Wu A, Drummond G B
University Department of Anaesthesia, Critical Care and Pain Medicine Royal Infirmary, Edinburgh EH16 4SA, UK.
Br J Anaesth. 2006 Apr;96(4):510-5. doi: 10.1093/bja/ael035. Epub 2006 Feb 20.
Respiratory movements in patients after abdominal surgery are frequently abnormal, with associated disturbances in the pattern of inspiratory pressure generation. The reasons for these abnormalities are not clear and have been attributed to impaired action of the diaphragm. However, an alternative is that partial airway obstruction could trigger reflex activation of the inspiratory ribcage muscles, which would cause a similar pattern of inspiratory pressure change. Direct measurement of electrical activity can indicate if reflex activation of inspiratory muscles occurs when partial airway obstruction is present.
In an open study, we implanted electrodes to measure the EMG of scalene, intercostal and external oblique abdominal muscles in patients after lower abdominal surgery. Analgesia was with morphine i.v. by patient control. We used nasal cannulae to measure nasal airflow and compared EMG activity when airway obstruction was present with activity when breathing was not obstructed.
The pattern of activity of the different muscles was distinct. Intercostal activity reached a maximum during inspiration, before the scalene muscles, whereas scalene activity increased in phase with increasing lung volume. Abdominal muscle activity commenced when expiratory flow had ceased and continued until the next inspiration. In all three muscle groups, partial airway obstruction did not alter muscle activity.
Partial airway obstruction does not activate inspiratory ribcage muscles, in patients receiving morphine for postoperative analgesia after lower abdominal surgery. Changes in respiratory pressures and abnormalities of chest wall movement described in previous studies cannot be attributed to reflex responses and probably result from increased airway resistance and abdominal muscle action.
腹部手术后患者的呼吸运动常常异常，吸气压力产生模式也会出现相关紊乱。这些异常的原因尚不清楚，以往认为是膈肌功能受损所致。然而，另一种可能是部分气道阻塞会触发吸气时胸廓肌肉的反射性激活，从而导致类似的吸气压力变化模式。直接测量电活动可以表明在存在部分气道阻塞时是否会发生吸气肌的反射性激活。
在一项开放性研究中，我们在下腹部手术后的患者体内植入电极，以测量斜角肌、肋间肌和腹外斜肌的肌电图。通过患者自控静脉注射吗啡进行镇痛。我们使用鼻套管测量鼻气流，并比较存在气道阻塞时的肌电图活动与呼吸未受阻时的活动。
不同肌肉的活动模式各不相同。肋间肌活动在吸气过程中达到最大值，早于斜角肌，而斜角肌活动随肺容积增加而同步增加。腹肌活动在呼气气流停止时开始，并持续到下一次吸气。在所有三组肌肉中，部分气道阻塞并未改变肌肉活动。
在下腹部手术后接受吗啡术后镇痛的患者中，部分气道阻塞不会激活吸气时的胸廓肌肉。先前研究中描述的呼吸压力变化和胸壁运动异常不能归因于反射反应，可能是气道阻力增加和腹肌作用的结果。
