Abstract
Objective
A 45‐min interval from injury to intubation has been proposed as a performance indicator for severe trauma patient management. In the Sydney pre‐hospital system a previous change in case identification systems was associated with activation delay. We aimed to determine if this also decreased the proportion of patients intubated within this benchmark.
Methods
Retrospective cohort study of patients intubated by a helicopter emergency medical service (HEMS) over two time periods. Period 1 dispatch was via HEMS crew directly screening the computerised dispatch system, and period 2 was via paramedics in a central control room. Times from emergency call to intubation were compared.
Results
In the HEMS crew screening period 46/58 (79.31%) intubations met the target, compared with 137/314 (43.6%) in the central control period (P < 0.001). The median (interquartile range) time to intubation in the direct crew screening period was 33 (25–41) min, versus the central control period at 47 (38–60) min (P < 0.001).
On multivariate modelling, distance to the scene was related to time to intubation (P < 0.001; Incident Rate Ratio = 1.018, 95% confidence interval 1.015–1.020) as was dispatch system, entrapment/access difficulty and indication for intubation (all P < 0.001).
Conclusions
Time from emergency call to intubation was significantly shorter in the HEMS screening period where all non‐trapped cases less than 50 km distant were intubated within the 45‐min benchmark. There was no distance where intubation within 45 min could be assured for non‐trapped patients in the central control period due to dispatch delays.
Keywords: intubation, key performance indicator, physician, pre‐hospital, response time
Intubation within 45 min of injury has been proposed as a pre‐hospital performance standard. We compared performance of two pre‐hospital case identification systems: direct screening by helicopter emergency medical service (HEMS) crew, or paramedics in a central control room. HEMS crew screening was associated with significantly higher standard compliance.
Key findings.
Intubation within 45 min of injury has been proposed as a performance standard in pre‐hospital care with a previous Australian retrieval service study indicating distance as the major compliance impediment.
We compared performance against this standard between two case identification systems: direct screening by HEMS crew, or paramedics in a central control room.
As with the previous Australian study we found that distance to the scene was strongly associated with benchmark compliance. However, the case identification systems also significantly affected the proportion of complying patients with dispatch delays being the major reason for non‐compliance within 50 km of the operations base.
Introduction
Pre‐hospital advanced airway management is routinely provided in many Australian jurisdictions for severe head injury and threatened airway/ventilation due to trauma. International guidelines provide recommendations and performance standards for pre‐hospital RSI. 1 , 2 , 3 Among such standards is the National Institute for Health and Care Excellence (NICE) guidance which recommends RSI as soon as possible and within 45 min of the call to emergency services for patients who cannot maintain their airway and/or ventilation. 4 Although the NICE guidelines are from the UK, services such as the South Australian retrieval system have published their performance relative to this standard as no equivalent Australian standard exists. 5
Achieving this 45‐min RSI window is challenging, particularly in rural and remote regions with prolonged travel distances. 5 , 6 , 7 In the analysis of the statewide South Australian system, only 37% of patients were intubated within 45 min of activation of the retrieval team, mostly due to distance from the service base. This prior study did not evaluate performance from time of call to emergency services as per the NICE guidelines. Instead, it was assumed that the case identification and dispatch decision time was negligible, although supporting data was not provided.
Previous data from the Sydney pre‐hospital system indicates dispatch times can be prolonged and vary with case identification system, 8 specifically before and after changes to the case identification system in March 2011 associated with conclusion of recruitment for the Head Injury Retrieval Trial (HIRT). 8 , 9 During the trial cases were identified by the trial team directly monitoring the computed‐assisted dispatch (CAD) system of the NSW Ambulance Service from their operations base. At trial conclusion access to the CAD was withdrawn and case identification was conducted exclusively by a dedicated paramedic (known as the Rapid Launch Trauma Coordinator – RLTC) monitoring the CAD in a central control room. A previous study of this system change in severely injured children noted a marked increase in time for severely injured children to arrive at a paediatric trauma centre in the post‐trial period, although intubation performance was not examined. 8
We hypothesise this change to the case identification system in Sydney had a similar effect on time to pre‐hospital intubation. We aimed to compare the time to intubation from the emergency call in the HIRT and RLTC periods and hence the proportion of intubations that comply with the NICE guideline.
