Tension pneumothorax diagnosed on clinical grounds requires immediate treatment by needle decompression and expeditious chest tube thoracostomy before radiographic evaluation. The traditional "gold standard" for diagnosis of pneumothorax continues to be the 6-foot upright posteroanterior chest radiograph, although the sensitivity of this examination is 83 percent.10 A radiolucent line is seen to separate the parietal and visceral pleurae. Pseudo-pneumothorax due to a skinfold, scapular border, or tubing is differentiated from true pneumothorax by looking for vascular markings outside the confines of the radiolucent line and the blending of these lines into the chest wall rather than following the borders of a collapsed lung. Large bullae have been mistaken for pneumothoraces, but bullae and cysts have concave inner margins and rounded edges. Pneumothorax is much more difficult to detect on a supine anteroposterior radiograph. On the anteroposterior view, a deep sulcus sign, representing a deep lateral costophrenic angle, sometimes is a clue to a pneumothorax. 10 Expiratory radiographs by themselves are no more sensitive than inspiratory films and provide inferior evaluation of lung parenchyma. 10 However, comparison of paired inspiratory and expiratory films may be more sensitive than either view alone.11 Chest computed tomography (CT) may be more sensitive than plain radiographs in detection of pneumothorax, but most studies compare supine chest x-ray film (CXR) with chest CT in the setting of trauma. This is useful if the plain film is equivocal. Ultrasound, although portable and easy to perform, is not useful for the diagnosis of pneumothorax, because ultrasound sensitivity is 73 to 95 percent and its specificity is 68 to 91 percent. 12

Spontaneous pneumothorax should be included in the differential diagnosis of acute chest pain or acute deterioration in a patient with COPD. ST-segment and T-wave changes may be mistaken for ischemia. Occasionally, severe bullous COPD may mimic pneumothorax, and careful review of the CXR is needed with confirmatory CT if the patient is stable. A thoracostomy with the chest tube inserted into a bulla mistaken for a pneumothorax results in a large pneumothorax, associated bronchopulmonary fistula, and its complications.3

The size of the pneumothorax may be calculated, and some physicians use size as a guide to therapy. Radiologist "best guess" estimates show substantial interobserver disagreement and lack of reproducibility.13 Using the lung area (x, * y,) to hemithorax area (x2 x y2) ratio to estimate the size of the pneumothorax has a poor correlation ( r = 0.7) with actual size14 (Fig 62-1,). Estimating the amount of collapse by using the ratio of the cube of the pneumothorax diameter (x,) to the cube of the hemithorax diameter (x2) also shows poor correlation ( r = 0.7).14 Rhea and colleagues13 describe a nomogram by using the average intrapleural distance, and

Collins and coworkers15 describe a formula using three intrapleural distances measured in centimeters:

FIG. 62-1. Measurements used in pneumothorax size evaluations.

Whatever method is chosen, the same formula should be used so that sequential calculations are consistent. Chest CT volume measurements represent the current

"gold standard," but the patient's clinical status and not the pneumothorax size should determine treatment options. 1 Treatment

Treatment goals are the elimination of intrapleural air, optimization of pleural healing, and prevention of recurrences. However, there is marked practice variation, and no consensus exists, although attempts have been made.116 Observation, oxygen, catheter aspiration (either single or sequential), tube thoracostomy (either minicatheter or standard chest tube), pleurodesis, video-assisted thorascopy (VAT), and thoracotomy are all options, but only the latter three procedures reduce the risk of future pneumothorax recurrence.

Since 1.25 percent of intrapleural air is reabsorbed each day, stable patients with an asymptomatic primary small spontaneous pneumothorax who have ready access to health care may be observed as outpatients after a 6-h period of observation and a repeat chest radiograph showing no increase in pneumothorax size. Extended outpatient observation is needed because a 25 percent pneumothorax would take about 20 days to resolve. Critics of this treatment plan point to the 23 to 40 percent of patients treated by observation who eventually require tube thoracostomy.1

Observation may be a reasonable approach for those patients with a contraindication to invasive therapy, such as coagulopathy. Concomitant oxygen administration at 3 to 4 L/min increases pleural air resorption three- to fourfold and should always be used in the emergency department. 1

Catheter aspiration is underutilized for treatment of spontaneous pneumothorax. Multiple techniques, equipment, and protocols are described, making a consensus statement difficult. Success rates from 37 to 75 percent are described with the greater success seen in PSP.1 Techniques include simple one-time aspiration with small plastic 16- to 18-gauge intravenous catheters, repeated aspirations through the same catheter, and small-caliber chest tube with aspiration. Minicatheter tube placement uses a specially designed catheter with multiple side ports eliminating the problem of single-lumen obstruction seen with intravenous catheters. The technique involves placing a small catheter either into the second anterior intercostal space in the midclavicular line or laterally at the fourth or fifth intercostal space in the anterior axillary line after local anesthesia and sterile preparation. A three-way stopcock is applied, and a 60 mL syringe is used to aspirate the pleural space until resistance is met and the patient coughs. The stopcock is closed, the tube is secured, and a chest radiograph is obtained to assure reexpansion. Aspiration of more than 4 L suggests continued air leak and failure of simple aspiration. Failure to fully expand warrants another aspiration attempt. If the procedure is successful, patients should be observed for 6 h and, if no recurrence is seen, discharged to close follow-up within 24 h. If the procedure is not successful, a Heimlich valve is attached, with an improved success rate for failed simple aspiration.17

Patients who fail to reexpand even with the Heimlich valve can be placed on low suction or undergo formal large-bore chest tube thoracostomy. These patients require admission, although outpatient chest tube management has been described. Standard chest tube thoracostomy with underwater seal drainage is the most commonly used therapy and remains the standard in many hospitals. Proponents point to a low complication rate and a high success rate of 95 percent. 17 Patients with secondary spontaneous pneumothorax, those with recurrent pneumothorax, and those who fail simple catheter aspiration with Heimlich valve require formal large-bore, >28 French chest tube thoracostomy.17 A proposed treatment algorithm is presented in Fig,,., 6,2,-,2,.

FIG. 62-2. Treatment summary (see the text).

*Symptoms of tension pneumothorax demand immediate decompression.

fSecondary: chronic obstructive pulmonary disease (CoPD), AIDS, cystic fibrosis, asthma, or other known prior lung disease.

Short-term complications of spontaneous pneumothorax include tension pneumothorax, failure to reexpand, persistent air leak, and complications related to the removal of intrapleural air, such as infection, technical errors, and reexpansion pulmonary edema. Reexpansion pulmonary edema is multifactorial, poorly studied, and reports are largely anecdotal.1 Younger patients with larger pneumothoraces rapidly expanded with suction are at most risk. Pulmonary edema generally occurs on the side of the reexpanded lung. Treatment is supportive.

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