The ACUTE (Ambulance CPAP: Use, Treatment effect and economics) feasibility study: a pilot randomised controlled trial of prehospital CPAP for acute respiratory failure

The Effect of Prehospital Clinical Trial-Related Procedures on Scene Interval, Cognitive Load, and Error: A Randomized Simulation Study

INTRODUCTION

Globally, very few settings have undertaken prehospital randomized controlled trials. Given this lack of experience, there is a risk that such trials in these settings may result in protocol deviations, increased prehospital intervals, and increased cognitive load, leading to error. Ultimately, this may affect patient safety and mortality. The aim of this study was to assess the effect of trial-related procedures on simulated scene interval, self-reported cognitive load, medical errors, and time to action.

METHODS

This was a prospective simulation study. Using a cross-over design, ten teams of prehospital clinicians were allocated to three separate simulation arms in a random order. Simulations were: (1) Eligibility assessment and administration of freeze-dried plasma (FDP) and a hemoglobin-based oxygen carrier (HBOC), (2) Eligibility assessment and administration of HBOC, (3) Eligibility assessment and standard care. All simulations also required clinical management of hemorrhagic shock. Simulated scene interval, error rates, cognitive load (measured by NASA Task Load Index), and competency in clinical care (assessed using the Simulation Assessment Tool Limiting Assessment Bias (SATLAB)) were measured. Mean differences between simulations with and without trial-related procedures were sought using one-way ANOVA or Kruskal-Wallis test. A p-value of <0.05 within the 95% confidence interval was considered significant.

RESULTS

Thirty simulations were undertaken, representing our powered sample size. The mean scene intervals were 00:16:56 for Simulation 1 (FDP and HBOC), 00:17:22 for Simulation 2 (HBOC only), and 00:14:24 for Simulation 3 (standard care). Scene interval did not differ between the groups (p = 0.27). There were also no significant differences in error rates (p = 0.28) or cognitive load (p = 0.67) between the simulation groups. There was no correlation between cognitive load and error rates (r = 0.15, p = 0.42). Competency was achieved in all the assessment criteria for all simulation groups.

CONCLUSION

In a simulated environment, eligibility screening, performance of trial-related procedures, and clinical management of patients with hemorrhagic shock can be completed competently by prehospital advanced life support clinicians without delaying transport or emergency care. Future prehospital clinical trials may use a similar approach to help ensure graded and cautious implementation of clinical trial procedures into prehospital emergency care systems.

Prehospital continuous positive airway pressure (CPAP) for acute respiratory distress: a randomised controlled trial

OBJECTIVE

To compare the efficacy of continuous positive airway pressure (CPAP) versus usual care for prehospital patients with severe respiratory distress.

METHODS

We conducted a parallel group, individual patient, non-blinded randomised controlled trial in Western Australia between March 2016 and December 2018. Eligible patients were aged ≥40 years with acute severe respiratory distress of non-traumatic origin and unresponsive to initial treatments by emergency medical service (EMS) paramedics. Patients were randomised (1:1) to usual care or usual care plus CPAP. The primary outcomes were change in dyspnoea score and change in RR at ED arrival, and hospital length of stay.

RESULTS

708 patients were randomly assigned (opaque sealed envelope) to usual care (n=346) or CPAP (n=362). Compared with usual care, patients randomised to CPAP had a greater reduction in dyspnoea scores (usual care -1.0, IQR -3.0 to 0.0 vs CPAP -3.5, IQR -5.2 to -2.0), median difference -2.0 (95% CI -2.5 to -1.6); and RR (usual care -4.0, IQR -9.0 to 0.0 min^-1 vs CPAP -8.0, IQR -14.0 to -4.0 min^-1), median difference -4.0 (95% CI -5.0 to -4.0) min^-1. There was no difference in hospital length of stay (usual care 4.2, IQR 2.1 to 7.8 days vs CPAP 4.8, IQR 2.5 to 7.9 days) for the n=624 cases admitted to hospital, median difference 0.36 (95% CI -0.17 to 0.90).

