Thank you for for your time. My talk is regarding a a project that I did a short while ago in in preop which was looking at um functional capacity assessment in preop patients. So specifically uh colarctyl patients over the age of 70 and comparing the shuttle walk test uh to uh CPET. And this was a presentation that I presented to a a wider audience. So at the risk of teaching ducks to suck eggs, I'll skim over the bit on functional capacity assessment, but obviously it's an important part of of pre-op assessment. Um it helps to establish or uh predict a patient's likely physiological reserve and and determine their ability to cope with demands of of major surgery. Um, and we know that generally speaking, patients with better functional capacity are less likely to have complications probably have a shorter length of stay and a lower rate of peroperative mortality. Um, and when it comes to assessing patients preoperatively, it's a really important part of risk stratification. It allows for shared decision- making and peroperative planning. There are subjective and objective methods of functional capacity assessment and CPAT is regarded as the gold standard objective method. uh is more expensive, requires trained personnel and specialized equipment and alternative objective assessments of functional capacity would include the shuttle walk test. So this is a picture of a bleed test because I couldn't find anyone actually doing the shuttle walk, but essentially the principle is the same. Your patient's walking backwards and forwards between two cones. the speed at which they have to walk increases every minute in time to you know an audio signal and then the test is is stopped when the patient can't get to the next cone before the signal goes off. Um and we calculate an incremental shuttle walk distance from that. Um and comparatively it's simple uh inexpensive and readily accessible. I've put the um CPET thresholds that we use for risk stratification or or risk uh assessment on here. Um I'm sorry for those who are more familiar with with CPET uh but for those who aren't uh to give you an overview there are uh multiple thresholds that we get from a CPET test but the three that have been most broadly studied specifically for peroperative risk prediction are peak V2. So the peak rate of oxygen uptake um and the value of uh less than 15 ms per kilo per minute is deemed to predict higher risk. um anorobic threshold or the V2 at which oxygen supply oxygen demand rather exceeds supply and the patient starts to metabolize anorobically um of less than 11 and the ventilatory equivalent for CO2 so that's the ratio of minute ventilation or VE uh to carbon dioxide production at anorobic threshold um overall that's a measure of uh gas exchange efficiency and a value of greater than 40 at anorobic threshold has been associated with poorer long-term outcomes. Um so essentially anyone who achieves less than 15 on a PV2, less than 11 on an anorobic threshold and greater than 40 on a VE or VCO2 anorobic threshold would be deemed to be at higher risk of peroperative complications. Um and you know probably the effect is cumulative in that you know the more sub threshold CE variables they are is probably has a a higher predictive value for identifying high risk patients. Sorry that's a very quick uh whiz through. Um so there have been multiple studies looking at the comparison between shuttle walk tests and CPET uh that have looked at various different thresholds in various different surgical populations. Um so uh less than 250 mters in patients undergoing lung cancer resection and major colctal surgery was associated with an increased risk of major complications and mortality. more than 350 meters in esophageal or gastric resection was associated with a better median survival than patients who got less than that. Um and more than 360 meters in elective intraabdominal surgery was shown to be predictive of achieving what would be described as acceptable or normal risk CPET parameters. All of the patients in that particular study who got more than 360 on their shuttle walk went on to have more than 15 peak V2 rather of more than 15 and an anorobic threshold of more than 11 when they subsequently had their CET. Um similarly 400 meters uh for patients undergoing long resection was also shown to be predictive of a PO2 of more than 50. Um so essentially patients who get less than 250 meters uh you know I think we can conclude that they're likely to require formal testing to quantify their functional capacity. uh but there is a possibility that for patients who get more than 360 or more than 400 meters there's a possibility that they're very likely to have normal or acceptable risk CPEP parameters when they undergo testing probably at a lower risk of post-oper post-operative complications as a result of that and for that reason in the peroperative setting might not necessarily require formal CPET testing. So my aim was to try and assess whether the shuttle walk test could be used as a screening test to try and identify patients who might not necessarily require preop CPET um in the hope of leading to a potential costsaving reducing the waiting times