Affiliations: University of Connecticut School of Medicine, Farmington, CT,
Washington University School of Medicine, St. Louis, MO
Correspondence to: Mark Metersky, MD, FCCP, University of Connecticut School of Medicine, Division of Pulmonary Medicine, 263 Farmington Ave, Farmington, CT 06030
To the Editor:
Mundy et al1 (September 2003) performed a very well-designed, group randomized, controlled trial investigating the benefits of early mobilization in patients admitted to the hospital with community acquired-pneumonia. They reported that early mobilization resulted in improved outcomes, specifically a 1.1-day decrease in hospital length of stay with a concomitant savings of approximately $1,000 per patient in the intervention group. I want to believe the improvement was due to the intervention, as it would provide a simple but powerful tool to improve my patient’s outcomes. But, alas, I don’t believe it.
If one examines Table 2 of this study carefully, one sees that 61% of the control (usual care) group received early mobilization and 73% of the intervention group received early mobilization, for an absolute difference of only 12% or approximately one eighth of the patient population. This means that if the intervention alone was responsible for the outcome differences noted among the entire patient population, then the magnitude of improvement due to the intervention would have to be eight times the improvement noted among the population as a whole. In other words, we would have to believe that early mobilization resulted in an 8.8-day decline in the length of stay and a cost savings of $8,800.
The above scenario is unlikely for two reasons. It is not biologically plausible that mobilization could decrease the length of stay more than the average length of stay for community-acquired pneumonia. Furthermore, if the results were this compelling, I would have expected them to have been presented.
What then could explain the results that were noted, if they were not due to the intervention? Several were appropriately noted by the authors and in the accompanying editorial. One possible explanation not noted is that the intervention group received their initial antibiotics a mean of 1.2 h quicker than the usual care group. Although not statistically significant, this may have been clinically significant, as a shorter time to initial antibiotics has been associated with improved patient outcomes.2
In conclusion, I believe that early mobilization is likely to benefit some patients with pneumonia; however, I do not believe that this study can be used as evidence of that benefit. Perhaps, if further analysis of the data from this study demonstrated that patients who actually received the intervention did better than those who did not, we would have stronger evidence in support of early mobilization.
We appreciate Dr. Metersky’s interest in our article. While studies such as this one can never define causality, we have identified a striking association between early mobilization and length of hospital stay.
As noted in our article1and the accompanying editorial by Dr. Wunderink,2the association between early mobilization and length of hospital stay for patients hospitalized with community-acquired pneumonia (CAP) may be attributable to several factors. It is worth noting that Dr. Metersky’s suggestion that the timing of antibiotics reflected an explanation is a misread of the article. The intervention group received their initial antibiotics a mean of 1.2 h later, not sooner, than the usual care group. Thus, the effect of early mobilization may be even stronger if evaluated in future studies. In prior work by Meehan et al,3 initiation of antibiotics within 8 h of arrival was associated with lower CAP mortality in elderly patients; no associations were made for timing of antibiotics with length of hospital stay.
The absolute difference in early mobilization for the two groups was 12% (73% vs 61% for the intervention and usual care groups, respectively). The additional calculations made by Dr. Metersky appear to assume a linear relationship for levels of pneumonia severity of illness and compliance with the intervention. To the best of our knowledge, there is no evidence to support this assumption. Future studies may be able to assess this as a hypothesis, along with other intriguing questions such as a potential dose effect of mobilization. Overall, we appreciate the spotlight on this provocative study and, as in the article, re-emphasize that we do not recommend that this provides sufficient evidence for early mobilization to become a standard of CAP care.
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