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Hyperbaric chambers One-person hyperbaric chambers are the most practical option when space is limited. A chamber that treats patients supine is generally more versatile than one where patients recline. However, some patients, for example amputees, may find transferring to a sitting position easier than one where they must lie down. Nevertheless, we consider here a chamber where the patient is treated supine and can lie down. This type of one-person chamber costs around £72,000, and one version is supplied by Hyox Systems of Aberdeen, UK (the Clinica 2000 Hyperbaric Therapy Unit). An oxygen recirculation system, which reduces oxygen consumption by around 80%, would add about £30,000 to the capital cost. Costs of £72,000 and £110,000 were used for the upper range. Rebates are available to hospitals, so the £72,000 was reduced by lO% to give the lowerrange cost, while the lower-range cost of a chamber with a recirculation unit was £lOO,OOO.Capital costs were also amortised over a lO-year period using a method described by Drummond et al.13This calculation assumed that annuity payments occurred in advance and used discount rates of 3% and 7%. One-person hyperbaric chambers similar to the one used in our calculations are available from several other suppliers. For example, HyperTec, USA, (www.hypertec-02.com) has a unit with a base price of $108,000 (around £58,100) and Tampa Hyperbaric Enterprise, USA (www.oxytank.com) can supply a unit for $80,000 (around £43,045). However, since our costing was based in the UK, we have used the chamber price provided by a UK-based supplier
Staffing Operating a monoplace hyperbaric unit requires one member of staff but, as at Ninewells Hospital, a single member of staff operates three such chambers and may actually supervise four. Chamber operation itself is straightforward, but scheduling patients who are undergoing other treatments is often complex and requires knowledge of a variety of procedures. The person responsible must also be sufficiently knowledgeable to discuss hyperbaric treatment protocols with the referring physician. An experienced and suitably trained nurse (grade E on the currentNHS pay scale) would be appropriate as the manager and would cost between £21,978 and £26,541, including the employer's costs. In addition to operating the chamber, the manager is required to do the administrative work, including record-keeping linked to the hyperbaric unit. The unit also needs about half a day of consultant time each week. The cost of this time has been calculated by dividing a consultant's basic annual salary by 730 to give the cost of a half day. Doing this for the first and third points on the NHS hospital consultant pay scale (pay scale code MCn) gives a cost of between £111 and £118, including the employer's costs. The total cost of the consultant has been calculated by multiplying these costs by the number of productive weeks (44 to 47 weeks; see 'Cost per treatment session'). Oxygen Oxygen is provided from the main supply of the hospital, which invariably will use liquid oxygen. The price paid for oxygen varies depending on local contracts with suppliers, but a range of 25p to 40p per litre of liquid oxygen is normal. One litre of liquid oxygen is equivalent to about 842 litres of gaseous oxygen at 15°C and 101kPa (1 atmosphere [atm]).14 To calculate the volume of 1 litre of liquid oxygen at the operating conditions of the hyperbaric chamber (25°C and 202kPa or 2 atm) we used the Combined Gas Law, PlV/Tl = PzV/Tz, where: P = pressure V = volume T = temperature (in kelvin). Using SI units we get: 101 (842) =202Vz 288 298 This gives a figure of around 436 litres for Vz' the volume at 25°C and 202kPa. Using this figure gives a cost range of 0.06p to 0.09p per litre of gaseous oxygen. A one-person chamber of the type supplied by Hyox has a flow rate of 150 litres per minute without oxygen recirculation and 25 litres per minute when fitted with a recirculation unit. Property and cleaning costs The Scottish Health ServiceCosts book for 2004 (section 9: functional costs) prepared by the Information and Statistics Division of NHS Scotland, was used for maintenance-of-property costs and cleaning costs. 15 We have assumed that the hyperbaric oxygen therapy is delivered in one of the six Scottish hospitals classified as large, general teaching hospitals by the Information and Statistics Division. The lowest and highest costs for the six hospitals gave rangJOURNAL OF WOUND CARE VOl IS, NO 6. JUNE 2006 ~---- ~-- ~-- ~ Ao---- "~-""'""-.--- es of £1.90 to £84 per cubic metre for property costs and £17 to £33 per square metre for cleaning costs. A space large enough to hold up to two one-person hyperbaric chambers was then used to calculate the property and cleaning costs for the hyperbaric therapy unit. The room was assumed to be 3m x 4.5m x 3m, giving annual property costs of between £77 and £3402 and an annual cleaning cost of between £230 and £446. Overheads and miscellaneous consumables Overhead costs from Ninewells Hospital have been used. Electricity, steam (for heating), and rent and rates are costed at £4.95, £6.51 and £9.58 per square metre respectively. The gives a total of £21.04 per square metre. To get a range, this figure has been adjusted by HO%. A small cost of lOp per treatment session was added to cover miscellaneous consumables such as disposable cleaning wipes and occasionallaundry costs. Cost per treatment session A standard treatment session at the Hyperbaric Medicine Unit. at Ninewells Hospital comprises 60 minutes inside the hyperbaric chamber at 202kPa (2atm)i oxygen is used for the full 60 minutes. The single member of staff using one chamber can treat six patients a day, five days a week in one chamber. Staff holidays and maintenance are likely to reduce the number of productive weeks from S2 to between 44 and 47 weeks. This means that a single-chamber hyperbaric unit could offer between 1320 and 1410 treatment sessions per year. The cost per treatment session was calculated by dividing the total annual cost of the hyperbaric unit by the number of treatment sessions. To gain an idea of how sensitive the cost per treatment was to the number of patients treated per year, we took the lower cost estimates presented in Table 1 and varied these by :1:10%and then calculated the cost per treatment for 600 to 1600 patients per year. T
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