Rossi Felipe S, Mascaretti Renata Suman, Haddad Luciana B, Freddi Norberto A, Mauad Thais, Rebello Celso M
Experimental Research Unit (LIM 30), Department of Pediatrics, Medical School, São Paulo University, São Paulo, SP, Brazil.
Clinics (Sao Paulo). 2008 Apr;63(2):237-44. doi: 10.1590/s1807-59322008000200013.
Studies comparing high frequency oscillatory and conventional ventilation in acute respiratory distress syndrome have used low values of positive end-expiratory pressure and identified a need for better recruitment and pulmonary stability with high frequency.
To compare conventional and high frequency ventilation using the lower inflection point of the pressure-volume curve as the determinant of positive end-expiratory pressure to obtain similar levels of recruitment and alveolar stability.
After lung lavage of adult rabbits and lower inflection point determination, two groups were randomized: conventional (positive end-expiratory pressure = lower inflection point; tidal volume=6 ml/kg) and high frequency ventilation (mean airway pressures= lower inflection point +4 cmH2O). Blood gas and hemodynamic data were recorded over 4 h. After sacrifice, protein analysis from lung lavage and histologic evaluation were performed.
The oxygenation parameters, protein and histological data were similar, except for the fact that significantly more normal alveoli were observed upon protective ventilation. High frequency ventilation led to lower PaCO2 levels.
Determination of the lower inflection point of the pressure-volume curve is important for setting the minimum end expiratory pressure needed to keep the airways opened. This is useful when comparing different strategies to treat severe respiratory insufficiency, optimizing conventional ventilation, improving oxygenation and reducing lung injury.
Utilization of the lower inflection point of the pressure-volume curve in the ventilation strategies considered in this study resulted in comparable efficacy with regards to oxygenation and hemodynamics, a high PaCO2 level and a lower pH. In addition, a greater number of normal alveoli were found after protective conventional ventilation in an animal model of acute respiratory distress syndrome.
比较急性呼吸窘迫综合征中高频振荡通气和传统通气的研究采用了较低的呼气末正压值，并发现需要通过高频通气实现更好的肺复张和肺稳定性。
以压力-容积曲线的低位拐点作为呼气末正压的决定因素，比较传统通气和高频通气，以获得相似程度的肺复张和肺泡稳定性。
对成年兔进行肺灌洗并测定低位拐点后，将两组随机分组：传统通气组（呼气末正压 = 低位拐点；潮气量 = 6 ml/kg）和高频通气组（平均气道压 = 低位拐点 + 4 cmH₂O）。在4小时内记录血气和血流动力学数据。处死后，进行肺灌洗蛋白分析和组织学评估。
除保护性通气时观察到明显更多的正常肺泡外，氧合参数、蛋白和组织学数据相似。高频通气导致较低的PaCO₂水平。
确定压力-容积曲线的低位拐点对于设定保持气道开放所需的最低呼气末压力很重要。在比较治疗严重呼吸功能不全的不同策略、优化传统通气、改善氧合和减少肺损伤时，这很有用。
本研究中所考虑的通气策略中利用压力-容积曲线的低位拐点，在氧合和血流动力学方面产生了相当的疗效，PaCO₂水平较高且pH值较低。此外，在急性呼吸窘迫综合征动物模型中，保护性传统通气后发现更多正常肺泡。
