Definitive diagnosis of<unk>  rarely made in the ED
ED workup should focus on assessing for reversible pathologies that may be causing or exacerbating symptoms (e.g. infection, PE, pulmonary hypertension, pulmonary edema, concomitant COPD exacerbation, etc.)
VBG/ABG
CBC, BMP
CXR
Consider CT chest (to rule out PE or better characterize lung parenchyma)
+/- Infectious workup, echo as appropriate
Inpatient/outpatient workup may include serologic studies (ANA, rheumatoid factor), PFTs, BAL, lung biopsy
VBG/ABG
CBC, BMP
CXR
Consider CT chest (to rule out PE or better characterize lung parenchyma)
+/- Infectious workup, echo as appropriate
Interstitial lung disease
Interstitial pneumonias 
Pneumoconiosis
Lung malignancy
Atypical pneumonia
Aspiration pneumonia or pneumonitis
Lung transplant complications
Bacterial, viral, or fungal pneumonia