Respiratory Diseases — MCQs
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Apnea in an infant is cessation of breathing for:
A previously well 1-year-old infant has had a runny nose and has been sneezing and coughing for 2 days. Two other members of the family had similar symptoms. Four hours ago, his cough became much worse. On physical examination, he is in moderate respiratory distress with tachypnea and nasal flaring. Upon auscultation, he has easily audible wheezing with scattered crackles bilaterally. His arterial blood gas on room air revealed a pH of 7.46, a PaCO2 of 34 mm Hg, and a PaO2 of 75 mm Hg. His chest radiograph shows bilateral hyperinflation with flattened diaphragms and peribronchial thickening, without focal consolidation. Which of the following is the appropriate next course of action?
At what age group is Streptococcal pneumoniae most commonly encountered?
What is the most common cause of croup?
Tachypnea in a 4-month-old child is defined as a respiratory rate greater than which of the following?
What is a characteristic symptom of asthma?
What is the gold standard for diagnosing Cystic Fibrosis?
What is the treatment of choice in bronchiolitis?
What is the most common cause of stridor shortly after birth?
A 7.5-year-old girl presents with a non-productive cough and mild stridor for 3 months. Her condition was improving, but she suddenly developed wheeze, productive cough, and mild fever. Chest X-ray shows hyperlucency, and pulmonary function tests reveal an obstructive pattern. What is the most probable diagnosis?
Respiratory Diseases Indian Medical PG Practice Questions and MCQs
Question 31: Apnea in an infant is cessation of breathing for:
- A. >10 seconds
- B. >20 seconds (Correct Answer)
- C. >30 seconds
- D. >40 seconds
Explanation: **Explanation:** **1. Understanding the Correct Answer (B):** In pediatrics, particularly in neonates and infants, **Apnea** is clinically defined as the cessation of airflow for **more than 20 seconds**. However, a pause of shorter duration can also be classified as apnea if it is accompanied by **bradycardia** (heart rate <100 bpm), **cyanosis**, or **marked pallor**. This definition is crucial because infants have an immature respiratory control center in the brainstem, making them susceptible to unstable breathing patterns. **2. Analysis of Incorrect Options:** * **Option A (>10 seconds):** This is incorrect as brief respiratory pauses (5–10 seconds) are common in healthy infants and are often part of "Periodic Breathing," which is considered physiological unless associated with clinical compromise. * **Options C & D (>30 or >40 seconds):** These durations are far too long. Waiting for 30–40 seconds before diagnosing apnea would lead to severe hypoxia and potential brain injury. Medical intervention is required much earlier. **3. High-Yield Clinical Pearls for NEET-PG:** * **Apnea of Prematurity (AOP):** The most common cause of apnea in NICU settings, usually resolving by 37 weeks of post-menstrual age. * **Drug of Choice:** **Caffeine Citrate** is the preferred methylxanthine for treating apnea of prematurity due to its wide therapeutic index and long half-life. * **Periodic Breathing:** Characterized by cycles of 5–10 seconds of gasping followed by 10–15 seconds of rapid breathing. This is **normal** in preterm infants and does not require treatment. * **Primary vs. Secondary Apnea:** In neonatal resuscitation, primary apnea responds to tactile stimulation, whereas secondary apnea requires positive pressure ventilation (PPV).
Question 32: A previously well 1-year-old infant has had a runny nose and has been sneezing and coughing for 2 days. Two other members of the family had similar symptoms. Four hours ago, his cough became much worse. On physical examination, he is in moderate respiratory distress with tachypnea and nasal flaring. Upon auscultation, he has easily audible wheezing with scattered crackles bilaterally. His arterial blood gas on room air revealed a pH of 7.46, a PaCO2 of 34 mm Hg, and a PaO2 of 75 mm Hg. His chest radiograph shows bilateral hyperinflation with flattened diaphragms and peribronchial thickening, without focal consolidation. Which of the following is the appropriate next course of action?
