Expiratory timing in obstructive sleep apnoeas.
Diaphragmatic electromyogram was recorded during NREM sleep in 4 patients affected by obstructive sleep apnoea (OSA) syndrome in order to evaluate the behaviour of expiratory time (TE) in the course of the obstructive apnoea-ventilation cycle. The two components of TE, i.e. time of post-inspiratory inspiratory activity (TPIIA) and time of expiratory phase 2 (TE2) were separately analysed. TPIIA showed a short duration, with only minor variations, within the apnoea, while its duration was more variable and longer in the interapnoeic periods: the longest TPIIA values were associated with the highest inspiratory volumes in the same breaths. This behaviour seemed regulated according to the need of a more or less effective expiratory flow braking, probably as a result of pulmonary stretch receptors discharge. Conversely TE2 showed a continuous gradual modulation, progressively increasing in the pre-apnoeic period, decreasing during the apnoea and increasing in the post-apnoeic period: these TE2 variations seemed related to oscillations in chemical drive. These data show that TE in the obstructive apnoea-ventilation cycle results from a different modulation in its two components and suggest that both mechanical and chemical influences play a role in its overall duration.
Cibella
F
F
Istituto di Fisiopatologia Respiratoria del C.N.R. Palermo, Italy.
Marrone
O
O
Sanci
S
S
Bellia
V
V
Bonsignore
G
G
D000328:Adult; D000402:Airway Obstruction / Q000503:physiopathology*; D003964:Diaphragm; D004576:Electromyography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012018:Reflex / Q000502:physiology; D012891:Sleep Apnea Syndromes / Q000503:physiopathology*; D013997:Time Factors; D014939:Work of Breathing / Q000502:physiology*