Relationship between mouth occlusion pressure and electrical activity of the diaphragm: effects of flow-resistive loading.
We determined the relationship between mouth occlusion pressure and diaphragmatic electromyography during CO2 rebreathing with and without inspiratory flow resistance. Diaphragmatic electromyography was measured as a moving time average; occlusion pressures were measured 150 msec after onset of an inspiratory effort against a closed airway (P.15). P.15 versus diaphragmatic electromyographic plots during CO2 rebreathing with and without inspiratory flow resistance were linear. In 3 subjects the slope of P.15 versus diaphragmatic electromyography was unchanged with inspiratory flow resistance whereas in 3 others the slope increased, indicating greater inspiratory force for a given degree of diaphragmatic activity. We concluded that under unloaded conditions P.15 is a reliable index of respiratory neural output but may no longer reflect only inspiratory motoneuron drive during mechanical loading.
D002245:Carbon Dioxide; D003964:Diaphragm / Q000502:physiology*; D004576:Electromyography; D006801:Humans; D008297:Male; D009055:Mouth / Q000502:physiology; D010791:Phrenic Nerve / Q000502:physiology; D011312:Pressure; D012123:Pulmonary Ventilation
D002245:Carbon Dioxide