AB0961 Cardiorespiratory response according to body weight support and gait velocity via anti-gravity treadmill after bilateral total knee arthroplasty
Authors: B.R. Kim
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Patients undergoing total knee arthroplasty (TKA) may benefit from early focused postoperative rehabilitation, and progressive weight-bearing activities, such as walking, are routinely recommended during rehabilitation to facilitate return to normal gait function. Not all patients are capable of full weight-bearing activity in the early postoperative period and assistive devices such as walkers, crutches, and canes, are routinely employed. The anti-gravity treadmill, consisting of a treadmill enclosed within an airtight chamber, applies air pressure to a patient's lower body to alter body weight support and can reduce the forces at the knee during weight bearing exercise. The anti-gravity treadmill could be a useful device for early postoperative rehabilitation of TKA, especially for those patients with reduced physical strength and cardiovascular fitness. However, so far, there have been no reported investigations of the physiologic cardiorespiratory responses via anti-gravity treadmill in patients following TKA. <h3>Objectives</h3> This study was conducted to investigate cardiorespiratory response according to body weight support and gait velocity elicited using an anti-gravity treadmill during walking and to find specific gait velocity and body weight support combinations early after bilateral TKA. <h3>Methods</h3> Twenty five patients who underwent a primary TKA were enrolled in this study. Subjects walked with 2.5 km/h and 3.5 km/h on an anti-gravity treadmill at 3 levels (50%, 75%, 100%) of body weight (BW). Each trial was performed for 2 min with at least 1 min rest between trials. For cardiorespiratory responses, oxygen consumption (VO<sub>2</sub>), Heart rate, systolic (SBP) and diastolic blood pressure (DBP), respiratory exchange ratio (RER) and rate pulse product (RPP) were measured continuously with average values. The VO<sub>2</sub>, heart rate and RER were measured by using the K4b2 (Cosmed, Rome, Italy), which is a wireless cardiopulmonary diagnostic device, and the values of these exercise variables were defined as the averages of values recorded during the last 30 s of exercise. The RPP was calculated ([heart rate x SBP]/100). In addition, Borg's rating of perceived exertion scale (RPE) and visual analogue scale (VAS) of knee pain were recorded immediately after each condition. <h3>Results</h3> There were 20 females and 32 men, with the average age being 71.3±5.4 years. In the two-way repeated measures ANOVA, VO<sub>2</sub> levels (p&lt;0.01), HR (p&lt;0.01), RPP (p&lt;0.01), RPE (p&lt;0.01), RER (p&lt;0.01) and VAS (p&lt;0.01) were significantly increased in proportion to 3 levels (50%, 75%, 100%) of BW. In the post-hoc analysis, all other conditions except comparison of RER values between 50% level of BW and 75% level of BW under a speed of 2.5 km/h and a speed of 3.5 km/h were statistically significant. Meanwhile, SBP (p=0.65) and DBP (p=0.39) were not influenced by difference of BW levels. While walking with a speed of 3.5 km/h at same fraction of BW level, VO<sub>2</sub> (p=0.03), RPE (p&lt;0.01) and RER (p=0.01) values were statistically greater than 2.5 km/h. In the post-hoc analysis, all other conditions except comparison of RER values between a speed of 2.5 km/h and a speed of 3.5 km/h under 100% level of BW was statistically significant. In addition, multiple linear regression analysis was performed to defining VO<sub>2</sub> as functions of gait speed and fraction of BW under each condition. Based on BW and gait velocity settings of the LBPP treadmill, the equations were VO<sub>2</sub>=1.46 v+0.08 BW+3.13 (adjusted <i>R</i><sup>2</sup>=0.34) <h3>Conclusions</h3> This study demonstrated that cardiorespiratory responses were variably computed by combination of weight support and gait velocity during anti-gravity treadmill walking, and these cardiorespiratory responses and knee pain were more significantly influenced by body weight support than gait velocity. These findings suggest that body weight support and gait speed should be considered for gait training program for cardiovascular fitness early after bilateral total knee arthroplasty. <h3>Disclosure of Interest</h3> None declared