Introduction Positional treatments have a long history of usage in obstructive sleep apnoea (OSA). Recent developments of more sophisticated therapies reported good response in patients with an AHI of <60 and predominately supine OSA (arbitrarily defined as total AHI: non-supine AHI ≥ 1.5).1,2 We hypothesised that patients with mild to moderate OSA usually have periods both with and without OSA, and that the OSA periods will be mainly due to supine OSA. Such patients might therefore be trialled on positional therapies without specific assessment of posture.
Methods Patients included had OSA and underwent an in-hospital respiratory sleep study between May- July 2016. Sleep studies included video review for identification of supine sleep. The oxygen desaturation index >4% (ODI) was recorded in supine and non-supine positions. The ratio of the total to non-supine ODI was calculated.
Results 40 patients’ sleep studies were suitable for analysis. 7 patients were excluded: 3 due to comorbidities (hypoventilation/CSA), 3 due to lack of supine sleep ( <30 minutes) and one due to having minimal OSA. Patients had a mean age of 53.8 years (SD 12.7) and mean BMI of 34.9 kg/m2 (SD 9.0). The median supine ODI was significantly higher than the median total ODI (supine ODI 54.3/h, IQR 47.9; total ODI 28.6/h, IQR 34.4; p < 0.001). There was a significant relationship between the ratio of total ODI to non-supine ODI versus the total ODI (Spearman’s rho = 0.37, p = 0.02; Figure 1).
Discussion Our data suggests that patients with lower ODIs are more likely to have supine predominant OSA. At ODI values over 40 it is very unlikely that there is a posturally dependant component to a patient’s OSA. However, the reverse is not the case; although many patients with low ODIs do have a postural component, many do not. It is therefore necessary to objectively assess the degree of supine predominant OSA in future trials of positional therapies, but patients with ODIs over 40 could be excluded at the outset.
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Levendowski DJ, et al. Capability of a neck worn device to measure sleep/wake, airway position, and differentiate benign snoring from obstructive sleep apnea. J Clin Monit Comput 2015;29:53–64.