Published online March 17, 2008
PEDIATRICS
Vol. 121
No. 4
April 2008, pp.
e754-e758
(doi:10.1542/peds.2007-0251)
Use of Nasal Continuous Positive Airway Pressure During Retrieval of Neonates With Acute Respiratory Distress
Philip G. Murray, MRCPCH and
Michael J. Stewart, FRACP
Newborn Emergency Transport Service, Royal Women's Hospital, Carlton, Victoria, Australia
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ABSTRACT
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OBJECTIVE. Although nasal continuous positive airway pressure is widely used in neonatal units, its use in neonatal transport is not yet established. Previous reports have been limited to small numbers of primary road transports and larger numbers of return transports while its use in air transportation has not been reported. The aim of this study was to assess the safety and effectiveness of transporting neonates and infants by road or air while treated with nasal continuous positive airway pressure.
METHODS. We conducted a retrospective review of the records of all infants transported between January 1, 2004, and November 1, 2005.
RESULTS. A total of 220 infants were treated with nasal continuous positive airway pressure; of these, 13 infants (6%) were intubated before transport, leaving 207 infants transported on a median nasal continuous positive airway pressure of 7 cm H2O. Thirty infants were transported by fixed or rotary wing aircraft and 190 by road. No infants required intubation or bag and mask ventilation during transport. Twenty-eight infants (13%) required intubation within 24 hours of arrival at the receiving hospital, 4 infants (2%) were intubated >24 hours after arrival, 11 infants (5%) were intubated for surgery, and 164 infants (73%) were never intubated. A total of 111 infants (50%) were preterm and <72 hours old at transport, and 32 infants (15%) were 
32 weeks' gestational age and <72 hours old at transport. Fraction of inspired oxygen was significantly lower at the end of transport (0.45 vs 0.34).
CONCLUSIONS. Nasal continuous positive airway pressure is effective and has an acceptable safety margin for the road-based transportation of infants with acute respiratory distress. Air transport is feasible but larger studies are required to assess safety.
Key Words: NCPAP • transport • fixed wing • rotary wing • neonate
Abbreviations: NCPAP—nasal continuous positive airway pressure • NETS—Newborn Emergency Transport Service • TCO2—transcutaneous CO2 • FIO2—fraction of inspired oxygen • RDS—respiratory distress syndrome • GA—gestational age
Nasal continuous positive airway pressure (NCPAP) is a safe and effective mechanism for providing respiratory support for term and preterm infants.1,2 The use of NCPAP in Australia and New Zealand is increasing for all gestations.3 This rise in NCPAP use reflects evidence from animal studies suggesting reduced lung injury with NCPAP compared with mechanical ventilation4 and reports of lower rates of chronic lung disease in infants cared for in units favoring the use of NCPAP over intubation and ventilation.5,6
Until recently there has been little published data on the use of NCPAP in neonatal transport. Simpson et al7 described the use of NCPAP via an infant flow driver in 6 infants during a 1-year period in Scotland. A larger series of 100 infants transported by road on NCPAP has been reported from a team based in Cambridge, United Kingdom.8 Neither of these reports included aeromedical transport of infants on NCPAP. One group from Scotland reports intubating all of the infants on NCPAP requiring aeromedical transport.9 There are limited data on the use of NCPAP in the transport of infants with acute respiratory distress, with the 100 patients in the Cambridge report having a mean age of 28 days and only 3 infants identified as having acute respiratory distress.8
The Victorian Newborn Emergency Transport Service (NETS) is the largest provider of infant and neonatal transport in Australia. NETS serves a population of 5 million people and covers 225000 km2. Approximately 2600 infants are transported each year, of which 1100 are emergency transfers. Transport by fixed and rotary wing aircraft accounts for 15% of transfers. Virtually all of the newborns in Victoria who require either NCPAP or ventilation are cared for in 1 of the 4 NICUs based in Melbourne, Australia. The transport team consists of a neonatal transport nurse and a transport fellow who is usually a senior pediatric trainee. All of the transports are triaged and supervised by consultant neonatologists on-call exclusively for transport. NCPAP is delivered by Hudson prongs connected to a Stephan ventilator, which delivers warmed, humidified gas. The aim of this study was to describe a large cohort of neonates and infants transported on NCPAP including a large number with acute respiratory distress.
