Compliance Practice Questions

Q: A 65-year-old man with COPD undergoes pulmonary function testing. His FEV1 is 65% predicted, and spirometry shows an obstructive pattern. A pressure-volume loop demonstrates reduced elastic recoil with increased total lung capacity. When comparing his lungs to a healthy individual, what physiological change best explains his altered compliance?

Destruction of elastic tissue in alveolar walls. ***Destruction of elastic tissue in alveolar walls*** - In **COPD/emphysema**, the degradation of **elastin fibers** by proteases leads to loss of structural integrity and **increased lung compliance**. - Reduced **elastic recoil** means the lungs are more distensible (easily inflated) but fail to collapse efficiently during expiration, causing **air trapping** and increased **Total Lung Capacity (TLC)**. *Increased alveolar surface tension from surfactant deficiency* - **Surfactant deficiency** (typical of **Neonatal Respiratory Distress Syndrome**) increases surface tension, which **decreases compliance** and causes alveolar collapse. - High surface tension makes the lungs stiff and difficult to inflate, which is the opposite of the physiology seen in this **obstructive** case. *Increased collagen deposition in interstitial spaces* - **Interstitial lung diseases** (fibrosis) involve the deposition of **collagen**, which results in stiff lungs and **decreased compliance**. - This pathology presents with a **restrictive pattern** on spirometry, characterized by reduced **TLC**, unlike the increased volumes seen in emphysema. *Bronchial smooth muscle hypertrophy* - This is a hallmark of **Asthma** and **Chronic Bronchitis**, which increases **airway resistance** during expiration rather than changing the elastic properties of the lung parenchyma. - While it contributes to an **obstructive pattern**, it does not explain the specific pressure-volume loop change of **reduced elastic recoil**. *Pulmonary vascular remodeling* - This process involves thickening of the pulmonary arteries and is associated with **pulmonary hypertension**, not primary changes in lung compliance. - While common in advanced COPD, it affects the **circulatory resistance** of the lungs rather than the **elasticity** of the alveolar units.

Q: A 57-year-old man comes to the physician because of a 2-year history of fatigue, worsening shortness of breath, and a productive cough for 2 years. He has smoked 1 pack of cigarettes daily for the past 40 years. Examination shows pursed-lip breathing and an increased anteroposterior chest diameter. There is diffuse wheezing bilaterally and breath sounds are distant. Which of the following parameters is most likely to be decreased in this patient?

Lung elastic recoil. ***Lung elastic recoil*** - The patient's presentation (long smoking history, dyspnea, pursed-lip breathing, increased AP diameter, distant breath sounds, and wheezing) is classic for **emphysema**, a form of **COPD**. - Emphysema involves the destruction of **alveolar walls** and **elastic fibers**, leading to a significant decrease in the lung's ability to passively recoil during expiration. *Thickness of small airways* - In COPD, particularly chronic bronchitis, there is often **inflammation and thickening of the small airways** due to goblet cell hyperplasia and mucus gland hypertrophy, increasing their thickness, not decreasing it. - This thickening contributes to increased airway resistance. *Work of breathing* - The **destruction of elastic recoil** in emphysema means the patient must actively use accessory muscles to exhale, significantly **increasing the work of breathing**, which is evident from pursed-lip breathing. - Patients with COPD expend much more energy to breathe than healthy individuals. *Lower airway resistance* - Emphysema, while characterized by alveolar destruction, also has an obstructive component due to **airway collapse during expiration** (loss of radial traction) and potential inflammation/mucus, which leads to **increased lower airway resistance**, not decreased resistance. - This increased resistance contributes to air trapping and wheezing. *Pulmonary vascular pressure* - Chronic hypoxia resulting from severe COPD can lead to **pulmonary vasoconstriction** and remodeling of the pulmonary arteries, causing **pulmonary hypertension** and an increase in pulmonary vascular pressure. - This is a common complication in advanced COPD, not a decreased parameter.

Q: A scientist is designing experiments to better appreciate how the lung expands. He acquires two sets of cat lungs and fills one set with saline. He plots changes in the lungs' volume with respect to pressure as shown in Image A. The pressure-volume loop of the liquid-ventilated lung is different from the gas-ventilated lung because of what property?

