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 (SpO₂) and dEMG were measured for 24 hours. dEMG data were processed for all IH events resulting in a SpO₂<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.