Methods
Study design
This is a single‐centre, retrospective cohort study following the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) Statement guidelines. 10 Study approval was by the Nepean Blue Mountains Human Research Ethics Committee reference 2024/ETH00309.
Setting
The CareFlight Rapid Response Helicopter (CRRH) service is a specialist metropolitan pre‐hospital physician‐staffed trauma service. The CRRH was the service established for the purpose of operating the HIRT which transitioned to service provision at conclusion of trial recruitment. They respond to predominantly trauma cases, and medical emergencies as directed. Crew composition, experience levels and training programmes have been previously described. 11 The service area extends approximately 100 km (54 nautical miles) from their operations base located near to the demographic centre of Sydney population.
During the HIRT, a member of the CRRH team monitored the NSW Ambulance CAD via a weblink to identify appropriate cases. 9 , 12 Severely injured children were also included although these responses were outside of the trial. 8 , 13 , 14
In the post‐HIRT period beyond March 2011, the RLTC tasked the service according to the Ambulance Service T1 protocol for severe trauma with additional consideration for cases that may require helicopter access due to distance or poor road access. All responses in both time periods were by helicopter.
Study population
The present study includes all patients undergoing RSI during CRRH pre‐hospital missions in the following time windows:
HIRT period: August 2009 to March 2011 when trial recruitment ceased, and the case identification system changed. The period commences in August 2009 as the recording of intubation time in the clinical record commenced at this time. The team had direct access to the CAD and recorded the time of the first key stroke (FKS) of the emergency call from the public, that is, the time of call first pickup by control centre operators.
RLTC period: January 2014 to December 2022. This period commences in January 2014 as recording of the emergency ‘000’ call time in the CareFlight retrieval database commenced in this month. This data was collected from the mobile data terminals (MDTs) in road ambulances responded in parallel. The ‘Time booked’ was utilised as the FKS time is not available on the MDT, and the Ambulance Service declined to provide FKS data directly to the CRRH team. Time booked is generally within a minute of the FKS time and occurs when enough data has been obtained to prioritise the case and place it in the queue for vehicle allocation. Hence it forms a reasonable approximation for the FKS time.
Data sources
Data were extracted from the CareNet Retrieval database, the CareFlight Airway Registry as well as the contemporaneously completed treatment record.
Main outcome measures
The primary outcome measure was the time to perform pre‐hospital emergency RSI from the emergency call, and the proportion of patients in which this was achieved within 45 min.
Secondary outcome variables
Secondary outcomes include:
Time from emergency call to team departing base (activation interval). Time to team notification could not be utilised as during the HIRT period the HEMS team identified their own cases, and the time of activation decision was not recorded. The time of departure from the base was routinely recorded in both time periods however.
Travel time from the base to the moment of making physical contact with the patient (response interval). This includes the time taken to transit to the landing zone, travel by foot or ground vehicle to the patient location, then access the patient which can be prolonged in industrial incidents, gaols, etc.
Time from physical patient contact to intubation (contact to intubation interval).
Statistical analysis
Descriptive analyses were used to examine differences in the distribution of the characteristics of the study population during the two periods. To examine whether there is a statistically significant differences in proportion of patients complying with the guideline target between the two periods χ 2 tests were utilised when appropriate with Bonferroni adjustments. Given non‐parametric distribution on the overall time to intubation, the Mann–Whitney U test was used to examine differences in distribution of time between the dispatch systems. Secondary outcome intervals were similarly compared using Mann–Whitney U tests. Finally, multivariable negative binomial models accounting for over‐dispersion were used to examine the overall time to intubation and the interval from contact to intubation between the periods. Analyses were undertaken using SPSS 28 (IBM Corp, Armonk, NY, USA).
Results
During the HIRT period, there were 341 patient contacts and after exclusions, 58 cases included in the analysis. During the RLTC period, there were 2243 patient contacts, with 314 cases available for analysis after exclusions including 99 cases due to FKS time (Fig. S1). During the RLTC period the time from dispatch call to departing the base was median 3 (interquartile range [IQR] 2–4) min.
Characteristics of the patients, intubations and mission data are presented in Table 1.
TABLE 1.
