Acute dyspnea

(Redirigido desde «Tachypnea»)

This page is for adult patients. For pediatric patients, see: acute dyspnea (peds)

Background

  • Dyspnea (shortness of breath) is one of the most common ED chief complaints[1]
  • Can be life-threatening — rapid assessment for immediately dangerous causes is essential
  • The approach should focus on pattern recognition using vital signs, lung exam, CXR, and ECG to quickly narrow the differential
  • Key question: Is this cardiac, pulmonary, or other?
Lobes of the lung with related anatomy.

Clinical Features

Emergent Pattern Recognition

Diagnosis Lungs CXR ECG Treatment Contraindicated
Pulmonary Edema Bilateral rales Interstitial fluid Normal/abnormal R/O AMI, lasix, nitrates, ACEi, BiPAP IVF; ?albuterol; ?Beta-blockers
Bronchoconstriction Wheezes Clear/hyperinflated Normal/pulmonary strain Albuterol, atrovent, steroids, consider anaphylaxis (epi) Beta-blockers; ?aspirin
Pneumonia Focal ronchi/decreased breath sounds Infiltrate/effusion Normal IVF, antibiotics Rate control; diuresis
Pulmonary embolism Clear Clear (most) or Westrmark/Hampton hump Normal/S1Q3T3 Anticoagulate/thrombolytics Rate control
Pneumothorax/Hemothorax Unequal Pneumo/hemo Normal Needle thoracentesis/chest tube Rate control
Dysrythmia Clear/pulmonary edema Clear/pulmonary edema Abnormal Type dependent Albuterol; ?IVF
ACS Clear/pulmonary edema Clear/pulmonary edema Normal/abnormal Aspirin; nitrates, anticoagulation, ?beta-blockers, +/- thrombolytics Albuterol; ?IVF

Differential Diagnosis

Acute dyspnea

Emergent

Non-Emergent

Evaluation

Pulmonary edema with small pleural effusions on both sides.

Immediate

  • Pulse oximetry (continuous)
  • ECG — arrhythmia, ischemia, RV strain
  • CXR — pneumothorax, effusion, pulmonary edema, consolidation, widened mediastinum
  • Bedside ultrasound — pneumothorax, pleural effusion, B-lines (pulmonary edema), pericardial effusion, RV dilation, cardiac contractility

Labs (guided by clinical suspicion)

  • BNP/NT-proBNP — helps differentiate cardiac from pulmonary dyspnea
  • Troponin — if ACS suspected
  • D-dimer — if PE suspected and low-to-moderate pretest probability
  • CBC — anemia, infection
  • BMP — metabolic acidosis (consider DKA, sepsis, toxic ingestion)
  • VBG/ABG — acid-base status, pCO2, carboxyhemoglobin, methemoglobin
  • Lactate — if sepsis or shock suspected

Advanced Imaging

  • CT-PA — if pulmonary embolism suspected
  • CT chest — if parenchymal disease, mass, or empyema suspected
  • CT angiography — if aortic dissection suspected


Bedside Lung Ultrasound in Emergency (BLUE) Protocol[2]

Algorithm for the Use of Ultrasound in the Evaluation of Dyspnea
  • Landmark study by a French intensivist that described various profiles of specific pulmonary disease found on US[3]
  • Ultrasound approaches include anterior zones and PLAPS (posterior or lateral alveolar and/or pleural syndrome) point, which is located at the posterior axillary line similar to FAST view
  • Predominant A lines anteriorly + lung sliding = Asthma/COPD
  • Multiple predominant B lines anteriorly + lung sliding = Pulmonary Edema
  • Predominant A lines anteriorly + lung sliding + positive DVT = PE
  • Absent anterior lung sliding + anterior A lines + positive lung point = Pneumothorax (PTX)
  • PLAPS findings +/- A or B lines +/- abolished lung sliding = Pneumonia
    • PLAPS describes changes at the PLAPS point, usually related to consolidations and pleural effusions[4]
    • Consolidations may include lung hepatization, shred sign, air bronchograms
      • Note that mirroring (normal) may appear similar to hepatization, but mirroring only shows in specific spots due to specific echogenic windows
    • Pleural effusions are visualized as anechoic/hypoechoic areas with possible spine sign or floating lung sign (sinusoid sign on M-mode)
  • A suggested BLUE protocol guides diagnosis of dyspnea; this should be modified as needed based on clinical presentation
    • Check lung sliding in anterior lung fields ---> check for A and B lines ---> check for PLAPS findings

Management

Disposition

  • Admit to ICU:
    • Intubated or on BiPAP with impending respiratory failure
    • Massive or submassive PE
    • Hemodynamic instability
    • Severe asthma/COPD unresponsive to initial treatment
  • Admit to floor:
    • CHF exacerbation requiring IV diuresis
    • Pneumonia with hypoxia or significant comorbidities
    • New PE on anticoagulation
  • Discharge:
    • Asthma/COPD exacerbation with adequate response to ED treatment and baseline PEF restored
    • Mild CHF exacerbation with adequate response to diuresis and stable vitals
    • Low-risk PE (if outpatient anticoagulation pathway available)
    • Anxiety-related dyspnea after exclusion of organic causes

Calculators

A-a O₂ Gradient

Alveolar-arterial (A-a) O₂ Gradient
Parameter Value
Age (years)
FiO₂ (%)
PaCO₂ (mmHg)
PaO₂ (mmHg)
A-a Gradient mmHg
Expected A-a mmHg (age-adjusted normal)
Interpretation
  • Normal A-a gradient ≈ (Age/4) + 4 on room air
  • Elevated A-a gradient suggests: V/Q mismatch, shunt, or diffusion impairment
  • Normal A-a gradient + hypoxia suggests: hypoventilation or low FiO₂
References
  • Formula: A-a = [FiO₂ × (Patm – PH2O)] – (PaCO₂/0.8) – PaO₂
  • Kanber GJ, et al. The alveolar-arterial oxygen gradient in young and elderly men during air and oxygen breathing. Am Rev Respir Dis. 1968;97(3):376-381. PMID 5637791.

See Also

References

  1. ↑ Mueller C, et al. Use of B-type natriuretic peptide in the evaluation and management of acute dyspnea. N Engl J Med. 2004;350(7):647-654. PMID 14960741
  2. ↑ http://ccm.anest.ufl.edu/files/2012/08/BLUELung.pdf Relevance of Lung Ultrasound in the Diagnosis of Acute Respiratory Failure - The BLUE Protocol
  3. ↑ Lichtenstein DA, Mezière GA. Relevance of lung ultrasound in the diagnosis of acute respiratory failure: the BLUE protocol. Chest. 2008 Jul;134(1):117-25. doi: 10.1378/chest.07-2800. Epub 2008 Apr 10. Erratum in: Chest. 2013 Aug;144(2):721. PMID: 18403664; PMCID: PMC3734893.
  4. ↑ Lichtenstein DA. Lung ultrasound in the critically ill. Ann Intensive Care. 2014 Jan 9;4(1):1. doi: 10.1186/2110-5820-4-1. PMID: 24401163; PMCID: PMC3895677.
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