Effects of Expiratory Rib Cage Compression and/or Prone Position on Oxygenation and Ventilation in Mechanically Ventilated Rabbits with Induced Atelectasis

INTRODUCTION: Expiratory rib cage compression is a chest physiotherapy technique known as “squeezing” technique in Japan. It has been claimed that rib cage compression effectively treats and/or prevents lung collapse, but no studies have been reported on rib cage compression focused on improving ventilation and/or oxygenation in subjects with collapsed lung. Therefore, we studied whether rib cage compression, with and without prone positioning, improves the ratio of P_aO2 to fraction of inspired oxygen (P_aO2/F_IO2), P_aCO2, or dynamic compliance of the respiratory system.

METHODS: We used anesthetized adult rabbits with induced atelectasis. An endotracheal tube and an 18-gauge catheter were placed into the airway via a tracheostoma, and pressure-controlled mechanical ventilation was used. To create atelectasis, artificial mucus was infused into the airway via the catheter. The rabbits were randomly assigned to one of 4 groups (n = 10 in each group): (1) supine without rib cage compression, (2) supine with rib cage compression, (3) prone without rib cage compression, and (4) prone with rib cage compression. Each rib cage compression session lasted for 5 min and was repeated 5 times every 30 min. After these interventions for 180 min all animals were placed in the supine position for 120 min.

RESULTS: The prone-position groups had significantly higher P_aO2/F_IO2 than the supine-position groups at 60 min after the beginning of the intervention, and at 60, 90, and 120 min after the end of the intervention (p < 0.05). Rib cage compression did not significantly affect P_aO2/F_IO2, P_aO2, or dynamic compliance.

CONCLUSIONS: It is unlikely that rib cage compression re-expands collapsed lung. Prone positioning improved oxygenation in rabbits with induced atelectasis.