Respiratory

Question 1

What conditions should be included in the differential diagnosis? If protein-rich exudate is found in the alveoli, what diagnosis is likely and to what condition could it lead?

Answer 1

Given this patient’s history, the differential diagnosis should include noncardiogenic pulmonary edema, acute pneumonitis, and acute respiratory distress syndrome. Onset of symptoms may take up to several days depending on the severity of the insult.
Protein-rich exudate in the alveoli suggests diffuse alveolar damage, which may lead to acute respiratory distress syndrome (ARDS). ARDS is a severe and potentially fatal lung disease in which acute inflammation and progressive parenchymal injury leads to hypoxemia. Typical histological presentation (Figure 14-1) involves diffuse alveolar damage and hyaline membrane formation in the alveolar walls.

Question 2

What are the mechanisms of acute respiratory distress syndrome (ARDS)?

Answer 2

Diffuse alveolar damage involves an increase in alveolar capillary permeability because of the damage caused by an inciting agent; in this case, the inciting agent is the corrosive gas and the body’s response to it. Initial damage is due to neutrophilic substances that are toxic to tissue, oxygen-derived free radicals, and activation of the coagulation cascade. This insult leads to protein-rich exudates leaking into the lungs and the formation of an intra-alveolar hyaline membrane.

Question 3

If ARDS does not resolve, what complication can arise?

Answer 3

If the inflammation and hyaline membrane formation do not resolve, the damaged tissue can organize, resulting in fibrosis.

Question 4

How is Noncardiogenic pulmonary edema characterised?
How is Acute interstitial pneumonitis characterised?

Answer 4

Noncardiogenic pulmonary edema is pulmonary edema caused by injury to the lung parenchyma (such as pulmonary contusion, aspiration, or inhalation of toxic gas).
Acute interstitial pneumonitis is a severe lung disease that begins abruptly with cough, fever, and difficulty breathing and progresses to respiratory failure within days to weeks.

Question 5

What is the most appropriate treatment for ARDS?

Answer 5

Oxygenation is a cornerstone of treatment and usually involves some form of mechanical ventilation in the intensive care unit. Whenever ARDS develops, the underlying cause must be treated, and patients may also need medication to treat infection, reduce inflammation, and remove fluid from the lungs.

Question 6

What is the most likely diagnosis?
What other conditions should be considered in the differential diagnosis?

Answer 6

Asbestosis

Question 7

What is the pathophysiology of Asbestosis?

Answer 7

The pathophysiologic process of asbestosis involves diffuse pulmonary interstitial fibrosis caused by inhaled asbestos fibers. Asbestos fibers penetrate bronchioles and lung tissue, where they are surrounded by macrophages and coated by a protein-iron complex (ferruginous bodies); Figure 14-2 shows these phagocytosed bodies. Diffuse fibrosis around the bronchioles spreads to the alveoli, causing lung tissue to become rigid and airways distorted.

Question 8

What are the most likely chest x-ray findings in Asbestosis?

Answer 8

In cases of minor exposure, the only findings may be pleural thickening or calcified pleural plaques. In cases of extensive pulmonary fibrosis, reticular or nodular opacities will be seen throughout the lung fields, most prominently at the bases.

Question 9

What is the most likely diagnosis?

Answer 9

Asthma exacerbation. Asthma is a form of obstructive lung disease.

Question 10

What are other obstructive lung diseases other than asthma, and how do they differ from asthma? (3)

Answer 10

Question 11

What is the pathophysiology of Asthma?

Answer 11

Acutely, bronchial hyperresponsiveness leads to episodic, reversible bronchoconstriction. Specifically, smooth muscle contraction in the airways leads to expiratory airflow obstruction. Chronically, airway inflammation leads to histologic changes in the bronchial tree.

Question 12

What histologic findings in the lung are associated with Asthma?

