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Ventilation/Perfusion

Terms in this set (28)

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?
4 L/min is the alveolar ventilation rate (V).

5 L/min is the pulmonary blood flow (Q).

Normally, V/Q = 0.8

[(4; L/min)/(5 L/min) = V/Q = 0.81
A V/Q ratio between zero and unity (0 < V/Q < 1) indicates what?
A V/Q ratio between zero and unity (0 < V/Q < 1) indicates a relative shunt.
What is indicated by a V/Q ratio that is greater than one (V/Q > 1)?
A V/Q > 1 indicates deadspacing.
Compared with the apex of the lung, the base of the lung exhibits (when the individual is awake and upright) greater or lesser perfusion?
Greater. Perfusion (blood flow) is best in dependent lung. The base of the lung is dependent in the upright (sitting or standing) individual.
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)?
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.
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)?
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.
What is the importance of maintaining a normal ventilation-to-perfusion relationship?
A normal ventilation-to-perfusion relationship is required to keep PaCO2 and Pa02 in the normal range.
In a lung unit that exhibits absolute shunt, what is the V/Q ratio, the amount of ventilation, and the amount of perfusion?
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.
What is the V/Q ratio in a lung unit that is ventilated but completely unperfused (e.g., pulmonary emboli)?
V/Q = infinity if the lung unit is ventilated and completely unperfused, because Q = 0.
State the numeric values for absolute deadspace and absolute shunt.
With absolute deadspace, V/Q = infinity (V/O) and with absolute shunt, V/Q = 0 (0/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?
Lower. The V/Q ratio is high in nondependent lung and low in dependent lung.
What are the consequences of clipping a bronchus but leaving the vas-culature intact during left pneumonectomy?
An intrapulmonary shunt develops if a bronchus is clipped and the vasculature is left intact. When a shunt develops, Pa02 decreases.
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?
There is a large shunt when one lung is nonfunctional. PaO2 decreases possibly/probably resulting in arterial hypoxemia. If the lung is removed, there is no shunt and hence there is no arterial hypoxemia.
Where is the dependent lung found? Where is the non-dependent lung found? When are the lung bases dependent and the lung apices non-dependent?
The Dependent lung is the region of the lung that is closest to the ground and the non-dependent lung is located farthest from the ground. The bases of the lung are dependent in the upright (sitting or standing) individual. The apices of the lung are non-dependent in the upright (sitting or standing) individual. The dependent lung is dependent on gravity and upon support from the base of the structure.
How is minute alveolar ventilation calculated? A healthy 65 kg 30-year-old has what alveolar ventilation if respiratory rate is 12 per minute and tidal volume is 450 mL?
Alveolar ventilation is minute ventilation minus dead space ventilation. Alveolar ventilation = (tidal volume - dead space) x ventilation rate. For a healthy patient, dead space is 2 mL/kg. Alveolar ventilation for the 65 kg 30-year-old is:

(450 mL - 65 kg x 2 mL/kg) x 12/min =

(450 mL - 130 mL) x 12/min =

320 mL x 12/min = 3,840 mL = 3.84 liters.
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