Compliance

Compliance US Medical PG Question 1: A previously healthy 35-year-old woman is brought into the emergency department after being found unresponsive by her husband. Her husband finds an empty bottle of diazepam tablets in her pocket. She is stuporous. At the hospital, her blood pressure is 90/40 mm Hg, the pulse is 58/min, and the respirations are 6/min. The examination of the pupils shows normal size and reactivity to light. Deep tendon reflexes are 1+ bilaterally. Babinski sign is absent. All 4 extremities are hypotonic. The patient is intubated and taken to the critical care unit for mechanical ventilation and treatment. Regarding the prevention of pneumonia in this patient, which of the following strategies is most likely to achieve this goal?

• A. Nasogastric tube insertion
• B. Daily evaluation for ventilator weaning
• C. Subglottic drainage of secretions (Correct Answer)
• D. Oropharynx and gut antibacterial decontamination
• E. Prone positioning during mechanical ventilation

Compliance Explanation: ***Subglottic drainage of secretions*** - This is a highly effective strategy to prevent **ventilator-associated pneumonia (VAP)** by continuously removing secretions that pool above the endotracheal tube cuff before they can be aspirated. - Endotracheal tubes with a **subglottic secretion drainage port** reduce VAP incidence by preventing microaspiration of contaminated oropharyngeal secretions into the lower respiratory tract. - This is a **specific mechanical intervention** that directly addresses one of the key pathogenic mechanisms of VAP. *Nasogastric tube insertion* - While an NG tube may be needed for feeding or gastric decompression, it does not directly prevent VAP and may **increase aspiration risk** by compromising the lower esophageal sphincter. - NG tubes can promote gastroesophageal reflux and provide a conduit for bacterial migration. *Daily evaluation for ventilator weaning* - This is also a **critical component of VAP prevention** as part of the ventilator bundle, since reducing duration of mechanical ventilation is the most effective overall strategy to prevent VAP. - However, in this question asking for a strategy to prevent pneumonia in an intubated patient, subglottic drainage is the more specific technical intervention, whereas daily weaning assessment is a broader protocol that reduces exposure time. - Both strategies are important; subglottic drainage addresses the "how" of prevention during intubation, while weaning protocols address the "duration" of risk exposure. *Oropharynx and gut antibacterial decontamination* - Selective digestive decontamination (SDD) aims to reduce bacterial colonization, but evidence for routine use is mixed and raises concerns about **antimicrobial resistance**. - Not universally recommended as a primary VAP prevention strategy in most guidelines. *Prone positioning during mechanical ventilation* - **Prone positioning** is primarily indicated for improving oxygenation in **Acute Respiratory Distress Syndrome (ARDS)**, not for VAP prevention. - While it may improve secretion drainage, it is not a standard VAP prevention measure and carries its own risks and logistical challenges.

Compliance US Medical PG Question 2: A 60-year-old woman presents to the clinic with a 3-month history of shortness of breath that worsens on exertion. She also complains of chronic cough that has lasted for 10 years. Her symptoms are worsened even with light activities like climbing up a flight of stairs. She denies any weight loss, lightheadedness, or fever. Her medical history is significant for hypertension, for which she takes amlodipine daily. She has a 70-pack-year history of cigarette smoking and drinks 3–4 alcoholic beverages per week. Her blood pressure today is 128/84 mm Hg. A chest X-ray shows flattening of the diaphragm bilaterally. Physical examination is notable for coarse wheezing bilaterally. Which of the following is likely to be seen with pulmonary function testing?

• A. Decreased FEV1: FVC and decreased total lung capacity
• B. Normal FEV1: FVC and decreased total lung capacity
• C. Increased FEV1: FVC and decreased total lung capacity
• D. Decreased FEV1: FVC and increased total lung capacity (Correct Answer)
• E. Increased FEV1: FVC and normal total lung capacity

