Peripheral skin perfusion reflects the level of vascularity and viability of a limb and may help in planning the site of amputation or bypass surgery in patients with vascular disease. This study used peripheral pulse oximetry in 20 healthy volunteers and in 20 patients with limb ischaemia. Pulse oximetry saturation levels (Psa,O2) were compared with ankle artery Doppler pressures and transcutaneous oxygen measurements (Ptc,O2). Recordings were taken at two standard sites distally and referenced to finger and forearm to calculate an index. A significant correlation was found between Ptc,O2 and Psa,O2 in patients with ischaemia (r = 0.68, P less than 0.01). A further group of 12 patients with acute limb ischaemia was similarly assessed before and after revascularization. After revascularization mean(s.d.) Ptc,O2 increased from 38(13) to 44(1) mmHg (P greater than 0.05) and mean(s.d.) Psa,O2 increased from 86(3) to 90(4) per cent (P less than 0.01). These data suggest that pulse oximetry is a more sensitive index of peripheral perfusion than Ptc,O2 or ankle artery Doppler pressure and that, because of its accuracy and simplicity, it merits further use.
Intelligent planning, control and forecasting of electricity usage has become a vitally important element of the modern conception of the energy grid. Electricity smart-meters permit the sequential measurement of electricity usage at an aggregate level within a dwelling at regular time intervals. Electricity distributors or suppliers are interested in making general decisions that apply to large groups of customers, making it necessary to determine an appropriate electricity usage behaviour-based clustering of these data to determine appropriate aggregate load profiles. We perform a clustering of time series data associated with 3670 residential smart meters from an Irish customer behaviour trial and attempt to establish the relationship between the characteristics of each cluster based upon responses provided in an accompanying survey. Our analysis provides interesting insights into general electricity usage behaviours of residential consumers and the salient characteristics that affect those behaviours. Our characterisation of the usage profiles at a fine-granularity level and the resultant insights have the potential to improve the decisions made by distribution and supply companies, policy makers and other stakeholders, allowing them, for example, to optimise pricing, electricity usage, network investment strategies and to plan policies to best affect social behavior.
Pulse oximetry: a n e w non-invasive assessment of peripheral arterial occlusive disease Sir We read with interest the article by Joyce ef al. ( B r J Surg 1990; 77: I 1 15-1 7) on the subject of pulse oximetry (Psa,02) in peripheral vascular disease. We assume that the patients and control groups are of comparable mean age, with similar smoking histories; no data are given on this point. More importantly, we find it difficult to understand why pulse oximetry. which reflects arterial oxygen saturation, should be influenced by arterial narrowing. Transcutaneous oximetry clearly mirrors the degree of oxygen utilization in the end-tissuein other words, it is measuring a function of oxygenation at a level distal to the point at which oxygen is consumed. This is not the case with pulse oximetry. since measurements using this technique rely on the pulsatile nature of pre-capillary flow. Hence the saturation of the blood within the capillaries is not measurable by this method.Reduced P,,,O, readings in peripheral vascular disease may reflect diminished pulsatility in peripheral arterioles. Venous pulsation may therefore contribute a relatively greater proportion to the P,,,o, signal, leading to apparently lower arterial saturation. Thus the authors may in fact be exploiting a deficiency in the technique to reveal a difference between their control and disease groups which may well be spurious.We would be interested to hear the authors' comments on these remarks. Author's reply SirWe are indebted to Mr Cheatle and Mr Coleridge-Smith for their interest in our paper and for their informed comments on our study and its findings. Their letter raises some issues that we would like to address.Clearly our control group and patient group were not comparable either in respect ofage or smoking history. To match the former with the latter would have inevitably included a number of patients with sub-clinical vascular disease. Our intention was to utilize a group of healthy people to enable us to establish a baseline of information against which data from patients with peripheral vascular disease could be evaluated.We did not of course state that there was a direct and simple relationship between oxygen saturation, as measured by pulse oximetry, and arterial narrowing. The correlation between P,,,oi and angiographic score preoperatively and the maintenance of this relationship postoperatively does, however, suggest an indirect relationship which may very well reflect diminished pulsatility in arterial disease as Cheatle and Coleridge-Smith suggest. Their belief that venous pulsation makes a significant contribution to the P,,,o, signal is more putative. We would be genuinely interested in any data bearing on this aspect of pulse oximetry that they can provide. If their contention can be sustained then we shall need to re-evaluate the technique of pulse oximetry and the significance of its derived data. Nevertheless, our oximetry values, obtained by a conventional and current technique, are valid in as far as the technique is valid....
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.