How is the design of the nasal interface critical in achieving bubble CPAP results?

How the design of the nasal interface is critical in achieving bubble CPAP results?

In this article, Baldursdottir et al discuss the design of the nasal interface and its impact on the pressure delivery and work of breathing in bubble CPAP circuits.
In the original bCPAP design, the interface has wide-bore tubing and a low-resistance that creates a stable airway pressure reflected by the submersion depth of the expiratory tubing. With the increasing popularity of the bCPAP, new systems have emerged with different alterations. Most of these have not been compared or validated with the original design.
Authors identified three common alterations to the bCPAP design:
  1. the resistance of nasal interface,
  2. the volume of dead space and
  3. the diameter of expiratory tubing.
Authors examined the effect of these alterations on pressure delivery and work of breathing in a mechanical lung model using simulated breathing. Outcomes were the delivered CPAP and the imposed work of breathing. Their findings confirmed that high-resistance interfaces and narrow expiratory tubing increased the work of breathing. In addition, narrow expiratory tubing resulted in higher CPAP levels than indicated by the submersion depth. They concluded that new bubble CPAP systems should be designed with low-resistance and large diameter tubing, and they should be validated against the original bCPAP devices.

Read more… Baldursdottir S, Falk M, Donaldsson S, Jonsson B, Drevhammar T: Basic principles of neonatal bubble CPAP: effects on CPAP delivery and imposed work of breathing when altering the original design. Arch Dis Child Fetal Neonatal Ed 2020;0:F1–F5.