Effect of oxygen and heliox breathing on air bubbles in adipose tissue during 25-kPa altitude exposures

Abstract

Randsøe T, Kvist TM, Hyldegaard O. Effect of oxygen and heliox breathing on air bubbles in adipose tissue during 25-kPa altitude exposures.

Threshold Altitude for Bubble Decay and Stabilization in Rat Adipose Tissue at Hypobaric Exposures

“…It was kept patent by a continuous infusion of nonheparinized denitrogenated saline by means of a syringe pump (Sage Instruments model 341, Freedom, CA ) at a rate of 1 ml z h 2 1 . To avoid bubble formation during saline infusion at altitude, denitrogenated saline was prepared by means of boiling and subsequent storing in sterile gas-tight syringes with Luer lock ( 19 ). Mean arterial blood pressure (MAP) was measured throughout the experiment by means of a pressure transducer from Edwards Lifesciences ™ (Irvine, CA ) placed inside the chamber.…”

“…At 71 kPa, oxygen breathing caused increased growth and prolonged disappearance times of air bubbles when compared to oxygen breathing at 101.3 kPa (sea level) ( 12 ). At 25 kPa, bubbles grew even further and stabilized without disappearing ( 19 ). By means of preoxygenation, injected micro air bubbles (containing 79% N 2 ) ( 19 ) as well as injected micro oxygen ( 18 ) bubbles (containing 0% N 2 ) were studied in nitrogen-depleted rat adipose tissue at 25 kPa during continuous oxygen breathing (F I o 2 5 1).…”

“…In previous reports, micro air bubbles (containing 79% N 2 ) were injected into adipose tissue of rats decompressed from sea level and held at 71 kPa ( 12 ) or 25 kPa ( 19 ) ( ; 2,900 and ; 10,376 m above sea level) during continued oxygen breathing (F I o 2 5 1). At 71 kPa, oxygen breathing caused increased growth and prolonged disappearance times of air bubbles when compared to oxygen breathing at 101.3 kPa (sea level) ( 12 ).…”

“…At 25 kPa, bubbles grew even further and stabilized without disappearing ( 19 ). By means of preoxygenation, injected micro air bubbles (containing 79% N 2 ) ( 19 ) as well as injected micro oxygen ( 18 ) bubbles (containing 0% N 2 ) were studied in nitrogen-depleted rat adipose tissue at 25 kPa during continuous oxygen breathing (F I o 2 5 1). We found that preoxygenation enhanced air bubble disappearance and signifi cantly reduced air bubble growth when compared to nonpreoxygenated rats ( 19 ), but preoxygenation did not prevent growth of either air or oxygen bubbles ( 18 , 19 ) while at 25 kPa ( ; 10,376 m above sea level).…”

“…By means of preoxygenation, injected micro air bubbles (containing 79% N 2 ) ( 19 ) as well as injected micro oxygen ( 18 ) bubbles (containing 0% N 2 ) were studied in nitrogen-depleted rat adipose tissue at 25 kPa during continuous oxygen breathing (F I o 2 5 1). We found that preoxygenation enhanced air bubble disappearance and signifi cantly reduced air bubble growth when compared to nonpreoxygenated rats ( 19 ), but preoxygenation did not prevent growth of either air or oxygen bubbles ( 18 , 19 ) while at 25 kPa ( ; 10,376 m above sea level). Based on these reports, it is concluded that both N 2 and metabolic gases, O 2 in particular, caused growth and reduced the disappearance rate of air and oxygen bubbles in nitrogen-depleted lipid tissue at 25 kPa.…”