BMJ  2003;327:1316 (6 December), doi:10.1136/bmj.327.7427.1316

Paper

Cost effectiveness and cost utility model of public place defibrillators in improving survival after prehospital cardiopulmonary arrest

¹ Robertson Centre for Biostatistics, University of Glasgow, Glasgow G12 8QQ, ² Department of Medical Cardiology, University of Glasgow, Glasgow G32 2ER, ³ Scottish Ambulance Service Headquarters, Edinburgh EH10 5UU, ⁴ Greater Glasgow NHS Board, Glasgow G3 8YZ

Abstract

Objective To determine the cost effectiveness and cost utility of locating defibrillators in all major airports, railway stations, and bus stations throughout Scotland.

Design Economic modelling exercise with data from Heartstart (Scotland). Parameters used in economic model included direct costs derived for increased accident and emergency attendances, increased hospital bed days, purchase and maintenance of defibrillators, and training in their use; life years gained calculated from increased discharges from hospital and mean survival after discharge; utility (quality of life) obtained from published data. Sensitivity analyses tested the robustness of model. Future gains discounted at 1.5% a year and future costs at 6%.

Setting Whole of Scotland.

Subjects Records of all prehospital cardiac arrests due to presumed heart disease that occurred in a major airport, railway, or bus station between May 1991 and March 1998 and were not witnessed by ambulance or medical staff.

Main outcome measures Observed survival to hospital admission and observed survival to discharge. Predicted survival calculated by applying observed survival in patients attended by ambulance staff within three minutes to those who waited longer.

Results The total discounted direct costs were £18 325 a year. The cost per life year gained was £29 625 ($49 625, €43 151) and the cost per quality adjusted life year (QALY) gained was £41 146 ($68 924, €59 932). More widespread provision of public place defibrillators would increase these figures.

Conclusions The cost per QALY calculated for public place defibrillators represents poorer value for money than some alternative strategies for improving survival after prehospital cardiopulmonary arrest, such as the use of other trained first responders. The figure exceeds the commonly discussed cut off levels for funding in the United Kingdom and United States of £30 000 and $50 000 per QALY, respectively.

Introduction

Increasing numbers of defibrillators are being provided in public places in the United Kingdom¹ and the United States.² However, there is little information on the value for money of such a strategy. In England, the Department of Health has committed more than £3m to provide defibrillators in 72 public places. In contrast, no central funding has, as yet, been provided for public place defibrillators in Scotland. We determined the economic efficiency of locating defibrillators in all major airports, railway stations, and bus stations throughout Scotland.

Methods

Data source
Since 1988, Scottish ambulance crews have collected data prospectively on all resuscitation attempts after cardiopulmonary arrests nationwide. The data include call-response interval (time from telephone call to arrival of the ambulance), location of the arrest, presumed cause of arrest and whether defibrillation was attempted. Staff in hospital medical records departments document whether patients are discharged alive. The data are collated to form the Heart-start (Scotland) register.

Economic model
We considered the status quo (no public place defibrillators) and the provision of defibrillators in all major airports and railway and bus stations. We compared costs and benefits from a health service perspective. In clinical trials, outcome is usually measured as survival, though quality adjusted survival is also important to patients and decision makers. Therefore, we undertook a cost effectiveness analysis using life years gained and a cost utility analysis using quality adjusted life years (QALY) gained.

During the period studied, there were no public place defibrillators in Scotland. All prehospital defibrillation was undertaken by ambulance staff (99%) or general practitioners (1%). We identified all arrests that occurred in a major airport or railway or bus station over seven years from May 1991 and were due to cardiac disease and were not witnessed by ambulance staff. We determined the observed survival to admission and discharge then calculated predicted survival after location of defibrillators in these sites. Our basic model assumed that the number of defibrillators per site was sufficient to enable prompt defibrillation of everyone arresting in that site. We also assumed that public place defibrillators would have the same effects on survival as early attendance of ambulance staff. So to calculate predicted survival we applied the observed survival among patients attended by ambulance staff within three minutes to those who waited longer. This method is described in greater detail elsewhere.³

We calculated current mean survival after discharge from hospital and applied this to the additional patients who could be discharged alive. We applied a measure of utility (quality of life) derived from a study that used the health utilities index mark III.⁴

In the basic model, we included the direct costs to the health service, including purchase and maintenance of automated external defibrillators, basic training of key staff members located nearby, and the marginal costs resulting from additional or prolonged hospital admissions. We applied the average cost for attendance at an accident and emergency department. For additional patients admitted to hospital, we applied a mean length of stay of three days in a coronary care unit before transfer to a general medical or cardiology ward. We applied average Scottish NHS costs to these beds.⁵ We assumed that there would be no direct costs generated by the additional survivors requiring outpatient attendance or readmission after discharge. Also, we included no indirect costs—for example, due to social care or employment. All costs were based on data for the financial year April 2000 to March 2001, inclusive.