for patients who do need CPET and not just uh in the peroperative setting but but generally it's used for multiple other reasons in in other settings as well and at a time when the patients are often going through lots of different hospital appointments to reduce the number and hopefully improve their experience as a result of that currently in colurectal patients over the age of 70 we were doing CPET in in all of them. We were also doing the shuttle walk tests routinely in prehab but not really using that data in our preop pathway. Um so I did a a retrospective audit of all of those patients in that group um who had undergone both the shuttle walk as a part of prehab and CPET between uh April 22 and December 23 and used previously published thresholds. So I wanted to assess whether those thresholds of 250 m or 360 m that have been previously published could identify patients with acceptable CPET performance in this population. And I use positive predictive values to to try and demonstrate that. Um overall there's a relatively um even split between men and women. A mean age of 77 and a mean shuttle walk distance of 250 m. Um the mean CPET variables were um as you can see there all within what would be regarded as an acceptable or a normal risk uh profile for proceeding with surgery peroperatively. Uh so mean PP2 was 17, mean at was 12.8 and mean VVCO2 was 33.6. There were 111 patients who completed both tests with a mean interval between the tests of 6.8 days. 21 patients achieved a distance of more than 360 and 55 achieved a distance of more than 250. Um quite a bit of information on this slide, but I'll just narrow down really on the 360 meter data. Um so of the 21 patients who achieved a distance of more than 360 m, 19 of them had a peak V2 of more than 15, giving a positive predictive value of 0.91. Um you'll notice that the negative predicted value is uh significantly worse than that and I'll talk more about why that might be towards the end. Uh a similar pattern for a 250 m threshold but the positive predicted value as you would imagine not quite as good. Uh for an anorobic threshold of more than 11, there was a positive predicted value of 0.95. So 20 of the 21 patients who achieved more than 360 m on their shuttle walk had an anorobic threshold of more than 11. And the results were uh the same for predicting VE VCO2 less than 40. From that I concluded that a threshold of 360 m demonstrates a reasonable ability to identify patients who are likely to have CPET parameters that would be deemed acceptable or satisfactory to proceed with surgery. The positive predicted values for that threshold predicting all of the parameters that I've mentioned before were in excess of 0.9. in the field that the shuttlew walk test can be used or it's reasonable to use it as a screening tool to identify patients in this cohort who might not necessarily need further CPET testing and for this cohort of patients that would lead to a potentially 19% reduction in the number of tests a significant cost saving and hopefully improved patient experience. Um as a result of that there's been a change to our prehab uh pathway or our preop pathway. Um so this is the new flowchart that they follow in prehab now which uh this should say age more than 70. So if the patient's over 70 and a waiting colctal surgery um they uh go to prehab uh they achieve uh more than 360 m on their shuttle walk test. If they've already got a CPET ordered that can be that can be cancelled. It can be used for another patient. If they haven't already got a CPET ordered or booked they don't need that appointment. That can be used for somebody else. save a little bit of money there hopefully um and um potentially increase or improve the use of the the waiting list for those patients who who do require it uh either peroperatively or otherwise. Um as I mentioned the uh negative predictive value of the thresholds is not very good. Uh so poor shuttle walk tested performance doesn't necessarily mean they're going to get a high-risisk CPET. There's probably a number of reasons for that but I would suspect muscular scalletal reasons. patients who are simply not able to complete the shuttle walk for whatever reasons because they can't walk or you know have difficulty with that but are much more comfortable sitting on a bike and demonstrate reasonable cardio uh cardiovascular reserve and overall there are a significant number of patients with satisfactory CPET performance in this population and the high prevalence of satisfactory CPET might explain the high positive predictive values of the test obviously a single center a single cohort but I would say that's comparable to the other studies that are available looking at the same thing And for this, I didn't compare outcomes between groups, but that's something we could look at going forward. And the plan is to try and assess this to assess the new pathway, see how many patients it affects, look at how much money that's saving hopefully, but also to see look at the outcomes of those patients and and and review things um going forward. Um thanks very much for your time. So please, if you've got any questions, I'd again happy to take them.