The Science Journal of the American Association for Respiratory Care

1996 OPEN FORUM Abstracts

RELATIONSHIP OF MAXIMUM VOLUNTARY VENTILATION WITH FEV_{1}

Debra Park, Cl EdD, RRT, Harriet Long, RRT, Bekele Afessa, MD, University Medical Center, Jacksonville, Florida.

Background: Maximum voluntary ventilation (MVV) is used to determine a person's breathing reserve. The direct MVV measurement involves a fatiguing test and it is dependent on patient training and motivation. Because of the difficulties in measuring MVV, formulas such as FEV_{1}X35 and FEV_{1}X40 have been proposed to predict the MVV. This study was undertaken to determine the relationship between the directly measured MVV and the indirect MVV calculated from the FEV_{1}. Method: The study involves the retrospective review of pulmonary function tests performed in the two year period between January 1994 and December 1995. Data collected included age, race, gender, FVC, FEV_{1}, FEV_{1}/FVC, predicted FVC%, predicted FEV_{1}%, predicted FEV_{1}/FVC%, and MVV. The presence and type of ventilatory impairment (obstructive vs restrictive) was determined according to ATS criteria. All means are expressed as ±SD. Differences between the means are compared by paired student's test using StatView 4.5 software. P values less than 0.05 were considered significant. Results: The study population included 276 Caucasian, 214 African-American, 5 Hispanic, and 5 Asian for a total of 500. There were 196 males and 304 females. Their mean age was 52.6±14.2 years. Spirometry showed that 219 (43.8%) of the subjects had normal PFT results, 200 (40.0%) had obstructive defects, and 81 (16.2%) had restrictive defects. The mean FEV_{1} was 2.21±0.89 Liters. The mean MVV was 82.43±35.59 Liters, compared to 77.40±31.03 Liters of FEV_{1}X35 (p= < .0001) and 88.45±35.49 Liters of FEV_{1}X40 (p= < .0001). The difference between the MVV and FEV_{1}X35 was less than 15% in 263 (53%) patients, 15%-25% in 112 (22%) and higher than 25% in 125 (25%). The difference between the MVV and FEV_{1}X40 was less than 15% in 255 (51%) of our patients, 15% - 25% in 114 (23%) and higher than 25% in 131 (26%). The mean MVV in our patient population could have been determined by the equation: MVV=5.564+(34.802XFEV_{1}). Conclusions: There are statistically significant discrepancies between the measured MVV and the MVV calculated from FEV_{1} in our patients. We conclude that validation studies and modifications are necessary before applying these formulas in different patient populations.

Reference: OF-96-056

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