In the October issue of Pediatrics, Walsh et al1 describe the use of nasal cannulae in a population of 1508 infants of <1250 g at birth, of whom 209 were challenged between 35 and 37 weeks' postconceptional age by the removal of oxygen and the cannula. This was performed by using the physiologic definition of bronchopulmonary dysplasia (BPD) previously described by this group.2 More than one quarter of the 187 infants for whom results were available were receiving a fraction of inspired oxygen (Fio2) of <0.23 using accepted calculations, and 72% of such infants were able to maintain adequate oxygen saturations (defined as a pulse oxygen saturation of >90%) when their cannulae were removed. Infants who failed the oxygen-removal challenge had a mean calculated Fio2 of 0.26. The authors speculate that one reason for continued use of the cannula was lack of knowledge of the actual delivered Fio2, an explanation that would not account for the use of a nasal cannula to deliver room air, used in 22 of their infants, some of whom had flows as high as 2 L/minute. Indeed, 7 infants receiving room air failed to tolerate room air without the cannula.
The current experience by Walsh et al raises a number of questions. Is the use of an oxygen challenge more meaningful than the actual clinical prescription of oxygen and method of delivery? In their previous study2 they demonstrated that infants who successfully tolerated oxygen withdrawal were less likely to go home on oxygen but did not differ in the receipt of diuretics or steroids when compared with infants who failed such a challenge. There was no information for the use of such treatments in the current study. Almost all studies evaluating longer-term neurodevelopment in very low birth weight infants demonstrate that the diagnosis of BPD is a risk factor for the occurrence of subsequent neurodevelopmental impairment. It would be of considerable interest to know whether infants tolerating oxygen removal experienced any differences in such longer-term outcomes compared with those who failed the oxygen-removal challenge, factoring in the receipt of other treatments that may reflect the severity of BPD.3
The use of nasal cannula-delivered oxygen with room air and flows of up to 2 L/minute is of some concern. Locke et al4 previously demonstrated that flows of 2 L/minute using a 0.3-cm nasal cannula produced a mean pressure of 9.8 cm H2O in infants of 30 weeks' gestation, studied at 28 days of age. More recently this group has demonstrated that high-flow nasal cannulae (HFNC) are associated with significantly higher upstream pressures, which may represent a significant hazard.5 Sreenan et al6 used HFNC up to 2.5 L/minute to produce continuous positive airway pressure (CPAP) of 6 cm H2O, as measured by equivalent esophageal pressures (4.5–4.6 cm H2O) and reported that 6 hours of such treatment was equivalent to 6 hours of traditional CPAP for the treatment of apnea in infants with birth weights of <2 kg, studied at a mean postconceptional age of 30 weeks. Their calculations would indicate that a flow of 1.6 L/minute in a 1000-g infant and 1.3 L/minute for a 500-g infant using similar cannulae would produce 6 cm H2O CPAP. There are increasing reports using HFNC as a form of respiratory support in preterm and term newborn infants,7,8 with flows as high as 6 L/minute,9 without documentation of the level of CPAP.
Although the use of HFNC may seem to be an attractive approach that would conceivably avoid trauma to the nose using the smaller nasal cannula compared with most nasal CPAP interfaces, there are a number of concerns when using nonheated and nonhumidified HFNC, including desiccation of the nose with associated bleeding10 and airway obstruction and infection.11 Perhaps the most critical issues are the lack of knowledge of the actual level of CPAP delivered to the infant and the inability of current delivery systems to prevent excessive pressure delivery to the infants' airway, which may result in significant lung overexpansion.12 Sreenan et al pointed out that adequate pressure delivery required maintenance of “a good seal in the oral cavity,”6 consistent with previous observations that there is a significant fall in pressure from cannula to pharynx that is aggravated when the mouth is open as shown for CPAP.13 The use of a pressure-regulated source of CPAP such as a ventilator or underwater seal ensures that within narrow limits the delivered pressure will not exceed the set pressure irrespective of the state of the airway. The actual airway pressure delivered by using a high-flow gas source completely depends on the presence of leaks within the airway. If these are always constant, then the actual pressure using a given cannula size may be predictable; however, such conditions seldom exist in the preterm infant. Thus, if the infant closes his or her mouth, and there are dried secretions around the nares that essentially occlude the nose around the cannula tips, the flow will continue to increase the pressure until either the airway opens or the air under pressure can escape somewhere else. One would hope that the natural airway orifices would be the first to give before the development of gastric distension or lung overexpansion. Locke et al stated that it was “inherently unsafe to use nasal cannulas for the purpose of generating positive end-distending pressure.”4 The American Association of Respiratory Care 2002 Clinical Practice Guideline14 stated that maximum flow for nasal cannulae in newborn infants should not exceed 2 L/minute, a flow that may be excessive for the extremely low birth weight infant.
