TY - JOUR T1 - Aminophylline increases ventilation and crural diaphragm contractility in awake canines JF - European Respiratory Journal JO - Eur Respir J VL - 44 IS - Suppl 58 SP - P1797 AU - Jenny Jagers AU - Bruce Rothwell AU - Paul Easton Y1 - 2014/09/01 UR - http://erj.ersjournals.com/content/44/Suppl_58/P1797.abstract N2 - Aminophylline (Amino) is still used in treatment of COPD. However, effects of Amino on ventilation and respiratory muscles are uncertain. Previously, we examined the effects of Amino on costal diaphragm (Resp Phys, 2009 167:273-80). Since costal and crural diaphragm show differential function, structure and fiber type, we studied the effect of Amino on the crural diaphragm (CRU), by measurement of both length and moving average EMG. Sonomicrometry transducers and EMG electrodes were implanted in the left CRU. After recovery, the animals were studied awake, breathing through a mask recording airflow, ETCO2, heart rate, muscle length, and EMG during room air, and CO2 stimulation, before and after Amino. Results are shown at room air and 2 levels of CO2. For N=6 dogs (mean wt 29.8kg) studied after 25 days, minute ventilation, tidal volume, and respiratory frequency increased significantly with Amino, during resting breathing and all levels of CO2. Mean Amino was 72 umol/L (therapeutic range 55-110 umol/L). CRU shortening increased significantly with Amino while CRU EMG activity remained unchanged, consistent with increased contractility of the CRU with Amino. We conclude that, at clinical therapeutic doses of Aminophylline, crural diaphragm contractility is increased. ER -