Medicina Pulmonar e Respiratória

Alveolar Stress, How to Measure?

Abstract

Erikson Custódio Alcântara, Wátila de Moura Sousa, Carlos Oscar Paschetta, Pablo Jorge Galíndez and Krislainy de Sousa Corrêa

The Alveolar Stress Index is an under explored tool, promising and may help to prevent the deleterious effects of mechanical ventilation. The aim of this study was to describe the importance of Alveolar Stress Index tool, as well as aspects in ventilatory support. This tool evaluates the pressure-volume loop, which, although measures the pulmonary mechanical stress, it does not consider the heterogeneity of the respiratory system. The Alveolar Stress Index, checked in screen monitor of mechanical ventilation equipments, facilitates the detection of alveolar collapse zones (alveolar stress index <0.9) or overdistension (alveolar stress index >1.1) of lung areas. If the index value indicates alveolar collapse (atelectrauma=pulmonary lesion caused by the cyclic opening and closing of alveolar units and distal airways), it is recommended to increase the PEEP (Positive end-expiratory pressure). On the other hand, if the value indicates alveolar distension (volutrauma=pulmonary lesion induced by high tidal volume, thus causing the distension of the lung parenchyma), the initial orientation is to decrease the tidal volume. It is worth mentioning that the intention of measuring alveolar stress index is not to replace other parameters, but to add it to patient monitoring, to the median and multicompartmental observation of the ventilated area, considering the heterogeneity of lung ventilation distribution, so that more tools are available to the professional, thus avoiding or hindering lung injuries, when under mechanical ventilation.