Patho Respiratory Spring 2025 RB

PATHOPHYSIOLOGY OF THE RESPIRATORY SYSTEM

  • Presented by Roxanne Bennett, DNP, NP-C

Learning Objectives

  • Describe normal pulmonary airflow and gas exchange mechanisms.
  • Discuss how ventilation and perfusion alterations affect blood oxygenation.
  • Identify common etiologies and risk factors of pulmonary disease.
  • Discuss the physiologic consequences and clinical manifestations of pulmonary disease.
  • Distinguish between different lung disease types.
  • Describe how pulmonary disease influences cardiac function.

Function of the Respiratory System

  • Primary function: Supply O2 to body cells and remove CO2 & waste products.

Components of the Respiratory System

  • Includes:
    • Mouth/nose/pharynx
    • Upper/lower airways
    • Lungs and alveoli
    • Vasculature/capillaries
    • Red blood cells and tissue cells

Mechanisms of Ventilation

  • Inspiration (Inhalation): Chest cavity increases size, negative intrapleural pressure, air drawn into lungs.
  • Expiration (Exhalation): Elastic recoil of stretched structures decreases chest cavity size, increasing intrapleural pressure.

Gas Exchange (Diffusion)

  • Transfer of gases between alveoli and pulmonary capillaries, affected by ventilation/perfusion factors.

Factors Hindering Ventilation

  • Mucus or bronchoconstriction (COPD, Asthma)
  • Loss of accessory muscle function (Neurological disorders)
  • Blocked airway
  • Drug-induced bradypnea (sedatives, narcotics)

Gas Transport in Blood

  • Oxygen Transport:
    • 98% attached to hemoglobin, 2% dissolved in plasma.
  • Carbon Dioxide Transport:
    • 60% as bicarbonate, 30% attached to hemoglobin, 10% dissolved in plasma.

Lung Compliance

  • Refers to lung's ability to stretch and expand.
  • Affected by:
    • Elastin fibers (stretchable protein)
    • Surfactant (reduces surface tension, eases breathing)

Pulmonary Disorders

Lung Inflation Disorders

  • Pleural Effusion: Fluid accumulation in pleural cavity due to imbalance of fluid formation/removal.
  • Pneumothorax: Air in intrapleural space, causing lung collapse.
  • Atelectasis: Incomplete lung expansion due to various causes.

Restrictive Lung Disorders

  • Intrinsic: Includes interstitial lung disease and pneumonia.
    • Caused by inhalants, toxins, pathogens.
  • Extrinsic: Pressure from outside lungs (obesity, chest deformities).

Obstructive Airway Disorders

  • Impaired expiration leads to air trapping (Asthma, COPD).

Asthma

  • Characterized by airway inflammation, hyper-responsiveness, and obstruction.

COPD

  • Results in chronic airflow obstruction typically caused by smoking.
  • Includes emphysema and chronic bronchitis.

Clinical Features of Emphysema

  • Symptoms: Dyspnea, tachypnea, pursed-lip breathing, barrel chest.

Clinical Features of Chronic Bronchitis

  • Symptoms: Chronic cough, purulent sputum, dyspnea.

Pulmonary Embolism (PE)

  • Blockage in pulmonary arteries from various sources (thrombus, air, fat).
  • Risk factors: Surgery, malignancy, immobilization, etc.

Pulmonary Hypertension

  • Elevated pressures in pulmonary arteries, leading to symptoms like SOB, dizziness, chest pain.

Cor Pulmonale

  • Right-sided heart failure due to pulmonary causes (COPD, pulmonary hypertension).

Respiratory Diagnostics

Arterial Blood Gases (ABG)

  • Evaluates oxygen and CO2 levels, pH balance of the blood.
  • Important for diagnosing respiratory failures.

Hypoxia, Hypoxemia, & Hypercapnia

  • Hypoxia: Insufficient oxygen in tissues.
  • Hypoxemia: Low arterial blood O2 levels.
  • Hypercapnia: Increased CO2 levels in the blood.

Types of Respiratory Failure

  • Type I (Hypoxemia): PaO2 <60 mmHg.
  • Type II (Hypercapnia): PaCO2 >50 mmHg.