Chest
Validation of a Technique to Assess Maximal Inspiratory Pressure in Poorly Cooperative Patients
Section snippets
METHODS
Using a protocol approved by the investigational review board, we studied 22 cooperative intubated patients (Table 1). Consent was obtained from family members so as to keep the patients naive to the purposes of the study. The ability to fully cooperate with instructions was assessed by administering a simple command-response oriented mental status examination prior to testing:
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STATISTICAL ANALYSIS
The data obtained through naive and coached MIP maneuvers were compared for all 22 patients by a two-tailed t test analysis for paired data. A two-tailed unpaired t test was used to compare the post-coaching percentage increase of MIP for patients stratified by the use of DS. Patients also were stratified by P0.1 <2 cm H2O vs >2 cm H2O, regardless of whether DS was added or not.
RESULTS
Variances between naive and coached MIPs for all 22 patients (Table 2 and 3) were significant (p = 0.001), mean±SD values for naive and coached MIP were 48.95 ±24.83 and 55.77 ±22.42, respectively. Naive and coached values for patients not receiving DS were 38.44±21.60 and 48.36±21.03, respectively (p = 0.005). Those receiving DS had naive and coached values of 59.46 ± 24.20 and 63.18 ± 22.20, respectively (p = 0.087). Patients with values for P0.1 <2 cm of H2O prior to the naive MIP maneuver
DISCUSSION
On both physiologic and empiric grounds the MIP is believed to be an important predictor of whether patients can sustain spontaneous ventilation without mechanical support. Used alone, values of MIP that exceed 25 cm H2O have been reported to predict successful withdrawal of ventilatory support.2, 3, 4 However, no uniform technical standard for the MIP was employed in these reports, and our experience indicates that the index alone is insufficient to accurately predict success or failure of
ACKNOWLEDGMENTS
The authors would like to thank V. J. Lamb for her technical assistance concerning data collection and analysis. In addition, we would like to thank N. E. Bennett, M. D. Waring, L. G. Scherer and J. B. Hood for their assistance in manuscript preparation.
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