There are a number of reasons to provide mechanical ventilation to a Patient. Diaphragmatic Injury or paralysis would be one. Most decisions to ventilate are due to Respiratory Acidosis (Low Ph, high PACO2.) Protection of the airway is also common, common during surgical procedures. Phrenic Nerve damage would prevent the Diaphragm from being innervated and without very quick intervention, (ambuing or ventilation) the Patient would expire in just a few moments. Phrenic Nerve damage sucks, because it is permanent, about as bad as being a Quadriplegic or a Paraplegic.
Of course people are ventilated for other reasons such as non responsiveness or severe trauma, and more.
I am not immediately skeptical of the venom possibility, as snake poisons do result in rapid onset of blood clotting and the prothrombin times must be monitored closely, particularly in the case of A-Fib or other arrhythmias.
BookmarQed!