Factors influencing oxygen store during denitrogenation in the healthy patient.
OBJECTIVE
To define the various factors that influence the rate of effective preoxygenation.


METHODS
Prospective, randomized study.


METHODS
Procedure room in a teaching hospital.


METHODS
14 ASA physical status I volunteers who performed 4 sessions of breathing in random order. Of these volunteers, 7 performed two extra sessions using vital capacity breathing, which were also completed in random order.


METHODS
Using the circle system, volunteers breathed with a mouthpiece and nose-clip until expired nitrogen reached 5%, using either a fresh gas flow of 5 L/min or 10 L/min or a system flushed with O(2).


METHODS
End-expired levels of O(2), nitrogen, and CO(2) were recorded.


RESULTS
Minute ventilation, functional residual capacity, and age were significant factors for rate of denitrogenation. However, height and weight were not significant factors in predicting time to denitrogenation. At low flow rates, flushing with O(2) significantly decreased the time of denitrogenation. There appeared to be little clinical benefit of flushing with O(2) when a 10 L/min O(2) flow was used.


CONCLUSIONS
A high gas flow rate appears critical to achieving rapid preoxygenation.
Sum Ping
Sam John T
SJ
VA North Texas Healthcare System, Dallas, TX 75216, USA. sam.sum-ping@utsouthwestern.edu
Makary
Laila F
LF
Van Hal
Michael D
MD
D000328:Adult; D002245:Carbon Dioxide / Q000378:metabolism*; D005260:Female; D006784:Hospitals, Teaching; D006801:Humans; D008297:Male; D008875:Middle Aged; D009584:Nitrogen / Q000378:metabolism*; D010100:Oxygen / Q000008:administration & dosage / Q000378:metabolism*; D011446:Prospective Studies; D012143:Respiratory Physiological Phenomena; D014797:Vital Capacity / Q000502:physiology
D002245:Carbon Dioxide; D009584:Nitrogen; D010100:Oxygen