Abstract
Objective: To assess the feasibility of expiratory flow-volume curves as a measurement of respiratory mechanics during ventilatory support: to what extent is the shape of the curve affected by the exhalation valve of the ventilator? Design: Prospective, comparative study. Setting: Medical intensive care unit of a university hospital. Patients: 28 consecutive patients with various conditions, mechanically ventilated with both the Siemens Servo 900C and 300 ventilators, were studied under sedation and paralysis. Interventions: The ventilator circuit was intermittently disconnected from the ventilator at end-inspiration in order to obtain flow-volume curves with and without the exhalation valve in place. Measurements and results: Peak flow (PEF) and the slope of the flow-volume curve during the last 50 % of expired volume (SF50) were obtained both with and without the exhalation valve in place. The exhalation valve caused a significant reduction in peak flow of 0.3 l/s (from 1.27 to 0.97 l/s) with the Siemens Servo 900 C ventilator and of 0.42 l/s (from 1.36 to 0.94 l/s) with the Siemens Servo 300 ventilator (p < 0.001). The SF50 was not affected. Conclusion: In mechanically ventilated patients, the exhalation valve causes a significant reduction in peak flow, but does not affect the SF50. This study further suggests that the second part of the expiratory flow-volume curve can be used to estimate patients' respiratory mechanics during ventilatory support.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
Author information
Authors and Affiliations
Additional information
Received: 8 October 1998 Final revision received: 18 February 1999 Accepted: 18 May 1999
Rights and permissions
About this article
Cite this article
Lourens, M., van den Berg, B., Hoogsteden, H. et al. Flow-volume curves as measurement of respiratory mechanics during ventilatory support: the effect of the exhalation valve. Intensive Care Med 25, 799–804 (1999). https://doi.org/10.1007/s001340050955
Issue Date:
DOI: https://doi.org/10.1007/s001340050955