Before we fully adopt the use of HFNC for our extremely low birth weight infants, especially with flows in excess of 1 L/minute, we need to determine if the natural airway orifices of our smallest infants are capable of acting as intrinsic predictable blow-off valves that will prevent the occurrence of excessive airway pressure. Alternatively, we must develop delivery systems capable of detecting and preventing such situations.
The study by Walsh et al provides additional evidence that the clinical calculation of the effective Fio2 will facilitate appropriate oxygen therapy for the preterm infant. One can extrapolate from the calculations used by Walsh et al that at cannula flows >1 L/minute per kilogram of infant weight, the Fio2 of the cannula will reflect the actual Fio2 of the infant. Longer-term outcome information may assist in determining the most relevant method of diagnosing BPD. For infants treated with HFNC, I believe that it may be more important to be aware of the level of delivered CPAP than the actual Fio2, especially because all such infants are currently monitored with pulse oximetry. HFNC seem to have been rapidly accepted because of their simplicity, ease of use, and the introduction of a device that permits adequate heating and humidification.15 Simple, however, may not be safe.
- Accepted July 18, 2005.
- Address correspondence to Neil N. Finer, MD, Department of Pediatrics, University of California, 200 W Arbor Dr, 8774, San Diego, CA 92103-8774. E-mail:
No conflict of interest declared.
- ↵Walsh M, Engle W, Laptook A, et al. Oxygen delivery through nasal cannulae to preterm infants: can practice be improved? Pediatrics.2005;116 :857– 861
- ↵Walsh MC, Yao Q, Gettner P, et al. Impact of a physiologic definition on bronchopulmonary dysplasia rates. Pediatrics.2004;114 :1305– 1311
- ↵Madan A, Brozanski BS, Cole CH, Oden NL, Cohen G, Phelps DL. A pulmonary score for assessing the severity of neonatal chronic lung disease. Pediatrics.2005;115 (4). Available at: www.pediatrics.org/cgi/content/full/115/4/e450
- ↵Locke RG, Wolfson MR, Shaffer TH, Rubenstein SD, Greenspan JS. Inadvertent administration of positive end-distending pressure during nasal cannula flow. Pediatrics.1993;91 :135– 138
- ↵Chang GY, Cox CC, Shaffer TH. Nasal cannula, CPAP and vapotherm: effect of flow on temperature, humidity, pressure and resistance. Pediatr Acad Soc.2005:57 :1231
- ↵Sreenan C, Lemke RP, Hudson-Mason A, Osiovich H. High-flow nasal cannulae in the management of apnea of prematurity: a comparison with conventional nasal continuous positive airway pressure. Pediatrics.2001;107 :1081– 1083
- ↵Quinn D. Nasal cannula treatment for apnea of prematurity. Pediatr Acad Soc.2005;57 :1248
- ↵Ovalle OO, Gomez T, Troncoso C, Palacios J, Ortiz E. High flow nasal cannula after surfactant treatment for infant respiratory distress syndrome in preterm infants <30 weeks. Pediatr Acad Soc.2005;57 :3417
- ↵Ramanathan A, Cayabyab R, Sardesai S, Siassi B, Seri T, Ramanathan R. High flow nasal cannula use in preterm and term newborns admitted to neonatal intensive care unit: a prospective, observational study. Pediatr Acad Soc.2005;57 :3424
- ↵Courtney SE, Pyon KH, Saslow JG, Arnold GK, Pandit PB, Habib RH. Lung recruitment and breathing pattern during variable versus continuous flow nasal continuous positive airway pressure in premature infants: an evaluation of three devices. Pediatrics.2001;107 :304– 308
- ↵De Paoli AG, Lau R, Davis PG, Morley CJ. Pharyngeal pressure in preterm infants receiving nasal continuous positive airway pressure. Arch Dis Child Fetal Neonatal Ed.2005;90 :F79– F81
- Copyright © 2005 by the American Academy of Pediatrics