Costs and benefits were estimated for the average period of survival after arrest. We adopted usual economic practice and placed less weight on future gains. We adhered to the National Institute for Clinical Excellence (NICE) recommendations by discounting future costs and benefits at 6% and 1.5% a year, respectively. The cost effectiveness and cost utility ratios were calculated by dividing the difference in discounted lifetime costs between the two options by the difference in discounted lifetime health benefits.

Sensitivity analyses
To test the robustness of the basic model, we varied the assumptions and values used in a series of sensitivity analyses. These analyses tested the impact of variations in the number of cardiac arrests, the effectiveness of public place defibrillators, the number of defibrillators required and their cost, hospital costs, and longer term costs for survivors. For more details see bmj.com.

Results

Numbers of sites, arrests, and defibrillators
Over the period studied, there were four major airports, nine major railway stations, and four major bus stations in Scotland, equating to 17 eligible sites. Over seven years, 38 arrests occurred in these locations, equating to 5.4 a year. In the basic model, we assumed that four defibrillators would be located in each airport, one in each bus station, two in each of the largest two railway stations, and one in each of the seven others (31 defibrillators altogether).

Admission, survival, and quality of life
The observed survival to arrival at the accident and emergency department, admission, and discharge was 52.9%, 26.4%, and 14.7%, respectively. If public place defibrillators were available, the predicted survival figures were 66.7%, 33.3%, and 16.7%, respectively. Therefore, the marginal increases a year in the numbers surviving were 0.7 (13.8%), 0.4 (6.9%), and 0.1 (2.0%), respectively.

The mean length of stay after admission was 24 days among those discharged alive, 8 days among those who died, and 14 days overall. Application of these figures to the 5.4 eligible arrests a year resulted in 0.7 additional patients attending accident and emergency and 5.6 additional inpatient days; 1.4 in coronary care and 4.2 in general medicine or cardiology. Mean survival after discharge alive from hospital was 6.2 years.

After discounting, we gained 5.7 life years per survivor—that is, surviving to discharge from hospital. We applied the utility value of 0.72, calculated by Nichol et al,⁵ to estimate the gain in QALYs. This meant that, on average, health related quality of life after arrest was 72% of normal. The gain in QALYs per survivor was, therefore, 4.5 undiscounted and 4.1 discounted.

Costs
The mean costs were £46 per accident and emergency attendance, £612 per day in coronary care, and £234 per day in general medicine or cardiology.⁵ Each defibrillator cost £2500 to buy and maintain. Training was calculated per site rather than per defibrillator. We applied the costs of the Scottish Ambulance Service training course, which was £52.40 a year (A Marsden, Scottish Ambulance Service, personal communication).

The overall initial capital cost of the defibrillators was £77 500. The capital charge over five years was £93 310 without discounting and £79 020 with discounting at 6%. Including training, this equated to £16 554 a year. The incremental cost due to additional accident and emergency attendances and in hospital care was £1770 a year. Therefore, the total direct cost combining capital and revenue was £18 325 a year. The life year gain per year was 0.72, hence the discounted net cost per life year gained was £29 625. The QALY gain a year was 0.44, producing a discounted net cost per QALY gained of £41 146.

Sensitivity analyses
Varying our assumptions about health gains from public place defibrillators had a much greater impact on our results than varying our estimates of costs, particularly hospital costs. Even extreme changes, such as doubling ward costs and multiplying accident and emergency costs by 10, had minimal impact.

In the multi-way sensitivity analyses, combination of changes that impacted favourably on health gain produced a net cost per QALY of £24 788 (table 1). Combination of assumptions with the opposite effect produced a figure of £67 869. Application of both assumptions resulting in reduced defibrillator cost produced a figure of £17 956. The most extreme scenario, including the most favourable assumptions about both cost and outcome, produced a figure of £13 979.

