Cardiovascular implementations of respiratory measurements.
Direct measurement of oxygen consumption (VO2) as an important on-line available parameter in patient monitoring has only very recently been accomplished with the development of the totally closed circuit anesthesia ventilator Physioflex. When the respiratory parameters measured with the same system and inspiratory oxygen concentration are in normal range adequate cellular oxygen supply is furthermore dependent on the following factors that influence oxygen delivery (DO2) to the tissue: the general factors, oxygen transport capacity of the blood and cardiac output and (local factors) distribution of tissue perfusion (including e.g. local occlusion, sludging, steal syndrome). In critically ill patients general impairment of oxygen delivery might occur as well as maldistribution. Studies were performed in experimental animals and patients to get some insight into the cardiovascular implementations of these respiratory measurements. Oxygen delivery has been manipulated (in pigs) by sodium nipride infusion (drop of blood pressure and cardiac output) to critical levels of oxygen supply. Endotoxin was infused with typical hemodynamic changes (first, hyperdynamic phase with increase of pulmonary artery pressure, decrease of mean arterial pressure and increase of cardiac output and, second, hypodynamic phase with low cardiac output). VO2 and oxygen delivery were controlled in a patient with a ruptured aneurysm, with impairment of oxygen transport capacity due to low hemoglobin but maintained circulating volume.
Van der Zee
H
H
Dept. of Anesthesiology, Albany Medical Center, NY.
Verkaaik
A P
AP
D000764:Anesthesia, Closed-Circuit; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D004731:Endotoxins / Q000494:pharmacology; D006801:Humans; D009599:Nitroprusside / Q000494:pharmacology; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D013552:Swine
D004731:Endotoxins; D009599:Nitroprusside; D010100:Oxygen