Dyspnea

Basics

Description

Inability to breathe comfortably
  • Describes a symptom of many possible underlying diseases
  • May or may not correlate with signs of increased work of breathing
  • Usually an unconscious activity, dyspnea is the subjective sensation of breathing, from mild discomfort to feelings of suffocation
  • Accounts for 3.5% of ED visits
  • Caused by difficulties in maintaining homeostasis with respect to gas exchange and acid–base status
  • Can reflect an impairment in ventilation, perfusion, metabolic function, or CNS drive
  • Mechanisms that control breathing:
    • Control centers:
      • Brainstem and cerebral cortex affect both automatic and voluntary control of breathing
    • Chemo, stretch, and irritant sensors:
      • CO2 receptors located centrally and PO2 receptors located peripherally
      • Mechanoreceptors lie in respiratory muscles and respond to stretch
      • Intrapulmonary mechanoreceptors respond to chemical irritation, engorgement, and stretch
    • Effectors of respiratory center output are in the respiratory muscles and respond to central stimulation to move air in and out of the thoracic cavity
    • Motor–sensory control of the diaphragm and muscles of respiration are controlled by C3–C8 nerves and T1–T12 nerves
  • Derangements of any of these neurosensory pathways produces dyspnea:
    • Many etiologies for the sensation of dyspnea are due to the complex nature of mechanisms that control breathing

Etiology

  • Upper airway:
    • Epiglottitis
    • Laryngeal obstruction
    • Tracheitis or tracheobronchitis
    • Angioedema
  • Pulmonary:
    • Airway mass
    • Asthma
    • Bronchitis
    • Chest wall trauma
    • CHF
    • Drug-induced conditions (e.g., crack lung, aspirin overdose)
    • Effusion
    • Emphysema
    • Lung cancer
    • Metastatic disease
    • Pneumonia
    • Pneumothorax
    • Pulmonary embolism (PE)
    • Pulmonary HTN
    • Restrictive lung disease
  • Cardiovascular:
    • Arrhythmia
    • Coronary artery disease
    • Intracardiac shunt
    • Left ventricular failure
    • Myxoma
    • Pericardial disease
    • Valvular disease
  • Neuromuscular:
    • CNS disorders
    • Myopathy and neuropathy
    • Phrenic nerve and diaphragmatic disorders
    • Spinal cord disorders
    • Head and cervical spine trauma
    • Systemic neuromuscular disorders
  • 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:
    • Hyperventilation
    • Anxiety
  • Other:
    • Altitude
    • Anaphylaxis
    • Anemia

Geriatric Considerations
  • Most common diagnoses in elderly patients presenting to the ED with dyspnea:
    • Decompensated heart failure
    • Infection (pneumonia, UTI)
    • COPD/asthma
    • PE


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

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