The following statements suggest the physiological characteristics of the dead space in the respiratory system, alveolar ventilation (the amount of air reaching alveoli per minute), and respiratory minute volume (RMV) in healthy individuals.

A. The alveolar ventilation is less than RMV.
B. The anatomic dead space can be estimated by the body weight of the individual.
C. At rest, the anatomic dead space and physiological dead space are identical.
D. The alveolar ventilation is higher in rapid shallow breathing than that of the slow deep breathing at the same RMV.

Which one of the following options represents the combination of correct statements?

Correct option is A

EXPLANATION-

Statement A: "The alveolar ventilation is less than RMV."
RMV (Respiratory Minute Volume) is the total volume of air breathed in and out per minute, including both the air reaching the alveoli and the air remaining in the dead space (anatomic + physiological dead space). Alveolar ventilation refers only to the volume of air that actually reaches the alveoli and participates in gas exchange. Since some of the air stays in dead space and does not participate in gas exchange, alveolar ventilation is always less than RMV.
Hence, statement A is correct.

Statement B: "The anatomic dead space can be estimated by the body weight of the individual."
Anatomic dead space is the volume of the conducting airways where no gas exchange occurs, such as the trachea and bronchi. This volume is often estimated roughly by using a formula proportional to the individual's body weight, commonly around 2.2 ml per kg of body weight. Therefore, it is standard practice to estimate anatomic dead space by body weight in clinical physiology.
Hence, statement B is correct.

Statement C: "At rest, the anatomic dead space and physiological dead space are identical."
Physiological dead space includes anatomic dead space plus any alveoli that are ventilated but not perfused with blood (no gas exchange). In healthy individuals at rest, the physiological dead space closely matches the anatomic dead space because most alveoli are well perfused and functional. This means there is minimal or no additional physiological dead space beyond the anatomic dead space.
Hence, statement C is correct.

Statement D: "The alveolar ventilation is higher in rapid shallow breathing than that of slow deep breathing at the same RMV."
At the same RMV, rapid shallow breathing increases the proportion of air remaining in the dead space and reduces the proportion reaching alveoli. Conversely, slow deep breathing minimizes dead space ventilation and increases alveolar ventilation. Therefore, alveolar ventilation is lower in rapid shallow breathing compared to slow deep breathing at the same RMV.
Hence, statement D is incorrect.

So, the correct option is (a) - A, B and C