Hedenstierna G, Santesson J, Norlander O
Acta Anaesthesiol Scand. 1976;20(4):334-42. doi: 10.1111/j.1399-6576.1976.tb05047.x.
Airway closure (closing capacity, CC), FRC, total efficiency of ventilation (lung clearance index, LCI) and distribution of inspired gas (nitrogen washout declay percentage, NWOD) were determined by nitrogen washout techniques and arterial PO2and PCO2 measured by standard electrodes in 10 extremely obese subjects, prior to an during anaesthesia and artifical ventilation. CC was normal, but because of small FRC, airway closure occurred within a tidal breath in 9 out of 10 subjects during spontaneous breathing, when awake. PO2 was reduced, the hypoxaemia correlating to the magnitude of airway closure. LCI was normal, but NWOD was borderline. During anaesthesia, CC was unaltered by FRC was further reduced, so that in nine subjects sirway closure occurred above FRC and tidal volume together. A marked increase in relative hypoxaemia was recorded. LCI and NWOD rose, indicating less efficient and less even ventilation. It is concluded that airway closure reasonably explains the marked hypoxaemia in obese subjects during anaesthesia, and that it may also be the reason for the uneven distribution of inspired gas.
采用氮洗脱技术测定了10名极度肥胖受试者在麻醉和人工通气前及过程中的气道闭合（闭合容量，CC）、功能残气量（FRC）、通气总效率（肺清除指数，LCI）和吸入气体分布（氮洗脱衰减百分比，NWOD），并使用标准电极测量动脉血氧分压（PO2）和二氧化碳分压（PCO2）。CC正常，但由于FRC较小，10名受试者中有9名在清醒自主呼吸时，潮气量范围内出现气道闭合。PO2降低，低氧血症与气道闭合程度相关。LCI正常，但NWOD处于临界值。麻醉期间，CC未改变，但FRC进一步降低，因此9名受试者气道闭合发生在FRC和潮气量之上。记录到相对低氧血症显著增加。LCI和NWOD升高，表明通气效率降低且分布不均。结论是，气道闭合合理地解释了肥胖受试者麻醉期间明显的低氧血症，并且它也可能是吸入气体分布不均的原因。
