Final answer:
A critical change in diastolic blood pressure is considered to be a decrease of 20 mmHg or more. Diastolic pressure is essential for blood flow and should be less than 80 mmHg but not below 60 mmHg. Significant changes can indicate various health issues and require medical attention.
Step-by-step explanation:
What is considered a critical change in diastolic blood pressure is a decrease of 20 mmHg or more. Diastolic blood pressure is critical for maintaining adequate blood flow and pressure throughout the cardiac cycle. A desirable diastolic pressure is generally less than 80 mmHg, but it should not be lower than 60 mmHg. Significant changes in diastolic pressure can indicate a range of health issues, such as fluid balance concerns, internal hemorrhaging, or blood vessel dilation problems which can put a strain on the heart's ability to pump blood. Since critical changes in diastolic pressure can lead to serious complications, it's essential to monitor these values carefully and seek medical attention if drastic shifts occur.