Chest
Clinical Investigations in Critical CarePrediction of Minimal Pressure Support During Weaning From Mechanical Ventilation
Section snippets
MATERIAL AND METHODS
Seven patients were studied at the time that they were considered weanable by their primary physicians. There were five male and two female subjects. The mean age of the patients was 71 years (range, 35 to 84 years) and the mean time of intubation was 7.5 days (range, 2 to 12 days). Three of the patients had pneumonia; one each had COPD, interstitial lung disease, and congestive heart failure, respectively, and one of the patients had taken a drug overdose. All patients were ventilated by means
RESULTS
The mean PSmin was 7.0 cm H2O with a range of 4 to 10 cm H2O. The mean VT, RR, WOBpat, PTP, and PEEPi are shown in Table 2. As the level of pressure support was decreased, the WOBpat increased (Fig 1). Progressive increases in the WOBpat were noted in the FB and CPAP modes of ventilation. With the ETT in position, but with the patients off the ventilator, WOBpat was less than CPAP. Immediately post-EXT, the WOBpat increased as compared with breathing through the ETT. This change was evident in
DISCUSSION
We found that a predictor of PSmin overestimates the PS required to simulate spontaneous breathing in our patients immediately post-EXT. Moreover, contrary to expectations, we found that the WOBpat during spontaneous breathing during EXT was higher than spontaneous breathing through the ETT. Abnormalities in the flow volume loops of these patients post-EXT suggest that upper airway abnormalities are a possible source of the increased WOB post-EXT.
The formula PIFR × R gives an estimate of the
ACKNOWLEDGMENTS:
The authors acknowledge the support of Bicore Monitoring Systems who provided the monitor and the esophageal catheters. We also acknowledge the secretarial support of Linda L. Randolph.
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Manuscript received May 6; revision accepted August 25