Influence of water immersion on the airway impedance measured by forced oscillation technique.

INTRODUCTION: Few studies have examined the influence of different water depths on the airway impedance measured by forced oscillation technique in healthy adults. METHODS: Eleven healthy men (23.2 ± 1.5 years old) participated in this study. We measured the respiratory impedance assessed with the resistance at frequency of 5 Hz and 20 Hz, the reactance at frequency of 5 Hz, and frequency of resonance. To compare the influence of water depths, we carried out one dryland (DL) and two water level conditions: clavicle level (CL) and xiphoid appendix level (XA). RESULTS: The respiratory resistance at frequency of 5 Hz was higher in CL and XA than DL, and at 20 Hz was significantly higher in CL than DL. The respiratory reactance at 5 Hz was lower in CL and XA than DL, and frequency of resonance was higher in CL and XA than DL. CONCLUSION: These results suggested that water immersion above xiphoid appendix level increase airway resistance.