Compliance Explanation: ***Decreased FEV1:FVC ratio and increased total lung capacity*** - This patient's symptoms (shortness of breath on exertion, chronic cough, 70-pack-year smoking history, coarse wheezing, and diaphragmatic flattening on X-ray) are highly suggestive of **Chronic Obstructive Pulmonary Disease (COPD)**, specifically **emphysema**, an obstructive lung disease. - In COPD, there is airflow limitation, causing a **decreased FEV1:FVC ratio** (typically <0.70). Over time, air trapping occurs due to damaged alveoli and loss of elastic recoil, leading to an **increased total lung capacity (TLC)** and residual volume. *Decreased FEV1:FVC ratio and decreased total lung capacity* - A **decreased FEV1:FVC ratio** indicates an **obstructive lung disease**. - However, a **decreased total lung capacity (TLC)** is characteristic of a **restrictive lung disease**, which does not align with the patient's presentation typical of COPD/emphysema. *Normal FEV1:FVC ratio and decreased total lung capacity* - A **normal FEV1:FVC ratio** is inconsistent with the patient's strong history of smoking and symptoms suggestive of airflow obstruction. - A **decreased total lung capacity (TLC)** indicates a restrictive lung disease, which is not the primary diagnosis here. *Increased FEV1:FVC ratio and decreased total lung capacity* - An **increased FEV1:FVC ratio** is not physiologically possible in significant lung disease and is therefore incorrect. - A **decreased total lung capacity (TLC)** would point towards a restrictive pattern not seen in generalized emphysema. *Increased FEV1:FVC ratio and normal total lung capacity* - An **increased FEV1:FVC ratio** is not a characteristic finding in any lung disease and is therefore incorrect. - A **normal total lung capacity** would not be expected in advanced emphysema where air trapping is prominent.

Compliance US Medical PG Question 3: A previously healthy 64-year-old woman comes to the physician because of a dry cough and progressively worsening shortness of breath for the past 2 months. She has not had fever, chills, or night sweats. She has smoked one pack of cigarettes daily for the past 45 years. She appears thin. Examination of the lung shows a prolonged expiratory phase and end-expiratory wheezing. Spirometry shows decreased FEV1:FVC ratio (< 70% predicted), decreased FEV1, and a total lung capacity of 125% of predicted. The diffusion capacity of the lung (DLCO) is decreased. Which of the following is the most likely diagnosis?

• A. Bronchiectasis
• B. Interstitial lung disease
• C. Chronic obstructive pulmonary disease (Correct Answer)
• D. Hypersensitivity pneumonitis
• E. Bronchial asthma

Compliance Explanation: ***Chronic obstructive pulmonary disease*** - The patient's long history of **smoking (45 pack-years)**, **prolonged expiratory phase**, and **end-expiratory wheezing** are classic signs of airway obstruction. - Spirometry findings of a **decreased FEV1:FVC ratio** (< 70% predicted), **decreased FEV1**, **increased total lung capacity (TLC)**, and **decreased DLCO** are all highly indicative of **emphysema**, a subtype of COPD. *Bronchiectasis* - While it shares symptoms like cough and SOB, **bronchiectasis** is characterized by permanent **dilatation of bronchi** and profuse, chronic **sputum production**, which is not mentioned here. - Spirometry typically shows **obstructive patterns**, but the marked increase in TLC and decreased DLCO are more specific to emphysema. *Interstitial lung disease* - This condition primarily causes a **restrictive lung pattern**, meaning a decreased TLC and normal or increased FEV1:FVC ratio. - The patient's **increased TLC** and **obstructive spirometry** rule out a purely restrictive process. *Hypersensitivity pneumonitis* - This is an inflammatory response to inhaled antigens, often presenting with **recurrent episodes** of fever, chills, and cough, and can lead to restrictive physiology. - The patient lacks a history of specific **antigen exposure** and presents with an obstructive pattern and increased TLC. *Bronchial asthma* - While asthma shares obstructive features like wheezing and a decreased FEV1:FVC ratio, it is characterized by **reversibility** of airway obstruction and typically does not cause a significantly **elevated TLC** or **decreased DLCO** in uncomplicated cases. - The patient's long smoking history points away from asthma as the primary diagnosis.

Compliance US Medical PG Question 4: A 25-year-old previously healthy woman is admitted to the hospital with progressively worsening shortness of breath. She reports a mild fever. Her vital signs at the admission are as follows: blood pressure 100/70 mm Hg, heart rate 111/min, respiratory rate 20/min, and temperature 38.1℃ (100.6℉); blood saturation on room air is 90%. Examination reveals a bilateral decrease of vesicular breath sounds and rales in the lower lobes. Plain chest radiograph demonstrates bilateral opacification of the lower lobes. Despite appropriate treatment, her respiratory status worsens. The patient is transferred to the intensive care unit and put on mechanical ventilation. Adjustment of which of the following ventilator settings will only affect the patient’s oxygenation?

