Final answer:
The best treatment for the construction worker is to apply high-concentration oxygen and rapidly transport him to the nearest medical facility. His symptoms suggest a serious heat-related illness requiring immediate medical attention, and while awaiting transport, he should be monitored and kept as cool as possible.
Step-by-step explanation:
The symptoms provided suggest that the patient at the construction site is likely suffering from a heat-related illness, possibly heat exhaustion or the onset of heat stroke. The patient has been working in high temperatures, is speaking incoherently, has collapsed, and exhibits signs such as low blood pressure, a rapid pulse, and a high respiratory rate. His damp shirt with salt rings indicates significant sweating and possible electrolyte loss.
The initial step in treatment should be to call for rapid medical transport while providing care. While you wait for the ambulance, place the patient in a position of comfort, continue to cool him with the vehicle's air conditioning, and monitor his vital signs. The use of high-concentration oxygen, if available, can help improve oxygen delivery to tissues, which may be compromised due to circulatory changes.