| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
RESPIRATORY |
1 Department of Anaesthesiology, University Health Network, Toronto Canada
2 Department of Physiology, University of Toronto, Toronto Canada
Current methods of forcing end-tidal PCO2 (PETCO2) and PO2 (PETO2) rely on breath-by-breath adjustment of inspired gas concentrations using feedback loop algorithms. Such servo-control mechanisms are complex because they have to anticipate and compensate for the respiratory response to a given inspiratory gas concentration on a breath-by-breath basis. In this paper, we introduce a low gas flow method to prospectively target and control PETCO2 and PETO2 independent of each other and of minute ventilation in spontaneously breathing humans. We used the method to change PETCO2 from control (40 mmHg for PETCO2 and 100 mmHg for PETO2) to two target PETCO2 values (45 and 50 mmHg) at iso-oxia (100 mmHg), PETO2 to two target values (200 and 300 mmHg) at normocapnia (40 mmHg), and PETCO2 with PETO2 simultaneously to the same targets (45 with 200 mmHg and 50 with 300 mmHg). After each targeted value, PETCO2 and PETO2 were returned to control values. Each state was maintained for 30 s. The average difference between target and measured values for PETCO2 was ± 1 mmHg, and for PETO2 was ± 4 mmHg. PETCO2 varied by ± 1 mmHg and PETO2 by ± 5.6 mmHg (S.D.) over the 30 s stages. This degree of control was obtained despite considerable variability in minute ventilation between subjects (± 7.6 l min–1). We conclude that targeted end-tidal gas concentrations can be attained in spontaneously breathing subjects using this prospective, feed-forward, low gas flow system.
(Received 12 February 2007;
accepted after revision 2 April 2007;
first published online 5 April 2007)
Corresponding author J. A. Fisher: Toronto General Hospital 7EN-242, 200 Elizabeth St, Toronto, Canada, M5G 2C4. Email: joe.fisher{at}utoronto.ca
This article has been cited by other articles:
|
|
 |
|
  D. M. Mandell, J. S. Han, J. Poublanc, A. P. Crawley, A. Kassner, J. A. Fisher, and D. J. Mikulis Selective Reduction of Blood Flow to White Matter During Hypercapnia Corresponds With Leukoaraiosis Stroke, July 1, 2008; 39(7): 1993 - 1998. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. M. Mandell, J. S. Han, J. Poublanc, A. P. Crawley, J. A. Stainsby, J. A. Fisher, and D. J. Mikulis Mapping Cerebrovascular Reactivity Using Blood Oxygen Level-Dependent MRI in Patients With Arterial Steno-occlusive Disease: Comparison With Arterial Spin Labeling MRI Stroke, July 1, 2008; 39(7): 2021 - 2028. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Duffin Measuring the ventilatory response to hypoxia J. Physiol., October 1, 2007; 584(1): 285 - 293. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
