Aerospace, Decompression Illness


Article Author:
Richard de la Cruz


Article Editor:
Jeffrey Cooper


Editors In Chief:
Jeffrey Cooper


Managing Editors:
Avais Raja
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Khalid Alsayouri
Frank Smeeks
Kristina Soman-Faulkner
Radia Jamil
Patrick Le
Sobhan Daneshfar
Anoosh Zafar Gondal
Saad Nazir
William Gossman
Pritesh Sheth
Hassam Zulfiqar
Navid Mahabadi
Steve Bhimji
John Shell
Matthew Varacallo
Heba Mahdy
Ahmad Malik
Mark Pellegrini
James Hughes
Beata Beatty
Nazia Sadiq
Hajira Basit
Phillip Hynes
Tehmina Warsi


Updated:
12/14/2018 12:59:01 PM

Introduction

While many think of decompression sickness secondary to diving, it also occurs after exposure to reduced environmental pressure and can occur in aviation as well. High altitudes can expose flight crews and individuals to the risk of decompression sickness. The general pathophysiology is similar to decompression sickness and involves gas, such as nitrogen, forming bubbles in tissue, which is responsible for the symptoms ranging from relatively minor symptoms to profound neurologic manifestations.[1][2][3]

Traditionally, decompression sickness is categorized as type 1, referring to skin changes and milder symptoms such as joint pain, or type 2, referring to more severe symptoms involving the neurologic, cardiac, and pulmonary systems. Some difficulties with that naming system have led to a better system that refers to the patient’s involved organ systems, such as musculoskeletal, cutaneous, neurologic, or cardiopulmonary subtypes.

Etiology

Decompression sickness that occurs with high-altitude exposure such as in aviation can happen through various mechanisms. The first is by exposure to a high-altitude chamber such as is used by military organizations. The second is through exposure to altitude without proper aircraft or suit pressurization. Commercial aircraft typically have a pressurized cabin; however, failure of that system or noncommercial air travel can lead to decompression sickness. A third mechanism is due to the pressure difference as can occur with an individual who was to scuba dive and then fly a commercial flight in a short period. The sudden exposure to a cabin pressure of around 7000 feet may cause decompression sickness. It is important to note that decompression sickness still can occur in individuals who follow standard decompression procedures before flying.[4][5]

Epidemiology

It is difficult to determine accurate rates of decompression sickness secondary to aviation and altitude exposure, as there have been reports of potential cases that are not characterized as altitude-exposure decompression illnesses. One publication noted 63 cases of individuals who experienced decompression sickness from flying after a dive over a 4-year period. With that noted, in one study involving 2001 subjects, the rate of people experiencing any form of decompression illness following altitude exposure from an altitude chamber was 40%. Of individuals experiencing decompression sickness, the majority of symptoms were joint pain (72.8%) or paresthesias (12.6%). Only 3.4% of people who experienced decompression sickness secondary to altitude in that study experienced symptoms that were classified as neurologic or respiratory. Only 1.3% of individuals experienced recurrent symptoms. The studies revealed a low rate (3.4%) of individuals experiencing neurologic or respiratory symptoms though did not include paresthesias, which have been noted to be a neurologic symptom by others. When considering neurologic symptoms that include a headache and paresthesia, the rates may be closer to 14% to 34% of cases.[6][7]

Individuals flying a military or private flight may be exposed to high-altitude situations predisposing them to a decompression illness. Approximately 30% of the time flying between 18,000 ft and 30,000 ft results in symptoms with a much higher percentage when flying at altitudes between 30,000 ft to 45,000 feet.

Aside from straightforward factors such as altitude or time from the last dive, other factors have been noted to affect the risk of decompression sickness. Gender has not been found to be a risk factor despite the suggestion that females have a higher risk of developing decompression sickness during menses, with risk decreasing associated with time since last menses. Other risk factors include having a higher body mass index and being less physically fit.

Pathophysiology

Decompression sickness occurs as a result of gas bubbles, referred to as evolved gas emboli, forming in tissues that can exert pressure on nerves, block blood vessels, and interact with proteins. This can result in a varying severity of symptoms that include pain and skin changes as well as neurologic and cardiopulmonary symptoms. The gas emboli form as a result of inert gas (nitrogen) that is dissolved in tissues at ground level, becomes supersaturated at altitude, and develops into bubbles. One interesting factor is that not all tissue dissolves gas at the same rate, with fat dissolving at least fivefold the nitrogen dissolved in blood.

