1 - Perfusion & Ventilation Flashcards
What does the pulmonary variable P stand for?
Pressure
What does the pulmonary variable C stand for?
Content
What does the pulmonary variable V stand for?
Volume (gas)
What does the pulmonary variable F stand for?
Fractional concentration
What does the pulmonary variable Q stand for?
Volume (blood) (aka perfusion)
What does the pulmonary variable S stand for?
Saturation
What does the pulmonary variable A stand for?
Alveolar
What does the pulmonary variable I stand for?
Inspired
What does the pulmonary variable D stand for?
Dead space
What does the pulmonary variable E stand for?
Expired
What does the pulmonary variable T stand for?
Tidal
What does the pulmonary variable a stand for?
arterial
What does the pulmonary variable v stand for?
venous
What does the pulmonary variable c stand for?
capillary
What are the normal systolic and diastolic pressures in the pulmonary system? How do they compare to the systemic system?
Systolic = 25 mmHg (systemic = 120 mmHg)
Diastolic = 8 mmHg (systemic = 80 mmHg)
How does the pulmonary system function with pressures significantly lower than those of the systemic system?
Pulmonary system has much less resistance, so it requires a lower pressure and smaller pressure drop
Increased pulmonary arterial pressure [increases/decreases] resistance and [increases/decreases] blood flow.
Decreases resistance, increases blood flow (this is due to high compliance)
What is the equation for transmural pressure?
P(Tm) = P(iv) - P(A)
In regards to transmural pressure, high P(iv) and low P(A) [dilates/compresses] vessels and [increases/decreases] resistance.
dilates vessels, decreases resistance
In regards to transmural pressure, low P(iv) and high P(A) [dilates/compresses] vessels and [increases/decreases] resistance.
compresses vessels, increases resistance
Increased lung volume [dilates/compresses] alveolar vessels and [dilates/compresses] extra-alveolar vessels. How does this impact resistance?
compresses alveolar vessels (increased resistance), dilates extra-alveolar vessels (decreased resistance)
With a PAO2 of less than 60 mmHg, pulmonary vessels [dilate/constrict]. Why?
Constrict; this shunts the blood flow away from a poorly perfused alveolus.
What is the diagnosis criteria for pulmonary hypertension?
mean pulmonary pressure over 25 mmHg (normal 15 mmHg) at rest or 35 mmHg during exercise
At what pulmonary capillary pressure does pulmonary edema occur?
Pulmonary capillary pressure over 25 mmHg
What is the progression of pulmonary edema?
flooding of peri-capillary interstitial spaces –> crescentic filling of alveoli –> flooding of individual alveoli with loss of gas exchange
How do you calculate the partial pressure of oxygen in atmospheric (dry) air? How do you calculate it once it has been humidified in the tracheal?
Atmospheric air:
P(O2) = P(total) * oxygen proportion of air –> P(O2) = 760 mmHg * 0.21
Tracheal air:
P(O2) = [P(total) - P(H2O)] * oxygen proportion of air –> P(O2) = [P(total) - P(H2O)] * 0.21
What are the normal partial pressures of O2 and CO2 in alveolar air?
P(A)O2 = 104 mmHg P(A)CO2 = 40 mmHg
What is the equation for minute ventilation? What are the normal values for these variables?
minute ventilation = respiratory rate x tidal volume
RR = 12-20 breaths/min TV = 500 ml/breath
How much of tidal volume is anatomic dead space in a healthy individual?
Of a 500 ml tidal volume, 150 ml fills the conducting airways
What is the equation for alveolar ventilation?
Alveolar ventilation = RR x (tidal volume - anatomic dead space volume)
How can you calculate residual volume?
Helium dilution test:
C1 * V1 = C2 * V2 = C2 * (V1 + FRC)
At what lung capacity is resistance the lowest?
Functional residual capacity (FRC)
If a lung area has decreased ventilation, the lung will respond with [hypoxic vasoconstriction/hypocapnic bronchoconstriction].
hypoxic vasoconstriction
If a lung area has increased ventilation, the lung will respond with [hypoxic vasoconstriction/hypocapnic bronchoconstriction].
hypocapnic bronchoconstriction
What are the factors that influence pulmonary vascular resistance?
- compliance of a vessel
- sympathetic/parasympathetic tone
- lung volume
- hypoxia
- hypercapnia
- low pH
What is the definition of a shunt?
An area that is perfused but not ventilated
Pulmonary edema can occur when intravascular hydrostatic pressure is too [high/low] and intravascular oncotic pressure is too [high/low].
high hydrostatic pressure, low oncotic pressure
Pulmonary edema with alveolar flooding leads to hypoxemia by creating a ___.
Shunt
What is the difference between cardiogenic and non-cardiogenic pulmonary edema?
Pulmonary edema from increased intravascular pressure is cardiogenic; pulmonary edema from increased alveolar-capillary permeability is non-cardiogenic
What are the partial pressures of O2 and CO2 in atmospheric, tracheal, and alveolar conditions?
Atmospheric: PO2 = 160 mmHg, PCO2 = 0 mmHg
Tracheal: PO2 = 150 mmHg, PCO2 = 0 mmHg
Alveolar: PO2 = 104 mmHg, PCO2, = 40 mmHg
Using VCO2 and PACO2, what is the equation for alveolar ventilation?
VA = 0.863 * (VCO2/PACO2)
