Elsevier

The Journal of Pediatrics

Volume 154, Issue 2, February 2009, Pages 177-182.e2
The Journal of Pediatrics

Original article
Observational Study of Humidified High-Flow Nasal Cannula Compared with Nasal Continuous Positive Airway Pressure

https://doi.org/10.1016/j.jpeds.2008.07.021Get rights and content

Objectives

To conduct an in vitro evaluation of a humidified high-flow nasal cannula (HFNC) system at different flows, cannula sizes, and air leaks and also an in vivo analysis of mean end-expiratory esophageal pressure (EEEP) from nasal continuous positive airway pressure at 6 cm H2O (NCPAP+6) versus HFNC.

Study design

In the in vitro study, we measured HFNC system pressure and flow, with varying degrees of leak and with and without the use of a pressure-limiting valve. In the in vivo study, we measured EEEP in 15 newborns on NCPAP+6 and then on HFNC at 6 L/minute, with flow decreased by 1 L/minute every 30 minutes. Heart rate, respiratory rate, fraction of inspired oxygen, arterial oxygen saturation, respiratory distress syndrome score, and EEEP were recorded for each intervention. Data analysis was done using repeated-measures analysis of variance and linear regression.

Results

In the in vitro study, in the absence of leaks, the pressures were limited by the pressure-limiting valve only at flows ≥ 2 L/minute. With leaks of 30% and 50%, delivered pressures were always < 3 cm H2O. In the in vivo study, respiratory rate increased from baseline (NCPAP+6) as flow decreased (P < .02). Intrapatient and interpatient coefficients of variation were always high.

Conclusions

A pressure-limiting valve is necessary in a HFNC system. Although mean EEEP levels were similar in NCPAP+6 and HFNC, tachypnea developed as flow diminished. This system apparently cannot predict EEEP, because of interpatient and intrapatient variation.

Section snippets

In Vitro Study

Using a calibrated gas flow analyzer (Fluke Biomedical, Everett, Washington), pressure and gas flow values were analyzed in triplicate at 5 different points within the HFNC system: at the gas flow source, immediately before the pressure-limiting valve, immediately after the pressure-limiting valve, at the end of the HFNC circuit tubing, and at the distal end of the nasal cannula (Figure 1). available at www.jpeds.com). Both the preterm and neonatal cannulas (Fisher & Paykel BC series, 2.4 mm

In Vitro Study

With the HFNC system completely intact with the pressure-limiting valve in place and set at 45 cm H2O, as gas flow was increased, delivered flow was preserved throughout the system, and pressures ranged from 35.7 cm H2O at 1 L/minute to 45.8 cm H2O at 6 L/minute, apparently limited by the pressure-limiting valve (Figure 2; available at www.jpeds.com). Delivered flow and pressure were attenuated distal to the nasal cannula at gas flows ≥ 2 L/minute. Distal to the neonatal nasal cannula, gas flow

Discussion

Despite very limited information on their performance, HFNC systems are being increasingly used for noninvasive neonatal respiratory support. We investigated pressure delivery for one such system both in vitro and in vivo in this observational study of humidified HFNC compared with NCPAP. The main findings in vitro were the demonstrated need for a pressure-limiting valve to control potential excessive pressure delivery, along with a dramatic reduction in the delivered pressures in the face of a

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Financial support for this study was provided by a grant from the Children's Hospitals and Clinics of Minnesota Foundation. The authors declare no conflicts of interest.

This trial was registered at www.clinicaltrials.govNCT00356668

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