Comparison between total lung capacity and residual volume values obtained by pletysmography and single breath methods with methane.
We analyzed pulmonary function tests of twenty asthmatic patients from Gaffrée e Guinle University Hospital, classified according to Brazilian Guidelines for Asthma (2002), similar to GINA, into mild persistent or moderate (9) or severe (11) asthma. We obtained parameters from spirometry, plethysmograph (PL) and single breath technique for diffusion capacity (SB), with methane. Total lung capacity and residual volume were called TLC(PL) and RV(PL) when measured by pletysmography and TLC(SB) and RV(SB) when determined by single breath test. There were 13 women and 7 men with mean age of 47.6 years. The pulmonary dysfunction degree to FEV1/FVC was 58.8% with CI95=53.9 to 63.6. The mean values in litres for TLC(PL) (5.94) and RV(PL) (2.55) were significantly higher than for TLC(SB) (4.73) and RV(SB) (1.66). Multiple regression equations were determined for TLC(PL) e RV(PL) using only single breath values, TLC(SB) or RV(SB), and spirographic para- meters, with significant regression coefficients. However, the inclusion of spirometric parameters, except for FVC, did not improve the predicted capacity for the equations. Considering only the TLC(SB), r(2)=0.79, the equation is: TLC(PL)=(TLC(SB) *1.025)+1.088, with EPE=0.64. The regression for RV(PL), r(2) =0.23, is: RV(PL)=(RV(SB) *0.9268)+1.012. The results obtained after bronchodilation with 400 mcg of salbutamol did not improve the regression. We concluded that the SB technique did not obtain the same results as pletysmography for TLC and RV, but for TLC this difference can be predicted.
Dias
Ricardo Marques
RM
Gaffrée e Guinle University Hospital, and Laboratório de Função Pulmonar, Prócardiaco Hospital, Rua Dona Mariana 219, CEP 22280-020 Botafogo, Rio de Janeiro, RJ, Brazil.
Chacur
Fernando Hauaji
FH
Carvalho
Sonia Regina da Silva
SR
Mancini
André Luís
AL
Capuchino
Geraldo A
GA
D000328:Adult; D001249:Asthma / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008176:Lung Volume Measurements / Q000379:methods; D008297:Male; D008697:Methane; D008875:Middle Aged; D010991:Plethysmography; D012115:Residual Volume; D012119:Respiration; D014109:Total Lung Capacity
D008697:Methane