Pulmonary Function Testing — MCQs
Identify the pathology from the given flow-volume loop:
Which of the following is used for the diagnosis of asthma?
In which of the following conditions there is an increase in lung diffusion capacity?
Functional residual capacity (FRC) is defined as the volume of air remaining in the lungs at which specific moment in the respiratory cycle?
Investigation of choice in bronchiectasis?
Irreversible obstructive lung function is seen in which of the following conditions?
Which of the following statements about lung compliance is false?
Blood gas measurements of a patient show the following values: pH 7.2, pCO2 80 mm Hg, and pO2 46 mm Hg. Which of the following could be the most probable diagnosis?
A lady presents with complaints of hemoptysis, and her chest X-ray appears to be normal. What is the next best investigation?
In evaluation of a case of immotile nasal cilia, which of the following investigations should prove useful?
Pulmonary Function Testing Indian Medical PG Practice Questions and MCQs
Question 1: Identify the pathology from the given flow-volume loop:
- A. Variable extra thoracic obstruction
- B. Variable intrathoracic obstruction
- C. Fixed distal airway obstruction
- D. Fixed central airway obstruction (Correct Answer)
Explanation: ***Fixed central airway obstruction*** - This flow-volume loop shows **flattening of both the inspiratory and expiratory limbs**, creating a characteristic "box" or "square" shape. - This pattern indicates that airflow is limited equally during both inspiration and expiration, regardless of lung volume changes, which is characteristic of a **fixed central airway obstruction**. - Examples include **tracheal stenosis, tracheal tumors, or fixed goiters** compressing the trachea. *Variable extrathoracic obstruction* - Characterized by flattening of the **inspiratory limb only**, as negative intrathoracic pressure during inspiration exacerbates the obstruction. - The expiratory limb typically remains normal as positive intrathoracic pressure tends to open the airway. - Examples include **vocal cord paralysis or extrathoracic tracheal tumors**. *Variable intrathoracic obstruction* - Characterized by flattening of the **expiratory limb only**, as positive intrathoracic pressure during forced expiration collapses the airway. - The inspiratory limb usually remains normal as negative pressure helps maintain airway patency. - Examples include **intrathoracic tracheal tumors or tracheomalacia**. *Fixed distal airway obstruction* - Fixed obstructions producing the characteristic "box" pattern are typically **central (proximal) lesions in large airways**, not distal. - Distal airway obstructions (like **COPD or asthma**) produce a different flow-volume loop pattern characterized by **decreased peak expiratory flow** and "scooping" or "concave" appearance of the expiratory limb, not the flat bilateral pattern seen here.
Question 2: Which of the following is used for the diagnosis of asthma?
- A. Measurement of tidal volume
- B. End expiratory flow rate
- C. Total lung capacity
- D. FEV1 (Correct Answer)
Explanation: ***FEV1*** - **Forced expiratory volume in 1 second (FEV1)** is the gold standard spirometric parameter for asthma diagnosis - Key diagnostic criteria include: - Reduced **FEV1/FVC ratio** (<0.70 or <0.75-0.80 in adults) - **Bronchodilator reversibility**: ≥12% and ≥200 mL increase in FEV1 after inhaled short-acting β2-agonist - This reversibility distinguishes asthma from fixed obstructive diseases like COPD - Serial **peak expiratory flow (PEF)** monitoring can also demonstrate variability characteristic of asthma *Measurement of tidal volume* - **Tidal volume** measures the amount of air inhaled or exhaled during normal breathing (typically ~500 mL at rest) - Not a diagnostic parameter for asthma as it doesn't assess **airway obstruction** or **hyperresponsiveness** - May be reduced during acute exacerbations but lacks specificity for asthma diagnosis *End expiratory flow rate* - Not a standard diagnostic parameter for asthma - While **mid-expiratory flow rates** (FEF25-75%) and **peak expiratory flow (PEF)** are assessed, **FEV1** remains the primary diagnostic measure - FEV1 provides better reproducibility and standardization for diagnosis *Total lung capacity* - **Total lung capacity (TLC)** represents total lung volume after maximal inhalation - May be normal or increased in asthma due to **air trapping** and hyperinflation - Not used as a primary diagnostic criterion as asthma diagnosis focuses on demonstrating **reversible airflow limitation**, not lung volumes
Question 3: In which of the following conditions there is an increase in lung diffusion capacity?