Answer 12

Histologic examination reveals smooth muscle hypertrophy, goblet cell hyperplasia, thickening of basement membranes, and increased eosinophil recruitment (in Figure 14-3 the arrow points to plate of cartilage, and the arrowhead points to infiltrate of inflammatory cells). Dilated bronchi are filled with neutrophils and may have mucous plugs.

Question 13

What are common triggers of Asthma?

Answer 13

Triggers of asthma exacerbation include stress, cold, exercise, dust and animal dander, mold, and viral upper respiratory tract infections.

Question 14

What is the appropriate treatment for asthma?

Answer 14

For acute episodes, albuterol, a β2-agonist, helps relax bronchial smooth muscle and decrease airway obstruction. However, for long-term control of persistent symptoms, inhaled corticosteroids are the best treatment.

Question 15

What drug was most likely given to this baby to promote lung expansion?
What is the most likely diagnosis?

Answer 15

Surfactant, normally produced late in fetal life (around week 28), can be given to the baby directly. Surfactant lowers the surface tension between alveoli, helping the lung to expand. Dexamethasone can be used antenatally to aid in surfactant production; it is given to women at risk for preterm delivery to reduce the risk of respiratory distress syndrome.

Question 16

What are the 5 primary types of atelectasis?

Answer 16

Question 17

How does obstructive atelectasis differ from compressive atelectasis?

Answer 17

In obstructive atelectasis, the mediastinum shifts toward the atelectasis due to loss of lung volume in that area. By contrast, the mediastinum shifts away from the atelectasis with compression.

Question 18

During atelectasis, to what is the patient commonly predisposed?

Answer 18

Atelectasis results in mucus trapping and a decrease in ventilation, thereby predisposing the patient to
infections.

Question 19

What is the most likely diagnosis?

Answer 19

Bronchiectasis.

Question 20

What radiologic findings can help diagnose Bronchiectasis?

Answer 20

In bronchiectasis, a “tree-in-bud” pattern is commonly seen on high-resolution CT scans. This represents the plugging of small airways with mucus and bronchiolar wall thickening.

Question 21

What are the possible etiologies of bronchiectasis?

Answer 21

Etiologies include chronic bronchial necrotizing infections, cystic fibrosis, bronchial obstruction from granulomatous disease or neoplasms, α1-antitrypsin deficiency, impaired host defense (eg, AIDS), and airway inflammation (eg, bronchiolitis obliterans). Additionally, tuberculosis and primary ciliary dyskinesia should be evaluated.

Question 22

What complications are associated with bronchiectasis? (5)

Answer 22

Complications of bronchiectasis include hemoptysis, hypoxemia, cor pulmonale, dyspnea, and amyloidosis.

Question 23

What is the appropriate treatment for bronchiectasis?

Answer 23

If an infection is thought to be the cause, then antibiotics should be given. If the bronchiectasis is localized, surgery may be an option. For routine management, however, measures include postural drainage and chest percussion.

Question 24

What is the most likely diagnosis?

Answer 24

The history of productive cough for at least 3 consecutive months over 2 consecutive years accompanied by emphysema (suggested by pursed-lip breathing) indicates chronic obstructive pulmonary disease (COPD) with features of chronic bronchitis.

Question 25

What radiologic findings can help diagnose chronic bronchitis?

Answer 25

In patients with COPD, x-rays of the chest often reveal lung hyperinflation, flattening of the diaphragm, and decreased peripheral vascular markings.

Question 26

What abnormalities would be expected on pulmonary function testing in patients with chronic bronchitis?

Answer 26

Question 27

How would chronic bronchitis affect the patient’s arterial blood gas levels (pH, PaO2, PaCO2, and SaO2)?

Answer 27

The pH decreases as a result of respiratory acidosis. Although pH may be normal in a patient with chronic compensated COPD, it is low in a patient with an acute exacerbation. Arterial oxygen tension (PaO2) decreases, arterial carbon dioxide tension (PaCO2) increases, and oxygen saturation (SaO2) decreases secondary to impaired gas exchange (from destruction of alveolar septae and pulmonary capillary bed).

