Acute bronchiolitis (AB) is a form of lower respiratory tract infection of viral etiology characteristic of the pediatric age group. This disease is one of the leading reasons for hospital admission in infants and young children, and up to 10% of these patients require admission to the pediatric intensive care unit (PICU).1 In out-of-hospital settings, it is associated with a high frequency of transport of critically ill pediatric patients, with wide variation in severity.2 At present, there is no specific treatment for AB, and its management is based on providing respiratory support adapted to the severity of disease.

In patients with severe AB, the use of noninvasive ventilation (NIV) in the PICU has been found to improve respiratory distress and reduce the need of invasive mechanical ventilation, so it has become widespread.3,4 A similar trend has been observed in pediatric interhospital transport, and several studies suggest that its use is safe and feasible in this context.5,6 Moreover, there is evidence that early initiation of NIV is associated with a decrease in severity scores and an improvement in vital signs during interhospital transport7 without an increase in the rate of emergency intubation during transport.8,9

The aim of our study was to describe and compare the characteristics of patients with AB undergoing interhospital transport with NIV, initiated by either the pediatric transport team (PTT) or the sending hospital (SH).

We conducted a single-center retrospective and observational study in a tertiary care hospital that has a specialized pediatric ground transport team comprised of an emergency medical technician, a pediatric nurse and an intensive care pediatrician. In addition, the medical emergency response coordinating center has an intensive care pediatrician on staff that communicates with both the SH and the PTT and can provide guidance to both during transport.

The study was conducted between January 2021 and March 2024. We included all patients aged less than 24 months with a diagnosis of AB transported from one hospital to another by the PTT in whom NIV was initiated at some point during stabilization or transport and who received NIV during transport. The transports originated in one of 37 possible sending hospitals and ended at one of the 8 tertiary care hospitals that have a PICU in Catalonia.

We defined AB as the first episode of lower respiratory tract infection of viral etiology in a patient aged less than 24 months preceded by a viral upper respiratory prodrome.10

During transport, NIV was delivered with the Hamilton T1 respirator (Hamilton Medical AG, Switzerland) to both pediatric and neonatal patients. The interfaces were face masks or, in some neonates, nasal masks, depending on the fit on the patient.

We excluded patients with a personal history of AB, a diagnosis of respiratory disease in the neonatal period or other respiratory diseases that did not meet the criteria for AB. We also excluded transports ending but not starting in a hospital (from primary care centers), that were cancelled or in which NIV was not the modality used for respiratory support.

The study was approved by the Ethics Committee of the hospital where it was conducted.

During the study period, 2327 patients underwent interhospital transport, of who 492 (21.1%) had a diagnosis of AB and 263 were included in the study (Fig. 1). In 119 cases (45.2%), NIV was initiated by the SH and in 144 (54.8%) it was not initiated until the arrival of the PTT. Only 2 patients in whom NIV was initiated by the SH required OTI once the PTT arrived for stabilization before transport, and they were excluded from the analysis. Table 1 presents the main clinical characteristics of the sample. The NIV modality used during transport was bilevel positive airway pressure (BiPAP) in most patients (n=259; 98.5%) and continuous positive airway pressure (CPAP) with a nasal interface in only four. When NIV was initiated by the SH, the interface was a face mask in most cases (102/119; 85.7%), and a nasal mask in only 17 (14.3%), which was switched to a face mask for transport in 13 cases.

Figure 1.

Flow diagram of sample selection.

NIV, noninvasive ventilation; OTI, orotracheal intubation; PTT, pediatric transport team.

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We found significant differences in the BROSJOD severity scores (Fig. 2). Initiation of NIV before activation of the PTT was associated with lower scores on arrival of the PTT to the SH, with a median score of 8 (IQR, 6–10) compared to patients in which initiation of NIV was deferred until the arrival of the PTT, with a median score of 11 (IQR, 10–12) (P<0.0001). When it came to the severity score at the end of transport, the median was 8 in the group with initiation of NIV by the SH compared to 7 (IQR, 6–8) in the other group, with a P value that neared the threshold of significance (P=0.052). The PTT was unable to record the BROSJOD score at the SH in 14 patients (5.3%) and on arrival to the RH in 15 patients (5.7%).

Figure 2.

