The Neonatal Resuscitation Program (NRP) provides a standardized approach for managing newborns who require assistance at birth. A significant challenge is helping the infant’s lungs transition from a fluid-filled state to an air-filled state for breathing. Positive End-Expiratory Pressure (PEEP) is a fundamental technique used during resuscitation to support this transition and facilitate effective lung function. NRP guidelines recognize PEEP as a necessary component of positive pressure ventilation, especially for premature infants, to safeguard delicate lung structures.
Defining PEEP in the NRP Context
PEEP is a mechanical respiratory technique that maintains positive pressure within the airways and alveoli at the end of the exhalation phase. Without PEEP, pressure inside the lungs returns to zero, allowing the small air sacs to collapse completely. PEEP creates a residual pressure that resists this collapse, keeping the airways open. This continuous positive pressure is a passive force applied through a mask or an artificial airway during assisted ventilation.
The mechanism of PEEP involves setting a specific pressure level sustained throughout the entire breathing cycle, even after the assisted breath is delivered. This constant pressure acts as a splint to the lung’s smallest structures, preventing them from sealing shut. Holding the alveoli partially inflated means less energy is required for the baby to re-open them with the next breath.
The pressure is delivered using specialized equipment, such as the T-piece resuscitator, which is preferred for its ability to deliver precise and consistent pressures. This controlled delivery ensures the desired pressure is reliably maintained. The goal is to apply enough pressure to achieve physiological benefits without harming underdeveloped lung tissue.
Establishing Functional Residual Capacity
A primary goal of PEEP in neonatal resuscitation is establishing the functional residual capacity (FRC) in the newborn’s lungs. FRC is the volume of air remaining in the lungs after a normal exhalation. Establishing this baseline volume is a major hurdle because the newborn’s lungs are filled with fetal lung fluid and have high surface tension.
Because of fetal lung fluid and often a lack of surfactant, the air sacs naturally want to collapse. PEEP provides the counter-pressure needed to overcome this high surface tension, forcing the fluid to be absorbed or cleared. This sustained pressure keeps the newly aerated sections of the lung open, creating the necessary volume of air for ongoing gas exchange. Without this residual volume, the lung’s compliance, or its ability to stretch and expand, is reduced.
Establishing and maintaining FRC transforms the lung from a liquid-filled organ to a gas-exchanging one. This process ensures a continuous supply of gas is available in the alveoli, even between breaths. This step is important in the transition from fetal circulation, as it allows pulmonary blood vessels to dilate in response to oxygen, increasing blood flow to the lungs.
Optimizing Gas Exchange and Preventing Atelectasis
The stable lung volume achieved by establishing FRC improves gas exchange and prevents atelectasis. Atelectasis is the partial or complete collapse of a lung section, which PEEP combats by physically holding the air sacs open. Preventing this collapse ensures the maximum surface area remains available for the exchange of oxygen and carbon dioxide.
Preventing the cyclical collapse and re-opening of the alveoli (atelectrauma) protects delicate lung tissue from injury. The constant positive pressure preserves the integrity of surfactant, a substance that naturally lowers surface tension and prevents alveolar collapse. Maintaining open air sacs allows for better diffusion of oxygen into the pulmonary capillaries and removal of carbon dioxide.
Keeping the alveoli open helps optimize ventilation-perfusion (V/Q) matching. This is the balance between the amount of air reaching the alveoli (ventilation) and the blood flow passing by them (perfusion). By ensuring well-perfused areas are also well-ventilated, PEEP maximizes the efficiency of oxygen uptake and carbon dioxide removal. This optimization improves the baby’s oxygen saturation levels.
Practical Considerations and Monitoring
The NRP guidelines suggest a starting PEEP level of 5 centimeters of water (cm H2O) when initiating positive pressure ventilation. This setting is safe and effective for most newborns requiring resuscitation. PEEP can be delivered using devices like the T-piece resuscitator or a flow-inflating bag with a PEEP valve, which allows for precise pressure control and consistent delivery.
Careful monitoring is necessary because PEEP, while beneficial, can introduce potential complications, primarily barotrauma. Barotrauma is lung injury caused by excessive pressure, which can lead to air leaks, such as a pneumothorax. Clinicians must monitor for adequate chest rise, which indicates effective inflation without overdistension.
Heart rate and oxygen saturation, measured by pulse oximetry, are continuously tracked to assess PEEP effectiveness. An increase in heart rate is the most rapid indicator that ventilation and PEEP are aerating the lungs. Adjustments to the PEEP setting should be made cautiously and incrementally, guided by the infant’s clinical response and the need to achieve effective oxygenation while minimizing lung injury risk.