Eric L Legome, MD,
Chief, Department of Emergency Medicine,
Kings County Hospital Center; Associate Professor, Department
of Emergency Medicine, New York Medical
College
Nothing to disclose.
Francisco Talavera, PharmD, PhD,
Senior Pharmacy Editor,
eMedicine
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John D Halamka, MD, MS,
Associate Professor of Medicine, Harvard
Medical School, Beth Israel Deaconess Medical Center; Chief
Information Officer, CareGroup Healthcare System and Harvard
Medical School; Attending Physician, Division of Emergency
Medicine, Beth Israel Deaconess Medical
Center
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Joseph A Salomone III, MD,
Associate Professor and Attending Staff,
Truman Medical Centers, University of Missouri-Kansas City
School of Medicine; EMS Medical Director, Kansas City,
Missouri
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Chief Editor
Rick Kulkarni, MD,
Assistant Professor of Surgery, Section of
Emergency Medicine, Yale-New Haven Hospital
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Background
A pneumothorax refers to a collection of gas in the pleural space resulting in collapse of the lung on the affected side. A tension pneumothorax is a life-threatening condition caused by air within the pleural space that is under pressure; displacing mediastinal structures and compromising cardiopulmonary function. A traumatic pneumothorax results from blunt or penetrating injury that disrupts the parietal or visceral pleura. Mechanisms include injuries secondary to medical or surgical procedures.
A tension pneumothorax results from any lung parenchymal or bronchial injury that acts as a one-way valve and allows free air to move into an intact pleural space but prevents the free exit of that air. In addition to this mechanism, the positive pressure used with mechanical ventilation therapy can cause air trapping.
As pressure within the intrapleural space increases, the heart and mediastinal structures are pushed to the contralateral side. The mediastinum impinges on and compresses the contralateral lung.
Hypoxia results as the collapsed lung on the affected side and the compressed lung on the contralateral side compromise effective gas exchange. This hypoxia and decreased venous return caused by compression of the relatively thin walls of the atria impair cardiac function. The decrease in cardiac output results in hypotension and, ultimately, in hemodynamic collapse and death to the patient, if untreated.
A study conducted from 1959-1978 involving a US community with an average of 60,000 residents reported an incidence of primary spontaneous pneumothorax of 7.4 cases per 100,000 persons per year for men and 1.2 cases per 100,000 persons per year for women. When these figures are extrapolated, about 8,600 individuals develop primary spontaneous pneumothorax in the United States per year.
Tension pneumothorax is a complication in approximately 1-2% of the cases of idiopathic spontaneous pneumothorax. Until the late 1800s, tuberculosis was a primary cause of pneumothorax development. A 1962 study showed a frequency of pneumothorax of 1.4% in patients with tuberculosis.
Undoubtedly, the incidence of pneumothorax and/or tension pneumothorax in US hospitals has increased as intensive care treatment modalities have become increasingly dependent on positive-pressure ventilation, central venous catheter placement, and other causes that potentially induce iatrogenic pneumothorax.
International
Acupuncture is a traditional Chinese medicine technique used worldwide by alternative medical practitioners. Although generally considered to be a safe form of therapy, acupuncture's most frequently reported serious complication is pneumothorax. In one Japanese report of 55,291 acupuncture treatments, an approximate incidence of 1 pneumothorax in 5000 cases was documented.[1]
Mortality/Morbidity
The clinician should assume that a tension pneumothorax results in hemodynamic instability and death, unless immediately treated.
Sex
The male-to-female ratio is about 6:1 for primary spontaneous pneumothorax development.
In men, the risk of spontaneous pneumothorax is 102 times higher in heavy smokers than in nonsmokers. Spontaneous pneumothorax most frequently occurs in tall, thin men aged 20-40 years.
Catamenial pneumothorax is a rare phenomenon that generally occurs in women aged 30-50 years. It frequently begins 1-3 days after menses onset. Its etiology may be primarily related to associated diaphragmatic defects.
