Pulmonology Notes

Pulmonology

Key Terms

• Cough: Protective reflex to clear the airway with explosive expiration.
• Sputum: Mucus coughed up, which can be examined to aid in diagnosis.
• Hemoptysis: Coughing up blood.
• Hypoxemia: Reduced levels of arterial oxygen (reduced PaO2).
• Hypoxia: Reduced oxygenation of cells in tissues.
• Hypercapnia: CO2 retention.
• Dyspnea: Subjective sensation of uncomfortable breathing.
• Dyspnea on exertion: Shortness of breath with activity.
• Orthopnea: Shortness of breath when lying down.
• Kussmaul respirations: Deep, rapid breathing pattern seen in patients with metabolic acidosis.
• Cheyne-Stokes respirations: Alternating periods of deep and shallow breathing and apnea. (Note: Many other abnormal breathing patterns exist with unique clinical names).

Signs/Symptoms of Respiratory Distress

• Use of accessory muscles of breathing.
• Retracting intercostal spaces.
• Flaring of nostrils.
• Tripod positioning.
• Other signs: hypoxemia, hypoxia, hypercapnia, tachycardia, tachypnea (increased respiratory rate), slow respiratory rate, hyper- or hypotension, cyanosis, confusion, etc.

Acute Respiratory Failure

• Inadequate gas exchange leads to either:
  • Hypoxemia/hypoxia (poor oxygenation)
  • Hypercapnia (poor ventilation)
• Multiple etiologies include trauma, injury, or infection of lungs, airways, chest wall, brain, spinal cord, heart, liver, etc., or from sedation and/or surgical procedures.
• Patients with a history of smoking, chronic renal failure, chronic liver failure, underlying lung disease, and infection have an increased risk of developing post-op respiratory failure.
• Patients may require oxygenation or ventilation support with non-invasive or invasive devices.

Pleura Abnormalities

Pneumothorax

*   Rupture of visceral or parietal pleura leads to the presence of air or gas in the pleural space, leading to collapse of lung tissue.
*   Causes:
    *   Primary or spontaneous: Caused by primary lung disease; typically occurs in otherwise healthy young males who smoke cigarettes and develop blebs (blisters) in lung tissue which may spontaneously rupture
    *   Secondary:
        *   Caused by chest trauma
        *   Iatrogenic: Caused by surgical procedure (central line placement) or medical treatment (mechanical ventilation)
*   Clinical manifestations: acute pleuritic chest pain, dyspnea, tachycardia, absent breath sounds on the affected side.
*   Can become life-threatening if they become too large or compress other structures.
    *   Tension pneumothorax: An emergency medical condition that requires immediate bedside treatment with a chest tube; common symptoms include severe hypoxemia and hypoxia, tracheal deviation, and hypotension.

Pleural Effusions

• Presence of fluid in the pleural space.
• Types:
  • Transudative effusion: Watery and diffuses out of the capillaries.
  • Exudative effusion: Less watery; contains high concentrations of white blood cells and plasma proteins.
  • Hemothorax: Bloody exudate.
  • Empyema: Pus.
• Clinical manifestations: May be asymptomatic or cause dyspnea and pleural pain.
• Treatment: Watchful waiting versus thoracentesis, chest tube, and/or surgery depending on size and symptoms.

Restrictive Lung Diseases

• Refers to a reduction of lung volume caused by reduced lung compliance.
• Examples:
  • Aspiration pneumonitis: Chronic aspiration of food and liquid leads to irritation/inflammation of lung tissue and decreased compliance.
  • Atelectasis: Deflation of alveoli leading to collapse of lung tissue.
  • Pulmonary fibrosis: Development of excess fibrous or connective tissue due to acute or chronic inflammation or injury.
  • Acute respiratory distress syndrome (ARDS)

Acute Respiratory Distress Syndrome (ARDS)

• Most severe form of acute lung injury caused by acute inflammation and alveolocapillary injury.
• Characterized by the onset of bilateral lung infiltrates on x-ray and low ratio of PaO2 to the fraction of inhaled oxygen.
• Clinical manifestations:
  • Dyspnea and hypoxemia with poor response to oxygen supplementation
  • Hyperventilation and respiratory alkalosis
  • Decreased tissue perfusion, metabolic acidosis, and organ dysfunction
  • Increased work of breathing and hypoventilation
  • Hypercapnia, respiratory acidosis, and worsening hypoxemia
  • Decreased cardiac output, hypotension, death

Obstructive Lung Diseases

• Caused by obstruction of bronchi.
• Two main types:
  • Asthma
  • Chronic Obstructive Pulmonary Disease (COPD):
    • Chronic bronchitis
    • Emphysema

