Chest
Volume 102, Issue 6, December 1992, Pages 1829-1832
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Clinical Investigations in Critical Care
Reproducibility of Weaning Parameters: A Need for Standardization

https://doi.org/10.1378/chest.102.6.1829Get rights and content

Although weaning parameters can accurately predict weaning outcome, variability of the measurements of these parameters has not been closely examined. In the current study, we examined the reproducibility of these parameters using a standardized technique. Before the weaning trial, maximal inspiratory pressure (Pimax), minute ventilation ( V˙E), respiratory frequency (f), tidal volume (Vt), rapid shallow breathing index (f/Vt), and vital capacity (VC) were obtained on three trials over a period of 15 min. The results of these parameters over three measurements were compared. There were no statistical differences in the values of Pimax, V˙E, f, Vt, and f/Vt over three trials (p=0.45, p=0.37, p=0.69, p=0.64, p=0.1, respectively). The VC was the only parameter that showed statistical differences among three trials (p<0.05). For the group, respiratory frequency had the lowest coefficient of variation (COV=SD/mean × 100 percent) at 6.7 percent while the VC had the highest COV at 19.6 percent. We concluded that most weaning parameters of breathing pattern can be measured reliably with bedside instruments using a standard technique.

Section snippets

Material and Methods

Thirty patients admitted to the medical intensive care units of Hermann Hospital in Houston, Tex, were recruited into the study. All patients had required a period of mechanical ventilation because of the inability to sustain adequate spontaneous breathing. The average age for the group was 63.5±2.75 years (mean±SE). The patients had pneumonia (n=13), ARDS (n=6), neuromuscular disease (n=5), congestive heart failure (n=2), COPD (n=2), and smoke inhalation (n=2). The average number of days that

Results

The mean values for Pimax, V˙E, f, Vt, f/t, and VC in all 30 patients were 45.9±2.8 cm H2O, 11.3±1.2 L/min, 26.8±1.6 breaths/min, 415.7±32.9 ml, 79.9±8.6 breaths/min/L, and 803.7±113.1 ml, respectively. The average value of each parameter in each trial is shown in Table 1. Vital capacities were obtained only in 13 of 30 patients because the other 17 patients were not able to follow instructions to properly perform this task. There were no statistical differences in the values of Pi

Discussion

In the current study, we demonstrated that weaning parameters were highly reproducible when measured with a standardized technique. Overall, VC was the least reproducible of all parameters. Pimax tended to be slightly less reproducible than the parameters of breathing pattern (f and Vt). There was no statistically significant difference between the COV of Pimax and that of breathing parameters. Thus, it was concluded that most weaning parameters of breathing pattern can be measured reliably

ACKNOWLEDGMENT

The author sincerely thanks Drs. Martin J. Tobin and Robert F. Lodato for their helpful suggestions in preparation of this manuscript.

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revision accepted May 7.

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