Question 28

Why is breathing with pursed lips adaptive in COPD/chronic bronchitis?

Answer 28

Breathing with pursed lips maintains positive end-expiratory pressure (PEEP). PEEP prevents alveolar and small airway collapse, which is common in emphysema. Respiratory therapy often provides supplemental oxygen via a mask or nasal prongs. Positive airway pressure can be provided by continuous positive airway pressure, bilevel positive airway pressure, or intubation and ventilatory support.

Question 29

What complication of chronic bronchitis is suggested by the patient’s enlarged neck veins, hepatomegaly, and edema?

Answer 29

Cor pulmonale. Right heart failure due to chronic pulmonary hypertension leads to systemic venous congestion, which presents with the symptoms mentioned here. This complication occurs only in patients with severe COPD who develop pulmonary hypertension.

Question 30

What is the most likely diagnosis? What are the likely lung examination findings?

Answer 30

This patient presents with several classic findings of community-acquired pneumonia (CAP): a productive cough, fever, rigors (shaking chills), and tachypnea. His risk factors include an advanced age and a significant smoking history. Exam findings: Decreased breath sounds, crackles, dullness to percussion, and increased tactile fremitus are probable findings and can indicate areas of consolidation (ie, areas filled with fluid).

Question 31

What are the most likely causative organisms of CAP?

Answer 31

Question 32

Gram stain of the sputum in a patient with suspected CAP reveals gram-positive cocci in pairs and short chains. Additional testing reveals that the organism is optochin sensitive and the Quellung reaction is positive. What is the causative organism?

Answer 32

S pneumoniae is a gram-positive, encapsulated organism, hence the positive Quellung reaction, which is performed by adding anticapsular antisera that cause the capsule to swell. The organism is also catalase negative, α-hemolytic (partial hemolysis; the blood turns greenish), and optochin sensitive (which differentiates it from Streptococcus viridans, which is also α-hemolytic).

Question 33

What are the appropriate treatments for S pneumoniae CAP?

Answer 33

Penicillin V and amoxicillin are rarely used in clinical practice because resistance with these drugs is an increasing problem. The typical treatment is either a macrolide in combination with a cephalosporin or fluoroquinolone monotherapy.

Question 34

What factors would indicate hospitalization for a patient with community acquired pneumonia?

Answer 34

Factors that increase the need for hospitalization include age older than 65 years, altered mental status, underlying chronic illness, elevated blood pressure, elevated temperature, and abnormally high kidney function tests (ie, creatinine and blood urea nitrogen).

Question 35

How many segments of lung will be resected if the entire right lower lobe is removed?

Answer 35

There are five segments in the right lower lobe (Figure 14-8): Medial, Anterior, Lateral, Posterior, and Superior (mnemonic: MALPS).

Question 36

Which vessels supply arterial and venous branches to the lungs, and what paths do the branches follow to supply each lung segment?

Answer 36

The lung alveoli are supplied by branches of the pulmonary artery and vein. The bronchial tree also receives its arterial supply from the bronchial arteries (from the aorta) and venous drainage from bronchial veins that feed into the azygos and accessory hemiazygos veins. Pulmonary and bronchial arteries follow the airways into the periphery. Pulmonary veins course in the septa between adjacent lung segments.

Question 37

When entering the thoracic cavity through an intercostal space, the surgeon preserves the intercostal nerves and vessels. What is the anatomic relationship between the intercostal nerves and vessels and the ribs?

Answer 37

The intercostal nerves and vessels lie in the costal groove inferior to each rib. They are positioned between the innermost intercostal and internal intercostal muscles for the length of those muscles.

Question 38

During development, the pulmonary arteries arise from which aortic arch?

Answer 38

The sixth aortic arch produces the pulmonary arteries as well as to the ductus arteriosus.

Question 39

During which week of gestation are the bronchial buds formed from the foregut?

