Pulmonary Surfactants — MCQs
Surfactant acts to maintain lung compliance by decreasing which factor?
In RDS in a child, which cells are found defective?
An elderly male on ventilator has received atracurium infusion for 3 days. He now develops epileptic fits. Probable cause for his epilepsy is:
Which of the following statements about pulmonary surfactant is correct?
A patient presents with respiratory distress and is diagnosed with panacinar emphysema. Which of the following is deficient?
Which of the following is a non-ionic contrast agent?
With reference to Respiratory Distress Syndrome (RDS), which of the following statements is false?
A 30-year-old male presents with hypoxia, cyanosis, and confusion. He is found to have methemoglobinemia. What is the most appropriate treatment?
All of the following are true about "Imiquimod" except:
What is the drug of choice for acute severe asthma?
Pulmonary Surfactants Indian Medical PG Practice Questions and MCQs
Question 1: Surfactant acts to maintain lung compliance by decreasing which factor?
- A. Surface tension (Correct Answer)
- B. Pleural fluid secretion
- C. Intrathoracic pressure
- D. Pleural pressure
Explanation: ***Surface tension*** - **Surfactant** directly reduces the **surface tension** at the air-liquid interface within the alveoli. - By lowering surface tension, surfactant prevents alveolar collapse, particularly at low lung volumes, and increases **lung compliance**. *Intrathoracic pressure* - **Intrathoracic pressure** (also known as pleural pressure) is the pressure within the chest cavity, which fluctuates with breathing. - While surfactant affects lung mechanics, it doesn't directly influence the overall intrathoracic pressure. *Pleural fluid secretion* - **Pleural fluid** lubricates the pleural surfaces and is secreted by the pleural membranes. - Surfactant's primary role is in the alveoli to reduce surface tension, not to regulate **pleural fluid secretion**. *Pleural pressure* - **Pleural pressure** is the pressure in the space between the parietal and visceral pleura. - Surfactant improves lung compliance, which indirectly affects how pressure changes during breathing, but it doesn't directly control the **pleural pressure** itself.
Question 2: In RDS in a child, which cells are found defective?
- A. Bronchial epithelium
- B. Type 2 pneumocytes (Correct Answer)
- C. Type 1 pneumocytes
- D. Clara cells
Explanation: ***Type 2 pneumocytes*** - **Type 2 pneumocytes** are responsible for producing **surfactant**, which reduces surface tension in the alveoli and prevents their collapse [2], [3]. - In **Respiratory Distress Syndrome (RDS)**, especially in premature infants, these cells are immature or insufficient, leading to **surfactant deficiency** [1]. - This is the **primary cellular defect** in RDS, making it the correct answer [2]. *Bronchial epithelium* - The **bronchial epithelium** primarily lines the conducting airways and is involved in mucociliary clearance, not surfactant production. - Defects in this epithelium are associated with conditions like **bronchitis** or **asthma**, not the primary pathogenesis of RDS. *Type 1 pneumocytes* - **Type 1 pneumocytes** are thin, flat cells that form the majority of the alveolar surface (95%) and are crucial for gas exchange. - While they are affected by the damage in RDS, their primary defect is not the cause of the disease; the underlying problem is **surfactant deficiency** from Type 2 pneumocytes [2]. *Clara cells* - **Clara cells** (now called club cells) are non-ciliated secretory cells found in the bronchioles that produce Clara cell secretory protein (CCSP). - They play a role in detoxification and immune modulation but are **not responsible for surfactant production** or the pathogenesis of RDS. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 465-466. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Respiratory Tract Disease, pp. 313-314. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, p. 466.
