Tension pneumothorax

A tension pneumothorax is a life-threatening condition that results from a progressive deterioration and worsening of a simple pneumothorax, associated with the formation of a one-way valve at the point of rupture.^[1]

Upon inspiration, when the pressure inside the chest and pleural cavity lessens as a result of the respiratory muscles increasing chest dimensions, air is sucked in through this one way valve, into the pleural space. Because expiration is a passive process, there is an insignificant amount of pressure created to force the air back out of the pleural cavity. This condition over time results in a gradual accumulation of air to the degree that it begins to put pressure on the mediastinum, compressing the heart and decreasing cardiac output due to the reduced amount of diastolic filling of the ventricles, and also putting pressure against the trachea, deviating it from the midline. Because of the increased thoracic pressure, venous return to the heart is decreased, causing a backup of blood into the venous system, as is evidence by distended jugular veins.^[1]

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Signs and symptoms

• Decreased or absent breath sounds on the affected side
• Jugular venous distension
• Tracheal deviation towards unaffected side^[1]
• Hyperesonance on percussion^[1]
• Unequal chest rise^[1]
• Dyspnea
• Tachypnea^[1]
• Tachycardia^[1]
• Hypotension^[1]
• Hypoxia^[1]
• Pale, cool, clammy skin
• Subcutaneous air
• Cyanosis

Differentiation

A tension pneumothorax is a condition whose signs and symptoms resemble very closely those of a condition called pericardial tamponade. A chest x-ray will distinguish the two. On physical exam, the differentiating factors are:

• Pericardial tamponade
  • Breath sounds: Equal on both sides
  • Trachea: Midline
  • Percussion: Normal resonance
  • Pulse: Affected by breathing, called pulsus paradoxus, or simply paradoxical pulse.
• Tension pneumothorax
  • Breath sounds: Decreased or absent on affected side
  • Trachea: Deviated to unaffected side
  • Percussion: Tympanic
  • Pulse: Normal

Treatment

Initial treatment involves the insertion of a large bore cannula or needle into the second intercostal space on the mid-clavicular line (known as "needle thoracostomy", or more commonly, "needle decompression"), thereby releasing the pressure in the pleural cavity and converting the tension pneumothorax to a simple pneumothorax, which is then treated at the earliest opportunity by inserting a chest tube.^[1]

Tension pneumothorax represents a medical emergency which cannot often accommodate the time spent waiting for the capture and interpretation of a chest radiograph. Consequently, the decision to proceed with needle decompression must be made clinically (i.e., "at the bedside") by observing the acute presentation and reviewing relevant history. There is some debate on the topic of needle thoracostomy. There are risks associated with the process such as lung laceration, especially if no tension pneumothorax condition is present, and that relieved tension may reaccumulate undetected if the needle thoracostomy becomes dislodged. There is also the possibility that the cannula will not reach the pleural cavity due to a thick chest wall, especially in overweight individuals.^[2][3]

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