- A. Monitoring oxygenation and fluid status (Correct Answer)
- B. Inhaled epinephrine and a single dose of steroids
- C. Acute-acting bronchodilators and a short course of oral steroids
- D. Emergent intubation, mechanical ventilation, and antibiotics
Explanation: ***Monitoring oxygenation and fluid status*** - This 1-year-old infant presents with classic **bronchiolitis** (likely **RSV**) given the viral **upper respiratory prodrome**, family clustering, and bilateral **wheeze with crackles**. - **AAP guidelines** recommend supportive care with **oxygen monitoring** and **fluid management** as first-line treatment, avoiding unnecessary interventions in mild-moderate cases. *Inhaled epinephrine and a single dose of steroids* - **Epinephrine** is indicated for **croup** (barking cough, stridor), not bronchiolitis with bilateral wheeze and crackles. - **Steroids** have no proven benefit in **bronchiolitis** and are not recommended by current pediatric guidelines. *Acute-acting bronchodilators and a short course of oral steroids* - **Bronchodilators** (albuterol/salbutamol) show minimal benefit in **bronchiolitis** and are not routinely recommended in infants under 2 years. - **Oral steroids** are ineffective in viral **bronchiolitis** and may increase risk of secondary bacterial infections. *Emergent intubation, mechanical ventilation, and antibiotics* - Patient has **moderate respiratory distress** but **normal pH** (7.46) and **adequate oxygenation** (PaO2 75 mmHg), not requiring immediate intubation. - **Antibiotics** are not indicated as this is a **viral illness** (bronchiolitis) without evidence of bacterial superinfection.
Question 33: At what age group is Streptococcal pneumoniae most commonly encountered?
- A. Less than 5 years (Correct Answer)
- B. 5-15 years
- C. 20-25 years
- D. 30-40 years
Explanation: **Explanation:** *Streptococcus pneumoniae* (Pneumococcus) is the most common bacterial cause of community-acquired pneumonia (CAP) across almost all pediatric age groups. However, its highest incidence and clinical burden are seen in children **less than 5 years of age**. **Why Option A is Correct:** In children under 5, the immune system is still developing, and there is a lack of protective antibodies against various pneumococcal serotypes. This age group also has the highest rates of nasopharyngeal colonization, which serves as a precursor to invasive diseases like pneumonia, meningitis, and bacteremia. Globally, *S. pneumoniae* is a leading cause of mortality in children under 5, particularly in developing countries. **Why Other Options are Incorrect:** * **Option B (5-15 years):** While *S. pneumoniae* still occurs, the relative incidence of atypical pathogens like *Mycoplasma pneumoniae* and *Chlamydophila pneumoniae* increases in school-aged children and adolescents. * **Options C & D (Adult groups):** While *S. pneumoniae* remains the most common cause of CAP in adults, the absolute frequency of infections and the risk of invasive disease are significantly lower compared to the vulnerable under-5 pediatric population (until reaching the geriatric age group, >65 years). **High-Yield Clinical Pearls for NEET-PG:** * **Most Common Cause:** *S. pneumoniae* is the #1 cause of bacterial pneumonia in children >3 weeks of age. * **Radiology:** Classically presents as **lobar pneumonia** with air bronchograms. * **Complication:** It is the most common cause of **empyema thoracis** in children. * **Prevention:** The **Pneumococcal Conjugate Vaccine (PCV13)** is part of the National Immunization Schedule (Universal Immunization Programme) in India, given at 6 weeks, 14 weeks, and a booster at 9 months.
Question 34: What is the most common cause of croup?
- A. Haemophilus influenzae
- B. Streptococcus pneumoniae
- C. Influenza virus
- D. Parainfluenza virus (Correct Answer)
Explanation: **Explanation:** **Croup**, also known as **Laryngotracheobronchitis (LTB)**, is a common pediatric respiratory illness characterized by inflammation and narrowing of the subglottic airway. **Why Parainfluenza virus is correct:** Viral infections are responsible for the vast majority of croup cases. **Parainfluenza virus type 1** is the most common causative agent (accounting for ~75% of cases), followed by types 2 and 3. The virus causes subglottic edema, leading to the classic clinical triad of a **barking cough, inspiratory stridor, and hoarseness.** **Analysis of Incorrect Options:** * **A. Haemophilus influenzae:** Specifically *H. influenzae* type b (Hib), is the primary cause of **Acute Epiglottitis**. While it involves the upper airway, it presents more acutely with high fever, drooling, and a "cherry-red" epiglottis, rather than a barking cough. * **B. Streptococcus pneumoniae:** This is the most common cause of community-acquired bacterial pneumonia and otitis media in children, but it does not typically cause the subglottic inflammation seen in croup. * **C. Influenza virus:** While Influenza A and B can cause croup, they are less frequent than Parainfluenza. Croup caused by Influenza tends to be more severe clinically. **High-Yield Clinical Pearls for NEET-PG:** * **X-ray Finding:** The characteristic **"Steeple Sign"** (subglottic narrowing) is seen on an Anteroposterior (AP) view of the neck. * **Age Group:** Most common between **6 months and 3 years**. * **Management:** Mild cases are treated with a single dose of **Dexamethasone** (oral/IM). Severe cases with stridor at rest require **Nebulized Epinephrine** (L-epinephrine or Racemic) for rapid vasoconstriction and airway widening. * **Westley Croup Score:** Used to clinically assess the severity of the respiratory distress.
