Question Answer
Normal V/Q ratios Normal = (4/5) = 0.8, ABG values are norm, 7.40, CO2 = 40, O2 = 100
High V/Q ratios = Deadspace = Responsive Hypoxemia High = (5/5) = 1.0, ABG pH = 7.45, CO2 = 30, O2 = 110(hypocapnic) because venous blood not in the mix so CO2 is not in ABG as much
Low V/Q ratio = Shunt = Refractory Hypoxemia Low = (3/5) = 0.6, ABG – pH=7.35, CO2 50(hypercapnic), O2 = 80
Deadspace disorders Pumlonary Emboli, Circulatory Shock = High V/Q
Shunt disorders Atelectasis, Pneumonia, Pumlonary Edema = Low V/Q
Fick’s Law Diffusion over alveolar Cap. Membrane, directoly proportional to SA, Pressure Gradient, and Diffusion coefficent, inversly proportional to thickness
Normal DLCO Diffusion capacity for CO(carbon monoxide), 25ml/min/mmHg
How to increase diffusion factors Recumbent position – Increases SA, exercise – increases ventilation, perfusion, and hemoglobin, Body size = height not wt.
How to decrease diffusion factors decrease SA – most dramatic in emphysema, Increase membrane thickness – in interstitial lung diseases like IIPF and pneumoconosis diseases
How is Oxygen transported in the blood Plasma, and hemoglobin
Hemoglobin A made p of 2 alpha and 2 beta polypeptide chains, with 4 HEME groups
p50 point of reference for loading or unloading of O2 onto hemoglobin, partial pressure required to saturate the Hb to 50% level
Normal p50 27mmHg
Decreased p50 less than 27 = left shift(LOAD), increased affinity between O2 and Hb, O2 loading easier in LUNGS, but harder in Tissues
Increased p50 greater than 27 = Right shift(RELEASE), dreased affinity between O2 and Hb, O2 loading harder in Lung, unloading easier in tissues
LEFT Shift Factors increased pH(ALKALEMIA), decreased CO2, Hypothermia, Decreased 2,3,DPG, promotes O@ loading
RIGHT Shift Factors Decreased pH(ACIDEMIA), increase CO2, hyperthermia(Fever), increase 2,3 DPG, promotes O2 unloading
BOHR effect CO2 and pH effect oxyHb disassociation curve, LEFT/LUNG/LOW CO2/ALKALEMIA…favors LOADING…RIGHT/TISSUES/HIGH CO2/ACIDEMIA…favors unloading
Methemoglobin (MHb)- Bad hemoglobin congential or chemically induced(Nitrates, NO, Caine drugs)alters HEME portion of Hb, cause DECREASED p50- O2 loads on Hb but will not unload in tissues, PulseOx reads 85%
Carboxyhemoglobin (HbCO) caused by CO poisoning or smoking, DECREASED p50- O2 loads on Hb but will not unload in tissues
Fetal Hemoglobin (HbF) in the fetus and neosaltered 2,3,DPG binding causes DECREASED p50, O2 load on Hb but not unload in tissues
Total Oxygen Delivery (DO2) – how much O2 going out DO2 = C.O. x (CaO2x10), normal is 5 x (20×10)= 1000ml/min, if given dl, multiply by 10
O2 consumption/uptake O2 consuption = C.O. x [C(a-v)O2x10], normal is 250ml/min
Factors that increase O2 consumption Exercise, Fever, Seizures, Shivering, all >250ml.min
Factors that decrease O2 consumption Peripheral shunting – bl not reaching tissues in limbs, Cyanide poison – block mitochondria from processing O2 properly, Hypothermia, metabolic rate goes down
C(a-v)O2 – (a-v) is diff between arterial and venous normal is 20-15 or 5ml/min
Factors that increase (a-v) gap Decreased CO, Increased O2 consumption, exercise, shivering, seizure, fever, tissues asking for more O2
Factors that decrease (a-v) gap Peripheral shunting, cyanide poisoning, hypothermia
Extraction Ratio O2ER O2ER = (CaO2-CvO2)/CaO2, normal = 25%, (20-15)/20
Increased ER Same as (a-v) gap, Decreased CO, Increase O2 consumption, failing heart, exercise, seizure, fever, shivering
Decreased ER Same as (a-v) gap, Increased CO, Decreased O2 consumption, peripheral shunting, cyanide poisoning, hypothermia
SVO2 = Venous saturation Normal 75%, PVO2 – 40-45, critical at 60%
Factors that increase SVO2 Ex. 80%, incresaed CO, decreased O2 consumption at tissues, Peripheral shunting, Cyanide poisoning, hypothermia
Factors that decrease SVO2 Ex. 60%, decreased CO, increased O2 consumption at tissues, exercise, seizures, shivering, fever
Calculate shunt (QS=shunted blood, QT=total blood flow)(CCO2=content O2 in pulm. Cap. Bed) QS/QT= (CCO2-CaO2)/(CCO2-CvO2)
Clinical significance of shunting <10=NORMAL, 10-20%=MILD, 20-30%=MODERATE, >30%=SEVERE
CO2 Transport 10% dissolved in Plasma, 20% in Carbamino on the protein portion, and 70% on Bicarbonate in the hemoglobin
Haldane Effect As SaO2 decreases, CO2 loading on Hb is enhanced(TISSUE LEVEL)…As SaO2 increases, CO2 unloading is enhanced (LUNG LEVEL)
Chloride Shift at TISSUE LEVEL Chloride IN, Bicarb OUT, CO2 LOADED, O2 UNLOADED(H+ increase)