Pneumothorax

A primary spontaneous pneumothorax (PSP) tends to occur in a young adult without underlying lung problems, and usually causes limited symptoms. Chest pain and sometimes mild breathlessness are the usual predominant presenting features. In newborns tachypnea, cyanosis and grunting are the most common presenting symptoms. People who are affected by a PSP are often unaware of the potential danger and may wait several days before seeking medical attention. PSPs more commonly occur during changes in atmospheric pressure, explaining to some extent why episodes of pneumothorax may happen in clusters. This causes a type of circulatory shock, called obstructive shock. Tension pneumothorax tends to occur in clinical situations such as ventilation, resuscitation, trauma, or in people with lung disease. It is a medical emergency and may require immediate treatment without further investigations (see Treatment section). The most common findings in people with tension pneumothorax are chest pain and respiratory distress, often with an increased heart rate (tachycardia) and rapid breathing (tachypnea) in the initial stages. Other findings may include quieter breath sounds on one side of the chest, low oxygen levels and blood pressure, and displacement of the trachea away from the affected side. Rarely, there may be cyanosis, altered level of consciousness, a hyperresonant percussion note on examination of the affected side with reduced expansion and decreased movement, pain in the epigastrium (upper abdomen), displacement of the apex beat (heart impulse), and resonant sound when tapping the sternum. Tension pneumothorax may also occur in someone who is receiving mechanical ventilation, in which case it may be difficult to spot as the person is typically receiving sedation; it is often noted because of a sudden deterioration in condition. Recent studies have shown that the development of tension features may not always be as rapid as previously thought. Deviation of the trachea to one side and the presence of raised jugular venous pressure (distended neck veins) are not reliable as clinical signs. ==Cause==

Primary spontaneous Spontaneous pneumothoraces are divided into two types: primary, which occurs in the absence of known lung disease, and secondary, which occurs in someone with underlying lung disease. The cause of primary spontaneous pneumothorax is unknown, but established risk factors include being of the male sex, smoking, family history of pneumothorax, and a tall, thin build. Smoking either cannabis or tobacco increases the risk. 11.5% of people with a spontaneous pneumothorax have a family member who has previously experienced a pneumothorax. Several hereditary conditions – Marfan syndrome, homocystinuria, Ehlers–Danlos syndromes, alpha 1-antitrypsin deficiency (which leads to emphysema), and Birt–Hogg–Dubé syndrome – have all been linked to familial pneumothorax. Generally, these conditions cause other signs and symptoms as well, and pneumothorax is not usually the primary finding. Traumatic A traumatic pneumothorax may result from either blunt trauma or penetrating injury to the chest wall. Traumatic pneumothorax may also be observed in those exposed to blasts, even when there is no apparent injury to the chest. Pneumothorax was reported as an adverse event caused by misplaced nasogastric feeding tubes. Avanos Medical's feeding tube placement system, the CORTRAK* 2 EAS, was recalled in May 2022 by the FDA due to adverse events reported, including pneumothorax, leading to 60 injuries and 23 people dying as communicated by the FDA. Medical procedures, such as inserting a central venous catheter into one of the chest veins or taking biopsy samples from lung tissue, may also lead to pneumothorax. The administration of positive pressure ventilation, either mechanical ventilation or non-invasive ventilation, can result in barotrauma (pressure-related injury) leading to a pneumothorax. An additional problem in these cases is that those with other features of decompression sickness are typically treated in a diving chamber with hyperbaric therapy; this can lead to a small pneumothorax rapidly enlarging and causing features of tension. The goal of treatment was to deprive the oxygen dependent mycobacterium of the resources it requires to multiply and spread. However, the same complications that arise with other mechanisms may still apply, leading to questions of risk vs. benefit. ==Mechanism==

The thoracic cavity is the space inside the chest that contains the lungs, heart, and numerous major blood vessels. On each side of the cavity, a pleural membrane covers the surface of lung (visceral pleura) and also lines the inside of the chest wall (parietal pleura). Normally, the two layers are separated by a small amount of lubricating serous fluid. The lungs are fully inflated within the cavity because the pressure inside the airways (intrapulmonary pressure) is higher than the pressure inside the pleural space (intrapleural pressure). Despite the low pressure in the pleural space, air does not enter it because there are no natural connections to air-containing passages, and the pressure of gases in the bloodstream is too low for them to be forced into the pleural space. Chest-wall defects are usually evident in cases of injury to the chest wall, such as stab or bullet wounds ("open pneumothorax"). In secondary spontaneous pneumothoraces, vulnerabilities in the lung tissue are caused by a variety of disease processes, particularly by rupturing of bullae (large air-containing lesions) in cases of severe emphysema. Areas of necrosis (tissue death) may precipitate episodes of pneumothorax, although the exact mechanism is unclear. Smoking may additionally lead to inflammation and obstruction of small airways, which account for the markedly increased risk of PSPs in smokers. Once air has stopped entering the pleural cavity, it is gradually reabsorbed. Tension pneumothorax occurs when the opening that allows air to enter the pleural space functions as a one-way valve, allowing more air to enter with every breath but none to escape. The body compensates by increasing the respiratory rate and tidal volume (size of each breath), worsening the problem. Unless corrected, hypoxia (decreased oxygen levels) and respiratory arrest eventually follow. ==Diagnosis==

