Yang K L, Tobin M J
Division of Pulmonary and Critical Care Medicine, University of Texas Health Science Center, Houston 77030.
Crit Care Med. 1991 Jan;19(1):49-53. doi: 10.1097/00003246-199101000-00014.
a) To determine the variation in methods used to measure minute ventilation (VE) in patients who receive mechanical ventilation; b) to determine the effect of supplemental oxygen on VE, respiratory rate (RR), and tidal volume (VT) measurements.
Telephone survey of hospitals, and a randomized control trial.
Medical and surgical ICUs in a university hospital.
Thirty-three patients who had required mechanical ventilation because of the inability to sustain adequate spontaneous ventilation. All patients were considered ready to undergo a weaning trial by their physicians.
Spontaneous VE, RR, VT, and SaO2 were measured both in the presence and absence of supplemental oxygen; measurements were obtained in a randomized manner.
a) In a telephone survey of hospitals throughout the country, we found that the measurement of VE is variably obtained during room air breathing or in the presence of supplemental oxygen. b) Measurements of VE increased from 11.0 +/- 0.8 L/min while patients received supplemental oxygen to 13.5 +/- 1.1 L/min while patients breathed room air (p less than .001). Of 15 patients who had a VE less than 10 L/min while receiving supplemental oxygen, seven developed a value greater than 10 L/min while breathing room air; thus, a weaning trial might have been inappropriately deferred in these patients. c) Mean SaO2 decreased from 95.0 +/- 0.6% while breathing supplemental oxygen to 90.2 +/- 1.1% while breathing room air (p less than .001).
Measurements of VE in patients being considered for a weaning trial can result in significant oxygen desaturation if obtained during room air breathing, and the values obtained can significantly overestimate the patient's true ventilatory requirements, since most patients receive supplemental oxygen during a weaning trial. Standardized methods of measuring VE in critically ill patients need to be developed.
a）确定接受机械通气患者测量分钟通气量（VE）所使用方法的差异；b）确定补充氧气对VE、呼吸频率（RR）和潮气量（VT）测量值的影响。
对医院进行电话调查及一项随机对照试验。
一所大学医院的内科和外科重症监护病房。
33例因无法维持足够自主通气而需要机械通气的患者。所有患者经医生评估均准备好进行撤机试验。
在有和没有补充氧气的情况下测量自主VE、RR、VT和动脉血氧饱和度（SaO2）；测量以随机方式进行。
a）在对全国医院的电话调查中，我们发现VE的测量在呼吸室内空气或补充氧气时获取方式各不相同。b）患者接受补充氧气时VE测量值为11.0±0.8L/分钟，呼吸室内空气时增加至13.5±1.1L/分钟（p<0.001）。15例接受补充氧气时VE低于10L/分钟的患者中，7例呼吸室内空气时VE值大于10L/分钟；因此，这些患者的撤机试验可能被不适当地推迟了。c）平均SaO2从呼吸补充氧气时的95.0±0.6%降至呼吸室内空气时的90.2±1.1%（p<0.001）。
对于考虑进行撤机试验的患者，如果在呼吸室内空气时测量VE，可能会导致显著的氧饱和度下降，并且所获得的值可能会显著高估患者的真实通气需求，因为大多数患者在撤机试验期间接受补充氧气。需要制定危重症患者测量VE的标准化方法。
