COMPARISON OF PARTIALLY ATTENDED NIGHT TIME RESPIRATORY RECORDINGS AND FULL POLYSOMNOGRAPHY IN PATIENTS WITH SUSPECTED SLEEP APNOEA HYPOPNOEA SYNDROME/

Background - Laboratory full polysomnography (PSG) is considered to be the gold standard for the diagnosis of the sleep apnoea/hypopnoea syn drome (SAHS), but it is expensive and time consuming. A study was unde rtaken to evaluate the diagnostic usefulness of partially attended nig ht time respiratory recording (NTRR) and a clinical questionnaire in p atients with suspected SAHS in comparison with full PSG. Methods - Sev enty six patients (54 men) of mean (SD) age 51 (11.5) gears with a bod y mass index of 31 (5.7) kg/m(2) were studied at random on two differe nt nights with full PSG at the sleep laboratory and with NTRR on a res piratory ward. NTRR records oximetry, airflow, chest and abdominal mot ion. All signals were continuously displayed on a computer screen thro ughout the night and respiratory events were scored automatically the following morning. All patients completed a clinical questionnaire. Re sults - Mean values of the apnoea/hypopnoea index (AHI) using NTRR wer e lower than those obtained with full PSG (22.7 (2.4) versus 32.2 (3) events/hour) which was mainly due to underrecognition of hypopnoeas. S ensitivity and specificity of NTRR for the diagnosis of SAHS were 82% and 90%, respectively, taking as reference AHI >10 on full. PSG (AHI-P SG >10). The mean (+/-2SD) difference in AHI between the two methods w as 9.6 (range -5.4-24.6) (95% confidence interval 6.2 to 13). Symptoms of witnessed apnoeas, impotence, the overall clinical impression of a trained physician, and a neck size over 40 cm were significantly more prevalent in patients with AHI-PSG of >10, but impotence was the only clinical feature significantly more prevalent in patients with false negative compared with true negative NTRR results that helped to disti nguish patients with NTRR <10 but AHI-PSG >10. Conclusions - NTRR is a helpful and easy complementary diagnostic tool in clinical practice b ecause it detects patients with moderate to severe SAHS reasonably wel l and therefore can be useful for confirming a diagnosis of SAHS and a lso for treatment decisions. It is suggested that patients with suspic ion of SAHS should be initially studied by NTRR. When NTRR is negative , a full PSG should be performed if witnessed apnoeas, impotence, syst emic hypertension, ischaemic heart disease, and a trained physician's clinical impression of SAHS are present.