Question 3: An elderly male on ventilator has received atracurium infusion for 3 days. He now develops epileptic fits. Probable cause for his epilepsy is:
- A. Ventilator failure
- B. Accumulation of Atracurium
- C. Accumulation of Laudanosine (Correct Answer)
- D. Allergy to drug
Explanation: Accumulation of Laudanosine\n - Atracurium is metabolized in the body via Hofmann elimination and ester hydrolysis into laudanosine and other inactive metabolites.\n - Laudanosine is a tertiary amine that can cross the blood-brain barrier and, at high concentrations, is a CNS stimulant, potentially inducing seizures.\n\nVentilator failure\n - Ventilator failure would lead to respiratory distress and potentially hypoxia, which can cause seizures, but it's not a direct pharmacological effect of atracurium or its metabolites.\n - The question implies a drug-related cause due to prolonged atracurium infusion, making ventilator failure less likely as the probable cause for drug-induced epilepsy.\n\nAccumulation of Atracurium\n - While prolonged infusion of atracurium means continuous drug administration, atracurium itself does not typically accumulate to toxic levels in the same way as its metabolites, especially in patients with normal organ function, due to its organ-independent elimination.\n - Atracurium is a neuromuscular blocker and its accumulation would primarily lead to prolonged paralysis, not directly to epileptic fits.\n\nAllergy to drug\n - An allergic reaction to a drug typically manifests as rash, anaphylaxis, or bronchospasm, not primarily as epileptic fits, unless severe anaphylaxis leads to cerebral hypoperfusion and secondary seizure.\n - While possible, it is not the most common or direct cause of seizures associated with atracurium administration.
Question 4: Which of the following statements about pulmonary surfactant is correct?
- A. Maintain alveolar integrity (Correct Answer)
- B. Secreted by type I pneumocytes
- C. A structural protein in epithelial cells
- D. A component of mucus
Explanation: **Maintain alveolar integrity** - Pulmonary surfactant **reduces surface tension** at the air-liquid interface within the alveoli, preventing their collapse during expiration. - This function is crucial for maintaining **alveolar stability** and efficient gas exchange. *Secreted by type I pneumocytes* - Pulmonary surfactant is primarily secreted by **type II pneumocytes**, also known as great alveolar cells, not type I pneumocytes. - **Type I pneumocytes** are responsible for gas exchange due to their thin, flat structure. *A structural protein in epithelial cells* - Pulmonary surfactant is a complex mixture of **lipids (primarily phospholipids)** and proteins, not solely a structural protein. - Its primary role is functional (reducing surface tension), not structural support for epithelial cells. *A component of mucus* - Pulmonary surfactant is an independent substance found within the alveolar lining, distinct from the **mucus** produced by goblet cells in the airways. - Mucus primarily functions in trapping foreign particles and is found in larger airways.
Question 5: A patient presents with respiratory distress and is diagnosed with panacinar emphysema. Which of the following is deficient?
- A. Alpha-1 antitrypsin (Correct Answer)
- B. Surfactant
- C. Albumin
- D. Type II pneumocytes
Explanation: **Alpha-1 antitrypsin** * **Alpha-1 antitrypsin (A1AT) deficiency** is a genetic disorder that leads to the development of panacinar emphysema, especially in non-smokers or at a young age [1], [2]. * A1AT protects the lung tissue from destruction by **elastase** released by neutrophils; without it, this enzyme breaks down alveolar walls [1], [2]. *Surfactant* * **Surfactant** is responsible for reducing surface tension in the alveoli, preventing their collapse in the lungs. * A deficiency primarily causes **neonatal respiratory distress syndrome** or adult respiratory distress syndrome, not predominantly emphysema. *Albumin* * **Albumin** is a primary protein in plasma that maintains oncotic pressure and transports various substances in the blood. * A deficiency in albumin (e.g., in liver disease or malnutrition) typically leads to **edema** and impaired drug transport, not emphysema. *Type II pneumocytes* * **Type II pneumocytes** are responsible for producing and secreting surfactant, as well as acting as progenitor cells for Type I pneumocytes. * While abnormalities in these cells can lead to surfactant deficiency, the direct cause of genetic panacinar emphysema is the lack of protection against elastase, not a primary defect in pneumocyte number or function in this context.
Question 6: Which of the following is a non-ionic contrast agent?
