Why do scuba divers increase their risk of decompression sickness when ascending to altitude soon after a dive?

Increasing altitude soon after a dive can heighten the risk of decompression sickness because the dive tables, which help divers calculate safe ascent times and surface intervals, are based on the assumption of sea-level conditions. When divers ascend to altitude, the atmospheric pressure decreases rapidly compared to the pressure at sea level. This reduction in pressure can lead to a quicker formation of nitrogen bubbles in the body that had been dissolved during the dive.

As divers are exposed to lower pressure environments, nitrogen that has been absorbed in the tissues during the dive can start to come out of solution, forming bubbles. This is the fundamental principle behind decompression sickness; if divers do not adhere to the recommended surface intervals or attempt an ascent to altitude too soon after diving, their risk of these bubbles forming and causing harm increases significantly.

Additionally, while other factors related to altitude and gas exchange can play a role, the primary concern stemming from changed pressures highlights the critical importance of following prescribed safety measures based on dive tables for ascents.