Khan N, Brown A, Venkataraman S T
Department of Anesthesiology/Critical Care Medicine, University of Pittsburgh, PA, USA.
Crit Care Med. 1996 Sep;24(9):1568-79. doi: 10.1097/00003246-199609000-00023.
To predict extubation success and failure in mechanically ventilated infants and children using bedside measures of respiratory function.
Prospective collection of data.
A university-affiliated children's hospital with a 51-bed critical care unit.
All infants and children who were mechanically ventilated for at least 24 hrs, except neonates < or = 37 wks gestation and patients with neuromuscular disease.
Bedside measurements of cardiorespiratory function were obtained immediately before extubation.
Extubation failure was defined as reintubation within 48 hrs of extubation in the absence of upper airway obstruction. Failure rates were calculated for different ranges (selected a priori) of preextubation measures of breathing effort, ventilatory support, respiratory mechanics, central inspiratory drive, and integrated indices useful in adults. Effort of spontaneous breathing was assessed by the respiratory rate standardized to age, the presence of retractions and paradoxical breathing, inspiratory pressure, maximal negative inspiratory pressure (maximal negative inspiratory pressure), inspiratory pressure/maximal negative inspiratory pressure ratio, and tidal volume indexed to body weight of a spontaneous breath. Ventilatory support was measured by the fraction of inspired oxygen (F10(2)), mean airway pressure, oxygenation index, and the fraction of total minute ventilation provided by the ventilator. Respiratory mechanics were assessed by determination of peak ventilatory inspiratory pressure and dynamic compliance. Central inspiratory drive was assessed by mean inspiratory flow. Frequency to tidal volume ratio and the compliance, rate, oxygenation, and pressure indexed to body weight, the integrated indices useful in predicting extubation failure in adults, were also calculated. Thirty-four of the 208 patients who were studied were reintubated for an overall failure rate of 16.3% (95% confidence interval 11.3% to 21.4%). The reasons for reintubation were poor effort (n = 8), excessive effort (n = 14), altered mental status or absent airway reflexes (n = 2), cardiovascular instability (n = 3), inadequate oxygenation (n = 3), respiratory acidosis (n = 3), and undocumented (n = 1). Extubation failure increased significantly with decreasing tidal volume indexed to body weight of a spontaneous breath, increasing F10(2), increasing mean airway pressure, increasing oxygenation index, increasing fraction of total minute ventilation provided by the ventilator, increasing peak ventilatory inspiratory pressure, or decreasing mean inspiratory flow (p < .05). Dynamic compliance showed a trend of increasing failure rate with decreasing dynamic compliance but did not reach statistical significance (p = .116). Respiratory rate standardized to age, inspiratory pressure, maximal negative inspiratory pressure, inspiratory pressure/maximal negative inspiratory pressure ratio, frequency to tidal volume ratio, and compliance, rate, oxygenation, and pressure did not show any trend in failure rate with increasing or decreasing values. Threshold values that defined a low risk (< or = 10%) and a high risk (> or = 25%) of extubation failure could be determined for tidal volume indexed to body weight of a spontaneous breath, F10(2), mean airway pressure, oxygenation index, fraction of total minute ventilation provided by the ventilator, peak ventilatory inspiratory pressure, dynamic compliance, and mean inspiratory flow. Neither a low nor a high risk of failure could be defined for frequency to tidal volume ratio or the compliance, rate, oxygenation, and pressure (CROP) index.
Bedside measurements of respiratory function can predict extubation success and failure in infants and children. Both a low risk and a high risk of failure can be determined using these measures. Integrated indices useful in adults do not reliably predict extubation success or failure in
采用床边呼吸功能测量方法预测机械通气婴幼儿和儿童拔管成功与失败情况。
前瞻性数据收集。
一所拥有51张床位重症监护病房的大学附属医院。
所有接受机械通气至少24小时的婴幼儿和儿童，但不包括孕周≤37周的新生儿和神经肌肉疾病患者。
在拔管前即刻进行床边心肺功能测量。
拔管失败定义为在无气道梗阻情况下拔管后48小时内再次插管。计算拔管前不同范围（预先设定）的呼吸努力、通气支持、呼吸力学、中枢吸气驱动以及对成人有用的综合指标的失败率。通过根据年龄标准化的呼吸频率、有无三凹征和反常呼吸、吸气压力、最大吸气负压、吸气压力/最大吸气负压比值以及自主呼吸潮气量与体重的比值来评估自主呼吸努力。通过吸入氧分数（F10(2)）、平均气道压、氧合指数以及呼吸机提供的每分钟通气总量的比例来测量通气支持。通过测定通气峰值吸气压力和动态顺应性来评估呼吸力学。通过平均吸气流量评估中枢吸气驱动。还计算了频率与潮气量比值以及顺应性、频率、氧合和压力与体重的比值，这些综合指标对预测成人拔管失败有用。在研究的208例患者中，有34例再次插管，总体失败率为16.3%（95%置信区间11.3%至21.4%）。再次插管的原因包括呼吸努力不足（n = 8）、呼吸努力过度（n = 14）、精神状态改变或气道反射消失（n = 2）、心血管不稳定（n = 3）、氧合不足（n = 3）、呼吸性酸中毒（n = 3）以及原因不明（n = 1）。随着自主呼吸潮气量与体重的比值降低、F10(2)升高、平均气道压升高、氧合指数升高、呼吸机提供的每分钟通气总量的比例升高、通气峰值吸气压力升高或平均吸气流量降低，拔管失败显著增加（p <.05）。动态顺应性显示随着动态顺应性降低失败率有升高趋势，但未达到统计学意义（p = 0.116）。根据年龄标准化的呼吸频率、吸气压力、最大吸气负压、吸气压力/最大吸气负压比值、频率与潮气量比值以及顺应性、频率、氧合和压力，其值升高或降低时失败率均无任何趋势。对于自主呼吸潮气量与体重的比值、F10(2)、平均气道压、氧合指数、呼吸机提供的每分钟通气总量的比例、通气峰值吸气压力、动态顺应性和平均吸气流量，可以确定定义拔管失败低风险（≤10%）和高风险（≥25%）的阈值。对于频率与潮气量比值或顺应性、频率、氧合和压力（CROP）指数，既无法定义低失败风险也无法定义高失败风险。
床边呼吸功能测量可预测婴幼儿和儿童拔管的成功与失败。使用这些测量方法可以确定低失败风险和高失败风险。对成人有用的综合指标不能可靠地预测婴幼儿和儿童拔管的成功或失败。
