High and conventional rates of positive pressure ventilation.

We compared high frequency positive pressure ventilation with conventional rate ventilation in 23 preterm infants with the idiopathic respiratory distress syndrome. Nine infants (10 studies) were making spontaneous respiratory efforts during conventional ventilation that abated at 100 breaths per minute. Six of these showed an increase in TcPo2 of at least 10% at the higher rate (mean 18.5%). Two babies showed no change during high frequency positive pressure ventilation, and in one baby (the largest) the TcPo2 fell. Eight infants were apnoeic at both ventilator rates: five suffered a fall in TcPo2 of at least 10% at 100 breaths per minute (mean 19%) and three were unchanged. A further six infants (seven studies) would not tolerate a reduction in rate from 100 breaths per minute without an increase in FIO2. Failure to tolerate a conventional ventilator rate in these circumstances seemed related to the onset or a noticeable increase in spontaneous respiratory efforts.