BIO 115 Lecture Notes - Lecture 17: Hemoglobin, Blood Gas Tension, Pulmonary Embolism
Document Summary
Venous blood that bypasses the gas exchange region of the lung entirely. Bronchial and thebesian circulations in normal individuals (this is only a very small amount) Right to left have the greatest direct effect on arterial po2. The po2 and the shape of the o2 dissociation curve determine the oxygen concentration in the pulmonary capillary blood (concentration is the dependent variable). Increasing fio2 would elevate the po2 of blood leaving pulmonary capillaries to but would have only a small effect on its oxygen concentration (hemoglobin is saturated). Thus, the arterial oxygen concentration after mixing with shunted blood would change very little and hypoxemia would persist. Although shunted blood would tend to elevate paco2, the resulting hypercapnia (unlike hypoxemia) would be minimized by increasing alveolar ventilation. Some causes of hypoxemia are refractory and others are responsive to oxygen therapy. Responsive hypoxemia: arterial hypoxemia that significantly improves when fio2 is increased.
