Certified Hyperbaric Technologist Practice Test

When a patient is breathing air at 2 ATA, what is the partial pressure of oxygen and nitrogen?

1. 319.2 mmHg O2; 1200.8 mmHg nitrogen

2. 600 mmHg O2; 900 mmHg nitrogen

3. 400 mmHg O2; 800 mmHg nitrogen

4. 210 mmHg O2; 630 mmHg nitrogen

The correct answer is: 319.2 mmHg O2; 1200.8 mmHg nitrogen

When a patient is breathing air at 2 ATA (atmospheres absolute), the total pressure experienced by the patient doubles compared to sea level pressure, which is approximately 760 mmHg. At sea level, air is composed of about 21% oxygen and 79% nitrogen. To determine the partial pressures of both gases at 2 ATA, one can calculate as follows: 1. The total pressure at 2 ATA is 2 × 760 mmHg = 1520 mmHg. 2. The partial pressure of oxygen can be calculated as 21% of the total pressure: - Partial pressure of O2 = 0.21 × 1520 mmHg = 319.2 mmHg. 3. The partial pressure of nitrogen is calculated as 79% of the total pressure: - Partial pressure of N2 = 0.79 × 1520 mmHg = 1200.8 mmHg. This calculation shows that at 2 ATA, the partial pressure of oxygen is indeed 319.2 mmHg, and the partial pressure of nitrogen is 1200.8 mmHg, making this the correct answer to the question about the composition of gases under the specified pressure. Understanding these calculations