EFFECTS OF INSPIRATORY AND EXPIRATORY POSITIVE PRESSURE DIFFERENCE ONAIR-FLOW DYNAMICS DURING SLEEP

We measured the effects of dissociating inspiratory and expiratory pos itive pressure (Pr and PE, respectively) on the inspiratory flow limit ation pattern and on genioglossus (GG) activity in nine sleep apnea pa tients. Measurements were made at two different levels of PI with step wise increases in PE. Flow-limited breaths were observed during each r ecording session. In six of nine subjects, maximal inspiratory flow (( V) over dot I-max) was correlated with the difference between Pr and P E (correlations were negative ill 5 subjects, positive in 1 subject). In three other patients, (V) over dot I-max was not influenced by the amount of pressure difference. A positive relationship between tonic a nd/or phasic GG electromyographic activities and PI-PE difference was observed at least at one PI level in all patients. This correlation wa s observed independently of the presence or absence of any relationshi p between (V) over dot I-max and the amount of pressure difference. Ou r results suggest that increasing the PI-PE difference (i.e., decreasi ng PE) may be associated with a significant worsening in inspiratory f low limitation and that the (V) over dot I-max-pressure difference beh avior is not dependent on the GG electromyographic-pressure response.