Nasal Continuous Positive Airway Pressure for Respiratory Care of Premature Infants

By Anna Kuruc, Urvinder Kaur, Lauren Harnois, Alex Muller

 

The 28-week premature infant going into respiratory failure with grunting and retractions would greatly benefit from nasal continuous positive airway pressure (CPAP). Grunting frequently occurs as a sign of increased work of breathing. The grunting sound is created by the closure of the glottis and contraction of abdominal muscles. This infant at 28 weeks is in the saccular stage of lung development, and therefore has gas exchange surface area, but alveoli are not present since this does not occur until week 36 gestational age. The structural immaturity of the lungs causes work of breathing to increase as the infant must generate a high pressure to inflate the premature alveoli that might be collapsed. CPAP can help the spontaneously breathing infant in respiratory distress improve oxygenation, reduce alveolar dead space, and decrease work of breathing by splinting the airways open, thereby keeping the alveoli from collapsing .¹

Clinicians often prefer nasal CPAP over invasive mechanical ventilation (MV) due to the hazards that invasive MV pose on the infant such as infection, barotrauma, sedation-related problems, and discomfort. Nasal CPAP and mechanical ventilation both show similar therapeutic outcomes when it comes to mortality. However, MV poses much more risks with the same effects. Even short-term MV shows ventilator induced lung injury (VILI); barotrauma, endotrauma, volutrauma, and atelectruma. VILI is the major factor in chronic lung injury in the neonatal population. Endotracheal intubation itself is very painful and often requires deep sedation, causing hemodynamic instabilities and airway trauma. Mechanical ventilation should only be used as the last treatment option if the infant does not respond to the noninvasive treatment. ²

Nasal CPAP can be delivered to the infant in many ways based on the clinical scenario.  In our case, short binasal prongs would be most effective as infants are nose breathers. Short nasal prongs reduce resistance as opposed to long nasal prongs. Nasal prongs will also help spontaneously breathing infants with mobilization and oral feeding.³ Soft material around the nasal prongs reduces mucosal trauma and noise is flow dependent. Nasal CPAP also uses a heated humidifier to moisten cold, dry air, to avoid mucosal complications.

The main goal in the therapy is to open the airways of preterm infants and reduce the work of breathing.  Evidence shows that CPAP decreases tachypnea, rib recession, and improves thoracoabdominal synchrony. It minimizes obstructive apnea by stenting the airways to maintain airway patency.⁴ Various mechanisms are used to generate CPAP to provide respiratory support for the spontaneously breathing infant. For example, ventilators are used to provide CPAP by delivering a constant flow of gas, which creates positive pressure at the airway by varying the opening of the expiratory port. A Bubble CPAP system can also be used and involves the delivery of a constant flow of gas to the infant’s breathing circuit with the expiratory limb of the breathing circuit submerged under water at a specific depth to create a specific level of CPAP. The Infant Flow system is another mode of delivering CPAP. Nasal CPAP flow rate in the Infant Flow system is usually set at 8 L/minute to maintain a CPAP pressure of about 5 cm H₂O. The flow provides gas to the infant based on the Bernoulli effect; inlet gas passes through the twin nasal jet injector nozzles at high velocity that turn the flow into constant pressure.  In this variable flow CPAP system, if the infant needs more inspiratory flow, more gas is entrained through the Venturi effect. The infant can exhale without impeding the incoming flow through the Coanda effect. Once expiratory flow stops, the device switches to inspiratory position. ¹

Nasal CPAP has been effectively used to avoid endotracheal intubation since 1968.⁴ Although minimal research studies have been conducted on infants and nasal CPAP, both clinical and animal data strongly suggest using CPAP as opposed to mechanical ventilation to reduce ventilator associated lung injury.²

 

1. Walsh B. Neonatal and Pediatric Respiratory Care, Fourth Edition edition. St. Louis: Elsevier Saunders; 2015.
2. DiBlasi RM. Neonatal Noninvasive Ventilation Techniques: Do We Really Need to Intubate? 47th Respiratory Care Journal Conference, “Neonatal and Pediatric Respiratory Care: What Does the Future Hold?” November 2010, Arizona. Respir Care 2011;56(9):1273-1297 25p.
3. Pfister RH, Soll RF. Initial respiratory support of preterm infants: the role of CPAP, the INSURE method, and noninvasive ventilation. Clin Perinatol 2012;39(3):459-481.
4. Jane Pillow J. Which continuous positive airway pressure system is best for the preterm infant with respiratory distress syndrome? Clin Perinatol 2012;39(3):483-496.