• A. Tidal volume and respiratory rate
• B. FiO2 and PEEP (Correct Answer)
• C. Respiratory rate and PEEP
• D. Tidal volume and FiO2
• E. FiO2 and respiratory rate

Compliance Explanation: ***FiO2 and PEEP*** - **FiO2 (fraction of inspired oxygen)** directly controls the oxygen concentration delivered to the patient, thus solely impacting **oxygenation**. - **PEEP (positive end-expiratory pressure)** prevents alveolar collapse and recruits collapsed alveoli, improving the **functional residual capacity** and thus **oxygenation** without significantly altering CO2 removal (ventilation). *Tidal volume and respiratory rate* - **Tidal volume (Vt)** directly impacts the amount of air moved with each breath, primarily affecting **ventilation** (CO2 removal). - **Respiratory rate (RR)** also directly determines the total minute ventilation, thus influencing **ventilation** more than oxygenation. *Respiratory rate and PEEP* - As mentioned, **respiratory rate** significantly affects **ventilation** by altering minute ventilation (Vt x RR). - While **PEEP** primarily affects oxygenation, the combination with respiratory rate means it's not exclusively targeting oxygenation. *Tidal volume and FiO2* - **Tidal volume** is a key determinant of **ventilation** (CO2 removal), not solely oxygenation. - **FiO2** does affect oxygenation, but its combination with tidal volume makes this option incorrect for *only* affecting oxygenation. *FiO2 and respiratory rate* - **FiO2** directly impacts **oxygenation**. - **Respiratory rate** primarily affects **ventilation** (CO2 removal), thereby influencing carbonic acid levels and pH.

Compliance US Medical PG Question 5: A 57-year-old man comes to the physician because of a 2-year history of fatigue, worsening shortness of breath, and a productive cough for 2 years. He has smoked 1 pack of cigarettes daily for the past 40 years. Examination shows pursed-lip breathing and an increased anteroposterior chest diameter. There is diffuse wheezing bilaterally and breath sounds are distant. Which of the following parameters is most likely to be decreased in this patient?

• A. Thickness of small airways
• B. Work of breathing
• C. Lung elastic recoil (Correct Answer)
• D. Lower airway resistance
• E. Pulmonary vascular pressure

Compliance Explanation: ***Lung elastic recoil*** - The patient's presentation (long smoking history, dyspnea, pursed-lip breathing, increased AP diameter, distant breath sounds, and wheezing) is classic for **emphysema**, a form of **COPD**. - Emphysema involves the destruction of **alveolar walls** and **elastic fibers**, leading to a significant decrease in the lung's ability to passively recoil during expiration. *Thickness of small airways* - In COPD, particularly chronic bronchitis, there is often **inflammation and thickening of the small airways** due to goblet cell hyperplasia and mucus gland hypertrophy, increasing their thickness, not decreasing it. - This thickening contributes to increased airway resistance. *Work of breathing* - The **destruction of elastic recoil** in emphysema means the patient must actively use accessory muscles to exhale, significantly **increasing the work of breathing**, which is evident from pursed-lip breathing. - Patients with COPD expend much more energy to breathe than healthy individuals. *Lower airway resistance* - Emphysema, while characterized by alveolar destruction, also has an obstructive component due to **airway collapse during expiration** (loss of radial traction) and potential inflammation/mucus, which leads to **increased lower airway resistance**, not decreased resistance. - This increased resistance contributes to air trapping and wheezing. *Pulmonary vascular pressure* - Chronic hypoxia resulting from severe COPD can lead to **pulmonary vasoconstriction** and remodeling of the pulmonary arteries, causing **pulmonary hypertension** and an increase in pulmonary vascular pressure. - This is a common complication in advanced COPD, not a decreased parameter.