Question 35: Tachypnea in a 4-month-old child is defined as a respiratory rate greater than which of the following?
- A. 30 breaths/min
- B. 40 breaths/min
- C. 50 breaths/min (Correct Answer)
- D. 60 breaths/min
Explanation: **Explanation** The definition of tachypnea in children is based on age-specific thresholds established by the **World Health Organization (WHO)** and the **Integrated Management of Neonatal and Childhood Illness (IMNCI)** guidelines. These thresholds are critical for the clinical diagnosis of pneumonia in resource-limited settings. For a child aged **2 months to 12 months**, tachypnea is defined as a respiratory rate (RR) of **≥ 50 breaths per minute**. Since the patient in the question is 4 months old, Option C is the correct threshold. **Analysis of Options:** * **A & B (30 and 40 breaths/min):** These are within the normal resting respiratory range for an infant. While 40 breaths/min is the upper limit of normal for a child aged 1–5 years, it is not considered tachypnea for a 4-month-old. * **D (60 breaths/min):** This is the threshold for tachypnea in **neonates (infants < 2 months of age)**. **High-Yield Clinical Pearls for NEET-PG:** To accurately count the respiratory rate, the child must be calm and the count should be taken for a full **60 seconds**. The IMNCI criteria for fast breathing (Tachypnea) are: 1. **< 2 months:** ≥ 60 breaths/min 2. **2 months to 12 months:** ≥ 50 breaths/min 3. **12 months to 5 years:** ≥ 40 breaths/min 4. **> 5 years:** > 20–25 breaths/min (Adult standards begin to apply) **Note:** In the presence of cough or breathing difficulty, tachypnea is the most sensitive clinical sign for identifying pneumonia in children under five.
Question 36: What is a characteristic symptom of asthma?
- A. Clubbing
- B. Wheezing (Correct Answer)
- C. Stridor
- D. Bradycardia
Explanation: **Explanation:** **Asthma** is a chronic inflammatory airway disease characterized by reversible airway obstruction, bronchial hyperresponsiveness, and airway remodeling. **Why Wheezing is the Correct Answer:** Wheezing is a high-pitched, musical whistling sound produced by turbulent airflow through narrowed small airways (bronchioles). In asthma, this narrowing is caused by a combination of bronchospasm, mucosal edema, and mucus plugging. It is typically **expiratory**, though it can be biphasic in severe cases. **Analysis of Incorrect Options:** * **Clubbing (A):** Clubbing is **not** a feature of isolated asthma. Its presence in a patient with respiratory symptoms should prompt an investigation for chronic suppurative lung diseases (like Bronchiectasis or Cystic Fibrosis), interstitial lung disease, or malignancy. * **Stridor (C):** Stridor is a harsh, high-pitched sound caused by obstruction in the **upper airway** (larynx or trachea), such as in Croup or Foreign Body Aspiration. Asthma affects the lower airways. * **Bradycardia (D):** Asthma exacerbations typically cause **tachycardia** due to respiratory distress, anxiety, and the side effects of beta-agonist (Salbutamol) treatment. Bradycardia is an ominous, late sign indicating impending respiratory failure. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnosis:** Spirometry showing reversibility (increase in FEV1 ≥12% and ≥200ml after bronchodilator) is the gold standard. * **Silent Chest:** The disappearance of wheezing in a severe asthma attack is a "danger sign," indicating insufficient air movement to even produce a sound. * **Samter’s Triad:** Asthma, Aspirin sensitivity, and Nasal polyposis. * **Drug of Choice:** Inhaled Corticosteroids (ICS) are the mainstay of long-term management (preventers), while SABA is used for acute relief.
