FORCED OSCILLATION TECHNIQUE FOR THE EVALUATION OF SEVERE SLEEP-APNEAHYPOPNEA SYNDROME - A PILOT-STUDY

The forced oscillation technique (FOT) is a noninvasive method of pote ntial clinical interest for quantitatively assessing airway mechanics during sleep, We investigated the applicability of FOT as a diagnostic tool for noninvasive assessment of airflow obstruction in patients wi th sleep apnoea/hypopnoea syndrome (SAHS) during sleep. In seven patie nts previously diagnosed with severe SAHS (mean+/-SD apnoea/ hypopnoea index (AHI) 67+/-14) we performed a full polysomnography (PSG) togeth er with on-line measurement of respiratory impedance (\Z\) using FOT, For each patient me determined: 1) number of respiratory events conven tionally detected by full PSG, those obtained by FOT and their degree of concordance; and 2) the characteristics and values of \Z\ during th e respiratory events. FOT was well tolerated and easily applied in con junction with a conventional sleep setup. The mean number of respirato ry events.h(-1) detected by PSG and FOT were 55+/-16 and 58+/-17, resp ectively, with a strong Concordance, \Z\ increased from a baseline of 11+/-4 to 50+/-20 cmH(2)O . L-1. s during apnoea (mean+/-SD). In all b ut one patient intermittent increases of \Z\ occurred immediately befo re each obstructive apnoea, In four patients, the increases of \Z\ dev eloped at end-expiration whereas in two others occurred during inspira tion. During hypopnoea most of the patients showed decreases of \2\ du ring expiration, In conclusion, forced oscillation technique can be us ed as a noninvasive and complementary tool for the diagnosis of respir atory events and provides an on-line quantitative approach for continu ous monitoring of airflow obstruction during sleep in patients with sl eep apnoea/hypopnoea syndrome.