Which of the following pulmonary volume can't be measured by spirometer directly ?

Options

A. Tidal volume
B. Vital capacity
C. Inspiratory capacity
D. Residual volume

Answer

To solve the question regarding which pulmonary volume cannot be measured directly by a spirometer, we can follow these steps:

### Step 1: Understand the Pulmonary Volumes
Familiarize yourself with the various pulmonary volumes:
- **Tidal Volume (TV)**: The amount of air inhaled or exhaled during normal breathing.
- **Vital Capacity (VC)**: The maximum amount of air that can be exhaled after a maximum inhalation.
- **Inspiratory Capacity (IC)**: The maximum amount of air that can be inhaled after a normal expiration.
- **Residual Volume (RV)**: The amount of air remaining in the lungs after a maximum exhalation.

### Step 2: Identify the Function of a Spirometer
A spirometer is a device used to measure the volume of air inhaled and exhaled by the lungs. It can measure various pulmonary volumes directly, but not all.

### Step 3: Analyze Each Option
- **Tidal Volume**: Can be measured directly by a spirometer.
- **Vital Capacity**: Can also be measured directly by a spirometer.
- **Inspiratory Capacity**: Can be measured directly by a spirometer.
- **Residual Volume**: Cannot be measured directly by a spirometer because it represents the air left in the lungs after maximum exhalation, which cannot be expelled or measured directly.

### Step 4: Conclusion
Based on the analysis, the pulmonary volume that cannot be measured directly by a spirometer is **Residual Volume**.

### Final Answer
The correct option is **Residual Volume**.

---