Paediatric transport involves delivering care to patients who require transfer to a health care facility that can provide definitive treatment. Interhospital ground transport can increase the risk associated with the patient’s current disease. Critical events can occur in up to 15% of paediatric transports.1

The safety of paediatric transport by ground ambulance varies between emergency medical services systems. It is essential to ensure the stability of the patient before transport, given the difficulty of performing procedures in transit in the ambulance setting.2 In addition, the transport of patients aged less than 1 year is further complicated due to their higher risk of instability and the narrow range of equipment and supplies available for this population.3,4

Acute respiratory failure (ARF) is a major cause of morbidity and mortality in the paediatric age group and is one of the leading causes of admission to paediatric intensive care units (PICUs). It is also a common reason for transport to tertiary health care facilities.2,3,5

Non-invasive ventilation (NIV) has emerged as a powerful tool for the emergency management of ARF in paediatric transport. A restrictive protocol, with careful selection to exclude patients with moderate to severe acute respiratory distress syndrome (ARDS), and a well-trained retrieval team are essential for correct use of NIV during transport.6 There are several studies in the literature of the use of NIV during patient transport, but none comparing different modes of ventilatory support during transport. The aim of our study was to compare the use of continuous positive airway pressure (CPAP) versus oxygen therapy during transport of infants with ARF and their disease course and outcome in the PICU.

The study was approved by the Clinical Research Ethics Committee of the Health Care Area of the main hospital in the study.

In the 10 years under study, the total number of transported patients that met the inclusion criteria was 110:71 transported with CPAP and 39 with oxygen therapy. Table 2 compares the characteristics of these groups. Prematurity was the most frequent underlying condition (61.8%), and bronchiolitis the most frequent cause of ARF (81.8%). We found a difference in the proportion of patients that had bronchiolitis or wheezing episodes between the CPAP and the oxygen therapy groups (P = .02).

In the CPAP group, the system used for delivery of CPAP during transport was the Boussignac® in 67.6% of patients (n = 48), the Oxylog 3000 plus® in 22.5% (n = 16), the Vivo 40® in 8.5% (n = 6) and the Elisée 150® in 1.4% (n = 1). The median pressure of CPAP was 7 cmH2O (interquartile range, 6–7 cmH2O). Only two infants in the CPAP group needed sedation to facilitate the adaptation to respiratory support, for which they were given midazolam. The use of nasogastric tubes was more frequent in the CPAP group compared to the oxygen therapy group (80.3% vs 2.6%; P < .001).

Fig. 1 and Table 3 show the differences found in the univariate analysis of the clinical and blood gas variables measured before transfer and on arrival to the PICU by type of respiratory support used during transport. The SF ratio was calculated at the referring hospital in 66.4% of patients (n = 73), but only in 41.8% (n = 46) at the PICU. Blood gas tests were performed in 87.3% of patients (n = 96) at the referring hospital, compared to 53.1% (n = 59) in the PICU.

Figure 1.

Box plots of clinical variables in CPAP and oxygen therapy groups: before transport (left) and in PICU (right).

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The specific multivariate models, which included the mode of respiratory support used during transport (CPAP vs oxygen therapy), clinical parameters, the partial pressure of carbon dioxide (pCO2), FiO2 and SF ratio in the PICU (controlled for their values prior to transfer), showed that CPAP only achieved significant decreases in the Wood-Downes score (β = –1.08; 95% CI = –1.76 to – 0.40; P = .002) and the heart rate (β = –19.64; 95% CI = –28.46 to –10.81; P < .001).

None of the patients required a change in the mode of respiratory support or endotracheal intubation during interhospital transport. Table 4 compares PICU outcomes by mode of support, and Fig. 2 presents the Kaplan–Meier curves of the duration of MV and length of stay in PICU. In our sample, the early use of CPAP prior to transfer was associated with a similar intubation rate (7.1% vs 5.1%; P = .689). However, the need for invasive MV and for BiPAP within 6 h of admission to the PICU were lower in the CPAP group: 40 % vs 100% (P = .092) and 69.2% vs 100% (P = .04), respectively. In our study, the mortality was limited to 1 patient in the oxygen therapy group that required invasive MV and died as a result of the underlying disease, a polymalformative syndrome.

Figure 2.

Kaplan–Meier curves: duration of MV and length of stay in PICU.

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The causes of ARF in our sample were similar to those reported in other studies conducted in patients admitted to the PICU that required support with NIV and invasive MV.6,16 We ought to highlight a higher proportion of patients with bronchiolitis in our study, a difference that could be explained by the age of less than 1 year in our sample.17

The proportion of patients with underlying disease in the cohort (30.9%) was lower compared to other samples of patients requiring NIV in the PICU setting described in the literature: 43% (Abadesso et al.)16 and 61% (Mayordomo-Colunga et al.).18 Prematurity was the most frequent underlying condition, and its frequency was similar compared to other case series of patients with bronchiolitis requiring admission to the PICU.17,19

Initially, the use of NIV in paediatric patients was restricted to units with extensively trained staff, but in recent years it has begun to be used in settings with fewer resources for monitoring, such as in interhospital transport.6,20,21 In our case series, the helmet interface had been chosen based on published evidence on its use in infants with ARF,22–24 in addition to being more comfortable25 and easy adaption.

