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  • Dyspnea: Subjective experience of breathing discomfort, must be self-reported

  • Respiratory distress: Presence of increased work of breathing, which signals approaching respiratory collapse; physical exam may reveal high respiratory rate, use of accessory muscles, evidence of acute obstruction (e.g., wheezing, stridor), and/or cyanosis

  • Hypoxia: Insufficient delivery of oxygen to tissues/organs, which can result from anemia, hypoxemia, circulatory dysfunction, hypermetabolic states, and/or the presence of histotoxins (e.g., cyanide)

  • Hypoxemia: Insufficient oxygenation of arterial blood; directly measured by blood gas


  • Pathophysiology: 1) Increased effort in setting of respiratory muscle fatigue. 2) Acute hypercapnia > acute hypoxemia. 3) Bronchoconstriction. 4) Dynamic airway compression. 5) Afferent mismatch.

  • Differential diagnosis: Etiologies may be pulmonary, cardiac, metabolic, hematologic, acid–base, and psychiatric; the dyspnea pyramid (Figure 2.10) can be helpful for remembering how common each etiology is for dyspnea (i.e., base of pyramid most common, top of pyramid least common)

  • Physical exam:

    • - Vital signs: HR, RR, SpO2

    • - General: Distress, mental status

    • - HEENT: Airway exam

    • - Volume: JVD, rales, edema, S3 (→ CHF)

    • - Pulm: Wheeze, pursed lips, increased I/E, stridor (→ COPD/asthma, anaphylaxis, angioedema), rhonchi/crackles, egophony (→ PNA), distant/absent breath sounds, dull to percussion (→ pleural effusion), absent breath sounds, resonant to percussion (→ pneumothorax)

    • - CV: Distant heart sounds, pulsus paradoxus (→ pericardial effusion, tamponade), palpitations/irregular rhythm

    • - Neuro: GCS <8 (→ early intubation), strength/sensation

    • - Abd: Ascites or distention

  • Differential diagnosis by system: (Figure 2.10)

    • - Cardiac: ACS, CHF, cardiomyopathy, valvular disease, arrhythmia, tamponade

    • - Pulm: Infection (pneumonia), PE, pneumothorax, asthma, COPD, ARDS, aspiration, hemorrhage, effusion, tumor

    • - HEENT: Angioedema, anaphylaxis, pharyngeal infection, foreign body, neck trauma

    • - Chest wall: Rib fracture, flail chest

    • - Neuro: CVA, neuromuscular disease (myasthenia gravis, muscular dystrophy)

    • - Toxic/metabolic: CO poisoning, methemoglobinemia, sepsis, DKA, anemia, narcotic overdose

    • - Psych: Anxiety

    • - Other: Pneumomediastinum, ascites, obesity

  • Workup: CBC with differential, BMP, LFTs (evaluate for congestion), CXR, ECG, A/VBG; additional testing to consider: BNP, troponin, cardiac/IVC POCUS, TTE; pulmonary POCUS; CT chest/CT-PE/HRCT chest

  • Management: If “respiratory distress” is present, see next section; otherwise, treat suspected underlying cause


The dyspnea pyramid. The etiologies of dyspnea are listed here, with more common causes of dyspnea on the bottom of the pyramid and less common causes at the top.


  • Ask for help: Call your team and consider rapid response

  • Confirm code status

  • Provide respiratory support: Oxygen via nasal canula, non-rebreather, or high-flow nasal canula. Consider non-invasive positive pressure ventilation (NIPPV) if not contraindicated or intubation if needed.

  • Perform physical exam: See physical exam under dyspnea above

  • First-pass diagnostics: STAT ABG, CBC with differential, CXR, ECG. Consider BMP, BNP, troponin, VBG with lactate, cardiac and/or pulmonary POCUS, CT chest/CTPE (based on stability)

  • Differential diagnosis: Consider differential diagnosis based on patient characteristics (Table ...

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