PHYS 506 Anatomy and Physiology Respiratory MCQs Answers 2023/24

PHYS 506 Anatomy and Physiology Respiratory MCQs Answers Lung Compartments 1. A spirometer can be used to directly measure which of the following? (A) Functional residual capacity (B) Peak flow rate (C) Residual volume (D) Total lung capacity (E) Vital capacity Answer: E. A spirometer is an instrument that records the volume of air moved into and out of the lungs during breathing, and therefore can only be used to measure lung volumes and capacities that can be exchanged with the environment. Spirometry can be used to measure the vital capacity, which is the maximal amount of gas that can be expired following a maximal inspiration. Spirometry cannot be used to meaure the volume of the gas that remains in the lungs following a maximal expiration (residual volume), and thus cannot directly measure the lung capacities that contain the residual volume, that is, the functional residual capacity and the total lung capacity. The peak flow rate is the maximal rate at which the volume of gas is exhaled. The measurement of flow rate requires a pneumotach, an instrument that integrates exhaled volume to derive the flow rate, or by a peak flow meter that patients can use at home, which are calibrated to record exhaled flow rates. 2. Which of the following lung volumes or capacities can be measured by spirometry? (A) Functional residual capacity (FRC) (B) Physiologic dead space (C) Residual volume (RV) (D) Total lung capacity (TLC) (E) Vital capacity (VC) Answer: E. Residual volume (RV) cannot be measured by spirometry. Therefore, any lung volume or capacity that includes the RV cannot be measured by spirometry. Measurements that include RV are functional residual capacity (FRC) and total lung capacity (TLC). Vital capacity (VC) does not include RV and is, therefore, measurable by spirometry. Physiologic dead space is not measurable by spirometry and requires sampling of arterial PCO2 and expired CO2. 3. Which volume remains in the lungs after a tidal volume (TV) is expired? (A) Tidal volume (TV) (B) Vital capacity (VC) (C) Expiratory reserve volume (ERV) (D) Residual volume (RV) (E) Functional residual capacity (FRC) (F) Inspiratory capacity (G) Total lung capacity Answer: E. During normal breathing, the volume inspired and then expired is a tidal volume (TV). The volume remaining in the lungs alter expiration of a TV is the functional residual capacity (FRC). Respiratory Physiology 4. The volume of gas in the lungs at the end of a normal expiration is referred to as the… (A)Residual volume (RV) (B) Expiratory reserve volume (ERV) (C) Functional residual capacity (FRC) (D)Inspiratory reserve volume (IRV) (E) Total lung capacity (TLC) Answer: C. The functional residual capacity (FRC) is the volume of gas in the lungs at the end of a normal expiration. Because expiration is passive, the lung volume decreases during expiration until the equilibrium volume (i.e., FRC) is reached. The equilibrium volume represents the volume of a distensible structure when the transmural pressure (i.e., the pressure inside minus the pressure outside) is zero. The residual volume (RV) is the volume of gas in the lungs following a maximal expiration. The expiratory re-serve volume (ERV) is the volume of gas that can be forcefully expired after a normal expiration, and the inspiratory reserve volume (IRV) is the additional volume of gas that can be inspired over the tidal volume. The total lung capacity (TLC) is the volume of gas in the lungs after a maximal inspiration. 5. When all ventilatory muscles are relaxed, the volume in the lungs is at: (A)Residual volume (RV) (B) Expiratory reserve volume (ERV) (C) Functional residual capacity (FRC) (D)Inspiratory reserve volume (IRV) (E) Total lung capacity (TLC) Answer: C. Muscles works are required during inspiration and forceful expiration (IRV & ERV). FRC is determined by chest wall recoil and lung recoil pressure, not muscle contractions. 6. A person starts to breathe from a 12 L spirometer containing 10% helium at the end of a passive expiration. If, after several minutes, the helium concentration in the spirometer falls to 8% this person’s functional residual capacity (FRC) is approximately: (A)1.2 L (B) 2.4 L (C) 3.0 L (D)4.0 L (E) 4.8 L Answer: C. V2 (FRC) = V1 × [([He]initial/[He]final) – 1] = 12 × [(10/8) – 1] = 12 × 2/8 = 3 [L]. Respiratory Physiology 7. Which volume remains in the lungs after a maximal expiration? (A) Tidal volume (TV) (B) Vital capacity (VC) (C) Expiratory reserve volume (ERV) (D) Residual volume (RV) (E) Functional residual capacity (FRC) (F) Inspiratory capacity (G) Total lung capacity Answer: D. During a forced maximal expiration, the volume expired is a tidal volume (TV) plus the expiratory reserve volume (ERV). The volume remaining in the lungs is the residual volume (RV). 8. In a maximal expiration, the total volume expired is (A) Tidal volume (TV) (B) Vital capacity (VC) (C) Expiratory reserve volume (ERV) (D) Residual volume (RV) (E) Functional residual capacity (FRC) (F) Inspiratory capacity (G) Total lung capacity Answer: B. The volume expired in a forced maximal expiration is forced vital capacity, or vital capacity (VC). 9. The ventilatory capacity of a patient with respiratory disease is evaluated using spirometry. Which of the following is the correct spirometric term for the largest exhaled volume that this patient can generate during the course of pulmonary function testing? (A)Total lung capacity (TLC) (B) Inspiratory capacity (IC) (C) Forced vital capacity (FVC) (D)Inspiratory reserve volume (IRV) (E) FEV1 Answer: C. Respiratory Physiology 10. A 45-year-old man inhaled as much air as possible and then expired with a maximum effort until no more air could he expired. This produced the maximum expiratory flow-volume curve shown in the following diagram. What is the forced vital capacity of this man (in liters) . . . . . . . . .