Diving Hyperb Med
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Diving rebreathers use canisters containing soda lime to remove carbon dioxide (CO2) from expired gas. Soda lime has a finite ability to absorb CO₂. Temperature sticks monitor the exothermic reaction between CO₂ and soda lime to predict remaining absorptive capacity. The accuracy of these predictions was investigated in two rebreathers that utilise temperature sticks. ⋯ When operated at even shallow depth, temperature sticks provided timely warning of significant CO₂ breakthrough in the scenarios examined. They are much less accurate during simulated exercise at surface pressure.
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Gas micronuclei are gas-filled voids in liquids from which bubbles can form at low gas supersaturation. If water is depleted of gas micronuclei, high gas supersaturation is required for bubble formation. This high gas supersaturation is required in part to overcome the Laplace pressure at the point of transition from dissolved gas to a bubble of perhaps nanometer-scale radius. ⋯ Surface nanobubbles typically have diameters less than 100 nanometers but have lifetimes that are orders of magnitude longer than would a bubble of similar dimensions. Surface nanobubbles do not grow into macroscopic bubbles when exposed to pressure waves sufficient to cause bubble formation from adventitious gas micronuclei elsewhere in the apparatus. This is surely not the last word in this new and active field of research into nanoscopic gas species; however, based on current evidence one must treat with skepticism speculation that unobserved surface nanobubbles are the gas micronuclei from which bubbles form in humans with low gas supersaturation and which underlie decompression sickness.