CHEST
Commentary
Air Travel and Pneumothorax Xiaowen Hu, MD; Clayton T. Cowl, MD, FCCP; Misbah Baqir, MBBS; and Jay H. Ryu, MD, FCCP
The number of medical emergencies onboard aircraft is increasing as commercial air traffic increases and the general population ages, becomes more mobile, and includes individuals with serious medical conditions. Travelers with respiratory diseases are at particular risk for in-flight events because exposure to lower atmospheric pressure in a pressurized cabin at cruising altitude may result in not only hypoxemia but also pneumothorax due to gas expansion within enclosed pulmonary parenchymal spaces based on Boyle’s law. Risks of pneumothorax during air travel pertain particularly to those patients with cystic lung diseases, recent pneumothorax or thoracic surgery, and chronic pneumothorax. Currently available guidelines are admittedly based on sparse data and include recommendations to delay air travel for 1 to 3 weeks after thoracic surgery or resolution of the pneumothorax. One of these guidelines declares existing pneumothorax to be an absolute contraindication to air travel although there are reports of uneventful air travel for those with chronic stable pneumothorax. In this article, we review the available data regarding pneumothorax and air travel that consist mostly of case reports and retrospective surveys. There is clearly a need for additional data that will inform decisions regarding air travel for patients at risk for pneumothorax, including those with recent thoracic surgery and transthoracic needle biopsy. CHEST 2014; 145(4):688–694 Abbreviations: BHD 5 Birt-Hogg-Dubé syndrome; CPAM 5 congenital pulmonary airway malformation; HRCT 5 highresolution CT; LAM 5 lymphangioleiomyomatosis; TTNB 5 transthoracic needle biopsy
were 2.8 billion people traveling by air in There 2011 worldwide according to the International Air
Transport Association.1 Air travel is safe and reasonably comfortable, but multiple factors including psychologic stress, jet lag, longer flight duration, and preexisting medical conditions cause some passengers to become ill during flight.2-8 The average age of airline passengers is increasing in parallel with that of the general population, and many more, including individuals with chronic medical disorders, are traveling farther and to more remote locations than ever before. Manuscript received October 4, 2013; revision accepted November 23, 2013. Affiliations: From the Department of Respiratory Disease (Dr Hu), Anhui Provincial Hospital, Hefei, China; and Division of Pulmonary and Critical Care Medicine (Drs Cowl, Baqir, and Ryu) and Division of Preventive, Occupational and Aerospace Medicine (Dr Cowl), Mayo Clinic, Rochester, MN. Correspondence to: Jay H. Ryu, MD, FCCP, Division of Pulmonary and Critical Care Medicine, Mayo Clinic, Gonda 18 S, 200 First St SW, Rochester, MN 55905; e-mail: [email protected] © 2014 American College of Chest Physicians. Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details. DOI: 10.1378/chest.13-2363 688
Several studies suggest that the frequency of in-flight medical events onboard commercial flights is increasing.4-7,9 Based on data gathered over a 3-year period from 2008 to 2010, the incidence of in-flight medical emergency was estimated to be one per 604 commercial airline flights.4 Neurologic, respiratory, GI, and cardiac problems are responsible for the most serious events during flight and account for the majority of flight diversions.4,5,10 Federal Aviation Administration (FAA) regulations require that aircraft designed for commercial air transportation contain pressurized cabins constructed with minimum cabin pressurization capability equivalent to 2,438 m (8,000 ft) at the maximum operating altitude.11,12 At 2,438 m, Po2 falls to the equivalent of breathing 15.1% oxygen at sea level. Under this condition, Pao2 ranges between 60 mm Hg and 75 mm Hg (arterial oxygen saturation determined by pulse oximetry, 89%-94%) for healthy individuals and may be lower when active or sleeping. Furthermore, peak cabin altitudes higher than 2,438 m have been measured on approximately 10% of flights.13 Commentary
Although the issue of hypoxemia during air travel, particularly for those with respiratory diseases, has been addressed frequently in the medical literature there is a paucity of data pertaining to pneumothorax. The purpose of this review is to address relevant issues regarding pneumothorax as well as other forms of intrathoracic barotrauma associated with air travel, including risk factors. Physiologic Considerations Boyle’s law describes the inversely proportional relationship between pressure and volume for a fixed amount of gas in a closed system kept at a constant temperature. Altitude exposure inherent in air travel is associated with a reduction of ambient barometric pressure which will, in turn, cause expansion of gas within enclosed spaces in the human body by 25% to 30% at the typical cruising altitude of a commercial airline flight.11,14,15 Such expansion of an intrathoracic gas-containing lesion occurs when there is absence of communication with the tracheobronchial tree, thus preventing equalization of pressure. This type of air trapping can be demonstrated in cystic lung diseases using expiratory