Which respiratory measurement can be taken from an unconscious patient?

• A. Slow vital capacity
• B. Tidal volume
• C. Forced vital capacity
• D. Peak expiratory flow

Answer: (B)

Tidal volume refers to the amount of air that is inhaled or exhaled during normal breathing. When assessing an unconscious patient, tidal volume can be measured by observing the patient's spontaneous breathing efforts or through more controlled methods such as using a spirometer or a mechanical ventilator that records these measurements. This metric is critical for evaluating the patient's respiratory function, especially in emergency situations where unconsciousness may affect their ability to manage their airway and breathing effectively.

In contrast, slow vital capacity and forced vital capacity require the patient to exert effort, either by taking a slow deep breath and exhaling slowly or by forcefully exhaling after a deep inhalation. These measurements can be influenced heavily by the patient's ability to follow commands, which is not possible in an unconscious individual. Peak expiratory flow, similar to forced vital capacity, also requires effort and is primarily used to assess conditions such as asthma, which again is not applicable to an unconscious patient. Hence, tidal volume stands out as the appropriate measurement in such circumstances.