Men undergoing treatment for tension pneumothorax are more likely to have a larger body habitus with wider chest wall. Tension pneumothorax patients with wider chest walls undergoing needle thoracostomy may need a catheter longer than 5 cm to reliably penetrate into the pleural space.
Harcke et al using CT scan analysis of deployed male military personnel determined that, at the second right intercostal space in the midclavicular line, the mean horizontal thickness was 5.36 cm, and that an 8-cm angiocatheter would reach the pleural space in 99% of the male soldiers in this series.[2]
Age
Pneumothorax occurs in 1-2% of all neonates. The incidence of pneumothorax in infants with neonatal respiratory distress syndrome is higher. In one study, 19% of such patients developed a pneumothorax.
The signs and symptoms produced by tension pneumothorax are usually more impressive than those seen with a simple pneumothorax. Unlike the obvious patient presentations oftentimes used in medical training courses to describe a tension pneumothorax, actual case reports include descriptions of the diagnosis of the condition being missed or delayed because of subtle presentations that do not always present with the classically described clinical findings of this condition.
Symptoms and signs of tension pneumothorax may include the following:
Findings at physical examination may include the following:
Respiratory distress (considered a universal finding) or respiratory arrest
Unilaterally decreased or absent lung sounds (a common finding; but decreased air entry may be absent even in an advanced state of the disease)
Adventitious lung sounds (crackles, wheeze; an ipsilateral finding)
Lung sounds transmitted from the nonaffected hemithorax are minimal with auscultation at the midaxillary line
Tachypnea; bradypnea (as a preterminal event)
Hyperresonance of the chest wall on percussion (a rare finding; may be absent even in an advanced state of the disease)
Hyperexpansion of the chest wall
Increasing resistance to providing adequate ventilation assistance
Cyanosis (a rare finding)
Tachycardia (a common finding)
Hypotension (should be considered as an inconsistently present finding; while hypotension is typically considered as a key sign of a tension pneumothorax, studies suggest that hypotension can be delayed until its appearance immediately precedes cardiovascular collapse)
Pulsus paradoxus
Jugular venous distension
Cardiac apical displacement (a rare finding)
Tracheal deviation (an inconsistent finding; while historic emphasis has been placed on tracheal deviation in the setting of tension pneumothorax, tracheal deviation is a relatively late finding caused by midline shift)
Mental status changes, including decreased alertness and/or consciousness (a rare finding)
Abdominal distension (from increased pressure in the thoracic cavity producing caudal deviation of the diaphragm and from secondary pneumoperitoneum produced as air dissects across the diaphragm through the pores of Kohn)
When examining a patient for suspected tension pneumothorax, helpful indications of subtle thoracic size and thoracic mobility differences may be elicited by performing careful visual inspection along the line of the thorax. In a supine patient, by lowering oneself to be in level with the patient.
Tension pneumothorax may be a difficult diagnosis to make and may present with considerable variability in signs presented. Respiratory distress and chest pain are generally accepted as being universally present in tension pneumothorax. Tachycardia and ipsilateral air entry are also common findings.
The development of tension pneumothorax in patients who are ventilated will generally be of faster onset with immediate, progressive arterial and mixed venous oxyhemoglobin saturation decline and immediate decline in cardiac output.
Cardiac arrest associated with asystole or pulseless electrical activity (PEA) may ultimately result.
A wide variety of disease states and circumstances increase the patient's risk of a pneumothorax. If a pneumothorax is complicated by a one-way valve effect, tension pneumothorax may result.
Infants requiring ventilatory assistance and those with meconium aspiration have a particularly high risk for tension pneumothorax. Aspirated meconium may serve as a one-way valve and produce a tension pneumothorax.
Trauma may cause a pneumothorax.
Tension pneumothorax may be the result of blunt trauma with or without associated rib fractures.
Incidents that may cause tension pneumothoraces include unrestrained head-on motor vehicle accidents, falls, and altercations involving laterally directed blows.
Any penetrating wound that produces an abnormal passageway for gas exchange into the pleural spaces and that results in air trapping may produce a tension pneumothorax.
Significant chest injuries carry an estimated 10-50% risk of associated pneumothorax. In about half of these cases, the pneumothorax may be occult; therefore, chest CT should always be performed.