high-resolution CT (HRCT) scanning. Two studies have examined this issue by comparing inspiratory and expiratory images on HRCT scanning in patients with various cystic lung diseases, including bullae, honeycomb lung, lymphangioleiomyomatosis (LAM), pulmonary Langerhans cell histiocytosis, cystic pulmonary airway (adenomatoid) malformation (CPAM), and cystic bronchiectasis.16,17 The cystic lesions in most of these cystic lung diseases decreased in size with expiration suggesting direct communication with the tracheobronchial tree. However, cystic lesions in a few patients with bullae and CPAM exhibited air trapping. It is also possible that superimposed processes such as airway collapse, inflammation or edema, and mucus plugging may cause at least temporary air trapping in cystic lung lesions that usually communicate with the airways. In-flight Pneumothorax Pneumothorax occurring in-flight appears to be rare based on survey studies examining medical emergencies occurring onboard aircrafts. A prospective multicenter observational study of flight outcomes was conducted by Coker and colleagues18 on 431 patients with a variety of lung diseases traveling by air. In-flight symptoms of respiratory distress were reported by 18% of patients but there were no in-flight emergencies, flight diversions, pneumothoraces, or deaths. Sand and colleagues5 identified 10,189 cases of in-flight medical emergencies in a retrospective survey of journal.publications.chestnet.org
two European airlines with deaths occurring in 0.4% of these emergencies, but no cases of pneumothorax were documented. A more recent survey of 11,920 medical emergencies occurring on multiple commercial airlines also made no mention of pneumothorax.4 However, there are multiple case reports of pneumothorax occurring in-flight as summarized in Table 1.19-30 Identifiable risk factors among these cases included bullae or blebs, CPAM, and LAM, although some subjects had no underlying lung disease. Cystic lung diseases, whether focal or diffuse, pose a potential risk for in-flight pneumothorax (Table 2).18,21,23,31,32 There are many forms of cystic lung diseases, the most common of which is bullous emphysema.33-35 However, the disorder that is associated with the highest risk of spontaneous pneumothorax is LAM, a rare disease affecting mostly women and characterized by infiltration of the lung with atypical smooth muscle-like cells (LAM cells) resulting in cystic changes.36,37 Two survey studies examined the risk of pneumothorax with air travel for patients with LAM and estimated the risk of pneumothorax per flight to be 1.1% and 2.2%, respectively.21,23 In one of these studies, none of the subjects knew they had LAM prior to the episode of in-flight pneumothorax.23 The other study included patients with idiopathic pulmonary fibrosis and sarcoidosis who had flown with none of them having experienced pneumothorax.21 Birt-Hogg-Dubé syndrome (BHD) is an autosomaldominant hereditary disorder characterized by multiple benign cutaneous neoplasms, cystic lung disease, and a markedly increased risk of renal neoplasms.38 Most adult patients manifest lung cysts on CT imaging, and 24% to 38% have a history of spontaneous pneumothorax.39,40 Hoshika and colleagues32 surveyed 48 patients with BHD with a prior history of pneumothorax to assess the risk of pneumothorax associated with air travel. Most of these patients had experienced recurrences with an average number of pneumothorax per patient of four (range, one to 10 episodes). Forty patients reported that they had traveled by air for a total of 2,142 flights, and none had experienced pneumothorax related to air travel. The risk of in-flight pneumothorax appears to be very low for patients with cystic lung diseases, with the exception of those with LAM. It is noted, however, that there is a large variation among airlines in documenting in-flight medical emergencies.41 True incidence of specific illnesses associated with air travel has been difficult to assess, and follow-up data are often incomplete as are causes of in-flight deaths (often presumed to be cardiac). Thus, some have argued for a centralized registry of in-flight medical emergencies with standardized documentation.11,41,42 CHEST / 145 / 4 / APRIL 2014
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Table 1—Reports of In-flight Pneumothorax and Associated Outcome Study/Year Flux and Dille /1969 Ho28/1975 Lim et al27/1985 Voge and Anthracite26/1986 Robb25/1994 Wallace et al24/1995 Grossman et al30/2005 Pollock-BarZiv et al23/2007 Lin et al22/2008 Taveira-DaSilva et al21/2009 Tiemensma et al20/2010 Madan et al19/2012 29
Underlying Disease
No. of Subjects
Outcome
Comments
Bulla None Subpleural blebs None None None None LAM Bullae with AAT deficiency emphysema LAM Bullae from prior tuberculosis CPAM
1 1 1 12 1 1 2 10 1 6 1 1
Nonfatal Nonfatal Nonfatal Nonfatal Nonfatal Nonfatal Nonfatal Nonfatal Nonfatal Nonfatal Fatal Nonfatal
Military pilot Military jet instructor Military pilot Military aircrew Military pilot Commercial passenger Military pilots Commercial passengers Military pilot Commercial passengers Commercial passenger Commercial passenger
AAT 5 a1-antitrypsin; CPAM 5 congenital pulmonary airway (adenomatoid) malformation; LAM 5 lymphangioleiomyomatosis.
