Exercise after SCUBA diving increases the incidence of arterial gas embolism

Abstract

Arterialization of gas bubbles after decompression from scuba diving has traditionally been associated with pulmonary barotraumas or cardiac defects, such as the patent foramen ovale. Recent studies have demonstrated the right-to-left passage of bubbles through intrapulmonary arterial-venous anastamoses (IPAVA) that allow blood to bypass the pulmonary microcirculation. These passages open up during exercise, and the aim of this study is to see if exercise in a postdiving period increases the incidence of arterialization. After completing a dive to 18 m for 47 min, patent foramen ovale-negative subjects were monitored via transthoracic echocardiography, within 10 min after surfacing, for bubble score at rest. Subjects then completed an incremental cycle ergometry test to exhaustion under continuous transthoracic echocardiography observation. Exercise was suspended if arterialization was observed and resumed when the arterialization cleared. If arterialization was observed a second time, exercise was terminated, and oxygen was administered. Out of 23 subjects, 3 arterialized at rest, 12 arterialized with exercise, and 8 did not arterialize at all even during maximal exercise. The time for arterialization to clear with oxygen was significantly shorter than without. Exercise after diving increased the incidence of arterialization from 13% at rest to 52%. This study shows that individuals are capable of arterializing through IPAVA, and that the intensity at which these open varies by individual. Basic activities associated with SCUBA diving, such as surface swimming or walking with heavy equipment, may be enough to allow the passage of venous gas emboli through IPAVA.

Intrapulmonary Shunt and SCUBA Diving: Another Risk Factor?

“…Recent studies potentially suggested another beneficial mechanism for the use of O 2 , closing the IPAVAs and preventing further arterialization, that is, if IPAVAs are the site of crossover in that particular instance . Indeed, the use of 100% O 2 on divers was investigated in the field in divers with open shunts, resulting from exercise, who were arterializing . The arterialization stopped almost immediately, around 90 seconds after application, as observed previously in the laboratory …”

“…This has been observed to occur at a grade of 4B on the modified Eftedal and Brubakk scale . Recently, an additional means for crossover was demonstrated in the field, that is, through opening of intrapulmonary arterial‐venous anastomoses (IPAVA) . Two prerequisites for crossover were reported: high VGE number post dive (“bubble producers”) and recruited/open IPAVAs either at rest or more frequently during exercise .…”

“…One of the proposed mechanisms of O 2 administration is to increase the washout of nitrogen from then blood, and by extension to the tissues, by increasing the concentration gradient of the inert gas at the site of gas exchange. Recent studies potentially suggested another beneficial mechanism for the use of O 2 , closing the IPAVAs and preventing further arterialization, that is, if IPAVAs are the site of crossover in that particular instance . Indeed, the use of 100% O 2 on divers was investigated in the field in divers with open shunts, resulting from exercise, who were arterializing .…”

Intrapulmonary arteriovenous anastomoses in humans – response to exercise and the environment

“…Whether or not this contributes to arterial gas embolism and subsequently decompression sickness remains controversial but exercise after a dive increases arterial gas embolism (Madden et al . ).…”

“…), post exercise (Madden et al . ) and at rest with inotropic drug infusion when breathing 100% O 2 (Bryan et al . ; Laurie et al .…”