Alterations in diaphragmatic activity preceding and during intermittent hypoxaemia events in preterm infants

Objective: To assess the activity of the diaphragm using electromyography (dEMG) prior and during apnoea-induced intermittent hypoxaemia (IH) events in preterm infants

Design: A single-centre observational study.

Setting: Neonatal intensive care unit. 

Patients: Preterm infants (<32 weeks of gestation) experiencing IH events with a frequency of >1/hour

Methods: Heart rate, oxygen saturation (SpO 2) and dEMG were measured for 24 hours. dEMG data were processed for all IH events resulting in a SpO 2 <80%. Events were scored by two reviewers as central, obstructive or mixed. Subsequently, minimum (dEMG min) and maximum (dEMG max) diaphragmatic activity were calculated in three time periods (5-1 min prior, 1 min prior and during the desaturation) for each event. The dEMG activity over time was also compared between the different apnoea types.

Results: 20 infants (gestational age 27.6±1.3 weeks) were included. A total of 591 IH events were used for analysis of which 88 (14.9%), 239 (40.4%) and 264 (44.7%) were scored as central, obstructive and mixed, respectively. In the 1 min before the actual IH, dEMG max and dEMG min dropped for central and increased for obstructive events. Central and obstructive events also differed during the actual event (dEMG min 6.1 vs 8.4 μV and dEMG max 9.4 vs 13.3 μV, both p<0.001 for central vs obstructive events). Mixed events did not show a distinct dEMG pattern.

Conclusion: dEMG can detect and characterise central and obstructive apnoea before the IH event occurs, which supports development of automated detection and classification of apnoea events.