Introduction: In patients with sleep apnea (SA) monitoring of respiratory effort (RE) is a challenging task especially for hypopnea characterization. The gold standard is esophageal manometry (Pes) but it?s rarely done in clinical practice. In order to investigate less-intrusive RE measures the ratio of the inspiratory and expiratory energy (Ei/Ee) from breathing sounds (BS) was studied.

Methods: N=20 (f=7, m=13) SA patients (mean age 50 ± 13 years) underwent polysomnography (PSG) including Pes measurement as reference RE measure. In addition, BS were recorded in parallel using the PneaVoX sensor (Cidelec, France). Ei/Ee calculation was done by signal processing of BS recordings. Following standard AASM sleep scoring and detection of respiratory events visual characterization of hypopneas accompanied with a progressive RE increase (REI) or without was performed ones using just Pes and ones using just Ei/Ee.

Results: Patients had a mean AHI of 31 ± 30 /h and a mean HI of 11 ± 12 /h. Pes reference scoring revealed n=981 hypopneas to be accompanied with REI and n=299 to be without. Using the Ei/Ee, 80 % of the hypopneas were consistently characterized. Sensitivity, specificity, positive predictive value and negative predictive value for the detection of REI using Ei/Ee were 89 %, 50 %, 85 %, and 57 % respectively.

Conclusions: Results reveal that monitoring of REI during hypopneas using Ei/Ee from PneaVoX sensor have a high concordance with those from Pes readings. It seems that PneaVoX sensor could help to identify obstructive hypopneas in patients with SA and potentially in the future become a less-obtrusive tool in clinical practice.