Dyspnea and Respiratory Distress

Dyspnea: Definition & Pathophysiology - Breathless Beginnings

• Dyspnea: Subjective awareness of uncomfortable breathing.
• Types:
  • Acute: <2-4 weeks; Chronic: >2-4 weeks.
  • Orthopnea: Dyspnea supine.
  • PND (Paroxysmal Nocturnal Dyspnea): Sudden nocturnal dyspnea.
  • Trepopnea: Dyspnea in one lateral decubitus position.
• Pathophysiology:
  • Respiratory center stimulation.
  • Inputs from:
    • Chemoreceptors: Central (medullary; $CO_2$, $H^+$); Peripheral (carotid/aortic bodies; $O_2$, $CO_2$, $H^+$).
    • Mechanoreceptors: Lung (stretch, J-receptors); Chest wall (proprioceptors).
  • Ventilation/Perfusion (V/Q) mismatch.

⭐ Orthopnea is a hallmark of left ventricular failure but can also occur in severe diaphragmatic weakness.

Dyspnea: Etiology - The Usual Suspects

Major Causes:

• Pulmonary: COPD, Asthma, Pneumonia, PE, Pneumothorax, ILD, Pleural effusion
• Cardiac: CHF, ACS, Arrhythmias, Pericardial (tamponade, constrictive), Valvular
• Neuromuscular: Myasthenia, GBS, Diaphragm paralysis
• Hematologic: Severe Anemia
• Metabolic: Acidosis (DKA - Kussmaul)
• Psychogenic: Anxiety, Panic

📌 Acute Dyspnea (4P+A+C):

• Pneumothorax
• Pulmonary Embolism (PE)
• Pneumonia
• Pulmonary Edema (APO)
• Asthma
• Cardiac (ACS/Arrhythmia)

Differentiating Acute Causes:

Dyspnea: Clinical Evaluation - Unmasking Dyspnea

• History: Onset (sudden/gradual), duration, mMRC severity, character, aggravating/relieving factors. Associated: chest pain, cough, fever, wheeze, hemoptysis. PMH, meds, smoking.
• Physical Exam:
  • General: Distress, cyanosis, accessory muscle use.
  • Vitals: RR, SpO2 (< 90% critical), HR, BP.
  • Respiratory: Palpation, percussion, auscultation (wheezes, crackles, rubs, ↓ breath sounds).
  • Cardiac: JVP, S3, murmurs, edema.
  • Signs of DVT.
• Initial Investigations: Pulse oximetry, CXR, ECG, ABG ($P(A-a)O_2$).
• Further: CBC, D-dimer, BNP/NT-proBNP, Troponins, Spirometry/PFTs, Echo, CT chest (CTPA, HRCT).

⭐ Pulsus paradoxus >10 mmHg is a key finding in cardiac tamponade and severe asthma/COPD.

Dyspnea: Management Principles - Breathing Easier

• General Approach: ABCDE (Airway, Breathing, Circulation, Disability, Exposure). Secure airway, administer Oxygen.
  • Target SpO2: 94-98% (general); 88-92% in COPD with hypercapnic failure.

• Non-Invasive Ventilation (NIV - CPAP/BiPAP):

  • Indications: COPD exacerbation (respiratory acidosis), cardiogenic pulmonary edema.
  • Contraindications: Facial trauma, undrained pneumothorax, hemodynamic instability, GCS < 8.

• Life-Threatening Causes: Quick Management

  • Acute Pulmonary Edema: Diuretics, Nitrates, NIV. 📌 LMNOP (Lasix, Morphine, Nitrates, Oxygen, Position).
  • Acute Severe Asthma/COPD: Bronchodilators (SABA, SAMA), Corticosteroids, O2. Consider MgSO4 for asthma.
  • Tension Pneumothorax: Immediate needle decompression → chest tube.
  • Massive Pulmonary Embolism: Anticoagulation; Thrombolysis/embolectomy if unstable.

⭐ In tension pneumothorax, needle thoracostomy should be performed in the 2nd intercostal space, mid-clavicular line, or the 5th intercostal space, anterior axillary line, over the superior border of the rib below to avoid neurovascular bundle.

High‑Yield Points - ⚡ Biggest Takeaways

• Key acute dyspnea causes: PE, pneumothorax, ACS, asthma/COPD exacerbation.
• Key chronic dyspnea causes: COPD, heart failure, ILD, anemia.
• Orthopnea & PND: hallmarks of left ventricular failure (LVF).
• Platypnea-orthodeoxia: linked to hepatopulmonary syndrome, R-L shunts.
• Kussmaul's respiration: signifies severe metabolic acidosis (e.g., DKA).
• Pulsus paradoxus >10 mmHg: points to cardiac tamponade, severe asthma/COPD.
• Acute respiratory distress immediate management: prioritize ABC (Airway, Breathing, Circulation) and administer supplemental oxygen.