A person is having normal lung compliance and increased airway resistance. The most economical way of breathing for him:
**Core Concept**
The question tests the understanding of respiratory physiology, specifically the concept of lung compliance and airway resistance. Lung compliance is a measure of the lung's ability to expand and fill with air, while airway resistance refers to the opposition to airflow through the airways. In this scenario, the person has normal lung compliance but increased airway resistance.
**Why the Correct Answer is Right**
Given the increased airway resistance, the most economical way of breathing for this person is to breathe at a lower rate and with a higher tidal volume. This allows for more efficient gas exchange, as the increased tidal volume helps to compensate for the increased airway resistance. The increased airway resistance makes it more difficult to breathe at high rates, as the increased airflow would result in greater opposition to airflow. Therefore, breathing at a lower rate with a higher tidal volume is the most economical way to breathe in this scenario.
**Why Each Wrong Option is Incorrect**
* **Option A:** Breathing at a high rate with a low tidal volume would be less economical, as the increased airflow would result in greater opposition to airflow due to the increased airway resistance.
* **Option B:** Breathing at a low rate with a low tidal volume would also be less economical, as the reduced tidal volume would result in less efficient gas exchange.
* **Option C:** Breathing at a high rate with a high tidal volume would be even less economical, as the increased airflow would result in greater opposition to airflow and would require even more energy to breathe.
**Clinical Pearl / High-Yield Fact**
In patients with increased airway resistance, such as those with chronic obstructive pulmonary disease (COPD), breathing at a lower rate with a higher tidal volume can help to improve gas exchange and reduce the work of breathing.
**Correct Answer: D**