Analysis of breathing-related variations in ECG-triggered Laser Doppler perfusion signals measured on the beating heart during surgery

Laser Doppler perfusion monitoring (LDPM) is a method to assess microvascular perfusion. A modified, ECG-triggered LDPM system has been developed to measure myocardial perfusion with minimum influence from heart motion. With this method, one systolic (PLS) and one diastolic (PLD) perfusion value is obtained. The aim of this study was to analyse breathing-related variations in PLS and PLD measured during open-heart surgery. The phase delays between PLS, PLD, mean arterial blood pressure (MAP), heart rate and, indirectly, the respiration were determined. MAP tended to be in phase with or precede the variations in PLD, i.e., PLD was at a maximum at the end of inspiration or at the beginning of expiration. No clear relation between PLS and any of the other signals could be found.