Relationship of transdiaphragmatic pressure and latencies for detecting added inspiratory loads

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Abstract
Changes in transdiaphragmatic pressure (Pdi) developed during graded elastic (E) and resistive (R) loaded breaths were measured and the emergence of such changes was correlated with the load-dependent alterations in latency for detection (Tdet). Five healthy adults were studied using 3 protocols, i.e., graded E, graded R and graded R in the presence of elevated background R. In each protocol, loads were added for single inspirations, 10 times in random order and separated by 3-5 unloaded breaths. Subjects pressed a signal marker as soon as loads were detected. Inspiratory flow (.ovrhdot.VI), inspired volume (VI) mouth pressure and Pdi of loaded breaths, and the preceding unloaded breaths were recorded and computer averaged. Patterns of .ovrhdot.VI and VI were not altered prior to detection of the smallest added E and R loads, but decreased with the higher loads. Group mean patterns of Pdi showed graded increases during loaded breaths. Augmentation of Pdi preceded Tdet and occurred earlier as Tdet decreased with graded E and R loads. Elevating the background R delayed both Tdet of added R and the augmentation of Pdi. Load-induced changes in diaphragmatic tension may play a sensory role in detection of inspiratory loads.