How does repeating and comparing the hemodynamic measures on the same subjects over time affect the power of the study?

Let’s look at the use of ANOVA in the following nursing research article:
Özden, D., & Görgülü, R. S. (2015). Effects of open and closed suction systems on the haemodynamic parameters in cardiac surgery patients. Nursing in Critical Care, 20(3), 118–125. doi:10.1111/nicc.12094