Received 12 December 2015; accepted 18 January 2016; published 21 Janaury 2016
Decompression sickness, a dreaded condition for divers all over the world, is one of the four major pathologies associated with diving apart from Barotraumas, Pulmonary Oedema, and toxic effects of gases on increased partial pressure   . It is caused by the release of inert gas bubbles (usually nitrogen) in tissues, after ambient pressure is reduced  - . Decompression sickness is traditionally classified as type I and type II in 1960 for compressed air workers and later adopted for diving and altitude exposure with some modifications  . Type I DCS refers to “pain only” without the involvement of central nervous system and manifests in mild symptoms such as musculoskeletal or joint pain, and skin rashes, while type II involves the presence of bubbles in Central Nervous System (CNS), thus has more serious implications and could result in paraplegia, loss of bladder control or even death  . Most frequent symptoms of decompression sickness are shoulder pain, tingling, vertigo, and skin rashes  . First aid treatment for DCS is to administer one hundred percent oxygen and definitive treatment is recompression to increased pressure  .
Sport of Self Contained Underwater Breathing Apparatus (SCUBA) diving is relatively new to India but has shown tremendous growth in past few years and likely to grow further. However, recompression chamber facility in Andaman and Nicobar Islands, which provides Hyperbaric Oxygen Therapy (HBOT) to the DCS patients, is available only with Clearance Diving Unit (CDU) of Naval Diving Unit Port Blair. Any civilian cases are first presented to G.B. Pant Hospital, Port Blair and then referred to CDU, if required.
Andaman and Nicobar Islands, with many active dive centres, are becoming a popular dive destination among the divers around the world  . Thus, the number of divers at risk for decompression sickness is also increasing; yet no scientific studies have been performed on decompression sickness incidents in the islands. Present study is the first insight into the DCS incidents that are reported in these islands. An attempt has also been made to have a rough estimate of the divers’ participation and average number of dives performed per year on the islands.
2. Materials and Methods
2.1. Study Design
Present study is a retrospective analysis of routine data from a decompression chamber.
2.2. Data Collection
Data on Decompression Sickness case reports were retrieved from the Clearance Diving Unit (CDU) of Naval Diving Unit, Port Blair and G.B. Pant Hospital, Port Blair.
Since no written records of total number of participation or number of dives performed per year are available with any of the dive centres, an approximate estimation was reached by enquiring various dive centre owners and managers.
2.3. Data Analysis
Individual reports were studied and classified on the bases of incident date, age, nationality, gender of the patient, type of DCS, treatment table used, and outcome of the treatment.
2.4. Ethical Considerations
Present study was reviewed and approved by DS College Ethics Committee in accordance with the Code of Ethics of the World Medical Association (Declaration of Helsinki) for humans and animals.
There were more than 16 dive centres in Andaman and Nicobar Islands and the list was growing every year. On an average one lakh divers participated in the sport per year, majority of them were not certified divers but Discover SCUBA Divers (DSDs). About 125000 dives were performed per year on these islands.
Nine patients were given Hyperbaric Oxygen Therapy (HBOT) for DCS in the islands, from 1st January 2011 to 31st June 2015. The frequency of DCS incidents on these islands was about 0.2/10000 dive persons. Majority of the cases were type II DCS, most common symptoms were tingling in left hand and numbness in left leg. All the patients were presented to the hospital at least six hours after the onset of the symptoms. Royal Navy table 61 or 66 was used to treat the patients [Figure 1 & Figure 2].
All the nine patients recovered completely without any residual symptoms, after receiving HBOT [Table 1].
Frequency of DCS per thousand dives/divers varies all over the world due to myriad reasons. Major problem in calculating DCS incident rate per dive is incomplete records on total number of divers, and dives throughout the world.
Most organized source of data information on divers and diving incidents is from a few organizations, such as Divers Alert Network (DAN) America, Divers Emergency Service (DES) Australia, and American Academy of Underwater Science (AAUS) North America   . DAN launched Project Dive Exploration (PDE) in 1995 to collect and interpret data on incidents in recreational diving   .
Figure 1. Royal navy treatment table 61 (source: londondivingchamber.co.uk).
Figure 2. Royal navy treatment table 66 (source: londondivingchamber.co.uk).
Table 1. Incidents of DCS in Andaman and Nicobar Islands during Jan 2011 to June 2015.
According to DAN report 2009, frequency of DCS in dive volunteers, with 150739 captured dives in the year 2007, was 2.3 DCS incidents per 10,000 dives and out of all incidents of DCS, fifty percent were type I DCS  .
Incidents of DCS reported in Andaman and Nicobar Islands were fewer than reported elsewhere in the world, except in South Africa [Table 2]. This could be due to the lack of reporting to the hospital by the patients in these areas. In South Africa and India, majority of the data on DCS were extracted from hyperbaric centres, where people are usually referred only in case of severe incidents, while in case of minor incidents people might administer self treatment and do not go to hospital. Our study also indicates higher reporting of type II DCS incidents (66.67% of the total DCS cases) than comparatively milder type I DCS incidents.
It is indicated that some patients of apparently less serious type I DCS are going back home without HBOT. This could lead to undesired manifestations of the illness, later in their lives, since long term studies have not been performed on injured sport divers. Symptoms sometimes disappear even without treatment and sometimes they improve before markedly worsening  . Thus, definitive treatment is still strongly recommended.
DCS patients respond well to HBOT with complete or substantial relief in majority of cases, even in case of late presentations   . Present study also reinforces the success of Hyperbaric Oxygen Therapy with full recovery of all the patients.
Andaman and Nicobar Islands have lower incident rate of Decompression Sickness as compared to many other areas of the world. One of the possible reasons could be underreporting of apparently less severe DCS I incidents by the patients. Since long term effects of untreated DCS have not been studied, and patients respond well to Hyperbaric Oxygen Therapy, awareness among divers is required to encourage them to undergo treatment, even in case of apparently less severe DCS.
・ Since studies on long term effects of DCS on recreational divers have not been performed, divers should be made aware of the possible effects of untreated DCS later in life.
・ In present study, HBOT proved a complete success in treating DCS patients, thus divers should be encouraged to undergo therapy, irrespective of the severity of symptoms.
Authors are thankful to the Clearance Divers Unit of the Naval Diving Unit and G.B. Pant Hospital, Port Blair, Andaman and Nicobar Islands for providing the necessary information for this study.
Table 2. Frequency of decompression sickness around the world.
The authors declare that they have no competing interests.