Almeida-Junior Armando A, da Silva Marcos T Nolasco, Almeida Celize C B, Ribeiro José D
Pediatric Intensive Care Unit, Center for Investigation in Pediatrics, State University of Campinas Medical School, Campinas, SP, Brazil.
Pediatr Crit Care Med. 2007 Jul;8(4):372-7. doi: 10.1097/01.PCC.0000269389.51189.A8.
To evaluate the association between deadspace/tidal volume ratio (Vd/Vt) and gas exchange variables: Pao2, Paco2, Pao2/Fio2, arterial/alveolar oxygen tension ratio (Pao2/PAo2), alveolar-arterial oxygen tension difference/arterial oxygen tension ratio (P(A-a)o2/Pao2), carbon dioxide production (Vco2), ventilation index ([Paco2 x peak inspiratory pressure x mechanical respiratory rate]/1000), and oxygenation index ([mean airway pressure x Fio2 x 100]/Pao2), all measured at an early stage in children with obstructive acute respiratory failure.
Prospective, cross-sectional, observational study.
Pediatric intensive care unit, university hospital.
Twenty-nine infants with acute bronchiolitis, defined according to clinical and radiologic criteria. Children with chronic pulmonary disease, neuromuscular disease, congenital cardiopathies, or hemodynamic instability were excluded.
Measurements were made between 24 and 72 hrs of mechanical ventilation using volumetric capnography and arterial blood gas analysis.
The following variables significantly correlated with Vd/Vt, calculated using Spearman's correlation coefficient (rs): Pao2 (rs = -0.63, p < .001), Pao2/Fio2 (rs = -0.56, p = .002), Pao2/PAo2 (rs = -0.46, p = .012), P(A-a)o2/Pao2 (rs = -0.46, p = .012), Paco2 (rs = 0.51, p = .005), Vco2 (rs = -0,62, p < .01), oxygenation index (rs = 0.48, p = .009), and ventilation index (rs = -0.53, p = .003). A statistically significant association was found between an increase in Vd/Vt and severity of lung injury, defined as Pao2/Fio2 <200 (p = .03, Mann-Whitney).
In the study population, Vd/Vt not only reflected ventilatory disorders, as is well recognized, but also was associated with disturbances of oxygenation. These results warrant further evaluation of the usefulness of serial measurement of Vd/Vt as a marker of disease severity in severe acute bronchiolitis and other causes of respiratory failure.
评估死腔/潮气量比值（Vd/Vt）与气体交换变量之间的关联，这些变量包括：动脉血氧分压（Pao2）、动脉血二氧化碳分压（Paco2）、氧合指数（Pao2/Fio2）、动脉血氧分压与肺泡氧分压比值（Pao2/PAo2）、肺泡-动脉氧分压差与动脉血氧分压比值（P(A-a)o2/Pao2）、二氧化碳产生量（Vco2）、通气指数（[Paco2×吸气峰压×机械呼吸频率]/1000）以及氧合指数（[平均气道压×Fio2×100]/Pao2），所有这些变量均在患有阻塞性急性呼吸衰竭的儿童早期进行测量。
前瞻性、横断面、观察性研究。
大学医院儿科重症监护病房。
29例根据临床和放射学标准定义的急性细支气管炎婴儿。排除患有慢性肺部疾病、神经肌肉疾病、先天性心脏病或血流动力学不稳定的儿童。
在机械通气24至72小时之间，使用容积式二氧化碳描记法和动脉血气分析进行测量。
使用Spearman相关系数（rs）计算得出，以下变量与Vd/Vt显著相关：Pao2（rs = -0.63，p <.001）、Pao2/Fio2（rs = -0.56，p =.002）、Pao2/PAo2（rs = -0.46，p =.012）、P(A-a)o2/Pao2（rs = -0.46，p =.012）、Paco2（rs = 0.51，p =.005）、Vco2（rs = -0.62，p <.01）、氧合指数（rs = 0.48，p =.009）以及通气指数（rs = -0.53，p =.003）。Vd/Vt升高与肺损伤严重程度之间存在统计学上的显著关联，肺损伤严重程度定义为Pao2/Fio2 <200（p =.03，Mann-Whitney检验）。
在本研究人群中，Vd/Vt不仅如人们所熟知的那样反映通气障碍，还与氧合障碍有关。这些结果值得进一步评估连续测量Vd/Vt作为严重急性细支气管炎和其他呼吸衰竭病因中疾病严重程度标志物的实用性
