A high-value, low-cost bubble continuous positive airway pressure system for low-resource settings: technical assessment and initial case reports

Abstract

Acute respiratory infections are the leading cause of global child mortality. In the developing world, nasal oxygen therapy is often the only treatment option for babies who are suffering from respiratory distress. Without the added pressure of bubble Continuous Positive Airway Pressure (bCPAP) which helps maintain alveoli open, babies struggle to breathe and can suffer serious complications, and frequently death. A stand-alone bCPAP device can cost $6,000, too expensive for most developing world hospitals. Here, we describe the design and technical evaluation of a new, rugged bCPAP system that can be made in small volume for a cost-of-goods of approximately $350. Moreover, because of its simple design--consumer-grade pumps, medical tubing, and regulators--it requires only the simple replacement of a <$1 diaphragm approximately every 2 years for maintenance. The low-cost bCPAP device delivers pressure and flow equivalent to those of a reference bCPAP system used in the developed world. We describe the initial clinical cases of a child with bronchiolitis and a neonate with respiratory distress who were treated successfully with the new bCPAP device.

Conflict of interest statement

Competing Interests: Author Robert Miros is CEO of 3rd Stone Design. 3rd Stone is involved in developing the bCPAP device into a commercial product. Thus far, he has been contracted as part of a grant to produce 114 bCPAP devices. This does not alter the authors' adherence to all PLOS ONE policies on sharing data and materials.

Figures

Figure 1. Block diagram and photograph of bCPAP system.

The system consists of: (1) an adjustable flow generator; (2) a pressure-regulated delivery system; and (3) a patient interface. Flow is generated by two air pumps that can be blended with oxygen from a tank or concentrator. The total flow rate and fraction of oxygen delivered are controlled by two flow regulators. The output of the flow generator is connected to the pressure-regulated delivery system. Pressure is controlled by submerging a pressure control tube in a column of water; the mean pressure in the system is determined by the height of the water column. The patient interface is also connected to the pressure control tube, ensuring that the pressure in the patient interface and the pressure control tube are equivalent. The pressurized air mix is delivered to the patient's nostrils via a set of binasal prongs terminated at the distal end.

Figure 2. Pressure vs. time at the nasal prongs for two bCPAP devices.

(Left) a reference standard bCPAP device used clinically in the US and (Right) the low-cost bCPAP device. Dotted lines show the mean and average peak pressures, averaged across 60 seconds of data collection. The pressure waveforms of the two devices are similar, indicating delivery of equivalent therapeutic pressure. In both devices, the mean pressure is controlled by adjusting the height of water in the pressure control tube, and the high frequency oscillations about the mean are associated with the formation of bubbles at the distal tip of the pressure control tube. There were no statistically significant differences between the pressures generated by the two devices (Student t-test, p

Figure 3. Comparison of reference standard and low-cost bCPAP output pressure under different flow and pressure settings.

Each bCPAP system was assembled and nasal prong pressure was measured for 60 seconds of operation and mean pressures were calculated; results were then averaged for 10 independent trials of each system. (A) The mean pressure (mid-point of bar) and peak low and high pressures at a flow rate of 7 L/min at varying pressure settings. (B) The mean pressure (mid-point of bar) and peak low and high pressures at a pressure of 6 cm H2O and varying flow rates.

Figure 4. Vital signs for 6-month old patient with bronchiolitis (a) and a neonate with respiratory distress (b) immediately before and after initiation of bCPAP.

(A) Time course immediately before treatment (large symbols) and after initiation of therapy (small symbols). The patient received CPAP treatment with gradually decreasing oxygen flow for 4 days, was then transitioned to nasal oxygen, and finally transitioned to room air. The patient was discharged on day 6. (B) Time course immediately before treatment (large symbols) and after initiation of therapy (small symbols). The patient received CPAP treatment for 3.5 days. The fraction of oxygen was gradually decreased to room air during the first 2 ½ days.