Military jet aviators repeatedly use Valsalva maneuvers during flight and are at risk for pneumothorax and pneumomediastinum. For example, Ho28 described a 29-year-old military jet instructor who experienced onset of pleuritic chest pain during a flight and underwent emergency chest radiography on landing. However, he soon flew on another mission that day before the results of his chest radiography became known and experienced worsening chest pain and dyspnea during the second flight. The second chest radiograph was performed, which revealed a left-sided pneumothorax with complete collapse of the underlying lung, worse compared with that seen on the earlier chest radiograph. He was treated with chest tube drainage and recovered uneventfully. Retrospective questionnaire survey data obtained from 112 US Air Force aircrew who had experienced spontaneous pneumothorax identified 12 who had in-flight onset of symptoms.26 This study did not mention any fatalities related to pneumothorax. Fatality related to pneumothorax during air travel appears to be exceedingly rare. We identified only one case of fatal in-flight pneumothorax. Tiemensma and colleagues20 reported a sudden death occurring on an airplane in a 27-year-old woman with treated
pulmonary TB. She died of tension pneumothorax resulting from a ruptured bulla. Risk of Air Travel in Patients With Recent Pneumothorax or Thoracic Surgery The safety of air travel for patients with recent pneumothorax or thoracic surgery is still a matter of debate, largely due to the paucity of relevant data. In 1999, Cheatham and Safcsak43 reported 12 consecutive patients with traumatic pneumothorax (all involving motor vehicle accidents) expressing a desire to travel by air. Eleven patients flew 14 days after radiographic resolution of their pneumothorax, and all remained asymptomatic during flight. One patient flew 3 days after resolution of pneumothorax and developed respiratory distress in-flight with symptoms suggestive of a recurrent pneumothorax. Her symptoms resolved within a few hours of landing, and chest radiography was not performed. Based on these data, the authors concluded that commercial air travel appeared to be safe 14 days following radiographic resolution of a traumatic pneumothorax. Risk associated with air travel in patients who experienced post-transthoracic needle biopsy (TTNB)
Table 2—Risk of Air Travel-Associated Pneumothorax by Underlying Conditions Study/Year
Underlying Condition
No. of Study Subjects
Prevalence, %
Comments
Coker et al18/2007 Pollock-BarZiv et al23/2007 Taveira-DaSilva et al21/2009 Taveira-DaSilva et al21/2009 Taveira-DaSilva et al21/2009 Tam et al31/2011 Hoshika et al32/2012
Various lung diseases LAM LAM IPF Sarcoidosis Recent TTNB BHD
500 276 204 47 48 179 40
0 3.6 2.9 0 0 0 0
… 2.2% risk per flight 1.1% risk per flight … … … …
BHD 5 Birt-Hogg-Dubé; IPF 5 idiopathic pulmonary fibrosis; TTNB 5 transthoracic needle biopsy. See Table 1 legend for expansion of other abbreviations. 690
Commentary
pneumothorax was assessed in a telephone survey of 65 patients of whom 77% traveled by air within 4 days of the final postbiopsy chest radiograph, which demonstrated residual pneumothorax in more than onehalf of the patients.31 One of these patients flew with a chest tube and Heimlich valve used to manage an active air leak. Only one of 65 patients noted symptoms during flight consisting of increased chest pain and shortness of breath but none sought medical attention after the flight other than for removal of the chest tube in the aforementioned patient. These authors concluded that air travel within 2 weeks of TTNBrelated pneumothorax is safe even for those with radiographic evidence of residual pneumothorax.31 There are no data that directly relate to the risk of air travel-associated pneumothorax for patients who have undergone thoracic surgery. In 2010, Szymanski et al44 conducted a survey of 68 US thoracic surgeons for their recommendations regarding air travel by patients with postoperative pneumothorax. Forty-four percent of thoracic surgeons recommended that patients wait variable periods of time with a median of 7 days (range, 1-42 days) following complete resolution of pneumothorax prior to air travel, while 46% opined that it would be acceptable for individuals to fly despite residual pneumothorax (allowed more often for patients with , 5%, 5%-10%, and 10%-30% than those with 30%-50% pneumothorax), and 10% felt air travel to be contraindicated. Only one of the surveyed surgeons knew of an air travel-related complication among his patients (one patient who experienced thoracic pain during ascent). Based on this survey, symptomatic recurrence or exacerbation of postoperative pneumothorax appears to be rare while it is apparent that a wide variability exists among thoracic surgeons regarding their recommendations for air travel by patients after thoracic surgery. Air Travel With Chronic Pneumothorax Although pneumothorax is generally considered a contraindication for air travel, there are reports of patients with chronic pneumothorax who have flown uneventfully.21,45 Currie and colleagues45 described a 36-year-old man who had a persistent left-sided loculated pneumothorax for 4 years following staphylococcal pneumonia. After satisfactory results on a hypoxic challenge test (breathing 15% oxygen), the patient was deemed fit to fly and completed over a dozen flights including transatlantic routes without difficulty. As described previously, patients with LAM are at high risk of spontaneous pneumothorax (70%-80% lifetime risk), and some of these patients have chronic pneumothorax (Fig 1). In the study of 281 patients with LAM described by Taveira-DaSilva et al21 there were eight patients with chronic pneumothorax who journal.publications.chestnet.org
Figure 1. High-resolution CT scan of the chest of a 50-year-old female nonsmoker with pulmonary lymphangioleiomyomatosis demonstrating a loculated right pneumothorax that has been present for 1 y. Talc pleurodesis had been performed after two episodes of right-sided pneumothorax. She was asymptomatic during to and from transatlantic flights during the month following this CT scan study.
