Notes on Upper and Lower Respiratory Disorders

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A-a gradient:

• Difference between arterial and alveolar PO2.

Ventilation defect:

• No O2 in lung; Respiratory distress syndrome.

Perfusion defect:

• No blood in lung; pulmonary embolus.

Diffusion defect:

• No gas exchange between blood and alveoli; interstitial fibrosis; pulmonary edema.


• Used to differentiate between restrictive and obstructive lung disease.

Upper airway disorders:

Choanal atresia:

• Bony septum between nose and pharynx; cyanotic baby while being breast-fed.

Upper airway disorders:

Nasal polyp:

• Due to inflammation, allergies, etc.

• Blocked cyclooxygenase, leaves lipoxygenase pathway open.

• Increased leukotrienes, causing bronchoconstriction.

Obstructive sleep apnea:

• Excessive snoring with breath cessation.


• Pulmonary hypertension, polycythemia.


• CPAP; weightloss.


• Maxillary sinus in adults; ethmoid sinus in children.

• Causes: Upper respiratory infections, deviated nasal septum, allergies, smoking.

• S. pneumoniae is most common.

• Blocked drainage into nasal cavity.

• Fever, congestion, pain.

Nasopharyngeal carcinoma:

• Male dominant.

• Squamous cell carcinoma; metastasis to lymph nodes.

Laryngeal carcinoma:

• Smoking, alcohol, squamous papillomas, papillomatosis.

• Located in true vocal cords.

• Hoarseness.


Resorption atelectasis:

• Collapsed lung.

• Air doesn't reach alveoli.

• Caused due to: mucus, foreign material, bronchogenic carcinoma.

• Fever, dyspnea.

• Absent breath sounds.

• Ipsilateral elevation of diaphragm, and tracheal deviation.

Compression atelectasis:

• Small airways compressed by air or fluid.

• Eg., tension pneumothorax; pleural effusion.

Due to loss of surfactant:

• Surfactant (phosphatidylcholine) is synthesized by type II pneumocytes.

• RDS in newborns: due to prematurity, maternal diabetes, C-section.

• Intrapulmonary shunting in newborn

• Ground glass appearance in chest radio graph.

• O2 therapy may cause superoxide free radical damage; blindness.

• Intraventricular hemorrhage.

• PDA.

• Hypoglycemia, enterocolitis.

Acute lung injury:

Pulmonary edema:

• Altered Starling pressure.

• Increased hydrostatic; decreased oncotic pressure.

• Infections, drugs, aspiration, high-altitude.

Acute respiratory distress syndrome:

• Pulmonary edema due to alveolar-capillary damage.

• Caused by: sepsis, gastric aspiration, trauma/shock, infections, smoke, heroin.

• Cyokines released; leakage of protein-rich exudate; decreased surfactant.


Pulmonary infections:

Community acquired pneumonia:

• Often due to S. pneumoniae.

• Acute bronchitis; lung has areas of consolidation.

Lobar pneumonia:

• Complete consolidation of lobe.

• Complications: lung abscesses, empyema, sepsis.

• Findings: fever, cough, positive Gram stain, leukocytosis.

Community-acquired pneumonia:

• M. pneumoniae.

• C. pneumoniae.

• C. trachomatis.

• RSV, influenzavirus, adenovirus.

• Insidious onset; fever, productive cough.

• Flu-like symptoms.

• No consolidation.

Nosocomial pneumonia:

• Severe underlying disease.

• Antibiotic therapy.

• Immunosuppression.

In immunocompromised hosts:

• AIDS, bone marrow transplants.

• CMV; P. jiroveci; A. fumigatus.


• M. tuberculosis.

• PPD test.

• Primary and secondary (reactivation) TB.

• Fever, night sweats, weight loss.

• Miliary spread within lungs and extrapulmonary sites.

• Granulomatous hepatitis; Pott's disease (vertebra).

M. avium-intracellulare complex:

• Atypical mycobacterium.

• TB in AIDS.

