Respiratory System — MCQs

Respiratory System Indian Medical PG Practice Questions and MCQs

Question 761: What does a spirometry test primarily measure?

A. Heart rate variability
B. Lung capacity and air flow (Correct Answer)
C. Blood oxygen levels
D. Blood pressure

Explanation: ***Lung capacity and air flow*** - Spirometry measures how much air an individual can **exhale** and how quickly they can exhale it. - Key parameters include **Forced Vital Capacity (FVC)** and **Forced Expiratory Volume in 1 second (FEV1)**. - This is the **primary purpose** of spirometry testing and essential for diagnosing obstructive and restrictive lung diseases. *Heart rate variability* - This is a measure of the **variation in time** between heartbeats. - It is assessed through **ECG** or specialized heart rate monitors, not spirometry. *Blood oxygen levels* - These are typically measured using a **pulse oximeter** or by an **arterial blood gas (ABG) test**. - While spirometry provides information about lung function that can indirectly affect oxygen levels, it does **not directly measure** oxygen saturation. *Blood pressure* - Blood pressure measures the **force of blood** against artery walls. - It is measured using a **sphygmomanometer** and has no direct relationship with spirometry.

Question 762: Which of the following best describes the Bohr effect?

A. Increased CO2 binding to hemoglobin
B. Increased O2 release from hemoglobin at lower pH (Correct Answer)
C. Increased CO2 release from hemoglobin at lower pH
D. Increased O2 binding to hemoglobin at higher pH

Explanation: ***Increased O2 release from hemoglobin at lower pH*** - The **Bohr effect** describes how **hemoglobin's affinity for oxygen decreases** in the presence of increased acidity (lower pH) and higher carbon dioxide (CO2) concentrations. - This physiological adaptation ensures that **oxygen is released more readily to tissues** that are actively metabolizing and producing CO2 and lactic acid, thus lowering their local pH. *Increased CO2 binding to hemoglobin* - While CO2 does bind to hemoglobin (forming **carbaminohemoglobin**), this is known as the **Haldane effect**, which describes how **deoxygenated hemoglobin has a higher affinity for CO2** than oxygenated hemoglobin. - The Bohr effect specifically concerns the **impact of CO2 and pH on oxygen binding affinity**, not primarily CO2 binding itself. *Increased CO2 release from hemoglobin at lower pH* - Lower pH actually favors the **release of oxygen** from hemoglobin, not CO2. CO2 release from hemoglobin is more influenced by oxygenation status (Haldane effect) and the concentration gradient in the lungs. - In tissues with **lower pH**, hemoglobin's affinity for CO2 is slightly reduced as well, but the predominant effect related to oxygen is its release. *Increased O2 binding to hemoglobin at higher pH* - Higher pH (more alkaline conditions) actually **increases hemoglobin's affinity for oxygen**, promoting oxygen uptake in the lungs. - This inverse relationship is also part of the Bohr effect phenomenon, where the curve shifts to the left, but the question asks for the direct description of the Bohr effect in its most impactful context (i.e., at the tissue level).

Question 763: A 35-year-old male experiences exercise-induced asthma. Which of the following physiological changes is most likely occurring during an asthma attack?

A. Increased airway resistance (Correct Answer)
B. Decreased lung compliance
C. Increased alveolar surface tension
D. Decreased respiratory rate

Explanation: ***Increased airway resistance*** - **Bronchoconstriction**, mucus hypersecretion, and airway inflammation all contribute to a significant narrowing of the airways. - This narrowing directly impedes airflow, leading to a **higher resistance** to the movement of air during breathing. *Decreased lung compliance* - **Lung compliance** primarily relates to the stiffness of the lung tissue itself, often affected by conditions like pulmonary fibrosis. - While asthma involves airway changes, the primary issue is obstruction rather than a significant stiffening of the overall lung parenchyma. *Increased alveolar surface tension* - **Alveolar surface tension** is mainly regulated by surfactant, and an increase would typically lead to alveolar collapse, as seen in **ARDS** or premature infants. - In asthma, the main problem is in the **bronchioles** and larger airways, not the direct collapse of alveoli due to surface tension issues. *Decreased respiratory rate* - During an asthma attack, the body's natural response to difficulty breathing and hypoxemia is to **increase the respiratory rate** (tachypnea) to compensate. - A decreased respiratory rate would be a sign of impending **respiratory failure**, not an initial or common physiological change during an active exacerbation.

