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Prolonged use of heat and moisture exchangers does not affect device efficiency or frequency rate of nosocomial pneumonia |
Davis K, Evans S L, Campbell R S, Johannigman J A, Luchette F A, Porembka D T, Branson R D |
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Record Status This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn. Health technology Use of a single heat and moisture exchanger (HME) for 120 hours for patients requiring mechanical ventilation for more than 48 hours. Two intervention strategies were considered: hydrophobic HME (Duration HME) changed every 120 hours (HME-120), and hygroscopic HME (Aqua+) changed every 120 hours (HHME-120).
Economic study type Cost-effectiveness analysis.
Study population Patients requiring mechanical ventilation for more than 48 hours and meeting the criteria for HME use (the criteria were published in another study).
Setting Hospital. The economic study was carried out in the USA.
Dates to which data relate Effectiveness and resource use data corresponded to eligible patients admitted to the surgical intensive care unit between September 1996 and December 1997. The price year was not explicitly specified.
Source of effectiveness data The evidence for final outcomes was based on a single study.
Link between effectiveness and cost data Costing was prospectively conducted on the same patient sample as that used in the effectiveness analysis.
Study sample Power calculations were not used to determine the sample size. The study sample consisted of 220 eligible patients (out of 985 patients who were mechanically ventilated) randomly assigned to either the HHME-24 group (n=100; mean (SD) age of 48 (11) years), the HME-120 group (n=60; mean (SD) age of 43 (17) years), or the HHME group (n=60; mean (SD) age of 46 (14) years).
Study design This was a prospective, randomized, controlled, unblinded clinical trial, carried out in a single centre. The duration of the follow-up was not explicitly specified, but appears to have been for up to 5 days after ventilation or until each patient was extubated. Regarding loss to follow-up, it was reported that on days 2 through 5, the number of patients remaining in the study, and used for analysis for the HME-120 and HHME-120 groups were: 60/60 (day 2), 22/20 (day 3), 10/9 (day 4), and 4/2 (day 5). Devices in all groups could be changed at the discretion of the staff when signs of occlusion or increased resistance were identified.
Analysis of effectiveness The principle (intention to treat or treatment completers only) used in the analysis of effectiveness was not explicitly reported. The health outcome measures were the frequency rate of nosocomial pneumonia and bacterial colonisation, resistance, humidity, duration of use, and clinical evidence of device efficacy (number of suctionings per day, daily volume of saline instilled, and daily volume of secretions suctioned; the number of patients with thin, moderate, and thick secretions; and tracheal tube occlusions). The three study groups were comparable in terms of demographic and prognostic features.
Effectiveness results There was no difference in the number of colony-forming units from device cultures over the 5-day period and no difference between colony-forming units in devices changed every 24 hours compared with devices changed over 120 hours. The average (SD) duration of use was 23 (4) hours in the HHME-24 group, 73 (13) hours in the HME-120 group, and 74 (9) hours in the HHME-120 group. Mean absolute humidity was greater for the hygroscopic devices (30.4 (1.1) mg of H2O/L compared with the hydrophobic devices (27.8 (1.3) mg of H2O/L ), (p<0.05). There was no difference in the humidity from day 0 to day 5 for any of the groups. The frequency rate of nosocomial pneumonia was 8% in the HHME-24 group, 8.3% in the HME-120 group, and 6.6% in the HHME-120 group. Pneumonia rates per 1000 ventilatory support days were 20:1000 (HHME-24), 20.8:1000 (HME-120), and 16.6:1000 (HHME-120), (not significantly different). The resistance of the devices did not change for the HME-120 group throughout 5 days of use. Resistance for the hygroscopic devices (HHME-120) increased mildly, but significantly, from pre-study to day 5. This change was also clinically significant. Airway care was similar among the groups for numbers of suctioning per day, daily volume of saline instilled, and daily volume of secretions suctioned. The number of patients with thin, moderate, and thick secretions was the same for the three groups. There were no tracheal tube occlusions in any of the groups during the study.
