Gas enters the pleural cavity causing a state of pneumoperitoneum, called pneumothorax. The disease is highly prevalent and affects human health worldwide, imposing a serious economic burden on society. Without proper and timely management, pneumothorax can be fatal.
Professor Maskell, from the Department of Respiratory Medicine, University of Bristol, UK, and others review the incidence, etiology, diagnosis, treatment strategies, and future directions of pneumothorax. The article was published in a recent issue of BMJ.
Current status of pneumothorax incidence
Between 1991 and 1995, the annual number of visits to the UK for pneumothorax was 24/100,000 for men and 9.8/100,000 for women, and the hospitalization rate was 16.7/100,000 for men and 5.8/100,000 for women. The overall incidence rate refers to the rate of new pneumothorax in a given population over a certain period of time.
According to this calculation, there are 8,000 hospitalizations due to pneumothorax in the UK each year, and the average hospitalization day per person due to pneumothorax is about 1 week, so pneumothorax consumes about 50,000 bed days of medical resources in the whole country, and the economic burden caused by inpatients amounts to £13.65 million, and the annual cost of pneumothorax treatment in the US is as high as $130 million.
Types of pneumothorax
Depending on the cause, pneumothorax can be classified as primary spontaneous pneumothorax, secondary spontaneous pneumothorax, or traumatic (medical or other) pneumothorax. Traumatic pneumothorax is not included in the scope of this review.
Based on the presence or absence of underlying lung disease, spontaneous pneumothorax can be divided into primary and secondary, with significant differences in morbidity, mortality, severity of symptoms (degree of hypoxia during the attack), and management strategies. Although primary pneumothorax occurs mostly in healthy individuals without significant underlying lung disease, most of such patients will have some unspecified abnormal lung lesions.
A small sample of case-control studies found that emphysema-like changes were visible on CT in 81% of 27 non-smoking patients with primary pneumothorax, whereas none of the 10 non-smoking healthy volunteers had such a presentation. Complication rates and mortality rates are higher in secondary pneumothorax than in primary pneumothorax due to the presence of reduced cardiopulmonary reserve function due to underlying lung disease.
Tension pneumothorax is often life-threatening and must be treated urgently. In patients with tension pneumothorax, the rupture of the dirty pleura is a one-way valve, so the air enters the pleural cavity when inhaling and cannot be exhaled when exhaling, resulting in the accumulation of more and more air in the pleural cavity and the continuous increase of internal pressure, which compresses the vena cava and makes the return flow obstructed, and also affects the output function of the heart.
Clinically, high concentration of oxygen is often required, and emergency puncture decompression of the 2nd intercostal space in the midclavicular line is required for further placement of closed drainage of the chest cavity. Because tension pneumothorax affects hemodynamic stability and can be life-threatening, it usually requires urgent management before imaging can confirm the diagnosis. Imaging of tension pneumothorax is characterized by a mediastinal deviation to the healthy side, and in some patients, subluxation of the affected diaphragm and widening of the rib space due to increased intrapleural pressure on the affected side.
Diagnosis
Most patients with pneumothorax can be diagnosed by typical clinical features, while a small proportion of patients with pneumothorax have insignificant symptoms and need to rely on imaging for diagnosis. Most pneumothoraces have an acute onset and often present with sudden onset chest pain, chest tightness and shortness of breath, but some patients are symptom-deficient. Secondary pneumothorax is more obvious or severe than primary pneumothorax due to the presence of underlying lung disease.
Signs of pneumothorax mainly include decreased respiratory motion, percussion drum sounds, and decreased or absent breath sounds on the affected side on auscultation. Hypotension and tachycardia suggest the possible presence of a tension pneumothorax. Most patients can be diagnosed by standard inspiratory-phase chest radiographs. Because chest radiography cannot improve the diagnostic accuracy of pneumothorax, the routine use of chest radiography is not recommended. The typical presentation of a pneumothorax is a thin linear shadow in the shape of an external convex arc, called the pneumothorax line, with increased translucency outside the line and loss of lung texture, and compressed lung tissue inside the line.
