Abstract
Background: Exposure to particulate air pollution, of which diesel exhaust (DE) is a major component, increases cardiovascular morbidity and mortality. Although the underlying mechanisms of these effects are not fully understood, there are reports of increased blood pressure and reduced heart rate variability consistent with altered autonomic nervous function following exposure to particulate air pollution.
Objective: We tested the hypothesis that exposure to DE alters the haemodynamic response to systemic infusion of norepinephrine (NE).
Methods: In a randomized double-blind crossover study, 14 healthy non-smoking volunteers were exposed to dilute diesel exhaust or filtered air for one hour during intermittent exercise. Two hours after the exposure, the subjects received intravenous infusions of NE (50 ng/kg/min over 15 mins) and the haemodynamic response was assessed using invasive blood pressure, pulse wave velocity and thoracic bioimpedance.
Results: In comparison to filtered air, cardiac index was reduced (P=0.027) and systemic vascular resistance was increased (P<0.0001) following DE exposure. Despite this, the vasopressor response to infused NE was attenuated: increases in mean arterial pressure and pulse wave velocity were both reduced (P<0.0001 for both) whilst changes in heart rate were similar (P=0.28).
Conclusions: Our results show unexpected haemodynamic responses to NE after exposure to dilute DE, with both attenuated vasopressor responses and an inhibitory effect on cardiac index. These novel findings suggest that DE inhalation alters the cardiovascular response to adregenic stimulation, which could represent an effect on the autonomic nervous system.
- © 2011 ERS
