A bedside definition of acute respiratory distress syndrome based on a conceptual model

Shigeki Kushimoto

doi:10.1186/cc12539

Abstract

We would like to thank Perel for his discerning comments [1], published in the previous issue of Critical Care, about our study [2]. We agree with his pathophysiologybased view of the diagnosis of acute respiratory distress syndrome (ARDS). In regard to his fi rst concern, we excluded 14 patients, who were judged to have respiratory failure secondary to sepsis-induced increased pulmonary vascular permeability, because owing to hypovolemia their values of extravascular lung water indexed to predicted body weight (extravascular lung water index, or EVLWI) were less than 10 mL/kg. Because EVLWI in patients with ARDS correlated not only with pulmonary vascular permeability but also with cardiac preload [2], we interpreted that their low levels of EVLWI could be secondary to inappro priate preload. Although the mechanisms of hypoxemia were unclear, ventilation/perfusion mismatch may occur because of lung perfusion failure. Th e pathophysiology of the condition of these patients must be clarifi ed in the future. In regard to the concern that the experts may have had some idea of the pulmonary vascular permeability index (PVPI) value during the exclusion and allocation processes, the value of EVLWI was provided only to determine whether the patients had pulmonary edema (EVLWI of at least 10 mL/kg), and the value itself was not discussed during the review process. Th erefore, estimating the PVPI value must be impractical. We believe that the direct measurement of PVPI and EVLW will provide an important advance over current methods of assessing the presence and origin of lung edema and the precise condition of ARDS [3] and could be incorporated into the future defi nition of ARDS.

Highlights

In regard to his first concern, we excluded 14 patients, who were judged to have respiratory failure secondary to sepsis-induced increased pulmonary vascular permeability, because owing to hypovolemia their values of extravascular lung water indexed to predicted body weight were less than 10 mL/kg
In regard to the concern that the experts may have had some idea of the pulmonary vascular permeability index (PVPI) value during the exclusion and allocation processes, the value of indexed extravascular lung water (EVLWI) was provided only to determine whether the patients had pulmonary edema (EVLWI of at least 10 mL/kg), and the value itself was not discussed during the review process
Kushimoto points out that the reason for excluding 14 patients from the final analysis was that, they were judged to have sepsis-induced increased pulmonary vascular permeability, they had normal EVLW values due to inappropriate preload. He believes that the weak correlation between EVLWI and the indexed intrathoracic blood volume (ITBVI) supports this physiologic explanation

Summary

Introduction

In regard to his first concern, we excluded 14 patients, who were judged to have respiratory failure secondary to sepsis-induced increased pulmonary vascular permeability, because owing to hypovolemia their values of extravascular lung water indexed to predicted body weight (extravascular lung water index, or EVLWI) were less than 10 mL/kg. In regard to the concern that the experts may have had some idea of the pulmonary vascular permeability index (PVPI) value during the exclusion and allocation processes, the value of EVLWI was provided only to determine whether the patients had pulmonary edema (EVLWI of at least 10 mL/kg), and the value itself was not discussed during the review process. Estimating the PVPI value must be impractical.

Results

Conclusion