Abstract
In order to assess the relative contribution of the lung and the chest wall to the derangements of respiratory mechanics in chronic obstructive pulmonary disease (COPD) patients with acute ventilatory failure (AVF), we studied eight COPD patients undergoing controlled mechanical ventilation for AVF and nine normal subjects anaesthetized for surgery as a control group. With the use of the interrupter technique together with the oesophageal balloon technique we measured: static lung and chest wall elastances (E[st,L] and E[st,w], respectively), maximum (R[L,max]), minimum (R[L,min]) and additional (deltaR[L]) lung resistances, additional chest wall resistance (deltaRw) and, in the COPD group, total intrinsic positive end-expiratory pressure (PEEPtot). Measurements were repeated at 0, 5, 10 and 15 cmH2O of applied positive end-expiratory pressure (PEEP). We found that, in the COPD group: 1) both E(st,w) and deltaRw were higher than in the normal group; 2) R(L,max) was markedly increased due to an increase of both R(L,min) and deltaRL; 3) even low levels of PEEP increased PEEPtot; 4) PEEP did not reduce elastance or total resistance of either the lung or the chest wall. We conclude that chest wall mechanics are abnormal in chronic obstructive pulmonary disease patients with acute ventilatory failure undergoing controlled mechanical ventilation and that positive end-expiratory pressure does not seem to be effective in reducing either elastance or resistance of the lung or chest wall.
Highlights
With the use of the interrupter technique together with the oesophageal balloon technique we measured: static lung and chest wall elastances (Est,L and Est,w, respectively), maximum (RL,max), minimum (RL,min) and additional (∆RL) lung resistances, additional chest wall resistance (∆Rw) and, in the chronic obstructive pulmonary disease (COPD) group, total intrinsic positive end-expiratory pressure (PEEPtot)
Since the use of positive end-expiratory pressure (PEEP) in COPD patients undergoing controlled mechanical ventilation is still controversial [2, 6], we investigated the early effects of acute changes of PEEP upon partitioned respiratory mechanics
Est,L did not differ between the two groups and it increased with PEEP in both COPD and normal subjects (p
Summary
With the use of the interrupter technique together with the oesophageal balloon technique we measured: static lung and chest wall elastances (Est,L and Est,w, respectively), maximum (RL,max), minimum (RL,min) and additional (∆RL) lung resistances, additional chest wall resistance (∆Rw) and, in the COPD group, total intrinsic positive end-expiratory pressure (PEEPtot). We conclude that chest wall mechanics are abnormal in chronic obstructive pulmonary disease patients with acute ventilatory failure undergoing controlled mechanical ventilation and that positive end-expiratory pressure does not seem to be effective in reducing either elastance or resistance of the lung or chest wall. The mechanical properties of the total respiratory system in patients with acute exacerbation of chronic obstructive pulmonary disease (COPD) have been extensively investigated, reporting an increase in respiratory resistance as a hallmark [1, 2]. KATZ et al [4] suggested that, at least in some mechanically ventilated patients with acute respiratory failure, chest wall mechanics may be abnormal, and, more recently, an unexpected alteration of chest wall mechanical properties has been reported in patients with adult respiratory distress syndrome [5]
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