Exploring the relationship between respiratory muscle strength and the apnea-hypopnea index: A preliminary report

Abstract

<b>Aim:</b> The purpose of this study was to investigate whether the maximum inspiratory and expiratory pressure (MIP and MEP, accordingly) were associated with the apnea-hypopnea index (AHI) in patients with obstructive sleep apnea syndrome (OSAS). <b>Methods:</b> Fifty-two OSAS patients, comorbidity free, were divided into two severity strata (events/h: ≥15AHI&lt;30, n=28, vs. ΑΗΙ≥30, n=24). For each patient were recorded anthropometric characteristics, spirometry parameters, MIP, MEP and cardiopulmonary function (CPF) parameters in sitting position for 3 min. Differences between groups were assessed with the independent samples t-test; Correlations between variables were assessed with the Pearson’s R correlation coefficient. Data normality was assessed with the one sample Kolmogorov-Smirnov test; For all tests, a p-value &lt;0.05 was considered statistically significant. <b>Results:</b> Several differences were detected between the two groups (ΑΗΙ≥30 vs. ≥15AHI&lt;30): MIP (102.0±18.3 vs. 91.1±12.1 % of predicted, p&lt;0.05), CPF parameters tidal volume (0.8±0.2 vs. 0.7±0.1, L, p&lt;0.05), end-tidal CO2 (34.6±4.2 vs. 31.4±3.7, mmHg, p&lt;0.05) and mean arterial pressure (88.4±6.5 vs. 82.9±6.2, mmHg, p&lt;0.05). Significant correlations were detected between (a) MIP and AHI (r=.332, p&lt;0.05), (b) MIP and desaturation index (r=.439, p&lt;0.001) and (c) MEP and percentage of REM sleep stage (r=-.564, p&lt;0.001). <b>Conclusion:</b> Our findings outline a positive correlation between maximal inspiratory pressure the severity of AHI. Intermittent breath cessation during sleep could be a potential mechanism resulting in increased the inspiratory muscle strength.