Question Answer
pH 7.35-7.45 A-B
PaCO2 35-45 B-A
HCO3 22-26 A-B
Causes of Respiratory Acidosis Build up of CO2 in blood (not enough BPM), hypoventilation, increased dead space
Correct Respiratory Acidosis increase # of BPM, increase size of breaths, and decrease dead space
Causes of Respiratory alkalosis Must have low amount of CO2 in blood, hyperventilation, pain, anxiety
To correct respiratory alkalosis decrease # of BPM, medication for pain, and treat anxiety
Causes of metabolic acidosis low amount of HCO3 in blood, diarrhea, aspirin toxitiy, diabetes, renal failure
To correct metabolic acidosis stop/correct whatever is causing, medication for diarrhea, treat renal failure
Causes of metabolic alkalosis increase in HCO3 in blood, vomitting, NG suctioning, ingestion of NaHCO3
To correct metabolic alkalosis stop/correct vomitting, discontinue NG suction, stop NaHCO3
Oxygenation PaO2, measured only of oxygen dissolved in plasma. subtract 1 mmHg for each year over 60 to get normal for senior citizen
Correct hypoxemia oxygen level is normal, if it took supplemental oxygen to get it there
uncorrected hypoxemia if pt is on supplemental oxygen and their PaO2 is NOT within normal limits
Normal oxygenation 95-97%
SaO2 determined by PaO2, body temp, and pH
SaO2 amount of oxygen attached to and carried by hemoglobin
Question Answer
What is the first step before doing a ABG? check the chart to comfirm order and indication
After a major change in ventilatory support how long it should be waited to do a ABG? 20-30 minutes
What is the preferred site for adults ABG’s drawn? Radial artery
What is the longest time a ABG sample could go( without ice)without being analyzed? 15 minutes
PH lower than 7.35 acidemia
PH higher than 7.45 Alkalemia
What test is perform to comfirm collateral circulation before doing ABG? Allen Test
What is a adequate amount of blood for a ABG sample? 2-4 ml of blood
Normal PaCO2 35-45 mmhg
Normal PH 7.35-7.45
Normal HCO3- 22-26 meq/l
Interpret the following ABG: PH 7.40 PaCO2 40 HCO3- 24 normal
Interpret the following ABG: PH 7.25, PaCO2 60, HCO3 26 Respiratory Acidosis
Interpret the following ABG: PH 7.50 PCO2 44 HCO3- 35 Metabolic alkalosis
Interpret the following ABG: PH 7.25 PCO2 36 HCO3- 13 Metabolic Acidosis
Interpret the following ABG: PH 7.60 PCO2 22 HCO3- 24 Respiratory Alkalosis
Some causes of metabolic acidosis? diarrhea, starvation, diabetic ketoacidosis
When results of ABG the PH and the PCO2 are going in the opposite direction there is always? Respiratory component
Interpret the following ABG: PH 7.50 PACO2 27 HCO3- 24 Respiratory alkalosis

Interpret the following ABG: PH 7.38 PCO2 62 HCO3 24

Respiratory acidosis

Question Answer
Indications that you should perform an ABG: To evaluate PaCO2,Acid-Base and 1.)PaCO2,Oxygenation,Total Hb and dyshemoglobins(abnormal hemoglobins) 2.)Response to therapy 3.)Monitoring the severity and progression of a disease process.
What is the Sanz? pH
What is the Clark Electrode? PO2
What is the Severinghaus PCO2
Steps to calibration of PO2 electrode: 1
Question Answer
Primary purpose of obtaining ABG samples 1. adequacy of oxygenation 2. adequacy of ventilation 3. reflects lung formation
3 major hazards of arterial puncture 1. bleeding 2. obstruction of vessel. 3. infection
3 major criteria for selection of arterial puncture site 1. collateral blood flow 2. vessel accessibitly 3. peripheral structures
Collateral blood flow If it’s part of a colatoral circulation system it can prevent loss of distal blood flow in the event of arterial obstruction
Vessel accessbility the best vessel for puncture is one that is easy to palpate, relatively superficial and somewhat stable
Peripheral structures the best site for arterial punctures are those whcih do not have extremely sensitive adjacent structures such as nerves
The order of preference that sites usually utilize for arterial puncture radial, bronchial, femoral
Allen test elevate hand and make fist for 20 secs, firm pressure held against radial and ulnar arteries, pt opens hand should blanch white, examiner releases only ulnar compression
alternative methods of assessing for collateral circulation doppler ultrasound, and pulse oximetry
Correct procedure for obtaining ABG hold syringe @45 for radial, tell pt “going to feel stick”, enter needle quickly, withdraw 1-2 ml, press gauze on site for 3-5 min, check for bubbles, seal syringe while holding site pressure (roll syringe)
Appropriate action to preserve the sample awaiting analyzation put syringe in ice
What should be written on lab slip date, time, pt name, O2 %, temp if abnormal, your initials
Factors that would necessitate holding pressure greater than 5 minutes from arterial puncture pt using anticoagulants, and low platelet counts
Question Answer
What would you look at if you wanted to determine the oxygenation status of a patient? Pao2
An increase in CO2 cause the PH levels to become? Acidic
An increase in HCO3 is Alkalotic
Patient comes in with a PH of 7.52 a PaCo2 of 25 a HCO3 of 25 and a BE +1. What would be your interpretation of this blood gas? Respiratory Alkalosis
patient has a PH of 7.10 Co2 of 20 HCO3 of 10 and BE of -20 what is your interpretation of this blood gas? Metabolic Acidosis
What do you look at in a blood gas to determine ventilation? PaCo2
What is the normal range for B.E.? -2-(+2)
What is the normal HCO3 value? 24
You would add ____ or _____ to improve oxygenation? O2 or PEEP
True or False: A blood gas would be considered normal if the BE was NOT within the normal limits False. Everything must be within normal limits for the blood gas to be considered normal
You get a blood gas and the values are PH 7.28 CO2 is 48 HCO3 is 32 and BE is +10 what would you assess the problem to be? ( include whether is is fully compensated or partially). Partially Compensated Respiratory Acidosis
You get a PH and the ABG reads PH is 7.44 CO2 is 26 HCO3 is 23 and BE is -1 what would you assess the problem is? (include whether it is compensated or uncompensated) uncompensated respiratory alkalosis
If you get a gas and the PH is within normal range and CO2 and HCO3 are moving in the same direction then how would u first classify the gas? Fully compensated
If you get a ABG and it reads PH is 7.56 co2 is 42 HCO3 is 34 and BE is +5. Then how would you name this gas? Acute or uncompensated metabolic alkalosis
At what PH should we intubate the patient 7.2
Severe hypoxemia is is classified and PaO2 less than ___ mm Hg? 40
What is a normal range for PaO2 on room air? 80-100 mm Hg
If CO2 and HCO3 are moving in opposite directions then what first name would you give the gas? Acute or uncompensated
What is the range of moderate hypoxemia 40-59 mm Hg
You get an ABG and it reads: PH is 7.42 CO2 is 43 HCO3 is 25 and BE is +2. How would you classify this gas? Normal
If PH decreases below 7.35 then it is? Acidic
A PH above 7.45 is? Alkalotic
True or false: the FIO2 a patient is on is also shows up when reading a ABG True
If you are hypoventilating the your CO2 will increase
If you were hyperventilating then your CO2 would? decrease
Term Definition
pH<7.35 and PaCO2 > 45 HCO3 Normal RESPIRATORY ACIDOSIS chronic obstruction lung disease
Chronic Obstruction lung disease emphysema, chronic bronchitis, severed asthma, ARDS, Guillian-Barre syndrome, anesthesia and pneumonia
pH<7.35 and HCO3 <22 METABOLIC ACIDOSIS DKA, severe diarrhea, starvation/malnutrition, kidney failure, burns, shock and acute MI
drugs that cause a low pH narcotics, barbiturates, acetazolamide (Diamox), ammonium chloride and paraldehyde
pH> 7.45 and PaCO2<35 RESPIRATORY ALKALOSIS salicylate toxicity (early phase), anxiety, hysteria, tetany, strenuous exercise (swimming, running) fever, hyperthyroidism, delirium tremens, pulmonary embolism, sepsis. If a mechanical vent patient (too much f or VT)
pH > 7.45 and HCO3 > 26 METABOLIC ALKALOSIS severe vomiting, gastric suction, peptic ulcer, potassium loss (hypokalemia), excess administration of sodium bicarbonate, cystic fibrosis, hepatic failure
drugs that cause an elevated pH sodium bicarbonate, sodium oxalate, potassium oxalate
Compensated Respiratory Acidosis pH Normal PaCO2 > 45 HCO3> 26 Leave mechanical vent patient alone. There are no changes to be made they are compensating
Metabolic Alkalosis pH alkalotic HCO3 alkalotic
Metabolic Acidosis pH is acidotic HCO3 acidotic
Compensated state pH is in normal range (7.35-7.45)
uncompensated pH outside normal range and CO2 or HCO3 is normal
Respiratory Alkalosis pH is alkalotic CO2 is alkalotic
Respiratory Acidosis pH is acidotic CO2 is acidotic
Partially compensated pH outside normal CO2 and HCO3 outside of normal
Question Answer
An increase in the H+ of the blood only to an increase in the arterial PcO2 Respiratory Acidosis
The primary goal of acid-base homeostasis is to maintain what? Normal pH
Potential causes of Respiratory Alkalosis Anxiety, Hypoxemia, Pain
which organ system maintains the normal level of HCO3- at 24 mEq/L? Renal
According to Henderson-Hasslebalch equation, the pH of the blood will be normal as long as the ratio of HCO3- to dissolved CO2 is? 20:1
What is the limiting factor for H+ excretion in the renal tubules? Insufficient buffers
What is the kidneys most important function? Sodium maintenance
Normal range for BE +2 mEq/L
What acts as the “first-line” or immediate defense against the accumulation of H+ ions? Blood buffer systems
A primary Respiratory problem is determined by? If the PaCO2 is less than 35mmHg or Greater than 45mmHg
H+ can be determined by the use of which factors? HCO3- and H2CO3
Which organ system actually excretes H+ from the body? Kidneys
A primary Metabolic problem is when? HCO3- is less than 33mEq/L or greater than 26mEq/L
A patient has a pH of 7.49, what would this define? Alkalosis
Normal pH range? 7.35 to 7.45
Common sites for trancutaneous blood gas electrode chest, abdomen, and lower back
What affect does hyperventilation have on the closed buffer systems? Causes them to release more H+
What is Buffer solution? A solution that resists large changes in pH upon addition of an acid or a base.
