Respiratory System Practice Questions

Q: Which of the following is NOT true about COPD?

Decreased Diffusion capacity (DLco). **Explanation:** The key to answering this question lies in distinguishing between the two main components of COPD: **Chronic Bronchitis** and **Emphysema**. While both involve airway obstruction, their physiological profiles differ regarding gas exchange. **Why Option C is the Correct Answer (The "NOT True" statement):** Decreased Diffusion Capacity (DLco) is a hallmark of **Emphysema** (due to alveolar wall destruction reducing the surface area for gas exchange). However, in **Chronic Bronchitis**, the DLco is typically **normal** because the alveolar-capillary membrane remains intact. Since the term "COPD" encompasses both, and DLco is not universally decreased across all COPD phenotypes, it is the most nuanced "incorrect" general statement compared to the definitive obstructive patterns seen in the other options. **Analysis of Incorrect Options:** * **A. Reduced FEV1:** This is the gold standard for diagnosing any obstructive lung disease. Increased airway resistance leads to a significant drop in the Forced Expiratory Volume in 1 second. * **B. Increased Residual Volume (RV):** Due to "air trapping" and loss of elastic recoil, patients cannot fully exhale, leading to an increase in RV and Total Lung Capacity (TLC). * **D. Decreased MEFR:** Obstruction and premature airway closure during expiration characteristically reduce the flow rates (MEFR/PEFR). **NEET-PG High-Yield Pearls:** * **Gold Standard Diagnosis:** FEV1/FVC ratio < 0.70 post-bronchodilator. * **Pink Puffers (Emphysema):** High compliance, low DLco, severe dyspnea. * **Blue Bloaters (Chronic Bronchitis):** Normal compliance, normal DLco, cyanosis, and edema. * **Flow-Volume Loop:** Shows a characteristic "scooped-out" appearance in the expiratory limb.

Q: What is the normal pulmonary capillary pressure?

10 mm Hg. **Explanation:** The pulmonary circulation is a **low-pressure, low-resistance system** compared to the systemic circulation. The normal mean pulmonary capillary pressure is approximately **10 mm Hg** (ranging between 7–12 mm Hg). This low pressure is physiological necessity to prevent the filtration of fluid into the alveoli, ensuring efficient gas exchange. **Why 10 mm Hg is correct:** In the lungs, the Starling forces are balanced such that the capillary hydrostatic pressure (10 mm Hg) is significantly lower than the plasma colloid osmotic pressure (~28 mm Hg). This "safety factor" keeps the alveoli dry by favoring the absorption of fluid into the interstitium/capillaries rather than filtration into the air spaces. **Analysis of Incorrect Options:** * **A (5 mm Hg):** This is closer to the normal **Left Atrial Pressure** (mean ~2–5 mm Hg). While low, it does not represent the pressure within the capillary bed itself. * **C (20 mm Hg):** This value is too high for a normal capillary. A mean pulmonary capillary pressure above 18–20 mm Hg typically indicates pulmonary venous congestion or early **pulmonary edema**. * **D (32 mm Hg):** This is the average hydrostatic pressure at the arterial end of a **systemic capillary**. If pulmonary capillary pressure reached this level, massive pulmonary edema would occur instantly. **High-Yield NEET-PG Pearls:** * **Mean Pulmonary Artery Pressure (mPAP):** Normal is ~15 mm Hg. Pulmonary hypertension is defined as mPAP >20 mm Hg at rest. * **West Zones of the Lung:** Pulmonary capillary pressure varies by position; it is lowest at the apex (Zone 1) and highest at the base (Zone 3) due to gravity. * **PCWP (Pulmonary Capillary Wedge Pressure):** Measured via a Swan-Ganz catheter, it is a clinical surrogate for left atrial pressure and pulmonary capillary pressure. Normal is 6–12 mm Hg.

Q: What is the Haldane effect?

Dissociation of CO2 on oxygenation. ### Explanation The **Haldane Effect** describes the phenomenon where the oxygenation of hemoglobin in the lungs promotes the dissociation (release) of carbon dioxide from the blood. **Why Option B is Correct:** The underlying mechanism is based on the fact that **deoxygenated hemoglobin (deoxy-Hb)** has a higher affinity for $CO_2$ and acts as a better buffer for $H^+$ ions than oxyhemoglobin. 1. In the lungs, $O_2$ binds to hemoglobin, making it more acidic. 2. This acidity reduces its ability to carry $CO_2$ as carbamino compounds and releases $H^+$ ions. 3. These $H^+$ ions react with bicarbonate ($HCO_3^-$) to form $H_2CO_3$, which dissociates into $CO_2$ and $H_2O$, allowing $CO_2$ to be exhaled. Essentially, **oxygenation promotes $CO_2$ unloading.** **Analysis of Incorrect Options:** * **Option A:** 2,3-BPG decreases hemoglobin's affinity for oxygen, shifting the Oxygen-Hemoglobin Dissociation Curve (ODC) to the right. * **Option C:** This describes the **Bohr Effect**, which is the inverse of the Haldane effect. It states that increased $CO_2$ (and acidity) promotes the release of $O_2$ to the tissues. * **Option D:** **Chloride Shift (Hamburger Phenomenon)** refers to the exchange of $Cl^-$ and $HCO_3^-$ across the RBC membrane to maintain electrical neutrality during $CO_2$ transport. **High-Yield Clinical Pearls for NEET-PG:** * **Haldane Effect** occurs in the **Lungs** ($CO_2$ release). * **Bohr Effect** occurs in the **Tissues** ($O_2$ release). * The Haldane effect is quantitatively more important in $CO_2$ transport than the Bohr effect is in $O_2$ transport. * **Mnemonic:** **H**aldane = **H**emoglobin (Oxygenation) affects $CO_2$. **B**ohr = **B**lood $CO_2$ affects $O_2$.

