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Eur J Pediatr. 1999 Oct;158(10):796-9.

Comparison of two inspiratory: expiratory ratios during high frequency oscillation.

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Department of Paediatrics, United Medical and Dental Schools, St Thomas' Hospital, London, UK.


The aim of this study was to compare gas exchange and volume delivery during high frequency oscillation at two frequently used inspiratory:expiratory (I:E) ratios: 1:2 and 1:1, other oscillatory settings being kept constant. A group of 13 infants with respiratory distress syndrome, median gestational age 28 weeks (range 23-36) and postnatal age 1 day (range 1-8) were studied. At the I:E ratio of 1:1 compared to 1:2 the median paCO(2) was lower, P < 0.05 (30 mmHg, range 22-47 vs 34 mmHg, range 27-46) and the volume delivered higher, P < 0.01 (2.6 ml/kg, range 1.2-5.6 vs 2.0 ml/kg, range 1.0-3.9). There was no significant difference in oxygenation levels at the two I:E ratios. In a related in vitro study, changing the I:E ratio from 1:2 to 1:1 increased the mean airway pressure by a median of 8.6% (range 2.9-28.1%).


Routinely maintained longer expiratory than inspiratory times during high frequency oscillation should be discouraged.

[Indexed for MEDLINE]

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