Effective ventilation: The most critical intervention for successful delivery room resuscitation

Abstract

Lung aeration is the critical first step that triggers the transition from fetal to postnatal cardiopulmonary physiology after birth. When an infant is apneic or does not breathe sufficiently, intervention is needed to support this transition. Effective ventilation is therefore the cornerstone of neonatal resuscitation. In this article, we review the physiology of cardiopulmonary transition at birth, with particular attention to factors the caregiver should consider when providing ventilation. We then summarize the available clinical evidence for strategies to monitor and perform positive pressure ventilation in the delivery room setting.

Keywords: Lung aeration; Newborn; Resuscitation; Ventilation.

Figure 1:. Phases of lung aeration during newborn transition

Phase 1: The airways are still fluid-filled, and the emphasis is to clear the fetal lung liquid and aerate the lung. Phase 2: Lung aeration has been achieved and gas exchange is now possible. The air-liquid surface tension is present, and fetal lung liquid (now in the interstitial tissue) increases perialveolar interstitial tissue pressures. The focus of respiratory support is minimizing alveolar collapse and/or reflooding during expiration. Phase 3: The lungs is aerated and liquid is cleared from the tissue. Ventilation is now focused on gas exchange and metabolic homeostasis.

Figure 1:. Phases of lung aeration during newborn transition

Phase 1: The airways are still fluid-filled, and the emphasis is to clear the fetal lung liquid and aerate the lung. Phase 2: Lung aeration has been achieved and gas exchange is now possible. The air-liquid surface tension is present, and fetal lung liquid (now in the interstitial tissue) increases perialveolar interstitial tissue pressures. The focus of respiratory support is minimizing alveolar collapse and/or reflooding during expiration. Phase 3: The lungs is aerated and liquid is cleared from the tissue. Ventilation is now focused on gas exchange and metabolic homeostasis.

Figure 1:. Phases of lung aeration during newborn transition

Phase 1: The airways are still fluid-filled, and the emphasis is to clear the fetal lung liquid and aerate the lung. Phase 2: Lung aeration has been achieved and gas exchange is now possible. The air-liquid surface tension is present, and fetal lung liquid (now in the interstitial tissue) increases perialveolar interstitial tissue pressures. The focus of respiratory support is minimizing alveolar collapse and/or reflooding during expiration. Phase 3: The lungs is aerated and liquid is cleared from the tissue. Ventilation is now focused on gas exchange and metabolic homeostasis.

Figure 2:. Impact of closed glottis on tidal volume delivery during sustained inflation (SI)

In this respiratory tracing, when the sustained inflation begins, the pressure rises but there is almost no positive flow and no volume enters the lung. When the infant starts spontaneously breathing (and opens the glottis), there is positive flow to the infant with improved tidal volume delivery.

Figure 3:. Respiratory function monitor display during positive pressure ventilation

In each display, respiratory data are presented numerically on left side and with waveforms displayed centrally, as labelled on panel A A: Successful PPV: Unobstructed air flow, exhaled tidal volume between 4–8 ml/kg, and there is no leak. B: PPV with consistent mask leak. Air flow is consistently positive, exhaled tidal volumes are inconsistent and often low, and calculated leak is displayed numerically in the bottom left corner. C: PPV with anatomic or functional airway obstruction. Peak pressures are consistent, minimal positive and negative air flow, exhaled tidal volumes are low, and there is no leak.