Coronary heart disease (CHD) is a non-communicable disease characterized by the buildup of fatty plaques (atheroma) inside the coronary arteries, causing them to narrow and restrict blood flow to the myocardium (heart muscle).
In a clinical study, researchers modeled the relationship between the percentage of a coronary artery's lumen cross-sectional area that remains unobstructed ('open') and the rate of coronary blood flow. The simulated results are summarized in Table 1.
Table 1
| Coronary artery lumen open (%) | Coronary blood flow rate (cm3/min\text{cm}^3/\text{min}cm3/min) |
|---|---|
| 100 | 250 |
| 80 | 185 |
| 60 | 110 |
| 40 | 44 |
| 20 | 12 |
Describe the relationship shown in Table 1 between the percentage of the coronary artery lumen that is open and the coronary blood flow rate.
Calculate the percentage reduction in coronary blood flow rate when the open lumen area of the artery is reduced from 100%100\%100% to 60%60\%60%. Show your working.
Assuming that the change in coronary blood flow rate is linear within the range of 20%20\%20% to 40%40\%40% open lumen area, estimate the blood flow rate when the open cross-sectional area is exactly 30%30\%30%. Show your working.