Marini J J, Ravenscraft S A
University of Minnesota, St. Paul-Ramsey Medical Center, Minneapolis/St. Paul 55101-2595.
Crit Care Med. 1992 Oct;20(10):1461-72.
To discuss the theoretical relationship of mean alveolar pressure to its most easily measured analog, the mean airway pressure, and to describe the key determinants, measurement considerations, and clinical implications of this index.
Relevant articles from the medical and physiologic literature, as well as mathematical arguments developed in this article from first principles.
Theoretical, experimental, and clinical information that elucidates the physiologic importance, measurement, or adverse consequences of mean airway pressure.
Mathematical models were used in conjunction with data from the published literature to develop a unified description of the physiological and clinical relevance of mean airway pressure.
Geometrical and mathematical analyses demonstrate that shared elements comprise mean airway pressure and mean alveolar pressure, two variables that are related by the formula: mean alveolar pressure = mean airway pressure + (VE/60) x (RE-RI), where VE, RE, and RI are minute ventilation and expiratory and inspiratory resistances, respectively. Clear guidelines can be developed for selecting the site of mean airway pressure determination, for specifying technical requirements for mean airway pressure measurement, and for delineating clinical options to adjust the level of mean airway pressure. Problems in viewing mean airway pressure as a reflection of mean alveolar pressure can be interpreted against the theoretical basis of their interrelationship. In certain settings, mean airway pressure closely relates to levels of ventilation, arterial oxygenation, cardiovascular function, and barotrauma. Because mean airway pressure is associated with both beneficial and adverse effects, a thorough understanding of its theoretical and practical basis is integral to formulating an effective pressure-targeted strategy of ventilatory support.
Mean airway pressure closely reflects mean alveolar pressure, except when flow-resistive pressure losses differ greatly for the inspiratory and expiratory phases of the ventilatory cycle. Under conditions of passive inflation, mean airway pressure correlates with alveolar ventilation, arterial oxygenation, hemodynamic performance, and barotrauma. We encourage wider use of this index, appropriately measured and interpreted, as well as its incorporation into rational strategies for the ventilatory management of critical illness.
探讨平均肺泡压与其最易测量的类似指标——平均气道压之间的理论关系，并描述该指标的关键决定因素、测量注意事项及临床意义。
医学和生理学文献中的相关文章，以及本文从基本原理推导得出的数学论证。
阐明平均气道压的生理重要性、测量方法或不良后果的理论、实验和临床信息。
运用数学模型结合已发表文献中的数据，对平均气道压的生理和临床相关性进行统一描述。
几何和数学分析表明，平均气道压和平均肺泡压包含共同要素，这两个变量通过公式相关联：平均肺泡压 = 平均气道压 + (每分钟通气量/60)×(呼气阻力 - 吸气阻力)，其中每分钟通气量、呼气阻力和吸气阻力分别用VE、RE和RI表示。可为选择平均气道压测定部位、明确平均气道压测量的技术要求以及划定调整平均气道压水平的临床选项制定明确指南。将平均气道压视为平均肺泡压反映指标时出现的问题可依据它们相互关系的理论基础进行解读。在某些情况下，平均气道压与通气水平、动脉氧合、心血管功能及气压伤密切相关。由于平均气道压既有有益作用又有不良影响，透彻理解其理论和实践基础对于制定有效的压力靶向通气支持策略至关重要。
平均气道压能密切反映平均肺泡压，除非通气周期的吸气相和呼气相的流动阻力压力损失差异极大。在被动充气条件下，平均气道压与肺泡通气、动脉氧合、血流动力学表现及气压伤相关。我们鼓励更广泛地使用该指标，并进行适当测量和解读，同时将其纳入危重病通气管理的合理策略中。
