Final answer:
The fifth Korotkoff sound, which is the disappearance of sound, represents diastolic blood pressure in toddlers, occurs when the cuff's pressure drops below the diastolic pressure, indicating unrestricted blood flow.
Step-by-step explanation:
The diastolic blood pressure in toddlers, as in adults, is represented by the fifth Korotkoff sound. This is the point at which the last sound is heard when measuring blood pressure using a sphygmomanometer and a stethoscope. The process involves inflating the cuff to a pressure above the systolic pressure and then gradually releasing the air. When the cuff's pressure equals the systolic pressure, the first Korotkoff sound is heard, indicating the blood beginning to spurt into the artery. As the pressure is further reduced, the sounds can be heard changing in quality; however, it is the disappearance of sounds, the fifth Korotkoff sound, which signals that the pressure in the cuff has dropped below the arteriole's diastolic pressure and blood flow is no longer restricted.