In this issue of CHEST (see page 191),
Ferreyra et al report their findings using partial liquid ventilation
(PLV) in an animal model. This is a cutting-edge technology, and the
article makes for fascinating reading. The perfluorocarbon fluid used
in this technique is hyperdense, having a specific gravity of 1.92.
This attribute poses a potential hazard for human patients, owing to
the elevated hydrostatic pressure that this extremely dense liquid is
able to exert.
Consider a case wherein PLV might be employed for an adult patient in
the erect posture. In order to illustrate the pattern of distribution
of the instillate, we are going to employ the modified roentgenogram
shown in Figure 1.
This posteroanterior chest radiograph was obtained in preparation for a
CT scan, for which horizontal lines are automatically scribed onto the
radiograph at 1-cm intervals. As perfluorocarbon fluid is instilled
into the airway, it will percolate into the most dependent regions of
the lung. Ferreyra et al continued to instill perfluorocarbon into the
endotracheal tube until it reached the level of the teeth of the
(animal) subject. If this methodology were duplicated in an erect human
subject, the pattern of perfluorocarbon distribution would resemble
that shown in Figure 2.
We have overdrawn a line at each of the centimeter markers, beginning
at the lateral costophrenic sulcus, upward to the level of the main
stem bronchi. This vertical distance is observed, in this case, to be 8
cm. The posterior sulcus lies below this level, but we have chosen the
lateral sulcus as our zero point because it is easier to visualize on
the chest radiograph. Perfluorocarbon would rise to the 8-cm level
within the lungs, at which point additional fluid would rise within the
endotracheal tube. This additional instillate would be prevented from
entering the portion of each lung overlying the 8-cm scribe line
because the newly loculated gas lying above each hilum would have no
route of egress.