Answer 39

Bronchial buds are formed in the fourth week of gestation. Depending on the histology and other associated anomalies, different types of CCAMs are suspected to result from insults at varying stages of development. For example, type 2 CCAMs are associated with anomalies such as esophageal fistulas and bilateral renal agenesis. Thus, type 2 CCAMs are thought to arise early in organogenesis, during the fourth week of gestation.

Question 40

What genetically transmitted condition does this patient likely have?

Answer 40

The patient likely has cystic fibrosis (CF), which is caused by loss-of-function mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) protein, a chloride channel found in all exocrine tissues. As a result of these mutations, secretions in the lung, intestine, pancreas, and reproductive tract are extremely viscous.

Question 41

What test was likely conducted to confirm the diagnosis of cystic fibrosis?

Answer 41

A genetic screen during the patient’s infancy was most likely conducted. A sweat chloride test can also confirm the diagnosis, but it may be difficult to collect an adequate amount of sweat in a baby. Patients with CF have elevated sweat chloride levels.

Question 42

What is the probable etiology of the patient’s current symptoms?

Answer 42

The lungs in patients with CF are colonized at an early age with various bacteria not normally found in the lung. Therefore, patients suffer from repeated pulmonary bacterial infections (Staphylococcus aureus, Haemophilus influenzae, and Pseudomonas aeruginosa are the most common organisms), which increase production of viscous secretions. These increased secretions lead to increased cough and pulmonary obstruction, which can result in acute respiratory distress.

Question 43

What vitamin supplements do patients with cystic fibrosis usually require?

Answer 43

Patients with CF generally require the fat-soluble vitamins A, D, E, and K. The thick secretions block the release of pancreatic enzymes, resulting in pancreatic insufficiency.

Question 44

What information can be provided if this patient asks for genetic counseling?

Answer 44

The frequency of CF in white people is 1: 2000; the carrier rate of CF in white people is 1:25. CF is an autosomal recessive disease, so all children of a patient with CF will at a minimum become carriers. Approximately 95% of males with CF are infertile because of defects in the transport of sperm. Infertility affects as many as 20% of women as a result of abnormally thick cervical mucus and amenorrhea from malnutrition.

Question 45

What is the prognosis for patients with cystic fibrosis?

Answer 45

* Prognosis for patients with CF is generally good. * Most patients are able to survive into their 30s and lead relatively normal lives.

Question 46

What is the most likely diagnosis?

Answer 46

Question 47

What is the pathophysiology of Emphysema?

Answer 47

Destruction of alveolar walls results in enlargement of air spaces. Compared with a normal lung (Figure 14-9A), the lung in emphysema (Figure 14-9B) shows destruction of lung parenchyma and marked dilatation of terminal air spaces. Destruction of lung parenchyma also decreases elastic recoil, which increases airway collapsibility, causing expiratory obstruction. As a result, patients with emphysema often find it easier to exhale through pursed lips (which maintains a high end-expiratory pressure, thereby stenting the alveoli open)—hence the term “pink puffers.” Because of chronic hyperinflation, lungs are expanded close to total lung capacity with little inspiratory reserve, and diaphragms are flattened to a point of significant mechanical disadvantage.

Question 48

What findings are expected on lung and heart examination in a patient with emphysema?

Answer 48

Air trapped in the lungs causes the chest to sound hyperresonant to percussion. Patients with COPD also have decreased breath sounds, wheezing, a prolonged expiratory phase, diminished heart sounds, and a PMI that may be displaced centrally.

Question 49

What pattern of lung parenchymal destruction is likely to be found in a patient with emphysema?

Answer 49

Smoking results in a destruction pattern termed centrilobular emphysema, which affects the respiratory bronchioles and central alveolar ducts. Panacinar emphysema is associated with α1-antitrypsin deficiency and results in destruction throughout the acinus.

Question 50

How do pulmonary function test results help distinguish emphysema from other lung diseases?

Answer 50

In COPD, pulmonary test results are likely to be consistent with obstructive lung disease findings: dramatically reduced forced expiratory volume in 1 second (FEV1) and reduced forced vital capacity (FVC), resulting in an FEV1/FVC ratio of < 70%. By contrast, in restrictive lung diseases, both the FEV1 and the FVC are reduced, resulting in a normal FEV1/FVC.

