What is the first action an EMT should take when caring for an unresponsive patient who was exposed to chlorine gas?

For an unresponsive patient who has been exposed to chlorine gas, the most appropriate initial action is taking manual spine motion restriction of the head and neck and performing the jaw-thrust maneuver. This approach demonstrates proper attention to the potential for spinal injuries that might accompany the exposure, especially if the patient has collapsed or fallen.

When working with unresponsive patients, especially in toxic environments, prioritizing airway management while minimizing spinal movement is crucial. The jaw-thrust maneuver is specifically designed to secure the airway without compromising spinal alignment, which is critical in cases where traumatic injuries are suspected.

This choice is especially relevant in the context of chlorine gas exposure, where pulmonary irritants may affect the airway's responsiveness and function. By ensuring that the airway is maintained and protected, you can facilitate further interventions, such as ventilation if necessary, while avoiding exacerbating any possible spinal injuries.

The other options primarily focus on assessing respiratory status or determining circulation but may not adequately prioritize the need for airway management in an unresponsive patient.