Distribution of inspired gas during anesthesia and artificial ventilation

Abstract

Distribution of inspired gas was compared during spontaneous ventilation in the conscious state, during spontaneous ventilation in the anesthetized state, and during artificial ventilation in the anesthetized, paralyzed state in nine human subjects. Uniformity of distribution of inspired gas was measured using an open-circuit nitrogen-washout method. Rate and pattern of nitrogen elimination during oxygen breathing as well as calculated indices of uniformity of distribution of inspired gas and efficiency of over-all pulmonary ventilation did not vary significantly among the three conditions studied. Induction of anesthesia or substitution of artificial ventilation for spontaneous ventilation, therefore, caused no detectable change in uniformity of distribution of inspired gas. intrapulmonary mixing; respiratory changes during anesthesia Submitted on January 24, 1963

Studies on Intrapulmonary Gas Distribution in the Normal Subject Influence of Anaesthesia and Artificial Ventilation

“…These are summarized in Table 1. BERGMAN (1963) found no differences between awake and anaesthetized conditions, whether the latter was during spontaneous breathing or mechanical ventilation. REHDER et al (1971) reported a more rapid nitrogen washout with mechanical ventilation at a standardized tidal volumc, and attributed this to a reduced F R C and an altered, presumably more even distribution of inspired gas.…”

Factors influencing the arterial oxygen tension during anaesthesia with artificial ventilation. 1965

“…There is none. Secondly, the distribution of inspired gas has now been found to be normal during anaesthesia (Bergman, 1963) and defects of distribution are a consistent finding in patients with severe emphysema. Finally, the slope of the expired carbon dioxide concentration (plotted against expired volume) is practically normal during anaesthesia (Nunn and Hill, 1960).…”

Postoperative Hypoxemia: Common, Undetected, and Unsuspected After Bariatric Surgery

“…Reduction in functional residual capacity (FRC) routinely accompanies induction of general anesthesia and causes atelectasis [18,19]. Merely assuming the supine position causes up to a 20% reduction in FRC, observed in normal subjects [20].…”