DDx

• Can't miss
• PE, PTX, aortic dissection, STEMI, tamponade
• Consolidation: pulmonary edema, pneumonia, airway bleeding
• Constriction: asthma, COPD, allergic reaction
• Extrinsic: mass, obesity, effusion
• Cardiac: CHF exacerbation, ACS, tamponade
• Etc.: severe anemia, increased ICP, vocal cord dysfunction, severe acidosis (↑ respiratory drive), anxiety (diagnosis of exclusion)

Focus on respiratory, CV exam

• O₂ requirement; work of breathing; can patient speak normally before having to catch breath
• Risk factors for VTE (concern for PE)
• Lung exam (absent breath sound unilaterally = PTX; crackles = PNA/pulmonary edema)
• JVP, peripheral edema (CHF)

• Quick result: ABG, EKG, CXR, bedside US
• Delayed result: CBC, BMP, troponin, chest CT (PE or dissection protocol)
• In appropriate context: BNP, d-dimer, lactate
• BNP not useful in setting of known heart failure
• D-dimer can be elevated in malignancy, trauma, old age, etc. (p. much never useful in hospitalized patient...)
• Lactate OK in initial evaluation of sepsis but is less useful after tissue perfusion has already been restored; clearance is delayed in severe liver dysfunction

Oxygen

• Nasal cannula - max FiO₂ ~ 30%; 5-6 L/min
• Venti mask - max FiO₂ ~ 40-60%
• Non-rebreather - max FiO₂ ~ 80%
• Re-check ABG ~ 2 hrs after improving SaO₂ to > 90%
• If SaO₂ > 90% but still acidotic (pH on ABG < 7.35) - mechanical ventilation (BiPAP or intubation) to decrease work of breathing and improve ventilation/oxygenation
• BiPAP - non-invasive positive pressure ventilation (NIPPV)
• Patient must be awake to cooperate with mask and must be able to protect airway (risk of aspiration with positive pressure)
• Can trial BiPAP on floor, but if unstable or requires prolonged NIPPV, should be in ICU or intubated
• Intubation indicated if pt has decreased LOC/unresponsive, failed NIPPV, severe acidosis (pH < 7.20), anticipated prolonged respiratory failure

Other therapies, depending on clinical situation

• Diuretics if volume overloaded
• Vasodilators (nitroglycerin) if angina
• Bronchodilators (ipratropium, albuterol) if asthma/COPD
• Steroids if asthma/COPD, anaphylaxis
• Abx if COPD, sepsis (consider CAP vs. HCAP)
• Anticoagulation if ACS, suspected PE
• Naloxone/flumazenil if opioid/benzo overdose
• Thoracentesis/chest tube if pleural effusion/empyema