Question 37: What is the gold standard for diagnosing Cystic Fibrosis?
- A. Sequencing the CFTR gene (Correct Answer)
- B. Sweat chloride test
- C. Positive newborn screening test result
- D. Nasal transepithelial potential difference
Explanation: **Explanation:** The diagnosis of Cystic Fibrosis (CF) has evolved with advancements in molecular genetics. While the Sweat Chloride Test was historically considered the gold standard, current clinical guidelines and NEET-PG standards now recognize **Sequencing the CFTR gene** as the definitive "Gold Standard." **1. Why Option A is correct:** Cystic Fibrosis is an autosomal recessive disorder caused by mutations in the *CFTR* gene on chromosome 7. Identifying two pathogenic mutations (one on each allele) via full gene sequencing provides the most definitive evidence of the disease, especially in cases where sweat tests are borderline or inconclusive (e.g., atypical CF). **2. Analysis of Incorrect Options:** * **Option B (Sweat Chloride Test):** This remains the **first-line screening and diagnostic test of choice** in clinical practice. A value of **≥60 mmol/L** is diagnostic. However, it can yield false negatives in certain genotypes or false positives in conditions like malnutrition or adrenal insufficiency. * **Option C (Newborn Screening):** This involves measuring **Immunoreactive Trypsinogen (IRT)** levels. It is a screening tool, not a diagnostic one; a positive result must always be confirmed by sweat testing or genetic analysis. * **Option D (Nasal Transepithelial Potential Difference):** This is an ancillary test used in research settings or highly complex cases where both sweat tests and genetic sequencing are inconclusive. It measures the voltage across the nasal epithelium. **Clinical Pearls for NEET-PG:** * **Most common mutation:** ΔF508 (Class II mutation – defective processing/trafficking). * **Triad of CF:** Chronic sinopulmonary disease, pancreatic insufficiency, and high sweat chloride. * **Commonest cause of death:** Respiratory failure due to *Pseudomonas aeruginosa* colonization. * **Infertility:** 95% of males have Congenital Bilateral Absence of the Vas Deferens (CBAVD).
Question 38: What is the treatment of choice in bronchiolitis?
- A. Ribavirin (Correct Answer)
- B. Amantadine
- C. Vidarabine
- D. Zidovudine
Explanation: **Explanation:** **Bronchiolitis** is most commonly caused by the **Respiratory Syncytial Virus (RSV)**. While the primary management of bronchiolitis is supportive (oxygenation and hydration), **Ribavirin** is the specific antiviral agent indicated for severe cases or in high-risk infants (e.g., those with congenital heart disease or chronic lung disease). * **Why Ribavirin is correct:** Ribavirin is a guanosine analogue that inhibits viral RNA synthesis. It is administered via **small-particle aerosol (SPAG)** for 12–20 hours a day. It is the only FDA-approved antiviral specifically for RSV-induced bronchiolitis. * **Why other options are incorrect:** * **Amantadine:** An M2 ion channel inhibitor used primarily for Influenza A; it has no activity against RSV. * **Vidarabine:** An older antiviral (adenine arabinoside) previously used for Herpes Simplex Virus (HSV), now largely replaced by Acyclovir. * **Zidovudine (AZT):** A nucleoside reverse transcriptase inhibitor (NRTI) used exclusively in the treatment of HIV/AIDS. **Clinical Pearls for NEET-PG:** * **Most common cause:** RSV is responsible for >75% of cases. * **Diagnosis:** Primarily clinical; "Happy wheezer" (infant with respiratory distress but still feeding/playing) is a classic description. * **Radiology:** Hyperinflation and patchy atelectasis. * **Prophylaxis:** **Palivizumab** (a monoclonal antibody against RSV F-protein) is used for prevention in high-risk preterm infants. * **Note on Current Guidelines:** While Ribavirin is the "textbook" treatment of choice for severe RSV, modern clinical practice emphasizes that routine use is rare due to cost and toxicity; supportive care remains the mainstay.
Question 39: What is the most common cause of stridor shortly after birth?