In one study, 12% of patients with asymptomatic chest stab wounds had a delayed pneumothorax or hemothorax.
McPherson et al, analyzing data from the Vietnam Wound Data and Munitions Effectiveness Team study, determined that tension pneumothorax was the cause of death in 3-4% of fatally wounded combat casualties.[3]
Many procedures performed in an intensive care or emergency setting can result in an iatrogenic pneumothorax and tension pneumothorax. Examples of these procedures include incorrect chest tube insertion, mechanical ventilation therapy, central venous cannulation; cardiopulmonary resuscitation; hyperbaric oxygen therapy; needle, transbronchial, or transthoracic lung biopsy; liver biopsy or surgery; and neck surgery.
Secondary or spontaneous tension pneumothorax is possible in many medical conditions.
Pneumothorax is associated with asthma, chronic obstructive pulmonary disease, pneumonia (especially with Staphylococcus, Klebsiella, Pseudomonas, and Pneumocystis species), pertussis, tuberculosis, lung abscess, and cystic fibrosis.
In pulmonary disorders such as asthma and emphysema, hyperexpansion disrupts the alveoli.
Increased pulmonary pressure due to coughing with a bronchial plug of mucus or phlegm bronchial plug may play a role.
Marfan syndrome is associated with an increased risk of pneumothorax.
Individuals may inherit a predisposition for primary spontaneous pneumothorax.
Although rare, spontaneous pneumothorax occurring bilaterally and progressing to tension pneumothorax has been documented.
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.
Translumination: In neonatal patients, one may notice increased transmission of light through the chest on the affected side.
Chest radiography: Historical dogma has included the recommendation that a chest radiograph of tension pneumothorax is a film that should never be taken. In addition, as ultrasonography becomes increasingly available in emergency situations, the already limited role of radiography will be even further minimized. Multiple recent studies have shown bedside ultrasonography to be more accurate than supine chest radiography in detecting and quantifying the presence of pneumothorax, including traumatic pneumothorax. When considering radiography, utilizing a risk-benefit analysis has been suggested, in which the time taken to obtain the radiograph is balanced against the expected clinical course, with decompression preceding chest radiography in ventilated patients who are prone to rapid decompensation.
In a select subset of patients, it may be preferable to radiologically confirm and localize tension pneumothorax before subjecting the patient to potential morbidities arising from decompression. However, this consideration should be limited to a subset of patients who are awake, stable, not in advanced stages of tension and when an immediate chest film can be obtained, with a continuously accompanying practitioner ready to perform urgent decompression should the need arise.
Although the initial chest radiograph may show no evidence of pneumothorax, consider the possibility of delayed traumatic pneumothorax development in any penetrating chest wound. Obtain serial chest radiographs every 6 hours the first day after injury to rule this out. Some authors advocate the acquisition of only one or two serial examinations every 4-6 hours.
Air in the pleural cavity, with contralateral deviation of mediastinal structures, is evidence of a tension pneumothorax. Tension pneumothorax chest radiographic findings may include increased thoracic volume, increased rib separation, heart border ipsilateral flattening, contralateral mediastinal deviation, and hemidiaphragmatic depression.
Pneumothorax chest radiograph findings include ipsilateral lung edge seen parallel to the chest wall, increased lucency, and a deep sulcus sign (deep lateral costophrenic angle).
When evaluating the chest radiograph for pneumothorax, assess rotation. Rotation can obscure a pneumothorax and mimic a mediastinal shift.
In evaluating the radiograph for rotation, compare the symmetry and shape of the clavicles. Also, look at the relative lengths of the ribs in the middle lung fields on each side on the anteroposterior or posteroanterior views. On an image with rotation, the ribs on each side often have unequal lengths.
In a nonloculated pneumothorax, air rises to the nondependent portion of the pleural cavity. Therefore, carefully examine the apices of an upright chest radiograph, and scrutinize the costophrenic and cardiophrenic angles on a supine chest radiograph.
