A patient has an Inspiratory Capacity (IC) of 3500 mL and an Expiratory Reserve Volume (ERV) of 1200 mL.What is the patient's Vital Capacity (VC)?

A. Limit the airflow to maintain balance: Limiting airflow would reduce ventilation and impair oxygen delivery. Inspiratory muscles do not restrict airflow; instead, they adjust their force to ensure sufficient air reaches the alveoli despite resistance.

B. Relax more quickly: Rapid relaxation of inspiratory muscles would prematurely end inhalation, decreasing tidal volume and reducing the effectiveness of ventilation. Overcoming airway resistance requires sustained contraction, not faster relaxation.

C. Generate a stronger pressure gradient: Inspiratory muscles, primarily the diaphragm and external intercostals, must create a greater negative intrapulmonary pressure relative to atmospheric pressure. This stronger pressure gradient allows air to flow into the lungs despite increased airway resistance or decreased lung compliance.

D. Decrease the thoracic cavity size: Decreasing thoracic cavity size would increase intrapulmonary pressure, which would oppose inhalation. To overcome resistance, the thoracic cavity must expand, lowering intrapulmonary pressure and drawing air into the lungs.

A. It doubles: The total pressure of a gas mixture does not automatically double when combining gases. Doubling would only occur if each gas contributed an identical pressure and quantity, which is not generally the case in a mixture of different gases.

B. It remains unchanged: The total pressure of a gas mixture is directly dependent on the sum of the pressures exerted by individual gases. It cannot remain unchanged if partial pressures of the component gases vary or are combined.

C. It decreases: Total pressure decreases only if gas molecules are removed or the volume is increased. Simply adding partial pressures does not reduce total pressure; it accumulates the contributions of all gases present.

D. It equals the sum of the partial pressures: According to Dalton’s Law of Partial Pressures, the total pressure of a gas mixture is equal to the sum of the individual partial pressures of each gas in the mixture. Each gas contributes independently to the total pressure based on its mole fraction and temperature.