Postmortem Pulmonary Angiography And Bronchography

Satisfactory injection can be achieved only with inflated lungs. Therefore, careful removal of the lungs and sealing of accidental lacerations of the pleura is essential.

PULMONARY ARTERIOGRAPHY Barium-gelatin mixtures are the preferred media. Because the viscosity of the gelatin preparations depends on many factors, the optimal concentration of gelatin will vary and has to be tested. For further details, see Chapter 12. The pulmonary arteries can be injected in situ by introducing a 13-gauge needle just above the pulmonary valve. This technique is particularly useful when tumors, adhesions, or other pathologic conditions prevent the removal of intact lungs. It may be necessary, however, to place the cadaver for some time in a refrigerator to allow the gelatin to set; the lungs can then be removed without causing much leakage from minor lacerations.

The preferred method is pulmonary arteriography on isolated lungs (Fig. 4-7). Tubing is tied with glass or plastic cones into the pulmonary artery and the bronchus, respectively. The lung is inflated through the bronchus with air or carbon dioxide at a pressure of approx 20 mm Hg (the lung should attain its normal volume). The barium-gelatin medium is warmed to about 60°C and injected into the pulmonary artery of the inflated lung at a pressure of about 70-80 mm Hg. Again, some experimentation may be necessary because required injection pressures vary depending on the viscosity of the medium, temperature, types of syringes, and other factors. With the methods described here, we have consistently filled the peripheral pulmonary artery branches (Fig. 4-8), down to vessels with an internal diameter of about 60 pm. The study of even smaller vessels requires very low-viscosity gelatin mixtures or noncon-solidating contrast media. For an average-sized lung, about 150 mL of medium is needed. The injection takes 5-10 min. When the vascular tree is filled, the pressure increases suddenly; hence this endpoint cannot easily be missed. The lung should be kept warm during the injection so that the gelatin does not set too quickly. The techniques described here are for adult lungs but they also can be applied to infant lungs (12).

PULMONARY VENOGRAPHY AND LYMPHANGIOGRAPHY The injection technique for the venography is basically similar to that for pulmonary arteriography. In situ filling can be achieved by tying glass cones into these veins at their connection to the left atrium. The same technique may be used on heart-lung blocks or on isolated lungs. In the last instance, the procedure is facilitated if a part of the left atrium has been left attached to the lung so that glass or plastic tubes or cones are easier to tie into the veins. Injection pressures may vary between 20 and 70 mm Hg.

For lymphangiographic studies, stained sodium tritrizoate (see Chapter 15) is injected into pleural lymphatics with a no. 30 lymphangiography needle while the lung is kept at an inflation pressure of about 18 cm H2O (13).

BRONCHIAL ARTERIOGRAPHY Similar to the pulmonary vessels, the bronchial arteries can be injected in situ but this method is not recommended because multiple aortic branches must be tied first and because the origin of the bronchial arteries is not constant. In isolated lungs, the bronchial arteries usually can be cannulated at the posterosuperior aspect of the main bronchus. A 30-gauge polyethylene catheter is tied into the isolated bronchial artery or arteries. The lung is then inflated with carbon dioxide or air, and the contrast medium (see "Pulmonary Arteriography") is injected through the catheter. The injection pressure is 150 mm Hg. The end point of the injection has been discussed in the previous section. Bronchial arteriograms clearly show these vessels (Fig. 4-9). After bron-chopulmonary anastomoses have opened, bronchial arterio-grams may also show segments of pulmonary arteries.

BRONCHOGRAPHY High-viscosity barium-gelatin mixtures can be used but clinical contrast media give better results. Ideally the contrast medium should be instilled while the lung is expanded in a vacuum chamber.

Fig. 4-8. Slice of perfusion-fixed lung with advanced destructive centrilobular emphysema. Note pulmonary artery branches containing white contrast medium (arrows). A barium sulfate-gelatine mixture was used as contrast medium. Photographed specimen is under water.
Fig. 4-9. Bronchial arteriogram.
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