A skin fold can be mistaken for a pneumothorax. Unlike pneumothoraces, skin folds usually continue beyond the chest wall, and lung markings can be seen peripheral to the skin fold line. Viewing the film under the hot lamp may be necessary to discern obscure peripheral lung markings.
In evaluating the chest radiograph, first impressions of pneumothorax size can be misleading. To assist in determining the size of pneumothorax on the radiograph, a 2.5-cm margin of gas peripheral to the collapsing lung corresponds to a pneumothorax of about 30%. Complete collapse of the lung is a 100% pneumothorax.
Chest CT scanning
Collapse of the lung, air in the pleural cavity, and deviation of mediastinal structures are present in tension pneumothorax.
A CT scan is more sensitive than a chest radiograph in the evaluation of small pneumothoraces and pneumomediastinum, although the clinical significance of these occult pneumothoraces is unclear, particularly in the stable nonintubated patient.
A CT scan may allow for further evaluation of underlying pulmonary disease or injury.
Ultrasonography
Use of bedside ultrasonography in the diagnosis of pneumothorax is a relatively recent development. In some trauma centers, pneumothorax detection is included as part of their focused abdominal sonography for trauma (FAST) examination. Knudtson et al, in a prospective analysis of 328 consecutive trauma patients at a level 1 trauma center, obtained a specificity of 99.7% and an accuracy of 99.4%, and concluded that ultrasonography was a reliable modality for the diagnosis of pneumothorax in the injured patient.[4]
Ultrasonographic features used in the diagnosis of pneumothorax include absence of lung sliding (high sensitivity and specificity), absence of comet-tail artifact (high sensitivity, lower specificity), and presence of lung point (high specificity, lower sensitivity). In the absence of pleural disease, visceral pleura moves against parietal pleura while breathing. This movement of the two pleura is detected by the ultrasound as lung sliding, which is a "kind of twinkling synchronized with respiration" seen in real-time and time-motion modes. Comet-tail artifacts are vertical air artifacts that arise from the visceral pleural line (or in the case of parietal emphysema or shotgun pellets may arise above the pleural line).
Lung point, the location that lung-sliding and absent lung-sliding alternately appear, has been shown in multiple studies to allow determination of the size of a pneumothorax. Zhang et al obtained a 79% sensitivity in lung point's ability to determine pneumothorax size.[5]
In one study, ultrasonography had 95.5% sensitivity and 100% specificity for pneumothorax detection compared with chest radiography. In another study, ultrasonography performed on patients with blunt thoracic trauma had 94% sensitivity and 100% specificity for pneumothorax detection compared with spiral CT scanning. A prospective study involving 135 patients with multiple trauma using bedside ultrasonography performed by emergency department clinicians obtained 86% sensitivity and 97% specificity for the detection of pneumothorax.
A prospective study by Brook et al was designed to assess the accuracy of radiology residents in detecting pneumothoraces as part of the extended focused assessment with sonography for trauma (eFAST). Comparing sonographic pneumothorax detection (by the absence of parietal-over-visceral lung sliding with "comet tail" artifacts behind it) with the reference standard of chest CT in 169 consecutive trauma patients (ie, 338 lung fields) demonstrated a sensitivity of 47%, specificity of 99%, positive predictive value of 87%, and negative predictive value of 93%; with none of the small pneumothoraces missed by ultrasound requiring drainage during the hospitalization period. The authors concluded that sonographic pneumothorax detection by these radiology residents was both accurate and efficient in the early detection of clinically important pneumothoraces.[6]
Locate puncture site. The second intercostal space in the midclavicular line on the affected side immediately superior to the rib is most commonly recommended site.
Prepare the puncture site with povidone-iodine (Betadine), alcohol scrubs, or both.
Insert a large-bore Angiocath (14-gauge in an adult, 18- or 20-gauge in an infant) into the desired intercostal space over the top of the rib and perpendicular to the chest wall. Listen for a rush of air.
Remove the needle.
Secure the Angiocath in place, and establish a water seal or flutter valve.
Immediately prepare to insert a chest tube.
Listen for a rush of air on insertion to confirm the diagnosis of tension pneumothorax. Note this finding on the patient's chart. In an area with high ambient noise, the escape of air may not be detected.