- A. Amidotrizoate
- B. Iothalamate
- C. Ioxoglate
- D. Iohexol (Correct Answer)
Explanation: ***Iohexol*** - **Iohexol** is a well-known example of a **non-ionic, low osmolar contrast agent**. It's widely used due to its lower incidence of adverse reactions compared to ionic agents. - Non-ionic contrast agents remain as **intact molecules** in solution and do not dissociate into charged ions, contributing to their lower osmolality and better tolerability. *Amidotrizoate* - **Amidotrizoate** (also known as diatrizoate) is an **ionic, high osmolar contrast agent**. It dissociates into two ions in solution. - Due to its high osmolality, it is associated with a higher risk of adverse effects, such as **nausea**, **vomiting**, and **nephrotoxicity**. *Iothalamate* - **Iothalamate** is another example of an **ionic, high osmolar contrast agent**. It also dissociates into charged ions when dissolved. - Its use has decreased significantly with the development of safer non-ionic alternatives due to its higher potential for **adverse drug reactions**. *Ioxoglate* - **Ioxoglate** is a **dimeric, ionic contrast agent**. Although it's ionic, it has a lower osmolality than monomeric ionic agents due to its dimeric structure. - Despite being dimeric, it still dissociates into ions, distinguishing it from truly non-ionic compounds like iohexol.
Question 7: With reference to Respiratory Distress Syndrome (RDS), which of the following statements is false?
- A. Leads to respiratory distress in premature infants
- B. Is less common in babies born to diabetic mothers (Correct Answer)
- C. Is treated by administering surfactant therapy
- D. Usually occurs in infants born before 34 weeks of gestation
Explanation: ***Is less common in babies born to diabetic mothers*** - Babies born to **diabetic mothers** are at an **increased risk** of Respiratory Distress Syndrome (RDS) due to delayed lung maturation caused by **hyperinsulinemia.** - Insulin inhibits the production of **surfactant**, a substance critical for reducing surface tension in the alveoli and preventing lung collapse. - This statement is **FALSE** - RDS is actually **MORE common** in infants of diabetic mothers. *Leads to respiratory distress in premature infants* - RDS is primarily a disease of **prematurity**, resulting from a deficiency of **surfactant** in the immature lungs. - This deficiency leads to widespread **atelectasis** (lung collapse), which causes breathing difficulties immediately or shortly after birth. - This statement is **TRUE**. *Is treated by administering surfactant therapy* - **Surfactant therapy** is a cornerstone of RDS treatment, often delivered via an **endotracheal tube**. - It works by replacing the deficient natural surfactant, thereby improving **lung compliance** and reducing the work of breathing. - This statement is **TRUE**. *Usually occurs in infants born before 34 weeks of gestation* - RDS predominantly affects infants born **before 34 weeks of gestation**, as their lungs are typically not mature enough to produce sufficient surfactant. - The risk **decreases significantly** with increasing gestational age, with full-term infants rarely developing the condition. - This statement is **TRUE**.
Question 8: A 30-year-old male presents with hypoxia, cyanosis, and confusion. He is found to have methemoglobinemia. What is the most appropriate treatment?
- A. Activated charcoal
- B. Methylene blue (Correct Answer)
- C. Corticosteroids
- D. High-flow oxygen
Explanation: ***Correct: Methylene blue*** - **Methylene blue** acts as an electron acceptor in the presence of NADPH, reducing the ferric iron (Fe3+) in **methemoglobin** back to ferrous iron (Fe2+), thus reversing methemoglobinemia. - It is the **first-line treatment** for symptomatic methemoglobinemia, especially in patients with low oxygen saturation and signs of end-organ hypoxia. - Typical dose: **1-2 mg/kg IV over 5 minutes**, with improvement expected within 30-60 minutes. *Incorrect: Activated charcoal* - **Activated charcoal** is used for gastrointestinal decontamination in cases of oral poisoning by adsorbing toxins. - It does not directly treat **methemoglobinemia** or reverse the effects of toxins already absorbed into the bloodstream. *Incorrect: Corticosteroids* - **Corticosteroids** possess anti-inflammatory and immunosuppressive properties. - They are used in conditions like asthma or autoimmune disorders and have no role in the direct treatment of **methemoglobinemia**. *Incorrect: High-flow oxygen* - While oxygen delivery should be maintained, **high-flow oxygen** alone is ineffective in treating significant **methemoglobinemia**. - This is because **methemoglobin** cannot bind oxygen effectively, regardless of the partial pressure of inspired oxygen, making direct reversal with methylene blue necessary.
