CONTEXT
Conventional nasal continuous positive airway pressure (NCPAP) had been known to improve
the rate of successful extubation in preterm neonates and can be provided via a short
binasal prongs that fit snugly into the infant's nose. To be effective, however, the
prong has to be maintained in place in a way that it can deliver the positive distending
pressure to the upper airway with minimal leak.
Several NCPAP devices are available, but all can cause nasal trauma. Damage to the
skin often is mild and resolves with the cessation of NCPAP but may be a cause of
unexplained septicemia in the preterm population. More significant trauma can result
in permanent disfigurement and long-term functional sequelae.
Heated Humidified High-Flow Nasal Cannulae (HHHFNC) seems to be well tolerated in
patients and easy to apply, leading to increased use around the world. In a number
of reports, authors describe the use of HHHFNC as a mode of respiratory support in
premature infants.[1
2]
MATERIALS AND METHODS
Study design
This is a single center randomized controlled trial done in Royal Women's Hospital,
Melbourne, Victoria, Australia from January 1, 2009 to July 31, 2011.
Outcome
The primary outcome is extubation failure within the 7 days after extubation and was
defined as follows:
Apnea (respiratory pause >20 seconds), more than six episodes in 6 hours or one requiring
intermittent positive pressure ventilation
Acidosis, pH < 7.25 and PCO2 > 66 mmHg
And >15% sustained increase in FiO2 from extubation.
Extubation failure was deemed to have occurred if any single criterion was met in
any one of the 7 days after extubation
Population
Inclusion
Infants born at less than 32 weeks’ gestation
Who required endotracheal intubation and positive pressure ventilation
Were considered ready for extubation by the clinical team.
Exclusion
Suspected upper airway obstruction
Congenital airway malformations
Or major cardiopulmonary malformations.
Intervention
HHHFNC via Vapotherm with 1.5-mm external diameter nasal cannulae (Vapotherm Inc,
Stevensville, MD). Infants allocated to this group were extubated to a flow rate of
8 L/min. Flow rate was weaned to a minimum of 4 L/min.
NCPAP via Hudson binasal prongs, 3.7-4.6 mm external diameter (Hudson Respiratory
Care Inc, Temecula, CA). Infants randomized to NCPAP were extubated to a positive
end-expiratory pressure (PEEP) of 8 cm H2O if the fraction of inspired oxygen (FiO2)
>0.3 or a PEEP of 7 cm H2O if FiO2 < 0.3. PEEP was weaned to a minimum of 5 cm H2O.
The same fixation method was used for both nasal interfaces (Sticky Whiskers Beevers
Manufacturing and Supply, McMinville, OR). A nasal trauma score was adapted from Kaufman
et al. and nasal trauma scores were recorded three times daily for the 7 days after
extubation.
Oxygen saturation targets were 85-92% for both groups and all infants received a loading
dose of 20 mg/kg caffeine citrate before extubation and a maintenance dose of 10 mg/kg/day
until 34 completed weeks of gestation.
Randomization and allocation
A random number sequence was generated with STATA Statistical Software (Release 10.0,
2001; Stata Corp, College Station, TX) and was stratified by gestational age into
less than 28 weeks’ gestation and 28.0-31.6 weeks’ gestation.
A variable block size was used for treatment allocation. Allocation was matched by
the use of sequentially numbered, sealed opaque envelopes that were opened immediately
before the subjects were extubated.
Statistical analyses
Review of data from the study center over a 2-year period (2004-2006) revealed 50%
of infants <32 weeks’ gestation who required mechanical ventilation met the study
extubation failure criteria in the 7 days after extubation with a reintubation rate
of 35%.
A sample size of 130 provided 80% power to detect a reduction in extubation failure
from 50-25% (alpha = 0.05).
Analysis was by intention to treat. Mean values and proportions between groups were
analyzed by Student t-test or 2-sample test of proportions, respectively. All statistical
analyses were performed using STATA Statistical Software: (Release 10.0. Stata Corp).
RESULTS
A total of 132 infants were enrolled between January 1, 2009 and July 31, 2011. All
infants were followed for the first 7 days after extubation, and 121 infants were
followed until their discharge home.
The baseline demographic and ventilation characteristics of enrolled infants with
the exception of sex were similar. There were more males in the NCPAP group n = 41
(63%) compared with n = 33 (49%) of those assigned HHHFNC. There was no interaction
of sex with the primary outcome variable of extubation failure (P = 0.5).
There were no differences in rates of extubation failure or BPD between the two groups.
There were no differences in extubation failure rates in either gestational age stratum.
Infants assigned to HHHFNC had significantly less nasal trauma than those assigned
to NCPAP (P < 0.001) [Table 1].
Table 1
Primary outcome for infants assigned to receive either Vapotherm HHHFNC or NCPAP for
postextubation respiratory support and by subgroup
Seven infants assigned to HHHFNC and eight in the NCPAP group were reintubated in
the first week after extubation, having met the failure criteria. Two infants assigned
to HHHFNC and seven assigned to NCPAP were changed to nasal intermittent mandatory
ventilation (NIMV). At parental request, one infant's therapy was changed from NCPAP
to HHHFNC; consent was retained for the use of primary outcome data.
A total of 13 (20%) of infants assigned to NCPAP were changed to HHHFNC as the result
of nasal trauma in the first 7 days after extubation. These infants had a mean nasal
trauma score of 22 (SD 10.1) compared with a mean score of 7.4 (SD 6.7) in those who
remained on NCPAP (P < 0.001) and a mean score of 3.1 (SD 7.2) in those assigned to
HHHFNC.
CONCLUSION
There was no difference in the rates of extubation failure between infants randomized
to HHHFNC or NCPAP in the first 7 days after extubation. However, HHHFNC was associated
with significantly less nasal trauma compared with NCPAP.
COMMENTARY
Evidence is accumulating addressing the efficacy of HHHFNC utilization in the management
of preterm infants. To date, most of the studies comparing NCPAP to HHHFNC were of
small size and included larger preterm infants.
Evidence suggests the HHHFNC is comparable to NCPAP as a weaning method off conventional
ventilation. The largest study to date was conducted in Australia and presented at
the Pediatric Academic Society (PAS) meeting, 2013 in Washington DC. The study included
300 preterm infants. HHHFNC was found to be noninferior to NCPAP for extubation failure
in VLBW infants. The study failed to show noninferiority for infants less than 26
weeks. This new method of respiratory support in preterm infants was found to be more
convenient to apply and results in less nasal trauma as compared with NCPAP.
We believe that evidence is still not conclusive especially for the smallest preterm
infants less than 26 weeks and that more data are needed. A head to head comparison
of the two available devices with regard to efficacy is also needed.
Abstracted from
Collins CL, Holberton JR, Barfield C, Davis PG. A randomized controlled trial to compare
heated humidified high-flow nasal cannulae with nasal continuous positive airway pressure
postextubation in premature infants. J Pediatr 2013;162:949-54.