traveled by commercial airline to the study center. The pneumothoraces had been present prior to air travel for a mean duration of 2.2 years (range, 1-4.5 years), and two of these eight patients had previously undergone a pleurodesis. No change in volume of the pneumothorax was noted over a total observation period of 4.4 0.4 (mean SEM) years. No adverse consequences related to air travel occurred. Other Forms of Intrathoracic Barotrauma Associated With Air Travel Other forms of intrathoracic complications related to changes in barometric pressure during air travel have included pneumomediastinum, systemic air embolism, and bulla expansion with pulmonary hemorrhage. Three cases of pneumomediastinum associated with commercial flight were managed conservatively with uneventful resolution.46-48 Grossman and colleagues30 described 10 Israeli Air Force aviators in training who experienced pneumomediastinum caused by Valsalva maneuvers practiced during the basic training period (not flight-related). Two of these subjects had concomitant pneumothorax, one of whom required chest tube drainage. All subjects subsequently assumed flying duties without recurrence or other adverse consequences. Four cases of systemic air embolism during air travel in patients with pulmonary cystic lesions have been reported. A case of fatal air embolism caused by rupture of a large intrapulmonary bronchogenic cyst during air travel was described by Zaugg and colleagues.49 Two additional cases of systemic embolism CHEST / 145 / 4 / APRIL 2014
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during air travel have been associated with bullae. One of these patients died of the complication while the other suffered a unilateral hemiparesis.50,51 One remaining case consisted of cerebral air embolism caused by rupture of a CPAM resulting in a left hemiparesis and bulbar palsy.52 Chen and colleagues53 reported a 62-year-old man with emphysema and bullae who experienced recurrent hemoptysis during two consecutive commercial flights. His postflight chest radiograph revealed a bulla that had enlarged when compared with a preflight chest radiograph with a new air-fluid level. Wedge resection of the bulla revealed a thin fibrous wall with evidence of hemorrhage. Management Implications Current recommendations for air travel after pneumothorax or thoracic surgeries are largely extrapolated from anecdotal case reports and retrospective surveys and are outlined in Table 3.11,54 Guidelines from the Aerospace Medical Association published in 2003 suggest delaying air travel for 2 to 3 weeks following resolution of pneumothorax or after uncomplicated thoracic surgery.11 Pneumothorax is considered an absolute contraindication to air travel due to the risk of expansion during flight possibly resulting in tension pneumothorax.11 The most recent version of the British Thoracic Society guidelines regarding air travel for passengers with respiratory diseases (published in 2011) recommends a delay of 1 week after radiographic resolution of pneumothorax and preferably a 2-week delay for traumatic pneumothorax.54 One-week delay after resolution of pneumothorax is also advised for patients who have undergone thoracic surgery. Those with closed pneumothorax are advised not to travel on commercial flights with the rare exception of those with chronic loculated air collection who have undergone a careful clinical evaluation.54
There are several factors that need to be considered in determining the risk of pneumothorax in an individual patient, including type and severity of underlying lung disease, type of pneumothorax (spontaneous, traumatic, iatrogenic), prior history of pneumothoraces and treatments (chest tube, pleurodesis), and comorbidities (particularly cardiopulmonary disorders), as well as duration and route (eg, transoceanic) of air travel. Those with limited cardiopulmonary reserve will experience more severe consequences from a pneumothorax. Prior pleurodesis will decrease the risk of recurrent pneumothorax or limit the degree of lung collapse if pneumothorax recurs. Clearly, the decision to travel by air needs to be individualized, taking into account not only the aforementioned issues but also patients’ own perspectives and needs. Based on prior reports and our clinical experience, chronic loculated pneumothorax need not be an absolute contraindication to air travel. For patients with large intraparenchymal cystic lesions, for example, CPAM or bronchogenic cyst, elective resection prior to air travel should be considered. HRCT scanning of the chest with inspiratory and expiratory views may be helpful in some cases of cystic lung diseases to assess communication of the lesion with airways which would allow for equilibration of pressures. Management of suspected in-flight pneumothorax depends on the clinical status of the stricken passenger, available medical supplies, and the route of air travel. Supplemental oxygen should be provided and descent to the nearest airport, if available, needs to be considered. If signs of tension pneumothorax develop, urgent decompression and drainage will need to be undertaken using available supplies onboard. Emergency medical kits vary from airline to airline but usually include needles, IV catheters, and syringes. A dramatic account of managing tension pneumothorax in-flight using a scalpel, coat hanger, urinary catheter, and a bottle of water for underwater seal drain was provided by Wallace and colleagues.24
Table 3—Guidelines for Air Travel After Pneumothorax Study/Year Aerospace Medical Association Medical Guidelines Task Force11/2003
Ahmedzai et al54/2011
Air Travel Guidelines Pneumothorax is an absolute contraindication to air travel. Delay air travel for 2 or 3 wk after resolution of pneumothorax or uncomplicated thoracic surgery. Some stable patients with a persistent bronchopleural fistula can fly safely with a chest tube using a one-way Heimlich valve assembly. The presence of lung cysts or bullae is usually not a problem as long as the airways communicate with the abnormal air collection. Delay air travel for 7 d after resolution of pneumothorax. Delay air travel for 2 wk after resolution of trauma-related pneumothorax. Delay air travel for 7 d after full lung expansion in patients who have undergone thoracic surgery. Patients with closed pneumothorax should not travel on commercial flights (with very rare exceptions). Patients with LAM should be advised of the risk of pneumothorax with air travel and undergo evaluation if symptoms such as chest pain or shortness of breath are present.
See Table 1 legend for expansion of abbreviation. 692
Commentary
Conclusions Pneumothorax and other forms of intrathoracic barotrauma related to air travel are rare. Patients with cystic lung diseases, recent pneumothorax or thoracic surgery, and chronic pneumothorax need particular attention. The decision regarding air travel needs to be individualized by assessing risk based on specific disease-related issues and comorbidities while also taking into account patients’ preferences and needs. Additional data are needed to better inform decisions regarding air travel for patients at risk for pneumothorax. Acknowledgments Financial/nonfinancial disclosures: The authors have reported to CHEST the following conflicts of interest: Dr Cowl has received research contract funding in support of development of aviation oxygen delivery systems for pilots and passengers in aircraft. Drs Hu, Baqir, and Ryu have reported that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.
