2] The injection of 1 mL of air followed by 3 mL of 3% ethoxysclerol (air-block technique) during the Valsalva manoeuvre
caused an increase in intravascular pressure due to the presence of air and to the Valsalva manoeuvre
In children, it is possible to increase the CSA of IJV without the Valsalva manoeuvre
or other enhancement manoeuvres such as liver compression.
The Trendelenburg position, Valsalva manoeuvre
and abdominal compression have been suggested to increase the cross-sectional area (CSA) of the IJV and SCV (1-6).
The periosteum is loosely attached to the orbital bones, especially the orbital roof, which is the most common site for NTSOH development (6) The orbital veins are valveless, allowing increased jugular venous pressure to be transmitted to the veins in the subperiosteal orbital space, possibly causing rupture (2) Therefore, factors that increase venous pressures, such as vomiting, coughing and the Valsalva manoeuvre
may play a major role in NTSOH (1).
It must be stressed, however, that a Valsalva manoeuvre
is ill-advised in the event of venous air embolism--because of the risk, on its release, of paradoxical embolism (1,4).
This is called the Valsalva manoeuvre
and it works because air at cabin pressure is forced into the middle ear and sinuses.