Which of the following best explains why severe dehydration can cause an increased respiratory rate?

False: Aqueous secretions including saliva, gastric juice, and succus entericus are essential for the enzymatic hydrolysis of nutrients. Proper hydration ensures adequate production of these digestive fluids to facilitate motility and absorption. Dehydration leads to constipation and impaired nutrient uptake.

A. Because dehydration causes hypertension, increased perfusion and increased oxygen demand: Dehydration typically results in a reduction of mean arterial pressure due to decreased plasma volume. It leads to hypoperfusion rather than hyperperfusion of peripheral tissues. Increased respiratory effort is not driven by hypertensive states in this context.

B. Because dehydration directly increases lung capacity: Lung volumes and capacities are determined by anatomical structures and surfactant activity rather than hydration status. Dehydration may actually impair the viscosity of respiratory secretions, potentially complicating ventilation. It does not increase the physiological capacity of the lungs.

C. Because dehydration causes hypotension, decreased perfusion and metabolic acidosis, prompting respiratory compensation: Reduced intravascular volume leads to tissue hypoxia and a shift toward anaerobic metabolism. The resulting accumulation of lactic acid triggers the medullary respiratory centers to increase ventilation. This facilitates the clearance of carbon dioxide to normalize pH.

D. Because dehydration leads to metabolic alkalosis: Loss of free water or isotonic fluid usually predisposes the body to acidotic states through poor perfusion. Metabolic alkalosis is more commonly associated with specific electrolyte losses, such as profound vomiting. It would typically cause a decrease in respiratory rate.