The pneumothorax line is often not obvious in supine chest radiographs and requires a large amount of air accumulation to be seen, while the deep sulcus sign may be the only pneumothorax sign in supine position, which shows a deepening of the rib-diaphragm angle due to pleural air accumulation.
CT has high specificity and sensitivity for the diagnosis of pneumothorax, especially for the diagnosis of pneumothorax combined with other complex lung lesions, such as limited pneumothorax formed by adhesions between the remaining lung tissue and the mural pleura, and also simplifies imaging-guided pleural puncture.
CT can differentiate giant pulmonary blisters from pneumothorax. Massive pulmonary blisters are most often seen in patients with severe emphysema. Because of the lack of lung texture in the area where the blisters are located, the imaging may show features similar to a pneumothorax, but the blisters expand peripherally on chest radiographs, whereas a pneumothorax appears as a translucent band on the outside of the chest with the pneumothorax line parallel to the chest wall. It is relatively easy to identify the two on CT, and pneumothorax can be avoided by aspiration in patients with pulmonary herpes.
Etiology
1.Primary spontaneous pneumothorax
Smoking is the most important causative factor of primary pneumothorax, and a retrospective study in Stockholm included 138 patients with primary pneumothorax and 15,000 healthy people from the same region. The results showed that 88% of patients smoked, and compared with nonsmokers, the relative risk ratio for pneumothorax in female smokers (Relative
Risk) was 9 times higher in female smokers and 22 times higher in male smokers compared to non-smokers.
In addition this study showed a significant dose-response relationship between the incidence of pneumothorax and the amount of smoking. Cannabis smoking can also lead to the development of pneumothorax due to the damage to the lung parenchyma caused by the cannabis itself and the increased breath-holding and wah action required to smoke cannabis.
Primary pneumothorax is most often seen in lean and tall men, probably due to the fact that the alveoli in lean and tall men extend farther away from the apex of the lung, resulting in thinner alveolar walls and therefore predisposing to pneumothorax. There are two high incidence age groups for pneumothorax high, primary pneumothorax is more frequent in 15-34 years old, while secondary pneumothorax is mostly seen in people over 50 years old.
2.Secondary spontaneous pneumothorax
Chronic obstructive pulmonary disease (COPD) is the most common cause of secondary pneumothorax, and about 57% of secondary pneumothorax is caused by COPD. In addition, asthma, Pneumocystis jirovecii pneumonia due to HIV, cystic pulmonary fibrosis, lung cancer, tuberculosis, interstitial lung disease, and endometriosis can also lead to pneumothorax.
Pneumothorax caused by intrathoracic endometriosis needs to be taken into account by clinicians. In a prospective study, 25% (8) of 32 female pneumothorax patients treated surgically for sex had pneumothorax episodes associated with menstruation, and 7 of these patients had pathologically confirmed endometriosis of the diaphragm. Therefore, the possibility of intrathoracic endometriosis needs to be considered in female pneumothorax patients and has important implications for subsequent management.
Factors associated with pneumothorax recurrence
1.Primary spontaneous pneumothorax
Smoking is the only proven factor associated with the recurrence of primary pneumothorax. A retrospective study that included 99 patients with primary spontaneous pneumothorax who smoked showed that after 4 years of follow-up, the recurrence rate was 40% in patients who quit smoking and up to 70% in patients who did not quit smoking. In addition, the recurrence rate of male primary pneumothorax patients increased with height, and open-chest or thoracoscopic surgical treatment could reduce the recurrence rate.
2.Secondary spontaneous pneumothorax
Secondary pneumothorax is more prone to recurrence than primary pneumothorax due to the combination of underlying lung disease. In a retrospective study that included 182 patients with pneumothorax, about half of the patients underwent pleural fixation, and the 1-year recurrence rate of primary pneumothorax was 15.8, while the 1-year recurrence rate of secondary pneumothorax was as high as 31.2%.
