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Continuous subglottic suctioning for the prevention of ventilator-associated pneumonia: potential economic implications |
Shorr A F, O'Malley P G |
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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 The use of endotracheal tubes (ETs) modified to permit continuous subglottic suctioning (CSS), to reduce the incidence of ventilator-associated pneumonia (VAP).
Economic study type Cost-effectiveness analysis.
Study population The study population comprised a hypothetical cohort of patients undergoing nonelective endotracheal intubation (i.e. non-coincident with a planned intervention). The two sub-groups of patients considered were those requiring less than 72 hours of mechanical ventilation (MV) and those requiring longer than 72 hours.
Setting The setting was a hospital. The economic study was performed in the USA.
Dates to which data relate The effectiveness data were collected from studies published between 1995 and 1999. The cost data were collected from studies published between 1991 and 1999. No price year was reported.
Source of effectiveness data The effectiveness data were derived from a review of published studies.
Modelling A decision tree model was used to estimate the effectiveness and cost results, comparing two hypothetical cohorts of 100 patients each.
Outcomes assessed in the review The outcomes assessed in the review were the proportion of patients requiring MV for longer than 72 hours, and the incidence of VAP in patients requiring MV (more than or less than 72 hours).
Study designs and other criteria for inclusion in the review Randomised controlled trials (RCTs) and prospective cohort incidence studies were considered for inclusion in the review. The other inclusion criteria specified that the studies had to have been published in English from 1994 onwards.
Sources searched to identify primary studies MEDLINE was searched for primary studies.
Criteria used to ensure the validity of primary studies The authors did not evaluate the quality of the studies, but relied on sensitivity analyses to assess the uncertainty surrounding the outcomes obtained from the review.
Methods used to judge relevance and validity, and for extracting data Number of primary studies included At least 28 studies were included in the review, of which 8 appear to have been RCTs.
Methods of combining primary studies The relative risk reduction (RRR) for CSS came from just one study, an RCT comparing the treatments of this study. However, the RRR was assumed to be lower in the initial analysis. It was not reported how the other data were derived from the literature.
Investigation of differences between primary studies The authors do not appear to have investigated the differences between the primary studies included in the review.
Results of the review Fifty per cent of the patients required MV for longer than 72 hours.
The incidence of VAP was 25% among patients requiring longer than 72 hours' MV, and 5% among those requiring less than 72 hours' MV.
Methods used to derive estimates of effectiveness The authors made assumptions to derive the estimates of effectiveness.
Estimates of effectiveness and key assumptions The authors estimated that CSS-ETs reduced the incidence of VAP by 30% in the initial analysis, which was less than the primary source RCT found in the review of the literature.
Measure of benefits used in the economic analysis The summary measure of benefit used in the economic analysis was the number of cases of VAP prevented when using CSS-ETs instead of conventional ETs. This figure seems to have been obtained from the results of the decision tree.
Direct costs Some, but not all of the resource quantities were reported separately from the costs. The direct costs considered in the analysis were those of the hospital. These included the costs of VAP (diagnosis, treatment and stay in the intensive care unit) and the costs of ETs (CSS and conventional). The cost data were collected from the manufacturer of the CSS-ETs (Mallinckrodt), bills from the institution in which the study was performed, and published studies. Therefore, the costs were estimated using actual data and some authors' assumptions used in the effectiveness analysis. Since hospital bills and not costs were used to estimate some of the costs, the authors adjusted these costs by a cost-to-charge ratio of 0.6. The costs reported were the total and marginal costs. Discounting was not performed, but was irrelevant since the costs were incurred during a short time. The price year was not reported.
Statistical analysis of costs No statistical analyses of the costs were reported.
Indirect Costs No indirect costs were reported.
Sensitivity analysis One- and two-way sensitivity analyses were performed to assess uncertainty of the model when the following parameters were varied:
the percentage of patients requiring MV for more than 72 hours (range: 25.0 - 75.0);
the incidence of VAP in patients requiring more than 72 hours' MV (range: 12.5 - 37.5);
the incidence of VAP in patients requiring less than 72 hours' MV (range: 2.5 - 7.5);
the RRR of CSS (range: 15.0 - 45.0); and
the cost of VAP (range: $2,683 - $8,048).
In addition, a threshold analysis was performed to determine the point at which CSS-ETs no longer provided savings. A worst-case scenario was considered by varying all the parameters simultaneously by 50%. Therefore, the area of uncertainty investigated was variability in the data.
Estimated benefits used in the economic analysis There were 8.75 cases of VAP when CSS-ETs were used versus 12.5 cases when conventional ETs were used. The period considered in the analysis was unclear (several days, or possibly weeks).
Cost results The total costs associated with the use of CSS-ETs were $61,856, while those associated with the use of conventional ETs were $80,575. Therefore, the net saving obtained with CSS-ETs, compared with conventional ETs, was $18,719.