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Commentary
Commentary
Air Travel and Pneumothorax Xiaowen Hu, MD; Clayton T. Cowl, MD, FCCP; Misbah Baqir, MBBS; and Jay H. Ryu, MD, FCCP
The number of medical emergencies onboard aircraft is increasing as commercial air traffic increases and the general population ages, becomes more mobile, and includes individuals with serious medical conditions. Travelers with respiratory diseases are at particular risk for in-flight events because exposure to lower atmospheric pressure in a pressurized cabin at cruising altitude may result in not only hypoxemia but also pneumothorax due to gas expansion within enclosed pulmonary parenchymal spaces based on Boyle’s law. Risks of pneumothorax during air travel pertain particularly to those patients with cystic lung diseases, recent pneumothorax or thoracic surgery, and chronic pneumothorax. Currently available guidelines are admittedly based on sparse data and include recommendations to delay air travel for 1 to 3 weeks after thoracic surgery or resolution of the pneumothorax. One of these guidelines declares existing pneumothorax to be an absolute contraindication to air travel although there are reports of uneventful air travel for those with chronic stable pneumothorax. In this article, we review the available data regarding pneumothorax and air travel that consist mostly of case reports and retrospective surveys. There is clearly a need for additional data that will inform decisions regarding air travel for patients at risk for pneumothorax, including those with recent thoracic surgery and transthoracic needle biopsy. CHEST 2014; 145(4):688–694 Abbreviations: BHD 5 Birt-Hogg-Dubé syndrome; CPAM 5 congenital pulmonary airway malformation; HRCT 5 highresolution CT; LAM 5 lymphangioleiomyomatosis; TTNB 5 transthoracic needle biopsy
were 2.8 billion people traveling by air in There 2011 worldwide according to the International Air
Transport Association.1 Air travel is safe and reasonably comfortable, but multiple factors including psychologic stress, jet lag, longer flight duration, and preexisting medical conditions cause some passengers to become ill during flight.2-8 The average age of airline passengers is increasing in parallel with that of the general population, and many more, including individuals with chronic medical disorders, are traveling farther and to more remote locations than ever before. Manuscript received October 4, 2013; revision accepted November 23, 2013. Affiliations: From the Department of Respiratory Disease (Dr Hu), Anhui Provincial Hospital, Hefei, China; and Division of Pulmonary and Critical Care Medicine (Drs Cowl, Baqir, and Ryu) and Division of Preventive, Occupational and Aerospace Medicine (Dr Cowl), Mayo Clinic, Rochester, MN. Correspondence to: Jay H. Ryu, MD, FCCP, Division of Pulmonary and Critical Care Medicine, Mayo Clinic, Gonda 18 S, 200 First St SW, Rochester, MN 55905; e-mail: [email protected] © 2014 American College of Chest Physicians. Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details. DOI: 10.1378/chest.13-2363 688
Several studies suggest that the frequency of in-flight medical events onboard commercial flights is increasing.4-7,9 Based on data gathered over a 3-year period from 2008 to 2010, the incidence of in-flight medical emergency was estimated to be one per 604 commercial airline flights.4 Neurologic, respiratory, GI, and cardiac problems are responsible for the most serious events during flight and account for the majority of flight diversions.4,5,10 Federal Aviation Administration (FAA) regulations require that aircraft designed for commercial air transportation contain pressurized cabins constructed with minimum cabin pressurization capability equivalent to 2,438 m (8,000 ft) at the maximum operating altitude.11,12 At 2,438 m, Po2 falls to the equivalent of breathing 15.1% oxygen at sea level. Under this condition, Pao2 ranges between 60 mm Hg and 75 mm Hg (arterial oxygen saturation determined by pulse oximetry, 89%-94%) for healthy individuals and may be lower when active or sleeping. Furthermore, peak cabin altitudes higher than 2,438 m have been measured on approximately 10% of flights.13 Commentary
Although the issue of hypoxemia during air travel, particularly for those with respiratory diseases, has been addressed frequently in the medical literature there is a paucity of data pertaining to pneumothorax. The purpose of this review is to address relevant issues regarding pneumothorax as well as other forms of intrathoracic barotrauma associated with air travel, including risk factors. Physiologic Considerations Boyle’s law describes the inversely proportional relationship between pressure and volume for a fixed amount of gas in a closed system kept at a constant temperature. Altitude exposure inherent in air travel is associated with a reduction of ambient barometric pressure which will, in turn, cause expansion of gas within enclosed spaces in the human body by 25% to 30% at the typical cruising altitude of a commercial airline flight.11,14,15 Such expansion of an intrathoracic gas-containing lesion occurs when there is absence of communication with the tracheobronchial tree, thus preventing equalization of pressure. This type of air trapping can be demonstrated in cystic lung