Comparison of severity scale in interhospital transport. The group of patients with initiation of NIV by the SH is to the right, and the group with initiation by the transport team the left. The boxes span the interquartile range (IQR) and the line in the middle of the box the median. The whiskers extend to the minimum and maximum values within 1.5 times the IQR. Values outside this range were treated as outliers.

BROSJOD, Bronchiolitis Score of Sant Joan de Déu; NIV, noninvasive ventilation; RH, receiving hospital; SH, sending hospital.

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In the analysis of the stabilization time, we identified several outliers that we explored individually. In one patient in whom NIV was initiated by the SH, the stabilization time was 126min, and the delay in transport was due to waiting for the arrival of another unit to transport an additional patient. Since the reason for the delay was unrelated to the patient’s transport, this case was excluded from the analysis. Initiation of NIV by the PTT was significantly associated with a longer stabilization time, with a median of 47min (IQR, 40–56) compared to 40 (IQR, 33.3–47) in patients in whom NIV was initiated beforehand (P<0.0001) (Fig. 3). Furthermore, the stabilization time was weakly correlated to the severity score at the time of arrival of the PTT to the SH (r=0.21; P=0.001). On the other hand, the stabilization time was not associated with the need for sedation or the occurrence of incidents during transport.

Figure 3.

Comparison of stabilization time in interhospital transport. The boxes span the interquartile range (IQR) and the line in the middle of the box the median. The whiskers extend to the minimum and maximum values within 1.5 times the IQR. Values outside this range were treated as outliers.

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We found an association between the initiation of NIV by the SH and a lower fraction of inspired oxygen (FiO2), both at the beginning and at the end of transport, compared to the group with initiation of NIV by the PTT. In patients in whom NIV was initiated by the SH, the median FiO2 was 0.3 (IQR, 0.25–0.35) at the beginning of transport and 0.25 (IQR, 0.25–0.3) at the end, while in the group with initiation of NIV by the PTT the corresponding median FiO2 values were 0.35 (IQR, 0.3–0.45) and 0.3 (IQR, 0.25–0.35), respectively. These differences were statistically significant (P<0.0001 and P<0.002, respectively). When it came to respiratory parameters, we did not find differences in the peak inspiratory pressure (PIP) and positive-end expiratory pressure (PEEP) between the groups.

Incidents related to NIV were documented in 37 transports (14.1%), with a higher frequency in the group with NIV initiation by the SH compared to the group with initiation by the PTT (25 [21%] vs 12 [8.3%]; P=0.003). The most frequent incidents in both groups were leaks (14/37; 37.8%). Table 2 presents the distribution of incidents by type and the differences between groups. There was one case of pneumothorax recorded by the PTT on arrival to the SH that did not require pleural drainage until the second day of hospitalization in the RH.

As regards follow-up at the RH, 32 patients (12.2%) required OTI within 72h of arrival, with no differences between groups (11.8% in the group of NIV initiated by the SH vs 12.5% in the group of NIV initiated by PTT; P=0.856). There were no deaths during the management of the patient by the PTT nor reported by the RH in the telephonic follow-up 3 days after transport.

Fig. 4 reflects the progressive increase in the percentage of patients in whom NIV was initiated by the SH over the studied time intervals.

Figure 4.

Longitudinal trend in the initiation of NIV by SH over consecutive epidemic seasons. Results expressed as the percentage distribution of patients based on whether NIV was initiated by the sending hospital by epidemic season.

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The findings of our study show that patients with a diagnosis of severe AB who required interhospital transport with NIV benefitted from early initiation of noninvasive respiratory support by staff at SHs. However, we also identified a potential increase in the frequency of minor NIV-related incidents in the group of patients in whom NIV had been initiated by the SH.

Noninvasive ventilation has been found to reduce severity scores and signs of respiratory distress, both in the PICU setting4,12 and in patient transport, as observed in the study conducted by Manso Ruiz de la Cuesta et al.7 Our study yielded similar results, and we also found that early initiation of NIV by the SH was associated with significantly lower severity scores, which were in the moderate as opposed to the severe range by the time of arrival of the PTT to the SH. We found a similar trend at the time of arrival to the RH, with P values that neared the threshold of significance, although the difference may not be clinically relevant, since both groups had scores in the moderate range. This could be due to the short time that the PTT is in contact with the patient, with a median duration of less than 90min, which may be too short to appreciate improvement by the end of transport.

