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147 Loss of End-Expiratory Lung Volume During Periods of Hypopnoea in Preterm Infants with Early Respiratory Distress Syndrome (RDS) Receiving CPAP
  1. R Bhatia1,2,
  2. PG Davis1,2,3,
  3. DG Tingay1,2,4
  1. 1Newborn Research, The Royal Women’s Hospital, Parkville
  2. 2Neonatal Research, Murdoch Children’s Research Institute
  3. 3Department of Obstetrics and Gynaecology
  4. 4Department of Paediatrics, University of Melbourne, Melbourne, VIC, Australia

Abstract

Background and aims Whether variations in end-expiratory lung volume (EELV) occur in stable infants receiving nasal CPAP is unknown. This study aimed to describe global and regional volumetric behavior over periods of hypopnoea (< 20 breaths/min over 15-secs) in preterm infants < 18 hours of age receiving nasal CPAP.

Methods Twenty infants < 32 weeks’ receiving CPAP were studied whilst supine. Clinicians set CPAP level at mean(SD) 6(1)cmH2O in FiO2 0.25(0.03). Relative ΔEELV and tidal volume (V T) [respiratory inductive plethysmography] ] and regional ΔEELV [electrical impedance tomography] were measured. 20-secs of data were analysed preceding and following episodes of hypopnoea and ΔEELV and ΔV T determined (expressed as average V T units at baseline). Breath-to-breath phase angles (Θ) and labored breathing index (LBI) were calculated post-hoc.

Results Ten episodes of hypopnoea lasting mean(SD) 26(11)s were analyzed in 10 infants mean(SD) GA 29(1) weeks and BW 1119 (264)g. EELV and V T fell significantly from baseline by median(range) 0.3(–1.1, 0.5) and 0.2 (0.3)V T units(p<0.05) during episodes of hypopnoea. Both non-dependant and dependant halves of the chest contributed equally to global loss in EELV during hypopnoea. During recovery, the non-dependant hemi-thorax recovered median (range)70 (9,100)% and dependant 63 (4,100)% of the loss of EELV in those regions respectively. No changes were seen in HR, oxygen saturations, FiO2, LBI and thoraco-abdominal asynchrony during these episodes.

Abstract 147 Table 1

Conclusions A significant loss in EELV may occur during hypopneic phases of respiration in infants considered stable on CPAP. Further work is needed to determine the significance of these observations.

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