Capdevila X, Perrigault P F, Ramonatxo M, Roustan J P, Peray P, d'Athis F, Prefaut C
Département d'Anesthésie Réanimation A, C.H.U. Montpellier, France.
Crit Care Med. 1998 Jan;26(1):79-87. doi: 10.1097/00003246-199801000-00020.
This study examined, using noninvasive means, the changes in breathing pattern and inspiratory muscle pressure-time indices during difficult progressive withdrawal of pressure-support ventilation.
A prospective analysis of the temporal evolution of several respiratory variables in difficult-to-wean patients.
A university hospital intensive care unit.
A heterogeneous group of 17 patients receiving prolonged mechanical ventilation.
Daily measurements of breathing pattern and respiratory muscle performance parameters in difficult-to-wean patients.
We examined breathing pattern variables, rapid shallow breathing (respiratory rate/tidal volume), tracheal occlusion pressure, maximal inspiratory pressure (P(I)max), and the tension-time index of the inspiratory muscles (TTmus = P(I)/P(I)max x Ti/Ttot) (where Ti/Ttot is inspiratory fraction of the cycle). All measurements were repeated at 24-hr intervals throughout the difficult weaning period. The patients were extubated on satisfying ten of 12 classical weaning criteria. Eleven patients were successfully weaned from mechanical ventilation while six patients were not. Weaning failure was associated with the following: a) longer periods of mechanical ventilation before weaning; b) high values of tracheal occlusion pressure, respiratory rate, minute ventilation, and effective impedance maintained throughout the difficult weaning period; and c) persistent high PaCO2 and intrinsic positive end-expiratory pressure values. As the weaning failure patients' inspiratory muscles confronted an increasing inspiratory load, values of the tension-time index of the inspiratory muscles entered or remained in the fatigue zone. In contrast, weaning success patients normalized their breathing pattern and decreased their tracheal occlusion pressure, effective impedance, and tension-time index values.
Breathing pattern alterations and respiratory muscle performance impairments lead to ventilator dependency after prolonged mechanical ventilation. The measurement of variables such as the noninvasive tracheal occlusion pressure, inspiratory power of breathing, and tension-time index of the inspiratory muscles facilitate the management of difficult-to-wean patients.
本研究采用非侵入性方法，观察在困难的压力支持通气逐步撤离过程中呼吸模式及吸气肌压力-时间指标的变化。
对难以撤机患者的多个呼吸变量的时间演变进行前瞻性分析。
大学医院重症监护病房。
17例接受长时间机械通气的异质性患者。
对难以撤机患者的呼吸模式和呼吸肌功能参数进行每日测量。
我们检测了呼吸模式变量、快速浅呼吸（呼吸频率/潮气量）、气管阻断压、最大吸气压力（P(I)max）以及吸气肌的张力-时间指数（TTmus = P(I)/P(I)max×Ti/Ttot）（其中Ti/Ttot为呼吸周期的吸气分数）。在整个困难撤机期间，每隔24小时重复进行所有测量。患者在满足12项经典撤机标准中的10项时拔除气管插管。11例患者成功撤机，6例未成功。撤机失败与以下因素相关：a）撤机前机械通气时间较长；b）在整个困难撤机期间，气管阻断压、呼吸频率、分钟通气量和有效阻抗值较高；c）持续高PaCO2和内源性呼气末正压值。随着撤机失败患者的吸气肌面临的吸气负荷增加，吸气肌的张力-时间指数值进入或保持在疲劳区。相比之下，撤机成功的患者呼吸模式正常化，气管阻断压、有效阻抗和张力-时间指数值降低。
长时间机械通气后，呼吸模式改变和呼吸肌功能损害导致呼吸机依赖。测量诸如无创气管阻断压、呼吸吸气功率和吸气肌张力-时间指数等变量有助于管理难以撤机的患者。