PaO2 below what value is considered severe hypoxemia? 40mmHg
What mechanisms help to eliminate excess H+ via kidneys? Reabsorbtion of HCO3-, Phosphate buffering, Ammonia buffering
For continuous monitoring of adults and children, you should set a pulse oximeter’s low alarm in what range? 88% to 92%
Compensation for Respiratory Alkalosis occurs through? Renal excretion of HCO3-
What chart information should be checked before performing artery puncture? Patients primary diagnosis and history, presence of bleeding disorders or blood-borne infections, anti-couagulant or thrombolytic drug prescriptions, respiratory care orders.
What is a normal response of the body to a failure in one component of the acid-base regulatory mechanism compensation
When a strong acid is added to the bicarbonate buffer system, what is the result? weak acid neutral salt
Primary metabolic alkalosis is associated with which of the following? Gain of buffer base
The majority of the acid the body produces in a day is excreted through the lungs as CO2, what happens to the H+ ions? They bind to an OH- forming H2O
Sites used for Arterial Blood sampling by percutaneous needle puncture femoral, radial, brachial
Before a sample of capillary blood is taken, what should you do to the site? warm to 42degrees Celsius and clean with an antiseptic solution
A mechanically ventilated patient exhibits a sudden decrease in end-tidal CO2 levels. What are possible causes of this change? massive pulmonary embolism, disconnection of the ventilator, sudden drop in cardiac output
Indications for pulse oximetry include to assess changes in HbO2 during certain procedures, to comply with external regulations or recommendations, to monitor the adequacy of HbO2 saturation
Factors to determine the volume needed for an arterial blood sample include? ABG analyzer’s requirements, specific anticoagulant used, other tests that will be done
After obtaining an arterial blood sample, what should you do? Apply pressure to the site until bleeding stops, place sample in a transport container with ice slush, mix the sample by rolling and inverting the syringe
Transcutaneous blood gas monitoring is indicated when what need exists? To continuously analyze gas exchange in infants and children, to quantify the real-time responses to bedside interventions, to continuously monitor for hyperoxia in newborn infants
What is the appropriate interval for changing the site for a transcutaneous blood gas monitor sensor? 2 to 6 hours
What should be monitored during the sampling of arterial blood? Presence of pulsatile blood return and presence of air bubbles or clots in the sample.
what is a normal end-tidal PETCO2 range? 35-43 mmHg
What size needle would you recommend to obtain an ABG sample on an infant? 25 gauge
Indications for arterial blood sampling by percutaneous needle puncture include? monitor the severity of a disease process, evaluate ventilation and acid base status, evaluate a patient’s response to therapy
What is the normal range for end tidal CO2 as measured by capnography? 5% to 6%
After obtaining an arteral blood sample from an Arterial Line, you would? Flush the line and stopcock with heparinized intravenous solution, confirm stopcock port open to intravenous bag solution and catheter, confirm undamped pulse pressure waveform on monitor
Some causes of Metabolic Acidosis with an increase of anion gap include? Ketoacidosis, Lactic Acidosis, Renal Failure
Patient parameters that should be assessed as part of Arterial Blood Sampling include? Temperature, Position and Activity level, Clinical appearance
What factor would limit the ability of the H2CO3/ HCO3_ buffer system to perform efficiently? Lungs failing to excrete adequate levels of CO2
Clinical signs of Acute Respiratory Alkalosis include? Convulsions, dizziness, parathesia
Normally the following occur when the kidneys eliminate H+ Sodium ions and water are reabsorbed, HCO3- is reabsorbed in proportion to the H+ excreted, Bicarbonate bugger capacity is restored
Range of HCO3- 22-26 mEq/L
Range of PaO2 80- 100 mmHg
Range of PaCO2 35-45 mmHg
Range of SaO2 93% to 100%
pH below 7.35 Acidosis
pH above 7.45 Alkalosis
In acute respiratory acidosis what would you expect the BE range to be? +2 to -2 mEq/L
What is the role of Carbonic anhydrase in the kidneys? It drives the recovery of HCO3- and excretion of H+
Low PaCO2 best describes which of the following? Respiratory Alkalosis
With partially compensated respiratory alkalosis, which of the following blood gas abnormalities would you expect to encounter? decrease HCO3-, Decreased PCO2, Increase pH
Causes of Respiratory Acidosis in patients with normal lungs include Neuromusclar disorder, spinal cord trauma, Anesthesia, central nervous system depression
what is buffer base? The sum of all blood buffers in 1L of blood
Before connecting the sample syringe to an adult arterial line stopcock, what should you do? Aspirate at least 5mL of fluid or blood using a wasted syringe
Why is the bicarbonate buffer system considered an open buffer system Its acid (cardonic acid) is converted to Co2 and removed
Equipment for capillary blood sampling lancet, capillary tubes, warming pad
When is capillary blood gas sampling indicated? ABG analysis is needed but Arterial access is not availble
Primary chemical event in Metabolic Alkalosis Increase in blood HCO3-
Compensation for metabolic acidosis occurs through? Decrease in blood CO2 levels
Causes of Metabolic Alkalosis Diuretics, Hypochloremia, Vomitting
Example of an Iatrogenic cause of Metabolic Alkalosis Gastric suction
Clinical findings that you would expect in a fully compensated Respiratory Acidosis patient? elevated HCO3- and pH between 7.35 and 7.39
Question Answer
Define Quality Assurance Total quality of reported results
Define Quality Control Maintenance and validation of the measuring system
What is the normal accepted limits of variation for routine quality control measures? +/-2 standard deviations (95%) from the mean
Define a random error (what is it also referred to as?) An isolated result outside of the control limits and has minor significance. Also referred to as a dispersion.
Define trending (systemic error) Progressive controls increase or decrease
Define shifting (systemic error) Abrupt change in measurement followed by clustering
Question Answer
What is the normal pH range? 7.35-7.45
What is the normal range for PaCO2? 35-45mmHg
What is the normal range for HCO3? 22-26mEq/L
What is the normal range for base excess? -2-2.0mEq/L
What type of issue(s) are we looking for when we look at the HCO3 and base excess value(s)? Metabolic issues
What type of issue(s) are we looking for when we look at the PaCO2 value(s)? Ventilation status
What does the PaO2 measure? Oxygenation status
What are the hypoxemia ranges? >60mmHg (mild hypoxemia) 40-59mmHg (moderate hypoxemia) <40mmHg (severe hypoxemia)
What range of PaO2 is considered normal on room air? 80-100mmHg
What ABG value would we look for in patients that currently smoke or have smoked heavily in the past? %MetHb
What ABG value would we look for in patients that have carbon monoxide poisoning or have been in a fire? %COHb
Below what pH value is considered to be acidic? <7.35
Above what pH value is considered to be alkalotic? >7.45
Three anatomical sites for an ABG: 1)radial artery 2)femoral artery 3)dorsalis pedis
In a given ABG, if the pH and CO2 are going in DIFFERENT directions, what is this ABG considered to be? Respiratory
In a given ABG, if the pH and HCO3 are going in the SAME direction, what is this ABG considered to be? Metabolic
When interpreting a given ABG, what values must be abnormal for it to be considered “partial”? All values must be abnormal. (pH, CO2, and HCO3)
When interpreting a given ABG, what values must be normal for it to be considered “uncompensated”? Either the CO2 or HCO3
When interpreting a given ABG, what value must be normal for it to be considered “compensated”? The pH must be normal
How can tissue O2 be measured By invasive probes-Tissue Oxygen (Pt)2) monitor, inserted directly into organs, tissue, and body fluids.
How do you prevent pre-anlytical errors in ABG samples? Make sure the sample is: Obtained anaerobically, properly anticoagulated, bubbles removed, analyzed within 10 to 30 minutes
How is CO2 transported? 45-55 ml of CO2 per 1 dl blood is transported by ionized bicarb, dissolved in plasma, and plasma protein transport.
