Allergy and Airway |

Lung Volume Indices Correlate Better With the Duration of Asthma Than Spirometry FREE TO VIEW

Kazi Rahman, MS; Anupama Tiwari; Belayneh Abejie, MPH; Vipul Jain; Jose Joseph
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UCSF, Fresno, Pulmonary and Critical Care, Fresno, CA

Chest. 2014;146(4_MeetingAbstracts):15A. doi:10.1378/chest.1990335
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SESSION TYPE: Original Investigation Slide

PRESENTED ON: Wednesday, October 29, 2014 at 08:45 AM - 10:00 AM

PURPOSE: Persistent asthma symptoms have been associated with chronic airway inflammation. Further, longer duration of asthma may portend small airway remodeling. However, Spirometry has not been useful in assessing small airway dysfunction. Recently, we reported abnormal lung volume indices in presence of normal spirometry variables in mild to moderate persistent asthma. In this prospective cross sectional study, we investigated the association between lung volume indices and chronicity of asthma.

METHODS: Subjects with asthma symptoms for more than a year and on therapy were included. Subjects consented for study, had a full lung function done within 11 months and were administered a questionnaire. Further, subjects’ charts were reviewed for additional data. Exclusion criteria: DLCO <70%, presence of CHF, any lung parenchymal disease and pregnancy. Data was analyzed using general linear model. Outcome variables were FEV1/FVC ratio and RV/RLC ratio. Fixed factors: gender, ethnicity, and tobacco use. Co-variables: age, height, weight and asthma duration. Full factor analysis with interactions was used.

RESULTS: Mean age of 95 patients was 57.14 years SD±15.55 with 33% male and 66% female. Ethnicity was Caucasian 64%, Hispanic 28% and others 10%. Smoking status was non-smokers 67%, current smokers 5% and ex-smokers 27%. Mean asthma duration was 21.75 years SD±18.60. The Mean FEV1% predicted was 82.19 SD±21.65, FEV1/FVC ratio 73.59 SD±10.31; RV% predicted 118.85 SD±30.07 and RV/TLC was 42.48 SD±8.55. When FEV1/FVC ratio was used as a dependent variable, the model was not significant (p 0.122). However, when RV/TLC ratio was used as a dependent variable, the following variables were found to be significant: Age. ß 0.27 CI 95% (0.17 - 0.38) P <0.001; duration of asthma. ß 0.15 CI 95% (0.07 - 0.24) p <0.001. There were no significant interactions among gender, ethnicity and smoking.

CONCLUSIONS: Abnormal RV/TLC ratio was significantly associated with longer duration of asthma; FEV1/FVC was not.

CLINICAL IMPLICATIONS: RV/TLC may be a better indicator for assessing small airway dysfunction related to chronicity of asthma than FEV1/FVC.

DISCLOSURE: The following authors have nothing to disclose: Kazi Rahman, Anupama Tiwari, Belayneh Abejie, Vipul Jain, Jose Joseph

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