{"paper_id":"adbb959e-1b47-4e4b-b289-67e17ad9bcd8","body_text":"Pneumothorax is a composite word of Greek origin derived from\nπνεύμα (pneuma) and θώραξ (thorax), meaning air in the thorax\nand specifically within the pleural space. The term was first used by\na French physician Jean Marc Gaspard Itard, who was a student of\nRené Laennec, the inventor of the stethoscope, in the 19th century. [1] \nDuring that period, the most common cause of a pneumothorax was\ntuberculosis. Indeed, the iatrogenic introduction of a pneumothorax\nin the treatment of tuberculosis was accepted clinical practice in the\nlate 19th century and continued until the 1950s, when the use of\nanti-tuberculosis treatment became widely available. [2]\nThe term spontaneous pneumothorax refers to a pneumothorax\narising from neither trauma nor an iatrogenic cause. The traditional\nclassification of either primary spontaneous pneumothorax (PSP) or\nsecondary spontaneous pneumothorax (SSP) distinguishes between\npneumothoraces with (secondary) and without (primary) prior\nknown or clinically apparent underlying lung disease. However,\nalthough it is still widely used, the utility of making such a distinction\nis being challenged in many circles.\nThe purpose of this narrative non-systematic review is to highlight\nselected emerging evidence in this field and guide the practising\nclinician on an evidence-based approach to the management of\nspontaneous pneumothorax. For the purposes of the review, we\nconsider the single entity of spontaneous pneumothorax and specify\nPSP or SSP only where appropriate to the literature being referenced.\n\nSeveral risk factors for spontaneous pneumothorax have been\nidentified  (Table 1) . Individuals who present with a pneumothorax\nas a first manifestation of their lung disease tend to be tall with\na low body mass index, but PSP is most strongly associated with\ntobacco smoking. [3]  Cannabis smoking, altitude and air pollution\nare additional risk factors. [3 – 5]  In females, a rare cause is catamenial \npneumothorax. [6 , 7]  The peak incidence for PSP occurs at 35 years\nof age, whereas SSP occurs later in life at 53 years, reflecting\na parallel increase in chronic lung disease as age increases. [8] \nThe traditional SSP is associated with overt structural lung disease\nof which the most common underlying cause is chronic obstructive\npulmonary disease. [9 , 10]  Although the exact prevalence is not known,\nit is well recognised that in regions with high tuberculosis (TB)\nand HIV burden like South Africa (SA), infectious causes such\nas  Pneumocystis jirovecii  are the common causes of spontaneous\npneumothorax. [11]\nIt is now recognised that PSP is caused by underlying structural\nlung abnormalities that are not visible on a routine chest\nradiograph and not clinically apparent prior to the presentation\nwith a pneumothorax. Abnormalities which have been detected\nwith computed tomography (CT) or on histopathology include\nemphysema-like changes (blebs and bullae) of lung parenchyma\nunder the visceral pleura as well as a diffuse decrease in lung density\nmeasured by CT. One study identified a diffuse inflammatory process\nin the underlying lung parenchyma with subsequent increase in the\nporosity of the visceral pleura, [12]  and another found fibroblastic\nlesions consisting of pleural fibrosis with islands of fibroblastic foci\nwithin a myxoid stroma. [13]  Numerous genetic syndromes have been\nassociated with spontaneous pneumothorax  (Table 1)  and therefore\na detailed medical and family history, and careful clinical assessment\nof the patient should be performed.\n\nRoutine CT scanning was traditionally not advocated after the\nfirst episode of a perceived PSP. A recent clinical review of genetic\nabnormalities in PSP has suggested that a CT scan should be\nperformed in patients with a family history of pneumothorax,\nlung blebs, cysts, bullae or physical examination suggestive of a \nsyndrome. [14]  Some 10 - 12% of patients with PSP have a family history\nof a pneumothorax and it is thought that they have a higher recurrence\nrate. [15 , 16]  It is reported that between 5 - 10% of patients with an apparent\nPSP have underlying Birt-Hogg-Dubé (BHD) syndrome. [17 , 18]  In this\ncystic lung disease, there is a clear cost-benefit of performing a chest\nCT to identify patients with a high risk of recurrent pneumothorax and\nnumerous other long-term health implications. [19]\nIt has also been suggested that a CT be performed in females with\na first episode of spontaneous pneumothorax to diagnose occult\nlymphangioleiomyomatosis (LAM), as new advances in the treatment\nof this condition have emerged. [20]  In a study from Taiwan, [21]  3.6% of the\npatients had an unexpected finding on CT scan that was not seen on the\nchest radiograph and the majority of them were females.