Certified Hyperbaric Technologist Practice Test

At what pressure does the half-life of CO decrease to 23 minutes when breathing 100% oxygen?

1. 1 ATA

2. 2 ATA

3. 3 ATA

4. 4 ATA

The correct answer is: 3 ATA

When breathing 100% oxygen, the pressure at which the half-life of carbon monoxide (CO) decreases to 23 minutes is at 3 ATA (atmospheres absolute). At this pressure, the increased partial pressure of oxygen facilitates a more rapid elimination of carbon monoxide from the body due to enhanced uptake into the bloodstream and ultimately, faster transfer to the lungs for exhalation. As pressure increases in a hyperbaric environment, the behavior of gases, including carbon monoxide, changes significantly. At atmospheric pressures lower than 3 ATA, the elimination half-life of CO is longer, meaning that it takes more time for the body to excrete half of the absorbed carbon monoxide. The efficacy of hyperbaric oxygen therapy is attributed to this principle, where increasing the pressure optimizes the clearance of toxic gases like CO. Breathing pure oxygen under hyperbaric conditions allows for greater solubility and diffusion of oxygen in the blood, which is directly correlated with the pressure level. This mechanism explains why hyperbaric treatment can be effective for CO poisoning and highlights the importance of understanding how gas behavior varies with pressure.