Published in:
01-02-2006 | Original
Acute effects of hyperoxemia on dyspnoea and respiratory variables during pressure support ventilation
Published in: Intensive Care Medicine | Issue 2/2006
Login to get accessAbstract
Objective
To evaluate the acute effect of hyperoxemia on the comfort and the respiratory variables in patients undergoing pressure support ventilation (PSV) for acute respiratory failure (ARF).
Design and Setting
Prospective, observational study performed in the intensive care unit of a university hospital.
Patients
Thirteen semirecumbent patients were ventilated in PSV mode, the setting of which was established by the treating physician who was blinded to the study.
Measurements
The variables measured at different levels (21–80%) of FiO2 randomly applied were: minute volume (V
E), respiratory frequency (f) and the pressure develing during the first 100 ms of an occluded breath (P0.1). These variables were firstly measured at the level of FiO2 chosen by the treating physician. Severity of dyspnea was rated using the visual analogue scale 15' after each FiO2 variation.
Results
Modulation of FiO2 was able to vary significantly the respiratory variables, since a FiO2 increase was associated with a decrease in dyspnea, P0.1, f, and V
E. While valuable variations were detected at both lower and higher values of FiO2 than those established by the treating physician, a significant improvement in the respiratory variables was detected at FiO2 60%. The reduction in respiratory drive was statistically related to an amelioration of dyspnea (R2 = 0.89) even at values of FiO2 higher than 60%.
Conclusions
During PSV the respiratory drive can be heavily modulated by varying the FiO2 since even at FiO2 greater than 0.6 dyspnea and respiratory variables continued to improve.