Waters IV Flashcards
For ideal gas exchange, ventilation should be matched to _____.
perfusion
For the whole lung, the ventilation-perfusion ratio is given by:
Va/Q, Where Va= total alveolar ventilation and Q= total pulmonary blood flow (aka cardiac output)
Why is there less ventilation at the apical end of the lung compared to the base?
Intrapleural pressure is more negative, so transmural gradient is larger.. Thus, alveoli are larger and less compliant and less ventilation occurs
Why is there less perfusion at the apical end of the lung compared to the base?
lower intravascular pressures increase resistance
T or F. Blood flow and ventilation decrease moving upward in the lung at the same rate
F. Blood flow decreases faster
Where is the Va/Q ratio highest?
At the apex because perfusion drops faster than ventilation
Would the Va/Q be increased or decreased in a COPD patient?
increased in some regions and decreased in others
What is a normal Va/Q?
0.8
How does the Va/Q change in pulmonary embolus?
drastically increased
What is a shunt?
A situation where there is plenty of perfusion but an airway obstruction (Va/Q is 0)
Where is PaO2 highest in the vertical lung? What is it? What is it at the base?
at the apex - 130 mm Hg
base- 89 mm Hg
Where is Paco2 highest in the vertical lung? What is it? What is it at the base?
the base- 42 mm Hg
the apex- 28 mm Hg
Where in the vertical lung would ventilation be considered “wasted” in relation to perfusion
the apex
What is a pathologic consequence of PaO2 being higher in the apex?
organisms that use O2 as a nutrient source flourish in the apex
The A-a gradient is roughly 100:105 mm Hg for Po2
This can change in disease states
T or F. The A-a gradient of a shunt can be normalized using 100% O2
F.
T or F. The A-a gradient decreases in ventilation-perfusion mismatch
F. It increases (but CAN be normalized with 100% O2)
What happens in acute respiratory distress syndrome?
loss of barrier function causes fluid to leak into the air spaces and air diffusion is worse
How is pulmonary edema fluid cleared by the body?
edema fluid contains Na+ and type I and II pneumocytes move sodium from the alveoli into themselves via ENaC channels on the apical side and use a NaKATPase on the other side to remove it, and then water follows
How is oxygen carried?
- dissolved
- bound to hemoglobin
T or F. Pao2 is a measure of O2 bound to hemoglobin
F. It is DISSOLVED O2
Only 1.5% of all O2 in the blood is dissolved, the rest is bound to hemoglobin
How many molecules of O2 are bound by hemoglobin?
4
What is the O2 content of blood?
amount bound to hemoglobin + amount dissolved
= (O2 binding capacity * %saturation) + dissolved O2
Which of the following does decreased Hb affect:
a) O2 content of blood
b) O2 saturation
c) arterial Po2
only A