Basic principles of neonatal bubble CPAP: effects on CPAP delivery and imposed work of breathing when altering the original design

Abstract

BackgroundThe original bubble continuous positive airway pressure (bCPAP) design has wide-bore tubing and a low-resistance interface. This creates a stable airway pressure that is reflected by the submersion depth of the expiratory tubing. Several systems with alterations to the original bCPAP design are now available. Most of these are aimed for use in low-income and middle-income countries and have not been compared with the original design.ObjectiveWe identified three major alterations to the original bCPAP design: (1) resistance of nasal interface, (2) volume of dead space and (3) diameter of expiratory tubing. Our aim was to study the effect of these alterations on CPAP delivery and work of breathing in a mechanical lung model. Dead space should always be avoided and was not further tested.MethodsThe effect of nasal interface resistance and expiratory tubing diameter was evaluated with simulated breathing in a mechanical lung model without interface leakage. The main outcome was delivered CPAP and imposed work of breathing.ResultsHigh-resistance interfaces and narrow expiratory tubing increased the work of breathing. Additionally, narrow expiratory tubing resulted in higher CPAP levels than indicated by the submersion depth.ConclusionOur study shows the significant effect on CPAP delivery and imposed work of breathing when using high-resistance interfaces and narrow expiratory tubing in bCPAP systems. New systems should include low-resistance interfaces and wide-bore tubing and be compared with the original bCPAP. Referring to all systems that bubble as bCPAP is misleading and potentially hazardous.

Bubble CPAP splitting: innovative strategy in resource-limited settings

“…A recent study of effect of alterations in the original CPAP system design in a mechanical lung model concluded that high-resistance interfaces (like RAM cannula and modified nasal oxygen cannula) and narrow expiratory tubing (with internal diameters less than 8 mm) in bCPAP systems can significantly affect CPAP delivery and can result in increased work of breathing. 6 Use of standard low-resistance Hudson nasal prongs and corrugated tubing (with an internal diameter of 10 mm) in our study prevents such limitations in CPAP delivery.…”

“…However, many such designs use a high-resistance interface and narrow expiratory tubing, and this can significantly affect CPAP delivery and imposed work of breathing. 6 There is anticipated to be a surge in the number of preterm births in India due to rising maternal infection with the novel coronavirus infection and a parallel dwindling of availability of medical supplies, ventilators and CPAP machines because of demands in adult intensive care units and wards. Therefore, preterm and high-risk infants with respiratory distress may miss out on this therapy.…”

Evaluation of a Bubble CPAP System for Low Resource Settings

“…As a result, care providers in low-and middle-income settings often resort to improvising nasal bubble CPAP (bubble CPAP) systems; approximately one third of the hospitals in the Indian survey 18 using nasal CPAP used home-made bubble CPAP systems; these systems were made from supplies on hand, which typically include a compressed and nonhumidified pure oxygen (100%) gas source. They often give poor quality CPAP because the thin nasal cannulas that they use are difficult to exhale through 19,20 and they lead to prolonged exposure to pure oxygen, which can cause damage to the eyes, lungs, and brain.…”

“…Lowcost CPAP systems often do not include humidification, have large amounts of dead space that cause the patient to rebreathe carbon dioxide and use high-resistance circuits that have a large imposed work of breathing. 19 Therefore, there remains an unmet need for a system that provides high-quality bubble CPAP, does not require electricity or compressed air, is easy to use, and is low cost.…”

Early initiation of bubble CPAP and its outcome in neonates with respiratory distress

“…Though oxygen can be provided through continuous positive airway pressure, CPAP can also be provided via various interfaces such as face mask, nasal prongs, mechanical ventilator, CPAP machine and the Bubble CPAP (BCPAP). Bubble CPAP is known for its low cost and its delivery of CPAP by underwater seal [5,9] . BCPAP with its underwater seal has been widely researched and implemented across various neonatal intensive care units across the World, especially in low middle income countries [10] .…”