OBSTRUCTIVE SLEEP-APNEA SYNDROME - IS THE HALF-NIGHT POLYSOMNOGRAPHY AN ADEQUATE METHOD FOR EVALUATING SLEEP PROFILE AND RESPIRATORY EVENTS

Recently, to reduce the costs of polysomnography, split-night studies have been introduced into routine practice: the first part of the nigh t is used to make the diagnosis of obstructive sleep apnoea syndrome ( OSAS) and the second part to achieve an appropriate level of continuou s positive airway pressure, Since this split-night protocol has not ye t been validated by the comparison of polysomnographic pictures obtain ed in the first and second parts of the night, the aim of this study w as to evaluate sleep profile and respiratory disturbances in the first part (PSG1) and second (PSG2) portion of a standard full-night polyso mnographic examination (PSGtot) in a group of OSAS patients. Twenty ni ne consecutive OSAS patients, aged 54+/-10 yrs; body mass index (BMI) 40+/-6 kg.m(-2) (mean+/-SD values), were studied by separate analyses of PSG1, PSG2 and PSGtot, PSG1 was found to have a low sensitivity val ue (66%). A significant difference was found between apnoea-hypopnoea indices (AHI) recorded in PSG1, PSG2 and PSGtot (mean+/-SD, AHI1 33+/- 27, AHI2 45+/-28, AHItot 40+/-25 events.h(-1), respectively; p<0,01), A strong correlation was observed between AHItot and AHI1 (r=0,89) and between AHItot and AHI2 (r=0,92), but a weaker correlation between AH I1 and AHI2 (r=0,66), These correlations became weaker when patients w ere subdivided into two different classes on the basis of disease seve rity, PSG1 was representative of PSGtot and similar to PSG2 only in th ose patients with rapid eye movement (REM) phase sleep in the first pa rt of the night, We conclude that split-night protocols are not approp riate for evaluating sleep-disordered breathing in obstructive sleep a pnoea syndrome patients when rapid eye movement phase sleep does not o ccur in the first part of the night.