Chest wall electromyography: a surrogate for crural diaphragmatic electromyography during sleep apnoea hypopnea obstructive syndrome to assess respiratory effort

Chest surface EMG at diaphragmatic insertions (IC-EMG) is an alternative way for capturing respiratory effort (RE) during SAHOS.IC-EMG wasn9t investigated with regards to oesophageal crural diaphragmatic EMG (DI-EMG). Our study aimed to assess the similarity between IC and DI-EMG and the ability of IC-EMG to classify RE episodes. Methods 14 adults SAHOS underwent a lab-based PSG study with IC-EMG and DI-EMG. 70 periods of normal breathing (NB),309 RE events (including 135 RERA,70 OH and104 OA) were randomly selected for analysis in R-studio. After noise reduction, AUC and peak-to-peak distance (d) were calculated for both signals. Similarity between 2 signals was evaluated by cross-correlation as a function of the lag of one relative to the other. Correlation and d-value were compared among 4 groups of RE levels. Ability of each signal to detect RE was evaluated by multiclass CART algorithm. Results Patients have a mean age of 42.8±10.7 yrs and BMI of 31.1±8.6 kg/m2.Their averaged TST and AHI were 347±51.9 min and 35.3±25.1 n/h respectively. IC and DI-EMG signals are cross-correlated in either NB or RE events (r=0.6 to 0.86) by a lag of 0.5-0.9 second. AUC was also correlated (r=0.96). IC showed a significant difference in d-value among 4 groups (NB:14.6 vs RERA:21.9, OH:19.8 and OA:44.2). Using cut-offs at 17.8 and 31.5, IC distance allows classifying RERA, OAH and NB with accuracy, inter-class agreement and specificity of 0.8, 0.63 and 0.91, respectively. Conclusions IC-EMG is a useful method to assess RE and the obstructive nature of AH .