Question

Given below are two statements:
Statement I: The mean pressure in the pulmonary artery is approximately one-third that of the systemic
Statement II: The mean pressure in the pulmonary artery is one-sixth that of the systemic
In the light of the above statements, choose the most appropriate answer from the options given below

• A. Both Statement I and Statement II are correct
• B. Both Statement I and Statement II are incorrect
• C. Statement I is correct but Statement II is incorrect
• D. Statement I is incorrect but Statement II is correct

Hint:

Cardiovascular Pressures: Mean Systemic Arterial Pressure $\approx 100\text{ mmHg}$. Mean Pulmonary Arterial Pressure $\approx 15\text{ mmHg}$ ($1/6\text{th}$ of systemic).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Comparative hemodynamics: the pulmonary circulation is a high-flow, low-resistance, low-pressure vascular bed with mean arterial pressure roughly 1/6th of systemic mean arterial pressure.
Key Formula or Approach:
\[ \text{Pressure Ratio} = \frac{\text{Mean Pulmonary Artery Pressure } (\approx 15\text{ mmHg})}{\text{Mean Systemic Artery Pressure } (\approx 95 - 100\text{ mmHg})} \approx \frac{1}{6} \]

Step 2: Detailed Explanation:
In cardiovascular hemodynamics:
1. Systemic Circulation: High-resistance circuit with normal Mean Arterial Pressure (MAP) of approximately $95\text{ to 100\text{ mmHg}$} (systolic/diastolic $\approx 120/80\text{ mmHg}$).
2. Pulmonary Circulation: Low-resistance vascular bed with normal Mean Pulmonary Artery Pressure (MPAP) of approximately $15\text{ mmHg$} (systolic/diastolic $\approx 25/10\text{ mmHg}$).
3. Ratio: $\frac{15\text{ mmHg}}{95 - 100\text{ mmHg}} \approx \frac{1}{6.3} \approx \mathbf{1/6\text{th}}$.
- Therefore, mean pulmonary pressure is approximately one-sixth that of systemic pressure (Statement II is correct, Statement I is incorrect).

Step 3: Final Answer:
Thus, Statement I is incorrect but Statement II is correct, matching option (D).