Needle thoracostomy requires follow-up placement of a chest tube.
Potential morbidity associated with needle thoracostomy includes pneumothorax (with potential to tension later), cardiac tamponade, hemorrhage (which can be life-threatening), loculated intrapleural hematoma, atelectasis, pneumonia, arterial air embolism (when needle thoracostomy is performed and no tension pneumothorax is present), and pain to the patient.
Tube thoracostomy is performed as follows:
If the patient is hemodynamically stable, consider conscious sedation with careful titration of a short-acting narcotic and benzodiazepine. However, use of a local anesthetic often is adequate.
Place the patient in a 30-60° reverse Trendelenburg position, scrub the site with povidone-iodine (Betadine), alcohol, or both, and anesthetize the site with lidocaine.
Make a 3- to 4-cm incision over the fifth or sixth rib in the midaxillary line.
Use a curved hemostat to puncture the intercostal muscles and parietal pleura immediately superior to the rib border, avoiding damage to the underlying lung. Then, slide a finger over the clamp to maintain the formed tract.
Perform a digital examination to assess the location and to evaluate pulmonary adhesions. Sweep the finger in all directions, and feel for the diaphragm and possible intra-abdominal structures. To avoid losing the desired tract, keep the finger in place until the tube is inserted.
Insert the chest tube along side of the finger, using a clamp on the tube, if desired.
Direct the chest tube posteriorly and inferiorly, and insert it until it is at least 5 cm beyond the last hole of the tube.
Attach the tube to a water seal and vacuum device (eg, Pleur-Evac). Look for respiratory variation and bubbling of air through the water seal. Document the amount of blood or other fluids that may drain.
Suture the site, and secure the tube. A variety of anchoring and closure techniques exist, all of which are probably equivalent. Cover the site with petroleum jelly–impregnated gauze, and apply a suitable dressing.
Follow-up chest radiography is required to confirm tube placement and lung reexpansion.
Complications of tube thoracostomy include death, injury to lung or mediastinum, hemorrhage (usually from intercostal artery injury), neurovascular bundle injury, infection, bronchopleural fistula, and subcutaneous or intraperitoneal tube placement.
Attention to the ABCs is mandatory for all patients with thoracic trauma. Evaluate the patency of the airway and the adequacy of the ventilatory effort. Assess the circulatory status and the integrity of the chest wall.
Failure of the emergency medical service personnel and medical control physician to make a correct diagnosis of tension pneumothorax and to promptly perform needle decompression in the prehospital setting can result in rapid clinical deterioration and cardiac arrest.
However, if an incorrect diagnosis of tension pneumothorax is made in the prehospital setting, the patient's life is endangered by unnecessary invasive procedures. Close cooperation and accurate communication between the emergency department and the emergency medical service personnel is of paramount importance.
To prevent reentry of air into the pleural cavity after needle thoracostomy and decompression in the prehospital setting, a one-way valve should be attached to the distal end of the Angiocath. If available, a Heimlich valve may be used. If a commercially prepared valve is not available, attach a finger condom or the finger of a rubber glove with its tip removed to serve as a makeshift one-way valve device.
Clothing covering a wound that communicates with the chest cavity can play a role in producing a one-way valve effect, allowing air to enter the pleural cavity but hindering its exit. Removing such clothing items from the wound may facilitate decompression of a tension pneumothorax.
A tension pneumothorax is a contraindication to the use of military antishock trousers.
In a preliminary 2006 study from Norway, Busch evaluated the feasibility of using portable ultrasound in an air rescue setting.[7] Concluding that prehospital ultrasonography could provide diagnostic and therapeutic benefit when conducted by a proficient examiner who used goal-directed and time-sensitive protocols. Further study in this area may help to determine the indications and role of prehospital sonography.
For all patients with thoracic injury, immediate and careful attention to the ABCs is vital. Fully assess the patency of the airway and adequacy of the ventilatory effort. Carefully evaluate the cardiovascular system because a tension pneumothorax and a pericardial tamponade can cause similar findings.
