Pneumothorax

 PNEUMOTHORAX

   Definition:

Pneumothorax is defined as the presence of air or gas in the pleural cavity (the potential space between the visceral and parietal pleura of the lung). A medical term that it is used is the collapsed lung, although that term may also refer to atelectasis. The clinical results are dependent on the degree of collapse of the lung on the affected side. If the pneumothorax is significant, it can cause a shift of the mediastinum and compromise hemodynamic stability. Air can enter the intrapleural space through a communication from the chest wall (trauma) or through the lung parenchyma across the visceral pleura.

   The types of pneumothorax:

Primary spontaneous pneumothorax:

Spontaneous pneumothorax is a commonly encountered problem with approaches to treatment that vary from observation to aggressive intervention. Primary spontaneous pneumothorax (PSP) occurs in people without underlying lung disease and in the absence of an inciting event. In other words, air enters into the intrapleural space without preceding trauma and without an underlying history of clinical lung disease. However, many patients whose condition is labeled as primary spontaneous pneumothorax have subclinical lung disease, such as pleural blebs, that can be detected by CT scanning. Patients are typically aged 18-40 years, tall, thin, and, often, are smokers.

Secondary spontaneous pneumothorax:

Secondary spontaneous pneumothorax (SSP) occurs in people with a wide variety of parenchymal lung diseases. These individuals have underlying pulmonary pathology that alters normal lung structure. Air enters the pleural space via distended, damaged, or compromised alveoli. The presentation of these patients may include more serious clinical symptoms and sequelae due to comorbid conditions.

   Signs and symptoms:

Pneumothorax may be entirely asymptomatic, and may be picked up only incidentally on chest films. More commonly it causes a varying combination of chest pain, dyspnea, cough, or other symptoms, depending on the cause and general circumstances of each individual case. In general, symptoms are more severe in secondary than in primary spontaneous pneumothorax, and most patients with secondary spontaneous pneumothorax experience breathlessness that is out of proportion to the size of the pneumothorax. Its extreme form is tension pneumothorax, in which intrapleural pressure exceeds atmospheric pressure throughout the respiratory cycle. The ever-rising pressure in the pleural space compromises respiratory and cardiac function leading to progressive hemodynamic instability which may even result to death if it is not urgently diagnosed and managed.

   Diagnosis:

History and physical examination remain the keys to making the diagnosis of pneumothorax. Examination of patients with this condition may reveal diaphoresis and cyanosis (in the case of tension pneumothorax). Affected patients may also reveal altered mental status changes, including decreased alertness and/or consciousness (a rare finding).

Findings on lung auscultation vary depending on the extent of the pneumothorax. Respiratory findings may include the following:

• Respiratory distress (considered a universal finding) or respiratory arrest.
• Tachypnea (or bradypnea as a preterminal event).
• Asymmetric lung expansion: Mediastinal and tracheal shift to contralateral side.
• Distant or absent breath sounds: Unilaterally decreased/absent lung sounds common, but decreased air entry may be absent even in advanced state of pneumothorax.
• Minimal lung sounds transmitted from unaffected hemithorax with auscultation at midaxillary line.
• Hyperresonance on percussion: Rare finding; may be absent even in an advanced state.
• Decreased tactile fremitus.
• Adventitious lung sounds: Ipsilateral crackles, wheezes.

Cardiovascular findings may include the following:

• Tachycardia: Most common finding.
• Pulsus paradoxus.
• Hypotension: Inconsistently present finding.
• Jugular venous distention.
• Cardiac apical displacement: Rare finding.

Lab and imaging studies:

Although laboratory and imaging studies help determine a diagnosis, tension pneumothorax primarily is a clinical diagnosis based on patient presentation. Suspicion of tension pneumothorax, especially in late stages, mandates treatment and does not require potentially prolonged diagnostic studies.

Arterial blood gas (ABG) studies measure the degrees of acidemia, hypercarbia, and hypoxemia, the occurrence of which depends on the extent of cardiopulmonary compromise at the time of collection. ABG analysis does not replace physical diagnosis, nor should treatment be delayed while awaiting results if symptomatic pneumothorax is suspected. However, ABG analysis may be useful in evaluating hypoxia and hypercarbia and respiratory acidosis.

When pneumothorax is suspected, confirmation by chest radiography affords additional information beyond confirmation, such as the extent of pneumothorax, potential causes, a baseline study from which to go forward, and assistance with the therapeutic plan.

The following radiologic studies may be used to evaluate suspected pneumothorax:

• Chest radiography: Anteroposterior and/or lateral decubitus films.
• Contrast-enhanced esophagography: If emesis/retching is the precipitating event.
• Chest computed tomography scanning: Most reliable imaging study for diagnosis of pneumothorax but notrecommended for routine use in pneumothorax.
• Chest ultrasonography.

   Management:

The range of medical therapeutic options for pneumothorax includes the following:

• Watchful waiting, with or without supplemental oxygen.
• Simple aspiration.
• Tube drainage, with or without medical pleurodesis.

   Surgery:

If the patient has had repeated episodes of pneumothorax or if the lung remains unexpanded after 5 days with a chest tube in place, operative therapy such as the following may be necessary:

• Thoracoscopy: Video-assisted thoracoscopic surgery (VATS).
• Electrocautery: Pleurodesis or sclerotherapy.
• Laser treatment.
• Resection of blebs or pleura.
• Open thoracotomy.

   Pharmacotherapy:

The following medications may be used to aid in the management of patients with pneumothorax:

• Local anesthetics (eg, lidocaine hydrochloride)
• Opioid anesthetics (eg, fentanyl citrate, morphine)
• Benzodiazepines (eg, midazolam, lorazepam)
• Antibiotics (eg, doxycycline, cefazoline)