For our treks in Nepal it is the client’s responsibility to have adequate emergency health insurance that includes trekking at higher altitudes and helicopter evacuation.
Travelers who take adventure trips are a whole different breed of traveler. Adventure travel is typically physically demanding and often fraught with personal danger, rustic accommodations, and unfamiliar foods consumed in remote locations. Adventure travel insurance plans are those that include coverage for adventurous activities like hang gliding, diving, skiing, and mountaineering (to name just a few), so it’s important for adventure travel tourists to purchase a plan that includes coverage for their planned activities.
Ref: http://www.travelinsurancereview.net/adventure-travel-insurance/