Group differences by characteristics
| Characteristic | Case identification systems | Difference between groups | |
|---|---|---|---|
| HIRT (n = 58) | RLTC (n = 314) | ||
| Age (year), mean (SD) | 34.55 (24.58) | 40.55 (22.41) | 0.116 |
| Male, n (%) | 41 (70.60) | 239 (82.48) | |
| Entrapment or access difficulty present, n (%) | 18 (31.03) | 34 (10.83) | <0.001 |
| Distance (nautical miles†), median (IQR) | 11.69 (7.22–15.68) | 11.68 (6.20–20.64) | 0.574 |
| Indication for intubation, n (%) | 0.039 | ||
| Head injury | 45 (77.6) | 186 (59.2) | * |
| Neck/facial injury or burn/inhalation injury | 1 (1.7) | 32 10.2) | * |
| Altered mental state | 3 (5.2) | 19 (6.1) | |
| Other | 9 (15.5) | 77 (24.5) | |
| Physiology before intubation | |||
| Heart rate, mean (SD) | 100.70 (32.4) | 102.89 (28.05) | 0.067 |
| SpO2, median (IQR) | 98.00 (95–100) | 98.00 (94–100) | 0.736 |
| GCS, median (IQR) | 6 (4–8) | 7 (3–11) | 0.231 |
| Systolic BP, mean (SD) | 122.30 (37.57) | 132.08 (34.90) | 0.452 |
| Resp. rate, mean (SD) | 17.34 (9.05) | 19.03 (8.43) | 0.871 |
| Shock index, median (IQR) | 0.79 (0.63–0.98) | 0.79 (0.62–0.98) | 0.856 |
| Achieved first pass success, n (%) | 46 (79.31) | 305 (97.13) | <0.001 |
| Grade of first intubator, n (%) | <0.001 | ||
| Paramedic | 47 (81.03) | 293 (93.31) | * |
| Registrar as sole physician | 0 (0) | 4 (1.27) | |
| Supervised registrar | 6 (10.34) | 9 (2.87) | |
| Specialist | 5 (8.62) | 8 (2.55) | |
| Weekday, n (%) | 0.374 | ||
| Monday | 5 (8.6) | 32 (10.2) | |
| Tuesday | 10 (17.2) | 33 (10.5) | |
| Wednesday | 4 (6.9) | 44 (14.0) | |
| Thursday | 7 (12.1) | 48 (15.3) | |
| Friday | 9 (15.5) | 42 (13.4) | |
| Saturday | 15 (25.9) | 61 (19.4) | |
| Sunday | 8 (13.8) | 54 (17.2) | |
Statistically significant difference at P < 0.05.
1 nautical mile = 1.852 km.
HIRT, Head Injury Retrieval Trial; IQR, interquartile range; RLTC, Rapid Launch Trauma Coordinator; SD, standard deviation.
Primary outcome
In the HIRT period 79.31% (n = 46) of intubations met the 45‐min target, whereas 43.6% (n = 137) met the target in the RLTC period (P < 0.001).
The median (IQR) overall time to intubation in the HIRT period was 33 (25–41) min which was significantly shorter than the RLTC period at 47 (38–60) min (P < 0.001).
Locations and compliance of cases with the standard by dispatch period are depicted in Figure 1.
Figure 1.
Locations of patients and compliance with the 45‐min intubation target by dispatch periods. (a) HIRT period: 20‐month period covering entire Sydney coordination area. (b) RLTC period: 108‐month period, response restricted to a line north of the M4 motorway/Parramatta River by NSW Ambulance tasking policy unless no other assets available. FKS, first key stroke of emergency call; HIRT, Head Injury Retrieval Trial; RLTC, Rapid Launch Trauma Coordinator.
Figure 2 demonstrates the relationship between distance and time from FKS to intubation between the two dispatch periods with trapped/access difficulty patients excluded (for complete case analysis figure, see Fig. S2).
Figure 2.
Relationship between distance to patient and overall time to intubation with regression lines. FKS, first key stroke of emergency call; HIRT, Head Injury Retrieval Trial; RLTC, Rapid Launch Trauma Coordinator. Dispatch period: (
), HIRT; (
), RLTC; (
), HIRT; (
), RLTC.
Furthermore, we conducted a negative binomial regression to estimate the effect on overall time to intubation from distance to the scene while controlling for the dispatch system type, entrapment/difficult access, indication for intubation, first pass success, grade of first intubator, working versus weekend day and business hours versus out of hours. The overall model was significant (χ 2(12) = 222.98, P < 0.001). McFadden's pseudo R 2 for full model containing predictors for negative binomial model improved intercept only model variance prediction by 7% (R 2 = 0.07, P < 0.001).