Question 764: In the setting of an acute asthma attack, which immediate physiological adjustment is the most effective for improving airflow?

A. Reducing cardiac output to decrease oxygen demand
B. Decreasing respiratory rate to conserve energy
C. Bronchodilation to open the airways (Correct Answer)
D. Utilizing accessory muscles to aid in respiration

Explanation: ***Bronchodilation to open the airways*** - **Bronchodilation**, typically achieved through **beta-2 agonists**, directly addresses the hallmark of asthma—**bronchoconstriction**—by relaxing the smooth muscles of the airways. - This immediate widening of the bronchial passages is the most effective way to **reduce airflow obstruction** and improve ventilation in an acute asthma attack. *Decreasing respiratory rate to conserve energy* - In an acute asthma attack, the body's natural response is to increase, not decrease, the **respiratory rate** to compensate for reduced airflow. - While conserving energy is important, reducing the respiratory rate during severe obstruction would lead to **hypoventilation** and worsened hypoxemia. *Reducing cardiac output to decrease oxygen demand* - Reducing **cardiac output** would decrease oxygen delivery to tissues, which is detrimental during an acute asthma attack where oxygen demand may be increased due to the work of breathing. - The body generally tries to maintain or increase cardiac output to compensate for **hypoxia**. *Utilizing accessory muscles to aid in respiration* - While patients *do* utilize **accessory muscles** during an acute asthma attack, this is a compensatory mechanism indicating **increased work of breathing** and respiratory distress, not an effective *physiological adjustment* for improving airflow itself. - It signifies the severity of the attack and the body's struggle to overcome airway obstruction, rather than a primary treatment.

Question 765: A patient with obstructive lung disease presents with difficulty exhaling. What is the underlying cause of this symptom?

A. Increased airway resistance (Correct Answer)
B. Decreased lung compliance
C. Reduced surfactant production
D. Decreased tidal volume

Explanation: ***Increased airway resistance*** - Obstructive lung diseases, such as **COPD** and **asthma**, are characterized by narrowing of the airways. - This narrowing leads to **increased resistance** to airflow, making exhalation difficult as air becomes trapped in the lungs. *Decreased lung compliance* - **Decreased lung compliance** is characteristic of **restrictive lung diseases**, where the lungs are stiff and difficult to inflate. - This would primarily cause difficulty with inspiration, not exhalation. *Reduced surfactant production* - **Reduced surfactant production** primarily leads to **alveolar collapse** and increased surface tension, which makes inspiration difficult and reduces functional residual capacity. - While it affects gas exchange, it is not the primary cause of difficulty exhaling in obstructive lung disease. *Decreased tidal volume* - A **decreased tidal volume** is a symptom of many respiratory issues, but it is a consequence of the underlying pathology, not the direct cause of difficulty exhaling in obstructive lung disease. - The primary problem in obstructive disease is the **impeded airflow out of the lungs**.

Question 766: Considering the physiological effects of aging on the respiratory system, which factor should be primarily evaluated to determine respiratory efficiency in the elderly?