The mode of ventilation used in our case series was CPAP. This NIV mode is indicated for initiation of ventilatory support in infants aged less than 3 months and in patients with bronchiolitis or apnoea.26 These complaints were frequent reasons for interhospital transport in our sample. Continuous positive airway pressure is widely used because it is not as technically challenging as bilevel positive airway pressure (BiPAP) when it comes to achieving patient-ventilator synchrony. In our study, pressure delivered with CPAP was 7 cmH2O, in agreement with previous works.20,27 We ought to highlight that in patients with bronchiolitis and hypercapnic respiratory failure, a CPAP pressure of 7 cmH2O is associated with an improvement in respiratory effort and better short-term outcomes.

Evidence from multiple studies shows that the use of NIV achieves an improvement in the Wood-Downes score.14,15 Milési et al. reported a greater decrease in the m-WCAS score with the use of CPAP versus conventional oxygen therapy in infants with bronchiolitis admitted to the PICU (–2.4 ± 1.05 vs –0.5 ± 1.3; P = .03).13 In addition to a reduction in the severity score, our study found an improvement in heart rate and a decrease in the respiratory rate in the PICU when NIV was used for respiratory support during transport. Several studies comparing NIV with oxygen therapy in paediatric patients in the PICU have described improvements in clinical parameters.28,29 In a study of infants with bronchiolitis that required CPAP during transport, Fleming et al. found a lower FiO2 on arrival to PICU (0.62 vs 0.4; P < .001).20 We did not observe this trend. In a comparison of CPAP with standard treatment in patients with bronchiolitis, Thia et al. observed a greater improvement in pCO2 in the CPAP group (–1.35 vs –0.53 kPa; P <  .01).30 This result was less clear in our study, possibly due to the shorter time of observation.

In our study, none of the patients required intubation during transport, which was consistent with the findings of other authors, with a reported incidence of intubation of 0%–1%.6,20,21 In our sample, 6.4% of the patients were eventually treated with invasive MV, but the rate reported in the literature in patients initially treated with NIV is of 20%–22%.6,16 This difference may be explained by the use of BiPAP in our sample, as it has been reported that the use of BiPAP reduces the intubation rate to 8%.31 In our study, BiPAP was used in 33.6% of patients. Several studies have demonstrated a reduction of intubation rates, need of MV and incidence of complications with use of NIV.29,32 The need for MV or BiPAP within 6 first hours of admission to the PICU was lower in the CPAP group. These differences could be related to the early improvement achieved with CPAP, although the outcomes of patients in the PICU cannot be attributed to this factor alone. The fact that 30.8% of patients receiving support with oxygen therapy during transport continue with this mode of support in the PICU may be due to the lower availability and development of NIV in the early years following the introduction of this technique in the PICUs of the health care areas included in the study.

The mortality of patients with ARF admitted to the PICU reported in the literature ranges between 1.3% and 1.6%,16,17 which is comparable to the mortality found in our study (0.7%).

There are several limitations to our study. One is its retrospective design. Another is the amount of missing data, which was greatest for the SF ratio, followed by blood gas parameters. The groups compared were not homogeneous. In addition, the period under study was long (10 years), and during this time there were changes in clinical protocols and improvements in the equipment used to deliver NIV. These changes may have been a source of bias in our results.

We did not analyse the FiO2 delivered during transport because most ventilators used for NIV can only provide a limited range of FiO2. It is important to be aware that this limiting factor could indirectly influence in clinical and blood gas parameters in the PICU as well as in patient outcomes.

Our study included patients referred from 2 first-level hospitals. There was variation between the corresponding health care areas as regards the material resources used and the duration of transport to the PICU. The differences in the theoretical knowledge and practical skills of the different health care teams were minimal. All interventions conformed to standardised protocols and the training offered by the Respiratory Work Group of the Sociedad Española de Cuidados Intensivos Pediátricos (Spanish Society of Paediatric Intensive Care). We believe that the results of the study are independent of the health care area and thus could be extrapolated to other areas in Spain.

Prospective multicentre studies are needed to overcome the limitations of our study.

Early delivery of CPAP to infants with ARF was a safe measure of respiratory support during interhospital transport. In this framework, the use of CPAP was associated with an improvements in the modified Wood-Downes score and the heart rate compared to oxygen therapy.

The authors declare no conflicts of interest.