Objective To explore the clinical value of measuring angle alpha ( α) in the descending limb of maximum expiratory flow-volumem ( MEFV) curve in chronic obstructive pulmonary disease ( COPD) and bronchial asthma. Methods From MEFV curves, angle αand other parameters were measured in 157 individuals with COPD and 149 patients with asthma who received pulmonary function test in Zhongshan Hospital, from November 2008 until December 2009. The results were grouped and analyzed.The area under ROC curve of the angle αwas measured in the patients with COPD and compared with asthma. Results The angle αlessened with the increasing degree of airway obstruction in the patients with COPD and asthma( P lt;0. 01, P gt;0. 05) . Tangent( 180 - α) and FEV1. 0 were correlated either in the COPD group or in the asthma group( r = - 0. 640, P =0. 000; r = - 0. 206, P = 0. 012) . There was no statistical difference in the angle α between the COPD group and the asthma group when the patients had mild obstructive ventilation disorders( P =0. 177) . The angle αin the COPD group was smaller than that in the asthma group when the patients had moderate and severe obstructive ventilation disorders( P =0. 000, P =0. 000) . Area under ROC curves of the angle αin the patients with COPD who had mild, moderate and severe obstructive ventilation disorders were 0. 431, 0. 846 and 0. 928 respectively. In moderate obstructive ventilation disorders, the optimal diagnostic cutoff point was 135. 5 degree which was capable of differentiating COPD and asthma with a sensitivity of 81. 7% , a specificity of 74. 2% , a positive predictivevalue of 75. 4% , and a negative predictive value of 80. 7% . In severe obstructive ventilation disorders, the optimal diagnostic cutoff point was 129. 5 degree with a sensitivity of 87. 5% , a specificity of 84. 0% , a positive predictive value of 94. 3% , and a negative predictive value of 77. 8% . Conclusions Angle αin the descending limb of MEFV curve can assess the degree of airway obstruction in COPD, whereas it just reflect the presence of airway obstruction in asthma. Differences in Angle αare associated with pathological and pathophysiological differences between COPD and asthma, which will help for deffirentiating diagnosis.
Objective To establish amedical reference for adult pulmonary function parameters and a normal FEV1 /FVC% pred in population of Shanghai. Methods Subjects who underwent routine physical examination were initially screened and those who met enrollment criteria with age over 18 years old were required to underwent pulmonary function tests in Zhongshan Hospital from June 2009 to February 2010. After screening of 450 subjects, a total of 240 subjects with normal pulmonary function and 120 subjects with mild small airway abnormalities were enrolled in this study according to the prediction equations established in1988. All subjects were assigned into 6 groups according to their age with30 males amd 30 females in each group. Pulmonary function parameters including VC, FVC, FEV1 , FEV1 /FVC, PEF, FEF25% , FEF50% , FEF75% , RV, FRC, TLC, RV /TLC, DLCO, and KCO were collected for analysis. New prediction equations for the above 14 parameters were established by parameters of anthropometry. The medical reference ranges of 14 parameters were calculated according to the newprediction equations. The normal FEV1 /FVC%pred was also calculated. Results New prediction equations for normal adult pulmonary function parameters in Shanghai were established. DLCO =5.206 +4. 314 ×gender ( “male”= 1, “female”=0) - 0. 144 ×age( y) +0. 098 × height( cm) +0. 082 ×weight( kg) , KCO =9. 346 - 0. 026 ×age( y) - 0. 031 ×height( cm) +0. 025 ×weight( kg) .The LLN( P5) of VC, FVC, FEV1 , FEV1 /FVC, the LLN( P2. 5 ) and the upper limit of normal value ( P97. 5) of FRC, TLC, RV, RV/TLC were calculated. The LLN( P5) of FEV1 /FVC = 101. 924 - 0. 144 × age ( y) - 0. 118 ×high( cm) . The lower normal limit of FEV1 /FVC% pred was 92% . Conclusions This is the first time to have the medical reference of FEV1 /FVC% pred in China, and new prediction equations for DLCO in Shanghai. The LLN of FEV1 /FVC or FEV1 /FVC% pred lt;92% can be used as diagnostic criteria for obstructive ventilation disorder. Instead of using FEV1% pred lt; 80% , FEV1 lt; LLN can be used as diagnostic criteria for mild ventilation disorder.