How much blood is needed for an adequate ABG sample? 0.5 mL of blood. Usually enough to perform two tests.
For accurate ABG results what are the components of quality control? Record Keeping Performance validation Preventative maintenance and function checks Automated Calibration/Verification Internal Statistical quality control External quality control (proficiency testing Remedial action
Intra-arterial (In Vivo) continuous blood gas analysis is beneficial how? Real time monitoring Reduction in therapeutic decision making time Less blood loss Lower infection risk Improved accuracy Elimination of specimen transpor
Invasive procedures are Insertion of a monitoring device into a patient
Laboratory Analysis is discrete measurements of fluids or tissue that has been removed from the patient
Monitoring is defined as An ongoing process by which clinicians obtain and evaluate dynamic physiological processes in a timely manner (bedside)
Noninvasive procedures are external monitoring without insertion of devices INTO the patient
Possible anatomical sites for ABG’s Radial Brachial Femoral Posterior Tibial Dorsalis Pedis
Pressure values for osygenation PaO2 80-100 mmHg normal 60-80 mmHg mildly hypoxemic 40-59 mmHg moderately hypoxemic < 40 mmHg severely hypoxemic SaO2 95-100% Normal CaO2 18-20 % Normal
Procedure for initiating indwelling catheterization First sample of indwelling catherter would be a waste sample
Reasons for drawing an ABG Sudden, unexplained dyspnea Acute shortness of breath/tachypnea Abnormal breath sounds Cyanosis Heavy sue of accessory muscles Changes in ventilator settings CPR Diffuse infiltrates in Chest Xray Sudden Cardiac arrhythmias Acute hypotension
What are common technical errors associated with capillary blood samplig? Inadequate warming and squeezing of punture site. Squeezing the puncture site may result in venous and lymphatic contamination of the sample
What are secondary values to ABGs that need to be CALCULATED? Bicarbonate (HCO3) Base Excess (BE) or deficit Hemoglobin saturation (HbO2)
What are the 2 most important factors influencing accuracy of transcutaneous measurements? Age and perfusion status
What are the benefits of indwelling catheters? (ie. A-Line) Provides ready access for blood sampling Allows for continuous monitoring of vascular pressures.
What are two site locations for indwelling catheters? Normal routes are preipheral arteries (radial, brachial, pedal), femoral artery, central vein, and pulmonary artery.
What are two techniques of capnometry? Mainstream technique places an analysis chamber in patients breathing circuit. Sidestream technique pumps small volume of gas from circut into nearby analyzer.
What an a good capillary blood gas sample provide and reflect? Estimated arterial oxygenation and PCO2
What can be used if frequent blood sampling is needed? Arterial Cannulation
What can PtO2 monitors indicate? Monitor brain tissue oxygen as an early sign of ischemia. Monitor adequacy of brain perfusion in patients with traumatic brain injury.
What do most bedside systems to measure FiO2 utilize? Electrochemical principles (O2 analyzers)
What does Extra-arterial (Ex Vivo) blood gas analysis provide? Eliminates all problems associated indwelling sensors. Provides quick results Determine further justification of costs and patient benefits.
What does oximetery measure? Hb saturation using spectrophotometry.
What does transcutaneous monitoring provide? Continuous, noninvasive estimates of PO2 and PCO2 using a skin sensor. Also PtcO2 levels.
What is the downfall of indwelling catheters? Infection and thrombosis are more likely than intermittent punctures.
What is Hb measurements expressed as and what is its O2 capacity when compared to what is dissolved in plasma Always expressed in grams/dl. dl=100 ml. The O2 capacity of Hb is 7x greater than what is dissolved in plasma.
What is hemoximetry? Laboratory analytical procedure requiring invasive sampling of arterial blood
Question Answer
What is the normal pH range? 7.35-7.45
What determines the ventilation status of a patient? PaCO2
what is the normal range for HCO3? 22-26
what is the rule of thumb? the PaCO2 should be about 5 times the FIO2
When does the pH become acidosis or alkalosis anything below 7.35 is acid and anything above 7.45 is alkalosis
true of false does oxygenation decrease with age? true
what is the normal PaCO2? 35-45
the normal range for PaO2? 80-100
what are the different ranges for hypoxemia? >60mm hg is mild hypoxemia 40-59mm hg is moderate hypoxemia <40mm hg is serve hypoxemia
uncompensated C02 and HCO3 is NOT going in the same directions
compensated pH is normal and CO2 and HCO3 are going in the same direction
partially compenstated pH is out of range and CO2 AND HCO3 are going to the same direction.
what is the normal number for COHB? <3.0%
what does the COHB indicate? if the patient was exposed to carbon monoxide or a house fire.
what is the normal number for MetHb? <2.0%
what does the MetHb indicate? if the patient is a smoker
what is a metabolic issue? HCO3 and BE
what is a respiratory issue? CO2
what is the oxygenation status? PaO2
how to fix oxygenation? increase FI02
what are the last names? acidosis, alkalosis, and normal
what are the first names? compensated,uncompensated, partially compensated
what are the middle names? respiratory, combined, metabolic
Term Definition
PAO2 Alveolar oxygen tension
PcO2 Pulmonary capillary oxygen tension
PaO2 Arterial oxygen tension 75-100 mg
PvO2 mixed venous oxygen tension
PACO2 alveolar carbon dioxide tension
PcCO2 pulmonary capillary carbon dioxide tension
SaO2 Arterial oxygen saturation
SvO2 mixed venous oxygen saturation
pH Range 7.35-7.45; normal 7.40 <7.35 acidosis >7.45 alkalosis
HCO3 plasma bicarbonate concentration range 22-26 mEq/L(some books 24-28) ; normal 24 <22 acidosis >26 alkalosis
PaCO2 range 35-45 mmHg; normal 40 >45 acidosis <35alkalosis
mEq/L # of grams of solute contained in 1mL of a normal solution
CaO2 oxygen content of arterial blood = (Hbgx1.34xSaO2)+(PaO2x0.003)
CcO2 oxygen content of capillary blood
CvO2 oxygen content of mixed venous blood
V/Q ventilation/ perfusion ratio
QS/QT shunt fraction =(PAO2-CaO2)/PAO2-CvO2)
BE: +2 to -2 mEq/L
pH< 7.35 and PaCO2>45 indicates respiratory acidosis
pH>7.45 and PaCO2<35 indicates respiratory alkalosis
pH<7.35 and HCO3 <22 indicates metabolic acidosis
pH>7.45 and HCO3 >26 indicates metabolic alkalosis
Question Answer
Why do we analyze ABGs? ABG analysis gives important information to assist in the clinical management of patients with respiratory and metabolic problems
low HCO3 Kidney Disease
High PaCO2 COPD
Low PaO2 ARDS
From where do we draw? Radial Artery – most common site at which we draw ABGs
Why from radial artery Collateral circulation Allen’s test
pH represents a measurement of the overall acid-base balance and is used to assess the overall [H+] status of the blood
PaCO2 represents the arterial CO2 level and is used to assess ventilatory status
PaO2 represents the O2 tension level in the arterial blood and is used to evaluate the oxygenation status
HCO3 Represents bicarbonate level, an important buffer in the blood, and is used to evaluate the metabolic aspect of acid-base balance
BE/BD Represents the base excess (or deficit) level of the blood, and is used to indicate the metabolic aspect of acid-base balance
SaO2 Represents the level of saturation of hemoglobin (Hb) with O2 and also provides a measure of arterial oxygenation
7.35 – 7.45 pH
35 – 45mmHg PaCO2
80 – 100mmHg PaO2
22-26meq/L HCO3-
+/-2meq/L BE/BD
acidic High levels of CO2, Low pH (High H+ concentration, Low levels of HCO3
alkalotic Low levels of CO2, High pH (Low H+ concentration), High levels of HCO3
pH and PaCO2 are inversely related
pH and HCO3 are directly related
What is COMPENSATION? The altering of function of the respiratory or renal (metabolic) system in an attempt to correct for an acid-base disorder.
Hypoxemia low levels of oxygen in the blood
60-80mmHg mild hypoxemia
40-60mmHg moderate hypoxemia
<40mmHg severe hypoxemia
pH < 7.35 acidic
pH >7.45 alkalotic
PaCO2 < 35mmHg alkalotic
PaCO2 > 45mmHg acidic
HCO3 < 22meq/L acidic
HCO3 > 26meq/L alkalotic
Relationship between Minute Ventilation and ABG interpretation As Minute Ventilation increases, PaCO2 will decrease and pH will increase (Alkalosis) As Minute Ventilation decreases, PaCO2 will increase and pH will decrease (Acidosis)
Question Answer
What is analysis? Discrete measurements of fluids or tissue that must be removed from the body.
What is monitoring? An ongoing process by which clinicians obtain and evaluate dynamic physiological processess in a timely manner, usually at the bedside.
What is a monitor? A device that provides the important data to the clinician in real time, usually without removal of samples from the body.
What is a pulse oximeter? An inexpensive and portable, noninvasive monitoring device that provides estimates of arterial blood oxyhemoglobin saturation levels.
Spectophotometry detects oxygen saturation
What is spectophotometry? Measurement of color in a solution by determining the amount of light absorbed in the ultraviolet, infrared, or visible spectrum, widely used in clinical chemistry to calculate the concentration of substances in a solution.
