Positive End Expiratory Pressure during Resuscitation of Premature Lambs Rapidly Improves Blood Gases without Adversely Affecting Arterial Pressure

Abstract

Positive end expiratory pressure (PEEP) is important for neonatal ventilation but is not considered in guidelines for resuscitation. Our aim was to investigate the effects of PEEP on cardiorespiratory parameters during resuscitation of very premature lambs delivered by hysterotomy at~125 d gestation (term 147 d). Before delivery, they were intubated and lung fluid was drained. Immediately after delivery, they were ventilated with a Dräger Babylog plus ventilator in volume guarantee mode with a tidal volume of 5 mL/kg. Lambs were randomized to receive 0, 4, 8, or 12 cm H 2 O of PEEP. They were ventilated for a 15-min resuscitation period followed by 2 h of stabilization at the same PEEP. Tidal volume, peak inspiratory pressure, PEEP, arterial pressure, oxygen saturation, and blood gases were measured regularly, and respiratory system compliance and alveolar/ arterial oxygen differences were calculated. Lambs that received 12 cm H 2 O of PEEP died from pneumothoraces; all others survived without pneumothoraces. Oxygenation was significantly improved by 8 and 12 cm H 2 O of PEEP compared with 0 and 4 cm H 2 O of PEEP. Lambs with 0 PEEP did not oxygenate adequately. The compliance of the respiratory system was significantly higher at 4 and 8 cm H 2 O of PEEP than at 0 PEEP. There were no significant differences in partial pressure of carbon dioxide in arterial blood between groups. Arterial pressure was highest with 8 cm H 2 O of PEEP, and there was no cardiorespiratory compromise at any level of PEEP. Applying PEEP during resuscitation of very premature infants might be advantageous and merits further investigation. At birth, the lungs of premature infants are completely airless, fluid filled, surfactant deficient, and noncompliant. It is common for these infants to require ventilation after birth. The recommended technique of resuscitating infants is with a neonatal resuscitation bag (1,2) connected to a face mask or endotracheal tube. The most common devices used do not provide positive end expiratory pressure (PEEP) and therefore may contribute to atelectasis, acute lung injury (3), and hyaline membrane formation. Although PEEP valves are available for self-inflating resuscitation bags, they are not in common use or recommended. PEEP and continuous positive airway pressure (CPAP)

T-Piece Resuscitator Versus Self-Inflating Bag for Preterm Resuscitation: An Institutional Experience

“…6 It appears that widespread use of PEEP during neonatal resuscitation is derived from animal models and observational studies. 7,8 In this study, T-piece increased the mean 1-min to 5-min Apgar score more rapidly than SIB. Although a statistically significant difference in rate of rise was seen between the 2 devices, since the Apgar score at 5 min were not found to be different, the conclusion that the T-piece is superior cannot be definitively stated.…”

Establishing lung gas volumes at birth: interaction between positive end-expiratory pressures and tidal volumes in preterm rabbits

“…However, a specific PEEP level is not recommended, and the guidelines warn that "high levels" of PEEP (8-12 cmH 2 O) may reduce pulmonary blood flow and increase the risk of pneumothoraces (8,24). These guidelines draw on studies in immature animals in which high V T s at birth were reported to cause lung injury, impair gas exchange, and reduce lung compliance (N.H. Hillman, T.J. Moss, I. Nitsos, A.H. Jobe, unpublished data).…”

“…PPV with a high tidal volume (V T ) causes lung injury (3)(4)(5)(6) as does PPV of poorly aerated lungs (7). Providing positive end-expiratory pressure (PEEP) immediately after birth quickly improves oxygenation (8) and the establishment of an FRC (9). However, the optimal PEEP required during resuscitation of very preterm infants is not known.…”

Relationship between oxygen saturation and the mode of oxygen delivery used in newborn resuscitation

“…14,17,22 Others have demonstrated that a properly inflated lung is important in achieving and maintaining proper oxygenation and that infants with inadequate FRC are more prone to desaturation events. [10][11][12][13] Deckardt et al continuously measured SpO 2 of newborns and delivered continuous positive airway pressure to those who failed to achieve an SpO 2 of 80% by 5 min of age. 4 They found that the use of continuous positive airway pressure improved oxygenation.…”

“…5,9 For infants requiring resuscitation, the mode of oxygen (O 2 ) delivery may be an important factor in affecting oxygenation. [10][11][12][13] Oxygenation is promoted by providing supplemental O 2 and/or establishing functional residual capacity (FRC) using positive pressure. Continuous positive airway pressure is effective at establishing FRC in the newborn and reducing ventilationperfusion mismatch through recruiting collapsed alveoli and stabilizing alveoli that are already patent, thereby improving oxygenation.…”