CONCLUSIONS

The use of prehospital CPAP by EMS paramedics reduced dyspnoea and tachypnoea in patients with acute respiratory distress but did not impact hospital length of stay.

TRIAL REGISTRATION NUMBER

ACTRN12615001180505.

Prehospital continuous positive airway pressure for acute respiratory failure: the ACUTE feasibility RCT

BACKGROUND

Acute respiratory failure is a life-threatening emergency. Standard prehospital management involves controlled oxygen therapy. Continuous positive airway pressure is a potentially beneficial alternative treatment; however, it is uncertain whether or not this treatment could improve outcomes in NHS ambulance services.

OBJECTIVES

To assess the feasibility of a large-scale pragmatic trial and to update an existing economic model to determine cost-effectiveness and the value of further research.

DESIGN

(1) An open-label, individual patient randomised controlled external pilot trial. (2) Cost-effectiveness and value-of-information analyses, updating an existing economic model. (3) Ancillary substudies, comprising an acute respiratory failure incidence study, an acute respiratory failure diagnostic agreement study, clinicians perceptions of a continuous positive airway pressure mixed-methods study and an investigation of allocation concealment.

SETTING

Four West Midlands Ambulance Service hubs, recruiting between August 2017 and July 2018.

PARTICIPANTS

Adults with respiratory distress and peripheral oxygen saturations below the British Thoracic Society's target levels were included. Patients with limited potential to benefit from, or with contraindications to, continuous positive airway pressure were excluded.

INTERVENTIONS

Prehospital continuous positive airway pressure (O-Two system, O-Two Medical Technologies Inc., Brampton, ON, Canada) was compared with standard oxygen therapy, titrated to the British Thoracic Society's peripheral oxygen saturation targets. Interventions were provided in identical sealed boxes.

MAIN OUTCOME MEASURES

Feasibility objectives estimated the incidence of eligible patients, the proportion recruited and allocated to treatment appropriately, adherence to allocated treatment, and retention and data completeness. The primary clinical end point was 30-day mortality.

RESULTS

Seventy-seven patients were enrolled (target 120 patients), including seven patients with a diagnosis for which continuous positive airway pressure could be ineffective or harmful. Continuous positive airway pressure was fully delivered to 74% of participants (target 75%). There were no major protocol violations/non-compliances. Full data were available for all key outcomes (target ≥ 90%). Thirty-day mortality was 27.3%. Of the 21 deceased participants, 14 (68%) either did not have a respiratory condition or had ceiling-of-treatment decision implemented that excluded hospital non-invasive ventilation and critical care. The base-case economic evaluation indicated that standard oxygen therapy was probably cost-effective (incremental cost-effectiveness ratio £5685 per quality-adjusted life-year), but there was considerable uncertainty (population expected value of perfect information of £16.5M). Expected value of partial perfect information analyses indicated that effectiveness of prehospital continuous positive airway pressure was the only important variable. The incidence rate of acute respiratory failure was 17.4 (95% confidence interval 16.3 to 18.5) per 100,000 persons per year. There was moderate agreement between the primary prehospital and final hospital diagnoses (Gwet's AC1 coefficient 0.56, 95% confidence interval 0.43 to 0.69). Lack of hospital awareness of the Ambulance continuous positive airway pressure (CPAP): Use, Treatment Effect and economics (ACUTE) trial, limited time to complete trial training and a desire to provide continuous positive airway pressure treatment were highlighted as key challenges by participating clinicians.

LIMITATIONS

During week 10 of recruitment, the continuous positive airway pressure arm equipment boxes developed a 'rattle'. After repackaging and redistribution, no further concerns were noted. A total of 41.4% of ambulance service clinicians not participating in the ACUTE trial indicated a difference between the control and the intervention arm trial boxes (115/278); of these clinician 70.4% correctly identified box contents.

