# Ventilation:Perfusion Flashcards

1
Q

Compared with the apex of the lung, the base of the lung exhibits (when the individual is awake and upright) greater or lesser perfusion?

A

Greater. Perfusion (blood flow) is best in dependent lung. The base of the lung is dependent in the upright (sitting or standing) individual.

2
Q

What is the principle reason blood flow to dependent lung is greater than blood flow to non-dependent lung?

A

Gravity.

3
Q

Compared with the apex of the lung, the base of the lung exhibits (when the individual is awake and upright) greater or lesser ventilation?

A

Greater. Total ventilation is best in dependent lung.

4
Q

In the awake spontaneously breathing patient in the lateral decubitus position, where is ventilation best (dependent or nondependent lung), and where is perfusion best (dependent or nondependent lung)?

A

In the awake spontaneously breathing patient in the lateral decubitus position, ventilation is best in dependent (lower) lung and perfusion is best in dependent (lower) lung.

5
Q

In the anesthetized and paralyzed patient in the lateral decubitus position, where is ventilation best (dependent or nondependent lung), and where is perfusion best (dependent or nondependent lung)?

A

When the patient in the lateral decubitus position is anesthetized and paralyzed, perfusion is best in the dependent (lower) lung, but ventilation is best in the nondependent upper lung.

6
Q

The healthy adult lung receives each minute an alveolar ventilation of about how many liters and a pulmonary blood flow of how many liters? What is the average resting ventilation:perfusion (V/Q) ratio?

A

4 l/min is the alveolar ventilation rate (V). 5 l/min is the pulmonary blood flow (Q). Normally, V/Q = 0.8 [(4L/min)/(5 L/min) = V/Q = 0.8].

7
Q

What is the importance of maintaining a normal ventilation-to-perfusion relationship?

A

A normal ventilation-to-perfusion relationship is required to keep PaCO2 and Pa02 in the normal range.

8
Q

In a lung unit that exhibits absolute shunt, what is the V/Q ratio, the amount of ventilation, and the amount of perfusion?

A

In a lung unit that exhibits absolute shunt, V/Q = 0 because V = 0; perfusion (Q) may be decreased somewhat because of hypoxic pulmonary vasoconstriction.

9
Q

A V/Q ratio between zero and unity (0 < V/Q < 1) indicates what?

A

A V/Q ratio between zero and unity (0 < V/Q < 1) indicates a relative shunt.

10
Q

What is indicated by a V/Q ratio that is greater than one (V/Q > 1)?

A

A V/Q > 1 indicates deadspacing.

11
Q

What is the V/Q ratio in a lung that is ventilated but completely unperfused (eg pulmonary emboli)?

A

V/Q = infinity if the lung unit is ventilated and completely unperfused, because Q = 0.

12
Q

State the numeric values for absolute deadspace and absolute shunt.

A

With absolute deadspace, V/Q = infinity (V/0) and with absolute shunt, V/Q = 0 (0/Q).

13
Q

Describe how gravity affects the size of alveoli.

A

At end-expiration, dependent alveoli are smaller than nondependent alveoli.

14
Q

Compared with the apex of the lung, the base of the lung exhibits (when the individual is awake and upright) higher or lower V/Q ratio?

A

Lower. The V/Q ratio is high in nondependent lung and low in dependent lung.

15
Q

What are the consequences of clipping a bronchus but

leaving the vasculature intact during left pneumonectomy?

A

An intrapulmonary shunt develops if a bronchus is clipped and the vasculature is left intact. When a shunt develops, Pa02 decreases.

16
Q

Why does a patient who has two lungs, but only one

functioning properly, present a problem, whereas a patient with one lung lives a fairly normal life?

A

There is a large shunt when one lung is nonfunctional. Pa02 decreases possibly/probably resulting in arterial hypoxemia. If the lung is removed, there is no shunt and hence there is no arterial hypoxemia.