Question 51

What is the most likely diagnosis? What is the likely source of this infection? What additional microorganisms can cause this presentation?

Answer 51

Question 52

What is the main virulence factor of H influenzae?

Answer 52

The polysaccharide capsule is the major virulence factor of H influenzae, which has both encapsulated and nonencapsulated strains. The nonencapsulated forms are limited to local infections such as otitis media in children and mild respiratory infection in adults (Table 14-1). The encapsulated strains are significantly more virulent and can cause disseminated diseases such as meningitis, epiglottitis, and septic arthritis. There are six capsular types of H influenzae, designated a through f. The b-type capsule accounts for approximately 95% of serious H influenzae infections in children.

Question 53

How has the vaccine for H influenza been redesigned to improve its efficacy?

Answer 53

The Hib vaccine consists of a purified b-type capsule conjugated to diphtheria toxin. The diphtheria toxin activates T lymphocytes, which are required for adequate antibody production against the capsular antigen. The original vaccine consisted only of b capsule and was not effective in eliciting an antibody response.

Question 54

What is the most likely diagnosis?

Answer 54

The pleural thickening (indicated by the arrows in Figure 14-10) in addition to a history of exposure to asbestos makes the diagnosis of malignant mesothelioma of high concern. Benign pleural plaques could also present similarly. As the malignant mesothelioma progresses, the lung is surrounded and compressed by a thick layer of tumor. Although mesotheliomas are rare, an exposure history greatly increases the risk. Common features of the disease include dyspnea, chest pain, and pleural effusions.

Question 55

What occupations put patients at risk for exposure to asbestos?

Answer 55

Asbestos exposure is commonly seen in pipe fitters, shipyard workers, welders, plumbers, and construction workers. In addition to malignant mesothelioma, asbestos is associated with benign pleural plaques, interstitial lung disease, pleural effusions, and bronchogenic carcinoma. The diseases typically manifest several decades after asbestos exposure.

Question 56

What are the typical findings on pulmonary function testing in malignant mesothelioma?

Answer 56

Pulmonary function testing reveals a restrictive pattern. Tumor growth decreases lung expansion and total lung capacity. Both forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) are decreased, but the FEV1/FVC ratio is preserved.

Question 57

What is the prognosis for patients with malignant mesothelioma?

Answer 57

Given only supportive care, the median survival for patients with malignant mesothelioma is approximately 6–12 months. With very aggressive therapies, such as extrapleural pneumonectomy plus chemotherapy and radiation, the median survival can be as high as 34 months.

Question 58

What is the most likely diagnosis?

Answer 58

A pleural effusion consists of fluid accumulation in the pleural space (between the visceral pleura and the parietal pleura) of the lung. Normally, the pleural space is only a potential space, with a small amount of fluid.

Question 59

How are pleural effusions classified?

Answer 59

Question 60

What are the common causes of transudative pleural effusion? What are the common causes of exudative pleural effusion?

Answer 60

* Common causes of transudative pleural effusion include congestive heart failure, cirrhosis, constrictive pericarditis, nephrotic syndrome, and pulmonary embolism (PE). * Common causes of exudative pleural effusion include infection (pneumonia, tuberculosis), malignancy (primary or metastatic lung cancer or mesothelioma), collagen vascular disease, and PE (note that PE can cause both transudative and exudative pleural effusions).

Question 61

What are the typical laboratory findings in pleural effusion?

Answer 61

Analysis of pleural effusion fluid includes measuring pH, total protein, lactate dehydrogenase (LDH), glucose, cell count, gram stain and culture. Cytology can also be performed to identify malignant causes. Meeting any one of the three Light’s criteria qualifies the effusion as an exudate: - Protein effusion/serum ratio > 0.5 - LDH effusion/serum ratio > 0.6 - Pleural LDH level greater than two-thirds the upper limit of serum LDH level.

