Final answer:
A child presenting with severe respiratory distress should receive supplemental oxygen, inhaled bronchodilators, possibly systemic corticosteroids.
Step-by-step explanation:
The child with tachypnea, wheezing, inability to speak more than a few words at a time, lethargy, and an SpO2 less than 90% requires immediate medical management for a likely severe asthma exacerbation or other serious respiratory condition. These interventions aim to stabilize the patient's breathing, reduce inflammation, and improve gas exchange.
Immediate administration of high-flow supplemental oxygen via a non-rebreather mask is necessary to improve oxygenation. If wheezing is predominant and asthma is suspected, inhaled short-acting bronchodilators like albuterol should be given.
If there is no significant improvement, administration of systemic corticosteroids is generally recommended. Consideration for hospital admission and further assessment is warranted, possibly including intubation and mechanical ventilation if respiratory effort fails to improve or deteriorates.