According to the principles of spectophotometry… Every substance has a unique pattern of light absorption, much like a fingerprint. A substances pattern of light absorption varies predictably with the amount present.
Plethysmography detects heart rate
What is plethysmography? use of light waves to detect changes in the volume of an organ or tissue; pulse oximeters use the principle of photoplethysmography to measure the arterial pulse.
A pulse oximeter consists of a sensor, processor, and display unit.
What are some causes that may cause a pulse oximeter to not read properly? Nail Polish Low Blood Pressure (low perfusion) Dopamine (vasoconstrictors) Hypothermia Motion artifact ethnicity
What is the #1 thing that causes a pulse ox not to work correctly? Motion artifact
Sa02 and Sp02 should be roughly equivalent
Sa02 comes from hemoximetry
sp02 comes from pulse oximetry
A pulse oximeter measures the oxygen saturation of the blood
What are the advantages of pulse oximetry? Non-invasive continuous can be used to spot check -self calibrating
Pulse oximetry is based on 2 principles? spectophotometry plethysmography
THe pulse ox consists of 2 light beams and a photodetector (Red/Infrared)
The measurement sites with the pulse ox include. Fingers/Toes Ear Lobes Bridge of Nose Forehead
The Pulse oximeter should be left on for at least how many seconds? 20 seconds
What should you always chart when using pulse oximetry? The device and 02 liter flow. Date, time, position, Fi02, placement site, compare with ABG results.
What are the pulse oximetry indications? Monitor oxygen saturations (use value as a trend) Evaluate response to theraputic or diagnostic procedure. Comply with recomendations and regulations
What are the contraindications? Monitoring after a house fire. CO should be less than 1 in a normal person.
What are hazards/complications of pulse oximetry? False Values Pressure Sores Electrical Shocks/burns
What are the limitations of pulse oximetry? Motion artifact low perfusion states dysfunctional hgbs intravascular dyes lighting skin pigmentation nail polish/coverings
A pulse oximeter is within what accuracy of the hemoximitry value? +- 3-5 %
The lower the Sa02 value the less reliable the sp02 value will be
What are the qualifiers for home oxygen? A Pa02 of less than 44 mm Hg A sp02 of 87% during activity
Capnometry The measurement of C02 in respiratory gases.
Capnometer Device that measures C02
Capnography graphic display of c02 levels
dead space portion of inhaled air that does not take place in gas exchange.
Capnography is used primarily in the OR and Critical Care Unites
Capnography is used to assess ventilation
End exhalation has the highest level of c02
Capnography mesures carbond dioxed exhaled at the airwsay
PETCO2 End Tidal C02
What are the advantages of capnography? It’s non invasive Continuous Measures exhaled C02 and cuts down on ABG sticks
What is principal of capnography? Spectrophotometry (infrared absorption)
Method? Infrared absorption and a photodetector.
Sampling systems Mainstream/sidestream
Mainstream sampling systems are inserted directly in line with the ventilator circuit
Sidestream sampling systems are off to the side of the circuit
C02 absorbs infrared light
Because C02 absorbs infrared radiation, the greater the concentration of C02 in the sample the less infrared light that will arrive at the detector.
What are advantages of mainstream capnometers sensor at patient airway fast response (crisp waveform) No short lag time (real time reading) No sample flow to reduce tidal volume
What are disadvantages of mainstream capnometers? secretions and humidity can block sensor window. Sensor requires heating to prevent condesnation. Requires frequent calibration. Bulky sensor at patient airway Does not measure N2O Difficult to use with nonintubated patients.Cleaning
What are the advantages of sidestream capnometers? No bulky sensors or heaters at airway Ability to measure N20 Disposable sample line Ability to use with nonintubated patients
What are disadvantages of sidestream capnometers? Secretions block sample tubing trap required to remove water from the sample. Frequent calibration required Slow response to C02 changes Lag time between C02 changes and measurement. Sample flow may decrease tidal volume.
Sudden changes associated with Changes in High PETC02 sudden increase in Cardiac output sudden release of tourniquet. Injection of sodium bicarbonate.
What are gradual changes associated with High PETCo2? Hypoventilation Increase in C02 production.
What are sudden conditions associated with low PETC02 SUdden hyperventilation Sudden decrease in cardiac output Massive pulmonary embolism Air embolism Disconnection of the ventilator obstruction of the ET tube
What are gradual conditions associated with low PETCO2 Hyperventilation decrease in oxygen consumption decreased pulmonary perfusion
You should use capnography as a trend and corrolate with blood gas values
What are the indications of capnography? Monitor exhaled C02 (use value as a trend) Evaluate response to therapuetic or diagnostic procedure. Monitor severity of pulmonary disease. Determine tracheal intubation. Monitor ventilator circuit/artificial airway integrity.
Name more indications of capnography. Evaluate ventilator and patient interface. Monitor adequacy of blood flow. Monitor respiratory C02 when administered therapuetically.
What are the contraindications to capnography? None
What are the hazards of capnography? False values Positioning Weight Increased deadspace.
What are the limitations? Requires adequate response time. Moisture/Secretions Requires calibrations
If there is a leak you may have false values
The difference of PaC02 and PETC02 increase as dead space increases
Stae I of capnograph curve Expiratory pure deadspace
Stage II of capnograph curve mixture of deadspace/ventilatory CO2
Stage III of capnograph curve Pure C02 (end exhalation)
Stage IV of capnograph curve Inhalation of oxygen.
What are other methods of capnography? Calormetric C02 detector Mass spectometer Raman Spectroscopy.
A colormetric CO2 detector changes from purple to yellow if C02 is detected
In healthy adults PETCO2 is 1-5 mm HG less than PaC02
Transcutaneous monitoring is primarily used in neonates/small children
Transcutaneous monitoring is time intensive
Transcutaneous monitoring measures Pa02 and PaC02
The Ptc02 is measured with a clark electrode
The PtcC02 is measured with a Severinghause electrode
What are the advantages of transcutaneous monitoring? non-invasive continuous can monitor hyperoxygination
What is the principle of transcutaneous monitoring? Diffusion through skin surface Requires stabilization time.
Where are the measurement sites abdomen chest lower back
Transcutaneous monitoring provides estimates of PaC02 and Pa02 with sensor. Sensor is heated up to 42 degress celsius. this allows for diffusion.
What are the indications of transcutaneous monitoring? Monitor PaO2 and PaC02 (use value as a trend) Evaluate response to theraputic or diagnostic procedure.
What are the contraindications of transcutaneous monitoring? Poor skin integrity allergy to adhesive
If you have a leak the C02 will read 0
Transcutaneous monitoring must correlate with ABG initially
Transcutaneous monitoring doesn’t reflect oxygen delivery or content
What are the hazards/complications of transcutaneous monitoring? False values tissue/skin erythema blisters burns skin tears must change site every 2-6 hours
limitations of transcutaneous monitoring include prolonged stabilization required low perfusion states skin thickness improper electrode placement improper calibration labor intensive
What are ABG indications? To monitor ABG values. To evaluate response to therapeutic or diagnostic procedures. to monitor disease progression or severity.
What are the puncture sites? Radial artery (requires modified allens test) Brachial artery Femoral artery.
The femoral artery risky, huge veins and arteries, a fibrinolytic automatically rules out femoral sticks.
Radial artery Collateral circulation superficial and easy to palpate Is the number 1 artery for sticking Not near large veins. Relatively pain free
The brachial artery is risky, nerves and large veins. No collateral circulation. Increased risk for venous samle
Modified allens test Occlude radial/ulnar artery. Make fist, release fist, release ulnar artery. Should pick up within 10-15 seconds for + allens test.
What are the contraindications for ABG? negitive modified allen’s test avoid lesions or surgical shunts avoid infection of PVD Avoid femoral site on outpatients High dose anticoagulation
What are the hazards/complications? Thrombosis or air embolis Hemorrhage hamatoma arteriospasm loss of blood flow or circulation infection trauma vasovagal response pain sample contamination
There are preset and self filling syringes
Arterial blood gas supplies gloves/safety glasses 3 CC syringe/ 22-25 Guage needle anticoagulant-liquid sodium heparin crystalized lithium heparin. Needle cap/syringe plug local anesthetic (1%xylocaine/tuberculin syringe) Alcohol or betadine wipe gauze pad bandage cup of i
What do you chart on your blood gas? Date/Time, Patient Name and room number, Initials, site, Fi02, ventilator settings, temperature, 0xygen therapy device
Pre-analytical errors occur before the sample is inserted into the machine
Post-analytical errors happen while running the machine
Pre- analytical errors bubble contamination- for 21% fi02 pa02 will increase. For 100% fi02, pa02 will go down. Delay in sample- pa02 will decrease pac02 will increase. Anxiety paco2 will decrease pa02 will increase. venous sampling- lowers ph, increases pac02 and decrease p
What is one more pre-analytical error? Excessive heparin- makes the sample more acidic. You’ll see visable froth
What are some post-analytical errors? incorrect callibration error in sampling
Blood gas analyzers are calibrated at 37 degrees celsius
Pa02 changes7% for each degree celsius.
