Rosen & Barkin's 5-Minute Emergency Medicine Consult (557 page)

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Asthma

CODES

• 483.0 Pneumonia due to mycoplasma pneumoniae
  
• 486 Pneumonia, organism unspecified
  
• 507.0 Pneumonitis due to inhalation of food or vomitus
  

BASICS

• Presence of free air in the intrapleural space
  
• Spontaneous pneumothorax is due to atraumatic rupture of alveolus, bronchiole, or bleb.
  
• Primary spontaneous pneumothorax (2/3 of incidences):
  
  • No underlying pulmonary pathology present
    
  • Rupture of small subpleural cyst or bleb
    
  • Primarily young, healthy patients (20–40 yr old) with tall, thin body habitus
    
  • Risk factors: Smoking, family history, Marfan syndrome, homocystinuria, thoracic endometriosis
    
• Secondary spontaneous pneumothorax from underlying pulmonary pathology (see Etiology)
  
• Tension pneumothorax:
  
  • Air continues to enter pleural space through bronchoalveolar disruption and becomes trapped via “ball-valve” mechanism.
    
  • Intrapleural pressure increases.
    
  • Venous return to right heart decreases, resulting in decrease in cardiac output.
    
  • Mediastinum shifts toward uninvolved side, mechanically interfering with right atrial filling.
    
  • Ventilation compromise and ventilation/perfusion mismatch result in hypoxemia
    

• Idiopathic
  
• Airway disease:
  
  • Chronic obstructive pulmonary disease (COPD)
    
  • Asthma
    
  • Cystic fibrosis
    
• Infections:
  
  • Necrotizing bacterial pneumonia
    
  • TB
    
  • Fungal pneumonia
    
  • Pneumocystis carinii
    
• Neoplasm
  
• Interstitial lung disease:
  
  • Sarcoidosis
    
  • Idiopathic pulmonary fibrosis
    
  • Lymphangiomyomatosis
    
  • Tuberous sclerosis
    
  • Pneumoconioses
    
• Connective tissue diseases
  
• Pulmonary infarction
  
• Endometriosis
  
• Blunt chest trauma
  
• Penetrating trauma to neck or trunk
  
• Iatrogenic:
  
  • Central line placement
    
  • Other vascular access procedures
    

DIAGNOSIS

• Severity of symptoms is generally proportional to size of the pneumothorax.
  
• Chest pain on the ipsilateral side:
  
  • Sharp, pleuritic pain
    
  • Sudden onset
    
  • Dull ache in delayed presentations
    
• Shortness of breath
  
• Rarely cough, asymptomatic, or generalized malaise
  

• Tachypnea
  
• Heart rate <120 bpm generally seen in simple spontaneous pneumothoraces
  
• Jugular venous distention and tracheal deviation to the contralateral side may be evident in tension pneumothorax.
  
• Cardiac and pulmonary exam:
  
  • Asymmetric decreased breath sounds
    
  • Hyperresonance to percussion of ipsilateral side
    
• Tension pneumothorax:
  
  • Hypotension
    
  • Tachycardia, heart rate >120 bpm
    
  • Diaphoresis
    
  • Cyanosis
    
  • Cardiovascular collapse
    
  • Tracheal deviation
    

• Imaging is mainstay of the workup
  
• DO NOT delay chest decompression if the patient is hemodynamically unstable and there is sufficient clinical evidence of pneumothorax.
  

Arterial blood gas offers little over oxygen saturation.

• Chest radiograph:
  
  • Upright chest radiograph
    
• Patients unable to tolerate upright chest radiograph can be taken in decubitus position with the suspected side up:
  
  • Absence of lung markings distal or peripheral to the visceral pleural white line
    
  • Displacement of mediastinum or anterior junction line
    
  • Deep sulcus sign
    
• On frontal view, larger lateral costodiaphragmatic recess than on opposite side
  
• Diaphragm may be inverted on the side with deep sulcus:
  
  • A rough estimate of pneumothorax size is sufficient to make clinical decisions.
    
