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Vestibular bends

Discussion in 'Decompression Theory' started by Mark Powell, Feb 10, 2005.

  1. Mark Powell

    Mark Powell Scuba Media & Publications

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    Dr Deco,

    Do you know of any research into the location of bubbles formed during a vestibular bend?

    I know that initially it was thought that the bends were occuring in the semi circular canals but I also know that there is some thought that they occur in the cerebellum.

    Has there been any definitive research been done on this?
     
  2. Dr Deco

    Dr Deco Medical Moderator Staff Member

    # of Dives: I just don't log dives
    Location: Issaquah [20 miles east of Seattle], Washington.
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    Hello Mark:

    In Situ, Organ Bubbles

    When I looked into this, I was surprised to find that the obvious answer, i.e., bubbles in the fluid (endolymph) of these organs contains bubbles when decompressed, was not demonstrated to be true. There is some evidence of bubble formation by McCormick et al. [references below], but they are so old that I do not have any reprints.

    The paper by Landolt et al. seems to place most of the blame on vascular bubbles although the techniques used would not have allowed for the actual visualization of the gas phase since too much time had elapsed before dissection.

    Arterialization

    This more recent paper of Cantais, Louge, et al.[below] makes a case for the culprit being our old “friend” the PFO. Otic DCS, as contrasted with barotraumas of the ear, is more a problem of deep diving.

    Summary of the Cantais E, paper

    • OBJECTIVE: We investigated the role of right-to-left shunt with standardized transcranial Doppler ultrasonography in a large population of divers referred for symptoms of decompression illness.
      PATIENTS: Patients were 101 consecutive divers with clinical evidence of decompression illness and a control group of 101 healthy divers. The degree of right-to-left shunt was defined as major if the number of high-intensity transient signals in the middle cerebral artery was >20.
      MEASUREMENTS AND RESULTS: Of the 101 divers presenting with decompression illness, transcranial Doppler detected a right-to-left shunt in 59 (58.4%), whereas control subjects demonstrated a right-to-left shunt in 25 cases (24.8%). When a right-to-left shunt was detected, the right-to-left shunt was major in 12 of 25 patients in the control group and in 49 of 59 patients in the decompression illness group. Within the decompression illness group, the proportion of major right-to-left shunt was 24 of 34 in the cochleovestibular subgroup, 13 of 21 in the cerebral decompression illness subgroup, ten of 31 in the spinal decompression illness subgroup, and two of two in the subgroup of divers with Caisson sickness.
      CONCLUSION: Based on our results, we conclude that major right-to-left shunt was associated with an increased incidence of cochleovestibular and cerebral decompression illness, suggesting paradoxical embolism as a potential mechanism.

    Dr Deco :doctor:

    References :book3:

    Cantais E, Louge P, et al. Right-to-left shunt and risk of decompression illness with cochleovestibular and cerebral symptoms in divers: case control study in 101 consecutive dive accidents. Crit Care Med. 2003 Jan;31(1):84-8.

    Landolt JP, Money KE, Topliff ED, Nicholas AD, Laufer J, Johnson WH.J Appl Pathophysiology of inner ear dysfunction in the squirrel monkey in rapid decompression.Physiol. 1980 Dec;49(6):1070-82.

    McCormick JG, Holland WB, et al. Sudden hearing loss due to diving and its prevention with heparin. Otolaryngol Clin North Am. 1975 Jun;8(2):417-30.

    McCormick JG, Philbrick T, Holland W, Harrill JA. Diving induced sensori-neural deafness: prophylactic use of heparin and preliminary histopathology results.
    Laryngoscope. 1973 Sep;83(9):1483-501.
     
  3. BigJetDriver

    BigJetDriver Great White Rest in Peace ScubaBoard Supporter

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    Doc,

    In re your report above, that's great information, and very thought provoking. Thanks for researching and posting that!

    Rob Davie
     
  4. Mark Powell

    Mark Powell Scuba Media & Publications

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    Hi Dr Deco,

    I was surpised that there was so little research on this. Thanks for digging up the paper by Cantais, Louge, et al, I'll have a look at it.

    Thanks for taking the time to look into it.

    Regards
     

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