PaC02 changes 4% for each degree celsius
What are indications for an arterial line? continuous ABP monitoring Repeated ABGs
Where are insertion sites? radial brachial femoral
What are the component parts of the a-line? starter sheath pressure transducer high pressure tubing and pressure bag 3 way stop cock flush tape or sutures
The high pressure tubing and pressure bag prevents blood from coming out of the body
The pressure bag should be set at 300 mm HG or 50 mmHG above systolic ABP
What are requirements for sample? gloves and safety syringes 2 syringes (waste/ABG syringe) syringe plug gauze bad cup of ice label
What are the hazards and complications same as abg #1 complication is clotting infection is a complication
The CBG is an alternative to the abg procedure
The CBG gives a rough estimate of pH and pc02. P02 is of no value of est. oxygenation.
How is the procedure done? blood is collected in a heparinized glass capillary tube and the site must be warmed before procedure.
The site prep and handling of the CBG is the same as ABG sampling
Which population uses the CBG? Infants and small children
CBGs should be avoid in critical cases infants less than 24 hours old
The sites for the CBG include the heel of foot, fingertip and ear lobe
The ABG laboratory include the operator interface measuring chamber calibrating gas tanks reagent containers waste/disposable container transmittal system
The operator interface includes controls, keypad, software, screen display
Measuring Chamber incorporates a 3 electrode system (measures 02, PC02, PH)
PH has 2 electrodes (halfcells) Reference chamber and measuring chamber
Measured values PaC02 severinghaus electrodce pH: uses 2 electrodes or half cells Pa02: Clarck (polaropgraphic) electrode (galvonic fuel cell)
What are the derived values? Sa02, HC03, BE/BD you need co-oximetry to measure true Sa02
ABG analysis process? Verify order and follow procedure document procedure analyze sample follow lab documentation procedure
Quality assurance accreddidation JCAHO, College of American Pathologists
Purpose of quality assurance to prevent innaccuracies
Components of quality assurance record keeping, performance validation, preventative maintenance, automated calibration, calibration verification, remedial action, documentation
Question Answer
Normal value for pH 7.35-7.45
Normal value for PaCO2 35-45 mmHg
Normal value for PaO2 80-100 mmHg
Normal value for HCO3 22-26
Normal value for BE +-2
Normal value for SaO2 95-97% can be 100%
pH acidosis less than 7.35
pH alkalosis (base) more than 7.45
CO2 acidosis more than 45
CO2 alkalosis less than 35
HCO3 acidosis less than 22
HCO3 alkalosis more than 26
What is happening with respiratory acidosis increased CO2 in the lungs
What is happening with respiratory alkalosis decreased CO2 in the lungs
What happens with metabolic acidosis decreased HCO3 in kidneys
What happens with metabolic alkalosis increased HCO3 in kidneys
What hapens in combined acidosis increased CO2 in the lungs and decrease HCO3 in kidneys
What happens in combined alkalosis decreased CO2 in the lungs and increase HCO3 in kidneys
Uncompensated either the HCO3 or CO2 must be w/in normal limits or pH is not normal
compensated pH is w/in normal limits or Both PCO2 and HCO3 are outside their normal ranges
partially compensated pH is not normal and/or both PCO2 and HCO3 are outside their normal ranges
combined Three parameters are all either acid or all alkaline
Normal oxygenation 80-100
mild oxygenation (hypoxemia) 60-79
moderate oxygenation (hypoxemia) 40-59
severe oxygenation (hypoxemia) less than 40
hyperoxia more than 100
What do if you have resp acidosis increase ventilation (rate or depth of respiration)
What to do if you have resp alkalosis decrease ventilation (rate or depth of respiration)
What to do if you have metabolic acidosis stop diarrhea, treat kidney failure
What to do if you have metabolic alkalosis DC NG tube, stop vomiting
Question Answer
ABG samples provide what precise measurement of Acid-Base balance and lungs ability to oxygenate the blood and remove CO2
Accurate interpretation of ABG require what knowledge of pt total clinical picture including any TX receiving
where are mixed venous blood samples drawn rt atrium or pulm artery
what is mixed venous blood sample used for evaluate overall tissue oxygenation
why not venous samples only give metabolic rates so little value, exposed to peripheral vascular beds
normal ABG values for arterial blood is Ph 7.35-7.45, PaO2 80-100 mmHg, PaCO2 35-45 mmHg, HCO3 22-26, BE +-2
Normal ABG for mixed venous blood is Ph 7.34-7.37, PaO2 38-42 mmHg, PaCO2 44-46, HCO3 24-30
Prior to ABG draw, what should RT review for in Pt chart low platelet count or increased bleeding time (meds etc)
Preferred site of ABG arteriotomy (needle into artery) radial artery
Sites for ABG arteriotomy in adult are radial artery, brachial artery, dorsalis pedis, or femoral artery.
What must be evaluated prior to a radial stick collateral circulation of the hand, via modified Allens test
how is modified Allens test performed have pt make tight fist, RT compress both radial and ulnar artery, instruct pt to open hand and relax, RT release ulnar
what is a positive Allens test hand pinks w/in 10-15 seconds after release of ulnar artery, means circulation is adequate for puncture site
what should RT do if Allen test is negative try other arm then try brachial
what should RT do for pt who needs frequent ABG’s insert indwelling arterial catheter (only in ICU)
what do bubbles in sample do may equilibriate w/blood and cause bad sample-need to remove bubbles immediately after draw
How should RT handle sample after draw remove bubbles, store in ice water to stop metabolism, analyze with in 1 hr
room temp samples must be analyzed how soon 10-15 mins
how long should pressure be applied to stick wound 3-5 mins or longer if clotting problem
ABG and VGB samples are used to evaluate what acid-base balance (Ph, PaO2 PaCO2, HCO3 BE), oxygenation status (PaO2, SaO2, CaO2, PvO2), and adequate ventilation (PaCO2)
What does PaO2 reflect O2 in plasma of arterial blood, reflects ability of lungs to transfer O2 into blood
Predicted PaO2 is dependent on what pt age, FIO2, PIO2 (Pb and altitude)
effects of age on PaO2 103.5-(.42xage)+- 4, so if old fart like Jeff and age is 60 then 103-(.42×60) is 78.3 so normal range of PaO2 for Jeff is 74-82
hypoxemia PaO2 less than normal predicted range, at any age, for pt breathing room air or PaO2 <65mmhg, severe <40mmHg (any age) in pt with increased FIO2
Does hypoxemia exist if pt is on >FIO2 and his PaO2 is normal? NO, hypoxemia is only a <PaO2 lower than predicted regardless of FIO2
Hypoxia inadequate tissue oxygenation
how are hypoxemia and hypoxia related hypoxemia may result in hypoxia in pts with <CO, but they are not synonymous
most common cause of hypoxemia is >V/Q mismatch, in pts with lung disease
increased V/Q mismatch decrease in V/Q matching, perfusion is god, but ventilation is not, mucus plugging, secretions, bronchospasm, in specific portions of the lung
decreased V/Q matching is what (has been on last two Vent tests), an increase in V/Q mismatch
causes of hypoxemia >V/Q mismatch, diffusion defects, >CO2 from hypoventilation, Drug OD (>CO2), <PIO2 (altitude), equip failure
SaO2 norm >95%, O2 saturation, actual amount of O2 bound to Hb expressed as a %
how is SaO2 determined can be calculated, but true SaO2 must be can only be gotten from co-oximeter
Oxyhemoglobin disassociation curve shows the effects of O2 loading and unloading in relationship to Hb
Left shift in HbO2 disassociation curve >Ph, >SaO2, >Hb affinity, <temp, <CO2, <fetal Hb, <2,3 DPG, (increased affinity makes unloading at tissue more difficult)
Right shift in HbO2 disassociation curve <Ph, <SaO2, <Hb affinity, >temp, >CO2, >fetal Hb, >2,3 DPG, (decreased affinity makes unloading at tissue easier)
Ph and Hb affinity for O2 as Ph changes Hb affinity for O2 is directly affected (Bohr effect), Ph up, Hb affinity also up, Ph down Hb affinity also down
2,3 DPG organic phosphate in RBC, stabilizes deoxygenated Hb, reducing its affinity for O2, without it Hb would never unload O2 at the tissue
what >2,3DPG Alkalosis, chronic hypoxemia, anemia
what <2,3DPG acidosis
Shunt V/Q is equal to 0, perfusion with no ventilation, alveoli blocked, refractory to O2
decreased V/Q mismatch shunt effect, perfusion in excess of ventilation, non-refractory to O2, partial obstruction, hypoventilation, COPD, interstitial disease
Normal V/Q matching .8
increased V/Q matching ventilation in excess of perfusion, deadspace effect, regional hyperventilation, often seen in PPV and <CO
Deadspace ventilation no perfusion, increased PaO2 with a decreased CO2 (usually less than 40) emboli
CaO2 (Hb x 1.34)xSaO2+(PaO2x.003), norm 16-20 vol%, O2 bound to Hb and O2 in plasma, very important because of influence to tissue oxygenation
how is CaO2 measured can only truly accurate w/co-oximeter
decreased CaO2 anemia (normal PaO2 & SaO2 with <Hb), polycythemia (<PaCO2 & SaO2 w/normal CaO2), Hb bound by another gas (co-monoxide, metho)
P(A-a)O2 norm 10-15 mmHg on room air, or 25-65on 100%, predicted dependent on age and FIO2, increase is resp defect, every increase of 50 is 2% shunt above normal of 2-3%
