Hubble C L, Gentile M A, Tripp D S, Craig D M, Meliones J N, Cheifetz I M
Department of Pediatrics, Duke University Medical Center, Durham, NC 27710, USA.
Crit Care Med. 2000 Jun;28(6):2034-40. doi: 10.1097/00003246-200006000-00059.
Using a modification of the Bohr equation, single-breath carbon dioxide capnography is a noninvasive technology for calculating physiologic dead space (V(D)/V(T)). The objective of this study was to identify a minimal V(D)/V(T) value for predicting successful extubation from mechanical ventilation in pediatric patients.
Prospective, blinded, clinical study.
Medical and surgical pediatric intensive care unit of a university hospital.
Intubated children ranging in age from 1 wk to 18 yrs.
None.
Forty-five patients were identified by the pediatric intensive care unit clinical team as meeting criteria for extubation. Thirty minutes before the planned extubation, each patient was begun on pressure support ventilation set to deliver an exhaled tidal volume of 6 mL/kg. After 20 mins on pressure support ventilation, an arterial blood gas was obtained, V(D)/V(T) was calculated, and the patient was extubated. Over the next 48 hrs, the clinical team managed the patient without knowledge of the preextubation V(D)/V(T) value. Of the 45 patients studied, 25 had V(D)/V(T) < or =0.50. Of these patients, 24 of 25 (96%) were successfully extubated without needing additional ventilatory support. In an intermediate group of patients with V(D)/V(T) between 0.50 and 0.65, six of ten patients (60%) successfully extubated from mechanical ventilation. However, only two of ten patients (20%) with a V(D)/V(T) > or =0.65 were successfully extubated. Logistic regression analysis revealed a significant association between lower V(D)/V(T) and successful extubation.
A V(D)/V(T) < or =0.50 reliably predicts successful extubation, whereas a V(D)/V(T) >0.65 identifies patients at risk for respiratory failure following extubation. There appears to be an intermediate V(D)/V(T) range (0.51-0.65) that is less predictive of successful extubation. Routine V(D)/V(T) monitoring of pediatric patients may permit earlier extubation and reduce unexpected extubation failures.
单次呼吸二氧化碳波形图是一种采用改良玻尔方程的无创技术，用于计算生理死腔（V(D)/V(T)）。本研究的目的是确定一个预测儿科患者机械通气成功脱机的最低V(D)/V(T)值。
前瞻性、盲法临床研究。
一所大学医院的儿科医学与外科重症监护病房。
年龄从1周龄至18岁的插管儿童。
无。
儿科重症监护病房临床团队确定45例患者符合脱机标准。在计划脱机前30分钟，开始对每名患者进行压力支持通气，设置呼气潮气量为6 mL/kg。压力支持通气20分钟后，采集动脉血气，计算V(D)/V(T)，然后对患者进行脱机。在接下来的48小时内，临床团队在不知脱机前V(D)/V(T)值的情况下对患者进行管理。在研究的45例患者中，25例V(D)/V(T)≤0.50。在这些患者中，25例中有24例（96%）成功脱机，无需额外的通气支持。在V(D)/V(T)介于0.50至0.65之间的中间组患者中，10例中有6例（60%）成功脱机。然而，V(D)/V(T)≥0.65的10例患者中只有2例（20%）成功脱机。逻辑回归分析显示较低的V(D)/V(T)与成功脱机之间存在显著关联。
V(D)/V(T)≤0.50可可靠地预测成功脱机；而V(D)/V(T)>0.65则提示患者脱机后有呼吸衰竭风险。似乎存在一个中间V(D)/V(T)范围（0.51 - 0.65），其对成功脱机的预测性较差。对儿科患者进行常规V(D)/V(T)监测可能有助于更早脱机并减少意外脱机失败。
