Dipartimento di Anestesiologia, Terapia Intensiva e Scienze Dermatologiche, Fondazione IRCCS Ca' Granda - Ospedale Maggiore Policlinico, Università degli Studi di Milano, Milan, Italy.
Curr Opin Crit Care. 2012 Feb;18(1):42-7. doi: 10.1097/MCC.0b013e32834f17d9.
To describe the physiological meaning and the clinical application of the lung stress and strain concepts.
The end-inspiratory plateau pressure and ratio of tidal volume/ideal body weight are inadequate surrogates for the end-inspiratory stress (equal to the transpulmonary pressure) and the end-inspiratory strain (change in lung volume relative to the resting volume). For a given plateau pressure or tidal volume/ideal body weight, stress and strain may vary largely due to the variability of chest wall elastance and the resting lung volume. The injurious limits of stress and strain in healthy lungs are reached when stress and strain reach the total lung capacity. This occurs when the resting lung volume (the baby lung in case of acute respiratory distress syndrome) is increased by two-fold to three-fold. As these limits are rarely reached in clinical practice and damage has been reported with stress and strain well below this upper limit, this implies the presence in the lung parenchyma of regions which act as stress raisers or pressure multipliers. These are primarily linked to the inhomogeneous distribution of local stress and strain.
End-inspiratory stress and strain, as well as the lung inhomogeneity and the stress raisers, must be taken in account when setting mechanical ventilation.
描述肺应力和应变概念的生理意义和临床应用。
吸气末平台压和潮气量/理想体重比不能充分替代吸气末压力（等于跨肺压）和吸气末应变（与静息肺容积相比的肺容积变化）。对于给定的平台压或潮气量/理想体重，由于胸壁弹性和静息肺容积的可变性，应力和应变可能会有很大差异。当应力和应变达到总肺容量时，健康肺的损伤极限就会达到。当静息肺容积（急性呼吸窘迫综合征中的婴儿肺）增加一倍到三倍时，就会发生这种情况。由于这些极限在临床实践中很少达到，并且已经有报道称在低于这个上限的情况下出现了应变和应变损伤，这意味着在肺实质中存在作为应力集中或压力倍增器的区域。这些主要与局部应力和应变的不均匀分布有关。
在设置机械通气时，必须考虑吸气末压力和应变，以及肺不均匀性和压力倍增器。
