作为一种在床边监测通气充分性的新方法的通气比率分析。
Analysis of ventilatory ratio as a novel method to monitor ventilatory adequacy at the bedside.
作者信息
Sinha Pratik, Fauvel Nicholas J, Singh Pradeep, Soni Neil
出版信息
Crit Care. 2013 Feb 27;17(1):R34. doi: 10.1186/cc12541.
INTRODUCTION
Due to complexities in its measurement, adequacy of ventilation is seldom used to categorize disease severity and guide ventilatory strategies. Ventilatory ratio (VR) is a novel index to monitor ventilatory adequacy at the bedside. VR=(VEmeasured × PaCO₂measured)/(VEpredicted × PaCO₂ideal). VEpredicted is 100 mL.Kg-1.min-1 and PaCO₂ideal is 5 kPa. Physiological analysis shows that VR is influenced by dead space (VD/VT) and CO₂ production (VCO₂). Two studies were conducted to explore the physiological properties of VR and assess its use in clinical practice.
METHODS
Both studies were conducted in adult mechanically ventilated ICU patients. In Study 1, volumetric capnography was used to estimate daily VD/VT and measure VCO₂ in 48 patients. Simultaneously, ventilatory ratio was calculated using arterial blood gas measurements alongside respiratory and ventilatory variables. This data was used to explore the physiological properties of VR. In Study 2, 224 ventilated patients had daily VR and other respiratory variables, baseline characteristics, and outcome recorded. The database was used to examine the prognostic value of VR.
RESULTS
Study 1 showed that there was significant positive correlation between VR and VD/VT (modified r = 0.71) and VCO₂ (r = 0.14). The correlation between VR and VD/VT was stronger in mandatory ventilation compared to spontaneous ventilation. Linear regression analysis showed that VD/VT had a greater influence on VR than VCO₂ (standardized regression coefficient 1/1-VD/VT: 0.78, VCO₂: 0.44). Study 2 showed that VR was significantly higher in non-survivors compared to survivors (1.55 vs. 1.32; P < 0.01). Univariate logistic regression showed that higher VR was associated with mortality (OR 2.3, P < 0.01), this remained the case after adjusting for confounding variables (OR 2.34, P = 0.04).
CONCLUSIONS
VR is an easy to calculate bedside index of ventilatory adequacy and appears to yield clinically useful information.
引言
由于通气测量的复杂性，通气充足性很少用于对疾病严重程度进行分类和指导通气策略。通气比率（VR）是一种用于在床边监测通气充足性的新指标。VR =（实测分钟通气量×实测动脉血二氧化碳分压）/（预测分钟通气量×理想动脉血二氧化碳分压）。预测分钟通气量为100 mL·kg⁻¹·min⁻¹，理想动脉血二氧化碳分压为5 kPa。生理分析表明，VR受死腔（VD/VT）和二氧化碳产生量（VCO₂）的影响。进行了两项研究以探讨VR的生理特性并评估其在临床实践中的应用。
方法
两项研究均在成年机械通气的ICU患者中进行。在研究1中，使用容积式二氧化碳描记法估计48例患者的每日VD/VT并测量VCO₂。同时，使用动脉血气测量以及呼吸和通气变量计算通气比率。该数据用于探索VR的生理特性。在研究2中，记录了224例通气患者的每日VR和其他呼吸变量、基线特征及结局。该数据库用于检验VR的预后价值。
结果
研究1表明，VR与VD/VT（修正r = 0.71）和VCO₂（r = 0.14）之间存在显著正相关。与自主通气相比，强制通气时VR与VD/VT之间的相关性更强。线性回归分析表明，VD/VT对VR的影响大于VCO₂（标准化回归系数1/1 - VD/VT：0.78，VCO₂：0.44）。研究2表明，非存活者的VR显著高于存活者（1.55对1.32；P < 0.01）。单因素逻辑回归表明，较高的VR与死亡率相关（OR 2.3，P < 0.01），在调整混杂变量后情况依然如此（OR 2.34，P = 0.04）。
结论
VR是一种易于计算的床边通气充足性指标，似乎能产生临床有用信息。
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