Secondary effects also can occur, which may in part be responsible for some of those with delayed development of certain symptoms. Bubbles can cause endothelial damage, resulting in a capillary leak, platelet activation; and deposition is possible, as are other processes such as leukocyte-endothelial adhesion.

History and Physical

The history of a patient presenting with decompression sickness will often involve some aspect of recent diving, flight, non-commercial air travel, or altitude chamber use. The important thing to recognize is that not all individuals will understand the importance of these aspects of their history, so they may not volunteer it.

Specific symptoms patients may complain about depend on the location of the bubbles, with the most common being musculoskeletal symptoms presenting as joint pain that can be mild to severe. Patients may also complain of skin changes, headaches, paresthesias, and respiratory issues. A particular skin manifestation of decompression sickness is cutis marmorata, also called livedo reticularis, which is the result of skin tissue damage caused by gas bubbles forming during decompression. More profound presentations, while less common, can occur with altered mentation and severe neurologic or cardiopulmonary presentations possible. If neurologic signs or symptoms occur after exposure to altitude, consider decompression sickness.

Histories of rapid ascent in aviation or recent diving followed by altitude exposure are key components to a patient's history.

Important aspects of the physical exam include complete skin examination, complete neurological examination, careful lung and cardiac examination, and full evaluation of the joints.

Evaluation

Evaluation of a patient with suspected decompression illness relies primarily on history and physical examination since there are no specific tests to make the diagnosis. With that said, diagnostic testing to rule out other causes for a patient’s presentation may be necessary as decompression sickness can mimic many possible disease processes. For instance, in the hypoxic patient following a flight, the need to evaluate for other possible cardiac and pulmonary pathology may be warranted or an in a patient with a neurologic presentation, radiographic imaging of the brain may be indicated.[8][9]

Treatment / Management

Treatment and management may vary depending on the grade/form of decompression sickness and the treating facility or organization. [10]

Oxygen will wash inert gas from the lungs. A gradient is formed from tissues to lungs, allowing for the removal of the inert gas by both perfusion and diffusion.

The United States Air Force has published information on using ground-level 100% oxygen therapy for 2 hours following type-1 decompression sickness that occurs at altitude if it resolves upon descent. They used hyperbaric oxygen for more severe cases and for cases of type-1 decompression sickness that did not resolve. They have reported a high success rate with this treatment, with 94% of subjects not requiring further hyperbaric therapy. Further, the majority of individuals (95.6%) experiencing minor symptoms were manageable with ground-level 100% oxygen and had their symptoms resolved before starting any form of therapy, so consider this form of therapy in an individual with minor symptoms that have resolved before starting therapy. It is important to note that those results were from an altitude-chamber study since the high frequency of rapid onset symptoms at altitude is not always expected.

In more severe cases, hyperbaric recompression is accomplished in hyperbaric chambers. The recompression while breathing 100% oxygen will increase the tissue to lung gradient previously mentioned and decrease the bubble volume (Boyle’s Law), leading to the resolution of inert gas tissue bubbles. Standard recompression protocols are modeled after the United States Navy tables.

Decompression sickness in aviation most commonly is seen following flights in nonpressurized aircraft, in flights with cabin pressure fluctuations, or in individuals who fly after diving. Cases also have been reported after the use of altitude chambers. The manifestations are treated as SCUBA diving decompression sickness is treated, primarily with ground level or hyperbaric oxygen. These are relatively rare clinical events, and the clinician must consider this diagnosis in the proper historical setting. Practitioners should know where local hyperbaric chambers are located. The Divers' Alert Network (DAN) is an excellent source of information. 

Enhancing Healthcare Team Outcomes

Decompression sickness in aviation most commonly is seen following flights in nonpressurized aircraft, in flights with cabin pressure fluctuations, or in individuals who fly after diving. Cases also have been reported after the use of altitude chambers. The manifestations are treated as SCUBA diving decompression sickness is treated, primarily with ground level or hyperbaric oxygen. These are relatively rare clinical events, and the clinician must consider this diagnosis in the proper historical setting. Practitioners including nurse practitioners should know where local hyperbaric chambers are located. The Divers' Alert Network (DAN) is an excellent source of information.


Interested in Participating?

We are looking for contributors to author, edit, and peer review our vast library of review articles and multiple choice questions. In as little as 2-3 hours you can make a significant contribution to your specialty. In return for a small amount of your time, you will receive free access to all content and you will be published as an author or editor in eBooks, apps, online CME/CE activities, and an online Learning Management System for students, teachers, and program directors that allows access to review materials in over 500 specialties.

