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Are maximal inspiratory and expiratory pressures useful in the screening of obstructive sleep apnea?


Obstructive sleep apnea (OSA) is characterized by repetitive collapse of the upper airway during sleep. Respiratory muscle strength can be assessed by measuring the maximal inspiratory pressure (MIP) and the maximal expiratory pressure (MEP). During the apnea, the obstructed airway and the subsequent asphyxia lead to increased inspiratory efforts and, hence, to overload of inspiratory muscles. The chronic overload of the diaphragm place OSA subjects at risk of inspiratory muscle fatigue. However, whether diaphragm fatigue actually occurs in OSA patients is still controversial.


Obstructive sleep apnea (OSA) generates intense ventilatory effort which may cause either muscle fatigue or muscle force enhancement. The present study aimed to verify whether measurements of MIP and MEP are associated with the presence of OSA, being useful in OSA screening.


Patients undergoing full-night in-laboratory polysomnography were invited to measure MIP and MEP before the sleep study. Percentage of predicted MIP and MEP values were calculated and both increased (>120% of predicted) or reduced (<80% of predicted) MIP and MEP were considered as potential markers of OSA. The diagnostic performance was expressed as area under the ROC curve, sensitivity, specificity, predictive values and odds ratio in univariate analyses and in adjusted models.


We performed measurements in 246 persons. The percentage of predicted MIP and MEP measurements was calculated. The accuracies of percentage of predicted MIP and MEP to detect AHI>5, 15, and 30 were only marginally significant. Percentage of predicted MEP above 120% (MEP>120% of predicted) was a significant threshold for OSA risk, with sensitivity of 61%, specificity of 43% and accuracy of 59% to identify AHI>30. Adjusted odds ratio of MEP>120% of predicted to identify risk of severe OSA was 2.1 (95% confidence interval 1.1-3.9).


This study shows that OSA severity is associated with MEP above 120% of predicted. The usefulness of this measurement in office OSA screening is limited by its accuracy being similar to that of questionnaires.


sleep apnea; inspiratory pressure; expiratory pressure.


Área Clínica


Hospital de Clínicas de Porto Alegre - Rio Grande do Sul - Brasil, Universidade Federal do Rio Grande do Sul - Rio Grande do Sul - Brasil


Chaiane Facco Piccin, Marcia Kraide Fischer, Juliana Heitich Brendler, Jhoana Mercedes Uribe, Juliana Langendorf da Costa Vieira, Bruno de Brito Lopes, Kelly Silveira da Silva Bueno, Denis Martinez