Background and purpose: Manual hyperinflation (MH) of the lungs is commonly used by physiotherapists in the treatment of intubated mechanically ventilated patients with the aim of increasing alveolar oxygenation, reversing atelectasis or mobilizing pulmonary secretions. However, the efficacy of MH, used in isolation, has not been clearly established.
Method: This randomized, controlled trial investigated the effects of MH on lung compliance (CL), the arterial oxygen to fraction of inspired oxygen ratio (PaO2:FIO2) and the alveolar-arterial oxygen tension difference (A-a)PO2 in 100 medically stable, mechanically ventilated subjects who had undergone coronary artery surgery (CAS). Post-CAS subjects were used for this study as they constitute a large, homogeneous and accessible group. Subjects were randomized to either a control group (non-MH group) or to a treatment group (MH group) which received MH within four hours of surgery.
Results: After four minutes of MH there were significant improvements in CL, PaO2:FIO2 and (A-a)PO2 with values remaining above baseline measures at 60 min post-intervention. The mean improvement in CL was 6 ml/cmH2O (approximately 15%), 56 mmHg for PaO2:FIO2 (approximately 17%) and 29 mmHg for (A-a)PO2 (approximately 17%) immediately post-intervention. No significant changes in mean CL, PaO2:FIO2 or (A-a)PO2 were seen in the non-MH group.
Conclusions: MH performed in the stable ventilated patient significantly increased CL and PaO2:FIO2 and decreased (A-a)PO2, but the clinical significance of this improvement is unclear. Further investigations are required to validate the findings of this study as well as to determine the therapeutic value of MH on patient outcome.