Synthesis of costs and benefits The cost and benefits were combined by estimating the incremental cost-effectiveness ratios. These measured the cost per case of VAP prevented. The use of CSS-ETs was a dominant strategy because it had lower costs and exhibited higher effectiveness (in terms of a lower number of cases of VAP). Therefore, compared with the use of conventional ETs, there was a net saving of $4,992 per case of VAP avoided and a net saving of $1,872 per patient when using CSS-ETs.
The most sensitive parameter was the cost of VAP, although the primary results were not altered when this parameter was decreased by 50%. The results from the threshold analysis showed that only when the RRR of CSS-ETs fell below 2.1%, or when the cost of VAP was lower than $373, did the use of CSS-ETs require additional net expenditures. The results for the worst-case scenario showed that in order to prevent 0.47 VAP cases, a total cost of $143 (cost per patient of $14.30) was required.
Authors' conclusions The regular use of endotracheal tubes (ETs) modified to permit continuous subglottic suctioning (CSS) for nonelective endotracheal intubations is highly cost-effective. CSS-ETs are associated with significant savings, compared with conventional ETs, because of the lower incidence of ventilator-associated pneumonia (VAP).
CRD COMMENTARY - Selection of comparators Conventional ETs were chosen as the comparator because they were the standard care when no preventive measures for VAP were implemented. Other alternatives used to prevent VAP were named, but were not considered at analysis. You should decide whether a preventive measure for VAP is commonly used in your own setting.
Validity of estimate of measure of effectiveness A review of the literature, which appears to have been systematic, was undertaken. The data were selectively obtained from the available studies. The study is likely to have been influenced by language bias since only English studies were considered for inclusion in the review. No quality assessment of the included studies was performed, and the impact of differences between the primary studies was not considered when estimating the effectiveness. Sensitivity analyses were carried out to assess uncertainty surrounding the parameters, using ranges obtained from the medical literature. However, due to the lack of a quality assessment of the studies, it is not possible to assess whether the ranges were appropriate for the parameters used. This introduces uncertainty into the reliability of the conclusions.
Authors' assumptions were also used to derive the estimates of effectiveness. The assumption used was justified with reference to the medical literature and a personal communication. However, there were several limitations concerning the reliability of data for one important effectiveness estimate (the RRR of VAP for CSS-ETs).
Validity of estimate of measure of benefit The estimation of benefits appears to have been modelled using a decision tree model, which may have been appropriate. Since VAP causes mortality, and this was not considered in the economic analysis, it is uncertain whether the summary measure of effectiveness was appropriate for the study question. It would have been necessary to consider an alternative measure, taking into account the mortality associated with VAP, such as the number of quality-adjusted life-years gained with CSS-ETs in comparison with conventional ETs.
Validity of estimate of costs The authors reported that both the costs to the patient and hospital costs considered in the economic analysis. However, the actual perspective adopted was that of the hospital, which might have been limited. Some relevant costs were excluded from the economic analysis, such as the costs associated with the additional care that a patient with VAP would require while in the intensive care unit. The authors acknowledged that this might have led to an underestimation of the true costs of VAP.
Although the authors used hospital bills to estimate some of the costs, they applied a cost-to-charge ratio of 0.6, which is generally agreed to be a good surrogate for inpatient cost accounting. Only some of the resource quantities were reported separately from the costs. In addition, the price year was not stated, which hinders reflation exercises in other settings. Sensitivity analyses of the costs were performed to take account of the uncertainty these factors may generate. The ranges considered were obtained from the review. Discounting was not performed, which was appropriate given the short time considered in the study.
Other issues The authors made some comparisons of the cost results with those obtained from other studies. Important differences between the studies were found. However, these differences were appropriately considered in the sensitivity analyses. The comparisons also showed that the use of CSS-ETs compares favourably, in terms of cost-effectiveness, with other interventions routinely undertaken to care for patients requiring MV. The issue of the generalisability of the results was not addressed. The authors' conclusions reflected the scope of the study.
Implications of the study The authors suggested that critical-care physicians should use CSS-ETs more frequently. The authors recommended that further studies, to corroborate the efficacy of CSS-ETs, be performed.
Bibliographic details Shorr A F, O'Malley P G. Continuous subglottic suctioning for the prevention of ventilator-associated pneumonia: potential economic implications. Chest 2001; 119(1): 228-235 Other publications of related interest Garcia MS, Cambronero Galach JA, Lopez Diaz J, et al. Effectiveness and cost of selective decontamination of the digestive tract in critically ill intubated patients: a randomised, double blind placebo controlled multicenter trial. American Journal of Respiratory and Critical Care Medicine 1998;158:908-16.
Atkinson S, Sieffer E, Bihari D. A prospective, randomised, double blind controlled clinical trial with enteral immunonutrition in the critically ill. Critical Care Medicine 1998;26:1164-72.
Indexing Status Subject indexing assigned by NLM MeSH Cohort Studies; Cost Savings; Critical Care /economics; Cross Infection /economics /prevention & Humans; Intubation, Intratracheal /economics /instrumentation; Models, Economic; Pneumonia, Bacterial /economics /prevention & Suction /economics; Ventilators, Mechanical; control; control AccessionNumber 22001000416 Date bibliographic record published 30/04/2004 Date abstract record published 30/04/2004 |
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