Effects of pulmonary gas embolism on circulation and respiration in the dog

Abstract

It was found in previous investigations that during venous gas infusion at low rates (1--5 ml/min-1) circulatory and respiratory variables reached a constant level after about 10--15 min. The present study demonstrates that this steady state can be disturbed by changing the composition of the breathing gas mixture. Alteration from air to 21% O2 in helium rapidly increased the embolic effects up to a maximum within 1.5--2 min; in the next 5--8 min the circulatory and respiratory variables returned to their previous levels during air breathing. Reverse effects occurred when changing from 21% O2 in helium to air. Similar phenomena were seen after switching from air to pure oxygen and from 21% O2 helium to pure oxygen. However, the extent of the circulatory and respiratory changes differed depending on the composition of the respective alternating breathing gas mixtures and on the initial embolic level as determined by infusion rate and kind of infusion gas. Gas movements between intravascular bubbles and alveolar space might be responsible for these changes.

Pathophysiology of Decompression Sickness

“…[90][91][92][93][94][95][96][97] The time course for subsequent bubble resolution by diffusion into the alveoli is inversely proportional to the volume of embolic gas 96 but in the case of air can be accelerated by oxygen breathing. 95,98 In vivo, it is possible to establish a steady state in which the rate of venous gas infusion is equaled by its clearance by the lungs.…”

“…95,98 In vivo, it is possible to establish a steady state in which the rate of venous gas infusion is equaled by its clearance by the lungs. 92 The obstruction of pulmonary vessels by bubbles may be accompanied by damage to endothelium, 46,80,99 accumulation of leukocytes, 99,100 release of thromboxanes and leukotrienes, 101 damage to the blood-lung barrier, 102 and release of vasoactive substances. 103,104 Not surprisingly, the pulmonary artery pressure is elevated, 92,105-107 a state that may be accompanied by a decrease in cardiac output.…”

“…103,104 Not surprisingly, the pulmonary artery pressure is elevated, 92,105-107 a state that may be accompanied by a decrease in cardiac output. 94,108,109 There may be hypoxemia 110 due to either a ventilationperfusion mismatch [110][111][112] or pulmonary edema generated by elevated transcapillary pressure and leakage of plasma through damaged or inflamed endothelium. 95,109,[113][114][115][116][117] Ultimately, there may be cardiac decompensation, respiratory arrest, and death.…”

Venous and Arterial Bubbles at Rest after No-Decompression Air Dives

“…Factors leading to VGE arterialization in divers with PFO are most probably increased venous return, such as during perfonnance of Valsalva maneuver (13), and increased pulmonary artery pressure (24), which was also observed after a field air dive (8), In the absence of PFO, arterialization of gas emboli was seldom documented (1,14,19), A high percentage of arterializations were reported previously during deep chamber saturation excursions from 300 to 250 m of seawater (5), Recently, we reported a high incidence of arterializations during a series of deep trimix dives (16). These events mostly occurred in divers without PFO, suggesting some alternate pathway for VGE crossover into the systemic circulation, such as puhnonary capillaries or/and inttapulmonary a-v shunts.…”

Effect of a helium and oxygen mixture on physiological parameters of rats with cerebral arterial air embolism

“…The use of gas mixtures against the background of air embolism affects circulatory parameters and the partial pressure of the gases in the vessels. The diffusion capacity and low density of helium allow it to improve oxygen transport through the membrane of the alveolar-capillary complex ( Sergysels et al, 1978 ; Verstappen et al, 1978 ; Ryan et al, 2023 ). It is important to note that helium-oxygen mixture (heliox) is used in a heated state.…”