CONCLUSIONS

Recruitment rate was below target and feasibility was not demonstrated. The economic evaluation results suggested that a definitive trial could represent value for money. However, limited compliance with continuous positive airway pressure and difficulty in identifying patients who could benefit from continuous positive airway pressure indicate that prehospital continuous positive airway pressure is unlikely to materially reduce mortality.

FUTURE WORK

A definitive clinical effectiveness trial of continuous positive airway pressure in the NHS is not recommended.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN12048261.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 25, No. 7. See the NIHR Journals Library website for further project information.

Cost-effectiveness of out-of-hospital continuous positive airway pressure for acute respiratory failure: decision analytic modelling using data from a feasibility trial

Background

Standard prehospital management for Acute respiratory failure (ARF) involves controlled oxygen therapy. Continuous positive airway pressure (CPAP) is a potentially beneficial alternative treatment, however, it is uncertain whether this could improve outcomes and provide value for money. This study aimed to evaluate the cost-effectiveness of prehospital CPAP in ARF.

Methods

A cost-utility economic evaluation was performed using a probabilistic decision tree model synthesising available evidence. The model consisted of a hypothetical cohort of patients in a representative ambulance service with undifferentiated ARF, receiving standard oxygen therapy or prehospital CPAP. Costs and quality adjusted life years (QALYs) were estimated using methods recommended by NICE.

Results

In the base case analysis, using CPAP effectiveness estimates form the ACUTE trial, the mean expected costs of standard care and prehospital CPAP were £15,201 and £14,850 respectively and the corresponding mean expected QALYs were 1.190 and 1.128, respectively. The mean ICER estimated as standard oxygen therapy compared to prehospital CPAP was £5685 per QALY which indicated that standard oxygen therapy strategy was likely to be cost-effective at a threshold of £20,000 per QALY (67% probability). The scenario analysis, using effectiveness estimates from an updated meta-analysis, suggested that prehospital CPAP was more effective (mean incremental QALYs of 0.157), but also more expensive (mean incremental costs of £1522), than standard care. The mean ICER, estimated as prehospital CPAP compared to standard care, was £9712 per QALY. At the £20,000 per QALY prehospital CPAP was highly likely to be the most cost-effective strategy (94%).

Conclusions

Cost-effectiveness of prehospital CPAP depends upon the estimate of effectiveness. When based on a small pragmatic feasibility trial, standard oxygen therapy is cost-effective. When based on meta-analysis of heterogeneous trials, CPAP is cost-effective. Value of information analyses support commissioning of a large pragmatic effectiveness trial, providing feasibility and plausibility conditions are met.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12873-021-00404-8.

The diagnostic accuracy of pre-hospital assessment of acute respiratory failure

Introduction:

Acute respiratory failure (ARF) is a common medical emergency. Pre-hospital management includes controlled oxygen therapy, supplemented by specific management options directed at the underlying disease. The aim of the current study was to characterise the accuracy of paramedic diagnostic assessment in acute respiratory failure.

Methods:

A nested diagnostic accuracy and agreement study comparing pre-hospital clinical impression to the final hospital discharge diagnosis was conducted as part of the ACUTE (Ambulance CPAP: Use, Treatment effect and Economics) trial. Adults with suspected ARF were recruited from the UK West Midlands Ambulance Service. The pre-hospital clinical impression of the recruiting ambulance service clinician was prospectively recorded and compared to the final hospital diagnosis at 30 days. Agreement between pre-hospital and hospital diagnostic assessments was evaluated using raw agreement and Gwets AC1 coefficient.

