Ventilator beyond ventilation: impact of the increase of elastic recoil pressure of a respiratory system through positive end expiratory pressure–zero positive end expiratory pressure vs manually assisted cough vs manually assisted cough adding positive end expiratory pressure 12 cmH₂O on the peak expiratory flow in mechanically ventilated patients

Introduction

Physiotherapy has many techniques that are able to promote secretion clearance, decreasing airway obstruction in the attempt to improve ventilation homogeneity and exchanged blood gases [1–3]. These techniques aim to promote the increase of peak expiratory flow (PEF) and expiratory volume, probably through augmentation of the elastic recoil pressure produced by exsufflation forces. Our purpose was to assess the impact of the three usual modalities of bronchial hygiene on peak expiratory flow.

Design

A prospective, experimental and blinded study.

Methods

Twenty-six patients (mean age, 60 ± 13.5 years) admitted to the Hospital Português Clinical–Surgery Intensive Care Unit, requiring total support ventilation and with positive end expiratory pressure (PEEP) of 5.5 ± 1.44 cmH₂O, were assessed. Patients with a history of pulmonary disease, hemodynamic instability, rib cage and/or abdominal abnormalities, scoliosis, pregnancy, obesity, cardiac pacemaker, pneumothorax, unstable thorax and PEEP higher than 10 cmH₂O were excluded. PEF was measured by Navigator Graphics Monitor (Newport Medical Instruments Inc., Newport Beach, CA, USA) during PEEP–zero positive end expiratory pressure (ZEEP), manually assisted cough with baseline PEEP (MAC), mean PEEP of 5.5 ± 1.44 cmH₂O, and MAC with adding PEEP of 12 cmH₂O. Techniques were performed five times for each patient, with intervals of 5 min between each technique application. The Kruskal–Wallis test was used to compare the groups. The Mann–Whitney rank-sum test was used to compare the techniques two by two. Differences with P < 0.05 were considered significant.

Results

Means of the PEF variations are presented in Table 1. The comparison of MAC vs PEEP–ZEEP and MAC vs MAC with PEEP of 12 cmH₂O showed statistical significance (P < 0.0002 and P < 0.01, respectively). When PEEP–ZEEP and MAC with PEEP of 12 cmH₂O were compared, no statistical significant differences were noted.

Table 1

Conclusion

PEEP–ZEEP and MAC with PEEP of 12 cmH₂O were more efficient on the increase of peak expiratory flow than MAC with baseline PEEP. Considering that there were no statistical differences between the more efficient techniques, the relationship of risk/benefit and the institutional aspects, the choice of the technique should be powerful to consider.