Weiler N, Latorre F, Eberle B, Goedecke R, Heinrichs W
Department of Anaesthesiology, Johannes Gutenberg University School of Medicine, Mainz, Germany.
Anesth Analg. 1997 May;84(5):1025-8. doi: 10.1097/00000539-199705000-00013.
A potential risk of the laryngeal mask airway (LMA) is incomplete mask seal, which causes air leakage or insufflation of air into the stomach. The objective of the present study was to assess respiratory mechanics, quantify air leakage, and measure gastric air insufflation in patients ventilated via the LMA. Thirty patients were studied after induction of anesthesia but prior to any surgical manipulations. After the insertion of the LMA, patients were ventilated with increasing tidal volumes until one of the three following end points were reached: 1) gastric air insufflation, 2) airway pressure > 40 cm H2O, or 3) limitation of further increase in tidal volume by air leakage. The following variables were determined:inspired volume (VI), expired volume (VE), maximum inspiratory pressure (Pmax), airway pressure at gastric inflation (Pinfl), respiratory time constant (RC), compliance (C), resistance (R), and leakage fraction (FL). Respiratory mechanics were in the physiological range. Gastric insufflation occurred in 27% of the patients at inspiratory pressures between 19 and 33 cm H2O. Air leakage of more than 10% was evident at inspiratory pressures between 25 and 34 cm H2O. The end point of 40 cm H2O airway pressure was reached in only three patients. We conclude that the LMA is not better in preventing airway pressure transmission to the esophagus than a conventional face mask. However, a high FL is associated with reduced gastric air insufflation.
喉罩气道（LMA）的一个潜在风险是面罩密封不完全，这会导致漏气或将空气吹入胃内。本研究的目的是评估通过LMA通气患者的呼吸力学、量化漏气情况并测量胃内气体吹入量。在30例患者麻醉诱导后但在任何手术操作之前进行研究。插入LMA后，随着潮气量增加对患者进行通气，直至达到以下三个终点之一：1）胃内气体吹入；2）气道压力>40 cm H₂O；或3）由于漏气导致潮气量进一步增加受限。测定以下变量：吸入气量（VI）、呼出气量（VE）、最大吸气压力（Pmax）、胃充气时的气道压力（Pinfl）、呼吸时间常数（RC）、顺应性（C）、阻力（R）和漏气分数（FL）。呼吸力学处于生理范围内。27%的患者在吸气压力为19至33 cm H₂O时出现胃充气。在吸气压力为25至34 cm H₂O时，明显出现超过10%的漏气。仅3例患者达到40 cm H₂O气道压力的终点。我们得出结论，在防止气道压力传导至食管方面，LMA并不比传统面罩更好。然而，高漏气分数与胃内气体吹入减少有关。