Lung abscess causes:

• Patients with depressed cough reflexes inhale oropharyngeal material.

• Infection by: Streptococci, Staphylococcus, Prevotella, Fusobacterium, Klebsiella.

• Findings: spiking fever, productive cough with foul smelling sputum.

Vascular lung lesions: pulmonary thromboembolism:

• Originate from femoral vein.

• Emboli occlude pulmonary vessels.

• Findings: increased pulmonary artery pressure.

• Decreased blood flow to pulmonary parenchyma.

• Majority located in lower lobes.

• Increased pulmonary artery pressure.

• Dyspnea, tachypnea, fever, chest pain, friction rub, effusion.

• Increased A-a gradient.

• Positive D-dimers; pulmonary angiogram.

Pulmonary hypertension:


• More common in women.

• Vascular hyperreactivity with smooth muscle proliferation.


• Endothelial cell dysfunction.

• Hypoxemia and/or respiratory acidosis.


• Hypoxemia, respiratory acidosis, loss of pulmonary vasculature, left-to-right cardiac shunts, mitral stenosis.


• Dyspnea and chest pain, right-sided heart failure; cor pulmonale.

Restrictive lung diseases:

• Reduced total lung capacity.

• Causes: chest wall disorders.

• Interstitial lung diseases.

Interstitial fibrosis:

• Cytokines released; fibrosis stimulated.

• Decreased lung compliance.

• Increased lung elasticity.

• Dry cough.

• Dyspnea.

• Late inspiratory crackles in lower lung fields.


• Mineral dust inhalation.

• Coal dust, silica, asbestos, tobacco smoke.

• Macrophages swallow dust particles and become dust cells.

• Restrictive lung diseases: Coal worker's pneumoconioses:

• Black lung disease.

• Caplan syndrome may occur.


• Quartz dust inhaled.


• Nuclear and aerospace industry.


• Idiopathic multisystem granulomatous disease.

• Targets lung.

• Dyspnea.

• Active CD4 Th cells.

• Skin lesions.

• Increased ACE, hypercalcemia.

• Enlarged hilar and mediastinal lymph nodes (potato nodes).

Idiopathic pulmonary fibrosis:

• Repeated cycles of alveolitis triggered by unknown causes.

Collagen Vascular diseases:

• Systemic sclerosis.

• SLE.

• Rheumatoid arthritis.

• Caplan syndrome = rheumatoid nodules + pneumoconiosis.

Hypersensitivity pneumonitis:

• Idiopathic allergic alveolitis.

• IgE not involved.

• Farmer's lung: exposure to thermophilic actinomycetes bacteria, ie., Saccharopolyspora rectivirgula.

• Silo filler's disease: gas inhalation from plant material.

• Byssinosis: inhalation in textile industries.

Obstructive lung diseases:


• Enlargement of respiratory unit.

• Causes: smoking, AAT deficiency.

• Increased compliance; decreased elasticity.

• Centriacinar emphysema: common in smokers; upper lobes.

• Panacinar emphysema: AAT deficiency; AD disease; lower lobes.

• Pink puffers; dyspnea and hyperventilation.

Chronic bronchitis:

• Productive cough for 2 months - 3 years.

• Smoking, cystic fibrosis.

• Hypersecretion of mucus from bronchi.

• Acute inflammation.

• Dyspnea.

• Cyanosis of skin.

• Blue bloaters; stocky patients.

• Cor pulmonale (hypertrophy of right ventricle due to lung disease).

• Respiratory acidosis.


• Episodic and reversible airway disease.

Extrinsic asthma:

• Type I hypersensitivity; CD4 Th2 cells; bronchoconstriction, mucus production, influx of leukocytes.

• IL4 = isotype switching to IgE production.

• IL5 = production and activation of neutrophils.

• Histamine released.

• Late phase reaction: eotaxin produced; eosinophils cause airway constriction.

• Charcot-Leyden crystals in terminal bronchioles.

• Expiratory wheezing, nocturnal cough, increased anteriorposterior diameter.

