A cyanotic spell in a baby with tetralogy of Fallot is relieved by which position?

A cyanotic spell in a baby with tetralogy of Fallot is relieved by which position?

• A. lying flat
• B. knee-to-chest or squatting position
• C. standing
• D. on the side

Answer: (B)

During a cyanotic spell in tetralogy of Fallot, the obstruction to pulmonary blood flow makes more blood shunt from the right ventricle to the aorta via the VSD, lowering oxygen delivery to the lungs. The knee-to-chest position (or squatting in older children) increases systemic vascular resistance, which reduces the right-to-left shunt and pushes more blood toward the lungs. This improves pulmonary blood flow and raises arterial oxygen saturation, relieving the spell. Lying flat or standing does not raise resistance in the same protective way and can worsen the shunt, so knee-to-chest is the classic maneuver to help.

During a cyanotic spell in tetralogy of Fallot, the obstruction to pulmonary blood flow makes more blood shunt from the right ventricle to the aorta via the VSD, lowering oxygen delivery to the lungs. The knee-to-chest position (or squatting in older children) increases systemic vascular resistance, which reduces the right-to-left shunt and pushes more blood toward the lungs. This improves pulmonary blood flow and raises arterial oxygen saturation, relieving the spell. Lying flat or standing does not raise resistance in the same protective way and can worsen the shunt, so knee-to-chest is the classic maneuver to help.