Clinical conclusions In this sample of ventilated surgical intensive care unit patients, a 74-hour HME change frequency did not result in increased bacterial invasion or nosocomial pneumonia, increased device resistance, or decreased airway humidity when compared with a 24-hour HME change frequency.
Measure of benefits used in the economic analysis No summary benefit measure was identified in the economic analysis, and only separate clinical outcomes were reported.
Direct costs Costs were not discounted due to the short time frame of the cost analysis. Some quantities were reported separately from the costs (average device use). Cost items were reported separately. Cost analysis covered the costs of the individual components of the ventilatory support circuit and HME. The number of devices used was calculated by saving every device until each patient was extubated and dividing the total by the number of days of use. The perspective adopted in the cost analysis was not explicitly specified. The price year was not given.
Sensitivity analysis No sensitivity analysis was conducted.
Estimated benefits used in the economic analysis Cost results Costs per day were $3.24 for the HHME-24 group, $2.98 for the HME-120 group, and $1.65 for the HHME-120 group.
Synthesis of costs and benefits Costs and benefits were not combined.
Authors' conclusions Changing the hydrophobic or hygroscopic HME after 3 days does not diminish efficiency, increase resistance, or alter bacterial colonisation. The frequency rate of nosocomial pneumonia was also unchanged. Use of HMEs for more than 24 hours, up to 72 hours, is safe and cost-effective.
CRD COMMENTARY - Selection of comparators A justification was given for the choice of the comparator (changing the HME every 24 hours). It was the standard practice in the context in question. You, as a database user, should consider whether this is a widely used health technology in your own setting.
Validity of estimate of measure of effectiveness The effectiveness results are likely to be internally valid given the randomised nature of the study design. However, no power calculations were performed and the principle used in the analysis of effectiveness was not explicitly specified. The study groups were found to be comparable in terms of baseline characteristics. Insufficient information was provided upon which to base an assessment of the degree to which the study sample was representative of the study population.
Validity of estimate of measure of benefit The authors did not derive a measure of health benefit, and so the study may therefore be regarded as a cost-consequences analysis.
Validity of estimate of costs Some quantities were reported separately from the costs and adequate details of the methods of cost estimation were given. The price year and perspective adopted in the cost analysis were not reported. The effects of different procedures on indirect costs (productivity loss) were not discussed. The cost results may not be generalisable to other settings or countries.
Other issues The authors' conclusions appear to be justified given the uncertainties in the data. The issue of generalisability to other settings or countries was not addressed. However, some comparisons were made with other studies. It was noted that the criterion for diagnosis of pneumonia is culture of organisms from bronchoalveolar lavage, while the authors, because of cost considerations, did not use bronchoalveolar lavage in this study. Instead ventilatory support- associated pneumonia (VAP) was defined by clinical criteria.
Implications of the study The findings of the present study suggest that HMEs can be safely replaced every 3 days without an increased risk of nosocomial infection, increased device resistance, or decreased airway humidity.
Source of funding Supported in part by Nellcor-Puritan Bennett, Minneapolis, MN and Hudson-RCI, Temecula, CA, USA.
Bibliographic details Davis K, Evans S L, Campbell R S, Johannigman J A, Luchette F A, Porembka D T, Branson R D. Prolonged use of heat and moisture exchangers does not affect device efficiency or frequency rate of nosocomial pneumonia. Critical Care Medicine 2000; 28(5): 1412-1418 Indexing Status Subject indexing assigned by NLM MeSH Adult; Aged; Airway Resistance; Critical Care; Cross Infection /etiology /prevention & Equipment Design; Female; Heating /instrumentation; Humans; Humidity; Intubation, Intratracheal; Male; Middle Aged; Pneumonia, Bacterial /etiology /prevention & Prospective Studies; Ventilators, Mechanical; control; control AccessionNumber 22000000981 Date bibliographic record published 30/11/2000 Date abstract record published 30/11/2000 |
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