Intrinsic asthma:

• Non-immune.

• Caused by viral infections, air-pollutants, drug-sensitivity, stress, exercise, smoking.


• Permanent dilation of bronchi and bronchioles.

• Cartilage and elastic tissue destruction.

• Causes: CF, TB, bronchial obstruction, primary ciliary dyskinesia.

• Lower lobes.

• Productive cough; copious sputum.

Cystic fibrosis:

• AR disease.

• Three nucleotide deletion on chromosome 7.

• Defective CFTR for chloride ions.

• Increased Na/Cl in sweat, causing dehydration.

• Nasal polyps, respiratory infections and failure.

• Malabsorption.

• Type 1 diabetes mellitus.

• Male infertility.

Lung tumors:

• Most common cancers: adenocarcinoma; weak smoking association.

Association with smoking:

• Squamous cell carcinoma; small cell lung carcinoma.

Metastatic lung cancer:

• Most common.

• Primary site: breast.

• Secondary site: colon, renal.

• Dyspnea.

• Cough, hemoptysis, weight loss, chest pain.

• Pancoast tumor: Horner's syndrome.

• Superior vena cava syndrome.

Metastasis sites:

• Most common: hilar nodes.

• Also spreads to adrenal glands, liver.

Mediastinal masses:

• Commonly: neurogenic tumors.

• Thymoma: located in anterior mediastinum.

Pleural fluid:

• Moves from parietal pleura to pleural space to lungs.

Plural effusion:

• Movement of fluid from lymphatic vessels into pulmonary tissue.


• Increased hydrostatic pressure, decreased oncotic pressure, lymphatic obstruction, increased vessel permeability, metastasis to pleura.


• Ultrafiltrate; disturbed Starling pressures; protein/serum less than 0.5.


• Protein-rich, and cell-rich fluid; pneumonia, infarction, metastasis; protein/serum greater than 0.5.

Spontaneous pneumothorax:

• Idiopathic; hole in pleura.

• Pleural hole.

• Pleural cavity pressure = atmospheric pressure.

• Trachea deviates to side of pneumothorax.

• Sudden dyspnea, chest pain.

Tension pneumothorax:

• Ruptured tension pneumatocysts.

• Trauma to lungs; knife wound.

• Increased pleural cavity pressure; compression atelectasis.

• Absent breath sounds.

• Trachea and mediastinal structures deviate to opposite side.


• Insert needle into pleural cavity to relieve pressure.

Additional Reading:

Basic Pathology

1. Cell Injury
2. Inflammation and Repair
3. Immunopathology
4. Water, Electrolyte, Acid-Base, Hemodynamic Disorders
5. Genetic and Developmental Disorders
6. Environmental Pathology
7. Nutritional Disorders
8. Neoplasia
9. Vascular Disorders
10. Heart Disorders
11. Red Blood Cell Disorders
12. White Blood Cell Disorders
13. Lymphoid Tissue Disorders
14. Hemostasis Disorders
15. Blood Banking and Transfusion Disorders
16. Upper and Lower Respiratory Disorders
17. Gastrointestinal Disorders
18. Hepatobiliary and Pancreatic Disorders
19. Kidney Disorders
20. Lower Urinary Tract and Male Reproductive Disorders
21. Female Reproductive and Breast Disorders
22. Endocrine Disorders
23. Musculoskeletal Disorders
24. Skin Disorders
25. Nervous System Disorders
26. Notes on Tissue Regeneration
27. A Table of Bleeding Disorders
28. FAQ on Structure and Function of Red Blood Cells
29. FAQ on Components of Blood
30. Notes on Hemostatic Mechanisms
31. What is Fever?
32. What is Edema?
33. FAQ on Blood Pressure
34. FAQ on principles of fluid and flow dynamics of Blood
35. Causes of Thrombocytopenia
36. Squamous cell carcinoma of head and neck mucosa
37. Four tumors which never metastasize to the brain
38. What is caustic injury?
39. What causes Peripheral Edema?

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