Compliance US Medical PG Question 6: A 14-year-old male presents to the emergency department with altered mental status. His friends who accompanied him said that he complained of abdominal pain while camping. They denied his consumption of anything unusual from the wilderness, or any vomiting or diarrhea. His temperature is 100.5°F (38.1°C), blood pressure is 95/55 mmHg, pulse is 130/min, and respirations are 30/min. His pupils are equal and reactive to light bilaterally. The remainder of the physical exam is unremarkable. His basic metabolic panel is displayed below: Serum: Na+: 116 mEq/L Cl-: 70 mEq/L K+: 4.0 mEq/L HCO3-: 2 mEq/L BUN: 50 mg/dL Glucose: 1010 mg/dL Creatinine: 1.2 mg/dL While the remainder of his labs are pending, the patient becomes bradypneic and is intubated. His ventilator is adjusted to volume control assist-control with a respiratory rate (RR) of 14/min, tidal volume (Vt) of 350 mL, positive end-expiratory pressure (PEEP) of 5 cm H2O, and fractional inspired oxygen (FiO2) of 40%. His height is 5 feet 5 inches. Intravenous fluids and additional medical therapy are administered. An arterial blood gas obtained after 30 minutes on these settings shows the following: pH: 7.05 pCO2 :40 mmHg pO2: 150 mmHg SaO2: 98% What is the best next step in management?

• A. Increase respiratory rate
• B. Increase respiratory rate and tidal volume (Correct Answer)
• C. Increase tidal volume
• D. Increase tidal volume and positive end-expiratory pressure
• E. Increase positive end-expiratory pressure

Compliance Explanation: ***Increase respiratory rate and tidal volume*** - The patient presents with **severe metabolic acidosis** (pH 7.05, HCO3- 2 mEq/L) due to likely **diabetic ketoacidosis** given the hyperglycemia and altered mental status. - To compensate for metabolic acidosis, the body attempts to lower pCO2 through **hyperventilation**; therefore, increasing both the **respiratory rate** and **tidal volume** will increase minute ventilation and help "blow off" CO2, thus improving the pH. *Increase respiratory rate* - While increasing the respiratory rate will help decrease pCO2 and improve pH, it may not be sufficient on its own to correct the severe acidosis. - **Tidal volume** also plays a crucial role in minute ventilation and CO2 elimination; addressing both components is more effective. *Increase tidal volume* - Increasing tidal volume alone will also increase minute ventilation and help reduce pCO2. - However, combining it with an increased respiratory rate is more effective for severe acidosis, as both parameters contribute to **CO2 clearance**. *Increase tidal volume and positive end-expiratory pressure* - Increasing tidal volume helps reduce pCO2, but increasing PEEP primarily improves **oxygenation** by preventing alveolar collapse and increasing functional residual capacity. - The patient's pO2 is already high (150 mmHg) with 98% SaO2, so **oxygenation is not the primary concern**; the focus should be on correcting the acidosis by reducing pCO2. *Increase positive end-expiratory pressure* - As mentioned, PEEP is primarily used to improve **oxygenation** and manage conditions like acute respiratory distress syndrome (ARDS), which is not the immediate problem here. - The patient's **pO2 is adequate**, and PEEP will not directly address the **severe metabolic acidosis** or aid significantly in CO2 removal.

Compliance US Medical PG Question 7: A 22-year-old woman presents to the emergency department with a chief concern of shortness of breath. She was hiking when she suddenly felt unable to breathe and had to take slow deep breaths to improve her symptoms. The patient is a Swedish foreign exchange student and does not speak any English. Her past medical history and current medications are unknown. Her temperature is 99.5°F (37.5°C), blood pressure is 127/68 mmHg, pulse is 120/min, respirations are 22/min, and oxygen saturation is 90% on room air. Physical exam is notable for poor air movement bilaterally and tachycardia. The patient is started on treatment. Which of the following best describes this patient's underlying pathology? FEV1 = Forced expiratory volume in 1 second FVC = Forced vital capacity DLCO = Diffusing capacity of carbon monoxide

• A. Increased FVC
• B. Increased FEV1
• C. Increased FEV1/FVC
• D. Decreased airway tone
• E. Normal DLCO (Correct Answer)

