Oxygenation equilibration time after alteration of inspired oxygen in critically ill patients

• Published in: Heart & lung 2010-03, Vol.39 (2), p.147-152
• Main Authors: Fildissis, George, MD, PhD, Katostaras, Theofanis, PhD, Moles, Athanassios, MD, Katsaros, Andreas, MD, Myrianthefs, Paylos, MD, PhD, Brokalaki, Hero, PhD, RN, Tsoumakas, K., MD, PhD, Baltopoulos, George, MD, PhD
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Adults; Aged; Aged, 80 and over; APACHE; Blood Gas Analysis; Blood pressure; Cardiovascular; Critical Care; Critical Illness; Female; Humans; Intensive care; Intensive Care Units; Least-Squares Analysis; Male; Middle Aged; Oxygen; Oxygen - administration & dosage; Oxygen - blood; Oxygen Inhalation Therapy; Patients; Prospective Studies; Pulmonary/Respiratory; Terminal illnesses; Time Factors
• ISSN: 0147-9563; 1527-3288
• DOI: 10.1016/j.hrtlng.2009.06.009

To determine the time required for arterial oxygen partial pressure (Pa o2 ) equilibration after a change in fractional inspired oxygen (F io2 ) in intensive care unit (ICU) patients, a prospective study in a 7-bed university ICU was performed. Forty adult patients were examined using sequential arterial blood gas measurements after a .3 alteration in F io2 . The Pa o2 value measured at 30 minutes after a step change in F io2 in both periods was accepted as representative of the equilibrium value for Pa o2 . The mean equilibration time was 8.26 ± 5.6 minutes and 4.5 ± 2.65 minutes for increases and decreases in Pa o2 , respectively ( P = .003). The constant k values were .44 ± .31 minutes and .72 ± .7 minutes for increases and decreases in Pa o2 , respectively. There was no significant difference between the increase and the decrease of 90% oxygenation times in the 2 groups ( P = .150 and P = .446, respectively). The study confirms that a period of less than 10 minutes is adequate for 90% of the equilibration of Pa o2 to occur after an F io2 change in ICU patients.