Dyspnea

Basics

Description

  • Subjective breathing discomfort from mild discomfort to feelings of suffocation
  • Caused by oxygen supply–demand mismatch and CO2 elimination failure
  • Disruption of any of the complex mechanisms that control breathing can impair ventilation, perfusion, metabolic function, or CNS drive:
    • Brainstem and cortical centers regulate automatic and voluntary breathing, integrating sensory inputs
    • Central CO2 and peripheral O2 receptors, along with mechanoreceptors, detect imbalances and trigger responses
    • Respiratory muscles respond to neural drive, with mismatch between effort and ventilation causing dyspnea
  • Clinical subcategories of dyspnea:
    • Acute (<48 hr)
    • Chronic (>4 wk)
    • Exertional (Heart failure, asthma)
    • Orthopnea (CHF, diaphragm paralysis)
    • Trepopnea (dyspnea in lateral decubitus, unilateral lung disease, pleural effusion)
    • Platypnea (worse when upright, hepatopulmonary syndrome, right-to-left shunt)
    • Paroxysmal nocturnal dyspnea (Classic for heart failure)
    • Nocturnal dyspnea with snoring or apnea
  • 1–7.5% of ED visits
  • Elderly patients account for 18.5% of presentations

Etiology

  • Upper airway obstruction:
    • Epiglottitis
    • Laryngeal obstruction
    • Tracheitis or tracheobronchitis
    • Angioedema
    • Foreign body
  • Lower airway obstruction:
    • Asthma
    • COPD
    • Bronchitis
  • Alveolar disease:
    • Pneumonia
    • Pulmonary edema
    • ARDS
    • Metastatic disease
  • Pleural disease:
    • Pneumothorax
    • Pleural effusion
  • Pulmonary vascular disease:
    • Pulmonary embolus
    • Pulmonary hypertension
  • Respiratory muscle disease:
    • Neuromuscular disorders
    • Diaphragm paralysis
  • Cardiovascular causes:
    • Congestive heart failure
    • Acute coronary syndrome
    • Cardiac tamponade
    • Constrictive pericarditis
    • Thyroid storm:
      • Due to high-output heart failure, pulmonary edema, or respiratory muscle fatigue
    • Arrhythmia
    • Intracardiac shunt
    • Myxoma
    • Valvular disease
  • Metabolic acidosis:
    • Sepsis
    • Ketoacidosis (diabetic, alcoholic, starvation)
    • Renal failure (volume overload, uremia)
    • Profound thiamine deficiency
  • Toxic:
    • Methemoglobinemia
    • Salicylate poisoning
    • Cellular asphyxiants:
      • Carbon monoxide
      • Cyanide
      • Hydrogen sulfide
      • Sodium azide
    • Toxic alcohols
  • Abdominal compression:
    • Ascites
    • Pregnancy
    • Massive obesity
  • Psychogenic:
    • Anxiety and panic attacks
    • Hyperventilation
    • Vocal cord dysfunction
  • Other:
    • Altitude
    • Anaphylaxis
    • Anemia

Geriatric Considerations

  • Elderly dyspnea presents atypically with weakness, confusion, or inactivity
  • Elderly dyspnea patients need more hospitalization and longer stays
  • Often multifactorial, with overlapping cardiac, pulmonary, metabolic, and functional causes, compounded by frailty and multiple comorbidities, making diagnosis and management challenging

Pediatric Considerations

  • Common differential diagnosis for age <2 yr:
    • Asthma
    • Croup
    • Congenital anomalies of the airway
    • Congenital heart disease
    • Foreign-body aspiration
    • Nasopharyngeal obstruction
    • Shock

Pregnancy Considerations

  • Pregnant women have decreased lung capacity and a propensity for anemia
  • While supine, the gravid uterus can compress the IVC, leading to dyspnea and hypotension
  • There is an increased risk for PE throughout and shortly after pregnancy, as well as for amniotic fluid emboli in the peripartum and postpartum periods

There's more to see -- the rest of this topic is available only to subscribers.