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 Emergent Pulmonary
Cardiac
Other Associated with Normal/↑ Respiratory Effort
Other Associated with ↓ Respiratory Effort
Non-Emergent Evaluation Pulmonary edema with small pleural effusions on both sides. Immediate Pulse oximetry (continuous)
ECG — arrhythmia, ischemia, RV strainCXR — pneumothorax, effusion, pulmonary edema, consolidation, widened mediastinumBedside ultrasound — pneumothorax, pleural effusion, B-lines (pulmonary edema), pericardial effusion, RV dilation, cardiac contractilityLabs (guided by clinical suspicion) BNP /NT-proBNP — helps differentiate cardiac from pulmonary dyspneaTroponin — if ACS suspectedD-dimer — if PE suspected and low-to-moderate pretest probabilityCBC — 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 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 Oxygen: Titrate to SpO2 >94% (88-92% if COPD/CO2 retainer); use high-flow nasal cannula, BiPAP , or intubation as neededImmediate life threats:
Common causes:
Airway management:
BiPAP for CHF or COPD exacerbation (avoids intubation in many cases)Intubation if impending respiratory failure, GCS decline, or refractory hypoxia 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
Expected A-a
Interpretation
Normal A-a gradient ≈ (Age/4) + 4 on room airElevated A-a gradient suggests: V/Q mismatch , shunt , or diffusion impairmentNormal A-a gradient + hypoxia suggests: hypoventilation or low FiO₂
References
Formula: A-a = [FiO₂ × (Patm – PH2O )] – (PaCO₂/0.8) – PaO₂Kanber 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
↑ 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
↑ http://ccm.anest.ufl.edu/files/2012/08/BLUELung.pdf Relevance of Lung Ultrasound in the Diagnosis of Acute Respiratory Failure - The BLUE Protocol↑ 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.
↑ 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.
