Gas Exchange

Gas exchange is the process by which oxygen is transported to cells and carbon dioxide is transported from cells

Key Related Terms

  • Hypoxia: Insufficient oxygen reaching cells

  • Anoxia: Total lack of oxygen in body tissues

  • Hypoxemia: Reduced oxygenation of arterial blood

  • Ischemia: Insufficient flow of oxygenated blood to tissues


Optimal gas exchange <——————————> No gas exchange

The more impaired gas exchange becomes, the more compromised the body becomes from insufficient oxygen (hypoxia)

Normal Physiological Process

Ventilation & Regulation:

  • Breathing is involuntary and regulated by the nervous system to maintain normal arterial blood gas levels

  • Chemoreceptors in the medulla sense CO₂ levels and stimulate diaphragm/intercostal muscle contraction

  • Atmospheric air (~21% oxygen) enters through patent airways

Alveolar Function:

  • Type I alveolar cells: Provide structure

  • Type II alveolar cells: Produce surfactant to keep alveoli open

Gas Diffusion:

  • Oxygen diffuses from alveoli into pulmonary capillaries based on pressure gradients

  • Gases diffuse from high to low concentration independently

  • PaO₂: Partial pressure of oxygen dissolved in arterial plasma

  • Oxygen attaches to hemoglobin in erythrocytes for transport to cells

O2 and CO2 are not exchanged/traded with each other!


Consequences of impaired Gas Exchange:

Mild Impairment:

  • Fatigue (compensatory mechanism to reduce oxygen demand)

  • Increased heart rate and respiratory rate

Moderate to Severe Impairment:

  • Reduced mitochondrial respiration and oxidative metabolism

  • CO₂ buildup leading to acid accumulation

  • Respiratory acidosis: When ventilation is impaired

  • Metabolic acidosis: When transport/perfusion is impaired

  • Cellular ischemia and necrosis if prolonged

Complete Cessation: Quickly results in death


Priority Nursing Interventions for Impaired Gas Exchange

1. Positioning

  • Elevate head of bed: Place patients in high-Fowler, Fowler, or semi-Fowler position

  • These positions use gravity to move the diaphragm away from the lungs, reducing work of breathing

  • Patients with chronic pulmonary disease may prefer a tripod position or leaning forward over a table

  • Lying horizontally: For hypoxemic patients with acute lung disease, gravity-dependent areas of the lung become best ventilated and perfused

Assessment Data:

clinical findings: cough, sputum (assess the characteristics of it/color)

2. Oxygen Therapy

Collaborate with respiratory therapists to deliver humidified oxygen:

Nasal Cannula:

  • Delivers 24% oxygen (1 L/min) to 44% oxygen (6 L/min)

  • Safe for long-term use; allows eating, talking, and coughing

  • High-flow nasal cannulas can deliver up to 60 L/min

⚠ COPD Precaution:

  • Do not exceed 3 L/min unless necessary for patients with CO₂ retention

  • Their bodies adapt to high CO₂ levels; low oxygen becomes their breathing stimulus

  • Excessive oxygen can eliminate their drive to breathe, causing hypoventilation and potential death

Face Masks:

  • Simple face mask: 35-50% oxygen at 6-12 L/min

  • Partial/nonrebreathing masks: 60-90% oxygen at 10-15 L/min

  • Venturi masks: Precise delivery at 24%, 28%, 31%, 35%, 40%, or 50%

3. Airway Management

For acute impairment:

  • Insert nasopharyngeal or oropharyngeal airway before emergency team arrival

  • Monitor patients on high-flow oxygen for need for advanced support:

    • CPAP or BiPAP: Noninvasive positive pressure through tight-fitting mask

    • Intubation: Endotracheal or tracheostomy tube with mechanical ventilation

4. Activity Management

  • Alternate activity with rest periods

  • Allow rest after dyspnea-inducing activities (bathing) before meals or exercise

  • Many COPD patients benefit from increased air circulation using an electric fan

5. Psychosocial Support

  • Encourage patients to express feelings about impaired gas exchange and lifestyle changes


Assessment Data:

History- family history, current meds, lifestyle, chronic disease, environment

Symptom focused- smoking?

Clinical findings: cough, sputum, abnormal breathing patterns, adventitious breath sounds, decreased level of consciousness, shortness of breath, chest pain with breathing

Physical exam- Check TPR, BP, O2 Sat, inspection (breathing effort, color, thorax, extremities), auscultation lungs bilaterally (MUST assess cardiopulmonary systems)

Lab Tests- ABG (arterial blood gas), hemoglobin