If you fall sick during the Everest Base Camp hike, you should consult your trek leader and try to descend to a lower height and continue your journey once you feel better. If your condition doesn’t move forward, you can call for an emergency helicopter clearing to an advanced medical facility office in Kathmandu. You can also attempt the other things if you’re experiencing altitude sickness: breathe in additional oxygen, increase the air pressure, get down in the high passes rapidly, and rest at the same altitude.