Question 62

What are the appropriate treatments for pleural effusion?

Answer 62

Thoracentesis performed by needle insertion into the pleural space is both diagnostic and therapeutic. The needle is inserted through an intercostal space superior to the rib to avoid the intercostal nerve and vessels, which lie in the intercostal groove at the inferior border of the rib. Other treatments include pleurodesis (in which the pleura is made adherent and closed by chemicals such as talc or doxycycline or physical abrasion) and permanent catheter insertion into the pleural space for periodic fluid drainage.

Question 63

What is the most likely diagnosis?

Answer 63

Mycoplasma pneumoniae, which causes primary atypical pneumonia (“walking pneumonia”), is the most common cause of pneumonia in teenagers (Table 14-2). This organism is the smallest free-living bacterium. It has no cell wall and its membrane is the only bacterial membrane containing cholesterol.

Question 64

What diagnostic tests can help confirm the diagnosis of Mycoplasma pneumoniae?

Answer 64

A high titer of cold agglutinins (IgM) and growth on Eaton agar (which is specific for growing M pneumoniae and contains penicillin for selectivity) indicate M pneumonia infection.

Question 65

What clinical findings are commonly associated with Mycoplasma pneumoniae?

Answer 65

Infection with M pneumoniae typically results in mild upper respiratory tract disease including low-grade fever, malaise, headache, and a dry, nonproductive cough. Symptoms gradually worsen over a few days and can last for more than 2 weeks. Less than 10% of patients develop more severe disease with lower respiratory tract symptoms. Classically, x-ray of the chest in these patients looks worse than would be predicted by their physical appearance.

Question 66

What is the pathogenicity of Mycoplasma pneumoniae

Answer 66

M pneumoniae is an extracellular organism that attaches to respiratory epithelium. As the superficial layer of respiratory epithelial cells is destroyed, the normal ability of the upper airways to clear themselves is lost. As a result, the lower respiratory tract becomes contaminated by microbes and is mechanically irritated. Close contact allows for spread of the organism.

Question 67

What hematologic condition can develop secondary to Mycoplasma pneumoniae?

Answer 67

Autoimmune hemolytic anemia due to cold agglutinins (usually IgM autoantibodies that are able to agglutinate RBCs at temperatures below 35°C) can lead to lysis and mild anemia. Cold agglutinin production peaks during the third week of M pneumoniae infection and resolves spontaneously.

Question 68

What are the appropriate treatments for Mycoplasma pneumoniae?

Answer 68

Azithromycin is most commonly prescribed to treat Mycoplasma infection. Tetracycline, clarithromycin, or erythromycin may be prescribed as well.

Question 69

What is the most likely diagnosis? What other conditions should be included in the differential diagnosis?

Answer 69

This is a case of pulmonary embolism (also known as pulmonary thrombo- embolism, or PTE).

Answer 70

Question 71

What is the Virchow triad?

Answer 71

The Virchow triad refers to the three factors that increase the risk for venous thrombosis: local injury to the vessel wall, hypercoagulability, and stasis. It is believed that patients with PTE are predisposed to venous thrombosis; triggers include pregnancy, limb immobility, and surgery.

Question 72

What is the most likely finding on microscopic examination in PE?

Answer 72

Under low-power magnification, char- acteristic lines of Zahn (alternating pale lines of platelets and fibrin with RBCs, indicating premortem clot for- mation) are visible in the thrombus.

Question 73

What test remains the gold standard for diagnosing PE?

Answer 73

Pulmonary angiography remains the most specific test available for definitively diagnosing PTE. However, because of the invasiveness of angiography, CT of the chest with thin cuts is the most frequently used diagnostic test. A ventilation-perfusion lung scan is still often used. A lung scan showing normal perfusion virtually excludes PTE. An x-ray of the chest can show signs of PTE including Hampton hump (a wedge-shaped indicator of infarction in a region served by an occluded vessel) and Westermark sign (oligemia distal to a PTE) but neither sign is specific and additional imaging is necessary to confirm the diagnosis. Plasma D-dimer levels have a negative predictive value in cases of low clinical suspicion but are elevated in more than 90% of patients with PTE. This assay is nonspecific and levels may also be elevated in conditions such as myocardial infarction or sepsis. The current strategy for diagnosing PTE and deep venous thrombosis is shown in Figure 14-12.