Improve Content - Become an Author or Editor

This is an academic project designed to provide inexpensive peer-reviewed Apps, eBooks, and very soon an online CME/CE system to help students identify weaknesses and improve knowledge. We would like you to consider being an author or editor. Please click here to learn more. Thank you for you for your interest, the StatPearls Publishing Editorial Team.

Aerospace, Decompression Illness - Questions

Take a quiz of the questions on this article.

Take Quiz
A 36-year-old pilot went flying after scuba diving for 3 hours, at an altitude of 20,000 feet and then started having pain in his right knee. He describes the pain as a dull ache and not made worse with movement. Upon landing, the pain in the knee resolved but he started to feel numbness in his feet and thoracoabdominal pain. Which of the following is true for this patient?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
Which of the following is responsible for the development of decompression illness?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
What are the most common presenting signs and symptoms of decompression sickness?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
What is the treatment for decompression illness?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
What is livedo reticularis in relation to decompression illness in aviation?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up

Aerospace, Decompression Illness - References

References

Shi L,Zhang YM,Tetsuo K,Shi ZY,Fang YQ,Denoble PJ,Li YY, Simulated High Altitude Helium-Oxygen Diving. Aerospace medicine and human performance. 2017 Dec 1     [PubMed]
Zhang JX,Berry JR,Beckstrand DP, Explosive Decompression with Resultant Air Gas Embolism in a Fourth Generation Fighter at Ground Level. Aerospace medicine and human performance. 2016     [PubMed]
You're the Flight Surgeon. Aerospace medicine and human performance. 2016     [PubMed]
Alea K, Identifying the Subtle Presentation of Decompression Sickness. Aerospace medicine and human performance. 2015 Dec     [PubMed]
Hundemer GL,Jersey SL,Stuart RP,Butler WP,Pilmanis AA, Altitude decompression sickness incidence among U-2 pilots: 1994-2010. Aviation, space, and environmental medicine. 2012 Oct     [PubMed]
Auten JD,Kuhne MA,Walker HM 2nd,Porter HO, Neurologic decompression sickness following cabin pressure fluctuations at high altitude. Aviation, space, and environmental medicine. 2010 Apr     [PubMed]
Bendrick GA,Ainscough MJ,Pilmanis AA,Bisson RU, Prevalence of decompression sickness among U-2 pilots. Aviation, space, and environmental medicine. 1996 Mar     [PubMed]
Murad MH,Altayar O,Bennett M,Wei JC,Claus PL,Asi N,Prokop LJ,Montori VM,Guyatt GH, Using GRADE for evaluating the quality of evidence in hyperbaric oxygen therapy clarifies evidence limitations. Journal of clinical epidemiology. 2014 Jan     [PubMed]
Moon RE,Sheffield PJ, Guidelines for treatment of decompression illness. Aviation, space, and environmental medicine. 1997 Mar     [PubMed]
Hart GB, Treatment of decompression illness and air embolism with hyperbaric oxygen. Aerospace medicine. 1974 Oct     [PubMed]

Disclaimer

The intent of StatPearls is to provide practice questions and explanations to assist you in identifying and resolving knowledge deficits. These questions and explanations are not intended to be a source of the knowledge base of all of medicine, nor is it intended to be a board or certification review of Certified Hyperbaric Technologist (CHT). The authors or editors do not warrant the information is complete or accurate. The reader is encouraged to verify each answer and explanation in several references. All drug indications and dosages should be verified before administration.

StatPearls offers the most comprehensive database of free multiple-choice questions with explanations and short review chapters ever developed. This system helps physicians, medical students, dentists, nurses, pharmacists, and allied health professionals identify education deficits and learn new concepts. StatPearls is not a board or certification review system for Certified Hyperbaric Technologist (CHT), it is a learning system that you can use to help improve your knowledge base of medicine for life-long learning. StatPearls will help you identify your weaknesses so that when you are ready to study for a board or certification exam in Certified Hyperbaric Technologist (CHT), you will already be prepared.

Our content is updated continuously through a multi-step peer review process that will help you be prepared and review for a thorough knowledge of Certified Hyperbaric Technologist (CHT). When it is time for the Certified Hyperbaric Technologist (CHT) board and certification exam, you will already be ready. Besides online study quizzes, we also publish our peer-reviewed content in eBooks and mobile Apps. We also offer inexpensive CME/CE, so our content can be used to attain education credits while you study Certified Hyperbaric Technologist (CHT).