Increased compliance. ***Increased compliance*** - Filling the lungs with **saline eliminates the air-liquid interface**, thereby removing the surface tension forces that oppose lung expansion. - With the reduction in **surface tension**, the lung requires less pressure to achieve the same volume change, making it more compliant. *More pronounced hysteresis* - **Hysteresis** in pressure-volume loops is largely due to the changing forces involved in overcoming and forming air-liquid interfaces during inspiration and expiration, respectively. - **Saline-filled lungs** exhibit *less pronounced hysteresis* because the surface tension component, a major contributor to hysteresis, is eliminated. *Increased inspiratory pressure* - **Saline-filled lungs** generally require *less inspiratory pressure* to achieve a given volume compared to air-filled lungs because the work of overcoming surface tension is removed. - This is a direct consequence of the *increased compliance*, meaning less effort is needed for expansion. *Increased residual volume* - **Residual volume** is primarily determined by the collapsing forces of the lung parenchyma and the opposing forces of the chest wall, as well as airway closure. - While saline might subtly alter these dynamics, it does *not inherently increase the residual volume*; in fact, the lack of surface tension might allow for slightly greater collapse, though this is not the primary difference. *Reduced airway resistance* - **Airway resistance** is determined by the diameter and length of the airways and the viscosity of the gas or liquid flowing through them. - While saline is a liquid, filling the *entire lung structure with saline* fundamentally changes the mechanics, but the primary difference in the pressure-volume loop is related to **parenchymal compliance**, not directly airway resistance in the conventional sense.

Question 1

A 65-year-old man with COPD undergoes pulmonary function testing. His FEV1 is 65% predicted, and spirometry shows an obstructive pattern. A pressure-volume loop demonstrates reduced elastic recoil with increased total lung capacity. When comparing his lungs to a healthy individual, what physiological change best explains his altered compliance?

Accepted Answer

Destruction of elastic tissue in alveolar walls

Answer

Increased alveolar surface tension from surfactant deficiency

Answer

Increased collagen deposition in interstitial spaces

Answer

Bronchial smooth muscle hypertrophy

Answer

Pulmonary vascular remodeling

Question 2

A 57-year-old man comes to the physician because of a 2-year history of fatigue, worsening shortness of breath, and a productive cough for 2 years. He has smoked 1 pack of cigarettes daily for the past 40 years. Examination shows pursed-lip breathing and an increased anteroposterior chest diameter. There is diffuse wheezing bilaterally and breath sounds are distant. Which of the following parameters is most likely to be decreased in this patient?

Accepted Answer

Lung elastic recoil

Answer

Thickness of small airways

Answer

Work of breathing

Answer

Lower airway resistance

Answer

Pulmonary vascular pressure

Question 3

A scientist is designing experiments to better appreciate how the lung expands. He acquires two sets of cat lungs and fills one set with saline. He plots changes in the lungs' volume with respect to pressure as shown in Image A. The pressure-volume loop of the liquid-ventilated lung is different from the gas-ventilated lung because of what property?

Accepted Answer

Increased compliance

Answer

More pronounced hysteresis

Answer

Increased inspiratory pressure

Answer

Increased residual volume

Answer

Reduced airway resistance

Question 4

A 51-year-old man comes to the physician because of progressive shortness of breath, exercise intolerance, and cough for the past 6 months. He is no longer able to climb a full flight of stairs without resting and uses 3 pillows to sleep at night. He has a history of using cocaine in his 30s but has not used any illicit drugs for the past 20 years. His pulse is 99/min, respiratory rate is 21/min, and blood pressure is 95/60 mm Hg. Crackles are heard in both lower lung fields. An x-ray of the chest shows an enlarged cardiac silhouette with bilateral fluffy infiltrates and thickening of the interlobar fissures. Which of the following findings is most likely in this patient?

Accepted Answer

Decreased lung compliance

Answer

Increased carbon dioxide production

Answer

Decreased pulmonary vascular resistance

Answer

Increased residual volume

Answer

Decreased forced expiratory volume

Compliance — MCQs

Compliance — MCQs

On this page

Practice by Chapter

Want unlimited practice?