A COMPARISON OF RESUSCITATION TECHNIQUES IN PREMATURE LAMBS
Probyn ME1, Hooper SB1, Dargaville PA2, Mc Callion N3, Harding R1, & Morley CJ3
1
Department of Physiology, Monash University, Melbourne; 2Department of Neonatology, Royal
Children’s Hospital, Melbourne; 3Neonatal Services, Royal Women’s Hospital, Melbourne.
E-mail: megan.probyn@med.monash.edu.au
Introduction: Preterm infants (<30 weeks) are at increased risk of developing respiratory distress
syndrome (RDS) and chronic lung disease (CLD) as they have immature lungs that are surfactant
deficient, incompliant and liquid-filled. RDS and CLD result from an acute inflammatory response
within the lung and it is now evident that the inflammatory reaction is due to tissue injury caused by
artificial ventilation. As the lung damage may be caused by just a few large breaths, it is possible
that the lung damage is initiated during the resuscitation period. Preterm human infants are
commonly resuscitated using a resuscitation bag that delivers variable tidal volumes and airway
pressures in the absence of a positive end expiratory pressure (PEEP). Our overall goal is to
compare the lung tissue damage caused by the resuscitation of premature lambs using either a
neonatal resuscitation bag (BR) or a mechanical ventilator set in volume guarantee (VG) mode.
The aim of this study was to determine the tidal volumes (VT) and peak inspiratory pressures (PIP)
achieved when resuscitating premature lambs using these different methods of resuscitation.
Methods: At ~126 days of gestation (term is ~147 days), anaesthetised pregnant ewes underwent
Caesarian section for fetal intubation and carotid artery and jugular vein catheterisation. The
lambs were then delivered and resuscitated for 15 minutes. Lambs were resuscitated using either
a “Laerdal” neonatal resuscitation bag (BR; n=7), which administered 100% oxygen, or the “Drager
Babylog 8000+” mechanical ventilator set in volume guarantee mode. In VG mode, the ventilator
administered a tidal volume of either 5ml/kg (n=4) or 10ml/kg (n=3) and all respiratory parameters
were recorded electronically.
Results: In all lambs, ~97% oxygen saturation (SaO2) was achieved within the first 5min of
resuscitation. In BR lambs, the range of pressures (12 - 68 cmH2O) and volumes (1.4 -15.4 ml/kg)
delivered were much greater than in the lambs resuscitated using either 5ml/kg (30 - 48 cmH2O
and 3.2 - 7.7 ml/kg) or 10ml/kg (34 - 57 cmH2O and 7.2 - 10.4 ml/kg - see figures).
Bag resuscitation
Pressure (cm H2O)
120
5ml/kg VG
120
80
80
80
40
40
40
0
0
3
6
9
12
15
0
3
Time (min)
VTE (ml/kg body wt)
6
9
12
15
3
Time (min)
Bag resuscitation
20
5ml/kg VG
20
16
12
12
12
8
8
8
4
4
4
0
6
9
12
Time (min)
15
9
12
15
10ml/kg VG
20
16
0
6
Time (min)
16
3
10ml/kg VG
120
0
3
6
9
12
Time (min)
15
3
6
9
12
15
Time (min)
Conclusion: The results of this study demonstrate that resuscitation of premature lambs with a
mechanical ventilator in VG mode is effective and delivers more consistent tidal volumes within a
narrower and more favourable range of mean airway pressures. We hypothesize that resuscitation
using a mechanical ventilator in VG mode will induce considerably less tissue damage within the
lung.