Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA332

Poster Communications

Laser Doppler Perfusion Imaging can be used for in vivo continuous perfusion assessment

H. Silva1,2, H. A. Ferreira3, A. Gadeau4, L. Monteiro Rodrigues1,2

1. CBiOS (Research Center for Biosciences and Health Technologies), U Lusófona, School of Health Sc & Technologies, Lisboa, Portugal. 2. Pharmacol. Sc Depart, U Lisboa, Faculty of Pharmacy, Lisboa, Portugal. 3. IBEB Institute Bioph Biomed Engineering, U Lisboa, Faculty of Sciences, Lisboa, Portugal. 4. U Bordeaux & INSERM, U1034, Adaptation cardiovasculaire à l'ischémie, F-33600, Pessac, France.

The in vivo assessment of the microcirculatory status is becoming increasingly important for studying cardiovascular function. Among several technologies available for the noninvasive perfusion quantification, Doppler-based flowmetry (LDF) and perfusion imaging (LDPI) techniques are often employed. LDPI is almost exclusively used for the perfusion assessment over large tissue areas, however, it can also be used in a continuous mode, recording flow in a much smaller area over time, similar to LDF. Despite the proximity between these techniques, these signals have not been compared this way. Our objective was to explore the LDPI ‘continuous mode' from the peripheral circulation of anesthetized mice and compare the obtained values with LDF. We used a group of C56/BL6 male mice (n=5, 7 w.o., 25.0 ± 0.8g) anesthetized with a ketamine (137.5 mg/kg) and xylazine (11.0 mg/kg) mixture (i.p.). All procedures involving animal experimentation were performed in accordance with the current ethical guidelines for the protection of animals used for scientific purposes in the EU. Twenty minutes after induction, LDF and LDPI signals were acquired for 30 minutes on the plantar aspect of the lower limb. The acquisition sampling rate of LDPI (left limb) was 40 Hz, and 128 Hz (later downsampled to 40 Hz) for LDF (right limb). The wavelet transform (WT) was applied to both signals to obtain their spectral decomposition. Both LDF and LDPI signals showed five spectral bands in similar spectral regions, which are compatible with the cardiorespiratory (LDF: 4.7-1.8Hz; LDPI: 4.7-2.8Hz), myogenic (LDF:0.1-0.048Hz; LDPI: 0.1-0.054Hz), sympathetic (LDF: 0.048-0.026Hz; LDPI: 0.054-0.028Hz), endothelial NO-dependent (LDF: 0.013-0.0071Hz LDPI: 0.013-0.0070Hz) and NO-independent (LDF: 0.0067-0.0047Hz; LDPI: 0.0070-0.0050Hz) components. Therefore, each component amplitude was comparable for both techniques. Since both signals were acquired under the same wavelength and band width parameters, we conclude that the observed differences in the spectral bands' width are explained by the differences in the paths taken by the emitted light. With LDPI, light travels through room air before crossing the skin, while with LDF it directly crosses the skin. These similarities between these techniques suggest that LDPI is a suitable alternative to LDF for continuous perfusion measurements.

Where applicable, experiments conform with Society ethical requirements