Cronjé Frans J, Meintjes W A Jack, Bennett Peter B, Fitchat Surita, Marroni Alessandro, Hyldegaard Ole
Division of Community Health, Department of Interdisciplinary Health Sciences, Faculty of Health Sciences, University of Stellenbosch, Stellenbosch, South Africa.
Undersea Hyperb Med. 2011 Jan-Feb;38(1):41-8.
Recreational divers are introducing "deep stops" at half the depth (HD-DS) to reduce the risk of spinal DCS with only Doppler evidence to support it. Therefore this research was designed to show the effect of an HD-DS on spinal DCS manifestations by evaluating whether: (1) air diving-induced spinal DCS could be produced in awake, freely moving rats at 3.5-6.0 atm abs (350-600 kPa); and (2) whether the introduction of an HD-DS reduced spinal DCS in such a model. Fifty-one female, Wistar rats (221 to 450 g) underwent one-hour compression at 350 to 600 kPa with seven minutes of decompression with/without a five-minute DS (HD-DS / No-DS). Animals were observed for three hours. Outcomes were classified as: (1) asymptomatic; (2) breathing difficulties; (3) paralysis/weakness; (4) immobility; or (5) death. Eight animals, exposed to 385 kPa air breathing for 60 minutes followed by a three-staged decompression of 7.5 minutes, remained asymptomatic. The profile is known to produce spinal DCS in anesthetized rats. Eleven animals were then used to determine the threshold for DCS: 500 kPa. A total of 14 animals were compressed to 550 kPa (Group 1). Group 1-A (n = 8) No-DS; Group 1-B (n = 6) HD-DS; 18 were compressed to 600 kPa (Group 2). Group 2-A (n = 8) No-DS; Group 2-B (n = 10) HD-DS.
(1) 385 kPa protocol did not produce visible DCS manifestations in awake rats. The binomial probability of no DCS in this sample size is 0.002818 for the proportion expected from a published report. The binomial probability of no fatalities is 0.005346). (2) No animals developed spinal DCS when assessed by visible paralysis/weakness or immobility, so no difference could be shown. Group 1-A: two deaths; two breathing abnormalities; four asymptomatic. Group 1-B: all asymptomatic. Difference recorded for breathing difficulties (p = 0.0483); none for fatalities (p = 0.2024). Group 2 mortality was 55% (n = 10). Group 2-A and 2-B: no difference for death (p = 0.6063) or breathing problems (p = 0.2084).
This model could not evaluate HD-DS for the prevention of spinal DCS in rats.
休闲潜水者在半程深度引入“深度停留”（HD-DS）以降低脊髓减压病风险，目前仅有多普勒证据支持这一做法。因此，本研究旨在通过评估以下内容来显示HD-DS对脊髓减压病表现的影响：（1）在3.5 - 6.0绝对大气压（350 - 600千帕）下，空气潜水诱发的脊髓减压病能否在清醒、自由活动的大鼠中产生；（2）在此模型中引入HD-DS是否能减少脊髓减压病。51只雌性Wistar大鼠（体重221至450克）在350至600千帕下进行1小时加压，并在有/无5分钟深度停留（HD-DS / 无深度停留）的情况下进行7分钟减压。对动物观察3小时。结果分为：（1）无症状；（2）呼吸困难；（3）麻痹/虚弱；（4）不动；或（5）死亡。8只动物暴露于385千帕空气呼吸60分钟，随后进行7.5分钟的三阶段减压，仍无症状。已知该方案会在麻醉大鼠中产生脊髓减压病。然后使用11只动物确定减压病阈值：500千帕。总共14只动物被加压至550千帕（第1组）。第1组 - A（n = 8）无深度停留；第1组 - B（n = 6）HD-DS；18只动物被加压至600千帕（第2组）。第2组 - A（n = 8）无深度停留；第2组 - B（n = 10）HD-DS。
（1）385千帕方案在清醒大鼠中未产生明显的减压病表现。对于该样本量，根据已发表报告预期比例，无减压病的二项式概率为0.002818。无死亡的二项式概率为0.005346）。（2）通过可见的麻痹/虚弱或不动评估时，没有动物发生脊髓减压病，因此无法显示差异。第1组 - A：2只死亡；2只呼吸异常；4只无症状。第1组 - B：全部无症状。记录到呼吸困难差异（p = 0.0483）；死亡无差异（p = 0.2024）。第2组死亡率为55%（n = 10）。第2组 - A和第2组 - B：死亡（p = 0.6063）或呼吸问题（p = 0.2084）无差异。
该模型无法评估HD-DS对预防大鼠脊髓减压病的作用。