\nCT may identify a population at higher risk for recurrence of PSP\nthrough the assessment of the severity of the underlying abnormalities\nof the visceral pleura, but this remains to be proven in prospective\nstudies. [22]\nA CT scan should thus be considered in the following patients with\nspontaneous pneumothorax: patients older than 55 years of age as an\nunderlying lung disease is more likely; patients with a family history of\npneumothorax, lung blebs, cysts or bullae; patients with a family history\nor clinical signs of a genetic syndrome; females; and non-smokers.\n\nCurrent guidelines for the management of spontaneous pneumothorax \nrequire an assessment of the size of the pneumothorax. [23 , 24]  However,\nthe evidence for using size in the management of pneumothoraces is not\nrobust and there is poor agreement in the methods of measurement. [25] \nCT is generally acknowledged as the best method for estimating the\nsize of a pneumothorax by various techniques including the Collins\nor Rhea methods. [26]  The traditional chest radiograph-based method\nof quantification is the light index, but its accuracy is inconsistent. [3 , 27] \nThe British Thoracic Society (BTS) guidelines use a measurement of\nthe distance from the chest wall to the lung edge taken at the level of\nthe hilum on chest radiograph, while the American College of Chest\nPhysicians (ACCP) measure this distance at the apex of the lung\n (Fig. 1) . [23 , 25]  A large pneumothorax is more than 2 cm at the hilum\naccording to the BTS and more than 3 cm at the apex according to the\nACCP. Nikolic  et al. [28]  elegantly demonstrated that the use of the BTS\nguidelines is associated with less invasive treatment than the ACCP\nguidelines and that following the ACCP guidelines resulted in 65% of\nthe patients having an intercostal drain (ICD) inserted unnecessarily.\nThe BTS guidelines do state that the size of the pneumothorax is\nless important than the degree of clinical compromise. The decision\nto proceed with invasive management should rather be based on\nsymptoms and the clinical stability of the patient. They defined\nstability as having a respiratory rate <24, heart rate of 60 - 120 bpm,\noxygen saturation more than 90% on room air, blood pressure\n>90/60 mmHg and being able to complete full sentences between\nbreaths. [23 , 24]  While these criteria are not absolute, the decision to\npursue a non-invasive management strategy in a pneumothorax\nwhich exceeds the BTS and ACCP size-based guidelines must be\nsupported by an initial clinical assessment of stability as well as close\nobservation.\nEstimation of size of a pneumothorax based on routine chest\nradiography. The American guidelines generally use the intrapleural\ndistance from the apex to the cupola of the lung (a), whereas the British\nThoracic Society uses the intrapleural distance at the hilum (b).\nInternational guidelines disagree on the role of needle aspiration.\nThe ACCP guidelines do not advocate needle aspiration if active\nintervention is required and the BTS guidelines advise needle\naspiration of up to 2.5 L as the first step in the management of PSP,\nwith the option of proceeding to catheter drainage with a small-bore\nICD. Needle aspiration has been shown to be effective, with decreased\nlength of hospital stay, decreased complications and similar recurrence\nrates compared with ICD. [29 – 32]  However, needle aspiration fails if the\nair leak is still present at the time of the procedure. It has been shown\nthat compliance with the BTS guidelines in general is poor and most\nclinicians favour ICD insertion as primary intervention over needle\naspiration. [33 , 34]  This might reflect the fact that 20 - 50% of patients will\nrequire a second procedure despite the needle aspiration, [29 , 35]  which\nphysicians are keen to avoid. There is also a perception that needle\naspiration is more time-consuming in the emergency unit setting. [32]\nIn general, we would recommend that in patients with spontaneous\npneumothorax who are judged to need intervention, are not\n in extremis , and the risk of persistent air leaks is judged to be low,\nneedle aspiration may be attempted first. If needle aspiration is not\npossible or has failed, it is advised to insert a small-bore ICD.