View this table: [in this window] [in a new window]   Table 1 Multi-way sensitivity analyses of effect of public place defibrillators

 

Discussion

Public place defibrillators may not be the most cost effective means of improving survival and quality of life after prehospital arrest. Alternative strategies, such as use of trained first responders including the police, may produce greater improvements and better value for money (table 2). However, caution is needed when we compare studies from countries with different healthcare systems. Also, the sensitivity analyses showed that our results were sensitive to assumptions regarding effectiveness. Therefore, our conclusions require corroboration from prospective studies. In England, the Department of Health has provided funding for 700 public place defibrillators.¹ The American Heart Association supports the principle⁹ but advised that expansion should be halted until further information on clinical and cost effectiveness from clinical trials is available.²

View this table: [in this window] [in a new window]   Table 2 Cost effectiveness of other population based interventions for prehospital cardiopulmonary arrest

 

The Heartstart register collects data prospectively throughout Scotland and therefore provides an invaluable tool for modelling the potential impact of public place defibrillators. In a previous study we showed that only 21% of arrests not witnessed by ambulance crews occurred in sites where public place defibrillators could impact on survival and only then if defibrillators were as commonplace as fire extinguishers.³ We calculated that locating defibrillators in every public site across Scotland would increase overall survival from 5.0% to 6.5%.³ This is less than the potential improvement achievable through some alternative strategies.¹⁰

We are aware of only two previous cost analyses on public place defibrillators. Both were limited by a lack of data on either cost or outcome.^{4 11} The Heartstart register provided us with accurate information on both the location and outcome of arrest, enabling us to make informed calculations of the potential cost, coverage, and impact of public place defibrillators.

In our model we included sites similar to those selected by the Department of Health, such as major airports and railway stations. England covers about 130 410 square kilometres (50 351 square miles). The Department of Health has provided funding for 700 defibrillators in 72 sites across the whole of England. Woollard attempted to model the cost effectiveness of this strategy.¹¹ A crucial assumption in his model was that half of all future arrests in public places in the whole of England will occur in the 72 sites in which defibrillators have been located. Because airports have a high volume of human traffic they are considered good locations for defibrillators. However, they often cover a large area, covering several levels, and the people using them are relatively young and mobile. Gratton et al reviewed all arrests over one year in Kansas City.¹² The 326 arrests occurred in 288 different locations. Of the 16 locations where more than one arrest occurred, only five were public places and only two arrests occurred in each site. Kansas City airport covers 10 hectares (25 square acres) and the two arrests at the airport occurred 6.1 km (4 miles) apart. Gratton et al concluded that "nursing homes" are the only non-healthcare sites in which the incidence and density of arrests justifies provision of defibrillators.¹²

In our study, the survival gain from public place defibrillators was estimated from a comprehensive population based register because randomised controlled trial data were not available. We were obliged to use a figure for utility obtained from a different population which may or may not be applicable to Scotland.⁴

We obtained a cost per QALY gained of £41 422 ($64 743) for providing defibrillators in all major airports and railway and bus stations. Expansion beyond these sites is likely to reduce cost effectiveness. Although there is no absolute "cut off" for funding, the chairman of the National Institute for Clinical Excellence (NICE) observed that recommended technologies tend to cost £30 000 per QALY or less. This figure corresponds well to the cut off of $50 000 frequently applied in the United States. The figure we obtained from our basic model exceeds these values.

It is important to consider the opportunity cost of investing public funding in public place defibrillators. Our study and others indicate that alternative population strategies for reducing time to defibrillation, such as use of trained first responders, might be more clinically^{3 7} and cost effective.⁴ Implantable cardiac defibrillators are an effective intervention in patients known to be at high risk of cardiopulmonary arrest with a cost per life year gained of £26 000-£31 000.¹⁰ From a wider perspective, several primary and secondary prevention interventions may be more cost effective in reducing overall mortality from coronary heart disease.^{11 12} We support the view of the American Heart Association that evidence of clinical and cost effectiveness from randomised controlled trials is required before further expansion of public place defibrillators can be justified.

What is already known on this topic Early defibrillation improves survival after prehospital arrest Public place defibrillators can reduce time to defibrillation in some arrests Information is lacking on whether greater benefit could be gained by investing the money spent on public place defibrillators in alternative strategies What this paper adds Modelling of costs of locating defibrillators in all major airports, railway, and bus stations throughout Scotland resulted in costs of £29 625 for each life year gained and £41 146 for each QALY These costs represent poorer value for money than some alternative strategies, such as the use of other trained first responders, and exceed the commonly used cut-off levels for funding

---

This is an abridged version; the full version is on bmj.com

We thank the Scottish Ambulance Service and hospital medical records staff for supplying the data on which the study was based.

Contributors: See bmj.com

Funding: British Heart Foundation.

Competing interests: None declared.

Ethical approval: Not required.

