Objective: To evaluate the acute influences 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 an 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 (VE), respiratory frequency (f) and the pressure developed in the first 100 msec of an occluded breath (P0.1). These variables were firstly measured at the level of FiO2 chosen by the treating physician. Severity of dyspnoea 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 of dyspnoea, P0.1, f and VE. While valuable variations were detected at lower but also at higher values of FiO2 than those established by the treating physician, a significant improvement of the respiratory variables was detected at FiO2 60%. The reduction of respiratory drive was statistically related to an amelioration of dyspnoea (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 the FiO2 > 0.6 dyspnoea and respiratory variables continued to improve.
Acute effects of hyperoxemia on dyspnoea and respiratory variables during pressure support ventilation
VOLTA, Carlo Alberto;RAGAZZI, Riccardo;ALVISI, Raffaele
2006
Abstract
Objective: To evaluate the acute influences 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 an 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 (VE), respiratory frequency (f) and the pressure developed in the first 100 msec of an occluded breath (P0.1). These variables were firstly measured at the level of FiO2 chosen by the treating physician. Severity of dyspnoea 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 of dyspnoea, P0.1, f and VE. While valuable variations were detected at lower but also at higher values of FiO2 than those established by the treating physician, a significant improvement of the respiratory variables was detected at FiO2 60%. The reduction of respiratory drive was statistically related to an amelioration of dyspnoea (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 the FiO2 > 0.6 dyspnoea and respiratory variables continued to improve.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
