Age effects on interrelationships between lung volume and heart rate during standing

To determine the effects of aging and posture on the relationship between respiration and heart rate (HR), we collected 5 min of lung volume and R-R interval data from 7 young (27 +/- 3 yr, mean +/- SD) and 10 old (69 +/- 6 yr) healthy humans during spontaneous breathing while they were supine (SU) and standing (ST). Lung volume and HR power spectra and transfer functions between lung volume and HR were estimated. Age and position effects and age-position interactions were determined by analysis of variance for repeated measures. Older subjects had a lower and more variable respiration rate (P < 0.03, P < 0.04), but both age groups exhibited decreased rate of respiration and increased tidal volume with ST (P < 0.05, P < 0.005). ST decreased lung volume-to-HR transfer function magnitude in both groups (P < 0.07). The more marked age-related differences were in phase angle. Both SU and ST phase angles were greater in older subjects (P < 0.003). ST decreased phase angle in young but increased phase angle in older subjects (P < 0.001). In conclusion, respiration, and respiration-HR interrelationships are altered by aging, with increased time delays between lung volume and HR and altered relationships with ST.