Surgical treatment such as open chest via thoracoscopy or small axillary incision can significantly reduce the recurrence rate of secondary pneumothorax. The average recurrence rate of pneumothorax during a 30-month follow-up period after surgical treatment of secondary pneumothorax by thoracic surgery was reported to be 3%, while another study showed that the recurrence rate of 86 patients with secondary pneumothorax without surgical treatment was 43% during the same follow-up period.
Treatment goals
The goals of early management of patients with pneumothorax are mainly to exclude tension pneumothorax and to relieve symptoms of dyspnea. Because patients with secondary pneumothorax are more symptomatic and more likely to develop cardiopulmonary insufficiency, whereas patients with primary pneumothorax often lack clinical symptoms and are relatively less likely to develop tension pneumothorax, primary and secondary pneumothorax are managed differently.
Early studies evaluated the treatment of pneumothorax primarily on the basis of improved imaging performance, and the patient’s clinical symptoms were less used to determine the merits of treatment, so early guidelines focused more on measures to reduce pleural air accumulation. The goals of pneumothorax treatment are to exclude tension pneumothorax, reduce complications, reduce pneumothorax-related symptoms, reduce hospitalizations, reduce recurrence rates, and identify patients suitable for surgical treatment in a timely manner.
Treatment methods
Treatment recommendations for pneumothorax vary significantly between guidelines. Treatment methods for pneumothorax include conservative observation and treatment, pleural puncture and aspiration, closed chest drainage, and surgical procedures. The appropriate method of treatment can be selected according to the patient’s symptoms, hemodynamic stability, the size of the pneumothorax, the cause of the pneumothorax, the initial or recurrence, and the effect of initial treatment.
The main differences between the treatment recommendations of different guidelines for primary and secondary pneumothorax are listed below. For example, the evaluation of the size of the pneumothorax varies from guideline to guideline. The British Thoracic Society (BTS) defines the distance between the lateral chest wall and the incisive edge of the lung >2 cm as a massive pneumothorax, whereas the American College of Chest Physicians (ACCP) defines the distance between the apex of the pleura and the lung apex >3 cm as a massive pneumothorax. Compared with ACCP guidelines, the evaluation method of BTS guidelines can better determine the appropriate patients for closed chest drainage in the “safety triangle”.
1.Primary spontaneous pneumothorax
If the pleural cavity rupture is closed, the air accumulation in the pleural cavity will gradually decrease because the pulmonary capillaries can absorb the air in the pleural cavity by themselves. Studies suggest that patients treated conservatively can absorb 2.2% of the volume of gas in the pleural cavity (the area of pneumothorax shown on chest film) by themselves every day. High oxygen concentrations are often given to conservatively treated patients because oxygen absorption accelerates the rate of absorption fourfold.
The indications for pleural puncture aspiration differ between the 2001 ACCP guidelines and the 2010 BTS guidelines. The BTS guidelines recommend pleural puncture aspiration for massive primary pneumothorax (>2 cm), whereas the ACCP guidelines recommend closed chest drainage for such patients, and fine tube puncture drainage only for some patients with massive pneumothorax requiring further surgical treatment.
Since the therapeutic effect of large-bore surgical trocar puncture and drainage is close to that of fine tube puncture and fine tube puncture can reduce patient discomfort, both guidelines do not recommend the use of large-bore surgical trocar drainage for patients with primary pneumothorax, and recommend the use of Seldinger puncture to place a fine tube for drainage (Seldinger puncture uses a puncture needle to penetrate and then feed a guidewire, withdraw the puncture needle and feed the guidewire along The Seldinger puncture method uses the puncture needle to penetrate and then deliver a guide wire, withdraw the puncture needle and deliver a drainage tube into the chest cavity along the guide wire to achieve drainage.)
A prospective randomized trial that included 56 patients with massive primary pneumothorax showed no significant difference in treatment success or recurrence rates between pleural puncture aspiration and closed chest drainage, but pleural puncture aspiration significantly reduced the number of hospital days, and therefore pleural puncture aspiration can be used to treat patients with massive primary pneumothorax.
An early published Cochrane systematic review, although only a single-center randomized controlled study was included, also suggested that both pleurodesis suction and closed chest drainage had similar early effects and outcomes after 1 year of treatment, but the former had a lower rate of patient hospitalization.
