Peripheral sympathetic autoregulation in arterial calf inflow enhancement with intermittent pneumatic compression

Abstract

Background: Peroperative mortality, graft failure and balloon angioplasty limitations mitigate against active intervention for claudication. With the exception of exercise programmes, conservative treatments yield limited results. Intermittent pneumatic compression of the foot (IPCfoot) used daily for over 3 months enhances significantly the walking ability and pressure indices of stable claudicants; this is attributable to the significant calf inflow enhancement with IPCfoot; however, the physiologic mechanisms involved are only partially understood. Aims: by comparing the effects of IPCfoot and postural alteration on calf inflow haemodynamics, this study examines the role of peripheral sympathetic autoregulation, which controls homeostasis in lower limb vessels when posture changes, in the enhancement of calf inflow with IPCfoot in healthy subjects and claudicants. Material and Methods: forty-one limbs of healthy subjects (n=34; Group I) and 48 limbs of stable claudicants (Fontaine II) (n = 42; Group II) were studied. The volume flow (Q), pulsatility index (PI), mean (mV), peak systolic (PSV) and end diastolic (EDV) velocities were measured in the popliteal artery using duplex ultrasound in: the horizontal position, and on sitting with or without IPCfoot. Results: in Group II: median Q, mV, PSV and EDV increased by 61%, 53%, 29% and 51% respectively, and PI decreased by 20% as posture changed from sitting to horizontal; with IPCfoot median Q, mV, PSV and EDV increased by 70%, 58%, 22% and 75% respectively, and PI decreased by 26% (all p<0.001). In Group I: median Q, mV, PSV and EDV increased by 125%, 115%, 51% and 38% respectively and PI decreased by 30% as posture changed from sitting to horizontal; with IPCfoot median Q, mV, PSV and EDV increased by 119%, 153%, 23% and 46%, respectively, and PI decreased by 50% (all p<0.001). The effects of IPCfoot and postural alteration (from sitting to horizontal) did not differ haemodynamically (p>0.1) in both groups. Q on lying was similar in Groups I and II. On sitting Q was higher in Group II [p=0.027 (95% CI 1.7, 27 ml/min)]. Conclusions: the striking similarity in the haemodynamic effects of IPCfoot and postural alteration in the popliteal artery strongly suggests that the leg inflow enhancement with IPCfoot is mediated by a transient suspension of peripheral sympathetic autoregulation. In addition to their role as clinical markers of PVD severity, the autoregulatory reflexes of peripheral circulation appear to have functions with significant clinical implications in the management of patients with leg inflow impairment.