- A. Alveolar haemorrhage (Correct Answer)
- B. Pulmonary oedema
- C. Idiopathic pulmonary fibrosis
- D. Emphysema
Explanation: ***Alveolar haemorrhage*** - The presence of **red blood cells within the alveoli** provides an additional source of **hemoglobin**, which can bind to carbon monoxide (CO) and therefore **increase the measured CO diffusion capacity (DLCO)**. - This is often seen in conditions like **Goodpasture's syndrome** or **pulmonary capillaritis**. *Pulmonary oedema* - Characterized by an **accumulation of fluid in the interstitial and alveolar spaces**, which **increases the diffusion barrier** for gases. - This fluid buildup **impairs gas exchange**, leading to a **decrease in DLCO**. *Idiopathic pulmonary fibrosis* - This condition involves **thickening and scarring of the alveolar-capillary membrane**, which significantly **increases the diffusion distance** for gases. - The resultant **fibrosis and destruction of capillaries** lead to a **marked decrease in DLCO**. *Emphysema* - Emphysema causes **destruction of alveolar walls** and the **pulmonary capillary bed**, leading to a **reduction in the surface area available for gas exchange**. - This loss of functional alveolar-capillary units results in a **decreased DLCO**.
Question 4: Functional residual capacity (FRC) is defined as the volume of air remaining in the lungs at which specific moment in the respiratory cycle?
- A. During active expiration
- B. After normal expiration (Correct Answer)
- C. At peak inspiration
- D. During active inspiration
Explanation: ***After normal expiration*** - **Functional residual capacity (FRC)** is the volume of air remaining in the lungs at the end of a **normal, passive expiration**. - It represents the sum of the **expiratory reserve volume (ERV)** and the **residual volume (RV)**. *During active expiration* - **Active expiration** involves the use of accessory muscles to force more air out of the lungs than during normal expiration. - This process would result in a lung volume less than FRC, closer to the **residual volume**. *At peak inspiration* - **Peak inspiration** represents the total lung capacity (TLC), which is the maximum volume of air the lungs can hold after a maximal inspiratory effort. - This is the largest lung volume, significantly greater than FRC. *During active inspiration* - **Active inspiration** is the process of inhaling air, which increases lung volume. - FRC is a static volume measured at the end of expiration, not during the dynamic process of inhaling.
Question 5: Investigation of choice in bronchiectasis?
- A. Bronchoscopy
- B. Chest X-ray
- C. MRI
- D. HRCT (Correct Answer)
Explanation: ***HRCT*** - **High-resolution computed tomography (HRCT)** is the gold standard for diagnosing bronchiectasis, as it provides detailed images of the bronchial tree. - It effectively visualizes the characteristic **bronchial dilation**, **lack of bronchial tapering**, and **"signet-ring" appearance** of the airways. *MRI* - **Magnetic resonance imaging (MRI)** is generally not the primary imaging modality for bronchiectasis due to its lower spatial resolution compared to CT for lung parenchyma. - While it can provide functional information, it is not as effective in visualizing the characteristic anatomical changes of bronchiectasis. *Bronchoscopy* - **Bronchoscopy** is an invasive procedure primarily used to identify the cause of bronchiectasis (e.g., foreign body, infection, endobronchial obstruction) or for therapeutic lavage. - It is not the initial diagnostic investigation of choice for confirming the presence and extent of bronchiectasis itself. *Chest X-ray* - A **chest X-ray** may show non-specific findings such as increased bronchial wall opacity or tram-track lucencies, which are suggestive of bronchiectasis but not definitive. - It lacks the sensitivity and specificity of HRCT to confirm the diagnosis and delineate the extent of the disease.
