Revista Portuguesa de Pneumologia (Jul 2007)
Papel da oximetria nocturna no rastreio da síndroma de apneia-hipopneia obstrutiva do sono
Abstract
Objectivo: Foi objectivo deste estudo determinar a sensibilidade e a especificidade da oximetria nocturna (ON) como método de screening diagnóstico para a síndroma de apneia-hipopneia obstrutiva do sono (SAHOS), utilizando como método de referência a polissonografia (PSG) . Metodologia: Foram incluídos 63 doentes com suspeita clínica de SAHOS e exclusão de doença respiratória, sendo submetidos a uma PSG completa, incluindo ON. Posteriormente, foram determinados: a sensibilidade, a especificidade e os valores preditivos positivo (VPP) e negativo (VPN) da ON. Resultados: A SAHOS foi diagnosticada em 47 doentes com uma média etária de 54 anos. Verificaram-se diferenças significativas na avaliação da percentagem do tempo total de sono (TTS) com dessaturação de O2 abaixo de 90% entre doentes com SAHOS (25,4 29,7%) e sem SAHOS (1 ± 1,5%), pAim: The aim of our study was to evaluate the sensitivity and specificity of Nocturnal Oximetry (NO) as a diagnostic screening tool for obstructive sleep apnoea hypopnoea syndrome (OSAHS), compared with polysomnography (PSG) as the gold standard. Methodology: 63 patients with clinical suspicion of OSAHS and exclusion of respiratory disease underwent PSG and NO. We then determined NO sensitivity, specificity, positive (PPV) and negative predictive values (NPV). Results: OSAHS was diagnosed in 47 patients with a mean age of 54 years. In the evaluation of the percentage of Total Sleep Time (TST) with oxygen desaturation below 90%, we found significant differences between patients with OSAHS (25.4 ± 29.7%) and without OSAHS (1 ± 1.5%), p<0,001. We used two cutoff points to evaluate sensitivity, specificity, positive (PPV) and negative predictive values (NPV), based on the severity of O2 desaturation (StO2<90%). Using the first cutoff point we diagnosed with NO as positive all the patients with TST desaturation values ¡Ý1% of the TST. Under these circumstances we found a sensitivity of 76.6%, a specificity of 75%, a PPV of 90% and an NPV value of 52.2% for our screening test (NO). Using the second cutoff point, we diagnosed with NO as positive all the patients with TST desaturation values ¡Ý5% of the TST. With this method we found a sensitivity of 65.9%, a specificity of 100%, a PPV of 100% and an NPV of 50%. Conclusion: NO is a useful screening test for the diagnosis of OSAHS in patients without respiratory disease.
