AIRWAY AND BODY-SURFACE SENSORS FOR TRIGGERING IN NEONATAL VENTILATION

Failure of neonatal patient triggered ventilation may reflect a delay in delivery of flow relative to the inspiratory effort of the infant. Transmission of diaphragmatic contraction to the sensor site (patient delay) and further transmission to and within the sensing device (devi ce delay) both contribute to the delay in triggering. Patient and devi ce delays were studied for different sensing systems in 36 infants, 24 of whom were intubated. Device delay was long (>40 ms) with a convent ional apnoea monitor compared with sensors placed at the airway openin g (2 ms), the inspiratory (12 ms) and expiratory (3 ms) pressure trans ducers of the ventilator, the Graseby capsule (8 ms), strain gauges (3 ms) and oesophageal pressure (6 ms). In near normal infants, the sum of patient and device delays for the latter sensors was less than 20 m s and a minor component of the total delay. However, in severe lung di sease the total delay may be more than 100 ms even for airway sensors.