Is it necessary to use a noseclip in the performance of spirometry using a wedge bellows device?

There is no current consensus among published guidelines on whether noseclips are required during spirometry testing. This study investigated the effect of noseclips on spirometric measurements in patients with a range of disease. Fifty-two patients (30 male; mean age 58.0 years, range 19-78; mean FEV1 82.6% predicted, range 23.8-128.3%) performed measurements of VC, FVC and FEV1 according to ARTP/BTS guidelines (1994) using a wedge bellows spirometer (Vitalograph Model S, Bucks, U.K.). All patients performed two sets of measurements (with and without noseclips) in random order (Group 1 = noseclips first; n=30; Group 2 (without noseclips first, n=22). Tests were conducted by qualified physiologists. Measurements obtained with and without the use of noseclips were similar (mean differences FEV1 -0.030 L SD 0.210 and -0.005 L SD 0.093 for Groups 1 and 2 respectively; FVC -0.007 L SD 0.109 and -0.040 L SD 0.117; VC 0.036L SD 0.137 and -0.040 L SD 0.150) and were not dependent on patient group or previous test experience. Four patients had differences outside the 95% confidence limits for each parameter. There were no significant correlations between the differences with and without noseclips and severity of lung disease, age, smoking history, BMI or lung volume (all P > 0.100). The within patient coefficient of variation did not depend on the testing method. Use of noseclips during spirometry does not systematically affect the results obtained or the within-subject repeatability. Marked individual differences highlight the importance of maintaining consistency in the method adopted for a particular patient.