Certified Registered Nurse Anesthetist (CRNA) Practice Exam

What should the gas mixture be when using CO2 laser to avoid combustion?

1. No more than 20% oxygen in nitrogen

2. No more than 30% oxygen in nitrogen or helium

3. No more than 40% oxygen in air

4. No more than 50% oxygen in argon

The correct answer is: No more than 30% oxygen in nitrogen or helium

When utilizing a CO2 laser, the gas mixture must be carefully selected to minimize the risk of combustion. The correct mixture includes no more than 30% oxygen combined with either nitrogen or helium. This limitation is essential because a higher concentration of oxygen significantly increases the risk of fire if exposed to the intense energy of the laser beam. Nitrogen serves as a non-combustible gas that dilutes the oxygen content, effectively reducing the flammability of the environment in which the laser operates. Helium is also utilized in some settings for its ability to carry heat away from the tissue while maintaining a safe environment. Therefore, ensuring that oxygen levels remain at or below 30% in this mixture is vital for maintaining safety during procedures involving CO2 lasers. In contrast, mixtures with higher oxygen concentrations, such as those mentioned in other choices, would increase the risk of combustion when exposed to the laser, making them unsuitable and dangerous for use in such procedures.