Saudurma Sirait. (2020). Comparison the effectiveness of the head of bed to 45 and 30 degrees with hyperoxigenation against oxygen saturation during the open suction in patients that installed mechanical ventilation in ICU room. International Journal of Allied Medical Sciences and Clinical Research, 8(2), 359–367. https://doi.org/10.61096/ijamscr.v8.iss2.2020.359-367