2.Secondary spontaneous pneumothorax
Secondary pneumothorax often requires more aggressive management due to the number of complications, significant symptoms and impact on cardiopulmonary function, and both ACCP guidelines and BTS guidelines therefore recommend hospitalization for all patients with secondary pneumothorax. Patients with secondary pneumothorax can be treated with oxygen, but caution is needed in patients who are prone to CO2 retention.
Although almost all patients eventually require closed chest drainage, the BTS guidelines recommend attempting pleurodesis for small amounts of asymptomatic secondary pneumothorax (1-2 cm), while ACCP does not.
Compared to primary pneumothorax, the pleural cavity rupture in secondary pneumothorax is often less likely to close on its own and therefore the average hospital stay is prolonged, and some studies have also demonstrated that the average hospital stay in patients with secondary pneumothorax is more than 10 days longer than in patients with primary pneumothorax.
Pneumothorax patients who have not closed their pleural cavity rupture for 48h must be seen by a thoracic surgeon and given an individualized treatment plan to decide whether to take further surgical treatment based on the risk of recurrence and the risk of surgical complications. Some patients who are not suitable for surgical treatment will require longer conservative treatment or less invasive treatment.
3.Negative pressure suction
If the pleural rupture does not heal after closed chest drainage, the air bubbles continue to escape from the water seal bottle, and the lung reopening is incomplete, the addition of negative pressure suction can be considered. Theoretically, negative pressure suction can promote healing of the ruptured dirty pleura by increasing gas drainage in the pleural cavity and bringing the dirty pleura into contact with the wall pleura. However, a randomized controlled study that included 23 patients with pneumothorax found that negative pressure suction did not increase the rate of pulmonary resuscitation and did not decrease the length of hospital stay.
Therefore, the BTS guidelines do not recommend the routine use of negative pressure suction in patients with pneumothorax, but only in patients with poor pulmonary resuscitation. As part of high-flow low-pressure suction therapy, the negative pressure is usually set at -10 to -20 cm
H2O, high-flow low-pressure suctioning can reduce air leakage and also prevent a large amount of inhaled body gas from entering the chest tube and reducing effective breathing. In addition, it should be noted that as the lung reopening too quickly can lead to reopening pulmonary edema, the use of negative pressure suction should be avoided in the early stage of closed chest drainage.
4.Surgical treatment
Both axillary small incision opening and thoracoscopy have been successfully applied in the treatment of recurrent pneumothorax. In a recent randomized controlled study, a total of 66 patients with primary and secondary pneumothorax were enrolled, and a comparison between axillary mini-incision and thoracoscopic treatment showed no significant difference in the postoperative recurrence rate (2.7% vs. 3%) and pain level. However, although thoracoscopic treatment was more time-consuming than axillary mini-incision open-chest treatment, postoperative patient satisfaction was higher (based on the use of the affected arm after surgery) and the return to normal life was faster.
5.Pleural fixation
Injection of sclerosing agents such as tetracyclines and talcum powder via the chest tube, as well as wiping the wall pleura with gauze or injecting sclerosing agents during surgery, can induce aseptic pleural inflammation and cause adhesion of the dirty layer and wall pleura, thus eliminating the pleural cavity gap, and the method is called pleural fixation. Injection of sclerosing agent via the chest tube is chemical pleural fixation, while via surgery is surgical pleural fixation. To avoid local pain caused by pleural inflammation, pleural fixation requires adequate pleural anesthesia and analgesia.
A randomized controlled study from Taiwan included 214 patients with primary pneumothorax to evaluate the effect of pleural fixation with minocycline, all of whom were treated with or without pleural fixation according to the randomized control principle with chest drainage via a fine tube. The results showed that the 1-year recurrence rate of patients treated with pleural fixation was 29.2%, which was significantly lower than that of the control group (49.1%).
