Certified Flight Registered Nurse (CFRN) Practice Exam

Which gas law explains the condition of a patient who feels like "ants are crawling on his skin" after diving?

1. Boyle's law

2. Dalton's law

3. Henry's law

4. Graham's law

The correct answer is: Henry's law

The situation described, where a patient experiences a sensation akin to "ants crawling on his skin" after diving, can be best understood through Henry's law. This law articulates the relationship between the amount of gas dissolved in a liquid and the partial pressure of that gas above the liquid. When divers descend, the increased pressure causes more nitrogen to dissolve into their blood and tissues. Upon ascending, if this dissolved nitrogen does not properly eliminate through breathing out, it can form bubbles in the bloodstream, leading to symptoms of decompression sickness, commonly referred to as "the bends." This condition can result in sensory disturbances, including the crawling sensation described. Thus, understanding Henry's law, which connects how gases behave under different pressures, is essential in recognizing the physiological changes that occur during and after a dive. Other laws, such as Boyle's law, focus on the relationship between pressure and volume of a gas, Dalton's law addresses the behavior of mixed gases, and Graham's law deals with the effusion rates of gas molecules, none of which specifically elucidate the sensation experienced by the diver in this scenario like Henry's law does.