References

1. Secretary of State for Health. Saving lives: our healthier nation. London: Department of Health, 1999.
2. Nichol G, Hallstrom AP, Kerber R, Moss AJ, Ornato JP, Palmer D, et al. American Heart Association report on the second public access defibrillation conference, April 17-19, 1997. Circulation 1998;97: 1309-14.[Free Full Text]
3. Pell JP, Sirel JM, Marsden AK, Ford I, Walker N, Cobbe SM. Potential impact of public access defibrillators on overall survival after out of hospital cardiopulmonary arrest: retrospective cohort study. BMJ 2002;325: 515-7.[Abstract/Free Full Text]
4. Nichol G, Hallstrom A, Ornato J, Riegal B, Stiell IG, Valenzuela T, et al. Potential cost-effectiveness of public access defibrillation in the United States. Circulation 1998;97: 1315-20.[Abstract/Free Full Text]
5. Information and Statistics Division. Scottish health service costs. Edinburgh: NHS Scotland, 2001.
6. Nichol G, Laupacis A, Stiell I, O'Rourke K, Anis A, Bolley H, et al. Cost-effectiveness analysis of potential improvements to emergency medical services for victims of out-of-hospital cardiac arrest. Ann Emerg Med 1996;27: 711-20.[CrossRef][ISI][Medline]
7. Lee K, Angus D, Abramson N. Cardiopulmonary resuscitation: what cost to cheat death? Crit Care Med 1996;24: 2046-52.[CrossRef][ISI][Medline]
8. Groeneveld P, Kwong J, Liu Y, Rodriguez A, Jones M, Sanders G, et al. Cost-effectiveness of automated external defibrillators on airlines. JAMA 2001;28: 1482-9.
9. Weisfeldt ML, Kerber RE, McGoldrick RP, Moss AJ, Nichol G, Ornata JP, et al. Public access defibrillation: a statement for health care professionals from the American Heart Association task force on automatic external defibrillation. Circulation 1995;92: 2763.[Free Full Text]
10. Pell JP, Sirel JM, Marsden AK, Ford I, Cobbe SM. Effect of reducing ambulance response times on deaths from out of hospital cardiac arrest: cohort study. BMJ 2001;322: 1385-8.[Abstract/Free Full Text]
11. Woollard M. Public access defibrillators: a shocking idea? J Public Health Med 2001;23: 98-102.[Abstract/Free Full Text]
12. Gratton M, Lindholm DJ, Campbell JP. Public access defibrillators. Prehosp Emerg Care 1999;3: 303-5.[Medline]

(Accepted September 30, 2003)

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

Related Articles

Need for differential discounting of costs and health effects in cost effectiveness analyses

Werner B F Brouwer, Louis W Niessen, Maarten J Postma, and Frans F H Rutten
BMJ 2005 331: 446-448. [Extract] [Full Text] [PDF]

Public place defibrillators are not cost effective
BMJ 2003 327: 0. [Full Text]

Cardiovascular diseases

Giulio Bognolo
BMJ 2003 327: 1354. [Extract] [Full Text]

This article has been cited by other articles:

• Cairns, K J, Hamilton, A J, Marshall, A H, Moore, M J, Adgey, A A J, Kee, F (2008). The obstacles to maximising the impact of public access defibrillation: an assessment of the dispatch mechanism for out-of-hospital cardiac arrest. Heart 94: 349-353 [Abstract] [Full text]  
• Jones, P, Lode, N (2007). Ventricular fibrillation and defibrillation. Arch. Dis. Child. 92: 916-921 [Abstract] [Full text]  
• Singaroyan, R., Seed, C. A., Egdell, R. M. (2006). Is a target culture in health care always compatible with efficient use of resources? A cost-effectiveness analysis of an intervention to achieve thrombolysis targets. J Public Health (Oxf) 28: 31-34 [Abstract] [Full text]  
• Brouwer, W. B F, Niessen, L. W, Postma, M. J, Rutten, F. F H (2005). Need for differential discounting of costs and health effects in cost effectiveness analyses. BMJ 331: 446-448 [Full text]  
• Krumholz, H. M. (2004). The year in health care delivery and outcomes research. J Am Coll Cardiol 44: 1130-1136 [Full text]  
• Wyatt, J P, Campbell, M (2004). JournalScan. Emerg. Med. J. 21: 205-206 [Full text]  
• (2004). Defibrillators Might Not Help Much for Out-of-Hospital Cardiac Arrest. Journal Watch Cardiology 2004: 5-5 [Full text]  
• (2004). Defibrillators Might Not Help Much for Out-of-Hospital Cardiac Arrest. JWatch General 2004: 4-4 [Full text]  

Rapid Responses:

Read all Rapid Responses

Incorrect numbers?

Adam Jacobs
bmj.com, 10 Dec 2003 [Full text]

Cost-effectiveness of public place defibrillators

Afschin Gandjour
bmj.com, 15 Dec 2003 [Full text]

Problems with Scottish Public Place AEDs do not apply

Michael C Colquhoun
bmj.com, 18 Dec 2003 [Full text]