However, pleural fixation has also been questioned to some extent. One study showed a 1-year recurrence rate of 33% in patients without pleural fixation, which was lower than the 49.1% rate in the control group described above, and pleural fixation required a two-day hospital stay. An early small sample randomized controlled study compared the recurrence rate of closed chest drainage alone (control group) with the addition of pleural fixation with tetracycline or talcum powder. After a mean follow-up period of 4.6 years, it was found that the recurrence rate was 8% in the group with pleural fixation compared to 36% in the control group.
Because surgery significantly reduced the postoperative recurrence rate in patients with pneumothorax to only 3%, which is lower than the reported recurrence rate suggested by pleural fixation, the BTS guidelines consider chemical pleural fixation only for patients with persistent air leaks who are not candidates for surgical treatment and do not recommend it as the treatment of choice.
Recommendations for patients
Pneumothorax has a high recurrence rate and therefore patients need to be advised which symptoms indicate a recurrence of pneumothorax and the need for prompt medical attention.
The BTS guidelines recommend that all patients need to be seen in respiratory medicine 2-4 weeks after the initial onset of pneumothorax to review pneumothorax resorption, to check for the presence of underlying lung disease, and for the need for further treatment. Patients may be considered to participate in normal work and activities after their symptoms have resolved. However, strenuous exercise and body collision exercises should be performed only after imaging suggests complete resolution of the pneumothorax.
Patients need to be informed that smoking cessation significantly reduces the recurrence of primary pneumothorax, with a relative risk reduction of approximately 40%, to help them successfully quit smoking. Although smoking cessation is the most effective way to reduce the recurrence of pneumothorax outside of clinical treatment, the success rate of smoking cessation in pneumothorax patients is very low, and studies have shown that more than 80% of patients continue to smoke for more than 1 year after a pneumothorax attack.
1.Diving
Because underwater activities can increase the rate of pneumothorax recurrence, and the pneumothorax volume increases during diving ascent, increasing the risk of tension pneumothorax, the BTS guidelines recommend that diving should be avoided for life for patients not treated by definitive methods (e.g., partial pleurodesis). For professional divers, treatment such as partial pleurectomy is required after a pneumothorax attack before diving can be resumed.
2.Airplane travel
Although airplane travel itself does not increase the risk of pneumothorax, it can aggravate the condition of pneumothorax at high altitude with serious consequences, so patients with pneumothorax without closed chest drainage should avoid airplane travel, and should only travel by airplane after treatment or imaging data suggesting the disappearance of pneumothorax absorption.
For patients with previous pneumothorax, the decision to fly should be based on the likelihood of pneumothorax recurrence and the tolerance level of the pneumothorax attack. The UK Civil Aviation Authority allows pneumothorax patients to fly two weeks after successful treatment with closed chest drainage.
New treatment methods
1.Conservative treatment
The BTS guidelines recommend conservative treatment for small amounts of pneumothorax (distance between the lateral chest wall and the lung margin <2cm) without obvious symptoms of chest tightness and shortness of breath, and for large amounts of pneumothorax with mild symptoms. A randomized controlled study currently underway in Australia compared pulmonary resuscitation, clinical symptoms, complications, and recurrence after 8 weeks of conservative treatment (discharge after clinical observation of stable disease) and standard treatment (pleural puncture and aspiration with closed chest drainage if necessary) in patients with massive pneumothorax treated with different modalities.
The new digital chest closed drainage system can quantify air leakage in pneumothorax patients compared with the traditional water seal bottle. The system is primarily used for the management of long-term pulmonary air leaks after thoracic surgery and also for the early classification of patients with pneumothorax, distinguishing patients prone to persistent air leaks from those with better closed chest drainage.
3.Endobronchial valve
Endobronchial valves are mainly used for non-surgical volume reduction in patients with emphysema and for the treatment of persistent air leaks in patients with pneumothorax. A transbronchoscopic placement of a segmental or subsegmental bronchial placement with a unidirectional valve collapses the distal lung, reducing air entry into the distal lung tissue without affecting gas exhalation.
