Is pulmonary resistance constant, within the range of tidal volume ventilation, in patients with ARDS?

Abstract

When managing patients with acute respiratory distress syndrome (ARDS), respiratory system compliance is usually considered first and changes in resistance, although recognized, are neglected. Resistance can change considerably between minimum and maximum lung volume, but is generally assumed to be constant in the tidal volume range (VT). We measured resistance during tidal ventilation in 16 patients with ARDS or acute lung injury by the slice method and multiple linear regression analysis. Resistance was constant within VT in only six of 16 patients. In the remaining patients, resistance decreased, increased or showed complex changes. We conclude that resistance within VT varies considerably from patient to patient and that constant resistance within VT is not always likely.