• Expiratory film:
  
  • May demonstrate small pneumothorax but has not been shown to increase yield of detection
    
• Chest CT:
  
  • Very sensitive for small pneumothorax but has little practical advantage over chest radiograph
    
• US:
  
  • User experience required
    
  • Rapid at bedside
    
  • Lack of lung sliding and comet-tail artifact signifies pneumothorax.
    
  • M-mode confirms pneumothorax with smooth lines above and below pleural line.
    
  • With experience, sensitivity surpasses chest radiograph
    

ECG:

• Often necessary to rule out cardiac etiologies of chest pain
  
• Nonspecific changes include T-wave inversion, left axis deviation, and decreased R-wave amplitude.
  

• Acute abdominal processes
  
• Aortic aneurysm or dissection
  
• Asthma exacerbation
  
• Chest wall pain
  
• COPD exacerbation
  
• Myocardial infarction
  
• Pericarditis
  
• Pleuritis
  
• Pneumomediastinum
  
• Pulmonary embolus
  

TREATMENT

• Cardiac monitor
  
• Pulse oximetry
  
• Oxygen 100% via nonrebreather face mask
  
• IV access
  
• Suspected tension pneumothorax requires either immediate needle thoracostomy or tube thoracostomy.
  
• Needle thoracostomy:
  
  • Immediate placement indicated in unstable patients with a tension pneumothorax
    
  • 14G–18G angiocatheter in the 2nd intercostal space at midclavicular line or 4th or 5th intercostal space at anterior axillary line
    
  • NOTE: The length of most standard angiocatheters is too short to penetrate the pleural cavity in moderate to large framed patients – longer, purpose-specific catheters may be required
    

• Nontraumatic pneumothorax estimated at <15% collapse and no cardiovascular or respiratory compromise:
  
  • Observe with 100% oxygen support for 4–6 hr.
    
  • Repeat chest radiograph and discharge if unchanged.
    
• Simple aspiration:
  
  • Indications:
    
    • Simple pneumothorax with only 15–30% collapse
      
    • Increase in size of a small pneumothorax during observation
      
  • Placement of aspiration catheter (typically 8F) with 3-way stopcock
    
• Aspirate air until resistance or 3 L of air aspirated.
  
  • If the pneumothorax is no longer visible on 2 subsequent chest radiographs at 4 hr intervals, remove catheter.
    
  • If a final chest radiograph is normal 2 hr after the catheter is removed, the patient may be discharged.
    
  • A 2nd aspiration may be attempted if the pneumothorax does not resolve.
    
• Heimlich valve:
  
  • Indicated when <30% collapse after failure of aspiration
    
  • Attach Heimlich valve to aspiration catheter or chest tube.
    
• Suction:
  
  • Indicated when the Heimlich valve fails
    
  • Attach aspiration catheter to suction at 20 cm H
    ₂
    O.
    
  • Observe in ED for 1 hr.
    
• Tube thoracostomy:
  
  • Indications:
    
    • Suspicion of a tension pneumothorax
      
    • Gunshot wound to the chest
      
    • Clinical evidence of a pneumothorax following blunt chest trauma or penetrating chest trauma
      
    • Presence of a pneumothorax of any size in patient receiving positive-pressure ventilation
      
    • Pneumothorax with >30% collapse
      
    • Most cases of secondary pneumothorax
      
    • Definitive therapy after needle thoracostomy
      
  • Tube size:
    
    • Small-caliber (7–14F) tube for primary spontaneous pneumothoraces
      
    • 20–28F for secondary spontaneous pneumothorax
      
    • 28F when there is detectable pleural fluid or an anticipated need for mechanical ventilation
      
  • Check for tube kinks by fully rotating the inserted tube.
    
  • All side holes in the tube must be within the chest wall to avoid leak.
    
  • Following insertion, the tube should be connected to a water-seal device.
    
  • A Heimlich valve may be used instead of a water-seal device in stable patients without a pleural effusion.
    
  • Re-expansion edema is a rare complication requiring supportive care.
    
• Possible complications:
  
  • Intercostal vessel bleeding
    
  • Inadequate drainage:
    
    • Kinked tube
      
    • Clogged tube
      
    • Communication outside of pleural cavity with leak
      
  • Re-expansion pulmonary edema:
    
    • Treatment with fluid resuscitation