\nFor many years, it has been argued that in addition to allowing the\nair in the pleural space to escape and the lung to re-expand after a\npneumothorax, an ICD also causes inflammation of the pleural\nsurface and promotes auto-pleurodesis, which reduces the relapse\nrate. [36]  However, there is a growing body of evidence suggesting that\na conservative approach to managing pneumothoraces which avoids\nICD use may have better outcomes in selected patients, with fewer\ninfectious complications, bleeding, organ injury, shorter hospital stay\nand lower subsequent risk of recurrence.\nThe average rate of resolution of a pneumothorax without the insertion\nof an ICD ranges from 1.25% to 2.2% of the volume of the hemithorax\nper day, although larger pneumothoraces tend to resolve faster than\nsmall ones and there is significant variation between individuals. [23 , 25]  \nTheoretically, the longer time that the lung spends partially collapsed\nallows the pleural defect to heal. The level of evidence for supplemental\noxygen treatment during conservative management is low. [37]  One study\nfound a rate of resolution of 4.27% per day with supplemental oxygen\ncompared with 2.06% per day without. [38]\nAs early as 1966, Stradling and Poole [39]  published a large series\nof patients who were managed conservatively and found that only\n25% of all spontaneous pneumothoraces needed any form of active\nintervention. In the group without underlying lung disease, 80%\nexpanded without any intervention, with a mean expansion time of\n22.5 days and the mean expansion time was 30.8 days without any\nintervention in the group with underlying emphysema. More than\nhalf of the patients considered to have underlying emphysema were\nmanaged without any intervention. Interestingly, the relapse rate\nwas 11% over a period of 6 years, which is strikingly lower than the\nrecently documented relapse rates of 22 - 54% at 1 year in patients\nmanaged actively with aspiration or ICD insertion. [30 , 40 - 42]\nSimilarly, a recent Australian [43]  retrospective study found that\nconservative management of PSPs (irrespective of size) had similar\nrecurrence rates, fewer complications and shorter hospital stay than\nthe intervention group, even in large pneumothoraces of >50% of the\nhemithorax. This study however did not include patients with overt\nunderlying lung disease.\nA landmark study conducted by Brown  et al. [44]  comparing\nconservative with interventional management of moderate-to-large PSP showed an almost twice as high recurrence rate in the\ninterventional group (16.8% v. 8.8%), along with decreased length\nof hospital stay and complications in the conservative arm. Less\nthan a quarter (15.4%) of patients initially selected for conservative\nmanagement required intervention during the initial follow-up due to\npersistent symptoms or instability. This trial provides more evidence\nthat conservative management can be considered even in large\npneumothoraces provided that the patient remains haemodynamically\nstable and has prompt access to healthcare.\nIn addition to rethinking whether an ICD is indicated in the first\ninstance, one should also carefully consider the size of the ICD that\nis inserted. The current BTS guidelines show that small ICDs of 16F\nor less results in reduced complication rates compared with large-bore\nICDs>16F. [23]  Moreover, a more recent meta-analysis concluded that\nICDs of 14F or less have lower complication rates, similar success rates,\nshorter drainage duration and shorter length of hospital stay. [45]  In the\nmajority of medical and emergency wards in SA, the common practice\nis to insert an ICD for any pneumothorax and the only available ICDs\nare 24F and above. It is therefore important to emphasise that both\npatient safety and patient comfort are improved with the thoughtful\nuse (or not) of an ICD.