Affiliations: Children’s Mercy Hospital
Kansas City, MO ,
Michigan State University
Kalamazoo Center for Medical Studies
Homnick et al (October 1998)1 conclude
that “…the flutter [device] appears to be safe, efficacious,
and cost effective for [cystic fibrosis] inpatients capable of
undertaking this type of therapy.” Unfortunately, data
inconsistencies, omissions, and inadequate power preclude support of
Fifteen subjects were admitted one time (15 hospitalizations) and 7
subjects were admitted more than one time (22 hospitalizations). This
results in a total of 37 hospitalizations. Only 33 hospitalizations
were included for analysis. Why were four (11%) of the
hospitalizations excluded from analysis, and which groups were they
Seven (32%) of their subjects provided 22 of the hospitalizations
analyzed (59 to 67%, depending on whether the hospitalizations
excluded from analysis come from the group of one-time admissions or
multiple admissions). Did the subjects admitted multiple times
alternate between the flutter device and manual chest physiotherapy
(CPT), or did they receive the same treatment each time they were
admitted? This weighting of data could have a significant impact on
Regardless of the power analysis used,1,,2 it is clear that
the sample size presented in this article falls far short of
sufficient. Therefore, while this article is an interesting preliminary
data acquisition abstract, it does not begin to support conclusions
about relative efficacy, and should not be interpreted as justification
to replace standard CPT with the flutter device in the hospital or at
Correspondence to: Martin L. Bauer, MD, FCCP, Section of
Pulmonology, Children’s Mercy Hospital, 2401 Gilham Rd, Kansas
City, MO 64108
We appreciate Dr. Bauer’s comments about our study comparing
chest physiotherapy (CPT) and the flutter device in hospitalized
patients with cystic fibrosis.1-1 We agree with Dr. Bauer’s
observation that our study was underpowered. We clearly stated that
this was a preliminary (pilot) study and our power analysis
demonstrated that much larger subject numbers would be necessary to
make definitive conclusions.
We disagree with the assertion that our study had “data
inconsistencies” and “omissions.” Dr. Bauer misinterpreted our
study design and data analysis when he stated that we excluded some
hospitalizations. We had 33 hospitalizations, not 37, and none were
excluded from analysis. Fifteen subjects had only one hospitalization.
Seven subjects had two or more admissions, representing 18
hospitalizations, not 22.
The subgroup analysis included the 15 one-time admission subjects and
the first admission of the 7 multiple-admission subjects, resulting in
a total of 22 hospitalizations. Analysis of this subgroup compared to
the 33-hospitalizations group demonstrated no differences.
Assignment to flutter device or CPT was alternated for each
hospitalization, regardless of the previous therapy received by
multiple-admission subjects. We did not analyze whether the seven
subjects received the same therapy on subsequent admissions.
We observed and stated that “the flutter [device] appears to be
safe, efficacious, and cost effective” in our study. We, of course,
would not recommend that any airway clearance technique or device be
routinely substituted for another until proven effective in clinical
trials with adequate statistical power.
Correspondence to: Douglas N. Homnick, MD, FCCP, Division
of Pediatric Pulmonology, MSU, Kalamazoo Center for Medical Studies,
1000 Oakland Dr, Kalamazoo, MI 49008; e-mail: email@example.com
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