Christian Alcaraz Frederiksen

Monitoring that can predict fluid responsiveness is an unsettled matter for spontaneously breathing patients. Mechanical ventilation induces cyclic variations in blood pressure, e.g. pulse pressure variation, whose magnitude predicts fluid responsiveness in mechanically ventilated patients. In this study, we hypothesised that a deep breathing manoeuvre with its effect on heart rate variability (HRV) could induce similar cyclic variations in blood pressure in spontaneously breathing healthy subjects and that the magnitude of these variations could predict the hemodynamic response to controlled haemorrhage. 37 blood donors were instructed to perform two simple deep breathing manoeuvres prior to blood donation; one manoeuvre with a respiratory cycle every 10 s (0.1 Hz) and one every 6 s (0.167 Hz). The variation in the pre-ejection period (∆PEP) was captured with the electrocardiographic and plethysmographic curves, while the hemodynamic response to haemorrhage was estimated with the cardiac output change assessed with ultrasonography. Respiratory HRV was estimated with root mean square of successive differences (RMSSD). Deep breathing induced cyclic changes in ∆PEP magnitude was significantly correlated to RMSSD (p