Asthma

• Chronic inflammatory disorder of the bronchial mucosa.
• Causes bronchial hyperresponsiveness and airway constriction.
• Asthma is reversible (constricted bronchi can return to normal and stop impeding airflow).
• Characterized by episodic attacks of bronchospasm, bronchial inflammation, mucosal edema, and increased mucous production.
• Exposure to antigen leads to activation of innate and adaptive immunity:
  • Early asthmatic response
    • Dendritic cells present antigen to helper T cells, which release inflammatory cytokines/chemokines that trigger bronchospasm and lead to airway obstruction.
    • Typically peaks within 30 minutes of exposure to antigen and resolves within 1-3 hours.
  • Late asthmatic response
    • Release of chemokines during early response results in recruitment of other WBCs, leading to inflammation and injury to pulmonary tissue if left untreated.
    • Begins 4-8 hours after early response and results in bronchial hyperresponsiveness (increased sensitivity to antigens).
• Clinical manifestations:
  • Asymptomatic between attacks.
  • At the beginning of attacks, patients experience chest tightness, dyspnea, expiratory wheezing, coughing, tachypnea, tachycardia.
  • If severe, patient may progress to develop respiratory distress, respiratory acidosis, and acute respiratory failure.
    • Ominous signs include absent breath sounds on chest auscultation.
    • Status asthmaticus: Life-threatening condition in which bronchospasm is not reversible by typical treatment methods.
• Treatment:
  • Primary treatment of acute attacks consists of aerosolized bronchodilator (beta-agonists) administered through nebulizers or inhalers.
    • Function to reverse symptoms of asthma by dilating the previously constricted bronchi
  • Other supportive treatments may include inhaled steroids and anti-inflammatory medications.

Chronic Obstructive Pulmonary Disease

• Also known as COPD.
• Risk factors include smoking (cigarette, pipe, cigar, secondhand smoke), occupational hazards, air pollution, and genetic factors.
• Unlike asthma, COPD is not fully reversible.
• Two main types:
  • Emphysema
    • Inhalation of irritants leads to inflammation of alveoli
    • Destruction of alveoli via breakdown of elastin within septa and permanent enlargement of gas-exchange airways.
  • Chronic bronchitis
    • Inhalation of irritants leads to inflammation of bronchi goblet cells.
    • Stimulates mucus secretion which becomes thickened and impairs bronchial ciliary function.
• Clinical manifestations:
  • Most common symptom is dyspnea on exertion.
  • Other symptoms depend on the type of COPD.
• Treatment:
  • Smoking cessation, vaccination, exercise.
  • Aerosolized bronchodilators, anti-muscarinic agents, steroids.

Respiratory Infections

Upper Respiratory Infections

• Very common; typically self-limited and mild.
• Examples: viral colds, pharyngitis (sore throat), laryngitis (inflammation of voice box).

Lower Respiratory Infections

• Acute bronchitis
  • Acute infection of inflammation of large airways (bronchi).
  • Self-limiting and typically caused by viral infections; may also be due to bacteria but rare unless the patient has COPD.
  • Clinical manifestations are similar to pneumonia; however, chest x-ray does not demonstrate infiltrates.
  • Treatment with supportive measures.
• Pneumonia
  • Infection of the lower respiratory tract.
  • May be caused by bacteria, viruses, or fungi (less likely protozoa or parasites).
  • Risk factors include advanced age, immunodeficiency, underlying lung disease, alcohol use, aspiration, chest trauma, endotracheal intubation, immobilization, etc.
  • Categorized based on how it was obtained:
    • Community Acquired (CAP)
    • Hospital Acquired (HAP)
    • Ventilator Associated (VAP)
    • Each type is associated with different causative agents, which affects the antibiotics of choice.
  • Clinical manifestations:
    • Symptoms may differ based on the causative agent.
    • Patients will first experience a viral upper respiratory tract infection which then leads to viral or bacterial pneumonia
    • Other common symptoms include cough, pleuritic chest pain, fever, chills, and malaise.
    • Severe pneumonia may progress to sepsis.