Compliance Explanation: ***Normal DLCO*** - This patient presents with an acute exacerbation of what is likely **asthma**, showing symptoms of **shortness of breath**, **tachycardia**, poor air movement bilaterally, and improvement with slow deep breaths. **Asthma** characteristically affects the airways and not the alveoli, thus the **diffusing capacity of carbon monoxide (DLCO)**, which measures gas exchange across the alveolar-capillary membrane, would be expected to be normal. - In asthma, the primary problem is **bronchoconstriction** and **airway inflammation**, which restricts airflow but does not typically impair the diffusion of gases like carbon monoxide across the alveolar-capillary membrane. *Increased FVC* - **Forced vital capacity (FVC)** is often normal or even slightly reduced in asthma due to **air trapping** and early airway closure, not increased. - An increased FVC is usually not associated with obstructive lung diseases like asthma but could potentially be seen in conditions where lung volumes are pathologically large, which is not the case here. *Increased FEV1* - **Forced expiratory volume in 1 second (FEV1)** is typically **decreased** in obstructive lung diseases like asthma due to **airflow limitation**. - An increased FEV1 would indicate better-than-average expiratory flow, which contradicts the symptoms of shortness of breath and poor air movement in this patient. *Increased FEV1/FVC* - The **FEV1/FVC ratio** is characteristically **decreased** in obstructive lung diseases like asthma, indicating that a disproportionately smaller amount of air can be exhaled in the first second relative to the total forced vital capacity. - An increased FEV1/FVC ratio would be a sign of a restrictive lung disease or normal lung function, not an exacerbation of an obstructive process. *Decreased airway tone* - The underlying pathology in asthma is typically **bronchoconstriction**, which means an **increased airway tone** and narrowing of the airways, rather than decreased. - Decreased airway tone would imply bronchodilation, which would alleviate, not cause, the patient's symptoms of shortness of breath and poor air movement.

Compliance US Medical PG Question 8: A 60-year-old man presents with breathlessness for the past 3 months. His symptoms have been getting progressively worse during this time. He denies any history of cough, fever, or chest pain. He works at a local shipyard and is responsible for installing the plumbing aboard the vessels. His past medical history is significant for hypertension for which he takes metoprolol every day. He denies smoking and any illicit drug use. His pulse is 74/min, respiratory rate is 14/min, blood pressure is 130/76 mm Hg, and temperature is 36.8°C (98.2°F). Physical examination is significant for fine bibasilar crackles at the end of inspiration without digital clubbing. Which of the following additional findings would most likely be present in this patient?

• A. Increased pulmonary capillary wedge pressure
• B. Increased residual lung volume
• C. Reduced FEV1/FVC ratio
• D. Decreased diffusing capacity of CO (Correct Answer)
• E. Decreased pulmonary arterial pressure

Compliance Explanation: ***Decreased diffusing capacity of CO*** - This patient's occupation at a **shipyard**, progressive dyspnea, and bibasilar crackles without clubbing, along with normal vital signs, are highly suggestive of **asbestosis**, a type of **interstitial lung disease (ILD)**. - ILDs cause **fibrosis of the alveolar-capillary membrane**, leading to impaired gas exchange and a characteristic **reduction in DLCO (diffusing capacity of the lung for carbon monoxide)**. This is a hallmark of parenchymal lung disease. *Increased pulmonary capillary wedge pressure* - An elevated **pulmonary capillary wedge pressure (PCWP)** indicates **left-sided heart failure** or **pulmonary venous hypertension**. - While dyspnea can be a symptom of heart failure, the patient's normal blood pressure and absence of cardiac-specific symptoms or signs point away from primary cardiac pathology. *Increased residual lung volume* - **Increased residual lung volume** is a characteristic finding in **obstructive lung diseases** such as **COPD** and **asthma**, where there is air trapping due to airflow limitation. - The patient's presentation with progressive dyspnea and bibasilar crackles is more consistent with a **restrictive lung disorder** like asbestosis, which typically causes **decreased lung volumes**. *Reduced FEV1/FVC ratio* - A **reduced FEV1/FVC ratio** is the hallmark of **obstructive lung diseases**, indicating airflow limitation. - In **restrictive lung diseases** like asbestosis, both FEV1 and FVC are typically reduced proportionally, often resulting in a **normal or even increased FEV1/FVC ratio**. *Decreased pulmonary arterial pressure* - **Pulmonary arterial pressure (PAP)** is typically **normal or increased** in patients with interstitial lung disease due to **hypoxic vasoconstriction** and vascular remodeling. - A decreased PAP would be an unusual and atypical finding in such a patient and is not associated with this clinical picture.

