Roithmaier A, Hultzsch W, Lipowsky G, Reinhardt D
Department of Pediatrics, University of Munich, FRG.
Crit Care Med. 1994 Sep;22(9 Suppl):S71-6. doi: 10.1097/00003246-199422091-00007.
Evaluation of a modified, computer-controlled, shutter method to determine the complete intrapulmonary pressure course and to ascertain the expiratory time constant for the respiratory system during high-frequency positive pressure ventilation.
Prospective clinical study.
Neonatal intensive care unit in a university hospital.
Sixteen premature newborns (mean gestational age 26 +/- 2 [SD] wks, birth weight 741 +/- 138 g) were studied at various times during their clinical course.
Installation of the shutter and air flow interruption did not result in any impairment of clinical and respiratory conditions. Time constants were between 58 and 190 msecs. In six patients, an inadvertent positive end-expiratory pressure (1 to 4.5 cm H2O) was found; in these patients only, expiratory time set at the respirator was < 4 time constants. In 13 measurements of nine patients, measured intrapulmonary peak inspiratory pressure was considerably lower (1 to 5 cm H2O) than that value set at the respirator.
The computer-controlled shutter method is noninvasive and applicable without impairment, even in preterm neonates with birth weights of < 1000 g. This method provides important information to optimize respiratory therapy, particularly knowledge of the individual time constant. To avoid inadvertent positive end-expiratory pressure and gas trapping, expiratory time should be > 4 time constants.
评估一种改良的、计算机控制的快门方法，以确定高频正压通气期间呼吸系统的完整肺内压力过程并确定呼气时间常数。
前瞻性临床研究。
大学医院的新生儿重症监护病房。
16例早产儿（平均胎龄26±2[标准差]周，出生体重741±138克）在其临床病程中的不同时间接受研究。
安装快门和气流中断未导致临床和呼吸状况出现任何损害。时间常数在58至190毫秒之间。6例患者发现有意外的呼气末正压（1至4.5厘米水柱）；仅在这些患者中，呼吸机设置的呼气时间<4个时间常数。在9例患者的13次测量中，测得的肺内吸气峰压比呼吸机设置的值低得多（1至5厘米水柱）。
计算机控制的快门方法是非侵入性的，即使对于出生体重<1000克的早产儿也可无损害地应用。该方法为优化呼吸治疗提供重要信息，尤其是关于个体时间常数的知识。为避免意外的呼气末正压和气体潴留，呼气时间应>4个时间常数。