\nThere may be a role for the outpatient management of a spontaneous\npneumothorax in the correct setting. Two studies recently evaluated\nambulatory management of spontaneous pneumothoraces with the\nplacement of small-bore ICD’s attached to one-way valves which allowed\nslow air leakage. The one study had a success rate of 79% in patients with\nlarge pneumothoraces and 37% had full outpatient management, [46] \nwhile the other study found that ambulatory management can be\neffective even in patients with overt underlying lung disease with a\nmean drainage time of 5.84 days. [47]  Both studies found that this method \nwas associated with reduced hospital costs and\navoided potential tension pneumothoraces. In\na situation where a patient has ready access to\ntransport and is close to the treating healthcare\nfacility, ambulatory management may be an\nappropriate strategy. An algorithm for the\nmanagement of a first episode of spontaneous\npneumothorax (primary or secondary) is\nsuggested  (Fig. 2) .\nProposed algorithm for management of primary spontaneous pneumothorax.\nCXR = chest radiograph\nICD = intercostal drain\nCT = computed tomography (chest)\nVATS = video-assisted thoracoscopic surgery.\n*Not if talc pleurodesis via ICD is planned.\n\nThe greatest risk for recurrence is within the\nfirst year, [24 , 42]  with a recent systematic review\nfinding that the pooled 1-year recurrence rate\nfor PSP is 29%. [40]  Risk factors for recurrence\ninclude smoking, younger age, female sex, low\nbody weight, height and radiological evidence\nof underlying lung abnormalities. [40 , 48]  Cessation\nof smoking is central to preventing recurrence\nand physicians must be active in advocating this\nfor all their patients. [49]\nTherapeutic options for preventing\nrecurrence of a spontaneous pneumothorax\ninclude pleurodesis with large-particle talc or\nother sclerosants via medical thoracoscopy or\nvideo-assisted thoracoscopic surgery (VATS),\nopen thoracotomy and pleurectomy, and VATS\nwith pleurectomy and pleural abrasion. Open\nthoracotomy and pleurectomy has a recurrence\nrate of 1% while VATS with pleurectomy\nand pleural abrasion has a recurrence rate\nof 5%. [50]  However, VATS is associated with\nshorter hospital stay, reduced hospital costs,\npostoperative bleeding complications and pain\nthan open thoracotomy. [51 – 53]  Guidelines advise\ndefinitive pleurodesis in patients with recurrent\nPSP, persistent PSP, bilateral PSP, professions at\nrisk and in patients with underlying overt lung\ndisease.\nOnce patients have undergone initial\nmanagement of the pneumothorax, whether\ntreated invasively or conservatively, the risk for\nrecurrence should be assessed. The management\nstrategy for prevention will depend on available\nexpertise, operative risk and patient preference.\nIn most cases, VATS or medical thoracoscopy\nis preferred and for those unable or unwilling\nto undergo surgery, chemical pleurodesis via\nICD is recommended. Ideally, the timing of the\nprocedure should be within the same hospital\nadmission as the risk for recurrence is highest\nwithin the first month, [23]  although this is not\nalways logistically possible.\n\nOur knowledge about spontaneous\npneumothoraces has evolved in recent years, \nand it is clear that the old labels of primary and\nsecondary may not be appropriate anymore.\nIndividuals previously managed under the PSP\nguidelines invariably have pleuropulmonary\ndisease on chest CT or histology and the\nliterature is still unclear on how we should\ndeal with this fact. Evidence seems to suggest\nthat more patients deserve to be investigated\nfor underlying disease than is currently\nrecommended. In addition to this, there are\nemerging data to suggest that conservative\ntreatment of spontaneous pneumothoraces\nof any size is appropriate in stable patients.\nHowever, careful consideration must be\ngiven to the necessity to intervene to prevent\nrecurrence, especially in settings where access\nto VATS or open pleurectomy is limited and\ntalc pleurodesis is the only practical option.\nIf initial invasive management is needed, it\nneed not always be the traditional large-bore\nICD. In fact, a small-bore ICD is preferable\nand ambulatory management could be\nconsidered. The next decade should see \nrandomised trials to clarify these issues. For\nnow, clinicians should endeavour to be more\ncritical of intervention choices in a patient\nwith a spontaneous pneumothorax.","source_license":"CC-BY-4.0","license_restricted":false}