Respiratory Distress/Shortness of breath

DDx of SOB

System DDx Work-up
Acute Asthma *  * (+) Hx, CXR, ABG, FEV1/FVC ratio, FEV1, peak expiratory flow rate (PEFR)
Pneumonia* CXR, ABG, Sputum cultures, Blood cultures.
Pulmonary edema CXR, Exho
Pneumothorax  * CXR: Tracheal shift AWAY from the side of lesion in tension pneumothorax; subcutaneous empyema in pneumomediastinum.
Unilateral absent breath sounds.
Pulmonary Embolism  * Well's Criteria, D-Dimer, V/Q Scan, CT angiogram (if normal Cr.)
Metabolic Acidosis ABG
Acute respiratory distress (ARDS) CXR, ABG
Panic attack ABG: Respiratory Alkalosis
Cardio Aortic Dissection  * -Echo: increased size of ascending aorta, double lumen, Dissection flap.
-CT Chest.
Acute MI*  * EKG, CE, Echo, Stress test
CHF*  * -CXR: Cardiomegaly, BL lower lobe shadowing, pleural effusion, Fluid in horizontal fissure, Kerley B Lines.
-Pro-BNP, Echo.
Valvular obstruction  * EKG, CXR, Echo
Arrhythmia EKG, Telemetry, Holter monitor.
Cardiac tamponad  * EKG, Echo
Pulmonary Anaphylaxis *  * Clinical Dx:
Prolonged expiratory phase, wheeze, tachycardia, hypotension, facial & tongue edema, & cutaneous manifestation (Urticaria, angioedema)
Pneumothorax  * CXR: Tracheal shift AWAY from the side of lesion in tension pneumothorax; subcutaneous empyema in pneumomediastinum.
Unilateral absent breath sounds.
Asthma *  * (+) Hx, CXR, ABG, FEV1/FVC ratio, FEV1, peak expiratory flow rate (PEFR)
Upper airway obstruction   *  
Restrictive lung Disease:
- Interstitial lung disease
- Pleural thickening or effusion
- Respiratory muscle weakness
- Obesity
CXR, CT Chest, Lung Biopsy
Pneumonia* CXR, ABG, Sputum cultures, Blood cultures.
Pulmonary Embolism  * Well's Criteria, D-Dimer, V/Q Scan, CT angiogram (if normal Cr.)
Aspiration (Foreign body)  * CXR: Unilateral atelectasis or hyperlucency
CT Chest: Foreign body in airway
Bronchitis Clinical Dx:
Cough, Prolonged coughing & Dyspnea (especially on exposure to cold air, exercise, or irritants) may occur.
Fever, Cough, inability to take deep breaths ("cough readiness"); lung exam may be normal or reveal rhonchi & wheeze.
Laryngitis Clinical Dx:
May demonstrate hyperemia of oropharaynx; enlarged tonsils with or without exudate
Epiglotitis* Laryngoscopy: swollen epiglottis, aryepiglotic folds, & arytenoid cartilages
Lateral Neck X-Ray: enlarged epiglottis - the "thumb sign"
OSA Polysomnography
Angioedema C4, C1-esterase inhibitor
Metabolic Acidosis ABG
Sepsis Serum Lactic Acid level (repeat if elevate to monitor decreasing levels). Procalcitonin (associated with bacterial sepsis), CBC, CMP, UA w/ c&s, ABG, Amylase, Lipase, Serial cardiac enzymes, PT/INR. Blood culture prior to antibiotic, Sputum culture (BAL), Line/port culture, Wound culture, Surgical Site culture, Legionella Ag, Strep Pneumonia Ag, MRSA swab, Flu swab, H1N1,
Fungal: Cryptococcal Ag (blood and urine)
? Paracentesis, Thoracentesis.
Hematologic Anemia CBC, Stool Occult blood,
Methemoglobinemia, Carbon monoxide poisoning Co-oximetry, Serum carboxyhemoglobin, Serum Lactate (), Serum troponin (), ECG (Tachy, ST elevation).
GI GERD EGD, 24 hr pH monitoring.
Ascites Clinical Dx, Abdominal US.
CXR: Pleural effusion
Neuro Stroke*  * CT Brain, MRI Brain
Tetanus Clinical Dx
Botulism Clinical, Serum C botulinum toxin (+), Stool C botulinum toxin (+).
Amyotrophic lateral sclerosis Clinical, EMG (fasciculation, Nerve conduction study (normal).
Polio LP, Viral culture
Guillain-Barre Syndrome LP (protein, Normal pleocytosis), Nerve conduction study (slow velocity, patchy demyelination)
Myasthenia Gravis Edrophonium (Tensilon) test: Transient improvement in muscle weakness
Serum Ach receptor Ab (+)
EMG: decremental response on repetitive nerve stimulation
Serum tyrosine kinase receptor Ab
Psychiatric Anxiety ABG: Respiratory Alkalosis
 RED * = Urgent Causea

DDx of Dyspnea

Most Common Causes Most Immediately Life-Threatening
Obstructive airway disease:
asthma, chronic obstructive pulmonary disease
Upper airway obstruction:
foreign body, angioedema, hemorrhage
Heart failure/cardiogenic pulmonary edema Tension pneumothorax
Ischemic heart disease:
unstable angina and myocardial infarction
Pulmonary embolism
Pneumonia Neuromuscular weakness:
myasthenia gravis, Guillain-Barré syndrome, botulism
Psychogenic Fat embolism

