Medical-Surgical Nursing: Oxygenation & Ventilation

Oxygenation and Ventilation

• Aim: Maintain adequate oxygen levels in the blood to support cellular life.
• Primary function: Provide oxygen for tissue metabolism and remove carbon dioxide, a waste product of metabolism.

Regulation of Breathing

• Controlled by the brain structures: medulla oblongata, pons, hypothalamus, and sympathetic nervous system.

Secondary Functions of the Respiratory System

• Facilitates sense of smell and produces speech.
• Maintains acid-base balance and body water levels.
• Helps regulate heat balance during respiration.

Arterial Blood Gas (ABG) Values

• PaO2: Normal range is 96-100%.
• PCO2: Normal range is 35-45 mmHg.
• pH: Normal range is 7.35 - 7.45; indicates acidosis (↓pH, ↑CO2) and alkalosis (↑pH, ↓CO2).
• HCO2: Normal range is 22-26 mEq/L.

Mechanisms of Breathing

• Negative Pressure: Lungs create a vacuum allowing environmental air to enter.
• Positive Pressure: Occurs due to external factors (e.g., wounds) allowing air to enter the lungs.

Physiologic Changes During Inspiration

• Oxygen-rich air travels from the environment through the trachea, bronchi, bronchioles to the alveoli.
• Diaphragm descends, pushing abdominal organs down and forward, enlarging the chest cavity.

Physiologic Changes During Expiration

• Carbon dioxide is expelled from the respiratory system.
• Intercostal muscles and diaphragm relax, returning to the resting position.
• Rib cage assumes a dome-shaped configuration during relaxation.

Upper Respiratory Tract Anatomy

• Extends from the nose to the epiglottis, consisting of:
  • Nose, sinuses, pharynx, larynx (voice box), and epiglottis (prevents aspiration).

Functions of the Upper Respiratory Tract

• Transport gases to/from lower airways and filter/humidify inspired gases.
• Protects lower airways against foreign bodies and microorganisms.

Lower Respiratory Tract Anatomy

• Extends from the base of the neck to the diaphragm, including:
  • Trachea, bronchi, bronchioles, alveoli, lungs, and thoracic cage.

Functions of the Lower Respiratory Tract

• Enables gas exchange by transporting gases in and out of the lungs.
• Promotes mucociliary function to clear mucus and debris.

Upper Airway Disorders: Epistaxis (Nosebleeds)

• Definition: Hemorrhage from the nose.
• Types of Bleeding:
  • Anterior bleeding: Visible blood flow; more common.
  • Posterior bleeding: Suspected if patient frequently swallows blood.

Causes of Epistaxis

• Local Factors:

  • Trauma from blows or injuries.
  • Dryness leading to crust formation—prevented by nasal lubricants and humidifiers.

• Systemic Factors:

  • Conditions such as hypertension, rheumatic heart disease, nasal polyps, cancer, or bleeding disorders (e.g., thrombocytopenia, dengue).