Can A-aDo2 be calculated on nasal canulla? no, FIO2 must be known, never calc on low flow devices
A-aDO2 for old pt (age x 0.4), old fart like Jeff at age 70 x .4 equals 28 mmHg on room air
When might you see hypoxemia w/normal A-a diff hypoventilation or <PIO2
A-a DO2> 350 on 100% is what indication for mech ventilation w/refractory hypoxemia
PvO2 norm 38-42, mixed venous, must be drawn from pulmonary artery
Oxygen delivery is a function of what? CO and CO2
PaO2, SaO2 and CaO2 evaluate what respiratory component
how is tissue oxygenation assessed PvO2
decreased PvO2 <35 most often from impaired circulation, hypovelemia, PPV, LHF
normal or increase PVO2 in a very sick pt is usually caused by tissue hypoxia still exists, PVO2 is unreliable-mechanism is unknown
C(a-v)O2 norm 3.5-5 vol%, increased w/stable VO2 indicates perfusion to organs is decreasing
a-v diff >6vol% cardiovascular decompensasion and tissue oxygenation is inadequate
a-v diff <3.5 vol% perfusion exceeds normal (if steady VO2), if VO2 is down then hypothermia
HbCO norm .5%, carboxyHb, carbon monoxide poisoning, must use co-oximeter, 200-250 x greater affinity than O2 for Hb
increased HbCO causes what tissue hypoxia, inhibits unloading of O2 at tissue, >of 5-10% w/smokers, >40-60% causes visual disturbances, myocardial toxicity, LOC, eventual death
S&S of increased HbCO headache, dyspnea, nausea, tachycardia, tachypnea
what effect does HbCO have o PaO2 and SaO2 if co-oximeter is not used, both will be normal
significance of PAO2 + PaO2 (on room air) 110-130 is hypoxemia due to hypoventilation, <110 is hypoxemia due to lung defect, >130 is pt on >FIO2 or error
First sign of hypoxemia is short of breath especially on exertion
clinical manifestations of hypoxemia are tachycardia, tachypnea, hypertension, cyanosis, confusion
severe hypoxemia may result in tissue hypoxia, met acidosis, bradycardia, hypotension, coma
In ICU pt, how do we identify tissue hypoxia PvO2 <35 and a-v diff >5 vol%
lungs remove CO2 by ventilation
kidneys role in acid-base balance is what remove small quantities of acid, restore buffer capacity of fluids by replenishing HCO3
Ph hydrogen ion concentration in blood, reflects acid-base balance
bases solutions capable of accepting H+
PaCo2 respiratory component of acid-base balance, identifies degree of ventilation in relation to metabolic rate
hypercarbia mot often results from hypoventilation, CO2 >45
hypocarbia is usually caused by hyperventilation, CO2 <35
What is the most reliable measurement of pt ventilation CO2, and should be interpreted in light of a normal VE w/CO2 or >VE w/normal CO2
HCO3 bicarb, norm is 22-26 mEq/L, primary metabolic component of acid-base balance, regulated by renal system, usually requires 12-24 hrs for compensatory response
A decrease in CO2 (to the left in O2 curve) reduces HCO3 how much CO2 <5mmHg will <HCO3 by 1
An increase in CO2 (to the right) will increase HCO3 how much CO2 >10-15 will >HCO3 by 1
BE+- base excess base deficit, standard deviation of HCO3 that takes buffering of RBC’s into account. Calculated with Ph, CO2 and Hematocrit and is a more complete analysis of metabolic buffering capability
Base excess positive value indicates either base has been added or buffer removed, larger the number the more sever the metabolic component
what is the importance of BE allows analysis of pure metabolic components of acid-base balance, changes in met components alter acid-base, respiratory components do not
do changes in CO2 effect BE? NO, only metabolic changes alter BE
Simple respiratory acidosis is inadequate ventilation, elevated CO2
common causes of resp acidosis acute upper airway obstruction, severe diffuse airway obstruction (acute or chronic), massive pulm edema
Common non-respiratory problems that cause resp acidosis drug OD, spinal cord injury, neuromuscular diseases, head trauma, trauma to thoracic cage
How is acute resp acidosis compensated none, renal changes are to slow
How is chronic resp acidosis compensated kidneys increase absorption of HCO3
How is uncompensated resp acidosis identified Ph,CO2, with normal HCO3 and normal BE
What is partially compensated resp acidosis HCO3, but Ph is not yet w/in normal limits
what is fully/completely compensated resp acidosis? HCO3 enough to bring Ph within normal range
How is degree of compensating determined in resp acidosis acute-HCO31 for every 10-15 in CO2, chronic- HCO34 for every 10 CO2
If expected level of HCO3 compensation is not occurring for acute or chronic acidosis what should RT suspect? complicating metabolic disorder is also present
neuromuscular disease or obstructive disorder w/resp acidosis, pt will RR will be what short of breath and RR
Drug OD or impaired resp center pt w/ resp acidosis pt RR will be what reduced
what effect does acute elevation of CO2 and acidosis have on CNS anesthetic, confused, semi-conscious and eventually coma
in acute resp acidosis how high does CO2 get for Pt to reach coma around 70 mmHg
because CO2 causes systemic vasodilation, what cardiac manifestations should be expected? warm flush skin, bounding pulse, arrhythmias
because CO2 causes cerebral vasodilation, what might be expected ICP, retinal venous distension, papilledema, headache
when HCO3 levels are up, what happens to chloride levels if result of renal compensation, then chloride will be
resp Alkalosis abnormal condition in which there is an increase in ventilation relative to the rate of CO2
How does RT identify resp alkalosis in ABG PaCO2 below expected level indicating ventilation is exceeding the normal level, hyperventilation
what are the common causes of resp alkalosis hyperventilation caused by pain, hypoxemia (PaO2 55-60), acidosis, anxiety
how do the kidneys compensate for resp alkalosis excrete HCO3
What is the expected compensation for acute resp Alkalosis none, Ph, PaCO2, normal HCO3
What is the expected compensation for partially compensated resp Alkalosis Ph, HCO3
What is the expected compensation for fully compensated resp Alkalosis normal Ph, HCO3
Expected compensation is not present for HCO3 in resp alkalosis, what should RT suspect complicating metabolic disorder is also present
In resp alk what is the advantage of a PaCO2 an PAO2 and therefor less chance of hypoxemia being present, or if present it will be better than if CO2 is up.
Clinical S&S associated w/ resp alkalosis tachypnea, dizziness, sweaty, tingling in fingers and toes, muscle weakness and spasms
when does RT need to be cautious not to induce resp alkalosis? during IPPB and mech vent
simple met acidosis HCO3 or BE falls below normal, caused when buffers are not produce in enough quantity (high Gap), or when buffers are lost (normal Gap)
Anion Gap normal 11 (8-16 mEq/L), when fixed acids accumulate in the body, H+ reacts to HCO3 causing it to,leading to a  anion gap
Causes of met acidosis with high anion gap can be divided into two categories what are they metibolicy produced acid gains or ingestion of acids
High anion gap met acidosis from metabolicy acid gains lactic acidosis (hypoxia, sepsis), ketoacidosis (diabetes, starvation, lack of glucose), renal failure (retained sulfuric acid)
High anion gap metabolic acidosis from ingestion of acids salcylate poisoning (aspirin), methanol, ethylene glycol
normal anion gap metabolic acidosis (hyperchloremic acidosis) from loss of HCO3 is caused by diarrhea or pancreatic fistula
normal anion gap met acidosis from failure to reabsorb HCO3 is most often caused by renal failure
normal anion gab met acidosis from ingestion may be caused by ammonium chloride or IV nutrition
what signs may be present w/renal disease blood urea, nitrogen and creatinine, urine output
How does the body compensate for met acidosis CO2(hyperventilation)
If normal or PaCO2 is present w/met acidosis what should RT suspect resp defect is also present (combination resp/met acidosis)
What is the predicted compensation of PaCO2 for met acidosis PaCO2 eqs (1.5xHCO3)+8+-2, if PaCO2 is not at predicted level based on calc, resp abnormality is present
what is the most common and obvious sign of met acidosis Kussmaul’s breathing
what is Kussmaul’s respiration very rapid, very deep ventilation
S&S and Pt complaints w/severe met acidosis dyspnea, headache, nausea, vomiting followed by confusion and stupor. Vasoconstriction, pulm edema, arrhythmias (if severe enough)
simple met alkalosis above normal HCO3
most common causes of met alk hyperkelemia, hypochloremia, ng suction (acid), vomiting (acid), post hypercapnic disorder, diuretics, steroids or to much bicarb therapy
how does body compensate for met alkalosis hypoventilation to PaCO2
fully compensated met alk is identified by in PaCO2 enough to return Ph to normal (hypercarbia may be present and may appear as resp acidosis)
when should RT suspect a mixed acid base disorder normal or near normal Ph w/severe abnormal HCO3 or PaCO2
where should RT look for clues of mixed acid base disorders pt hx, physical exam, lab tests, knowing primary disorders, expected compensations
expected compensation for acute resp acidosis PaCO215-HCO3 1
expected compensation for chronic resp acidosis PaCO210-HCO34
expected compensation for acute resp alkalosis PaCO25-HCO3 1
expected compensation for chronic resp alkalosis PaCO210-HCO3 5
