Pulmonary interstitial emphysema following spirometry in CPFE syndrome.

Interstitial emphysema (IE) is an uncommon lung disease associated with barotrauma, and is seen almost exclusively in neonates with respiratory distress syndrome. It is caused by the invasion of gas into the pulmonary interstitial space surrounding the bronchovascular bundles due to sudden changes in lung volumes and transpulmonary pressure. Secondary changes in the alveolar sacs cause the alveolar septa to rupture.1 The difference in pressure, always greater in the alveolar compartment than in the mediastinum, increases the flow of gas bubbles to the mediastinal compartment, producing pneumomediastinum. The effect of gravity causes the bubbles to rise to the neck, producing subcutaneous emphysema. We report the case of a 65-year-old man, former smoker (30 pack-years), with upper lobar emphysema and lower lobar fibrosis (combination of pulmonary fibrosis and emphysema [CPFE]). He presented in the hospital with worsening dyspnea at rest. On admission, he had intense tachypnea (32 breaths per minute) due to severe hypoxemia (38.5 mmHg) and a heart rate of 90 beats per minute. Images from a high resolution computed tomography (HCRT) scan of the chest performed 1 year previously (not attached) showed significant involvement of the lung architecture with patterns of emphysema and concomitant fibrosis. Clinical diagnostic procedures were completed with full lung function tests (LFT) and spirometry. Approximately 4 hours after spirometry, another chest HRCT was performed to compare the resulting morphological functional data with the previous examination. Unexpectedly, the repeat HRCT showed a significant amount of air in the mediastinal compartment (pneumomediastinum), and small gas bubbles were seen in the pulmonary interstitial space surrounding the bronchovascular bundles, attributed, in the absence of pneumothorax, to IE (Fig. 1). The patient had no signs of worsening chest pain or dyspnea after the HRCT or in the following hours. After 10 days of complete bed rest, another HRCT was performed, showing almost complete reabsorption of the air in the mediastinum and surrounding the bronchovascular bundles. Episodes of this kind occurring after a routine spirometry are very rare, even in patients with a clinical history of CPFE. Apart from acute barotrauma in neonatal or pediatric patients, particularly in premature babies with respiratory distress syndrome treated with mechanical ventilation or patients with surfactant deficiency,2 few cases of IE have been described in the literature. This acute