Question Answer
What is Alveolar Dead Space? Ventilation w/o perfusion
What is the #1 dead space disease? Pulmonary Embolism (blood clot)
What is an Anatomic Shunt? Anatomic channel that bypasses the pulmonary capillary bed & empties venous blood into the L Atrium. (Ex: Thebesian, Broncial, Pulmonary, & Pleural veins)
What is a capillary shunt caused by? Atelectasis & Alveolar Fluid
Explain Anatomic Dead space Conducting airways. Ideal body weight x 1 = approx dead space.
Explain Alveolar Dead space Non-perfused alveoli – alveoli that aren’t receiving enough blood flow.
Explain Physiologic Dead space Anatomic + Alveolar dead space (Vd/Vt)
What is FVC? Forced Vital Capacity; maximum inhale followed by maximum exhale. Ideal Body Weight x 6 = FVC
What is the BOHR Equation? PaCO2 – PeCO2 / PaCO2 = Vd/Vt
What is the normal Vd/Vt range? .20 – .40
If the difference between PaCO2 & PeCO2 is greater than 20, then … Lots of dead space. (#1 cause is pulmonary emboli)
There is a direct correlation between respiratory rate & … Vd/Vt
Rapid, shallow breathing = Increase in Vd/Vt
What is the major muscle of inspiration? Diaphragm. (R & L hemidiaphragms)
What nerve innervates the diaphragm? Phrenic nerve
What are the accessory muscles of inspiration? Scalenes, sternocleidomastoid, pectoralis major, & trapezius
What are the accessory muscles of expiration? Rectus abdominus, transverse abdominus, external oblique, internal oblique, internal intercostals
What is IRV? Inspiratory Reserve Volume. Maximum breath in on top of tidal volume (Vt).
What is ERV? Expiratory Reserve Volume. Maximum breath out from bottom of tidal volume (Vt).
What is RV? Residual Volume. Gas remaining in lungs following a maximum expiratory effort.
What is TLC? Total Lung Capacity. Sum of all lung volumes.
What is VC? Vital Capacity. Vt + IRV + ERV. Maximum inspiration follwed by maximum expiration. 70ml/kg.
What is IC? Inspiratory Capacity. Vt + IRV
What is FRC? Functional Residual Capacity. RV + ERV. Volume of gas in the lungs following a passive expiration.
Low lung compliance diseases Pneumonia, Pulmonary Edema
Low thoracic compliance caused by: Kyphoscoliosis, Ascites, Gross Obesity
What is Specific Compliance? Used to compare adults & children
What is normal Specific Compliance? 0.080 L/cmH2O/L
What is Elastance? Opposite of Compliance = how easy air is pushed out.
What is normal Elastance? 5cmH2O/L
Low values of elastance indicate: Emphysema
Explain airway tethering The more alveoli in contact w/ other airways, the less likely they are to collapse.
What is surfactant? Dipalmityl Lecithin – a phospholipid that dramatically reduces alveolar surface tension; keeps alveoli from collapsing.
What is surfactant produced by? Type II pneumocytes
What is LaPlace’s Law? P=4ST/r (P=pressure, ST=surface tension, r=radius)
If surface tension goes up, then … Pressure goes up
If radius goes up, then … Pressure goes down
Surface Tension & Distending Pressure are … Directly proportional
If Surface Tension goes up, then Distending Pressure … Goes up
If Surface tension goes down, then Distending Pressure … Goes down
Small radius = ____ distending pressure Increase
Large radius = ____ distending pressure Decrease
General causes of Surfactant Deficiency Acidosis, hypoxia, hyperoxia(high FiO2), atelectasis, prematurity
Specific causes of Surfactant Deficiancy ARDS, IRDS, pulmonary edema, drowning, oxygen toxicity
A horizontal reflection on a compliance curve denotes … Low compliance; little V for lots of P.
A vertical reflection on a compliance curve denotes … High compliance; lots of V for little P.
A horizontal curve = Low lung compliance.
Causes of low lung compliance Pneumonia, pulmonary edema, pulmonary fibrosis(silicosis), atelectasis
A vertical curve = High lung compliance.
Too much lung compliance can cause … Emphysema(due to low elastance)
Never allow Peak to hit … 50
Never allow Plat to hit … 30 – or puppies die & Sarah McLachlan cries.
Normal Airway Resistance 1-2 cmH2O/L/sec
High value of Raw indicates: Asthma, Chronic Bronchitis
Raw equation: Peak – Plat / flow
C stat equation: Vt / Plat – Peep
C dyn equation: Vt / Peak – Peep
Es (Elastic static) equation: Plat – Peep / Vt
Ed (Elastic dynamic) equation: Peak – Peep / Vt
What is Conductance? Ease of flow – opposite of Raw.
Normal Conductance 0.5 – 1.5 L/sec/cmH2O
Low values of Conductance indicate: Asthma, Chronic Bronchitis
What is Resistance? Chest wall tissue resistance; impedance to motion caused by the thorax & abdomen.
Chest wall resistance is approximately __% of breathing in healthy adults. 20
What is airway resistance? Impedance to movement of gas through the airways
Airway resistance is approximately __% of breathing resistance in healthy adults. 80
What are some resistance factors? Bronchospasm, secretions, mucosal edema, low elastance, artificial airway(ET & Trach tubes)
WOB Calculation: Diameter x 16
Poiseuille’s Law Flow ~ P x r(to the 4th power) Addresses laminar flow, occurs in the small airways <2mm in diameter. WOB increases when Diameter decreases.
Reynold’s Number 2rvd / n. # >2000 establishes turbulent flow.
Indications for use of low density gases: Stridor, croup(post extubation), foreign body aspiration, upper airway masses
What is the purpose of low density gases? To decrease turbulence & WOB
Define Time Constants The time required for a lung unit to empty approx. 65% of a tidal volume of breath
Time Constant equation Kt = Cl x Raw
What is the normal Time Constant? .2 seconds
Long Time constant indicate: 2.0 sec = asthma, bronchitis; 4.0 sec = emphysema
Short Time constant indicate: 0.1 sec = Pneumonia, IRDS, ARDS, cardiogenic pulmonary edema
Short Time Constant = Short amount of time to empty O2 from the lungs
Long Time Constant = Long amount of time to empty O2 from the lungs
What is the Specific Compliance equation? Cl / FRC. (Lung Compliance / Functional Residual Capacity)