Early initiation of NIV by the SH was also associated with lower oxygen requirements (FiO2), both during the management of the patient by the PTT at the SH and on arrival to the RH, which was consistent with previous studies in which NIV was found to reduce oxygen requirements from 2h of its initiation in patients with bronchiolitis13 and other diseases.14,15

The stabilization time in the group in which NIV was initiated by the PTT was similar to the one reported by Millán et al.,16 although their study did not take into account the specific timing of NIV initiation during the transport process. However, we ought to highlight that in our sample, initiation of NIV by the SH was associated with a shorter stabilization time.

In a previous study, Borrows et al.17 concluded that a longer stabilization time was not associated with poorer patient outcomes in the context of interhospital transport, which was consistent with our results, as there were no deaths nor any differences in the proportion of OTI between the two groups, and we also found that longer stabilization times were not associated with poorer outcomes in terms of mortality during transport or in the 3 subsequent days. Notwithstanding, we found a reduction in stabilization time, which, combined with the fact that patients in whom NIV was initiated earlier in the SH had lower FiO2 requirements and more favorable severity scores, was associated with a better clinical condition during transport and quicker arrival to the RH.

The use of NIV during pediatric ground transport has proven safe and feasible in several previous studies.15,16,18,19 This was also the case of our study, in which we only identified a single serious incident during the transport of patients with this support modality, independently of the timing of its initiation. Furthermore, none of the patients required escalation of respiratory support during transport.

The most frequent minor incidents in both groups were leaks and patient-ventilator asynchrony, in agreement with previous studies in adult patients.20,21 These adverse events were more frequent in patients in whom NIV had been initiated in the SH.

We also observed a substantial increase in the percentage of transports in which NIV had been initiated by the SH, from 20% to nearly 60% of pediatric transports over the 3-year period. This hints at a growing trend toward initiation of NIV while patients await transport. However, we ought to note that this procedure is not free of risks, especially when performed by professionals with less experience in the set up and use of these devices.

On the other hand, we found a reduction in the number of patient transports during the recent 2023–2024 epidemic season compared to previous periods. This decrease could be related to the administration of nirsevimab, a monoclonal antibody that has contributed to reducing hospital admissions due to AB caused by respiratory syncytial virus (RSV).22

All of the above, added to the findings of other studies in relation to NIV and patient transport,8,15,18 underscores the need for more in-depth training in the health care staff of these hospitals in order to minimize incidents an optimize the use of these devices. In addition, although we did not analyze its impact in this study, we want to highlight the role of the staff pediatrician in medical emergency coordination centers, who can offer telephonic telemedicine support to SHs, a practice that has proven useful in pediatric transport.23,24

To our knowledge, few published studies have analyzed the use of NIV in transport after its initiation by the staff of lower-level SHs (below tertiary care), so the findings of this study may be very relevant to clinical practice. We found that early initiation of NIV by the SH was associated with favorable outcomes without an associated increase in serious complications related to this respiratory support modality. We also found a reduction in the stabilization time, something that would allow quicker access to intensive care at the PICU while increasing the availability of pediatric transport units, which are a limited resource in high demand during epidemic seasons.

One of the limitations of our study is that it was conducted in a single center, which may limit the external validity of our findings, even if they are significant. This is compounded by the heterogeneity of PTTs in the rest of Spain and at the international level. There is also its retrospective design, which may limit the generalizability of the results, since there was a risk of selection bias and the sample of SHs was not homogeneous. Another limitation is that there were no data on the reasons why SHs did not initiate noninvasive respiratory support before transport (whether it was a lack of technological or human resources or a lack of knowledge on the use of NIV systems), which could be another source of bias.

In the future, it would be useful to conduct studies with a prospective multicenter design and in other geographical areas to determine whether the findings of the study can be generalized.

In our study of patients with AB who required interhospital transport with NIV, we observed an association between early initiation of noninvasive respiratory support and better clinical condition during transport, a finding that can help optimize the use of pediatric transport team resources. Training of the staff of SHs in the use of NIV could reduce the incidence of complications and guarantee the benefits associated to this modality.

This research project did not receive specific financial support from funding agencies in the public, private or not-for-profit sectors.