Increasing background inspiratory resistance changes somatosensory sensations in healthy man.

The central purpose of the study was to investigate if increasing background inspiratory resistance, a circumstance which activated afferents from the lungs and respiratory muscles, modified somatosensory and/or auditory sensations in healthy individuals. Estimation of mechanical stimulations applied on the middle finger (somatosensory sensation) and unilateral sound-pressure stimulations (auditory sensation) was based on the computation of Stevens' power function psi = k.phi n, where psi is the estimate and phi is either the somatosensory stimuli or sound-pressures. This was studied during eupnoeic unloaded ventilation then during a 10-min period of loaded breathing followed by a 10-min recovery period. Loaded breathing significantly lowered the estimate of somatosensory stimuli (decreased n coefficient). This effect persisted during the two first minutes of recovery period. By contrast, loaded breathing did not modify the perception of auditory stimulus. As somesthetic and respiratory afferents, but not auditory afferents, project on the same area in the sensory cortex we suggest the existence of central interactions which could explain observations of the difficulties to execute accurate tasks in patients suffering from obstructive lung disease independently from the alterations in their arterial blood gases.