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METHODS
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A computer database of all of the transports undertaken by NETS was searched for transfers using NCPAP as the mode of respiratory support between January 1, 2004, and November 1, 2005. The transport records of each infant were then obtained and demographic and clinical information collected along with data on the mode and duration of transport. All of the transported infants were followed up for 1 week by daily telephone calls to the receiving unit and this was recorded in the transport notes. Outcome was recorded as intubation within 24 hours of arrival, >24 hours after arrival, for surgery or not intubated.
For each infant, an initial assessment is made by the transport team, followed by a discussion with the NETS consultant to plan the ongoing management. There are no set criteria used by NETS to determine which infants receive NCPAP and which are intubated and ventilated. The decision on the mode of respiratory support (headbox oxygen, NCPAP, or intubation/ventilation) is made by the NETS consultant on the basis of the transport team's assessment.
Intubation and administration of surfactant with subsequent immediate extubation is not a management strategy routinely used by NETS or any of the tertiary perinatal centers in Victoria during the study period. Thus, none of the infants transported on NCPAP received surfactant before transport.
When NCPAP is commenced, a period of 10 to 20 minutes of observation is undertaken before transfer into the transport incubator to ensure it is adequately tolerated. This study included infants already on NCPAP at he time of referral, as well as those not on respiratory support before transport but deemed suitable for NCPAP. Infants who failed the trial on NCPAP were included on the basis of intention to treat.
NCPAP failure was defined as follows: (1) intubation before transport; (2) intubation during transport; (3) bag and mask ventilation during transport; (4) pulse oxygen saturation <88% despite appropriate O2 therapy (except for those with congenital heart disease); and (5) increase in transcutaneous CO2 (TCO2) >7 mmHg with TCO2 at the end of transport >60 mmHg. An upper limit of appropriate fraction of inspired oxygen (FIO2) was not set, because the study included infants with bronchiolitis, in whom a high FIO2 would be acceptable, providing blood gas analysis was satisfactory.
Data were entered into Microsoft Excel (Redmond, WA) and MINITAB 13 (MINITAB Inc, State College, PA). Comparisons between groups were made using the Mann-Whitney U test, 
2 test, and Fisher's exact test as appropriate. Analysis was undertaken for the whole group with secondary analyses undertaken on infants stratified by mode of transport. This study was performed as a quality assurance audit, and consequently ethics committee approval was not required (as per Australian National Health and Medical Research Council guidelines, available at www.nhmrc.gov.au/publications/_files/e46.pdf).
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RESULTS
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All of the data are given as median (range) unless stated otherwise. A total of 220 infants were either deemed suitable for NCPAP (n = 133) or already on NCPAP (n = 87) at the time of transport. Figure 1 indicates the outcomes for the 220 infants included. Thirteen infants (6%) were intubated before transport (4 transported by air and 9 by road; P value not significant), and reasons given were apneas on NCPAP (n = 3), worsening respiratory distress on NCPAP (n = 4), and failure to tolerate NCPAP (n = 4). For 2 infants the reasons for intubation were not clearly recorded. A total of 207 infants were transferred on a NCPAP of 7 cm H2O (5–10 cm H2O). There were no infants who were trialled on NCPAP and subsequently transferred in headbox oxygen. Four of the 207 infants transferred on NCPAP failed (based on the a priori criteria), all because of a rising TCO2 (1 transported by air and 3 by road; P value not significant), leaving 203 infants successfully transported on NCPAP. No patient required bag or mask ventilation or intubation during transport, and none had problems with oxygenation that warranted discontinuation of NCPAP. Of the 203 successfully transported infants, 161 (73%) did not require intubation (3 infants who met the NCPAP failure criteria were never intubated), 27 (13%) required intubation within 24 hours of arrival at receiving unit (1 infant who met the NCPAP failure criteria was also intubated within 24 hours of arrival), 4 (2%) were intubated >24 hours after arrival, and 11 (5%) were electively intubated for surgery. There was no record of any infant requiring immediate intubation on arrival at the receiving hospital.
There were 9 premature infants with respiratory distress syndrome (RDS) who were transported between tertiary perinatal centers because of bed shortages. Although the exact number of transfers between tertiary units was not available, it is likely that an additional 19 transfers between tertiary units occurred (14 patients with congenital heart disease, 4 with chronic lung disease and necrotizing enterocolitis, and 1 with gastroschisis).
