Diving and hyperbaric Unit, University hospitals of Geneva, Geneva, Switzerland.
Corresponding author: Dr Pierre Louge, Diving and hyperbaric Unit, University hospitals of Geneva, Geneva, Switzerland,
Diving Hyperb Med. 2023 Mar 31;53(1):51-54. doi: 10.28920/dhm53.1.51-54.
This study aimed to determine the lowest possible atmospheric pressure in the 111-152 kPa (1.1-1.5 atmospheres absolute [atm abs]) range that would require the patients to equalise their ears, allowing an effective sham for a 203 kPa (2.0 atm abs) hyperbaric exposure.
We performed a randomised controlled study on 60 volunteers divided into 3 groups (compression to 111, 132 and 152 kPa (1.1, 1.3, 1.5 atm abs) to determine the minimum pressure to obtain blinding. Secondly, we applied additional blinding strategies (faster compression with ventilation during the fictitious compression time, heating at compression, cooling at decompression) on 25 new volunteers in order to enhance blinding.
The number of participants who did not believe they had been compressed to 203 kPa was significantly higher in the 111 kPa compressed arm than in the other two arms (11/18 vs 5/19 and 4/18 respectively; P = 0.049 and P = 0.041, Fisher's exact test). There was no difference between compressions to 132 and 152 kPa. By applying additional blinding strategies, the number of participants who believed they had been compressed to 203 kPa increased to 86.5 %.
A compression to 132 kPa, (1.3 atm abs, 3 metres of seawater equivalent) combined with the additional blinding strategies of forced ventilation, enclosure heating and compression in five minutes, simulates a therapeutic compression table and can be used as a hyperbaric placebo.
本研究旨在确定在 111-152kPa（1.1-1.5 个绝对大气压[atm abs]）范围内的最低可能气压，以使患者需要平衡耳朵，从而为 203kPa（2.0atm abs）高压暴露提供有效的模拟。
我们对 60 名志愿者进行了一项随机对照研究，将其分为 3 组（分别压缩至 111、132 和 152kPa（1.1、1.3、1.5atm abs），以确定获得盲目所需的最低压力。其次，我们在 25 名新志愿者身上应用了额外的盲目策略（在虚构的压缩时间内进行通风的更快压缩、压缩时加热、减压时冷却），以增强盲目性。
在压缩至 111kPa 的手臂中，有更多的参与者认为自己没有被压缩至 203kPa，与其他两支手臂相比差异有统计学意义（分别为 11/18 比 5/19 和 4/18；P=0.049 和 P=0.041，Fisher 确切概率法）。在 132 和 152kPa 的压缩之间没有差异。通过应用额外的盲目策略，有 86.5%的参与者认为自己被压缩至 203kPa。
在 132kPa（1.3atm abs，3 米海水当量）下的压缩，结合强制通风、封闭加热和 5 分钟内压缩等额外的盲目策略，可以模拟治疗性压缩台，并可作为高压的安慰剂。
