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


CONCLUSIONS
Routinely maintained longer expiratory than inspiratory times during high frequency oscillation should be discouraged.
Dimitriou
G
G
Department of Paediatrics, United Medical and Dental Schools, St Thomas' Hospital, London, UK.
Greenough
A
A
Kavvadia
V
V
Milner
A D
AD
D002245:Carbon Dioxide / Q000032:analysis; D006612:High-Frequency Ventilation / Q000379:methods*; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D010100:Oxygen / Q000097:blood; D011312:Pressure; D011659:Pulmonary Gas Exchange; D012119:Respiration; D012127:Respiratory Distress Syndrome, Newborn / Q000503:physiopathology / Q000628:therapy*
D002245:Carbon Dioxide; D010100:Oxygen