The Science Journal of the American Association for Respiratory Care

2006 OPEN FORUM Abstracts

THE IMPORTANCE of Ideal body weight for tidal volume calculation

Anthony J. Asciutto RRT, David L. Michaels RRT, Michael A. Gentile RRT FAARC, John D. Davies RRT FAARC, Neil R. MacIntyre MD FAARC.

Duke University Medical Center, Durham, NC.

Background: Studies involving both human and laboratory subjects have shown that the selection of incorrect delivered tidal volumes (Vt) can cause ventilator induced lung injury (VILI). The ARDSnet study1 showed that the group of patients receiving Vt of 6 ml/kg ideal body weight (IBW) was associated with a lower mortality compared with the group receiving Vt of 12 ml/kg IBW. The purpose of this study was to compare IBW to actual body weight (ABW) and estimate the gap in Vt based on the difference of IBW and ABW.

Methods: We retrospectively examined a sample of ventilated patients and calculated the value of delivered tidal volume over IBW during conventional mechanical ventilation. Data (Vt, IBW, ABW) were gathered on all ventilated patients in adult intensive care units over a single 12 hours shift.

Results: In 37 ventilated patients, the value of delivered tidal volume over IBW ranged from 4.9 ml/Kg to 10.5 ml/Kg. The disparity of ABW and IBW (ABW-IBW) ranged from -7 Kg to +119 Kg (p < 0.05). If tidal volume of 6 ml/Kg was applied, the estimated gap of tidal volume resulting from the difference of IBW and ABW would maximally reach 714 ml.

Conclusion: The difference between IBW and ABW is significant.  The use of IBW instead of ABW for the basis of Vt calculation resulted in lower Vt in our institution and may help reduce the incidence of VILI. 

1.  Ventilation with Lower Tidal Volumes as Compared with Traditional Tidal Volumes for Acute Lung Injury and the Acute Respiratory Distress Syndrome. The Acute Respiratory Distress Syndrome Network , N Engl J Med. 2000;342:1301-1308.

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