Poster Presentation & Flash Talk 46th Annual Meeting of the Fetal and Neonatal Physiological Society 2019

Increasing respiratory effort with 100% oxygen during resuscitation of preterm rabbits at birth (#101)

Janneke Dekker 1 2 , Stuart B Hooper 2 3 , Michelle K Croughan 4 , Kelly J Crossley 2 3 , Megan J Wallace 2 3 , Erin V McGillick 2 3 , Philip LJ DeKoninck 2 3 5 , Martha Thio 6 7 8 , Tessa Martherus 1 , Gary Ruben 4 , Charles C Roehr 9 10 , Sophie JE Cramer 1 11 , Andreas Flemmer 12 , Linda Croton 4 , Arjan B te Pas 1 , Marcus J Kitchen 4
  1. Neonatology, Leiden University Medical Center, Leiden, The Netherlands
  2. The Ritchie Centre, Hudson Institute of Medical Research, Clayton, VIC, Australia
  3. Obstetrics and Gynaecology, Monash University, Melbourne, VIC, Australia
  4. School of Physics and Astronomy, Monash University, Melbourne, VIC, Australia
  5. Obstetrics and Gynaecology, Erasmus MC, Rotterdam, The Netherlands
  6. Women’s Newborn Research Centre, The Royal Women’s Hospital, Melbourne, VIC, Australia
  7. Murdoch Children’s Research Institute, Royal Children's Hospital, Melbourne, VIC, Australia
  8. Department of Obstetrics and Gynaecology, University of Melbourne, Melbourne, VIC, Australia
  9. Newborn Services, John Radcliffe Hospital, Oxford, United Kingdom
  10. Pediatrics, University of Oxford, Oxford, United Kingdom
  11. Department of Instrumental Affairs, Leiden University Medical Center, Leiden, The Netherlands
  12. Department of Neonatology, Dr. v. Haunersches Kinderspital & Perinatal Center Grosshadern, Munich, Germany

Background:               Spontaneous breathing is essential for successful non-invasive respiratory support delivered by a facemask at birth. As hypoxia is a potent inhibitor of spontaneous breathing, initiating respiratory support with a high O2 concentration may reduce the risk of hypoxia and increase respiratory effort at birth.

Methods:                     Preterm rabbit kittens (29 days gestation, term ~32 days) were delivered and randomised to receive continuous positive airway pressure with either 21% (n=12) or 100% O2 (n=8) via a facemask. If apnea occurred, intermittent positive pressure ventilation (iPPV) was applied with either 21% or 100% O2 in kittens who started in 21% O2, and remained 100% O2 for kittens who started the experiment in 100% O2. Respiratory rate (breaths per minute, bpm) and respiratory rate coefficient of variation (COV, %) were measured from oesophageal pressure recordings and functional residual capacity (FRC) was measured from synchrotron phase-contrast X-ray images.

Results:                       Kittens receiving 21% O2 had a significantly lower respiratory rate and higher respiratory rate COV, indicating a less stable breathing pattern, at the start of the experiment compared to kittens starting in 100% O2 (median (IQR) COV (%): 33.30 (17.24–50.06) vs 27.54 (18.58–36.34), p=0.009; respiratory rate (bpm): 16 (4–28) vs 38 (29–46), p=0.001). Apnea, for which iPPV was required, was more frequently observed in kittens in whom resuscitation was started with 21% compared to 100% O2 (11/12 vs 1/8, p=0.001). After recovery from apnea, respiratory rate was significantly lower and respiratory rate COV significantly higher, indicating a less stable breathing pattern, in kittens who received iPPV with 21% (n=5) compared 100% O2 (n=6). FRC was not different between study groups at both timepoints.

Conclusion:                 Initiating resuscitation with 100% O2 resulted in increased respiratory activity, and greatly reduced the risk of apnea and the need for iPPV after birth.