[Utility of portable monitoring device with airflow, oxygen saturation and respiratory effort in the diagnosis of sleep apnea hypopnea syndrome]

OBJECTIVE: To validate the values of monitoring airflow, oxygen saturation and respiratory effort in the diagnosis of sleep apnea-hypopnea syndrome (SAHS).

METHODS: A total of 70 subjects with suspected SAHS underwent the tests of polysomnography (PSG) and portable monitoring device (PMD) separately at our sleep lab. The portable monitoring device recorded nasal airflow, oxygen saturation and respiratory effort. Apnea-hypopnea index (AHI) or respiratory disturbed index (RDI), lowest oxygen saturation (LSaO2), oxygen desaturation index (ODI4) and percentage of different types of sleep breathing events (central/obstructive/mixed hypopnea) accounting for the total numbers of sleep disordered breathing were also analyzed. The data of AHI and ODI4 showed skew distribution undergoing log transformation to approximate to normal distribution. Pair t test was used for the comparisons of different parameters. The agreement between two methods was analyzed by Bland-Altman plot.

RESULTS: Fifty-eight subjects were diagnosed as SAHS with an AHI (RDI) over 5 on PSG. The sensitivity and specificity of portable monitoring device were 94.8% and 75.0% respectively. The mean AHI derived from PSG and RDI derived from PMD were (27 ± 25) and (29 ± 27) times per hour respectively and those after log transformation were (1.2 ± 0.5) and (1. 2 ± 0.5) times per hour (P = 0.411). The mean ODI4 derived from PSG and PMD were (23 ± 25) and (21 ± 24) and those after log transformation (0.9 ± 0.7) and (1.1 ± 0.5) times per hour respectively (P = 0.042). The mean values of LSaO2 were 79% ± 13% and 79% ± 12% respectively (P = 0.550). No significant differences existed between AHI derived from PSG and RDI derived from PMD. Bland-Altman plot also showed a high agreement between AHI derived from PSG and RDI derived from PMD. PMD could also identify major part of different events so as to aid clinical decision-making.

CONCLUSION: Portable monitoring device recording airflow, oxygen saturation and respiratory effort shows a great agreement with PSG with regards to AHI (RDI) and the identification of different types of respiratory events.