Decompression Sickness

Since bubble formation is an uncontrolled process, they can develop anywhere in the body, common sites being the shoulders, elbows, knees, and ankles. In most cases of altitude decompression sickness, the person generally complains of joint pains ("the bends") in which shoulder is the commonest site. When large joints like elbows, shoulders, hips, wrists, knees and ankles are involved, the person complains of localized deep pain that can be mild to excruciating. It is seen that active as well as passive movement of these joints increases the pain. Sometimes the pain can be reduced by bending the joint to a more comfortable position. If the pain is caused due to altitude change, then it can occur immediately or sometimes later too.

Neurological symptoms of headache and visual disturbances are present in 10% to 15% of decompression sickness cases. Cutaneous symptoms are seen in 10% to 15% of cases. The patient may suffer from altered sensation of paraesthesia or hyperesthesia. Confusion, amnesia, seizures, unconsciousness and unexplained mood changes can be seen. The person complains of itching generally around the ears, face, neck, arms and upper torso. Weakness or paralysis of legs, incontinence of urine and stool may be present. The patient may complain of a feeling of tightening or bending in the abdominal region. Generalized malaise and unexplained fatigue are commonly seen. Nausea, vomiting, dizziness, vertigo, hearing loss and loss of balance are present due to involvement of the inner ear [16]. Diver may complain of altered sensations as if tiny insects are crawling on the skin. Skin appears mottled or marbled along with itching at different sites. Swelling of the skin along with pitting edema. Pulmonary decompression sickness ("the chokes") is rarely seen in divers and is all the more rare in aviators because of oxygen pre-breathing protocols being introduced. The person may even complain of dry persistent cough and shortness of breath.

There are no specific tests for decompression sickness; it is purely a clinical diagnosis. Most times, the treatment itself is the test, if the person improves when treated with hyperbaric oxygen, it invariably proves that the person was suffering from decompression sickness. When the patient’s history suggests involvement of diving, determine if the patient is suffering from any pressure-related injuries. Get the basic lab tests done and if you feel there is some change in mental state of the patient or he/she is in shock, a more detailed workup is called for.

Following tests should be done in case of change in mental status:

• Blood glucose level, full blood count
• Sodium, magnesium, calcium, and phosphorous levels
• Blood oxygen saturation
• Ethanol level and drug screen
• Carboxyhemoglobin level

To rule out shock following tests should be performed:

• Blood glucose level, full blood count
• Electrolytes and BUN level
• Creatinine levels, lactic acid
• Blood type and screen/cross
• Prothrombin time, activated partial thromboplastin time
• Carboxyhemoglobin level

Imaging studies like chest radiography, head CT scan and MRI can be done to rule out any other injury caused due to diving leading to present set of symptoms.

Each and every case of decompression sickness should be treated with 100% oxygen initially till hyperbaric oxygen therapy is made available. Generally, the "bends" and skin symptoms disappear during the descent from high altitude, but still these cases should be thoroughly evaluated. Hyperbaric oxygen therapy should be used in treating neurological symptoms, pulmonary symptoms, and mottled or marbled skin lesions if they develop within 10-14 days. It is seen that the recovery is faster when the oxygen is given within the first four hours of surfacing. The recompression therapy is more successful due to prompt administration of oxygen and decreases the number of recompression treatments needed later [17]. Fluids help in reduction of dehydration. It is a general practice to give aspirin in case of diving accidents for antiplatelet activity, provided the patient is not bleeding, but there is no data to support this practice [18]. Aspirin can mask the symptoms, hence should not be given routinely unless indicated. Cardiopulmonary resuscitation should be done if needed and needle decompression of chest should be performed if there is suspicion of tension pneumothorax. The person should be made comfortable and made to lie in supine position, or the recovery position if vomiting occurs [2]. Do not place the patient in Trendelenburg position as it increases the intracranial pressure and worsens the injury to blood-brain barrier [19].

The duration of recompression treatment depends on the severity of symptoms, the dive history, the type of recompression therapy used and the patient's response to the treatment. Treat the patient for nausea, vomiting, headache and pain. The general protocol that is used for treatment includes providing hyperbaric oxygen therapy with a maximum pressure equivalent to 60 feet (18 m) of seawater for a total time under pressure of 288 minutes, of which 240 minutes are on oxygen and the balance are air breaks to minimize the possibility of oxygen toxicity [20].