DDx of Hypercapnia

Depressed central respiratory drive
  Structural central nervous system disease: brainstem lesions
  Drug depression of respiratory center: opioids, sedatives, anesthetics
  Endogenous toxins: tetanus
Thoracic cage disorders
  Morbid obesity
Neuromuscular impairment
  Neuromuscular disease: myasthenia gravis, Guillain-Barré syndrome
  Neuromuscular toxin: organophosphate poisoning, botulism
Intrinsic lung disease associated with increased dead space
  Chronic obstructive pulmonary disease
Upper airway obstruction

DDx of Wheezing

Upper airway (more likely to be stridor, may have element of wheezing)
  Angioedema: allergic, angiotensin-converting enzyme inhibitor, idiopathic
  Foreign body
  Infection: croup, epiglottis, tracheitis
Lower airway
  Transient airway hyperreactivity (usually caused by infection or irritation)
  Chronic obstructive pulmonary disease
  Foreign body
  Cardiogenic pulmonary edema ("cardiac asthma")
  Noncardiogenic pulmonary edema (acute respiratory distress syndrome)
  Pulmonary embolus (rare)

DDx of Cough

Acute Chronic Chronic: Less Common
Upper respiratory infection:
rhinitis, sinusitis, pertussis
Smoking and/or chronic bronchitis Heart failure
Postnasal discharge (upper airway cough syndrome) Lung cancer or other intrathoracic mass
Lower respiratory tract infection:
bronchitis, pneumonia
Asthma: reactive airways disease Emphysema
Occupational and environmental irritants
Allergic reaction Gastroesophageal reflux
Asthma Angiotensin-converting enzyme inhibitor Recurrent aspiration or chronic foreign body
Environmental irritants
Transient airway hyperresponsiveness Angiotensin II receptor blocker Psychiatric
Miscellaneous: cystic fibrosis, interstitial lung disease
Foreign body Postinfectious; pertussis

DDx of Hiccups

Acute: Benign, Self-Limited Chronic: Persistent, Intractable
Gastric distention Central nervous system structural lesions
Alcohol intoxication Vagal or phrenic nerve irritation
Excessive smoking Metabolic: uremia, hyperglycemia
Abrupt change in environmental temperature General anesthesia
Psychogenic Surgical procedures: thoracic, abdominal, prostate and urinary tract, craniotomy
Foreign body in ear touching tympanic membrane (especially hair)


Physical Maneuvers
Remove foreign body from ear
Swallow a teaspoon of sugar
Sip ice water
Drink water quickly


Drug Initial Dose Maintenance Dose
Chlorpromazine 25–50 mg IV, repeat in 2–4 h if needed 25–50 mg PO three to four times a day
Metoclopramide 10 mgs IV or IM 10–20 mg PO three times a day for 10 d
Haloperidol 2–5 mg IM 1–4 mg PO three times a day
Nifedipine 10–20 mg PO 10–20 mg PO three to four times a day
Valproic acid 15 mg/kg PO 15 mg/kg PO three times a day
Baclofen 10 mg PO 10 mg PO three times a day
Gabapentin (for suspected neurologic cause) 100 mg 100 mg PO three times a day


DDx of Cyanosis

Central Cyanosis Peripheral Cyanosis
Hypoxemia Reduced cardiac output
  Decreased fraction of inspired oxygen: high altitude Cold extremities
Maldistribution of blood flow: distributive forms of shock
Ventilation–perfusion mismatch Arterial or venous obstruction
Right-to-left shunt: congenital heart disease, pulmonary arteriovenous fistulas, multiple intrapulmonary shunts  
Abnormal skin pigmentation  
  Heavy metals: iron, gold, silver, lead, arsenic  
  Drugs: phenothiazine, minocycline, amiodarone, chloroquine  
Hemoglobin abnormalities  
  Methemoglobinemia: hereditary, acquired  
  Sulfhemoglobinemia: acquired  
  Carboxyhemoglobinemia (not true cyanosis)  

DDx of Pleural Effusion

Common Less Common
Heart failure Cirrhosis with ascites
  Peritoneal dialysis
  Nephrotic syndrome
Cancer: primary or metastatic Viral, fungal, mycobacterial, or parasitic infection
Bacterial pneumonia with parapneumonic effusion Systemic rheumatologic disorders: systemic lupus erythematosus, rheumatoid arthritis
Pulmonary embolism Uremia, pancreatitis
  Postcardiac surgery or radiotherapy
  Drug-related: amiodarone
Either transudates or exudates 
Transudates after diuretic therapy Pulmonary embolism


Pleural Fluid Diagnostic Tests
Detection of exudative pleural effusion 
Light and colleagues criteria for pleural exudate: one or more of the following present: (modified) 
  Pleural fluid/serum protein ratio >0.5
  Pleural fluid/serum LDH ratio >0.6
  Pleural fluid LDH greater than two thirds of the upper limit for serum LDH
Additional tests on exudative effusions 
Gram stain and culture to detect bacterial infection
Cell count
  Neutrophil predominance: parapneumonic, pulmonary embolism, pancreatitis
  Lymphocytic predominance: cancer, tuberculosis, postcardiac surgery
Glucose: low glucose seen in parapneumonic, malignant, tuberculosis, and rheumatoid arthritis causes of pleural effusions
Cytology for malignancy: highest yield is with adenocarcinoma, much lower with squamous cell, lymphoma, or mesothelioma
Pleural fluid pH: normal pleural fluid pH around 7.64. In parapneumonic effusions, a pleural fluid pH <7.10 predicts development of empyema or persistence and indicates need for thoracostomy tube drainage.
Pleural fluid amylase: elevated in pleural effusions due to pancreatitis or esophageal rupture
Mycobacterial and fungal stains and cultures: as suggested clinically
Tuberculosis pleural fluid markers: polymerase chain reaction for mycobacterial DNA, pleural fluid adenosine deaminase, or pleural fluid interferon



Source: Tintinalli ED 7