Question 6: Irreversible obstructive lung function is seen in which of the following conditions?
- A. Asthma
- B. COPD (Correct Answer)
- C. Pleural effusion
- D. Kyphoscoliosis
Explanation: ***COPD*** - **Chronic Obstructive Pulmonary Disease** (COPD) is characterized by **persistent airflow limitation** that is not fully reversible [3]. - This irreversibility is due to structural changes in the airways and parenchyma, including **emphysema** and **chronic bronchitis** [2]. *Asthma* - Asthma is characterized by **reversible airway obstruction** and hyperresponsiveness, often triggered by allergens or irritants [4]. - While it can be severe, the key distinguishing feature is that the airway limitation can be significantly reversed with bronchodilator treatment [1]. *Pleural effusion* - A pleural effusion involves the **accumulation of fluid in the pleural space**, which is outside the lung tissue. - This condition causes **restrictive lung disease** by compressing the lung, rather than obstructing the airways from within, and is usually treatable by drainage. *Kyphoscoliosis* - **Kyphoscoliosis** is a skeletal deformity of the spine that restricts lung expansion, leading to **restrictive lung disease**. - It does not directly cause an obstructive pattern within the airways, but rather impairs the mechanical ability of the lungs to inflate.
Question 7: Which of the following statements about lung compliance is false?
- A. Decreased in emphysema (Correct Answer)
- B. Total compliance is 0.2 L/cm H2O
- C. A measure of lung distensibility
- D. Change in volume per unit change in pressure
Explanation: ***Decreased in emphysema*** - This statement is **false** because **emphysema** is characterized by the destruction of elastic fibers in the lung parenchyma, which paradoxically leads to an **increase** in lung compliance. - The loss of elastic recoil makes the lungs more distensible and easier to inflate, but also impairs their ability to passively exhale. *Total compliance is 0.2 L/cm H2O* - This value represents the **normal total lung compliance** in a healthy adult (0.17 to 0.25 L/cm H2O), including both lung and chest wall compliance. - Lung compliance alone is typically around 0.2 L/cm H2O for healthy lungs. *A measure of lung distensibility* - **Compliance** is intrinsically defined as a measure of how easily the lungs or chest wall can be stretched or distended. - High compliance means the lungs are easy to inflate, while low compliance means they are stiff and difficult to inflate. *Change in volume per unit change in pressure* - This is the explicit **formula and definition of compliance** (C = ΔV/ΔP). - It quantifies the change in lung volume in response to a given change in transpulmonary pressure.
Question 8: Blood gas measurements of a patient show the following values: pH 7.2, pCO2 80 mm Hg, and pO2 46 mm Hg. Which of the following could be the most probable diagnosis?
- A. Acute exacerbation of COPD (Correct Answer)
- B. Acute bronchospasm
- C. Pulmonary embolism
- D. Chronic pneumonia
Explanation: ***Acute exacerbation of COPD*** - The patient presents with **respiratory acidosis** (pH 7.2, normal 7.35-7.45) and **hypercapnia** (pCO2 80 mm Hg, normal 35-45 mm Hg), combined with severe **hypoxemia** (pO2 46 mm Hg, normal 80-100 mm Hg) [2]. - This pattern is highly indicative of an acute exacerbation of **Chronic Obstructive Pulmonary Disease**, where worsening airflow obstruction leads to inadequate alveolar ventilation and impaired gas exchange; clinical evidence suggests long-term oxygen therapy can decrease mortality in these chronic patients [1]. *Acute bronchospasm* - While acute bronchospasm can cause hypoxemia and hypercapnia, the degree of hypercapnia (pCO2 80 mm Hg) seen here is typically more severe and prolonged than commonly observed in isolated bronchospasm. Indications for assisted ventilation in severe asthma include a rising PaCO2 above 45 mmHg [3]. - Acute bronchospasm would likely result in less pronounced acidosis and more rapid response to bronchodilator therapy, which isn't described. *Pulmonary embolism* - Pulmonary embolism typically causes **hypoxemia** and **hypocapnia** (low pCO2) due to reflex hyperventilation in response to V/Q mismatch, which contradicts the presented blood gas values [2]. - The primary defect in pulmonary embolism is an obstruction of blood flow, not a global ventilation impairment leading to severe hypercapnia. *Chronic pneumonia* - Chronic pneumonia can cause **hypoxemia** due to V/Q mismatch or shunting, but it generally leads to **hypocapnia** or normal pCO2 if the patient is able to compensate by increasing ventilation [2]. - Severe hypercapnia (pCO2 80 mm Hg) with acute acidosis is less typical for uncomplicated chronic pneumonia, unless it's a very advanced or acute severe presentation with respiratory muscle fatigue.
