Johannigman J A, Branson R D, Campbell R, Hurst J M
Department of Surgery, Wilford Hall, United States Air Force, San Antonio, TX.
Respir Care. 1990 Oct;35(10):952-9.
Transport of critically ill, mechanically ventilated patients from intensive care units for diagnostic and therapeutic procedures has become common in the last decade. Maintenance of adequate oxygenation and ventilation during transport is mandatory. We evaluated the Hamilton MAX transport ventilator in the laboratory and in the clinical arena to determine its usefulness during in-hospital transport.
In the laboratory, we determined the MAX's ability to assure tidal volume (VT) delivery in the face of decreasing compliance of a test lung, and we tested the alarm system. Using a two-compartment lung model modified to simulate spontaneous breathing, we also evaluated the responsiveness of the demand valve. The clinical evaluation was accomplished by comparing arterial blood gases and ventilator settings in the intensive care unit to those during transport.
As lung compliance was reduced from 0.1 to 0.02 L/cm H2O [1.0 to 0.20 L/kPa], delivered VT fell significantly at each set VT. The alarm systems performed according to manufacturer's specifications. The demand valve triggered appropriately without positive end-expiratory pressure (PEEP), but as PEEP was increased, triggering became more difficult. The demand valve is referenced to ambient pressure and cannot compensate for elevated end-expiratory pressures. During patient transport, arterial blood gases were comparable to those achieved in the ICU. Because an inspired oxygen concentration of 1.0 was used during transport, arterial oxygenation (PaO2) was significantly greater (123 +/- 75 vs 402 +/- 85 torr [16.4 +/- 10 vs 53.6 +/- 11 kPa]). A higher ventilator rate was required during transport to prevent tachypnea (7 +/- 3 vs 12 +/- 6 breaths/min), and peak inspiratory pressure (PIP) was higher during transport (40 +/- 8 vs 52 +/- 11 cm H2O [3.9 +/- 0.8 vs 5.1 +/- 1.1 kPa]).
The MAX is a reliable transport ventilator, capable of maintaining adequate ventilation and oxygenation in a majority of mechanically ventilated patients. Care should be taken to assure adequate VT delivery at high PIP, and ventilator rate may require adjustment to prevent tachypnea associated with triggering the non-PEEP-compensated demand valve when PEEP greater than 8 cm H2O [0.8 kPa] is used.
在过去十年中，将重症机械通气患者从重症监护病房转运至进行诊断和治疗操作的地点已变得很常见。转运过程中维持充足的氧合和通气是必需的。我们在实验室和临床环境中评估了汉密尔顿MAX转运呼吸机，以确定其在院内转运期间的实用性。
在实验室中，我们测定了MAX在测试肺顺应性降低时确保潮气量（VT）输送的能力，并测试了警报系统。使用经过改良以模拟自主呼吸的双腔肺模型，我们还评估了按需阀的响应性。临床评估通过比较重症监护病房中的动脉血气和呼吸机设置与转运期间的情况来完成。
随着肺顺应性从0.1降至0.02L/cm H₂O[1.0至0.20L/kPa]，在每个设定的VT下输送的VT均显著下降。警报系统按制造商的规格运行。在没有呼气末正压（PEEP）的情况下，按需阀触发正常，但随着PEEP增加，触发变得更加困难。按需阀以环境压力为参考，无法补偿升高的呼气末压力。在患者转运期间，动脉血气与在重症监护病房中测得的结果相当。由于转运期间使用的吸入氧浓度为1.0，动脉氧合（PaO₂）显著更高（123±75对402±85托[16.4±10对53.6±11kPa]）。转运期间需要更高的呼吸机频率以防止呼吸急促（7±3对12±6次/分钟），并且转运期间的吸气峰压（PIP）更高（40±8对52±11cm H₂O[3.9±0.8对5.1±1.1kPa]）。
MAX是一种可靠的转运呼吸机，能够在大多数机械通气患者中维持充足的通气和氧合。应注意在高PIP时确保充足的VT输送，并且当使用大于8cm H₂O[0.8kPa]的PEEP时，可能需要调整呼吸机频率以防止与触发无PEEP补偿的按需阀相关的呼吸急促。
