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Measuring the performance of an inter-hospital transport service
  1. Padmanabhan Ramnarayan
  1. Padmanabhan Ramnarayan, Children’s Acute Transport Service (CATS), 44-B Bedford Row, London WC1R 4LL, UK; RamnaP{at}

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Most district general hospital (DGH) paediatricians will have referred critically ill children to a retrieval team at some point in their career. Inter-hospital transport services have developed in response to the centralisation of specialist services such as intensive care, with the aim of ensuring safe and rapid transport of sick children to tertiary centres.13 In many parts of the UK, retrievals are undertaken by staff despatched from the receiving intensive care unit (ICU), although dedicated regional transport teams, similar to those in North America and Australia, have also evolved recently for neonatal and paediatric transfers.46 Regional transport teams allow concentration of expertise and often serve as a single point of contact for immediate advice, information on an appropriate ICU bed and access to a specialist team.


Clinicians, commissioners and patients justifiably expect specialist services to deliver high quality, cost-effective care. While a number of quality indicators have been proposed for intensive care,7 there is currently no consensus on how the performance of an inter-hospital transport service can be measured. This is likely to be a significant drawback in the future. Ongoing changes in the NHS such as re-organisation of children’s emergency services, implementation of the recommendations of the Darzi Next Steps Review, and proliferation of managed clinical networks are all likely to greatly increase the need for safe and efficient patient transfer between ambulatory, secondary and tertiary care settings.811 Payment-by-results is also likely to generate greater competition between existing NHS providers and encourage the involvement of independent sector providers in patient transport.12 The absence of agreed key performance indicators or reference values means that transport teams will be unable to measure their own performance over time and commissioners will not be able to compare services or benchmark performance, raising the risk of significant variability in the quality of care provided by inter-hospital transport teams.

This review aims to describe potential measures by which the performance of inter-hospital transport services can be assessed, based on available evidence and current clinical practice at the Children’s Acute Transport Service (CATS), a busy regional retrieval service based in London. Standards for the structure and organisation of retrieval services have been published previously and are outside the scope of this review.13


A number of quality indicators covering aspects such as speed, safety, efficiency of resource utilisation and user satisfaction have been reported in the literature, and are currently used at CATS, to describe the clinical and operational performance of transport services. Table 1 provides a comprehensive list of such measures and relevant data from CATS.

Table 1 Summary of quality indicators described in inter-hospital transport and relevant CATS data


Adverse events

The reported frequency of adverse events during specialist neonatal and paediatric transport ranges from 4% to 36%, the wide range indicating significant variability between services in terms of the occurrence, identification and/or reporting of adverse events.1417 A list of life-threatening physiological and technical adverse events reported in some previous studies, and related CATS data, are shown in table 2.

Table 2 Key adverse events described to measure the safety of inter-hospital transport

At CATS, voluntary reporting by team members, combined with daily case review to prospectively identify adverse events from a comprehensive list of both major and minor physiological incidents, indicates an overall rate of 116 adverse events per 1000 transports. Adverse events are more frequent among patients with greater severity of illness.18

Ambulance accident rate

Road or air ambulance accidents during retrieval have been used as sentinel events, including at CATS, although the lack of a national register and the scarcity of published data may limit wider use of accident rates at the present time.19


Patient mortality has been suggested as a marker of retrieval performance. However, death in transit is a very rare event; only two patients have died so far during >6500 transports by the CATS team. Transport-related mortality is more appropriately measured from the point of team mobilisation until ICU admission or ICU/hospital discharge. Data from one specialist team indicated that overall mortality for retrieved patients (measured at the time of ICU discharge) was 8.5% to 12.0%.20 Mortality for CATS retrievals (from team mobilisation to the end of the first 24 h on ICU) is ∼8%.

Unplanned re-transfers

Unplanned re-transfer to a higher level of specialist care soon after the index transfer may indicate incorrect initial triage of patient condition or poor quality of care during transport, akin to unplanned readmissions shortly after ICU discharge.21 Inter-ICU transfers have been associated with higher risk-adjusted mortality in adults.22 Recent CATS data show that unplanned inter-ICU transfers occur in 1.2% of cases (a median 14 h after index transfer), mainly for further specialist care such as extracorporeal membrane oxygenation (ECMO) or cardiac surgery.

