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Measured CPAP in a Noninvasive Pediatric Airway and Lung Model
Neil D Fernandes1,2,3, Esther Chung4, Michael D Salt4,2,3
1Massachusetts General Hospital, Boston, Massachusetts. ndfernandes@mgh.harvard.edu.
Insights
The RAM cannula delivers variable continuous positive airway pressure (CPAP) in pediatric patients, with approximately 25% pressure loss due to air leaks. Minimal leaks allow for clinically effective CPAP delivery.
Area of Science:
- Pediatric critical care
- Respiratory physiology
- Medical device engineering
Background:
- Bronchiolitis is a common cause of pediatric hospital admission in the US.
- Continuous positive airway pressure (CPAP) is a standard supportive treatment for bronchiolitis.
- The RAM cannula is an alternative CPAP delivery device, but its efficacy is uncertain.
Purpose of the Study:
- To evaluate the CPAP delivery accuracy of the RAM cannula in a pediatric lung model.
- To quantify the impact of air leaks on RAM cannula CPAP delivery.
Main Methods:
- A 3D-printed pediatric airway model with 7 sizes was used.
- Ventilator-delivered CPAP (5-10 cm H2O) was applied via RAM cannulas.
- Air leaks of 0-60% were simulated to measure the %leak effect on CPAP delivery.
Main Results:
- Measured CPAP ranged from 2.6 to 9.7 cm H2O, differing from set pressures.
- An average CPAP loss of approximately -25% was observed across tested pressures.
- Higher CPAP levels were achieved with increased set pressure and reduced air leaks.
Conclusions:
- The RAM cannula provides variable CPAP, with significant pressure loss due to air leaks.
- Clinically meaningful CPAP delivery is possible with the RAM cannula if air leaks are minimized.
Background:
Bronchiolitis is the most common cause of admission in children < 2 y of age in the United States. The standard of care involves supportive measures, including noninvasive interventions such as CPAP. CPAP is traditionally delivered through a full face mask; however, pediatric ICUs have been exploring the use of the RAM cannula by Neotech as a mode of CPAP delivery. The level of CPAP delivered via the RAM cannula is uncertain. We performed an in vitro study to determine the level of CPAP delivered via the RAM cannula utilizing a pediatric lung model.
Methods:
Models of 7 sizes of pediatric upper airways, produced with a 3-dimensional printer, were connected to a breathing simulator. We applied each size of RAM cannula to weight-appropriate airway and lung compliance parameters, delivering pressures of 5, 7, and 10 cm H2O using a ventilator in the CPAP mode. Leaks of 0%, 20%, 40%, and 60% were generated to emulate a complete seal, a poor fit, and open-mouth breathing. The outcome measure was the difference in CPAP, referred to as "%leak effect," measured by the lung simulator relative to the CPAP set on the ventilator.
Results:
We found that set CPAP of 5-10 cm H2O generated measured CPAP ranging from 2.6 to 9.7 cm H2O. For the set CPAP levels of 5, 7, and 10 cm H2O, the mean %leak effect values of measured CPAP from the set CPAP were -25%, -26%, and -25.7%, respectively. For each specific cannula-airway combination, increasing the set pressure and decreasing the air leak resulted in higher levels of CPAP delivered.
Conclusions:
The RAM cannula delivered varying amounts of CPAP, with a percent loss of approximately -25% depending on the level of leak in the system. With minimal leak, it is conceivable that the RAM cannula can be used to deliver clinically meaningful CPAP.
