Respiratory Concepts and Assessment

Overview

This lecture covers foundational respiratory concepts, respiratory assessment, gas exchange, arterial blood gas (ABG) interpretation, and common respiratory diseases such as pneumonia, pneumothorax, pulmonary embolism, COPD, asthma, and acute respiratory failure.

Respiratory Assessment

• Always assess patients visually first (“across the room” assessment) for breathing effort, skin color, alertness, and positioning.
• Heart and lungs work closely together; dysfunction in one affects the other.
• Assess for shortness of breath, onset, position changes, and history (e.g., COPD, heart failure).

Lung Physiology Concepts

• Lung compliance is how easily lungs expand; reduced in conditions like COPD or fibrosis.
• Airway resistance increases with inflammation, mucus, or bronchoconstriction (e.g., asthma).
• Diffusion is passive gas exchange (O2 in, CO2 out) at the alveolar-capillary membrane.
• VQ mismatch occurs when ventilation or perfusion is impaired, leading to poor gas exchange.

ABG Interpretation

• pH normal: 7.35–7.45; lower = acidic, higher = alkaline.
• PaO2 normal: 80–100 mmHg (arterial O2); SaO2: 93–97% (O2 bound to Hgb).
• PaCO2 normal: 35–45 mmHg (CO2, respiratory component).
• HCO3 normal: 22–26 mEq/L (bicarbonate, metabolic component).
• Use the ROME method: Respiratory Opposite (pH/CO2), Metabolic Equal (pH/HCO3).
• Compensated: pH normal but CO2/HCO3 abnormal; Uncompensated: pH and one value abnormal; Partially compensated: all values abnormal.

Acid-Base Disorders

• Respiratory acidosis: CO2 retention (hypoventilation, COPD, CNS depression); s/s: headache, confusion, lethargy.
• Respiratory alkalosis: Excess CO2 loss (hyperventilation, anxiety); s/s: paresthesia, tetany, muscle cramps.
• Metabolic acidosis: Excess acids or loss of base (DKA, lactic acidosis, diarrhea); s/s: confusion, Kussmaul respirations.
• Metabolic alkalosis: Excess base or acid loss (vomiting, diuretics, antacid use); s/s: muscle twitching, seizures, decreased respiration.

Respiratory Diseases

• Pneumonia: Inflammatory infection of lungs; risk factors include aspiration, intubation; treat with antibiotics and pulmonary hygiene.
• Pneumothorax: Air in pleural space causing lung collapse; s/s: chest pain, dyspnea; tension pneumothorax is life-threatening, needs needle decompression.
• Pulmonary embolism: Blood clot blocking lung perfusion; s/s: sudden dyspnea, tachycardia; treat with anticoagulants (heparin, warfarin, DOACs).
• Core pulmonale: Right-sided heart failure from lung disease or pulmonary hypertension; s/s: JVD, peripheral edema.
• COPD: Chronic airflow limitation, not reversible; cornerstone treatments are bronchodilators and corticosteroids, careful with O2 administration.
• Asthma: Reversible airway inflammation; triggers include allergens, exercise; treat with bronchodilators, steroids, avoid triggers.
• Acute respiratory failure: PaO2 <60 or PaCO2 >50; treat underlying cause, establish airway, provide O2/ventilation.

Key Terms & Definitions

• Lung Compliance — How easily lungs inflate during inspiration.
• Airway Resistance — Resistance encountered by air as it moves through the airways.
• Diffusion — Passive movement of gases across the alveolar-capillary membrane.
• VQ Mismatch — Imbalance between ventilation and perfusion.
• ABG — Arterial Blood Gas, measures pH, PaO2, PaCO2, HCO3 for acid-base status.
• Compensation — Body’s attempt to normalize pH via respiratory or metabolic changes.
• Pneumothorax — Air in pleural space causing lung collapse.
• Pulmonary Embolism — Clot blocking pulmonary artery, impairs perfusion.
• Core Pulmonale — Right-sided heart failure due to lung disease.
• COPD — Chronic Obstructive Pulmonary Disease, progressive, largely irreversible airflow limitation.
• Asthma — Chronic, reversible airway inflammation and hyperreactivity.

Action Items / Next Steps

• Review acid-base interpretation methods (ROME, tic-tac-toe).
• Memorize normal ABG values.
• Study distinguishing features and treatments for pneumonia, pneumothorax, PE, COPD, and asthma.
• Complete any assigned readings on respiratory diseases and acid-base balance.
• Practice ABG interpretation questions and review pneumonia antibiotic timing.