Maximum inspiratory pressure measurements have been used for many years to help predict the ability of the intubated, mechanically ventilated patient to maintain adequate spontaneous ventilation. However, controversy still exists about the best method to employ. We report and compare the results obtained with two techniques for the performance of maximal inspiratory pressure (MIP). METHODS: Method A employed a simple airway-occlusion technique, while Method B incorporated a one-way valve that allows the patient to exhale after attempting inspiration. With each technique, measurements were made every 5 seconds for a 20-second period. Measurements were randomly performed on 50 patients who were being weaned from ventilatory support in our medical ICU. RESULTS: A statistically significant difference (p < 0.001) was found in results with the two techniques. MIP was greater with Method B than with Method A. In addition, measured MIP increased with time, regardless of method. All patients tolerated both procedures well, and no measurement was discontinued because of adverse reaction. CONCLUSION: We believe the use of a one-way valve system with airway occlusion for up to 20 seconds is an accurate and safe method of evaluating MIP in clinically stable patients in whom weaning from ventilatory support is anticipated.
Kacmarek et al. (Sun,) studied this question.