Median gestational age (GA) at birth was 34 weeks (23–40 weeks), median age at transport was 1 day (0–175 days), and corrected GA at transport was 35 weeks (25–50 weeks). Median weight at transport was 2746 g (670–6100 g). Demographic characteristics are displayed in Table 1.
Table 2 summarizes the outcomes for the transported infants. FIO2 at end of transport was significantly lower than the FIO2 at start of transport (0.34 vs 0.45; 95% confidence interval: 0.05–0.12; P < .001). A total of 173 infants (79%) either had a fall or no change in FIO2 during transport. Only 9 infants (4%) had an increase in FIO2 >0.1, of whom only 4 had an increase in FIO2 >0.2 (0.29, 0.37, 0.43, and 0.45, respectively). Of these 9 infants, 5 were never intubated, 3 were intubated within 24 hours of arrival, and 1 was intubated electively for surgery. Of the 4 infants with a rise in FIO2 >0.2, 1 was intubated for surgery and the rest were never intubated. TCO2 and temperature were not significantly different at end of transport (45 mmHg vs 45 mmHg, P = .7, and 36.9°C vs 36.9°C, P = .23, respectively). TCO2 increased by >7 mmHg in 16 infants (7%), of whom 4 had a TCO2 at end of transport >60 mmHg (68, 68, 98, and 105 mmHg). Of these 16 infants, 4 were intubated (3 within 24 hours of arrival and 1 before transport). Of the 4 infants with a TCO2 increase and an end-of-transport TCO2 >60 mmHg, only 1 was subsequently intubated. This patient was an ex-premature infant with chronic lung disease and bronchiolitis who was taken on a 23-minute road transfer, during which time TCO2 increased from 60 to 105 mmHg and FIO2 increased from 0.60 to 0.75.
The majority of transfers were for RDS (135 infants [61%]). A small but significant number of transfers were for bronchiolitis (27 infants [12%]), chronic lung disease (19 infants [9%]), congenital heart disease (11 infants [5%]), and apnea (8 infants [4%]). Of the 135 infants transferred with RDS, 124 were <72 hours old at transport. A total of 134 infants (61%) were <37 weeks' corrected GA at transport. A total of 111 infants (50%) were preterm and <72 hours old at transport, and 32 infants (15%) were <72 hours old and <32 weeks' corrected GA at transport.
Compared with those who were not intubated within 7 days of transport (n = 164), the infants intubated within 24 hours of arrival had a higher FIO2 at start and end of transport and were less likely to have chronic lung disease (see Table 3). There were no other differences between these groups in their demographics or diagnosis.
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TABLE 3 Comparison of Characteristics of Infants Intubated Within 24 Hours of Arrival and Those Not Intubated Within 7 Days of Transport
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Air Versus Road Transport
A total of 190 infants (86%) were transported by road and 30 (14%) by air. Of those transported by air, 10 (33%) were by rotary wing and 20 (67%) by fixed wing. GA at birth was higher, age in days lower, and trip duration longer for those transported by air. Corrected GA at transport was not significantly different between the 2 groups. Chronic lung disease was less common as a primary diagnosis in the air group (0 of 30 vs 19 of 190; P = .05). There were no other significant differences between the demographic and clinical parameters of both groups (See Tables 1 and 2).
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DISCUSSION
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This is the largest published report describing the use of NCPAP as a method of respiratory support in infants requiring interhospital transport. It is the first report of the use of NCPAP in air-based transport and contains the first substantial description of the use of NCPAP in the transport of infants in the acute stage of RDS and other respiratory problems. Although this is a retrospective study, the data were collected prospectively. The NETS database is robust, and there were no patients on whom we had no available clinical notes. Unfortunately, blood gas analysis was not available for a sufficient number of patients for these data to be included in the analysis. Because the median transport duration was 33 minutes, our results may not be applicable to those with longer transport duration.