Question 74

What are the appropriate treatments for this condition?

Answer 74

PTE is treated with therapeutic levels of heparin for at least 5 days unless there is a contraindication to anticoagulation (eg, recent surgery). In most patients, warfarin and heparin may be started together and oral anticoagulation continued for at least 3 months. If there is a contraindication to anticoagulation or a high risk of recurrence of PTE, an inferior vena cava filter is recommended.

Question 75

What is the most likely cause of these symptoms? What is the most likely diagnosis?

Answer 75

The patient has respiratory acidosis (pH < 7.4 and PCO2 > 40 mm Hg) with compensatory metabolic alkalosis. Respiratory acidosis can be caused by COPD, airway obstruction, and hypoventilation. The patient has a chronic respiratory acidosis, as indicated by the large compensatory increase in bicarbonate to correct for an elevated PCO2. It is most likely due to her underlying COPD since a patient with a more acute process would not be able to compensate as robustly.

Question 76

In Figure 14-13, which area corresponds to respiratory acidosis, respiratory alkalo- sis, metabolic acidosis, and metabolic alkalosis?

Answer 76

Letter A in Figure 14-13 re- fers to respiratory acidosis, and letter B refers to meta- bolic acidosis. Letter C re- fers to respiratory alkalosis, and letter D refers to meta- bolic alkalosis.

Question 77

How is respiratory acidosis distinguished from metabolic acidosis?

Answer 77

In respiratory acidosis, the primary disturbance is an increase in PCO2 to which the body responds by increasing renal bicarbonate reabsorption. In metabolic acidosis, the primary disturbance is a decrease in bicarbonate, which is compensated for by hyperventilation, resulting in a decreased PCO2.

Question 78

What is the anion gap, and what factors can increase the anion gap in this condition?

Answer 78

Question 79

What is ILD and what are the common causes?

Answer 79

Question 80

What is the most likely cause of ILD in this patient?

Answer 80

Sarcoidosis is the most likely cause. This diagnosis is supported by the patient’s race, the presence of noncaseating granulomas (discrete collections of tissue macrophages termed histiocytes often organized into multinucleated giant cells without central necrosis), and the bilateral hilar lymphadenopathy on x-ray of the chest.

Question 81

What laboratory abnormalities may be found in a patient with sarcoidosis?

Answer 81

Vitamin D is secreted by the macrophages of the granulomas and is therefore elevated in serum. Angiotensin-converting enzyme is also secreted by the macrophages of the granulomas and is also elevated.

Question 82

What pulmonary function testing findings are expected in ILD?

Answer 82

In ILD, lung compliance is decreased, reflecting increased stiffness from alveolar wall inflammation and fibrosis. Tidal volume and total lung capacity are typically decreased. Diffusion capacity is also decreased as a result of inflammatory destruction of the air-capillary interface. Unlike most ILDs, sarcoidosis has features of both obstruction and restriction.

Question 83

What are some extrapulmonary manifestations of this patient’s ILD - sarcoidosis?

Answer 83

Common extrapulmonary manifestations of sarcoidosis are in the eye (anterior uveitis) and skin (papules and erythema nodosum), but granulomas can also occur in the heart, brain, lung, and peripheral lymph nodes.

Question 84

What is the appropriate treatment for ILD secondary to sarcoidosis?

Answer 84

Corticosteroids

Question 85

What is this most likely diagnosis?

Answer 85

Small cell lung carcinoma is strongly suggested by the central, hilar nature of the lung mass; a significant weight loss; and a serum sodium of 119 mEq/L, as a result of syndrome of inappropriate antidiuretic hormone (SIADH) as part of the paraneoplastic process.