Compliance US Medical PG Question 9: A 21-year-old man is admitted to the intensive care unit for respiratory failure requiring mechanical ventilation. His minute ventilation is calculated to be 7.0 L/min, and his alveolar ventilation is calculated to be 5.1 L/min. Which of the following is most likely to decrease the difference between minute ventilation and alveolar ventilation?

• A. Increasing the partial pressure of inhaled oxygen
• B. Decreasing the affinity of hemoglobin for oxygen
• C. Increasing the respiratory depth
• D. Decreasing the physiologic dead space (Correct Answer)
• E. Increasing the respiratory rate

Compliance Explanation: ***Decreasing the physiologic dead space*** - The difference between **minute ventilation (VE)** and **alveolar ventilation (VA)** is the **dead space ventilation (VD)**, calculated as: VE - VA = VD - In this case: 7.0 L/min - 5.1 L/min = 1.9 L/min of dead space ventilation - Decreasing the **physiologic dead space** directly reduces this difference by allowing a greater proportion of each breath to participate in gas exchange - This is the most direct way to narrow the gap between VE and VA *Increasing the partial pressure of inhaled oxygen* - This intervention primarily affects **oxygenation** by increasing the driving pressure for oxygen diffusion into the blood - It does not directly change the volume of air participating in alveolar ventilation or reduce dead space ventilation - The distribution of ventilation between alveolar and dead space remains unchanged *Decreasing the affinity of hemoglobin for oxygen* - A decrease in hemoglobin affinity for oxygen facilitates **oxygen unloading** to the tissues (rightward shift of the oxygen-hemoglobin dissociation curve) - This effect is related to **oxygen delivery** and does not alter the proportion of minute ventilation that reaches the alveoli for gas exchange - Dead space ventilation remains unchanged *Increasing the respiratory depth* - Increasing respiratory depth increases **tidal volume (VT)**, which improves the **ratio** of alveolar ventilation to minute ventilation (VA/VE efficiency) - However, the **absolute difference** (VE - VA) in L/min depends on the **total dead space volume**, which is not changed by increasing tidal volume alone - While this improves ventilation efficiency, it does not directly reduce the dead space ventilation measured in L/min unless physiologic dead space itself decreases *Increasing the respiratory rate* - While increasing respiratory rate increases **minute ventilation (VE)**, it also increases the frequency of ventilating the **dead space** with each breath - Since dead space ventilation (VD) = respiratory rate × dead space volume, increasing rate while keeping tidal volume constant will proportionally increase both VE and VD - This can actually widen the absolute gap between VE and VA, making it less efficient

Compliance US Medical PG Question 10: A 30-year-old woman presents to the emergency department with breathlessness for the last hour. She is unable to provide any history due to her dyspnea. Her vitals include: respiratory rate 20/min, pulse 100/min, and blood pressure 144/84 mm Hg. On physical examination, she is visibly obese, and her breathing is labored. There are decreased breath sounds and hyperresonance to percussion across all lung fields bilaterally. An arterial blood gas is drawn, and the patient is placed on inhaled oxygen. Laboratory findings reveal: pH 7.34 pO2 63 mm Hg pCO2 50 mm Hg HCO3 22 mEq/L Her alveolar partial pressure of oxygen is 70 mm Hg. Which of the following is the most likely etiology of this patient’s symptoms?

• A. Right to left shunt
• B. Alveolar hypoventilation (Correct Answer)
• C. Ventricular septal defect
• D. Impaired gas diffusion
• E. Ventilation/perfusion mismatch

