The Science Journal of the American Association for Respiratory Care

2012 OPEN FORUM Abstracts

COMPARATIVE STUDY OF CIRCUIT PRESSURES AND CPAP EFFECT FOR TWO HIGH FLOW NASAL CANNULA DEVICES.

Gary R. Lowe1, Randy Willis1, Shirley Holt3, Tracy Thurman3, Mark Heulitt1,2; 1Respiratory Care Services, Arkansas Children’s Hospital, Little Rock, AR; 2Department of Pediatrics, Critical Care Medicine, University of Arkansas for Medical Sciences, Little Rock, AR; 3Arkansas Children’s Hospital Research Institute, Little Rock, AR

Background: High pressures can be generated within the circuit of heated high flow nasal cannula (HHFNC) systems. A comparative study was undertaken to determine the pressures generated within the circuit and the patient interface of two manufacturers HHFNC devices. Objective: Evaluate the pressures generated within the circuit and at the patient interface. Methods: A bench study was conducted comparing maximal flows and pressures in a HHFNC system with two manufacturers’ nasal cannula devices [Fisher/Paykel (F/P) and Neotech Ram (RA)]. Flow rates for cannula sizes were set as follows: 6 LPM in F/P premature infant cannulas (F/P1) and RA preemie infant cannulas (RA1), 7 LPM in F/P infant cannulas (F/P2) and RA newborn cannulas (RA2), and 8 LPM in F/P pediatric cannula (F/P3) and RA infant cannulas (RA3). Five cannulas were used for each test. Data were collected at 32° and 37°C. FiO2 was 1.0. The external diameters and lengths of all cannulas were measured with calipers. Measurements of flow and pressure were acquired using the Biopac MP-100 System. For all cannulas, one 0-35 LPM pneumotachograph (PNT) was placed where the large bore tubing connects to the nasal cannula and one 0-35 LPM PNT was connected directly to the portion of the cannula that would be inserted in the nares. Pressure was calibrated with an SJ-16 vertical manometer. All output signals were routed via an analog channel box into the Biopac MP-100 data acquisition unit converting them into digital signals that can be processed with a computer. Signals were obtained at a rate of 1000 samples per second. Results: The circuit pressures noted in F/P cannulas were significantly higher (60% – 70%, p < 0.001) than in the RA cannulas. However, there was < 10% difference in pressures generated at the patient interface between manufacturers. Measured pressure at the patient interface was less than 0.50 cmH2O for both manufacturers (F/P 0.29-0.42; RA 0.27-0.42 cmH20). Temperature settings did not appear to have an effect on pressures generated in either case. The diameters of the F/P cannulas were smaller than the equivalent size of RA cannulas. Conclusion: Based on these results, F/P cannulas showed significantly higher circuit pressures than RA cannulas. Additionally, the diameters of the F/P cannulas may be responsible for the degree of back pressures generated in the circuit. Minimal pressures were generated at the patient interface in both manufacturers’ cannulas. Sponsored Research - None