Question 86

Which other paraneoplastic processes are associated with Small cell lung carcinoma?

Answer 86

Small cell lung carcinoma is known to cause hormonally mediated Cushing syndrome due to ectopic secretion of adrenocorticotropic hormone. In addition, up to 3% of patients with small cell lung carcinoma develop Lambert-Eaton myasthenic syndrome.

Question 87

What additional symptoms can arise from an intrathoracic cancer?

Answer 87

Symptoms for tumors within the thoracic cavity derive from their location and the structures they displace or disrupt, and include superior vena cava obstruction, hoarseness of the voice due to recurrent laryngeal nerve compression, phrenic nerve palsy resulting in dyspnea, dysphagia from esophageal compression, and stridor due to tracheal compression.

Question 88

To which areas do Small cell lung carcinomas commonly metastasize?

Answer 88

Small cell lung carcinoma is notable for its metastases to the central nervous system, liver, and bone. As a result, patients may present with bone pain, neurologic symptoms such as seizures or focal deficits, and pain in the right upper quadrant.

Question 89

What is the prognosis for patients with Small cell lung carcinoma?

Answer 89

Untreated patients with this disease have a median survival of only 6–17 weeks. However, with combination chemotherapy, median survival may increase to up to 70 weeks. The prognosis largely depends on the tumor’s reaction to chemotherapy; drugs include etoposide and cisplatin. Surgery is not an option in small cell carcinoma because of its early and highly aggressive metastasis.

Question 90

What is the most likely diagnosis?

Answer 90

Pneumothorax—more specifically, secondary spontaneous pneumothorax. Whereas primary spontaneous pneumothorax occurs in the absence of underlying lung disease, secondary spontaneous pneumothorax occurs in the setting of chronic lung parenchymal disruption.

Question 91

What is the pathophysiology of Pneumothorax?

Answer 91

Spontaneous pneumothorax is most likely caused by rupture of a subpleural bleb (a pocket of air caused by destruction of lung parenchyma near the pleural surface), which allows air to escape into the pleural cavity. A tension pneumothorax ensues when a one-way valve is created, allowing air to progressively accumulate with each inspiration. This expanded and pressurized pleural compartment shifts and compresses other intrathoracic structures.

Question 92

What diseases most often underlie Pneumothorax?

Answer 92

The most common underlying condition is chronic obstructive pulmonary disease. Additionally, patients with AIDS, Pneumocystis jiroveci (formerly carinii) pneumonia, cystic fibrosis, and tuberculosis are at higher risk for spontaneous pneumothorax.

Question 93

What is the most common clinical presentation of pneumothorax?

Answer 93

Dyspnea with pleuritic chest pain on the same side of the pneumothorax is a common presentation. Typical physical examination findings include diminished breath sounds, hyperresonance, and absent fremitus over the pneumothorax. Arterial blood gas testing typically shows hypoxia and hypercapnia.

Question 94

What are the typical radiologic findings in pneumothorax?

Answer 94

Partial collapse of the lung on the side of the pneumothorax with a thin line parallel to the chest wall is usually visible. In a tension pneumothorax, tracheal and mediastinal deviation can be present away from the pneumothorax. In a nontension pneumothorax, however, the trachea and mediastinum will remain unchanged or shift toward the side of the collapsed lung.

Question 95

What is the appropriate treatment for Pneumothorax?

Answer 95

For a tension pneumothorax, needle decompression at the second intercostal space at the midclavicular line is the initial treatment. Then, as with other pneumothoraces, a chest tube (thoracotomy) is placed at the fifth intercostal space at the midaxillary line. Small pneumothoraces may be treated with high concentration oxygen to facilitate nitrogen resorption and followed clinically and radiographically. In the case of repetitive pneumothoraces, parenchymal sclerosing agents such as physical and chemical irritants are used to adhere to layers of the pleura to prevent future pneumothoraces by a process called pleurodesis.