EFFECT OF CAFFEINE ON INCREASING OF BLOOD VESSELS STIFFNESS MEASURED BY PHOTOPLETHYSMOGRAM
Hasballah Zakaria, Tuti Adi Tama Nasution, Tati Lathifah Erawati Mengko
Institut Teknologi Bandung, Indonesia
Blood flow is highly dependent on blood pressure and resistance of blood vessels. Blood pressure is a major driving force so that blood can flow in the vessels. Many factors can increase blood pressure, one of which is the caffeine from coffee. This study measured the blood volume changes by using photoplethysmogram (PPG) placed on index finger to observe the effect of caffeine on subjects. PPG parameter included time delay (dT), stiffness index (SI), augmentation index (AI), pulse interval (PI) and inflection point area (IPA) . The study was conducted on 12 healthy subjects with age ranges of 20-40 years old and weight range from 45-80 kg. Experiments conducted between 09.00am - 12.00 pm. The PPG measurements was performed before drinking coffee and subsequently after at minute 15, 30, 45, 60, 120, and 180. Results showed a decrease in dT along with an increase of SI and AI. Furthermore, coffee gave a maximum effect at minute 30 and its temporal effect then decline to normal state after an hour. There was a moderate increase of PI and IPA but the result is not conclusive. These results indicated that the blood vessels will tend to be more rigid during the caffeine effect. This change in blood vessel stiffness then return to its original state after about an hour. The change of blood vessel stiffness may effect on increasing the blood pressure. Keywords: caffeine, coffee, blood pressure, photoplethysmogram, stiffness.