The VRI is an imaging modality that records energy generated by the vibrations of the lungs during respiration cycle and creates an image that can be viewed dynamically or sequentially. Yigla et al reported that the left quantitative lung data (QLD) were significantly higher than right QLD. The reason for this was thought to be caused by anatomical differences. As the left main bronchus is smaller and is more sharply angulated at the carina, the air flow of left lung might be more turbulent and provoke more vibration energy. We speculate that if this hypothesis is correct, heliox that convert turbulent flow to laminar flow would weaken left lung vibration energy.
Breath sounds were recorded from back sensors of VRIxp for twenty normal male subjects during air inhalation or heliox (O2 20% and He 80%) inhalation. We analyzed quantitative lung data (QLD) with air and heliox in each subject.
In twenty normal male subjects, QLD of the left lung inhaling air tended to be higher than the right, but not significantly. We could not observe the reduced left QLD with heliox (QLD% rt; 44.0 ± 8.6 lt; 56.0 ± 8.6, P < 0.05). There were no significant differences of left QLD with air inhalation and heliox inhalation. When we applied heliox to two patients with airway stenosis, VRI findings were more synchronized with heliox than with air.
Since left QLD was stronger than right QLD even with heliox, increased turbulence caused by anatomical differences were not thought to be the reason for the difference between left QLD and right. However, heliox inhalation could improve asynchrony of VRI dynamic image in two patients with airway stenosis. In these cases heliox seemed to reduce air flow turbulence and make air flow smoother. We plan to investigate the effect of heliox on VRI image of various respiratory diseases.
Heliox is useful for airway stenosis.
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