Abstract: Slide Presentations |

Identifying Obstruction Using A Three Second Exhalation By Extrapolating the Forced Vital Capacity (FVC) FREE TO VIEW

Saiprakash B. Venkateshiah, MD; Kevin McCarthy, RCPT; Mani S.Kavuru, MD
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Department of Pulmonary Medicine and Critical Care, Cleveland Clinic, Cleveland, OH


Chest. 2003;124(4_MeetingAbstracts):122S. doi:10.1378/chest.124.4_MeetingAbstracts.122S
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PURPOSE:  To assess the ability to extrapolate the FVC (FVCextr) from data collected during a three-second exhalation. Examine the utility of using the FEV1 to the extrapolated FVC ratio to detect obstruction.

METHODS:  330 sequential acceptable spirometry tests were obtained between 6/6/00 and 6/19/00 (I dataset) using the Jaeger Master Lab Pro (Erich Jaeger GmBh; Wurzburg, Germany). Jaeger software measured FEV2and FEV3 along with all other standard spirometric indices. Best-fit linear regression analysis generated the following equation for predicting the FVC:

FVCextr (L) = 0.261+(0.842FEV3) + [3.497{FEV3-FEV2}] (R2 =0.926).
The difference between the FVC and the FVCextr was calculated. The ratio of the FEV1 to the FVCextr was compared to the FEV1/FVC ratio lower limit of normal by NHANES III prediction to determine the sensitivity and specificity of this ratio for detecting obstruction.
The methods were also applied to a different spirometry dataset of 377 sequential acceptable spirograms obtained between 6/3/02 and 6/14/02 (II dataset).

RESULTS:  The mean (±SD) difference between the FVC and the FVCextr for the I and II datasets were 0.0006 (± 0.29) L and 0.0248 ( ± 0.24) L respectively. The sensitivity and specificity for using the FEV1/FVCextr ratio to detect obstruction were 95.7% and 85.8% {I dataset} and 93.8% and 89.1 %{II dataset}, respectively.CONCLUSIONS: The above regression extrapolates the FVC from a three-second exhalation with reasonable accuracy. The ratio of the FEV1 to this extrapolated FVC yields high levels of sensitivity for detecting obstruction.

CLINICAL IMPLICATIONS:  This model may reduce the exhalation time from six seconds to three seconds in screening efforts where office spirometry is used. In conventional spirometry, terminating the exhalation after 3 seconds may be less physically exhausting for older or impaired individuals and may be more useful in the hands of unskilled operators.

DISCLOSURE:  S.B. Venkateshiah, None.

Tuesday, October 28, 2003

2:30 PM - 4:00 PM




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