Question 9: All of the following are true about "Imiquimod" except:
- A. Antitumor activity
- B. Indirect antiviral activity
- C. Direct antiviral activity (Correct Answer)
- D. It releases cytokines
Explanation: ***Direct antiviral activity*** - Imiquimod is a **Toll-like receptor 7 (TLR7) agonist** that primarily works by **stimulating the immune system** to produce cytokines, which then fight viral infections and cancerous cells. - It does not directly inhibit viral replication or destroy viral particles; its action is entirely **immune-mediated**. *Antitumor activity* - Imiquimod stimulates the local immune response, leading to the production of interferons and other cytokines that can inhibit the growth of **tumor cells**, such as in basal cell carcinoma. - This activity is **indirect**, as it relies on the host immune system rather than direct cytotoxic effects on cancer cells. *Indirect antiviral activity* - As a TLR7 agonist, imiquimod prompts immune cells to release significant amounts of **cytokines** like interferon-alpha, which have potent antiviral effects. - This **enhances the body's natural defense mechanisms** against viral infections, such as those causing genital warts. *It releases cytokines* - Imiquimod's mechanism of action involves binding to **Toll-like receptor 7 (TLR7)** on immune cells like macrophages and dendritic cells. - This binding triggers a signaling cascade that results in the robust production and release of various **pro-inflammatory and anti-viral cytokines**, including interferons and TNF-alpha.
Question 10: What is the drug of choice for acute severe asthma?
- A. Short-acting beta-2 agonists (Correct Answer)
- B. Long-acting beta-2 agonists
- C. Oral theophylline
- D. Inhaled ipratropium bromide
Explanation: **Explanation:** **Short-acting beta-2 agonists (SABA)**, such as Salbutamol (Albuterol) or Terbutaline, are the drugs of choice for acute severe asthma because they provide rapid bronchodilation. They act by stimulating $\beta_2$ receptors on bronchial smooth muscle, increasing intracellular cAMP, which leads to immediate muscle relaxation. In acute settings, they are typically administered via nebulization or a metered-dose inhaler (MDI) with a spacer to ensure quick onset of action (within 5 minutes). **Why other options are incorrect:** * **Long-acting beta-2 agonists (LABA):** Drugs like Salmeterol have a slow onset of action and are used for maintenance therapy, not acute relief. (Note: Formoterol has a fast onset but is generally used in combination with ICS for maintenance and reliever therapy, not as monotherapy for acute severe attacks). * **Oral theophylline:** This has a narrow therapeutic index and a slow onset of action. It is much less effective than SABAs and carries a high risk of toxicity (arrhythmias, seizures). * **Inhaled ipratropium bromide:** This is an anticholinergic used as an *add-on* therapy to SABAs in acute severe asthma to provide synergistic bronchodilation, but it is not the first-line drug of choice. **Clinical Pearls for NEET-PG:** * **Route of choice:** Inhalation is preferred over parenteral routes due to faster action and fewer systemic side effects (like tremors and tachycardia). * **Management of Acute Severe Asthma:** The standard protocol includes high-flow oxygen, frequent SABA nebulization, and **systemic corticosteroids** (to reduce airway inflammation). * **Magnesium Sulfate:** Used intravenously in life-threatening cases that are refractory to initial treatment. * **Drug of choice for Exercise-Induced Asthma:** SABA (taken 15–20 minutes before exercise).
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free