RT Journal Article
SR Electronic
T1 Effect of sustained hypoxia on diaphragm length
JF European Respiratory Journal
JO Eur Respir J
FD European Respiratory Society
SP P1528
VO 44
IS Suppl 58
A1 Michael Ji
A1 Masato Katagiri
A1 Jenny Jagers
A1 Paul Easton
YR 2014
UL http://erj.ersjournals.com/content/44/Suppl_58/P1528.abstract
AB Introduction: Classic studies suggest an increase in resting end-expiratory lung volume (FRC) with hypoxia. Therefore, hypoxic increases in FRC have been purported to cause decreased resting length of the diaphragm. To date, diaphragm end-expiratory resting baseline length (LBL) during hypoxia has not been directly measured in any awake intact mammals.Methods: 18 days after implantation of sonomicrometers in the costal (COS) diaphragm in canines, we measured awake airflow, SpO2, ETCO2, and COS length during room air breathing then 25 min sustained isocapnic hypoxia (mean 79.5% SpO2). We report: 5 min room air (BASE), sustained hypoxia: first 3 min (PEAK) and final 5 min (PLATEAU), and then 5 min room air (RECOVERY) for breathing pattern and LBL.Results: For N=8 (mean 29.5kg), minute ventilation and tidal volume increased significantly from BASE to PEAK, then decreased to PLATEAU (p<0.01). Concurrently, LBL remained virtually unchanged from BASE to PEAK, however, with PLATEAU LBL decreased significantly (p<0.01). With RECOVERY, COS LBL remained significantly decreased compared to BASE (p<0.05).Conclusion: Hypoxia induced a significant decrease in diaphragm end-expiratory length. However, changes in diaphragm length occurred only when hypoxia was sustained, not during acute hypoxia. This may impact the force output of a contracting diaphragm in vivo during respiratory failure.