Distance to the scene was positively related to the overall time to intubation (b = 0.018, SE = 0.0014, χ 2(1) = 164.10, P < 0.001; Incident Rate Ratio = 1.018, 95% confidence interval 1.015–1.020). Furthermore, we found that dispatch system, entrapment/access difficulty and indication for intubation revealed statistically significant effects on the overall time to intubation (χ 2(1) = 43.17, P < 0.001; χ 2(1) = 13.12, P < 0.001; and χ 2(3) = 28.30, P < 0.001, respectively). Table S1 presents further details on the effect sizes and incident rates.
Secondary outcomes
There is a significant difference between the two periods in activation, response and contact to intubation intervals (Table 2).
TABLE 2.
Secondary time interval outcomes by dispatch period
| Time intervals (min) | Dispatch system | Difference between groups | |
|---|---|---|---|
| HIRT (n = 58) | RLTC (n = 314) | ||
| Activation interval, median (IQR) | 6 (3.5–7) | 11.50 (8–20) | P < 0.001 |
| Response interval, median (IQR) | 12 (10–16) | 16 (12–20) | P = 0.002 |
| Contact to intubation interval, median (IQR) | 12 (8–20) | 16 (12–21) | P < 0.001 |
HIRT, Head Injury Retrieval Trial; IQR, interquartile range; RLTC, Rapid Launch Trauma Coordinator.
A negative binomial regression model to estimate the effect on the Contact to Intubation interval from distance to the scene, physiological characteristics, while controlling for the dispatch system type, entrapment/difficult access, indication for intubation, first pass success, grade of first intubator demonstrated a marginally significant relationship between dispatch period and Contact to Intubation interval (χ 2(16) = 88.89, P < 0.001; b = −0.159; P = 0.049) (Table S2). McFadden's pseudo R 2 for full model containing predictors for negative binomial model improved intercept only model variance prediction by 13% (R 2 = 0.13, P < 0.001).
Distribution of activation intervals between dispatch periods is presented in Figure 3a and the relationship between response interval and distance to the patient by dispatch period is presented in Figure 3b.
Figure 3.
(a) Distribution of activation intervals comparing dispatch periods. (b) Relationship between response time and distance from base with regression lines. HIRT, Head Injury Retrieval Trial; RLTC, Rapid Launch Trauma Coordinator. Dispatch system: (
), HIRT; (
), RLTC; (
), HIRT; (
), RLTC.
Discussion
We have demonstrated a significant deterioration in the rate of RSI occurring within the 45‐min benchmark between the HIRT period and the current RLTC period. An increase in the median time from the emergency call to intubation, and in all three sub‐intervals was also observed. Dispatch model, distance to scene, intubation indication and entrapment status were all associated with time to intubation on multivariate testing.
These outcomes cannot be compared with the reported South Australian 37% intubation benchmark as they cover the entire state of South Australia from a single base. Additionally, the South Australian study assumed activation time was minimal. Our study has the strength of measuring the time from the FKS of the emergency call. We have observed a significant difference in activation times in NSW depending on the case identification system with the South Australian system most resembling the RLTC process. We found that nearly 80% of patients in the service area could be intubated by the CRRH service within the 45‐min benchmark during the HIRT period. This included all cases less than 28 nm (52 km) from the operations base that were not trapped (Fig. 2). This distance covers 60% of the NSW population, or 5 million people. Due to dispatch delays, there was no distance where intubation within 45 min could be assured for non‐trapped patients in the RLTC period.
The observed deterioration after the dispatch model change mirrors the changes previously reported in the paediatric pre‐hospital system. 8 The time taken to reach a Paediatric Trauma Centre increased by nearly 30 min, the rate of helicopter transport halved and the rate of direct transfer of severely injured children to a paediatric trauma centre also decreased. The present study indicates similar deterioration in timeliness of care for adult patients up to the end of the study period in 2022. The rate of RSI within the 45‐min benchmark time has nearly halved from the HIRT to the RLTC periods. Although the HIRT pioneered direct screening of the CAD by HEMS crew in NSW, access to the CAD was removed at conclusion of recruitment in 2011. In 2018 all seven non‐CRRH helicopter bases in NSW were given access to the CAD and authorised to alert the RLTC of appropriate cases. The CRRH which is the fastest responding HEMS in NSW and Australia, 15 is currently the only NSW HEMS base without CAD access.
