Inspiration: two decoupled diaphragms

INTRODUCTION Although inspiratory airflow is generated primarily by the diaphragm, costal (COS) and crural (CRU) diaphragm have distinct neural-mechanical profiles and varying mechanical advantage. QUESTION Do COS and CRU make equivalent contributions to generation of inspiratory airflow? METHODS Data N=12 canines, from database completed in 2009, implanted with sonomicrometers and EMG electrodes into left COS and CRU. After recovery, while awake, airflow, muscle length and moving average EMG were recorded during room air and CO2 stimulation, analyzed breath by breath and expressed as percent of maximum at successive 5% "slices" of TTOT(%TTOT). RESULTS At room air, mechanical contributions of COS and CRU were significantly different (p<0.05), with COS progressively diverging to greater contribution than CRU (Figure 1). Peak EMG of COS and CRU did not occur at peak inspiratory airflow, but much later in inspiration. And the segments were asynchronous, with peak CRU EMG occurring consistently after COS (p<0.05) (Figure 2). CONCLUSIONS COS and CRU contributions to inspiratory airflow are significantly different, EMG activation is not in phase with inspiratory airflow, and segmental activity is asynchronous. <fig><object-id>erj;64/suppl_68/PA1664/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig> <fig><object-id>erj;64/suppl_68/PA1664/F2</object-id><object-id>F2</object-id><object-id>F2</object-id><graphic></graphic></fig>