altered ventilation and diffusion

Anatomy of the Respiratory System

  • Lungs: Major organ of the respiratory system responsible for gas exchange (oxygen and carbon dioxide).

    • Pyramid-shaped and paired.

    • Connected to the windpipe with left and right bronchi, which subdivide into lobes.

    • Each segment supplied by its blood artery supply.

Functions of the Lungs

  • Gas Exchange: Transfers oxygen from the atmosphere to the blood and carbon dioxide from the blood to the atmosphere.

  • Ventilation: Mechanical process of breathing.

  • Host Defense: Protects from pathogens and particulate matter.

  • Angiotensin Conversion: Converts angiotensin I to angiotensin II.

  • Surfactant Production: Produced by type II alveolar cells, surfactant is essential for keeping alveoli inflated by reducing surface tension.

Lung Mechanics and Compliance

  • Compliance: Refers to the ease of lung expansion.

    • Decreased lung compliance results in stiff lungs (e.g., pulmonary fibrosis).

    • Conditions with decreased compliance include ARDS, pulmonary fibrosis, and obstructive diseases.

Ventilation Process

  • Inspiration (Inhalation): Breathing in oxygen.

  • Expiration (Exhalation): Breathing out carbon dioxide, regulated by neuronal impulses and lung receptors.

    • Key Muscles: Intercostal, diaphragm, sternocleidomastoid.

  • Airway Resistance: Affects how easily air can move in and out of the lungs.

Surfactant and Alveoli

  • Surfactant: A slippery lipoprotein that keeps the lungs inflated and prevents alveolar collapse.

  • Gas Exchange Mechanism: Gas moves from high concentration (alveoli) to low concentration (blood) via diffusion.

Definitions of Lung Volumes

  • Tidal Volume: Air volume exchanged during normal breathing.

  • Vital Capacity: Maximum air volume moved in and out during a forced breath.

  • Residual Volume: Air remaining in the lungs after maximum expiration.

  • Total Lung Capacity: Sum of vital capacity and residual volume.

Gas Transport in Blood

  • Oxygen Transport: Primarily as oxyhemoglobin (96-98% bound to hemoglobin) and 2-4% dissolved in blood.

  • Partial Pressures: Measured in mmHg, indicating the concentration of gases in arterial blood.

Hypoxia vs. Hypoxemia

  • Hypoxia: Insufficient oxygen to tissues.

  • Hypoxemia: Insufficient oxygen in the arterial blood.

  • Signs of Hypoxemia: Increased heart rate, hypotension, cyanosis, increased respiratory rates, etc.

Common Respiratory Diseases

Pneumonia

  • Definition: Inflammation of lung structures (alveoli and bronchi), caused by infection.

  • Signs/Symptoms: Fever, cough, sputum production, shortness of breath, chest pain.

  • Diagnostics: Blood tests, chest X-ray, sputum culture.

  • Treatment: Oxygen therapy, antibiotics, pulmonary toilet (chest physiotherapy).

Emphysema

  • Definition: Destruction of alveolar walls leading to impaired gas exchange.

  • Signs/Symptoms: Shortness of breath, barrel chest, chronic cough.

  • Treatment: Smoking cessation, pharmacological therapy (bronchodilators), potential lung transplant.

Bronchitis

  • Definition: Inflammation of bronchial tubes with excess mucus production.

  • Signs/Symptoms: Chronic cough, sputum production, shortness of breath.

  • Treatment: Smoking cessation, bronchodilator therapy, pulmonary rehab.

Asthma

  • Definition: Chronic inflammatory disease of the airways, leading to hyper-responsiveness.

  • Signs/Symptoms: Wheezing, chest tightness, shortness of breath.

  • Treatment: Short-term rescue medications, long-term control medications.

Cystic Fibrosis

  • Definition: Genetic disorder characterized by thick, sticky mucus production leading to lung and digestive problems.

  • Signs/Symptoms: Frequent lung infections, salty skin, digestive issues.

  • Treatment: Chest physiotherapy, pharmacological therapy, nutritional support.

ARDS (Acute Respiratory Distress Syndrome)

  • Definition: Life-threatening condition with fluid accumulation in alveoli, impairing gas exchange.

  • Signs/Symptoms: Severe dyspnea, tachypnea, crackles.

  • Treatment: Management of underlying cause, mechanical ventilation, supportive care.

COPD (Chronic Obstructive Pulmonary Disease)

  • Definition: Includes chronic bronchitis and emphysema; characterized by obstructed airflow.

  • Signs/Symptoms: Chronic cough, shortness of breath, hypoxia, fatigue.

  • Treatment: Smoking cessation, bronchodilators, corticosteroids, oxygen therapy.

Additional Concepts

Atelectasis

  • Definition: Collapse or incomplete expansion of the lung due to airway obstruction or compression.

  • Signs/Symptoms: Tachypnea, dyspnea, decreased breath sounds.

VQ Mismatch

  • Definition: Imbalance between ventilation (V) and perfusion (Q), affecting efficient gas exchange.

COVID-19

  • Overview: Viral infection caused by SARS-CoV-2 leading to respiratory distress.

  • Signs/Symptoms: Hypoxia, shortness of breath, potential to progress to acute respiratory failure.

  • Prevention/Treatment: Vaccination, monoclonal antibodies, high flow oxygen, mechanical ventilation if needed.