Hypoventilation and apnea in children during mechanically assisted ventilation

Uncuffed tracheostomy tubes are used for long-term mechanical ventilation in children. However, upper airway mechanics differ between sleep and wakefulness; this may affect air leak around tracheostomies. We studied 19 children with high cervical spinal cord injury on portable positive pressure ventilators, age range birth to 19 years. Ventilator settings were adjusted while awake to achieve PaCO2 less than 45 mm Hg and PO2 greater than 90 mm Hg. Clinically several children with uncuffed tracheostomies became unstable at night with seizures and sleep disruption. Nine of 11 children on volume controlled systems were found to be inadequately ventilated during sleep. Substitution with a cuffed tracheostomy allowed adequate ventilation both awake and asleep, suggesting that inadequate ventilation during sleep was due to an uncompensated leak around the uncuffed tracheostomy. To avoid cuffed tracheostomies, eight children received pressure controlled ventilation. Gas exchange was adequate throughout the day and night. We conclude that children receiving volume controlled mechanical ventilation via uncuffed tracheostomy tubes can exhibit hypoventilation due to uncompensated air leak. Pressure controlled ventilation improves adequacy of gas exchange during sleep and wakefulness.