- A. Laryngeal papilloma
- B. Laryngeal web
- C. Laryngomalacia (Correct Answer)
- D. Vocal cord palsy
Explanation: ### Explanation **Laryngomalacia** is the most common congenital anomaly of the larynx and the leading cause of stridor in infants. It is characterized by an inward collapse of the supraglottic structures (such as the epiglottis and aryepiglottic folds) during inspiration due to delayed maturation of the laryngeal cartilages. **Why Laryngomalacia is Correct:** The hallmark is **inspiratory stridor** that typically appears within the first two weeks of life. The stridor is characteristically **positional**: it worsens when the infant is supine, crying, or feeding, and improves when the infant is prone (lying on the stomach). Diagnosis is confirmed via flexible fiberoptic laryngoscopy, which shows an "omega-shaped" epiglottis. **Analysis of Incorrect Options:** * **Laryngeal Papilloma:** Caused by HPV 6 and 11, this typically presents later in childhood (2–5 years) with hoarseness and progressive airway obstruction, rather than shortly after birth. * **Laryngeal Web:** A rare congenital malformation resulting from incomplete canalization of the larynx. While it presents at birth, it usually causes a weak cry or aphonia along with stridor, and is far less common than laryngomalacia. * **Vocal Cord Palsy:** The second most common cause of neonatal stridor. It is often associated with birth trauma (recurrent laryngeal nerve injury) or CNS anomalies (Arnold-Chiari malformation), but it is statistically less frequent than laryngomalacia. **High-Yield Clinical Pearls for NEET-PG:** * **Natural History:** Most cases of laryngomalacia are self-limiting and resolve spontaneously by 18–24 months of age. * **Management:** Conservative management is the rule. Surgical intervention (**Supraglottoplasty**) is only indicated in severe cases involving failure to thrive, cor pulmonale, or severe obstructive sleep apnea. * **Associated Condition:** Gastroesophageal reflux (GERD) is frequently associated with laryngomalacia and can exacerbate the stridor.
Question 40: A 7.5-year-old girl presents with a non-productive cough and mild stridor for 3 months. Her condition was improving, but she suddenly developed wheeze, productive cough, and mild fever. Chest X-ray shows hyperlucency, and pulmonary function tests reveal an obstructive pattern. What is the most probable diagnosis?
- A. Bronchiolitis obliterans (Correct Answer)
- B. Hemosiderosis
- C. Pulmonary alveolar microlithiasis
- D. Follicular bronchitis
Explanation: **Explanation:** **Bronchiolitis Obliterans (BO)** is a chronic obstructive lung disease resulting from an insult to the lower respiratory tract, leading to inflammation and fibrosis of the small airways (bronchioles). 1. **Why it is correct:** The clinical presentation follows a classic pattern: an initial acute insult (often viral like Adenovirus or Mycoplasma) followed by a period of relative improvement, and then the development of chronic symptoms like **non-productive cough, persistent wheeze, and stridor**. The **hyperlucency** on Chest X-ray (due to air trapping) and the **obstructive pattern** on PFTs are hallmark findings of BO in children. 2. **Why other options are incorrect:** * **Hemosiderosis:** Presents with a triad of hemoptysis, iron deficiency anemia, and diffuse parenchymal infiltrates (not hyperlucency). * **Pulmonary Alveolar Microlithiasis:** A rare genetic disorder characterized by "sand-like" calcifications (microliths) within alveoli. X-ray shows a classic "sandstorm" appearance, not hyperlucency. * **Follicular Bronchitis:** Usually associated with immunodeficiency or connective tissue disorders; it typically presents with a nodular pattern on CT rather than isolated hyperlucency and obstructive PFTs. **Clinical Pearls for NEET-PG:** * **Post-infectious BO:** The most common cause in children is **Adenovirus** (Types 3, 7, and 21). * **Radiology:** Look for the **"Mosaic attenuation"** pattern on HRCT, which is the gold standard for diagnosis. * **Swyer-James-MacLeod Syndrome:** A sequela of post-infectious BO where one lung or lobe remains hyperlucent and small due to obliterated vascularity and air trapping.
Practice by Chapter
Upper Respiratory Tract Infections
Practice Questions
Lower Respiratory Tract Infections
Practice Questions
Asthma Management
Practice Questions
Cystic Fibrosis
Practice Questions
Bronchiolitis
Practice Questions
Foreign Body Aspiration
Practice Questions
Sleep-Disordered Breathing
Practice Questions
Congenital Lung Malformations
Practice Questions
Pleural Diseases
Practice Questions
Tuberculosis in Children
Practice Questions
Chronic Lung Disease in Premature Infants
Practice Questions
Pulmonary Function Testing
Practice Questions
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