A toddler who abruptly loses voice while eating and then struggles to breathe is choking on aspirated food. The block is purely mechanical, sitting in the larynx or trachea, so the entire treatment logic is about getting the object out fast rather than treating swelling or infection.
Among the offered choices, only one is a non invasive bedside maneuver that can be done in seconds. Abdominal thrusts, the Heimlich maneuver, squeeze the diaphragm upward and spike the pressure beneath the obstruction, popping the bolus out much like a cork. This is precisely why it is taught as the first action for any conscious choking victim.
The remaining options fail the timing and appropriateness test. Surgical airways such as cricothyroidotomy or tracheostomy are escalation steps used only after non surgical attempts do not work and the patient is deteriorating; they are not the opening move. Humidified oxygen helps mucosal conditions, not a solid object wedged in the airway. So the correct next step remains the abdominal thrust technique.
\[\boxed{\text{Heimlich maneuver}}\]