diseases using expiratory high-resolution CT (HRCT) scanning. Two studies have examined this issue by comparing inspiratory and expiratory images on HRCT scanning in patients with various cystic lung diseases, including bullae, honeycomb lung, lymphangioleiomyomatosis (LAM), pulmonary Langerhans cell histiocytosis, cystic pulmonary airway (adenomatoid) malformation (CPAM), and cystic bronchiectasis.16,17 The cystic lesions in most of these cystic lung diseases decreased in size with expiration suggesting direct communication with the tracheobronchial tree. However, cystic lesions in a few patients with bullae and CPAM exhibited air trapping. It is also possible that superimposed processes such as airway collapse, inflammation or edema, and mucus plugging may cause at least temporary air trapping in cystic lung lesions that usually communicate with the airways. In-flight Pneumothorax Pneumothorax occurring in-flight appears to be rare based on survey studies examining medical emergencies occurring onboard aircrafts. A prospective multicenter observational study of flight outcomes was conducted by Coker and colleagues18 on 431 patients with a variety of lung diseases traveling by air. In-flight symptoms of respiratory distress were reported by 18% of patients but there were no in-flight emergencies, flight diversions, pneumothoraces, or deaths. Sand and colleagues5 identified 10,189 cases of in-flight medical emergencies in a retrospective survey of journal.publications.chestnet.org
two European airlines with deaths occurring in 0.4% of these emergencies, but no cases of pneumothorax were documented. A more recent survey of 11,920 medical emergencies occurring on multiple commercial airlines also made no mention of pneumothorax.4 However, there are multiple case reports of pneumothorax occurring in-flight as summarized in Table 1.19-30 Identifiable risk factors among these cases included bullae or blebs, CPAM, and LAM, although some subjects had no underlying lung disease. Cystic lung diseases, whether focal or diffuse, pose a potential risk for in-flight pneumothorax (Table 2).18,21,23,31,32 There are many forms of cystic lung diseases, the most common of which is bullous emphysema.33-35 However, the disorder that is associated with the highest risk of spontaneous pneumothorax is LAM, a rare disease affecting mostly women and characterized by infiltration of the lung with atypical smooth muscle-like cells (LAM cells) resulting in cystic changes.36,37 Two survey studies examined the risk of pneumothorax with air travel for patients with LAM and estimated the risk of pneumothorax per flight to be 1.1% and 2.2%, respectively.21,23 In one of these studies, none of the subjects knew they had LAM prior to the episode of in-flight pneumothorax.23 The other study included patients with idiopathic pulmonary fibrosis and sarcoidosis who had flown with none of them having experienced pneumothorax.21 Birt-Hogg-Dubé syndrome (BHD) is an autosomaldominant hereditary disorder characterized by multiple benign cutaneous neoplasms, cystic lung disease, and a markedly increased risk of renal neoplasms.38 Most adult patients manifest lung cysts on CT imaging, and 24% to 38% have a history of spontaneous pneumothorax.39,40 Hoshika and colleagues32 surveyed 48 patients with BHD with a prior history of pneumothorax to assess the risk of pneumothorax associated with air travel. Most of these patients had experienced recurrences with an average number of pneumothorax per patient of four (range, one to 10 episodes). Forty patients reported that they had traveled by air for a total of 2,142 flights, and none had experienced pneumothorax related to air travel. The risk of in-flight pneumothorax appears to be very low for patients with cystic lung diseases, with the exception of those with LAM. It is noted, however, that there is a large variation among airlines in documenting in-flight medical emergencies.41 True incidence of specific illnesses associated with air travel has been difficult to assess, and follow-up data are often incomplete as are causes of in-flight deaths (often presumed to be cardiac). Thus, some have argued for a centralized registry of in-flight medical emergencies with standardized documentation.11,41,42 CHEST / 145 / 4 / APRIL 2014
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Table 1—Reports of In-flight Pneumothorax and Associated Outcome Study/Year Flux and Dille /1969 Ho28/1975 Lim et al27/1985 Voge and Anthracite26/1986 Robb25/1994 Wallace et al24/1995 Grossman et al30/2005 Pollock-BarZiv et al23/2007 Lin et al22/2008 Taveira-DaSilva et al21/2009 Tiemensma et al20/2010 Madan et al19/2012 29
Underlying Disease
No. of Subjects
Outcome
Comments
Bulla None Subpleural blebs None None None None LAM Bullae with AAT deficiency emphysema LAM Bullae from prior tuberculosis CPAM
1 1 1 12 1 1 2 10 1 6 1 1
Nonfatal Nonfatal Nonfatal Nonfatal Nonfatal Nonfatal Nonfatal Nonfatal Nonfatal Nonfatal Fatal Nonfatal
Military pilot Military jet instructor Military pilot Military aircrew Military pilot Commercial passenger Military pilots Commercial passengers Military pilot Commercial passengers Commercial passenger Commercial passenger
AAT 5 a1-antitrypsin; CPAM 5 congenital pulmonary airway (adenomatoid) malformation; LAM 5 lymphangioleiomyomatosis.
