Final answer:
The appropriate response to a 2-year-old patient experiencing a sudden drop in heart rate and mottled coloration while intubated would be to manually ventilate with a resuscitation bag and 100% oxygen to improve oxygenation and potentially stabilize the heart rate.
Step-by-step explanation:
In response to the signs of drastically reduced heart rate and mottled coloration in a 2-year-old unconscious patient who is intubated and receiving mechanical ventilation, the most appropriate action would be to use a resuscitation bag to provide manual ventilation with 100% oxygen.
These symptoms indicate a potentially life-threatening situation where the child may not be receiving adequate oxygenation, and immediate resuscitative measures are necessary. Increasing the ventilator rate, tidal volume, or positive end-expiratory pressure (PEEP) does not directly address the acute issue of bradycardia and poor perfusion that the mottled skin suggests.
Therefore, using a resuscitation bag to manually ventilate the patient allows for more immediate control and assessment of the patient's ventilation and oxygenation status, and the provision of 100% oxygen can help to quickly improve oxygen saturation and potentially stabilize heart rate.