Pelosi P, Solca M, Ravagnan I, Tubiolo D, Ferrario L, Gattinoni L
Istituto di Anestesia e Rianimazione, Universita' degll Studi di Milano, IRCCS Ospedale Maggiore, Italy.
Crit Care Med. 1996 Jul;24(7):1184-8. doi: 10.1097/00003246-199607000-00020.
To evaluate the effect of two commonly used heat and moisture exchangers on respiratory function and gas exchange in patients with acute respiratory failure during pressure-support ventilation.
Prospective, randomized trial.
Intensive care unit of a university hospital.
Fourteen patients with moderate acute respiratory failure, receiving pressure-support ventilation.
Patients were assigned randomly to two treatment groups, in which two different heat and moisture exchangers were used: Hygroster (DAR S.p.A., Mirandola, Italy) with higher deadspace and lower resistance (group 1, n = 7), and Hygrobac-S (DAR S.p.A.) with lower deadspace and higher resistance (group 2, n = 7). Patients were assessed at three pressure-support levels: a) baseline (10.3 +/- 2.4 cm H2O for group 1, 9.3 +/- 1.3 cm H2O for group 2); b) 5 cm H2O above baseline; and c) 5 cm H2O below baseline. Measurements obtained with the heat and moisture exchangers were compared with those values obtained using the standard heated hot water humidifier.
At baseline pressure-support ventilation, the insertion of both heat and moisture exchangers induced in all patients a significant increase in the following parameters: minute ventilation (12.4 +/- 3.2 to 15.0 +/- 2.6 L/min for group 1, and 11.8 +/- 3.6 to 14.2 +/- 3.5 L/min for group 2); static intrinsic positive end-expiratory pressure (2.9 +/- 2.0 to 5.1 +/- 3.2 cm H2O for group 1, and 2.9 +/- 1.7 to 5.5 +/- 3.0 cm H2O for group 2); ventilatory drive, expressed as P41 (2.7 +/- 2.0 to 5.2 +/- 4.0 cm H2O for group 1, and 3.3 +/- 2.0 to 5.3 +/- 3.0 cm H2O for group 2); and work of breathing, expressed as either power (8.8 +/- 9.4 to 14.5 +/- 10.3 joule/ min for group 1, and 10.5 +/- 7.4 to 16.6 +/- 11.0 joule/min for group 2) or work per liter of ventilation (0.6 +/- 0.6 to 1.0 +/- 0.7 joule/L for group 1, and 0.8 +/- 0.4 to 1.1 +/- 0.5 joule/L. for group 2). These increases also occurred when pressure-support ventilation was both above and below the baseline level, although at high pressure support the increase in work of breathing with heat and moisture exchangers was less evident. Gas exchange was unaffected by heat and moisture exchangers, as minute ventilation increased to compensate for the higher deadspace produced in the circuit by the insertion of heat and moisture exchangers.
The tested heat and moisture exchangers should be used carefully in patients with acute respiratory failure during pressure-support ventilation, since these devices substantially increase minute ventilation, ventilatory drive, and work of breathing. However, an increase in pressure-support ventilation (5 to 10 cm H2O) may compensate for the increased work of breathing.
评估两种常用的热湿交换器对急性呼吸衰竭患者在压力支持通气期间呼吸功能和气体交换的影响。
前瞻性随机试验。
大学医院重症监护病房。
14例中度急性呼吸衰竭患者，接受压力支持通气。
患者被随机分为两个治疗组，使用两种不同的热湿交换器：死腔较大、阻力较低的Hygroster（意大利米兰多拉的DAR S.p.A.公司）（第1组，n = 7），以及死腔较小、阻力较高的Hygrobac-S（DAR S.p.A.公司）（第2组，n = 7）。在三个压力支持水平对患者进行评估：a）基线（第1组为10.3±2.4 cm H₂O，第2组为9.3±1.3 cm H₂O）；b）高于基线5 cm H₂O；c）低于基线5 cm H₂O。将使用热湿交换器获得的测量值与使用标准加热热水加湿器获得的值进行比较。
在基线压力支持通气时，两种热湿交换器的插入均使所有患者的以下参数显著增加：分钟通气量（第1组从12.4±3.2升/分钟增至15.0±2.6升/分钟，第2组从11.8±3.6升/分钟增至14.2±3.5升/分钟）；静态内源性呼气末正压（第1组从2.9±2.0 cm H₂O增至5.1±3.2 cm H₂O，第2组从2.9±1.7 cm H₂O增至5.5±3.0 cm H₂O）；以P41表示的通气驱动（第1组从2.7±2.0 cm H₂O增至5.2±4.0 cm H₂O），第2组从3.3±２.0 cm H₂O增至5.3±3.0 cm H₂O）；以及以功率（第1组从8.8±9.4焦耳/分钟增至14.5±10.3焦耳/分钟，第2组从10.5±7.4焦耳/分钟增至16.6±11.0焦耳/分钟）或以每升通气量的功（第1组从0.6±0.6焦耳/升增至1.0±0.7焦耳/升，第2组从0.8±0.4焦耳/升增至1.1±0.5焦耳/升）表示的呼吸功。当压力支持通气高于和低于基线水平时，这些增加也会出现，尽管在高压力支持下，热湿交换器导致的呼吸功增加不太明显。气体交换不受热湿交换器影响，因为分钟通气量增加以补偿热湿交换器插入回路中产生的较大死腔。
在急性呼吸衰竭患者压力支持通气期间，应谨慎使用所测试的热湿交换器，因为这些设备会大幅增加分钟通气量、通气驱动和呼吸功。然而，增加压力支持通气（5至10 cm H₂O）可能会补偿增加的呼吸功。
