The SAR folks, trained as Wilderness First Responders, considered that this might be a flu-like illness or pneumonia, but the lack of a fever suggested otherwise. It didn't appear the patient was dehydrated or had CO poisoning. Considering possible life-threats, and suspicious about the story of the unexpected fatigue, they listened to the lungs and tested for ataxia.
The patient initially wanted to continue to walk, and asked for a horse to help him leave the field; however, he agreed to the helicopter after the WFRs had him listen to his lung sounds. He then insisted on walking to the landing zone, which concerned the WFRs who had been taught that physical exertion with HAPE could make matters much worse. They were able to start him on oxygen at 4 l/m via cannula from a small (D) tank they carried, which they knew would only last an hour at that flow rate. This helped him to walk, albeit slowly.
The patient was able to walk to the meadow and arrived simultaneously with the sound of the rotors. This stoical patient had the flight medics wondering about the urgency of the evacuation until they listened to his lungs and used their pulse oximeter, which registered at 74%. The evacuation was uneventful. In the hospital the patient was diagnosed and treated for HAPE. He was admitted overnight and released in the morning when his lungs were clear of fluid.