A. Respiratory rate
B. Lung compliance (Correct Answer)
C. Airway resistance
D. Oxygen saturation

Explanation: ***Lung compliance*** - With aging, there are **complex changes in respiratory mechanics**: lung parenchymal elastic recoil decreases (making lungs more compliant) while **chest wall compliance decreases** (chest wall becomes stiffer). - The overall **respiratory system compliance** changes significantly, and evaluating lung compliance provides the most direct assessment of these fundamental mechanical alterations. - Changes in compliance directly impact the **work of breathing** and respiratory efficiency, making it the primary factor to evaluate in elderly patients. - Loss of elastic recoil also contributes to **small airway collapse** and air trapping, further affecting respiratory efficiency. *Respiratory rate* - While respiratory rate can indicate respiratory distress, it does not directly measure the **efficiency** of gas exchange or the mechanical properties of the lungs. - An elderly individual may have a normal respiratory rate but still have compromised respiratory efficiency due to underlying changes in lung mechanics. - Respiratory rate is a compensatory response rather than a primary mechanical factor. *Airway resistance* - Airway resistance can increase with age due to **small airway closure** and loss of radial traction from decreased elastic recoil. - While important, it is often a **secondary consequence** of the primary changes in elastic properties and compliance. - Changes in respiratory system compliance generally have a more pervasive and direct impact on overall respiratory mechanics in the elderly. *Oxygen saturation* - Oxygen saturation reflects the **adequacy of gas exchange**, but it is an outcome measure, not a primary indicator of the underlying mechanical changes affecting respiratory efficiency. - A patient can have acceptable oxygen saturation at rest but demonstrate poor respiratory efficiency with exertion due to altered compliance and increased work of breathing. - It does not directly assess the mechanical properties that determine respiratory efficiency.

Question 767: Which type of chemoreceptors is primarily involved in the detection of arterial blood oxygen levels?

A. Peripheral chemoreceptors (Correct Answer)
B. Central chemoreceptors
C. Baroreceptors
D. Stretch receptors

Explanation: ***Peripheral chemoreceptors*** - The **carotid bodies** and **aortic bodies** are the primary peripheral chemoreceptors responsible for monitoring arterial blood **PO2 (partial pressure of oxygen)**. - When **arterial PO2 falls below 60 mmHg**, these receptors become highly active, increasing ventilatory drive. *Central chemoreceptors* - Located in the **medulla oblongata**, these receptors are primarily sensitive to changes in the **pH of the cerebrospinal fluid (CSF)**, which reflects arterial PCO2. - They play a dominant role in regulating respiration in response to **hypercapnia (high CO2)**, not hypoxia. *Baroreceptors* - These are **mechanoreceptors** located in the **carotid sinus** and **aortic arch** that sense changes in **arterial blood pressure**. - They are involved in cardiovascular reflexes, regulating blood pressure and heart rate, but not directly oxygen levels. *Stretch receptors* - Found in the **lungs** (pulmonary stretch receptors) and **airways**, these receptors respond to the inflation and deflation of the lungs. - They are primarily involved in the **Hering-Breuer reflex**, preventing overinflation of the lungs, and do not directly detect oxygen levels.

Question 768: During spirometry, a patient exhibits a reduced FEV1/FVC ratio. What is the physiological significance of this finding in relation to obstructive lung disease?

A. Indicates decreased lung compliance
B. Suggests increased airway resistance (Correct Answer)
C. Indicates reduced total lung capacity
D. Suggests increased respiratory muscle strength

Explanation: ***Suggests increased airway resistance*** - A **reduced FEV1/FVC ratio** is the hallmark of **obstructive lung disease**, indicating that airflow out of the lungs is impaired. - This impairment is due to **increased resistance** within the airways, making it difficult to exhale air quickly and forcefully. *Indicates decreased lung compliance* - **Decreased lung compliance** is characteristic of **restrictive lung diseases**, where the lungs are stiff and difficult to inflate. - This typically results in a **normal or increased FEV1/FVC ratio** with reduced FVC, whereas obstructive diseases show a disproportionate reduction in FEV1. *Indicates reduced total lung capacity* - **Reduced total lung capacity (TLC)** is primarily associated with **restrictive lung diseases**, where lung expansion is limited. - In obstructive diseases, **TLC is often normal or even increased** due to air trapping. *Suggests increased respiratory muscle strength* - **Increased respiratory muscle strength** is not directly reflected by a reduced FEV1/FVC ratio and is generally an indicator of good respiratory function or compensatory mechanisms. - While patients with obstructive disease may exert more effort to breathe, the primary issue is **airway narrowing**, not a lack of muscle strength.

