Kárason S, Karlsen K L, Lundin S, Stenqvist O
Department of Anesthesia & Intensive Care, Sahlgrenska University Hospital, Göteborg, Sweden.
Acta Anaesthesiol Scand. 1999 Mar;43(3):308-15. doi: 10.1034/j.1399-6576.1999.430311.x.
Airway pressure measurements above the endotracheal tube will be distorted because of endotracheal tube resistance. To separate lung and chest wall compliance, esophageal pressure is conventionally measured with an air-filled balloon catheter, which is difficult to insert in unconscious patients. We have developed a methodology with fluid-filled catheters for intratracheal and esophageal pressure measurements.
Twelve anesthetized patients were studied. Tidal volumes were measured by side-stream spirometry. Airway pressures were measured at the Y-piece and in the trachea with fluid-filled pressure lines. Esophageal pressure was measured via the narrow lumen in a fluid-filled Salem double-lumen stomach tube, which was slowly retracted from the stomach up through the esophagus until maximal respiratory pressure readings and minimal cardiac artifacts were obtained. Lung mechanics were measured at different tidal volumes (TV) and positive end-expiratory pressure (PEEP).
There was a significant difference between airway pressures at the Y-piece and in the trachea. Total compliance significantly increased with increasing TV and decreased with increasing PEEP. Chest wall compliance increased significantly with increasing TV, while lung compliance did not change significantly. Two patients showed repeatedly marked increase in lung compliance at one specific ventilatory setting, an increase the proportion of which was not reflected by changes in total compliance.
Y-piece pressures are not representative of intratracheal pressures, which can be measured by inserting a fluid-filled pressure line through the tube. Esophageal pressure is easily recorded with a fluid-filled Salem double-lumen catheter. Large changes in lung compliance may pass unnoticed when only total compliance is monitored. Monitoring of lung compliance may offer an improved basis for decisions about ventilator settings.
由于气管内导管阻力，气管内导管上方的气道压力测量会出现偏差。为了区分肺和胸壁顺应性，传统上使用充气球囊导管测量食管压力，但这在无意识患者中难以插入。我们开发了一种使用充液导管测量气管内和食管压力的方法。
对12例麻醉患者进行研究。采用旁流式肺量计测量潮气量。使用充液压力管路在Y形接头处和气管内测量气道压力。通过充液的塞勒姆双腔胃管的窄腔测量食管压力，将其从胃中缓慢向上经食管抽出，直至获得最大呼吸压力读数和最小心脏伪迹。在不同潮气量（TV）和呼气末正压（PEEP）下测量肺力学。
Y形接头处和气管内的气道压力存在显著差异。总顺应性随TV增加而显著增加，随PEEP增加而降低。胸壁顺应性随TV增加而显著增加，而肺顺应性无显著变化。两名患者在一种特定通气设置下肺顺应性反复出现明显增加，这种增加在总顺应性变化中未得到体现。
Y形接头处压力不能代表气管内压力，气管内压力可通过将充液压力管路插入导管进行测量。使用充液的塞勒姆双腔导管可轻松记录食管压力。仅监测总顺应性时，肺顺应性的大变化可能会被忽视。监测肺顺应性可为呼吸机设置决策提供更好的依据。
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