IDC Dive Physiology & Medical Considerations 3

Question 1

Henry's Law is most relevant to scuba diving because it explains:

Accepted Answer

How much gas dissolves in a liquid at a given pressure

Answer

Henry's Law states that the amount of gas dissolved in a liquid is proportional to the partial pressure of that gas, which is why more nitrogen dissolves in a diver's blood and tissues at depth.

Question 2

Pulmonary oxygen toxicity (the Lorrain Smith effect) differs from CNS oxygen toxicity in that it:

Accepted Answer

Occurs at lower partial pressures over longer exposures and affects the lungs

Answer

Pulmonary oxygen toxicity develops from prolonged exposure to elevated but sub-CNS oxygen partial pressures (typically above 0.5 ATA), causing lung inflammation and reduced capacity over hours.

Question 3

A patent foramen ovale (PFO) increases a diver's risk of DCS primarily because:

Accepted Answer

It allows venous nitrogen bubbles to bypass the lungs and enter arterial circulation

Answer

A PFO is an opening between the right and left atria that allows venous blood — and nitrogen bubbles — to pass directly into the arterial system, potentially causing neurological DCS.

Question 4

When a diver hyperventilates before a breath-hold dive, the primary danger is:

Accepted Answer

Lowering CO2 levels, delaying the urge to breathe until the diver loses consciousness underwater

Answer

Hyperventilation reduces CO2 (the primary trigger to breathe) without increasing oxygen stores, so a breath-hold diver may become hypoxic and black out before feeling the urge to surface.

Question 5

Which cardiovascular condition presents the greatest immediate risk during strenuous scuba activities such as fighting a current?

Accepted Answer

Undiagnosed coronary artery disease with poor cardiac reserve

Answer

Undiagnosed coronary artery disease with limited cardiac reserve can lead to sudden cardiac arrest during high-exertion diving, making it the greatest immediate cardiovascular risk.

IDC - Certified Instructor Development Course Trainer Practice Test

IDC - Certified Instructor Development Course Trainer Practice Test

IDC Dive Physiology & Medical Considerations 3