Pontier J-m, Jimenez C, Blatteau J-E. Blood platelet count and bubble formation after a dive to 30 msw for 30 min. Aviat Space Environ Med 2008; 79:1096–9.Introduction: Previous human studies reported that platelet count (PC) is decreased following decompression. Platelet aggregation and adherence to the bubble surface has been demonstrated in severe decompression sickness (DCS). The present study was designed to clarify the relationship between post-dive changes in blood PC and the level of bubble formation in divers. Methods: There were 40 healthy experienced divers who were assigned to 1 experimental group (N = 30) with an open-sea air dive to 30 msw for 30 min in field conditions and 1 control group (N = 10) without hyperbaric exposure. Bubble grades were monitored with a pulsed Doppler according to the Spencer scale and Kissman integrated severity score (KISS). Blood samples for red blood cell counts (RBC), hematocrit (Hct), and PC were taken 1 h before and after exposure in two groups. Results: None of the divers developed any signs of DCS. In two groups, the results showed significant increase in RBC count and Hct related with hemoconcentration and no change in PC. Divers with a high KISS score (39 ± 5.8; mean ± SD) presented a significantly more pronounced percent fall in PC than divers with a lower KISS score. We found a significant correlation between the percent fall in PC after a dive and the bubble KISS score. Discussion: The present study highlighted a relationship between the post-dive decrease in PC and the magnitude of bubble level after decompression. Our primary result is that the post-dive decrease in PC could be a predictor of decompression severity after diving.