Results:

77 participants were included. Chronic obstructive pulmonary disease (32.9%) and lower respiratory tract infection (32.9%) were the most frequently suspected primary pre-hospital diagnoses for ARF, with secondary contributory conditions recorded in 36 patients (46.8%). There was moderate agreement between the primary pre-hospital and hospital diagnoses, with raw agreement of 58.5% and a Gwets AC1 coefficient of 0.56 (95% CI 0.43 to 0.69). In five cases, a non-respiratory final diagnosis was present, including: myocardial infarction, ruptured abdominal aortic aneurysm, liver failure and sepsis.

Conclusions:

Pre-hospital assessment of ARF is challenging, with limited accuracy compared to the final hospital diagnosis. A syndromic approach, providing general supportive care, rather than a specifically disease-orientated treatment strategy, is likely to be most appropriate for the pre-hospital environment.

Prehospital management of acute respiratory distress in suspected COVID-19 patients

BACKGROUND

In December 2019, coronavirus disease (COVID-19) emerged in China and became a world-wide pandemic in March 2020. Emergency services and intensive care units (ICUs) were faced with a novel disease with unknown clinical characteristics and presentations. Acute respiratory distress (ARD) was often the chief complaint for an EMS call. This retrospective study evaluated prehospital ARD management and identified factors associated with the need of prehospital mechanical ventilation (PMV) for suspected COVID-19 patients.

METHODS

We included 256 consecutive patients with suspected COVID-19-related ARD that received prehospital care from a Paris Fire Brigade BLS or ALS team, from March 08 to April 18, 2020. We performed multivariate regression to identify factors predisposing to PMV.

RESULTS

Of 256 patients (mean age 60 ± 18 years; 82 (32%) males), 77 (30%) had previous hypertension, 31 (12%) were obese, and 49 (19%) had diabetes mellitus. Nineteen patients (7%) required PMV. Logistic regression observed that a low initial pulse oximetry was associated with prehospital PMV (ORa = 0.86, 95%CI: 0.73-0.92; p = 0.004).

CONCLUSIONS

This study showed that pulse oximetry might be a valuable marker for rapidly determining suspected COVID-19-patients requiring prehospital mechanical ventilation. Nevertheless, the impact of prehospital mechanical ventilation on COVID-19 patients outcome require further investigations.

Is a definitive trial of prehospital continuous positive airway pressure versus standard oxygen therapy for acute respiratory failure indicated? The ACUTE pilot randomised controlled trial

OBJECTIVES

To determine the feasibility of a large-scale definitive multicentre trial of prehospital continuous positive airway pressure (CPAP) in acute respiratory failure.

DESIGN

A single-centre, open-label, individual patient randomised, controlled, external pilot trial.

SETTING

A single UK Ambulance Service, between August 2017 and July 2018.

PARTICIPANTS

Adults with respiratory distress and peripheral oxygen saturations below British Thoracic Society target levels despite controlled oxygen treatment.

INTERVENTIONS

Patients were randomised to prehospital CPAP (O-Two system) versus standard oxygen therapy in a 1:1 ratio using simple randomisation.

PRIMARY AND SECONDARY OUTCOME MEASURES

Feasibility outcomes comprised recruitment rate, adherence to allocated treatment, retention and data completeness. The primary clinical outcome was 30-day mortality.

RESULTS

77 patients were enrolled (target 120), including 7 cases with a diagnosis where CPAP could be ineffective or harmful. CPAP was fully delivered in 74% (target 75%). There were no major protocol violations. Full data were available for all key outcomes (targets ≥90%). Overall 30-day mortality was 27.3%. Of these deceased patients, 14/21 (68%) either did not have a respiratory condition or had ceiling of treatment decisions implemented excluding hospital non-invasive ventilation and critical care.

CONCLUSIONS

Recruitment rate was below target and feasibility was not demonstrated. Limited compliance with CPAP, and difficulty in identifying patients who could benefit from CPAP, indicate that prehospital CPAP is unlikely to materially reduce mortality. A definitive effectiveness trial of CPAP is therefore not recommended.

TRIAL REGISTRATION NUMBER

ISRCTN12048261; Post-results.