Comparison of changes in tidal volume associated with expiratory rib cage compression and expiratory abdominal compression in patients on prolonged mechanical ventilation

[Purpose] This study was designed to compare and clarify the relationship between expiratory rib cage compression and expiratory abdominal compression in patients on prolonged mechanical ventilation, with a focus on tidal volume. [Subjects and Methods] The subjects were 18 patients on prolonged mechanical ventilation, who had undergone tracheostomy. Each patient received expiratory rib cage compression and expiratory abdominal compression; the order of implementation was randomized. Subjects were positioned in a 30° lateral recumbent position, and a 2-kgf compression was applied. For expiratory rib cage compression, the rib cage was compressed unilaterally; for expiratory abdominal compression, the area directly above the navel was compressed. Tidal volume values were the actual measured values divided by body weight. [Results] Tidal volume values were as follows: at rest, 7.2 ± 1.7 mL/kg; during expiratory rib cage compression, 8.3 ± 2.1 mL/kg; during expiratory abdominal compression, 9.1 ± 2.2 mL/kg. There was a significant difference between the tidal volume during expiratory abdominal compression and that at rest. The tidal volume in expiratory rib cage compression was strongly correlated with that in expiratory abdominal compression. [Conclusion] These results indicate that expiratory abdominal compression may be an effective alternative to the manual breathing assist procedure.