A new method of quantification of atelectatic areas: a pilot study

Background and goal of study

This study reports of a new way to verify the recruitment of atelectatic areas with a mobile CT, in patients who are served superimposed high frequency jet ventilation (SHFJV) [1].

Material and methods

After institutional approval four patients, three male and one female with a mean age of 52 years (ranging 21 to 83 years) received SHFJV for four hours by a prototype of a new electronic jet ventilator named ALEXANDER 1. Blood gas analyses were taken every half hour during the whole study period. A thorax CT (mobile CT, Philips Tomoscan M, Netherlands), was taken of every patient before and after the period of ventilation with the possibility of 3D reconstruction. The ventilated areas of each thoracic CT-picture were digitally remastered and volumetricly measured by a serial scan of the lungs (matrix 512 to 512, zoom factor 1.4; slicethickness 1.0 cm, pitch 1.0 cm, trash hold of -400 to -1000 HE). A high resolution CT (HR-CT) was performed of every patient's lungs (slicethickness 0.2 cm, pitch 1.5 cm, same trash hold and same matrix as in the serial scan) before and after jet-ventilation, to detect any alteration of the parenchyma or changing of (he diameters of the bronchi. Data export was performed via DICOM III on a Philips Easy Vision 2,1.2. Sun Sparc Station 5.

Results and discussion

The situation of every lung improved. The average amount of the improvement of the ventilated areas were 329 cm, which represented an average increase of 11.7%. In analogy of these values, we saw that the PaO₂ measurements of the arterial blood gas analyses were improving too. The average increase of the PaO₂ value amounted to 40.4% within the period of SHFJV, meaning that the improvement of the ventilation (recruitment of the atelectatic areas) leads to a better oxygenation. Regarding the HR CT, we saw no dilatation of the bronchi, but a decrease of the atelctatic areas.

Conclusions

The improvement of the ventilation and oxygenation can be umpirely objectified with this new method. This possibility improves the critically regarded situation of the SHFJV.