The airflow resistance sensing threshold during tidal breathing rises in old age in patients with asthma.

BACKGROUND in a previous study, we showed that the ability to detect a rise in airflow resistance at rest was reduced in some non-asthmatic subjects in old age. OBJECTIVE to determine whether airflow resistance detection is attenuated in elderly subjects with asthma. METHODS we studied 60 adult subjects with stable asthma (age range 20-88). Progressive external airflow resistance loading was used to measure the inspiratory load detection threshold (LDT) during tidal breathing at rest. RESULTS the mean inspiratory LDT was 5.57 (4.33 SD) kPa.s/l in the 20-64 age group (n=32) and 15.6 (10.1 SD) kPa.s/l in those aged 65 and above (n=28) (P<0.0001). The inspiratory LDT was significantly correlated with age (r=0.5246, P<0.00008), mainly due to the effect of higher LDTs in about half of the subjects above the age of 65 years. Expiratory LDT values and correlations were very similar to inspiratory values. CONCLUSIONS the threshold for detecting external resistive loads during tidal breathing rises in old age in some, but not all, asthmatic patients as was observed in non-asthmatic subjects. The finding has implications for treatment guidelines because some elderly subjects are likely to have reduced awareness of worsening airflow obstruction, and consequently delay their use of rescue treatments.