Presentation
The dog was under anesthesia for thoracic radiographs to check placement of an esophageal tube.
Patient Data
In the first radiograph, positive pressure was not applied by the anesthesia personnel. The dog is in expiratory phase of respiration. The diaphragm is positioned cranially and partially overlies the heart. The lungs are more opaque and the volume is decreased, especially in the caudal lung lobes. There is alveolar pattern in the right cranial lobe and the ventral right middle lobe. The thoracic limbs are positioned partially over the cranial thorax.
The second radiograph was performed under positive pressure (10-20 mm Hg) with the pop-off valve of the machine closed. The diaphragm is positioned caudally and has a flattened shape. The caudal lung lobes have more volume than the previous radiogaph, and are much more radiolucent. The cranial lobar bronchus is dilated and the trachea is wider. The alveolar pattern in the right cranial and middle lung lobes has resolved.
Case Discussion
These are extreme examples of the respiratory phases with an animal under anesthesia. In the conscious animal, the degree of hypoinflation and hyperinflation are less, but still clinically significant. Lesions may be hidden in a hypoinflated thoracic radiograph. Time the radiographic exposure to peak inspiration for each view of the thorax for best results.
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