Compliance Explanation: ***Alveolar hypoventilation*** - The patient exhibits features of **obesity** and **labored breathing** with decreased breath sounds and hyperresonance, along with arterial blood gas results showing **respiratory acidosis** (pH 7.34, pCO2 50 mmHg) and **hypoxia** (pO2 63 mmHg). - The calculated A-a gradient (Alveolar O2 - arterial O2) is low (70 mmHg - 63 mmHg = 7 mmHg), indicating that the problem is primarily with **overall ventilation** rather than a defect in gas exchange across the alveolar-capillary membrane. *Right to left shunt* - A right-to-left shunt would cause a **large A-a gradient**, as deoxygenated blood bypasses the lungs and mixes with oxygenated blood. - While it causes **hypoxemia**, it would not typically be associated with hypercapnia unless very severe, and the A-a gradient calculation here does not support a significant shunt. *Ventricular septal defect* - A ventricular septal defect is a **structural heart abnormality** that can cause a left-to-right shunt initially, leading to pulmonary hypertension and eventually a right-to-left shunt (Eisenmenger syndrome). - While it can cause hypoxemia due to shunting, it would not primarily manifest with increased pCO2 or the specific lung physical exam findings of decreased breath sounds and hyperresonance in the absence of other cardiac signs. *Impaired gas diffusion* - Impaired gas diffusion would lead to a **large A-a gradient** and **hypoxemia**, but typically not significant hypercapnia unless the impairment is extremely severe. - Conditions like **pulmonary fibrosis** or **emphysema** cause impaired diffusion, but the patient's presentation and particularly the low A-a gradient do not support this. *Ventilation/perfusion mismatch* - A V/Q mismatch also causes a **large A-a gradient** and **hypoxemia**, as some areas of the lung are either poorly ventilated or poorly perfused. - While it can cause hypercapnia in severe cases, the primary issue indicated by the low A-a gradient here is one of overall inadequate ventilation, not selective areas of ventilation-perfusion imbalance.

Compliance Flashcard 1 of 10

Question: What is the effect of pulmonary fibrosis on lung compliance?_____

Answer: Decreased compliance

Compliance Flashcard 2 of 10

Question: The compliance of the lungs and chest wall is _____ proportional to their elastance

Answer: inversely

Compliance Flashcard 3 of 10

Question: A lung with _____ compliance is harder to fill

Answer: low

Compliance Flashcard 4 of 10

Question: Lung compliance may be calculated by the equation C = _____

Answer: V/P

Compliance Flashcard 5 of 10

Question: The compliance of the lung-chest wall system is _____ than that of the lungs or chest wall alone

Answer: less

Compliance Flashcard 6 of 10

Question: What is the function of elastin?

Answer: give stretchy property to different tissues

Compliance Flashcard 7 of 10

Question: Lung compliance may be calculated by the equation C = _____

Answer: ΔV/ΔP

Extra Information: Watch associated Bootcamp video [https://app.bootcamp.com/med-school/pulmonology/videos/air?index=16] https://onlinemeded.org?ref=anki 

Compliance Flashcard 8 of 10

Question: To compensate for reduced lung compliance, obese patients have _____-_____ breathing

Answer: rapid

Extra Information:  Watch Restrictive Lung Disease (Overview) [https://dashboard.sketchy.com/study/medical/courses/medical-pathophysiology/units/medical-pathophysiology-pulmonary/videos/medical-pathophysiology-pulmonary-restrictive-lung-disease-restrictive-lung-disease-overview?utm_source=anki&utm_medium=partnership&utm_campaign=february_update&utm_content=medical]Watch associated Bootcamp video [https://app.bootcamp.com/med-school/pulmonology/videos/air?index=16] https://onlinemeded.org/spa/pulmonary/restrictive-lung-disease/acquire?ref=anki 

Compliance Flashcard 9 of 10

Question: During expiration, the slope of the pressure-volume loop _____ as the density of surfactant molecules rapidly _____

Answer: increases

Extra Information:  Watch associated Bootcamp video [https://app.bootcamp.com/med-school/pulmonology/videos/air?index=14] https://onlinemeded.org?ref=anki 

Compliance Flashcard 10 of 10

Question: What is the effect of emphysema on lung compliance? _____

Answer: Increased compliance

Extra Information:   Watch COPD & Emphysema [https://dashboard.sketchy.com/study/medical/courses/medical-pathophysiology/units/medical-pathophysiology-pulmonary/videos/medical-pathophysiology-pulmonary-obstructive-lung-disease-copd-and-emphysema?utm_source=anki&utm_medium=partnership&utm_campaign=february_update&utm_content=medical]Watch associated Bootcamp video [https://app.bootcamp.com/med-school/pulmonology/videos/air?index=16] https://onlinemeded.org/spa/pulmonary/obstructive-lung-disease/acquire?ref=anki