The symptoms of pneumothorax can be vague and inconclusive, especially in those with a small PSP; confirmation with medical imaging is usually required. It is not believed that routinely taking images during expiration would confer any benefit. Still, they may be useful in the detection of a pneumothorax when clinical suspicion is high but yet an inspiratory radiograph appears normal. Also, if the PA X-ray does not show a pneumothorax but there is a strong suspicion of one, lateral X-rays (with beams projecting from the side) may be performed, but this is not routine practice. The latter method may overestimate the size of a pneumothorax if it is located mainly at the apex, which is a common occurrence. Ultrasound may be more sensitive than chest X-rays in the identification of pneumothorax after blunt trauma to the chest. Ultrasound may also provide a rapid diagnosis in other emergency situations, and allow the quantification of the size of the pneumothorax. Several particular features on ultrasonography of the chest can be used to confirm or exclude the diagnosis. File:UOTW 6 - Ultrasound of the Week 1.webm|Ultrasound showing a pneumothorax File:UOTW 62 - Ultrasound of the Week 1.webm|Ultrasound showing a false lung point and not a pneumothorax ==Treatment==

The treatment of pneumothorax depends on a number of factors and may vary from discharge with early follow-up to immediate needle decompression or insertion of a chest tube. Treatment is determined by the severity of symptoms and indicators of acute illness, the presence of underlying lung disease, the estimated size of the pneumothorax on X-ray, and – in some instances – on the personal preference of the person involved. Any open chest wound should be covered with an airtight seal, as it carries a high risk of leading to tension pneumothorax. Ideally, a dressing called the "Asherman seal" should be utilized, as it appears to be more effective than a standard "three-sided" dressing. The Asherman seal is a specially designed device that adheres to the chest wall and, through a valve-like mechanism, allows air to escape but not to enter the chest. Tension pneumothorax is usually treated with urgent needle decompression. This may be required before transport to the hospital, and can be performed by an emergency medical technician or other trained professional. If tension pneumothorax leads to cardiac arrest, needle decompression or simple thoracostomy is performed as part of resuscitation as it may restore cardiac output. Conservative Small spontaneous pneumothoraces do not always require treatment, as they are unlikely to proceed to respiratory failure or tension pneumothorax, and generally resolve spontaneously. This approach is most appropriate if the estimated size of the pneumothorax is small (defined as 50%), or in a PSP associated with breathlessness, some guidelines recommend that reducing the size by aspiration is equally effective as the insertion of a chest tube. This involves the administration of local anesthetic and inserting a needle connected to a three-way tap; up to 2.5 liters of air (in adults) are removed. If there has been significant reduction in the size of the pneumothorax on subsequent X-ray, the remainder of the treatment can be conservative. This approach has been shown to be effective in over 50% of cases. Aspiration may also be considered in secondary pneumothorax of moderate size (air rim 1–2 cm) without breathlessness, with the difference that ongoing observation in hospital is required even after a successful procedure. In traumatic pneumothorax, larger tubes (28 F, 9.3 mm) are used. Chest tubes are required in PSPs that have not responded to needle aspiration, in large SSPs (>50%), and in cases of tension pneumothorax. They are connected to a one-way valve system that allows air to escape, but not to re-enter, the chest. This may include a bottle with water that functions like a water seal, or a Heimlich valve. They are not normally connected to a negative pressure circuit, as this would result in rapid re-expansion of the lung and a risk of pulmonary edema ("re-expansion pulmonary edema"). The tube is left in place until no air is seen to escape from it for a period of time, and X-rays confirm re-expansion of the lung. Pleurodesis and surgery Pleurodesis is a procedure that permanently eliminates the pleural space and attaches the lung to the chest wall. No long-term study (20 years or more) has been performed on its consequences. Good results in the short term are achieved with a thoracotomy (surgical opening of the chest) with identification of any source of air leakage and stapling of blebs followed by pleurectomy (stripping of the pleural lining) of the outer pleural layer and pleural abrasion (scraping of the pleura) of the inner layer. During the healing process, the lung adheres to the chest wall, effectively obliterating the pleural space. Recurrence rates are approximately 1%. Air travel is discouraged for up to seven days after complete resolution of a pneumothorax if recurrence does not occur. Underwater diving is considered unsafe after an episode of pneumothorax unless a preventive procedure has been performed. Professional guidelines suggest that pleurectomy be performed on both lungs and that lung function tests and CT scan normalize before diving is resumed. Aircraft pilots may also require assessment for surgery. Neonatal period For newborn infants with pneumothorax, different management strategies have been suggested including careful observation, thoracentesis (needle aspiration), or insertion of a chest tube. Needle aspiration may reduce the need for a chest tube, however, the effectiveness and safety of both invasive procedures have not been fully studied. ==Prevention==