Urgent interventions on ICU

The need for urgent vital interventions (eg, cardiopulmonary resuscitation, endotracheal intubation or central venous access) in the first hour after ICU admission may indicate inadequate stabilisation during retrieval. Along similar lines, the adequacy of stabilisation performed by the transport team may be indicated by repeated measurement of physiological scores at different time points during the transfer.23 24


Referring clinicians frequently rate the rapid availability of a retrieval team as an important requirement.25 Median retrieval response times (referral-to-patient bedside) of 75–100 min have been cited in the literature, although this varies significantly depending on the geographical region served (urban vs rural) and the model of service delivery (dedicated transport team vs team with concurrent ICU duties).4 15 Figure 1 graphically illustrates how various operational time intervals are defined, while table 3 shows typical times drawn from CATS and other published data.

Figure 1

Discrete events and operational time intervals during a typical retrieval. DGH, district general hospital; ICU, intensive care unit.

Table 3 Median operational time intervals reported by various transport services

Efficiency of resource use

Resource utilisation can be optimised by avoiding unnecessary transports as well as maximising team availability.

Incorrect triage at referral

Underestimating the acuity of illness may lead to an intensive care patient being refused at first referral, only to require transport subsequently. Although no specific data exist in the literature, 4% of referrals classified as non-ICU at initial triage at CATS subsequently require transfer to an ICU within 72 h.

Preventing inappropriate ICU transfer

Efficient triage and effective advice may result in an ICU referral resolving with telephone discussion, preventing unnecessary mobilisation of a transport team.16


Unavailability of a transport team for an appropriate referral can be used to indicate adequacy of service provision. Team availability can often be maximised by using a combination of physicians and advanced nurse practitioners to staff the service.26 The CATS team passes on 5% of appropriate referrals each year to other retrieval services due to team unavailability.


One of the barriers to the measurement of quality of care in intensive care transport has been the lack of established standards and uniform data. National retrieval standards are expected to form part of the latest version of the Paediatric Intensive Care Society (PICS UK) standards, although it is still unclear if their primary focus will remain the structure and organisation of retrieval services (inputs) rather than the measurement of performance (outputs). A national retrieval audit dataset has also recently been agreed as part of the Paediatric Intensive Care Audit Network (PICANet), although data collection has yet to commence. PICANet data will be crucial to assess the current performance of teams across the UK as well as to promote clinical consensus on key performance indicators.

Despite these encouraging initiatives, numerous challenges remain. Performance indicators generally involve either the assessment of process measures (eg, mobilisation time) or patient outcomes (eg, adverse events or mortality). Process measures depend heavily on how a service is configured and delivered – it may be difficult to mobilise a team immediately if ICU staff are simultaneously involved in caring for inpatients as well as covering retrievals, and the rate of refusals may be higher in such a setting. Standardisation of key processes (such as dedicated retrieval team and ambulance availability; consultant-led service; single point of contact for advice, bed allocation and retrieval; clear guidelines for optimal stabilisation; and uniform methodology and template for adverse event reporting) is crucial to ensure valid comparison between different transport teams. Clinicians and commissioners need to incorporate these goals into service level agreements and undertake regular reviews of performance using clear measurable standards. The process of benchmarking may itself form a powerful driver for such standardisation.

Similarly, comparison of patient outcomes is limited by the absence of widely accepted pre-transport scores to adjust for differences in severity of illness and case-mix. Although such scores have been developed for specific groups such as retrieved newborns, they are not used widely.20 27 Existing risk-adjustment scores used for ICU patients, such as the Paediatric Index of Mortality (PIM-2) and Clinical Risk Index for Babies (CRIB) were not specifically developed for retrieved patients, and use physiological data collected at the time of first face-to-face contact with an intensive care team rather than at initial referral to a retrieval service.28 29 Interventions by the retrieval team may lead to changes in physiological scores; moreover, the majority of vital interventions are now usually undertaken by staff at the referring hospital as a result of active telephone advice provided by the transport service, even before the arrival of the retrieval team.30 Further research into developing a widely accepted pre-transport severity of illness score is crucial for valid comparison of patient outcomes from different retrieval teams. Finally, international consensus on the terminology involving retrieval time intervals (sometimes used synonymously and in overlapping fashion, eg, despatch time, launch time, tasking time, activation time and mobilisation time) is urgently required, similar to the Utstein-style guidelines for resuscitation research.31 32


Inter-hospital transport services will play a vital and ever-increasing role in a centralised model of acute specialist care in the future NHS. Greater scrutiny of quality of care, and the need for transparency, will inevitably lead to transport services being compared against each other as well as external standards. Without robust indicators, it will be impossible to monitor performance, even within a single service, or to establish benchmarking standards. In this review, a number of potential key performance indicators, the challenges involved in their routine use, and future directions in the measurement of quality of care have been described. The universal adoption of performance indicators hinges on the standardisation of key clinical and operational processes involved in inter-hospital transport.



  • Competing interests: None.