The effect of helium on the immune system ex vivo

Various experimental studies have shown protective effects of helium inhalation
on ischemia/reperfusion damage in myocardial and cerebral tissue. Based on
these findings, we want to investigate whether an extended episode of helium
inhalation has any effects on the immune response.

The aim of this study is to evaluate whether a 30-minute episode of helium
breathing in humans affects the ability of the immune system to respond to ex
vivo stimulation in whole blood taken from healthy volunteers.

Explorative study with a cross-over design, using the principle of balanced
assignment. In this combined clinical and laboratory study, researchers
investigating immuneparameters in the laboratory will be blinded. Blinding of
patients is not possible, due to changes in voice after inhalation of
heliumgas.

Volunteers will be studied during two separate days, in which they will breath
heliox or room air for 30 min using a special, sealed mask.

All volunteers have to undergo two experimental *cycles*: one with heliox
inhalation and one with inhalation of normal room air. Between the experimental
cycles there will be an episode of at least two weeks. Each cycle includes one
whole day in the AMC (± 8 hours) and blood donation the next day in the
morning. On the day of participation, a physical examination (cardiopulmonary
system) will be performed by a physician. Twelve hours before the start of the
experimental cycle, the volunteer is not allowed to drink coffee or other
caffeine containing drinks, or to smoke. Doing any kind of sports on the night
before the experimental day in the AMC, or the night before the second day is
also prohibited.
On experimental day, the volunteers have to stay in the research room in which
circumstances will be as standardized as possible. Until after the third time
point of blood sampling, the volunteers have to stay seated in a chair and they
will be offered time to read. After that, they will receive a lunch that will
be the same for every volunteer. After time point 3, the volunteers are allowed
to walk around but they have to stay within the AMC.
Volunteers will undergo helium inhalation, with concentration 79% helium and
21% oxygen. Until now, no relevant cardiovascular, pulmonary, allergic or other
side effects of helium inhalation have been reported. A gas mixture of helium
and oxygen (heliox) is already used for clinical purposes, such as patients
with severe asthma or for children undergoing mechanical ventilation.
Volunteers will experience a transiently higher voice after helium inhalation.
Each blood withdrawal will be taken from a separate puncture site performed by
a physician with extensive experience in this field, such as an
anesthesiologist. For this study, the blood sampling cannot take place through
a venous access line. In total, the volunteer gives 126 ml for one experimental
cycle (2 days) and a total of 252 ml for the whole experiment (4 days).