If a tension pneumothorax is suspected, immediately administer 100% oxygen, and evaluate the patient for evidence of respiratory compromise, hemodynamic instability, or clinical deterioration. Place large-bore catheters, because hemothorax can be associated with pneumothorax, and the patient may, therefore, require immediate intravenous infusion. Upright positioning, if not inappropriate due to cervical spine or trauma concerns, may be beneficial.
Immediately perform needle thoracostomy or chest tube placement (see Procedures) if the clinical condition warrants such action. Once a needle thoracostomy has been performed, chest tube insertion must follow.
If a hemothorax is associated with the pneumothorax, additional chest tubes may be needed to assist drainage of blood and clots. If the hemopneumothorax requires insertion of a second chest tube, the second tube should be directed inferiorly and should be posterior to the diaphragm.
Chest tubes are attached to a vacuum apparatus that continually removes air from the pleural cavity. The collapsed lung reexpands and heals, thereby preventing continued air leakage. After air leaks have ceased for 24 hours, the vacuum may be decreased and the chest tube removed.
The process of lung reexpansion and healing is not immediate and may be complicated by pulmonary edema; therefore, a chest tube is usually left in place for at least 3 days unless the clinical condition warrants a longer placement.
In general, traumatic pneumothoraces should be treated with insertion of a chest tube, particularly if the patient cannot be closely observed. A subset of patients who have a small (< 15-20%), minimally symptomatic pneumothorax may be admitted, observed closely, and monitored by using serial chest radiographs. In these patients, administration of 100% oxygen promotes resolution by speeding the absorption of gas from the pleural cavity into the pulmonary vasculature.
Hernandez et al noted that ultrasonography is the only radiographic modality allowing patients with nonarrhythmogenic cardiac arrest to continue undergoing resuscitation while searching for easily reversible causes of asystole or PEA.[8] Their proposal is for further investigation into a protocol (using the acronym C.A.U.S.E. for cardiac arrest ultrasound exam) in which cardiac arrest patients, concurrent with resuscitation, receive bedside ultrasonography to look for cardiac tamponade, massive pulmonary embolus, severe hypovolemia, and tension pneumothorax. Their hope is that the eventual adoption of ultrasonography in this setting may allow increased "real-time" diagnostic acumen, decreasing the time required to receive appropriate condition-related therapy.
A tension pneumothorax requires treatment with procedural modalities. Anesthetics and analgesics should be used if the patient is not in distress. Medication may be necessary to treat the pulmonary disorder that caused the pneumothorax. For example, intravenous antibiotics are included in the treatment of a pneumothorax that developed as a sequela of staphylococcal pneumonia. Also, studies suggest that the administration of prophylactic antibiotics after chest tube insertion may reduce the incidence of complications such as emphysema.
If the patient has had repeated episodes of pneumothorax or if the lung remains unexpanded after 5 days with a chest tube in place, surgery may be necessary. The surgeon may use treatment options such as thoracoscopy, electrocautery, laser treatment, resection of blebs or pleura, or open thoracotomy.
In patients with repeated pneumothoraces who are not good candidates for surgery, sclerotherapy with talc or doxycycline may be necessary.
In a preliminary study by Dente et al, ultrasonographic evaluation for pneumothorax was found to be very accurate for the first 24 hours after insertion of a thoracostomy tube. However, its accuracy is not sustained over time. Twenty-four hours after thoracostomy, diagnostic sensitivity of ultrasonography for pneumothorax fell to 55%, and its positive predictive value to 43%. This may be related to intrapleural adhesion formation.[9]
Advise patients to wear safety belts and passive restraint devices while driving.
Encourage smoking cessation.
The incidence of iatrogenic tension pneumothorax may be decreased with prophylactic insertion of a chest tube in patients with a simple pneumothorax that requires positive pressure ventilation.
When subclavian vein cannulation is required, use the supraclavicular approach rather than the infraclavicular approach when possible to help decrease the likelihood of pneumothorax formation.
Prompt recognition and treatment of bronchopulmonary infections decreases the risk of progression to a pneumothorax.
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