A preventative procedure (thoracotomy or thoracoscopy with pleurodesis) may be recommended after an episode of pneumothorax, with the intention to prevent recurrence. Evidence on the most effective treatment is still conflicting in some areas, and there is variation between treatments available in Europe and the US. Surgery may need to be considered if someone has experienced pneumothorax on both sides ("bilateral"), sequential episodes that involve both sides, or if an episode was associated with pregnancy. ==Epidemiology==

The annual age-adjusted incidence rate (AAIR) of PSP is thought to be three to six times as high in males as in females. Fishman cites AAIR's of 7.4 and 1.2 cases per 100,000 person-years in males and females, respectively. Significantly above-average height is also associated with increased risk of PSP – in people who are at least 76 inches (1.93 meters) tall, the AAIR is about 200 cases per 100,000 person-years. Slim build also seems to increase the risk of PSP. Individuals who smoke at higher intensity are at higher risk, with a "greater-than-linear" effect; men who smoke 10 cigarettes per day have an approximate 20-fold increased risk over comparable non-smokers, while smokers consuming 20 cigarettes per day show an estimated 100-fold increase in risk. respectively, with the risk of recurrence depending on the presence and severity of any underlying lung disease. Once a second episode has occurred, there is a high likelihood of subsequent further episodes. Death from pneumothorax is very uncommon (except in tension pneumothoraces). British statistics show an annual mortality rate of 1.26 and 0.62 deaths per million person-years in men and women, respectively. A significantly increased risk of death is seen in older people and in those with secondary pneumothoraces, when the lung collapses due to another underlying health condition such as chronic lung disease. ==History==

An early description of traumatic pneumothorax secondary to rib fractures appears in Imperial Surgery by Turkish surgeon Şerafeddin Sabuncuoğlu (1385–1468), which also recommends a method of simple aspiration. Pneumothorax was described in 1803 by Jean Marc Gaspard Itard, a student of René Laennec, who provided an extensive description of the clinical picture in 1819. While Itard and Laennec recognized that some cases were not due to tuberculosis (then the most common cause), the concept of spontaneous pneumothorax in the absence of tuberculosis (primary pneumothorax) was reintroduced by the Danish physician Hans Kjærgaard in 1932. In 1941, the surgeons Tyson and Crandall introduced pleural abrasion for the treatment of pneumothorax. Prior to the advent of anti-tuberculous medications, pneumothoraces were intentionally caused by healthcare providers in people with tuberculosis in an effort to collapse a lobe, or entire lung, around a cavitating lesion. This was known as "resting the lung". It was introduced by the Italian surgeon Carlo Forlanini in 1888 and publicized by the American surgeon John Benjamin Murphy in the early 20th century (after discovering the same procedure independently). Murphy used the (then) recently discovered X-ray technology to create pneumothoraces of the correct size. ==Etymology==

The word pneumothorax comes from Greek pneumo- 'air' and thorax 'chest'. Its plural is pneumothoraces. ==Other animals==

Non-human animals may experience both spontaneous and traumatic pneumothorax. Spontaneous pneumothorax is, as in humans, classified as primary or secondary, while traumatic pneumothorax is divided into open and closed (with or without chest wall damage). The diagnosis may be apparent to the veterinary physician because the animal exhibits difficulty breathing in, or has shallow breathing. Pneumothoraces may arise from lung lesions (such as bullae) or from trauma to the chest wall. In horses, traumatic pneumothorax may involve both hemithoraces, as the mediastinum is incomplete and there is a direct connection between the two halves of the chest. Tension pneumothorax – the presence of which may be suspected due to rapidly deteriorating heart function, absent lung sounds throughout the thorax, and a barrel-shaped chest – is treated with an incision in the animal's chest to relieve the pressure, followed by insertion of a chest tube. For spontaneous pneumothorax the use of CT for diagnosis has been described for dogs and Kunekune pigs. == References ==