A previous study reported the use of a unidirectional bronchial valve to treat 40 patients with persistent air leak, 25 of whom had spontaneous pneumothorax. 93% (n=37) of the patients had reduced or disappeared air leak and 48% (n=19) of the patients had complete disappearance of air leak. At present, as a non-surgical treatment method, bronchial flap can be applied to patients with pneumothorax who have poor effect on traditional conservative treatment, but further prospective trials are needed to prove it.
4.Autologous blood transfusion
One study reported the application of intrapleural autologous blood transfusion to treat 44 patients with advanced COPD, secondary pneumothorax, and persistent air leak after 7 days of closed chest drainage, which successfully reduced the air leak rate on the 13th day after treatment. The effect was better in patients with small air leakage.
Intrathoracic autologous blood transfusion also had some complications, with 14% of patients developing hypothermia, but body temperature rapidly returned to normal after antibiotic treatment. This study suggests that intrapleural autologous blood transfusion may be an effective alternative option to chemical pleural fixation for patients at greater risk for surgical treatment.
5. Ambulatory treatment
The Heimlich unidirectional valve can replace the water seal bottle connected to a closed chest drain, providing a convenient daytime outpatient treatment option for patients with pneumothorax, which has good application prospects. In a randomized controlled trial that included 48 patients with primary pneumothorax, all patients were seen in the emergency room and treated with either a Heimlich unidirectional valve or thoracentesis aspiration.
The results showed no significant difference in hospitalization rates between the two, 44% (n=11) and 61% (n=14), respectively. At initial follow-up, 24% (n=6) of Heimilich unidirectional valve patients had complete lung recovery, whereas only 4% (n=1) of patients treated with thoracentesis aspiration had complete lung recovery, and patients tolerated both methods easily. patients treated with Heimilich unidirectional valve had their chest tubes removed in a mean of 3.5 days.
A systematic evaluation (n=1235) assessed the effectiveness of Heimlich unidirectional valve therapy, and although the systematic evaluation included data from a large number of nonrandomized controlled trials and may be subject to some bias, the results showed an overall success rate of 85.8% for Hemilich unidirectional valve therapy, including 77.9% for patients treated on an outpatient basis.
Hemilich unidirectional valve treatment reduced the hospitalization rate and complication rate of patients, with a complication rate of only 1.7%. Further randomized controlled trials with large samples are needed to evaluate the value of the Heimlich unidirectional valve in the treatment of pneumothorax.
Future research directions
1. Is conservative treatment safe and what is its effectiveness and feasibility? This has been the subject of recent ongoing randomized controlled trials, as well as Cochrane systematic reviews.
2.Is Hemilich valve treatment a safe and convenient, ambulatory treatment method?
3, What is the current incidence of pneumothorax?
4.Is it possible to grade patients with primary spontaneous pneumothorax according to the high risk of recurrence?
Key points for non-specialists to know
1.Pneumothorax often presents with sudden onset of chest pain and dyspnea, but a small number of patients may have no obvious symptoms.
2.Most patients can be diagnosed by chest X-ray, but sometimes CT diagnosis is also required.
3.Select a reasonable treatment according to whether the patient is a primary or secondary pneumothorax.
4.Hemodynamic instability suggests the possibility of tension pneumothorax, which requires immediate decompression by second intercostal puncture in the midclavicular line.
5.Smoking cessation can reduce the risk of recurrence of primary spontaneous pneumothorax.
6.Patients with pneumothorax need to undergo definitive treatment or imaging to confirm the pneumothorax absorption before flying, and the British Civil Aviation Authority recommends flying after 2 weeks of complete pneumothorax absorption.
Summary of the main points of the review.
1.Primary spontaneous pneumothorax without underlying lung disease is often associated with smoking.
2.Secondary spontaneous pneumothorax associated with underlying lung disease has more symptoms and more complications, which can easily lead to tension pneumothorax.
3.Tension pneumothorax needs urgent diagnosis and treatment to avoid death.
4.Smoking increases the risk of occurrence and recurrence of pneumothorax, so smoking cessation should be recommended for pneumothorax patients.
5.Patients with recurrent pneumothorax are more likely to have recurrence again, so surgical treatment is recommended