Early diagnosis and prompt treatment play a vital role in prognosis of decompression sickness. Decompression sickness when treated immediately with 100% oxygen, followed by recompression in a hyperbaric chamber, will help in maximum recovery in most of the cases with no long-term effects. Occasionally, decompression sickness can also lead permanent long-term injury.

Decompression sickness occurs due to a rapid decrease in ambient pressure which leads to the formation of bubbles of inert gases within tissues of the body. It can take place when one leaves a high-pressure environment, ascending from depth, or ascending to altitude, during free or assisted dives. It is seen in people involved with tunneling projects, in submarines during emergencies, and in breath-hold free diving, one can see the effects of decreased pressure too.

The occurrence of decompression sickness is rare. Studies suggest that around 2.8 cases per 10,000 dives suffer from decompression sickness. It is also seen that males are at 2.6 times greater risk than females. Approximately 1,000 US scuba divers are affected by decompression sickness per year [2]. Because of variability in reporting and collecting information, it is not easy to pen the exact statistics of diving-related injury in any mainstream medical journal publication. In order to improve the collection of this data, the divers alert network (DAN), based in North Carolina in the United States, functions as a center for medical information and referral service in case of diving-related injuries. The Divers Alert Network (DAN) formed "Project Dive Exploration" in 1999 so as to gather data on dive profiles and incidents. Between 1998 and 2002, 50,150 dives were recorded, of which 28 needed re-compressions. These included the incidences of arterial gas embolism (AGE) which were at the rate of about 0.05% [3] [4]. According to DAN, less than 1% of divers experience decompression sickness [5]. With changes in law and medical confidentiality becoming more stringent, it has become difficult to obtain these reports and much more difficult to follow them up in United States [6].

Generally, divers suffer from decompression sickness as they have breathed gas which is at higher pressure than the surface pressure because of the pressure of the surrounding water. There are two main factors that control the chances of diver suffering from decompression sickness, namely, the rate and duration of gas absorption under pressure and the rate and duration of outgassing on depressurization. The first parameter means that deeper or longer the dive, the more gas is absorbed into body tissues in higher concentrations than normal. The second parameter means that faster the ascent and shorter the interval between dives, the less time there is for absorbed gas to be offloaded safely through the lungs; the outcome being that these gases come out of solution too rapidly and form "microbubbles" in the blood.

When these gas bubbles are trapped in any of the organs, it is very uncomfortable, irrespective of their sizes. This holds true even for highly trained divers. The bubbles cause different reactions depending on their location. For example if a small bubble reaches the lungs, it can be simply filtered and exhaled, but if there is a right to left shunt, which is seen in case of a patent foramen ovale, then the bubbles bypass the natural filtering effect of the lungs and can reach the brain or other organs and could be fatal. It is believed that the nitrogen bubbles start as minute gas nuclei, present before the dive, and are not formed from supersaturation of the blood and tissues which are the foundation of large bubble formation [7]. All divers have bubbles [8], but only few of them suffer from decompression sickness. The probability of decompression sickness does not increase merely due to the presence of bubbles [9].

Microbubbles come into play before the formation of larger venous gas emboli [10]. These emboli can block the flow of blood in tiny blood vessels leading to infarcts. It is found that the dives and decompression stress increases the formation of microparticles from the vascular walls about 3.4 times and seem to trigger neutrophils along with their interaction with platelet membranes [8] [11]. The release of platelet microparticles specifically, can reflect the bubble-induced platelet aggregation. It can be the reason for coagulation and thrombosis, thereby interfering with blood flow [12]. As soon as the bubbles form, a foreign body interface is created to which platelets attach themselves [13]. Marked reduction in platelet count has been documented in case of severe decompression sickness. This depletion in platelet count can be used as a marker to determine the severity of injury [14] [15].