Military jet aviators repeatedly use Valsalva maneuvers during flight and are at risk for pneumothorax and pneumomediastinum. For example, Ho28 described a 29-year-old military jet instructor who experienced onset of pleuritic chest pain during a flight and underwent emergency chest radiography on landing. However, he soon flew on another mission that day before the results of his chest radiography became known and experienced worsening chest pain and dyspnea during the second flight. The second chest radiograph was performed, which revealed a left-sided pneumothorax with complete collapse of the underlying lung, worse compared with that seen on the earlier chest radiograph. He was treated with chest tube drainage and recovered uneventfully. Retrospective questionnaire survey data obtained from 112 US Air Force aircrew who had experienced spontaneous pneumothorax identified 12 who had in-flight onset of symptoms.26 This study did not mention any fatalities related to pneumothorax. Fatality related to pneumothorax during air travel appears to be exceedingly rare. We identified only one case of fatal in-flight pneumothorax. Tiemensma and colleagues20 reported a sudden death occurring on an airplane in a 27-year-old woman with treated
pulmonary TB. She died of tension pneumothorax resulting from a ruptured bulla. Risk of Air Travel in Patients With Recent Pneumothorax or Thoracic Surgery The safety of air travel for patients with recent pneumothorax or thoracic surgery is still a matter of debate, largely due to the paucity of relevant data. In 1999, Cheatham and Safcsak43 reported 12 consecutive patients with traumatic pneumothorax (all involving motor vehicle accidents) expressing a desire to travel by air. Eleven patients flew 14 days after radiographic resolution of their pneumothorax, and all remained asymptomatic during flight. One patient flew 3 days after resolution of pneumothorax and developed respiratory distress in-flight with symptoms suggestive of a recurrent pneumothorax. Her symptoms resolved within a few hours of landing, and chest radiography was not performed. Based on these data, the authors concluded that commercial air travel appeared to be safe 14 days following radiographic resolution of a traumatic pneumothorax. Risk associated with air travel in patients who experienced post-transthoracic needle biopsy (TTNB)
Table 2—Risk of Air Travel-Associated Pneumothorax by Underlying Conditions Study/Year
Underlying Condition
No. of Study Subjects
Prevalence, %
Comments
Coker et al18/2007 Pollock-BarZiv et al23/2007 Taveira-DaSilva et al21/2009 Taveira-DaSilva et al21/2009 Taveira-DaSilva et al21/2009 Tam et al31/2011 Hoshika et al32/2012
Various lung diseases LAM LAM IPF Sarcoidosis Recent TTNB BHD
500 276 204 47 48 179 40
0 3.6 2.9 0 0 0 0
… 2.2% risk per flight 1.1% risk per flight … … … …
BHD 5 Birt-Hogg-Dubé; IPF 5 idiopathic pulmonary fibrosis; TTNB 5 transthoracic needle biopsy. See Table 1 legend for expansion of other abbreviations. 690
Commentary
pneumothorax was assessed in a telephone survey of 65 patients of whom 77% traveled by air within 4 days of the final postbiopsy chest radiograph, which demonstrated residual pneumothorax in more than onehalf of the patients.31 One of these patients flew with a chest tube and Heimlich valve used to manage an active air leak. Only one of 65 patients noted symptoms during flight consisting of increased chest pain and shortness of breath but none sought medical attention after the flight other than for removal of the chest tube in the aforementioned patient. These authors concluded that air travel within 2 weeks of TTNBrelated pneumothorax is safe even for those with radiographic evidence of residual pneumothorax.31 There are no data that directly relate to the risk of air travel-associated pneumothorax for patients who have undergone thoracic surgery. In 2010, Szymanski et al44 conducted a survey of 68 US thoracic surgeons for their recommendations regarding air travel by patients with postoperative pneumothorax. Forty-four percent of thoracic surgeons recommended that patients wait variable periods of time with a median of 7 days (range, 1-42 days) following complete resolution of pneumothorax prior to air travel, while 46% opined that it would be acceptable for individuals to fly despite residual pneumothorax (allowed more often for patients with , 5%, 5%-10%, and 10%-30% than those with 30%-50% pneumothorax), and 10% felt air travel to be contraindicated. Only one of the surveyed surgeons knew of an air travel-related complication among his patients (one patient who experienced thoracic pain during ascent). Based on this survey, symptomatic recurrence or exacerbation of postoperative pneumothorax appears to be rare while it is apparent that a wide variability exists among thoracic surgeons regarding their recommendations for air travel by patients after thoracic surgery. Air Travel With Chronic Pneumothorax Although pneumothorax is generally considered a contraindication for air travel, there are reports of patients with chronic pneumothorax who have flown uneventfully.21,45 Currie and colleagues45 described a 36-year-old man who had a persistent left-sided loculated pneumothorax for 4 years following staphylococcal pneumonia. After satisfactory results on a hypoxic challenge test (breathing 15% oxygen), the patient was deemed fit to fly and completed over a dozen flights including transatlantic routes without difficulty. As described previously, patients with LAM are at high risk of spontaneous pneumothorax (70%-80% lifetime risk), and some of these patients have chronic pneumothorax (Fig 1). In the study of 281 patients with LAM described by Taveira-DaSilva et al21 there were eight patients with chronic pneumothorax who journal.publications.chestnet.org
Figure 1. High-resolution CT scan of the chest of a 50-year-old female nonsmoker with pulmonary lymphangioleiomyomatosis demonstrating a loculated right pneumothorax that has been present for 1 y. Talc pleurodesis had been performed after two episodes of right-sided pneumothorax. She was asymptomatic during to and from transatlantic flights during the month following this CT scan study.
