Background Chest wall restriction is a common outcome in patients with ankylosing spondylitis (AS). Pulmonary function testing (PFT's) demonstrates a restrictive pattern of impairment. This impairment may be exacerbated when the subject is recumbent particularly when sleeping. It is not clear to what extent the specific FVC and FEV1 standing or lying values correlate with other commonly employed physical exam and functional outcome measures.We postulate that critical diminution of recumbent pulmonary function may have an adverse effect on sleep quality and functional outcome measures.
Objectives To determine the utility of PFT testing in AS patients. To determine if FVC and FEV1 values in standing and recumbent postures correlate with other physical and functional outcome measures in AS patients.
Methods 48 consecutive patients with AS had routine history and physical exams including the EDASMI (Edmonton Ankylosing Spondylitis Metrology Index). Standard AS questionnaires were administered BASG, BASDAI, BASFI and Epworth Sleepiness Scale was used to determine degree of daytime sleepiness as a measure of sleep quality. PFT's were performed in standing and recumbent posture. Statistical analysis was performed with SPSS software and included age, sex and smoking adjusted analysis of correlation of FVC standing, FVC lying, FVC difference between standing and lying (FVC delta), FEV 1 standing, FEV 1 lying and FEV1 difference between standing and lying (FEV1 delta).
Results The population consisted of 15 women 10 of whom were smokers and 34 men 24 of whom were smokers. The mean age for the females was 50 years with a mean disease duration of 29.2 years. The mean age of the males was 51 years with a mean disease duration of 28.7 years. Mean BMI for the females was 29.4 and for the males 28.3.
There is a statistically significant correlation in men between FVC and FEV1 with chest expansion, EDASMI, BASFI and BASDAI. Tragus to wall measurement also correlated with FVC measurements. These relationship were observed even when controlling for age and smoking history. FVC delta did not correlate with measurements of AS outcome or the Epworth Sleepiness Scale. BASFI correlates with the Epworth Sleepiness Scale.
In the female cohort, FVC correlation with EDASMI almost reached statistical significance. The FVC in female smokers correlates with the age of onset and duration of disease. However, there was no correlation of FVC or FEV 1 with measurement of chest expansion, tragus to wall measurement, BASFI or BASDAI. The FVC delta did correlate with BASFI in females who have smoked. Correlation between FEV1 delta (but not FVC delta) with the Epworth Sleepiness Scale almost reached statistical significance in the female smoking group.
Conclusions FVC and FEV1 are objective and reproducible measures of pulmonary function. In men, these correlated well with the standard physical examination measurements including chest expansion, tragus to wall measurement and the EDASMI. In turn all of these physical measurements correlated with the patient function as measured by BASFI and to a lesser extent BASDAI. Further study of this patient population is required to determine the utility of PFT testing as an independent outcome variable.
Disclosure of Interest None declared