expected compensation for met acidosis PaCO2 eqs (1.5xHCO3)+8+-2 (shortcut is last two digits of Ph is equal to PaCO2) or HCO3 1-PaCO2.6
mixed/combined resp met acidosis PaCO2 HCO3
why is combined resp/met acidosis so easy to identify hypercapnia and low HCO3 work synergistically to significantly reduce Ph, often resulting in profound acidosis
common causes of resp/met acidosis are cardio pulm resuscitation, COPD and hypoxia, poisoning and drug OD
cardio pulm resuscitation and resp/met acidosis heart stops-blood circulation stops, apnea causes resp acidosis, and hypoxia causes lactic acidosis (metabolic)
COPD and hypoxia w/resp met acidosis chronic COPD w/compensated resp acidosis suddenly gets met disturbance like hypotension or renal failure, causing hypoxia and lactic acidosis
mixed/combined met resp alkalosis HCO3 w/below normal PaCO2-additive effects may result in severe alkalosis
When met alk is super imposed on resp alk, why does it become so severe when superimposed there is no compensation
what clinical situation will RT most likely see met/resp alkalosis hypoxemia, hypotension, neuro damage, to much mech vent, anxiety, pain, or any of above in combo
What pts most often get combined met resp alkalosis chronic COPD w/elevated HCO3, suddenly reduction in PaCo2 from mech vent will cause resp alk onto the met alk pt already has
Mixed met acidosis with resp alkalosis are difficult to recognize because either abnormality usually compensates for the other
met acidosis with Paco2 lower than predicted for degree of acidosis resp alk is also occurring simultaneously, Ph will be just above 7.4 (appearing to compensate for for resp alk)
what is the prognosis for met acidosis on resp alkalosis poor, most likely seen in critically ill
Question Answer
pH 7.35-7.45 <7.35 = Acid ; >7.45 = Alkaline (Base)
H+ The amount determines the pH. Acids = donate H+ : Bases = accept H+
PaCO2 35-45 mmHg >45 Respiratory Acidosis ; <35 Respiratory Alkalosis
PaO2 80-100 mmHg 60-79=Mild Hypoxemia ; 40-59=moderate ; <40=severe ; <27=death impending
SaO2 93-97% this value may indicate tissue hypoxia
HCO3- 22-26 mEq/L <22=metabolic acidosis ; >26=metabolic alkalosis
B.E. -2 to +2 mEq/L <-2 = metabolic acidosis ; >+2 = metabolic alkalosis
Question Answer
NORMAL PCO2 AND RAISED HCO3 IS AN INDICATOR OF WHAT? METABOLIC ALKALOSIS
What can cause acute respiratory acidemia? Drug overdose…Acute Bronchospasm …Trauma…Neuromuscular Diseases
What can cause chronic respiratory acidemia? The body has compensated…COPD…Pickwien Syndrome….Neuromuscular Disease
What causes respiratory Alkalemia? Hypoxemia…Pain/Fear/Anxiety…CNS Stimulation…Mechanically Induced
Name 3 parameters of the blood gas that are effected in metabolic acidemia? CHLORIDE…HCO3…PH
What internal organs come into play during compensation? KIDNEYS…LUNGS…
What is meant by compensation? When the compensatory response turns the pH to normal range
Describe metabolic Alkalemia. HCO3 > 26 meq/L & high pH
What are some physiologic causes of metabolic Alkalemia? Electrolyte Imbalance…N-G Suctioning…Vomiting…diarrhea…dieuretics
What are some physiologic causes of metabolic acidemia? Renal Failure…Aspirin Overdose…diarrhea…Ketoacidosis…Lactic Acidemia
An increase in Dead Space Ventilation occurs most often when: The perfusion of the lungs is reduced
What is the most reliable measurement for evaluating the effectiveness of ventilation? PaCO2
H+ & PH are ___________ related. Inversely
Name 3 types of Ketoacidosis. Diabetic…Starvation…Alcoholism
Name some details about Lactic Acidemia. Produced by anaerobic metab. …Hypoxemic..Poor circulation…Low HgB…excessive exercise…hypoxemic hypoxia (at higher elevations)
PaCO2 1.Acceptable range (35-45). 2.Determines if ventilations is adequate. 3.If PaCO2 >45 mmHg,then the pt. is not ventilating. 4.If pt. not on vent. and PaCO2 <35 torr, then it is not a serious problem.
Methods of supporting Ventilations 1. Mechanical Ventilations. 2. Manual resuscitation (bag). 3. Mouth to mouth resuscitation. 4. IPPB. 5.BIPAP. 6. Pressure support ventilation (PSV).
PO2 1.Acceptable range(80-100 torr). 2.It determines the adequacy of Oxygenation. 3.If PaO2 <80 torr, then pt. is not oxygenatiing. 4.If PaO2 >100 torr,then pt. is over-oxygenating n as w/all other drugs,O2 should be decreased.5.best indicator of o2transport
pH 1.Acceptable range(7.35-7.45). 2.Imp. to diagnose diabetics and indicates the need of sodium bicarbonate administration. 3. Interprets blood gases.
HCO3- 1.Acceptable range(22-26mEq/L). 2.Determines chronic vs. acute acidosis vs. alkalosis. 3.A low HCO3- is clear indicator for sodium bicarbonate indicator.
Hb (Hemoglobin) 1. Acceptable range(22-26). 2.Carries O2. 3.If Hb low then pt. is hypoxic regardless of PaO2 value and SaO2. 4. Hemorrhaging refers to the loss of blood and indicates supplement blood administration.
Question Answer
What does ABG’s determine? They are used to determine the oxygen level and managment of mechanical ventilation.
What is the normal pH range? 7.35-7.45mm Hg.
What is the normal range for PaCO2 35-45mm Hg.
What is the normal range for PaO2 80-100mm Hg.
What is the normal range for HCO3 22-26mEq/L
What does the pH measure? The pH measures the state of blood:acid or base.
What does the PaCO2 measure? The PaCO2 measures the partial pressure of carbon dioxide.
What does the PaO2 measure? The PaO2 measures the partial pressure of oxygen.
What does the HCO3 measure? The HCO3 measures the concentration of bicarbonate (metabolic issues).
What three ways do we classify the primary problem of ABG’s as? normal, acidosis, or alkalosis.
What two types do we classify as the primary cause of ABG’s as? respiratory or metabolic.
Which of the parameters is the respiratory component? PCO2
Which of the parameters is the metabolic component? HCO3
What happens to the pH when there is a increase in H+? The pH will decrease and become acidotic(<7.35).
What happens to the pH when there is a decrease in H+? The pH will increase and become alkalotic(>7.45).
Under what range of the pH will a patient have to be intubated? Anything less than 7.2
If the ph and PcO2 are going in opposite directions what does this indicate? A respiratory problem
If the ph and HCO3 are going in the same direction what does this indicate? A metabolic problem
What type of compensation is indicated when the pH, PCO2, and HCO3 are all out of range? partially compensated
What type of compensation is indicated when either the pH or PCO2 is out of range? uncompensated
What type of compensation is indicated when the pH is normal and the PCO2/HCO3 are out of range? fully compensated
pH-7.51, PaCO2-40, HCO3-31 uncompensated metabolic alkalosis
pH-7.30, PaCO2-59, HCO3-28 partially compensated respiratory acidosis
pH-7,62, PaCO2-47, HCO3-30 partially compensated metabolic alkilosis
pH-7.48, PaCO2-30, HCO3-23 uncompensated respiratory alkalosis
pH-7.36, PaCO2-30, HCO3-15, PaO2-80 fully compensated metabolic acidosis
What does the SaO2 meausure? The percentage of oxygen saturation of arterial blood.
Wat is the normal range for SaO2? 93-100
What is the normal range for base excess? -2.0 to 2.0
What is the normal range for CaO2? 16-22 mlO2/dl
What two things are used to determine the accurate percentage of the MetHb and the COHb? ABG and co-oximeter
What values are considered for a patient to be acidotic? pH<7.5 PaCO2>45 HCO3<22
What values are considered for a patient to be alkolotic? pH>7.45 PaCO2<35 HCO3>26
What is the most important value to examine when looking at ABG’s? oxygen
How is ventilation measured? PaCO2 levels
How is oxygenation measured? PaO2 levels
step 1 in interpreting ABG’s? classify primary problem
step 2 in interpreting ABG’s? classify primary cause
step 3 in interpreting ABG’s? classify compensation
Question Answer
What two electrochemical o2 analyzers are good for basic fio2 monitoring? clark electrode and galvanic cell
Where can blood gas samples be taken from? peripheral artery, indwelling catheter, capillary sampling
What is considered the gold standard of gas exchange analysis? ABGs
why is the radial artery the preferred site for arterial blood sampling? near the surface, easy to palpate and stabilize, ulnar artery gives good collateral circulation, not near any large veins, relatively pain free
what are the indications for ABGs? need to evaluate ventilation, acid base, oxygenation, status and oxygen carrying capacity of blood; need to assess the patient’s response to therapy and/or diagnostic tests; need to monitor severity and progression of a documented disease process
sampling of blood errors can be caused by: air in sample, venous admixture, excess anticoagulant, metabolic effects
The sample should be analyzed within 15 min
How long to do you need to give a critically ill or COPD patient to return to a steady state? 30 min
How long do you need to give a normal patient to return to steady state? 15 min
what are hazards and complications of ABGs? Bleeding, hematoma,Infection,air/blood embolism,Arterial spasm, occlusion, vessel damage.Ischemia distal to sample site,Necrosis distal to sample site
What are the contraindications of ABGs? Inadequate collateral circulation,Never sample from a lesion or surgical shunt,Femoral samples outside a hospital setting,Prolonged anticoagulation, inadequate clotting mechanism.
