Abstract
Introduction
Surgical spacesuits are in widespread use. Only one previous study (JBJS 1998) has assessed the quality of the environment within the space suit. They demonstrated that surgical spacesuits could allow re-breathing of carbon dioxide (CO2). However, they had no control group and performed a vigorous exercise protocol which may have been an unfair test. The design of helmet systems has also evolved in the last decade. We have conducted the first investigation into CO2 levels inside the modern space suit. There is a Workplace Exposure Limit for inspired CO2 as determined by the Health and Safety Executive (UK), which is 0.506kPa. We wondered whether re-breathing of CO2 in space suits would lead to inspired CO2 which breaches this level.
Methods
We used an anaesthetic room gas analyzer via nasal cannulae to measure inspired (ICO2) levels in 12 healthy volunteers. Readings were taken while wearing a surgical space suit with the fan on high and low settings. These were compared with a normal surgical facemask. Readings were repeated on mild exertion to simulate the effort of performing arthroplasty surgery.
Results
[Frequency of ICO2 >0.5kPa (12 subjects)]
Discussion
Despite the design modifications, modern space suits allow re-breathing of CO2. This is more marked with exertion and with low fan settings where ICO2 can exceed workplace limits. This may account for symptoms of headache and drowsiness reported after a prolonged period in the suit during arthroplasty surgery. We recommend the use of high fan settings at all times.
