Chest
Pulmonary Physiologic Test of the MonthHow Many Maneuvers Are Required to Measure Maximal Inspiratory Pressure Accurately?
Section snippets
Subjects
We analyzed raw data from 367 MIP tests performed by 178 patients (age, 14 ± 3 [SD] years; range, 4 to 25 years; 159 children and 19 adults; 53% male; weight, 45 ± 15 kg; total lung capacity, 80 ± 26% predicted, and residual volume, 154 ± 85% predicted) between 1988 to 1995. Adult subjects (age, 20 ± 2 years) performed 26 tests.
At Childrens Hospital Los Angeles, MIP evaluations are performed routinely in patients with neuromuscular diseases and musculoskeletal abnormalities. Patients had
RESULTS
Our study showed that from the same raw data, the long MIP was significantly greater than the short MIP (mean difference, 9 ± 13 cm H2O). This relationship is seen among children and adults (Fig 2), and female subjects (long MIP, 94 ± 40 cm H2O; short MIP, 84 ± 40 cm H2O; p<0.000005) and male subjects (long MIP, 87 ± 38 cm H2O; short MIP, 79 ± 38 cm H2O; p<0.000005). In fact, in 177 of 367 tests (48%), the long MIP was larger than the corresponding short MIP. The distribution of MIP results is
DISCUSSION
Our study demonstrates that MIP values calculated by the long MIP method were significantly greater than values determined by the short MIP method in children and adults, and in both male and female subjects. In almost half of the tests, the short MIP underestimated the long MIP. Therefore, performing the MIP maneuver more times resulted in higher MIP values.
The short MIP method assumes that peak performance is observed once results have been reproduced three times. Our observation that the
CONCLUSION
In conclusion, our study demonstrates that from the same raw data, the long MIP was significantly greater than the short MIP. Therefore, attempting 20 maneuvers per test, as in the long MIP method, provides a more accurate assessment of the true inspiratory muscle strength. We speculate that the difference between the long MIP and the short MIP is due to a learning effect. In patients who performed the MIP maneuver four times, with each evaluation separated by a week, there was no difference in
ACKNOWLEDGMENTS
The authors thank Margaret Wen for her invaluable assistance with data entry. We also thank Michael Stabile, MS, RPFT, and the staff at the Childrens Hospital Los Angeles Pulmonary Physiology Laboratory for their technical assistance.
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Reprint requests: Dr. Marlyn Woo, Division of Pediatric Pulmonology-mailstop 83, Childrens Hospital Los Angeles, 4650 Sunset Blvd, Los Angeles, CA 90027