The potential interference of cutaneous circulation on muscle blood volume and oxygenation monitoring by near‐infrared spectroscopy (NIRS) remains an important limitation of this technique. Spatially resolved spectroscopy (SRS) was reported to minimize the contribution of superficial tissue layers in cerebral monitoring but this characteristic has never been documented in muscle tissue monitoring. This study aims to compare SRS with the standard Beer–Lambert (BL) technique in detecting blood volume changes selectively induced in muscle and skin. In 16 healthy subjects, the biceps brachii was investigated during isometric elbow flexion at 70% of the maximum voluntary contractions lasting 10 sec, performed before and after exposure of the upper arm to warm air flow. From probes applied over the muscle belly the following variables were recorded: total hemoglobin index (THI, SRS‐based), total hemoglobin concentration (tHb, BL‐based), tissue oxygenation index (TOI, SRS‐based), and skin blood flow (SBF), using laser Doppler flowmetry. Blood volume indices exhibited similar changes during muscle contraction but only tHb significantly increased during warming (+5.2 ± 0.7 μmol/L·cm, an effect comparable to the increase occurring in postcontraction hyperemia), accompanying a 10‐fold increase in SBF. Contraction‐induced changes in tHb and THI were not substantially affected by warming, although the tHb tracing was shifted upward by (5.2 ± 3.5 μmol/L·cm, P < 0.01). TOI was not affected by cutaneous warming. In conclusion, SRS appears to effectively reject interference by SBF in both muscle blood volume and oxygenation monitoring. Instead, BL‐based parameters should be interpreted with caution, whenever changes in cutaneous perfusion cannot be excluded.

This study quantified the dependence of the IVC cross-sectional area on controlled intrathoracic pressure changes and evidenced the stronger influence of diaphragmatic over thoracic activity. Individual variability in thoracic/diaphragmatic respiratory pattern should be considered in the interpretation of the respirophasic modulations of IVC size.

The rapid hyperemia evoked by muscle compression is short lived and was recently shown to undergo a rapid decrease even in spite of continuing mechanical stimulation. The present study aims at investigating the mechanisms underlying this attenuation, which include local metabolic mechanisms, desensitization of mechanosensitive pathways, and reduced efficacy of the muscle pump. In 10 healthy subjects, short sequences of mechanical compressions ( = 3-6; 150 mmHg) of the lower leg were delivered at different interstimulus intervals (ranging from 20 to 160 s) through a customized pneumatic device. Hemodynamic monitoring included near-infrared spectroscopy, detecting tissue oxygenation and blood volume in calf muscles, and simultaneous echo-Doppler measurement of arterial (superficial femoral artery) and venous (femoral vein) blood flow. The results indicate that ) a long-lasting (>100 s) increase in local tissue oxygenation follows compression-induced hyperemia, ) compression-induced hyperemia exhibits different patterns of attenuation depending on the interstimulus interval,) the amplitude of the hyperemia is not correlated with the amount of blood volume displaced by the compression, and ) the extent of attenuation negatively correlates with tissue oxygenation ( = -0,78, < 0.05). Increased tissue oxygenation appears to be the key factor for the attenuation of hyperemia upon repetitive compressive stimulation. Tissue oxygenation monitoring is suggested as a useful integration in medical treatments aimed at improving local circulation by repetitive tissue compression. This study shows that ) the hyperemia induced by muscle compression produces a long-lasting increase in tissue oxygenation,) the hyperemia produced by subsequent muscle compressions exhibits different patterns of attenuation at different interstimulus intervals, and ) the extent of attenuation of the compression-induced hyperemia is proportional to the level of oxygenation achieved in the tissue. The results support the concept that tissue oxygenation is a key variable in blood flow regulation.

These results demonstrate for the first time that: (1) blood drained by superficial veins may affect BL measurement; (2) it is difficult to exclude veins from the measurement by simple visual inspection of the cutaneous surface; (3) SRS effectively rejects artifacts from superficial hemodynamic changes in both cutaneous microcirculation and large veins. These results bear implications to conditions in which thermoregulatory adjustments cannot be excluded.

Intermittent Pneumatic Compression (IPC) devices can be used to analyze the mechanisms underlying several vascular phenomena, such as hyperaemia. Commercial devices have limited dynamics and do not allow the delivery of customizable compressive pressure patterns, making difficult the analysis of such phenomena, which may require the application of long stimulations with low amplitude as well as fast compressions with higher pressure level. To overcome these issues, a novel pneumo-tronic device aimed to the investigation of the physiological effects induced by limb compressions has been conceived and is presented in this work. The design requirements of the system, capable of delivering customizable compressive patterns in the range 0-200 mmHg, are outlined. The final prototype architecture is described, and a mathematical model of the entire system, also including the interaction between the device and the limb tissues, is proposed. The performance of the device has been evaluated in several conditions by means of simulations, whose results have been compared to the data collected from experimental trials in order to validate the model. The outcomes of both experimentation and simulation trials proved the effectiveness of the solution proposed. A possible employment of this device for the investigation of the rapid compression-induced hyperaemia is presented. Other potential applications concern the wide range of intermittent-pneumatic compression treatments.