Tuberculosis

• Caused by infection with Mycobacterium tuberculosis.
  • Acid-fast bacillus (will not stain on gram stain tests).
• Leading cause of death from curable infectious diseases.
• Highly contagious and spread by airborne droplets (aerosol transmission).
• Typically affects the lungs but able to invade other organs.
  • Hides inside macrophages and can become dormant (latent tuberculosis).
  • Host cells may respond by creating caseating granulomas.
  • Disease may reactivate if patient becomes immune-compromised.
• Clinical manifestations include fever, cough, hemoptysis, weight loss, night sweats.
  • Latent tuberculosis is asymptomatic

Pulmonary Vascular Disease

Pulmonary Embolism

• Occlusion of a portion of the pulmonary vascular bed by a thrombus, embolus, tissue fragment, lipids, foreign body, amniotic fluid, or air bubble.
  • Most commonly arise from the deep veins in the thigh/calf (DVTs).
• Risk factors include Virchow’s triad:
  • Venous stasis, hypercoagulability, and injuries to the endothelial cells that line blood vessels.
• Clinical manifestations include sudden onset of pleuritic chest pain, dyspnea, tachypnea, tachycardia, unexplained anxiety, cardiac arrest, and death.
• Pulmonary embolism will not appear on an x-ray or regular CT scan (need to order CT angiogram).
• Treatment:
  • Prevention.
  • Oxygen and hemodynamic stabilization.
  • Anticoagulation and/or fibrinolytic agents.
  • May need embolectomy.

Lung Cancer

• Most frequent cause of cancer death in the United States.
• Risk factors include cigarette smoking (most common cause), air pollution (including secondhand smoke), occupational hazards, genetic factors, etc.
  • 10-20% of patients with lung cancer never smoked.
• Multiple Different types are mostly divided into two main classes:
  • Neuroendocrine tumors
  • Nonsmall cell lung cancer
• Staging is based on the Tumor Nodes Metastasis (TNM) system.
• Treatment includes surgical resection, chemotherapy, radiation, and newer immunotherapies.

Pediatric Pulmonary Diseases

Croup

• Also goes by many other names including laryngotracheobronchitis.
• Infection of the upper airway that leads to obstruction.
• Most commonly caused by viral infections.
• Common in children ages 6 months to 5 years of life.
• Common manifestations include harsh barking cough (“seal-like cough”), hoarse voice, and inspiratory stridor.
• Most cases of croup are mild and self-limited, but some may require hospitalization.

Cystic Fibrosis

• Autosomal recessive genetic disorder leading to multisystem organ disease.
• Gene mutation leads to abnormal chloride channel:
  • Cells are unable to transport chloride outside of the cell.
  • Normally, chloride outside of the cell would attract a layer of water molecules that helps moisturize and thin secretory mucus.
  • Without water, the cells produce mucus that is dehydrated, thickened, and prone to sticking together.
• Affects secretory tissues such as the lungs, intestines, pancreas, sweat ducts, and reproductive organs (vas deferens).
• Especially injurious to lung tissue, as thick secretions can:
  • Obstruct bronchioles (mucus plugging).
  • Result in chronic inflammation.
  • Lead to increased risk of infections.
• Signs and symptoms include persistent cough or wheeze, excess sputum production, hemoptysis, recurrent and/or severe pneumonia, and symptoms of chronic hypoxia such as nail clubbing.
• All newborns in the United States are screened for cystic fibrosis.
• Treatment:
  • There is no cure for cystic fibrosis
  • Multidisciplinary support.
    • Lung support with chest physical therapy via oscillation vests, nebulizer therapy, and antibiotics as needed.
    • New targeted therapies are available for certain forms of cystic fibrosis based on the genetic mutation.
    • May need lung transplant if at end-stage lung disease.
    • May need nutritional support given intestine and pancreatic involvement:
      • Pancreatic enzymes and fat-soluble vitamins.
  • Genetic counseling
  • Life expectancy is around 44 years of age for children born 2014-2018.

Sudden Infant Death Syndrome

• Sudden death of an infant <1 year of age which remains unexplained despite investigation by autopsy, review of clinical history, and examination of death scene.
• Most common cause of infant death in the United States.
• Almost always occurs during night-time sleep.
• More common in the first 2-4 months of life and rare after 6 months of age.
• More common during winter months.
• Risk factors:
  • Preterm or low birth weight, multiple births, positive family history.
  • Environmental stressors.
• Prevention of SIDS:
  • AVOID prone sleeping (sleeping on belly) or side sleeping; only use supine sleeping positions (sleeping on back).
  • AVOID soft bedding, toys, and blankets in the crib; only use firm sleeping surfaces with fitted sheets and without the presence of toys or blankets in the crib.
  • AVOID bed sharing (baby should sleep in designated crib or bassinet compliant with safety standards).
  • Encourage breast feeding and routine immunization.
  • Cardiovascular home monitoring devices may be used in certain cases but have not been proven to reduce risk of SIDS