2-022 | Additional Comments | Previous Article | Next Article | List of Articles | Submit Comments | Index | FSN Home Page
Nasal Cannula vs nCPAP for Apnea
High-Flow Nasal Cannulae (HFNC) in the Management of Apnea of Prematurity: A Comparison with Conventional Nasal Continuous Positive Airway Pressure (nCPAP). Sreenan C, Lemke RP, Hudson-Mason A, et al. Pediatrics 2001;107(5):1081-3.
The objective of this study was to determine the nasal cannula (NC) flow required to generate positive distending pressure (PDP) equal to that provided by nCPAP at 6 cm H20, and to assess the effectiveness of HFNC as compared with nCPAP in the management of apnea of prematurity. The study population consisted of forty premature infants (EGA 28.7 +/- 0.4 weeks; PMA 30.3 +/- 0.6 weeks) who were being managed with conventional nCPAP for at least 24 hours for clinically significant apnea of prematurity. The frequency and duration of apnea, bradycardia and desaturation episodes were monitored during a 6-hour period on nCPAP and compared with a 6-hour period on HFNC (flows up to 2.5 LPM). End expiratory esophageal pressure was measured on nCPAP and on HFNC, and the gas flow on the nasal cannula was adjusted to generate an end expiratory esophageal pressure equal to that measured on nCPAP.
Results: The flow required to generate a comparable PDP on HFNC varied with the infant’s weight, and was represented by the equation:
NC flow (L/min) = 0.92 + (0.68 x wt (kg)); R=0.72.
There was no difference in the frequency or duration of apnea, bradycardia or desaturation per recording between the two systems.
Comment. I’ve always been a little uncomfortable using HFNC to generate PDP in small premature babies, because of the inability to measure the distending pressure being generated. This study measures end expiratory exophageal pressure at 6 cm H20 of nCPAP, and adjusts the liter flow of the nasal cannula to give a similar reading. The equivalent NC flow rate varied with the patient’s weight, and the relationship was fairly linear. If you solve for NC flow rate in the derived equation, you will find that for infants weighing between 800 and 1600 grams, the required NC flow rate will be between 1.5 and 2.0 LPM. How convenient that it works out to be about the same amount of NC flow that many of us would start with anyway in this group of babies! At least now we have an idea of the equivalent distending pressure generated by this amount of NC flow.