Is the condtion you are referring to the dx for an infant?
The underlying cause can be a blood disorder (anemia, etc.) hypoxia (lack of oxygenated heart cells) from right side blood flow goes to the left side rather than filtered through the lungs. Or any mismatch between oxygen supply and its demand at the cellular level may result in a hypoxic condition.
The treatment would be to maximize oxygen delivery, to minimize oxygen consumption, and to favorably influence the systemic and pulmonary vascular resistances to improve pulmonary blood flow.