Reproducibility of weaning parameters. A need for standardization.

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 (VE), 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, VE, 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 x 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.