Usefulness of arterial blood gas estimations during exercise in patients with chronic heart failure.
BACKGROUND
Coexisting cardiorespiratory disease may contribute in individual cases to the increased ventilatory response to exercise in patients with chronic heart failure.


OBJECTIVE
To characterise further the arterial blood gas response to exercise and to explore the possible uses of blood gas sampling in clinical practice in patients with chronic heart failure.


METHODS
37 patients with a primary diagnosis of chronic heart failure (age (range) 59 (45-80); left ventricular ejection fraction 24.5% (4%-44%)) underwent exercise testing with arterial blood gas analysis during exercise.


RESULTS
In 34 patients there was a small fall in arterial carbon dioxide tension from a mean (SEM) of 4.9 (0.1) kPa at rest to 4.6 (0.1) kPa at peak exercise (p < 0.001). There was no significant change in arterial oxygen tension. During the recovery period arterial oxygen tension rose from 13.3 (0.3) kPa at peak exercise to 14.8 (0.3) kPa three minutes into recovery (p < 0.001). Arterial carbon dioxide tension was unchanged. In the remaining three patients there was considerable arterial hypoxaemia on exercise, from 10.4 kPa at rest to 7.7 kPa at peak exercise. All of these patients had an alternative diagnosis (patent foramen ovale with right to left shunt during exercise, pulmonary embolic disease, and clinically unsuspected obstructive airways disease).


CONCLUSIONS
Patients with a presumptive diagnosis of chronic heart failure should undergo exercise testing with arterial blood gas analysis. Arterial hypoxaemia on exercise is rare in stable chronic heart failure. If hypoxia on exercise is detected, an alternative diagnosis should be sought.
Clark
A L
AL
Department of Cardiac Medicine, National Heart and Lung Institute, London.
Coats
A J
AJ
D000368:Aged; D000369:Aged, 80 and over; D001158:Arteries; D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000097:blood; D003937:Diagnosis, Differential; D005080:Exercise Test; D005260:Female; D006333:Heart Failure / Q000097:blood* / Q000175:diagnosis; D006344:Heart Septal Defects, Atrial / Q000097:blood / Q000175:diagnosis; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000097:blood / Q000175:diagnosis; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D011655:Pulmonary Embolism / Q000097:blood / Q000175:diagnosis
D002245:Carbon Dioxide; D010100:Oxygen