异氟烷麻醉期间上呼吸道的可塌陷性

Collapsibility of the upper airway during anesthesia with isoflurane.

作者信息

Eastwood Peter R, Szollosi Irene, Platt Peter R, Hillman David R

机构信息

West Australian Sleep Disorders Research Institute, Department of Pulmonary Physiology, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia.

出版信息

Anesthesiology. 2002 Oct;97(4):786-93. doi: 10.1097/00000542-200210000-00007.

DOI:10.1097/00000542-200210000-00007

PMID:12357141

Abstract

BACKGROUND

The unprotected upper airway tends to obstruct during general anesthesia, yet its mechanical properties have not been studied in detail during this condition.

METHODS

To study its collapsibility, pressure-flow relationships of the upper airway were obtained at three levels of anesthesia (end-tidal isoflurane = 1.2%, 0.8%, and 0.4%) in 16 subjects while supine and spontaneously breathing on nasal continuous positive airway pressure. At each level of anesthesia, mask pressure was transiently reduced from a pressure sufficient to abolish inspiratory flow limitation (11.8 +/- 2.7 cm H(2)O) to pressures resulting in variable degrees of flow limitation. The relation between mask pressure and maximal inspiratory flow was determined, and the critical pressure at which the airway occluded was recorded. The site of collapse was determined from simultaneous measurements of nasopharyngeal, oropharyngeal, and hypopharyngeal and esophageal pressures.

RESULTS

The airway remained hypotonic (minimal or absent intramuscular genioglossus electromyogram activity) throughout each study. During flow-limited breaths, inspiratory flow decreased linearly with decreasing mask pressure (r(2) = 0.86 +/- 0.17), consistent with Starling resistor behavior. At end-tidal isoflurane of 1.2%, critical pressure was 1.1 +/- 3.5 cm H O; at 0.4% it decreased to -0.2 +/- 3.6 cm H(2)O ( < 0.05), indicating decreased airway collapsibility. This decrease was associated with a decrease in end-expiratory esophageal pressure of 0.6 +/- 0.9 cm H(2)O ( < 0.05), suggesting an increased lung volume. Collapse occurred in the retropalatal region in 14 subjects and in the retrolingual region in 2 subjects, and did not change with anesthetic depth.

CONCLUSIONS

Isoflurane anesthesia is associated with decreased muscle activity and increased collapsibility of the upper airway. In this state it adopts the behavior of a Starling resistor. The decreased collapsibility observed with decreasing anesthetic depth was not a consequence of neuromuscular activity, which was unchanged. Rather, it may be related to increased lung volume and its effect on airway wall longitudinal tension. The predominant site of collapse is the soft palate.

摘要

背景

在全身麻醉期间，无保护的上呼吸道易于阻塞，然而在此种情况下其力学特性尚未得到详细研究。

方法

为研究其上呼吸道的可塌陷性，在16名受试者处于仰卧位并经鼻持续气道正压自主呼吸时，于三种麻醉水平（呼气末异氟烷浓度分别为1.2%、0.8%和0.4%）下获取上呼吸道的压力-流量关系。在每种麻醉水平下，面罩压力从足以消除吸气流量限制的压力（11.8±2.7 cmH₂O）短暂降低至导致不同程度流量限制的压力。确定面罩压力与最大吸气流量之间的关系，并记录气道闭塞时的临界压力。通过同时测量鼻咽、口咽、下咽和食管压力来确定塌陷部位。

结果

在每项研究过程中，气道始终处于低张力状态（颏舌肌肌电图活动最小或无活动）。在流量受限呼吸期间，吸气流量随面罩压力降低呈线性下降（r² = 0.86±0.17），符合斯塔林电阻器特性。呼气末异氟烷浓度为1.2%时，临界压力为1.1±3.5 cmH₂O；浓度为0.4%时降至-0.2±3.6 cmH₂O（P<0.05），表明气道可塌陷性降低。这种降低与呼气末食管压力降低0.6±0.9 cmH₂O相关（P<0.05），提示肺容积增加。14名受试者的塌陷发生在腭后区域，2名受试者的塌陷发生在舌后区域，且不随麻醉深度改变。