Oxygen Requirements in the Early Postoperative Period (48 Hours)

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Abstract
Postoperative oxygen requirements were measured in 70 unselected patients undergoing 46 nonthoracic and 26 thoracic surgical procedures. Ventilation and respiratory gas exchange were determined 24-48 hrs. prior to operation and on the mornings and afternoons of the 1st and 2nd days following operation. Postopera-tive O2 uptake and CO2 output were not significantly different from preoperative control values in both nonthoracic and thoracic procedures. Ventilation and O2 consumption, and alveolar ventilation and CO2 output, usually were related linearly in both groups of patients, suggest-ing that postoperative ventilation was regulated relative to metabolic demands of the body. In the absence of cardiopulmonary disease or complications, this regulation was accomplished with maintenance of normal efficiency of respiration. Disproportionate alterations, consiting of excessive ventilation relative to gas exchange, occurred in about 15% of determinations. This resulted in decreased efficiency of respiration, with varying degrees of pulmonary insufficiency, and was observed most commonly in patients with chronic obstructive pulmonary disease. The importance of the O2-cost of breathing in postoperative patients is discussed and the necessity for further studies emphasized.