Question 769: Which physiological parameter has a direct mathematical relationship with tidal volume and increases when tidal volume increases during exercise?

A. Inspiratory reserve volume
B. Inspiratory capacity (Correct Answer)
C. Functional residual capacity
D. Residual volume

Explanation: ***Inspiratory capacity*** - **Inspiratory capacity (IC)** has a direct mathematical relationship with tidal volume: **IC = TV + IRV** (Tidal Volume + Inspiratory Reserve Volume). - Since IC is defined as the sum that includes TV, any increase in TV mathematically affects IC. During exercise, while TV increases and IRV typically decreases, IC represents the maximum volume of air that can be inspired from the resting expiratory level. - The question emphasizes the **direct mathematical relationship** (IC = TV + IRV), making IC the parameter that is mathematically linked to TV by definition. *Inspiratory reserve volume* - **Inspiratory reserve volume (IRV)** is the additional air that can be forcibly inhaled after normal tidal inspiration. - During exercise, as TV increases, IRV typically **decreases** because the increased tidal breathing utilizes part of the inspiratory reserve. This is an **inverse relationship**, not a direct one. - IRV does not increase when TV increases; instead, it is "encroached upon" by the larger tidal breaths. *Residual volume* - **Residual volume (RV)** is the air remaining in the lungs after maximal exhalation and remains relatively **constant** regardless of changes in tidal volume. - RV is not affected by voluntary breathing changes and serves to prevent alveolar collapse. - No mathematical relationship exists between RV and TV. *Functional residual capacity* - **Functional residual capacity (FRC)** equals **ERV + RV** (Expiratory Reserve Volume + Residual Volume). - FRC represents the lung volume at the end of normal expiration and actually **decreases** during exercise as breathing becomes deeper and more rapid. - FRC has no direct mathematical relationship with TV and does not increase when TV increases.

Question 770: What is the primary function of surfactant in the respiratory system?

A. Warm the air
B. Moisten the air
C. Reduce surface tension in the alveoli (Correct Answer)
D. Protect against pathogens

Explanation: ***Reduce surface tension in the alveoli*** - **Surfactant** is a complex mixture of lipids and proteins that lines the alveolar surfaces, significantly **reducing the surface tension** of the fluid within them. - This reduction in surface tension prevents the **collapse of alveoli** at the end of expiration, ensuring that lungs remain open and require less effort to inflate during inspiration. *Warm the air* - The **nasal passages** and **upper respiratory tract** primarily function to warm inhaled air before it reaches the lungs. - Surfactant's role is not involved in temperature regulation of inspired air. *Moisten the air* - The **mucous membranes** lining the nasal cavity and tracheobronchial tree are responsible for **humidifying or moistening** the inspired air. - While important for respiratory function, this is not the primary role of surfactant. *Protect against pathogens* - The **mucociliary escalator**, **macrophages**, and immunoglobulins in the respiratory tract are primarily involved in protecting against pathogens. - Although surfactant has some **immunomodulatory properties**, its main function is physical, relating to surface tension.

Practice by Chapter

Mechanics of Breathing

Practice Questions

Pulmonary Ventilation

Practice Questions

Pulmonary Circulation

Practice Questions

Gas Exchange in the Lungs

Practice Questions

Oxygen and Carbon Dioxide Transport

Practice Questions

Control of Breathing

Practice Questions

Respiratory Adjustments in Health and Disease

Practice Questions

High Altitude Physiology

Practice Questions

Diving Physiology

Practice Questions

Respiratory Function Tests

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free