What emergency assistance (e.g. air rescue) is available, how are they contacted, and what are the estimated response times?

In cities, town and tourist destinations, there are hospitals / clinics and ambulance service relatively close by and very easy to contact. Throughout Vietnam the number to call is 115. In remote & mountainous areas, an emaergency may become difficult due to poor communication and bad roads. In many of the National parks where the majority of our adventures take place there has been first aid and evacuation training and aid is at the most a half-day by foot away. Worst-case scenario, the group would have to walk the patient out ourselves. There are many resources to do this effectively. In Vietnam, air service is very hard to come by for military and resource reasons. Because the areas we adventure too are so close to tourist centers and main roads, it would not warrant air evacuation