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• Recompression in water with air supply at shallow depth cannot be superior to breathing pure oxygen on surface
  yavuz aslan
  Published on: 15 July 2016

• Published on: 15 July 2016

  Recompression in water with air supply at shallow depth cannot be superior to breathing pure oxygen on surface

  • yavuz aslan, medical doctor
  • Other Contributors:
    • samil aktas

  Sir,

  We read with interest the article named 'Prevention and treatment of decompression sickness using training and in-water recompression among fisherman divers in Vietnam' that was published in Injury Prevention 2016 February issue. We want to share our opinion about some parts of the article, especially in three subjects.

  It was mentioned that, the aim of the study was to investigate the impact o...

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  Sir,

  We read with interest the article named 'Prevention and treatment of decompression sickness using training and in-water recompression among fisherman divers in Vietnam' that was published in Injury Prevention 2016 February issue. We want to share our opinion about some parts of the article, especially in three subjects.

  It was mentioned that, the aim of the study was to investigate the impact of training programmes run over a period of 3 years, focusing on preventing DCS by reducing unsafe diving practices and treating DCS by means of IWR, in the last sentence of introduction. So we understood that the main subject of the study is forcing fisherman divers to make safe dives resulting in decrease in DCS and also to treat urgently with IWR if disease occurs. Therefore this education only involves lowering DCS and treating with IWR. But it is remarked as "Since implementing IWR training, annual mortality and morbidity incidence rates due to neurological DCS were reduced in our pilot sample" in second sentence of discussion. It was understood from the article, prior to 2009, annual mortality due to diving was estimated 4?1 cases per 1000 fisherman divers and annual incidence of DCS was 8?2 cases. Between 2009 and 2012 fatality rate dropped 1 per 1000 divers and annual incidence of DCS dropped 2?1 per 1000 divers. However we know it is unlikely to have a mortality rate of four cases in every eight DCS cases before 2009 and also one fatal case within two cases of DCS between 2009 and 2012. Many studies was reported before about this issue, in one of them Xu et al. showed nine deaths of 5278 consecutive DCS cases with a incidence of 0.17% in a decade (1). It seems suspicious that one in a two cases DCS mortality rate as mentioned in the article. Probably the mortality reasons must be other than DCS, e.g. drowning, nitrogen narcosis and diving related accidents, before 2009 and also between 2009 and 2012 in these dive sites. We found it very challenging; two days 10 subjects IWR training courses reduced annual mortality rates due to the DCS.

  On the other hand, in the treatment of DCS, there appears three main goals; [1] immediate reduction in bubble size, [2] to increase the washout of inert gas and [3] to provide oxygen delivery to the tissues to restore normal functions (2). If we put an order in terms of treatment efficacy; standart recompression treatment in chamber (oxygen, 45-60 feet), IWR with oxygen, breathing oxygen at surface, IWR with air at working depth (fisherman divers' traditional IWR), IWR with air (Clipperton Protocol, 9 m.) had superiority each other, respectively in the treatment of DCS. It is well known that, in the absence of a hyperbaric chamber treatment, IWR with oxygen of course superior to breathing oxygen at surface in DCS. Known risks of IWR are drowning, applying difficulties, hypothermia and disability to transfer patient to chamber because of being underwater. It has been shown that IWR with air at 9 meters has no significant benefit in DCS; also authors mentioned in the article IWR with air is useless which the fisherman divers used to do traditionally. Nevertheless authors advised to divers apply IWR with air at nine meters, which is the last choice in treatment of DCS but they did not mention exactly why divers should follow this protocol. If it is done with oxygen it should be helpful but not with air. According to our knowledge IWR with air should not be performed, if it is to be done deep treatment protocols must be chosen, not at shallow depth like nine meters (3).

  The last point we want to take attention is that only eight of 24 DCS patients have been treated with oxygen, the rest were treated with air. Unfortunately the number of divers, which were treated with oxygen, is very low. However, two of eight of these patients (%25) started with oxygen but continued with air, because the cases were not able to breathe from a second stage regulator. In our opinion, if the rate (%25) is really in high ranges like this, there could be given educations about using hoses without second stage regulator.

  Declaration of conflicting interests: The authors declared no conflicts of interest with respect to the authorship and/or publication of this letter. Funding: No author or related institution has received any financial benefit for this letter.

  References 1. Xu W1, Liu W, Huang G, Zou Z, Cai Z, Xu W. Decompression illness: clinical aspects of 5278 consecutive cases treated in a single hyperbaric unit. PLoS One. 2012;7(11):e50079. 2. Diving and Subaquatic Medicine, Fifth Edition. Carl Edmonds, Michael Bennett, John Lippmann, Simon Mitchell. 2015. p. 167 3. 6th ed. USA: U.S. Navy Diving Manual, 2008

  Conflict of Interest:

  None declared

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  Conflict of Interest:
  None declared.

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