Dry diving as a human model of pulmonary microembolization

Aim The human model of pulmonary embolism is currently unavailable. The objective of this study was to evaluate whether venous inert gas lung embolization after diving simulation is a model of pulmonary embolism. Methods Twelve recreational divers underwent two single air compressions, each in different post-compression posture, in the chamber to 30 m/40 min bottom time with standard decompression and ascent rates. Cardiopulmonary variables and precordial bubble grade were measured in sitting or lying supine before and 40, 70 and 100 min after the respective compression. Results The volume of airways decreased post-compression in supine (24%, p<0.01), as well as in sitting posture (28%, p<0.05). As a sign of lung embolization, the alveolar dead space increased significantly only in supine posture (from 27 to 65 mL, p<0.05). Transcutaneous arterial oxygen tension decreased post-compression from 11, 8 to 9, 5 kPa in supine posture (p<0.01) and from 11, 3 to 9, 72 kPa in sitting posture (p<0.005). Minute ventilation and breathing frequency increased significantly only in sitting posture. Cardiovascular depression was suggested from reductions in systolic blood pressure (both postures), heart rate and pulse pressure(sitting posture) and from apparent, but not significant decreases in cardiac output (both postures). Most of the signs were most pronounced at 40 minutes post-compression and persisted at 100 min post-compression.Conclusion Small, transient post-compression lung embolization by inert gas bubbles induces some of the cardiopulmonary signs of pulmonary embolism, especially if the diver is lying after the compression.