Q: At which gestational age does surfactant production in the lungs begin?

28 weeks. **Explanation:** **Correct Option: A (28 weeks)** Surfactant is a surface-active lipoprotein complex secreted by **Type II pneumocytes**. While surfactant synthesis begins as early as 20–24 weeks of gestation, it only reaches physiologically significant levels and begins to be secreted into the alveolar spaces around **28 weeks**. This timing is crucial as it marks the threshold where the fetal lungs gain the functional capacity to prevent alveolar collapse (atelectasis) upon expiration, significantly improving the chances of extrauterine survival. **Analysis of Incorrect Options:** * **B (32 weeks):** While surfactant levels continue to rise, this is an intermediate stage. It is not the "beginning" of functional production. * **C (34 weeks):** This is the clinical milestone where surfactant levels are usually sufficient to prevent **Respiratory Distress Syndrome (RDS)**. Most clinicians consider 34 weeks the "safe" zone where antenatal steroids are no longer routinely required. * **D (36 weeks):** By this time, the lungs are considered mature. The L/S ratio (Lecithin/Sphingomyelin) typically exceeds 2:1, indicating full pulmonary maturity. **High-Yield Clinical Pearls for NEET-PG:** * **Composition:** Surfactant is 90% lipids and 10% proteins. The most abundant phospholipid is **Dipalmitoylphosphatidylcholine (DPPC)** or Lecithin. * **Key Protein:** **Surfactant Protein B (SP-B)** is the most important for reducing surface tension. * **Stimulant:** **Glucocorticoids** (Cortisol) accelerate surfactant synthesis by stimulating Type II pneumocytes. This is why Betamethasone/Dexamethasone is given in preterm labor. * **Inhibitor:** **Hyperinsulinemia** (seen in infants of diabetic mothers) inhibits surfactant production, increasing the risk of RDS even in near-term babies.

Q: A 64-year-old woman presents with complaints of dyspnea and orthopnea. She is a lifelong non-smoker. Her pulmonary function testing is as follows. What is the most probable diagnosis?

Combined Obstructive - Restrictive Lung disease. ***Combined Obstructive - Restrictive Lung disease*** - **FEV1/FVC ratio < 70%** indicates obstructive pattern while **reduced TLC < 80% predicted** and **decreased FVC** suggest restrictive component. - This pattern occurs in conditions like **COPD with pulmonary fibrosis** or **bronchiectasis with scarring**, combining airway obstruction with lung volume reduction. *Mild Obstructive Lung Disease* - Would show **FEV1/FVC < 70%** with **normal or increased TLC** due to air trapping, not the reduced lung volumes seen here. - **FEV1 would be 60-80% predicted** in mild obstruction, but restrictive changes would be absent. *Moderate Obstructive Lung Disease* - Characterized by **FEV1 40-60% predicted** with **FEV1/FVC 70%)** with **reduced TLC and FVC** due to lung stiffness. - The **obstructive component (FEV1/FVC < 70%)** present in this case rules out pure restrictive disease.

Question 1

Which of the following is NOT true about COPD?

Accepted Answer

Decreased Diffusion capacity (DLco)

Answer

Reduced FEV1

Answer

Increased Residual Volume

Answer

Decreased Maximal Expiratory Flow Rate (MEFR)

Question 2

Tachycardia is caused by hypoxia due to which of the following mechanisms?

Accepted Answer

Secondarily after hyperventilation

Answer

Reflexly through peripheral chemoreceptors

Answer

Diffuse vasodilation

Answer

Through the central chemoreceptor

Question 3

Which of the following is used to measure the resistance in small airways?

Accepted Answer

Maximum mid expiratory flow rate

Answer

Vital capacity

Answer

FEV1

Answer

Closing volume

Question 4

What is the normal pulmonary capillary pressure?

Accepted Answer

10 mm Hg

Answer

5 mm Hg

Answer

20 mm Hg

Answer

32 mm Hg

Question 5

In an asthmatic patient, which of the following pulmonary functions would show the greater improvement on inhaling a bronchodilator?

Accepted Answer

FEV1

Answer

Tidal volume

Answer

FEF 25%-75%

Answer

FVC

Question 6

Select the best statement regarding the respiratory centers.

Accepted Answer

The pneumotaxic center can override the function of the inspiratory centers.

Answer

The normal rhythmic pattern of breathing originates from neurons in the dorsal respiratory group.

Answer

During quiet breathing, expiratory neurons are inhibited.

Answer

The apneustic center promotes inspiration.

Question 7

What is the Haldane effect?

Accepted Answer

Dissociation of CO2 on oxygenation

Answer

Effect of 2,3-BPG

Answer

Dissociation of O2 on addition of CO2

Answer

Chloride shift

Question 8

At which gestational age does surfactant production in the lungs begin?

Accepted Answer

28 weeks

Answer

32 weeks

Answer

34 weeks

Answer

36 weeks

Question 9

What is the characteristic of type-II respiratory failure?

Accepted Answer

Low PaO2 and high PaCO2

Answer

Low PaO2 and low PaCO2

Answer

Low PaO2 and normal PaCO2

Answer

Normal PaO2 and high PaCO2

Question 10

A 64-year-old woman presents with complaints of dyspnea and orthopnea. She is a lifelong non-smoker. Her pulmonary function testing is as follows. What is the most probable diagnosis?

Accepted Answer

Combined Obstructive - Restrictive Lung disease

Answer

Mild Obstructive Lung Disease

Answer

Moderate Obstructive Lung Disease

Answer

Restrictive Lung Disease

Respiratory System — MCQs

Respiratory System — MCQs

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