Question 9: A lady presents with complaints of hemoptysis, and her chest X-ray appears to be normal. What is the next best investigation?
- A. Bronchoscopy for airway evaluation
- B. High-resolution CT scan of the chest (Correct Answer)
- C. Sputum cytology for malignancy detection
- D. Pulmonary function tests for lung assessment
Explanation: ***High-resolution CT scan of the chest*** - A **normal chest X-ray** does not rule out significant pulmonary pathology as it can miss small lesions, especially in cases of hemoptysis [1]. - An **HRCT scan** is more sensitive for detecting subtle parenchymal, airway, or vascular abnormalities that could be causing bleeding [1][2]. *Bronchoscopy for airway evaluation* - While bronchoscopy is a critical tool for investigating hemoptysis, performing an **HRCT first** helps localize the bleeding source or narrow down potential etiologies, guiding the bronchoscopist [1]. - Starting directly with bronchoscopy without prior imaging might miss **parenchymal lesions** not visible in the airways and increases procedural risk if the source is unknown. *Sputum cytology for malignancy detection* - **Sputum cytology** has a low sensitivity for detecting malignancy, especially if the lesion is not centrally located or actively shedding cells. - It is often reserved for patients with clear suspicion of cancer and usually follows imaging studies that indicate a suspicious mass [1]. *Pulmonary function tests for lung assessment* - **Pulmonary function tests** assess lung volumes, airflow, and gas exchange but do not diagnose the cause of hemoptysis. - These tests are primarily used for evaluating **respiratory mechanics** and the presence of obstructive or restrictive lung diseases, not acute bleeding.
Question 10: In evaluation of a case of immotile nasal cilia, which of the following investigations should prove useful?
- A. Rhinogram
- B. Sweat sodium levels
- C. Nitric oxide test (Correct Answer)
- D. Xray nasal and paranasal sinuses
Explanation: Nitric oxide test - A low nasal nitric oxide (nNO) concentration is a key diagnostic criterion for Primary Ciliary Dyskinesia (PCD), a genetic disorder characterized by immotile or dyskinetic cilia [1]. - Nasal NO is significantly reduced in PCD patients due to impaired ciliary function, making this test highly useful for screening. *Rhinogram* - A rhinogram is a radiographic imaging technique primarily used to visualize the nasal cavity and paranasal sinuses, often to detect structural abnormalities or foreign bodies. - It does not directly assess ciliary function or provide information about ciliary motility. *Sweat sodium levels* - Elevated sweat chloride or sodium levels are the diagnostic hallmark of cystic fibrosis, a genetic condition primarily affecting mucus production. - While cystic fibrosis can cause respiratory symptoms, it does not directly lead to immotile nasal cilia in the same manner as PCD. *Xray nasal and paranasal sinuses* - An X-ray of the nasal and paranasal sinuses can reveal structural issues, such as sinus opacification or polyps, which may accompany ciliary dysfunction. - However, it does not provide direct information about the motility or structural integrity of the cilia themselves.
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