ARTERIAL BLOOD-GASES IN ELDERLY PERSONS WITH CHRONIC OBSTRUCTIVE PULMONARY-DISEASE (COPD)

With the increasing number of elderly people in developed countries, p hysicians are often confronted with patients whose arterial oxygen ten sion, Pao(2), is lower than that of normal young adults. The normal va lues predicted in the literature for very old individuals are generall y extrapolated from younger subjects. The purpose of the present study was to obtain Pao(2) values from a large population of elderly subjec ts with normal and obstructive ventilatory function. We measured arter ial blood gases in 274 subjects, aged 65-100 yrs (mean 82 yrs), with c hronic bronchitis and moderate airways obstruction (mean forced expira tory volume in one second (FEV(1)), 53% pred), Mean Pao(2) was 10.0+/- 1.4 kPa (75.2+/-10.8 mmHg) and mean arterial carbon dioxide tension (P aco(2)) was 5.4+/-0.8 kPa (40.5+/-6.1 mmHg). Both Pao(2) and Paco(2) w ere independent of age. Blood gas abnormalities were associated with a irways obstruction: Pao(2), was positively correlated to FEV(1) and Pa co(2) was negatively correlated to FEV(1). Pao(2) was 10.8+/-1.4 kPa ( 81.5+/-10.7 mmHg) in the patients with FEV(1) greater than or equal to 90% predicted versus 9.5+/-1.3 kPa (71.5+/-10.1 mmHg) in those with F EV(1) less than or equal to 35% pred. These findings suggest that the predicted Pao(2) extrapolated from younger normal values are often err oneously underestimated. It is probably more accurate to accept as nor mal a Pao(2) of 10.6-11.3 kPa (80-85 mmHg) for all subjects over 65 yr s, irrespective of their age.