EFFECTS OF A PATENT FORAMEN OVALE ON ARTERIAL SATURATION DURING EXERCISE AND ON CARDIOVASCULAR-RESPONSES TO DEEP BREATHING, VALSALVA MANEUVER, AND PASSIVE TILT - RELATION TO HISTORY OF DECOMPRESSION ILLNESS INDIVERS

Objective-To determine whether the presence of a patent foramen ovale could result in significant arterial desaturation and affect the respo nses of heart rate and blood pressure to physiological manoeuvres and to determine whether responses differed between those with and those w ithout prior clinical events associated with a patent foramen ovale. D esign-Blind controlled study. Setting-Teaching hospital. Patients-Dive rs with a large patent foramen ovale shown by contrast echocardiograph y and divided into those who had neurological decompression illness th at started within 30 minutes of surfacing (group 1), those who had no history of decompression illness (group 2), and age and sex matched co ntrol divers who had no evidence of intracardiac shunts (group 3). Mai n outcome measures-The change in percentage haemoglobin oxygen saturat ion during treadmill exercise and the response of heart rate and blood pressure to physiological manoeuvres. Results-There were no significa nt differences between the three groups but two divers in group 1 show ed clinically important desaturation during exercise and unusual blood pressure and heart rate responses to passive tilt. These divers were notable for having the greatest number of episodes and the most severe single episode of spinal cord decompression illness. Conclusion-A lar ge patent foramen ovale may be associated with clinically significant arterial desaturation and unusual responses of heart rate and blood pr essure in some healthy subjects.