traveled by commercial airline to the study center. The pneumothoraces had been present prior to air travel for a mean duration of 2.2 years (range, 1-4.5 years), and two of these eight patients had previously undergone a pleurodesis. No change in volume of the pneumothorax was noted over a total observation period of 4.4 0.4 (mean SEM) years. No adverse consequences related to air travel occurred. Other Forms of Intrathoracic Barotrauma Associated With Air Travel Other forms of intrathoracic complications related to changes in barometric pressure during air travel have included pneumomediastinum, systemic air embolism, and bulla expansion with pulmonary hemorrhage. Three cases of pneumomediastinum associated with commercial flight were managed conservatively with uneventful resolution.46-48 Grossman and colleagues30 described 10 Israeli Air Force aviators in training who experienced pneumomediastinum caused by Valsalva maneuvers practiced during the basic training period (not flight-related). Two of these subjects had concomitant pneumothorax, one of whom required chest tube drainage. All subjects subsequently assumed flying duties without recurrence or other adverse consequences. Four cases of systemic air embolism during air travel in patients with pulmonary cystic lesions have been reported. A case of fatal air embolism caused by rupture of a large intrapulmonary bronchogenic cyst during air travel was described by Zaugg and colleagues.49 Two additional cases of systemic embolism CHEST / 145 / 4 / APRIL 2014
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during air travel have been associated with bullae. One of these patients died of the complication while the other suffered a unilateral hemiparesis.50,51 One remaining case consisted of cerebral air embolism caused by rupture of a CPAM resulting in a left hemiparesis and bulbar palsy.52 Chen and colleagues53 reported a 62-year-old man with emphysema and bullae who experienced recurrent hemoptysis during two consecutive commercial flights. His postflight chest radiograph revealed a bulla that had enlarged when compared with a preflight chest radiograph with a new air-fluid level. Wedge resection of the bulla revealed a thin fibrous wall with evidence of hemorrhage. Management Implications Current recommendations for air travel after pneumothorax or thoracic surgeries are largely extrapolated from anecdotal case reports and retrospective surveys and are outlined in Table 3.11,54 Guidelines from the Aerospace Medical Association published in 2003 suggest delaying air travel for 2 to 3 weeks following resolution of pneumothorax or after uncomplicated thoracic surgery.11 Pneumothorax is considered an absolute contraindication to air travel due to the risk of expansion during flight possibly resulting in tension pneumothorax.11 The most recent version of the British Thoracic Society guidelines regarding air travel for passengers with respiratory diseases (published in 2011) recommends a delay of 1 week after radiographic resolution of pneumothorax and preferably a 2-week delay for traumatic pneumothorax.54 One-week delay after resolution of pneumothorax is also advised for patients who have undergone thoracic surgery. Those with closed pneumothorax are advised not to travel on commercial flights with the rare exception of those with chronic loculated air collection who have undergone a careful clinical evaluation.54
There are several factors that need to be considered in determining the risk of pneumothorax in an individual patient, including type and severity of underlying lung disease, type of pneumothorax (spontaneous, traumatic, iatrogenic), prior history of pneumothoraces and treatments (chest tube, pleurodesis), and comorbidities (particularly cardiopulmonary disorders), as well as duration and route (eg, transoceanic) of air travel. Those with limited cardiopulmonary reserve will experience more severe consequences from a pneumothorax. Prior pleurodesis will decrease the risk of recurrent pneumothorax or limit the degree of lung collapse if pneumothorax recurs. Clearly, the decision to travel by air needs to be individualized, taking into account not only the aforementioned issues but also patients’ own perspectives and needs. Based on prior reports and our clinical experience, chronic loculated pneumothorax need not be an absolute contraindication to air travel. For patients with large intraparenchymal cystic lesions, for example, CPAM or bronchogenic cyst, elective resection prior to air travel should be considered. HRCT scanning of the chest with inspiratory and expiratory views may be helpful in some cases of cystic lung diseases to assess communication of the lesion with airways which would allow for equilibration of pressures. Management of suspected in-flight pneumothorax depends on the clinical status of the stricken passenger, available medical supplies, and the route of air travel. Supplemental oxygen should be provided and descent to the nearest airport, if available, needs to be considered. If signs of tension pneumothorax develop, urgent decompression and drainage will need to be undertaken using available supplies onboard. Emergency medical kits vary from airline to airline but usually include needles, IV catheters, and syringes. A dramatic account of managing tension pneumothorax in-flight using a scalpel, coat hanger, urinary catheter, and a bottle of water for underwater seal drain was provided by Wallace and colleagues.24
Table 3—Guidelines for Air Travel After Pneumothorax Study/Year Aerospace Medical Association Medical Guidelines Task Force11/2003
Ahmedzai et al54/2011
Air Travel Guidelines Pneumothorax is an absolute contraindication to air travel. Delay air travel for 2 or 3 wk after resolution of pneumothorax or uncomplicated thoracic surgery. Some stable patients with a persistent bronchopleural fistula can fly safely with a chest tube using a one-way Heimlich valve assembly. The presence of lung cysts or bullae is usually not a problem as long as the airways communicate with the abnormal air collection. Delay air travel for 7 d after resolution of pneumothorax. Delay air travel for 2 wk after resolution of trauma-related pneumothorax. Delay air travel for 7 d after full lung expansion in patients who have undergone thoracic surgery. Patients with closed pneumothorax should not travel on commercial flights (with very rare exceptions). Patients with LAM should be advised of the risk of pneumothorax with air travel and undergo evaluation if symptoms such as chest pain or shortness of breath are present.
See Table 1 legend for expansion of abbreviation. 692
Commentary
Conclusions Pneumothorax and other forms of intrathoracic barotrauma related to air travel are rare. Patients with cystic lung diseases, recent pneumothorax or thoracic surgery, and chronic pneumothorax need particular attention. The decision regarding air travel needs to be individualized by assessing risk based on specific disease-related issues and comorbidities while also taking into account patients’ preferences and needs. Additional data are needed to better inform decisions regarding air travel for patients at risk for pneumothorax. Acknowledgments Financial/nonfinancial disclosures: The authors have reported to CHEST the following conflicts of interest: Dr Cowl has received research contract funding in support of development of aviation oxygen delivery systems for pilots and passengers in aircraft. Drs Hu, Baqir, and Ryu have reported that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.
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Commentary