what are examples of noninvasive monitoring? pulse oximetry, capnometry, and transcutaneous measurements
what are pulse oximetry? measurement of blood hemoglobin saturations. measures the light absorbed and transmitted by a substance and scientists can identify presence and concentration
whjat does pulse oximetry use to measure? photoplethysmography
what two problems come with use of pulse oximetry? technological problems (motion artifact, reading dark skin or through nail polish) and clinical interpretation (forgetting oxy hb curve)
A false high reading on the pulse oximeter may be caused by Hbco, MetHb, dark skin tone, dark nail polish, ambient light
a false low reading on the pulse oximeter may be caused by methb, anemia, vascular dye, MRI, electrocautery
transcutaneous monitoring is best for what patients neonatal/pediatric patients
How do transcutaneous monitors work? the device arterializes the underlying blood by heating the skin. warming also inc the permeability of skin to o2 and co2. it provides continous, noninvasive estimates of arterial po2 and pco2 through surface skin sensor
what is capnometry? measurement of co2 in respiratory gases
how do co2 analyzers work? measure absorption of infrared light after co2 absorbs it
what are capnometers (co2 analyzers) good for? detecting v/q imbalance
what is capnometers best used for? steady states like anesthesia, best used when both ventilation and perfusion are present
How would you instruct a patient to perform an IC measurement? measured directly from a spirogram. the patient is asked to inhale maximally from the resting FRC at the end of a normal effortless exhalation.
How much does a patient need to inhale for an FVC maneuver? the patient should inhale rapidly and completely to TLC from the resting FRC level. then there should be a forced exhalation begins right after- all of FVC must be exhaled (6 secs worth)
How much of breath should be exhaled in first second? 80%
When looking at FVC curves, what is notable about obstructive diseases? they produce flattened slopes and smaller FEV1
in obstructive lung diseases, what are the only capacity figures that will go up? RV, VT, FRC, TLC
how does helium dilution work? Known volume and concentration of helium is introduced to the circuit. Patient breathes the gas mixture from ERV (start point) for about 2-5” until equilibration occurs.
How long may helium dilution take on obstructed patients? Severely obstructed may take 20” to equilibrate.
how does nitrogen washout work? Patient breathes 100% O2 for a period of time until exhaled N2 reaches 2.5%. Normally N2 is at 78%. Generally takes 2-5 minute to breath out all nitrogen, with the severely obstructed taking up to 20” or never completely “washing out”.
how does plethysmography work? Shutter valve opens and closes at specific intervals, allowing pressure and volume changes to be recorded. The patient “pants”. applies boyles law. thoracic gas volume is calculated
what is DLCO (Diffusing Capacity using Carbon Monoxide)? measurement of Transfer rate across the alveolar capillary membrane., works by breathing in CO
who will have erroneous results on DLCO tests? smokers or people who smoked that day
what is the normal value of DLCO? 40ml/min/mmHg
what does a DLCO value less than 40 indicate? indicative of restrictive processes such as: emphysema, fibrosis, or low lung volumes.
during a bronchodilator study, what happens? Spirometry is done then a BD is given.Spirometry is repeated. Look for changes in FEV1 of 15% and 200ml increase in volume. This is called reversibility.
what does reversibility of the airway obstruction indicate? effective therapy
what does bronchial provocation entail? Irritate the airway with exercise, cold air, or histamine. Looking for bronchospasm and obstruction in spiromerty.
a positive response to saline is defined as Decrease of 10% during FVC- means is hyper responsive airway.
a positive response to methacholine is defined as FVC repeated until a maximum drop of 20% in FEV1 is recorded.
normal amt of impairment is 80-120% obstruction
what is GOLD Stage I: Mild COPD FEV1/FVC < 70% FEV1  80%   predicted With or without   chronic symptoms   (cough, sputum   production)
what is GOLD moderate stage? COPD FEV1/FVC < 70% 30%  FEV1 < 80% predicted   (IIA: 50%  FEV1 < 80%   predicted)   (IIB: 30%  FEV1 < 50%   predicted) With or without chronic   symptoms (cough, sputum   production, dyspnea)III:
what is GOLD severe stage? COPD FEV1/FVC < 70% FEV1 < 30% predicted,   or the presence of respiratory   failure, or clinical signs of   right heart failure* Respiratory failure: PaO2 < 8.0 kPa (60 mm Hg) with or without PaCO2 > 6.7 kPa (50 mm Hg) while breathing air at sea level.
When do we get xrays for sure? Intubation Sudden change in patient condition-eg drop in saturation, change in level of dyspnea, chest pain, any sudden acute changes that are strange for that patient When we insert something like a central line or catheter
What monitoring devices do you want to use for a patient who just survived a house fire? ABG-to check for carbon monoxide-run blood through coaximter
Question Answer
What is the normal range for pH of an ABG? 7.35-7.45
What is the normal range of the PaCO2? 35-45mm Hg
What is the normal range for the SaO2? 93%-100%
What is the normal percent of MetHb in the body? <2.0%
What is the normal percent of COHb in the blood? <3.0%
What is the normal range of base excess on an ABG? +2-(-2)mEq/L
What is the normal range for HCO3? 22-26mEq/L
What is the normal range for CaO2? 16-22ml O2/dl
When is a person considered mildly hypoxic, moderately hypoxic and severely hypoxic based on their PaO2? Mild: 60-80mm Hg Moderate: 40-59mm Hg Severe: <40mm Hg
A good rule of thumb when deciding if a person is well oxygenated or not based off of their PaO2 is? 5 x FiO2
What are the four main values you look at while trying to name a disorder based off on an ABG? pH, PaCO2, HCO3 and Base Excess
How do you determine the last name? If the pH is 7.35-7.45 then it’s “normal”. If the pH is below 7.35 then it’s “acidosis”. If the pH is above 7.45 then it’s “alkalosis”.
How do you determine the middle name? If the pH and PaCO2 are going in opposite directions (like a seesaw) then it is “respiratory”. If the pH and HCO3 go in the same direction then it is considered “metabolic”. It can also be “combined” if all of the above happen at the same time.
How do you determine if the first name is “compensated/acute” or “uncompensated/chronic”? If CO2 and HCO3 are going in the same direction, the body is trying to compensate. Also, the pH must be within normal limits. If those two things DON’T go in the same direction then it is uncompensated.
How do you determine if the first name is “partially compensated”? If the pH is <7.35 or >7.45, it is considered partially compensated IF CO2 is and HCO3 are going in the same direction.
Is it necessary to put their oxygenation status after the full name of the disorder? YES
Question Answer
What is an ABG it’s oxygenated, draw from the artery-radial, bronchial, femoral….Helps differntiate oxygen defiencies from primary metabolic acid-base abnormalities
ABG cornerstone in the diagnosis and management of oxygenation (PaO2) and acid-base (pH and PaCO2) disturbances
PaO2 oxygen in arterial blood
Why do we need to know PaO2 to assess symptims of hypoxemia, determine parameters of oxygen, assess/titrate oxygen therapy, document need of oxygen reimbursment, and to assess/titrate ventilator parameters
Why need to know PaCO2 to assess/titrate ventilation, to assess symptoms of dyspnea, to determine deadspace ventilation
Why need to know pH & HO3 to asses acid/base balance, to categorize acid/base disturbances
Allen test test to the wrist checking for collateral blood flow through the ulnar
Normal results for allen test hand color flushes within 5-7 seconds
Alternative methods for checking for collateral blood flow doppler ultrasound, pulse oximeter
ABG contraindications negative allen test, no ABG through a lesion or distal to a surgical shunt (dialysis) and be caution with pt that take anticoagulants
Why choose radial artery? 1. near the surface and relatively easy to palpate and stabilize 2. collateral circulation, 3. artery is not near and large veins, 4. procedure is relatively pain free
What to label on the syringe date, time, pt name, O2 %, temp if abnormal, and your initials
Hazards of ABG infection, bleeding, and obstruction of the vessel
What to document in chart date, time, document puncture information, and verify sent to lab
What does blood gas analyzer directly measure pH (sanz electrode), PaCO2 (serveringhaus electrode), PaO2 (Clark electrode)
What does blood gas analyzer indirectly measure HCO3, O2 saturation (this is done by calculating from the directly measurements)
What does co-oximeter measure hemoglobin content and values related to hemoglobin binding: SaO2, % COHB , and % methemoglobin
What does the blood gas machine accuracy depend on 1.accurately measuring barometric pressure 2. properly calibrating machine-running measurements against known values 3. maintaining electrodes 4. running quality control procedures
Calculating Calibration (PB- PH2O) x fractional concentration of gas EX—- (760-47) x 10%CO2 = 71.3 mmHg