Oxygenation using tidal volume breathing after maximal exhalation.
We compared, in volunteers, the oxygenation achieved by tidal volume breathing (TVB) over a 3-min period after maximal exhalation with that achieved by TVB alone. Twenty-three healthy volunteers underwent the two breathing techniques in a randomized order. A circle absorber system with an oxygen flow of 10 L/min was used. The end-expiratory oxygen concentration (EEO(2)) was monitored at 15-s intervals up to 3 min. TVB after maximal exhalation produced EEO(2) values of 68% +/- 5%, 75% +/- 5%, and 79% +/- 4% at 30, 45, and 60 s, respectively, which were significantly larger (P < 0.05) than the corresponding values obtained with TVB alone (58% +/- 5%, 66% +/- 6%, and 71% +/- 5%, respectively). In both techniques, the EEO(2) increased exponentially, with time constants of 35 s during TVB after maximal exhalation versus 58 s during TVB without prior maximal exhalation. In conclusion, maximal exhalation before TVB can hasten preoxygenation by decreasing the nitrogen content of the functional residual capacity, with a consequent increase of EEO(2) to approximately 70% in 30 s and 80% in 60 s.


CONCLUSIONS
Oxygenation by using maximal exhalation before tidal volume breathing produced a significantly faster increase in end-expiratory oxygen concentration than oxygenation with tidal volume breathing alone.
Department of Anesthesiology, American University Medical Center, Beirut, Lebanon.
Anis S
AS
Baraka
Samar K
SK
Taha
Mohamad F
MF
El-Khatib
Faraj M
FM
Massouh
Dima G
DG
Jabbour
Mahmoud M
MM
Alameddine
D000328:Adult; D000758:Anesthesia; D002245:Carbon Dioxide / Q000097:blood; D005260:Female; D005652:Functional Residual Capacity; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption; D010102:Oxygen Inhalation Therapy; D011650:Pulmonary Alveoli / Q000378:metabolism; D015656:Respiratory Mechanics / Q000502:physiology*; D013990:Tidal Volume / Q000502:physiology*
D002245:Carbon Dioxide; D010100:Oxygen