The cause for the observed performance decrement appears to be increases in all three time sub‐intervals with activation time the largest contributor. Figure 3a indicates a long tail of activation times in the RLTC period with the 75th centile at 20 min, compared with 7 min for the HIRT period. The time to depart base from tasking call through the entire RLTC period was median 3 min (IQR 2–4). Hence the increase in activation time arises from the RLTC dispatch process, rather than helicopter start time. Response time was closely related to distance in both periods (Fig. 3b). The time distance relationship for total time to patient contact (activation time plus response time – see Fig. S3) combined with Figure 3 indicates that extended time to patient contact beyond that predicted by distance alone was a largely a product of activation delay.
The difference in the regression lines in Figure 3b suggests helicopter speed differences between periods. An A109E was utilised exclusively during the HIRT period with a cruise speed 20 knots (37 km/h) faster than the BK117s which were utilised for the majority of the RLTC period. The BK117s were replaced towards the end of 2022 with a faster type (H145) which will reduce this difference going forward.
Dispatch period was marginally significantly related to the patient contact to intubation interval in the regression model (Table S2). Other modifying factors such as changes in case‐mix (intubation indication and physiology) and entrapment were also identified. Registrars acted as sole physicians without a supervising specialist in the RLTC period, although this was not significant in either regression model (Tables 1 and 2).
Limitations
This is a before and after system change study with the inherent limitations of the present study design, particularly potential changes in unrecognised confounding variables. We specifically examined sub‐intervals however to explore causes of the overall change in observed guideline compliance. There were 99 cases missing emergency call time data in the RLTC period who were hence excluded with potential for selection bias. Tasking criteria were different between periods which has probably produced the observed differences in case mix. Although this may account for the observed time differences, a previous paediatric dispatch study using consistent tasking criteria also observed a significant performance difference between dispatch models. 16 As the RLTC did not provide FKS times to CRRH crews during the RLTC period, FKS time had to be inferred from the time booked. Hence, the reported time to depart base and overall time to intubation in the RLTC period is likely to be a minute or so shorter than the actual time when measured from FKS. The effect of both periods being measured from FKS, however, would be to increase the observed difference in activation time and total time to intubation.
Conclusions
Time from emergency call to intubation was significantly shorter in the HIRT period where all non‐trapped cases less than 50 km distance from the operations base were intubated in less than the 45‐min benchmark. There was no distance where intubation within 45 min reliably occurred for non‐trapped patients in the RLTC period due to dispatch delays. All three sub‐intervals of activation, response and patient contact to intubation were also longer in the RLTC period.
Supporting information
Figure S1. Flow chart of patient inclusion. HIRT, Head Injury Retrieval Trial; RLTC, Rapid Launch Trauma Coordinator; RSI, rapid sequence intubation.
Figure S2. Relationship between FKS to intubation, and distance from the base; complete case analysis. FKS, first key stroke; HIRT, Head Injury Retrieval Trial; RLTC, Rapid Launch Trauma Coordinator.
Figure S3. Relationship between FKS to patient contact interval and distance from base to incident scene.
Table S1. Predictors of the overall time to intubation using a negative binomial regression.
Table S2. Predictors of the contact to intubation interval using a negative binomial regression.
Acknowledgements
The authors gratefully acknowledge the assistance of Mr Russell Hoore in production of the mapping figure. Open access publishing facilitated by The University of Sydney, as part of the Wiley ‐ The University of Sydney agreement via the Council of Australian University Librarians.
Competing interests
None declared.
Data availability statement
The data that support the findings of the present study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Figure S1. Flow chart of patient inclusion. HIRT, Head Injury Retrieval Trial; RLTC, Rapid Launch Trauma Coordinator; RSI, rapid sequence intubation.
Figure S2. Relationship between FKS to intubation, and distance from the base; complete case analysis. FKS, first key stroke; HIRT, Head Injury Retrieval Trial; RLTC, Rapid Launch Trauma Coordinator.
Figure S3. Relationship between FKS to patient contact interval and distance from base to incident scene.
Table S1. Predictors of the overall time to intubation using a negative binomial regression.
Table S2. Predictors of the contact to intubation interval using a negative binomial regression.
Data Availability Statement
The data that support the findings of the present study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.