The most important measure that can be taken to prevent decompression sickness is always giving personal safety top most priority. Despite of taking all the safety measures, there are cases of decompression sickness. Following are the measures to be taken to minimize the chances of suffering:

• Breathing 100% FIO2 oxygen during the decompression stops may help prevent decompression sickness [21].
• Being active during the decompression stops may also decrease the likelihood of bubble formation [22] [23] [24].
• It is advisable to keep yourself hydrated before and after the dive as it has protective effects.
• The partial pressure of oxygen should be considered at the decompression stop depth in order to prevent toxicity.
• Always keep in mind to ascend slowly to prevent decompression sickness. The time for ascent has been increased for a 60-ft dive from 1 minute to a maximum of 7 minutes. It is advised to stop ascent at decompression stops to allow the exhalation of nitrogen gas, rather than it’s bubbling in the blood.
• Aerobic exercise has proved to have positive effects on human beings as it increases the uptake of oxygen. The most important thing is the timing of this exercise prior to the diving. Maximum benefits were seen when these exercises were done for 40 minutes at 20 hours and 24 hours, respectively, before the dive. It was found that it had marked long-lasting effects on the number and size of nitrogen bubble formation [25] [26] [27] [28].
• Breathing normobaric oxygen for 30 minutes prior to the dive decreases venous bubble formation for the subsequent dive and repetitive dives afterwards with no further pre breathing [29] [30].
• Studies show that antioxidants help in maintaining normal hemostasis, and prevent inflammatory responses that can help to stop the decompression sickness process from starting [31].

Decompression sickness, also known as Diver’s sickness, is a complex condition caused due to change in barometric pressure. It is generally an outcome of underwater diving, high altitude or aerospace related events [1]. This condition arises due to dissolved gases escaping the blood as bubbles inside the body when depressurized too rapidly.

Decompression sickness is generally seen when a person is exposed to sudden change in barometric pressure. It is commonly experienced by divers and people working in aerospace or high altitude related professions. Due to sudden change in pressure, the gases dissolved in the body form bubbles and when these bubbles get trapped they produce various signs and symptoms. Depending on the site of entrapment, the person presents with different cutaneous, neurological, pulmonary or musculoskeletal symptoms. There are various measures that can be taken to prevent this condition and if treated promptly the person can recover completely. It is best to follow the safety protocols so as to avoid this condition as far as possible. It is not a guarantee that you won’t suffer from decompression sickness even after taking all necessary precautions. One can make sure that you have all knowledge about it, including the first aid so as to avoid any long term damages. The diagnosis is purely clinical and improvement with recompression therapy is the only real confirmatory test.

