The role of nocturnal oximetry in obstructive sleep apnoea-hypopnoea syndrome screening*
Celestina Ventura1
Ana Sofia Oliveira2
Rita Dias3
Joana Teixeira3
Cristina Canhão3
Odete Santos4
Paula Pinto5
]]> Cristina Bárbara6
Resumo
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%), p<0,001. A fim de avaliar a sensibilidade, a especificidade, o VPP e o VPN, utilizámos dois pontos de corte baseados na gravidade da dessaturação. Com o primeiro ponto de corte considerámos positivos para o diagnóstico da SAHOS todos os doentes que apresentassem valores de dessaturação (saturação de O2 < 90%) ¡Ý a 1% do TTS, tendo-se obtido para a ON uma sensibilidade de 76,6%, uma especificidade de 75%, um VPP de 90% e um VPN negativo de 52,2%. Utilizando o segundo ponto de corte, foram considerados positivos todos os doentes que apresentassem valores de dessaturação ¡Ý a 5% do TTS, tendo-se obtido uma sensibilidade de 65,9%, uma especificidade de 100%, um VPP de 100% e um VPN de 50%.
Conclusões: A ON é um bom teste de screening diagnóstico da SAHOS, desde que seja excluída patologia respiratória.
Palavras-chave: Síndroma de apneia/hipopneia obstrutiva do sono, oximetria nocturna
]]> Abstract
Aim: 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.
Key-words: Obstructive sleep apnoea hypopnoea syndrome, nocturnal oximetry
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1 Assistente Graduada de Medicina Familiar, Centro de Saúde de Grândola. / General Practice Specialist Consultant, Grândola Health Centre.
2 Interna do Internato Complementar de Pneumologia do Hospital de Pulido Valente. / Pulmonology Resident, Hospital Pulido Valente.
3 Técnica de Cardiopneumologia do Hospital de Pulido Valente. / Cardiopulmonology Technician, Hospital Pulido Valente.
4 Assistente Hospitalar Graduada do Hospital de Pulido Valente. / Specialist Consultant, Hospital Pulido Valente.
5 Assistente Hospitalar de Pneumologia do Hospital de Pulido Valente. Assistente Convidada de Pneumologia da Faculdade de Ciências Médicas da Universidade Nova de Lisboa. / Pulmonology Consultant, Hospital Pulido Valente. Guest Pulmonolgy Consultant, Nova University School of Medical Sciences.
6 Coordenadora da Unidade de Fisiopatologia Respiratória do Hospital de Pulido Valente. Professora Auxiliar de Pneumologia da Faculdade de Ciências Médicas da Universidade Nova de Lisboa. / Coordinator, Respiratory Physiopathology Unit, Hospital Pulido Valente. Assistant Pulmonology Professor, Nova University School of Medical Sciences.
]]> * Estudo efectuado no âmbito de um mestrado em Patologia Respiratória da Faculdade de Ciências Médicas de Lisboa. / Study undertaken as part of an MSc in Respiratory Pathology, Lisbon University School of Medical Sciences.
Recebido para publicação/received for publication: 07.01.06
Aceite para publicação/accepted for publication: 07.02.22
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