Tonic diaphragmatic activity in critically ill children with and without ventilatory support

Area of Science:

• Pediatric critical care medicine
• Respiratory physiology

Background:

• Infants require active maintenance of end-expiratory lung volume (EELV).
• Mechanically ventilated infants exhibit diaphragmatic tonic activity (DTA) for EELV maintenance.
• The role of DTA in compensating for laryngeal braking loss post-intubation is unclear.

Purpose of the Study:

• To investigate the persistence of DTA post-extubation in infants.
• To determine if DTA is observable in older children.

Main Methods:

• Prospective observational study of pediatric patients ventilated for over 24 hours.
• Recorded diaphragm electrical activity (EAdi) using a nasogastric catheter.
• Measured tonic EAdi as EAdi in the final quartile of expiration across four phases: acute, pre-extubation, post-extubation, and PICU discharge.

Main Results:

• In infants (<1 year), tonic EAdi was consistently present, averaging 33% of inspiratory EAdi at PICU discharge.
• No significant changes in tonic EAdi were noted between pre- and post-extubation periods in infants.
• In older children, tonic EAdi was generally negligible, though 10 showed significant activity at some point; bronchiolitis was the sole independent predictor of tonic EAdi.

Conclusions:

• Infants maintain tonic EAdi post-extubation, indicating its continued role in ventilatory control despite restored laryngeal braking.
• Tonic EAdi may have a pathophysiological role in bronchiolitis and can be reactivated in older children.
• Further research is needed to evaluate the utility of tonic EAdi in titrating mechanical ventilation.