NCPAP seems safe for road transports, because only 4% infants had an increase in FIO2 >0.1, and 7% had an increase in TCO2 >7 mmHg with no infants requiring intubation or bag and mask ventilation during transport. Four infants met the failure criteria because of a TCO2 increase. Results of blood gas analysis to confirm the rise in TCO2 were not available. Given that only 1 of these infants subsequently required intubation, the use of this criterion is questionable and highlights the need for additional studies with blood gas analysis immediately before and after transport. With only 30 infants transported by air, additional studies are required to establish the safety of NCPAP in air transports. The reduction in FIO2 during transport confirms the efficacy of NCPAP. It is not surprising that some infants required intubation within 24 hours of arrival at the receiving hospital, because >90% of infants with RDS were transferred within 72 hours of birth. Clearly many of these infants are at risk of worsening RDS but given that the number of infants ultimately needing intubation is far smaller than the number with RDS transported, routine intubation before road transport cannot be justified. Routine intubation is undesirable for several reasons: the infant is subjected to an invasive procedure that is uncomfortable, the procedure would add significantly to the stabilization time, and unnecessary ventilation may result in preventable lung injury.
Neonatal retrieval by air is mainly limited to acutely unwell infants, and this accounts for the lower postnatal age at transport in the air transport group. Because of space restrictions, intubation in the plane or helicopter would be very difficult. The threshold for intubation is, therefore, lower for infants to be transported by air, with the majority of infants <32 weeks' gestation being intubated before transport (in addition, infants in this GA range would be candidates for surfactant therapy). The GA at transport is, thus, higher in the air group.
This is the first study of the use of NCPAP in transport to report follow-up of transported infants. In particular, intubation rates after such transports have not been reported previously. It is reassuring that 83% of infants did not require intubation within 24 hours of transport. The details of exactly when and why infants were intubated were not able to be ascertained from the available data, and a more detailed prospective study of outcome would be useful. The only significant differences between those intubated within 24 hours of arrival and those not intubated in the first week of life were a higher FIO2 and lower rate of chronic lung disease in the intubated group. It was not possible to predict those who required intubation. Prospective studies identifying the timing and reasons for intubation and including arterial blood gas analysis may help predict those infants requiring intubation. Future studies should also address other important outcome measures that we were unable to assess in this retrospective study, including duration of respiratory support, length of hospital stay, pneumothoraces, chronic lung disease, intraventricular hemorrhage, and death.
The intubation rate before transport of 13 (6%) of 220 infants was higher than that reported by Bomont and Cheema8 of 2 (2%) of 100. This likely reflects the lower postnatal age at transport and the increased number of infants with acute respiratory distress included our study.
Previous studies have almost exclusively reported ex-preterm stable infants transferred on NCPAP from a tertiary neonatal unit to a local special care infant unit. In the study by Bomont and Cheema,8 the mean age at transfer was 28 days, and 73 of 84 transfers by the emergency team were for repatriation of infants from a tertiary unit to a local hospital. Because the only units in Victoria managing infants on NCPAP are based in Melbourne, there are no return transfers of infants on NCPAP. The lack of significant numbers of district hospitals undertaking NCPAP also contributes to the relatively large number of infants with acute respiratory distress needing transfer on NCPAP. There is a trend toward increasing numbers of midwife-led delivery units without onsite pediatric staff in many countries, and, thus, there is likely to be an increasing need to transfer infants with acute respiratory distress to tertiary neonatal units. Transport with NCPAP may be an appropriate mode of respiratory support for some of these infants.
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CONCLUSION
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NCPAP is effective and has an acceptable safety margin for the road-based transportation of infants with acute respiratory distress. Air transport is feasible, but larger studies will be required to assess safety. Additional studies are warranted to identify the timing and reasons for the intubation of infants transported on NCPAP.
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FOOTNOTES
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Accepted Sep 5, 2007.
Address correspondence to Philip G. Murray, MRCPCH, Endocrine Sciences Research Group, 3rd Floor, Core Technology Facility, University of Manchester, Manchester, M13 9NT, United Kingdom. E-mail: Philip.Murray{at}manchester.ac.uk
The authors have indicated they have no financial relationships relevant to this article to disclose.
| What's Known on This Subject
The use of nasal continuous positive airway pressure during the road based transport of stable infants who are not in the acute stages of respiratory distress is feasible and safe.
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| What This Study Adds
Nasal continuous positive airway pressure seems to be effective and has an acceptable safety margin for the road based transport of neonates with acute respiratory distress. Air-based transfers on nasal continuous positive airway pressure are feasible.
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