1. Auten JD, Kuhne MA, Walker HM 2nd, Porter HO. Neurologic decompression sickness following cabin pressure fluctuations at high altitude. Aviat Space Environ Med. 2010 Apr. 81(4):427-30.
2. Thalmann ED. Decompression Illness: What Is It and What Is The Treatment?. Divers Alert Network. March–April 2004 
3. Pulley SA. Decompression Sickness. Medscape. 2007
4. Project Dive Exploration: Project Overview. Divers Alert Network. 2010.
5. Bennett PB. What me bent?. Alert Diver (Divers Alert Network). 1997. Vol 2:
6. United States of America. Health Insurance Portability and Accountability Act of 1996. Health Information Privacy. 
7. Blatteau JE, Souraud JB, Gempp E, Boussuges A. Gas nuclei, their origin, and their role in bubble formation. Aviat Space Environ Med. 2006 Oct. 77(10):1068-76.
8. Thom SR, Milovanova TN, Bogush M, Bhopale VM, Yang M, Bushmann K, et al. Microparticle production, neutrophil activation, and intravascular bubbles following open-water SCUBA diving. J Appl Physiol (1985). 2012 Apr; 112(8):1268-78.
9. Mollerlokken A, Breskovic T, Palada I, Valic Z, Dujic Z, Brubakk AO. Observation of increased venous gas emboli after wet dives compared to dry dives. Diving Hyperb Med. 2011 Sep;41(3):124-8.
10. Swan JG, Wilbur JC, Moodie KL, Kane SA, Knaus DA, Phillips SD, et al. Microbubbles are detected prior to larger bubbles following decompression. J Appl Physiol (1985). 2014 Apr; 116(7):790-6.
11. Thom SR, Yang M, Bhopale VM, Milovanova TN, Bogush M, Buerk DG. Intramicroparticle nitrogen dioxide is a bubble nucleation site leading to decompression-induced neutrophil activation and vascular injury. J Appl Physiol (1985). 2013 Mar 1; 114(5):550-8.
12. Pontier JM, Gempp E, Ignatescu M. Blood platelet-derived microparticles release and bubble formation after an open-sea air dive. Appl Physiol Nutr Metab. 2012 Oct; 37(5):888-92.
13. Philp RB, Freeman D, Francey I, Bishop B. Hematology and blood chemistry in saturation diving: I. Antiplatelet drugs, aspirin, and VK744. Undersea Biomed Res. 1975 Dec; 2(4):233-49.
14. Pontier JM, Blatteau JE, Vallée N. Blood platelet count and severity of decompression sickness in rats after a provocative dive. Aviat Space Environ Med. 2008 Aug. 79(8):761-4.
15. Pontier JM, Jimenez C, Blatteau JE. Blood platelet count and bubble formation after a dive to 30 msw for 30 min. Aviat Space Environ Med. 2008 Dec; 79(12):1096-9.
16. Doolette, David J; Mitchell, Simon J. Biophysical basis for inner ear decompression sickness. J App Physiol. 2003; 94 (6): 2145–50.doi:10.1152/japplphysiol.01090.2002 (inactive 2015-01-12). PMID 12562679. Retrieved 30 September 2014. Accessed on 12.7.15
17. Longphre, John M; denoble, Petar J; Moon, Richard E; Vann, Richard D; Freiberger, John J. First aid normobaric oxygen for the treatment of recreational diving injuries. Undersea and Hyperbaric Medicine. 2007; 34 (1): 43–49. Retrieved 25 May 2010. Accessed on 12.7.15
18. Bessereau J, Coulange M, Genotelle N, Barthélémy A, Michelet P, Bruguerolle B, et al. Aspirin in decompression sickness. Therapie. 2008 Nov-Dec; 63(6):419-23.
19. De Watteville G. A critical assessment of Trendelenburg's position in the acute phase after a diving accident. Schweiz Z Sportmed. 1993 Sep; 41(3):123-5.
20. U.S. Navy Supervisor of Diving. Chapter 20: Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism. U.S. Navy Diving Manual (PDF). SS521-AG-PRO-010, revision 6. Volume 5. U.S. Naval Sea Systems Command. P. 41. 2008
21. Blatteau JE, Hugon J, Gempp E, Castagna O, Pény C, Vallée N. Oxygen breathing or recompression during decompression from nitrox dives with a rebreather: effects on intravascular bubble burden and ramifications for decompression profiles. Eur J Appl Physiol. 2012 Jun; 112(6):2257-65.
22. Jankowski LW, Tikuisis P, Nishi RY. Exercise effects during diving and decompression on postdive venous gas emboli. Aviat Space Environ Med. 2004 Jun; 75(6):489-95.
23. Dujic Z, Valic Z, Brubakk AO. Beneficial role of exercise on scuba diving. Exerc Sport Sci Rev. 2008 Jan; 36(1):38-42.
24. Dujic Z, Palada I, Obad A, Duplancic D, Bakovic D, Valic Z. Exercise during a 3-min decompression stop reduces postdive venous gas bubbles. Med Sci Sports Exerc. 2005 Aug; 37(8):1319-23.
25. Wisløff U, Brubakk AO. Aerobic endurance training reduces bubble formation and increases survival inrats exposed to hyperbaric pressure. J Physiol. 2001 Dec 1; 537(Pt 2):607-11.
26. Dujic Z, Duplancic D, Marinovic-Terzic I, Bakovic D, Ivancev V, Valic Z, et al. Aerobic exercise before diving reduces venous gas bubble formation in humans. J Physiol. 2004 Mar 16; 555(Pt 3):637-42.
27. Loset A Jr, Mollerlokken A, Berge V, Wisloff U, Brubakk AO. Post-dive bubble formation in rats: effects of exercise 24 h ahead repeated 30min before the dive. Aviat Space Environ Med. 2006 Sep; 77(9):905-8.
28. Dujic Z, Obad A, Palada I, Ivancev V, Valic Z. Venous bubble count declines during strenuous exercise after an open sea dive to 30 m. Aviat Space Environ Med. 2006 Jun; 77(6):592-6.
29. Castagna O, Gempp E, Blatteau JE. Pre-dive normobaric oxygen reduces bubble formation in scuba divers. Eur J Appl Physiol. 2009 May; 106(2):167-72.
30. Bessereau J, Genotelle N, Brun PM, Aboab J, Antona M, Chenaitia H, et al. Decompression sickness in urban divers in France. Int Marit Health. 2012; 63(3):170-3.
31. Madden LA, Laden G. Gas bubbles may not be the underlying cause of decompression illness - The at-depth endothelial dysfunction hypothesis. Med Hypotheses. 2009 Apr; 72(4):389-92.

• Small rightsided fat-containing Bochdalek hernia
  User29949, 2018-09-04 16:16