Applanation tonometry: a reliable technique to assess aortic pulse wave velocity in spinal cord injury

Abstract

Study design: Within-subject repeated measures. Objectives: To determine the intra-and inter-tester reliability of aortic pulse wave velocity (aPWV) measurements collected using applanation tonometry in individuals with spinal cord injury (SCI). Setting: Inpatient Rehabilitation Centre and outpatient Clinic in Vancouver, BC, Canada. Methods: Fifteen men and three women with traumatic SCI (age: 46 ± 16 years; C3-L1; American Spinal Injury Association Impairment Scale A-D; 2-284 months post injury) participated in two testing sessions separated by an average of 2 days. During each testing session, aPWV measurements were collected in the supine position following 10 min of rest. Arterial blood pressure waveforms were collected simultaneously by two trained raters at the carotid and femoral arterial sites using applanation tonometry. Heart rate was continuously measured using a single-lead electrocardiogram, whereas brachial blood pressures were measured at 5-min intervals using an automated device. Results: Intra-and inter-tester aPWV measurements demonstrated almost perfect reliability with intraclass correlation coefficients of 0.91 and 0.98 (Po0.001), and coefficients of variation of 5.9% and 3.4%, respectively. The smallest detectable differences (SDDs) for intra-and inter-tester measurements were 0.9 m s À1 and 0.6 m s À1 , respectively. There were no significant differences in heart rate or blood pressure between intra-and inter-testing sessions. Conclusion: Applanation tonometry measurements of aPWV are reliable in individuals with SCI. In addition, the SDDs were smaller than a clinically relevant value, suggesting that this measurement is suitable for repeated measures study designs in SCI. Spinal Cord (2014) 52, 272-275; doi:10.1038/sc.2013.176; published online 21 January 2014 Keywords: arterial stiffness; blood pressure; cardiovascular diseases; reliability INTRODUCTION Cardiovascular disease (CVD) is a leading cause of mortality in individuals living with spinal cord injury (SCI), 1,2 with the incidence of CVD occurring at earlier ages compared with able-bodied individuals. 2 In able-bodied individuals, CVD risk is attributed to non-modifiable factors such as age and gender, and modifiable factors including blood pressure, blood lipid profile, smoking status, physical activity status, body composition and diabetes management. 3 Although individuals with SCI typically present with one or more modifiable risk factors, 2,4 there is evidence to suggest that these risk factors alone may not fully explain the increased risk of CVD in this population. 5 Consequently, future investigations need to examine alternative and non-traditional CVD risk factors for individuals with SCI.Aortic pulse wave velocity (aPWV), which describes the speed of the arterial pressure waveform between the carotid and femoral arterial sites, is considered the gold-standard assessment of arterial stiffness. 6 In able-bodied individuals, elevated aPWV, indicative of increased arterial stiffness, is associated with an increased risk of C...

Effects of exercise interventions on cardiovascular health in individuals with chronic, motor complete spinal cord injury: protocol for a randomised controlled trial [Cardiovascular Health/Outcomes: Improvements Created by Exercise and education in SCI (CHOICES) Study]

“…HR will be determined from concurrent single-lead electrocardiography (model ML 123, ADInstruments, Colorado Springs, Colorado, USA), while BP will be measured in triplicate (the mean will be used for analysis) from the left arm following data collection (Dinamap Carescape V100; GE Healthcare, Buckinghamshire, UK). We have previously demonstrated acceptable inter-rater and intra-rater reliability of this assessment for persons with SCI in our laboratory 47…”

“…Following a 4-hour fast, cfPWV will be measured in the supine position following 10 min of rest. Arterial pressure waveforms will be collected at the carotid and femoral arterial sites for a minimum of 30 s using applanation tonometry47 (model SPT-301; Millar Instruments, Houston, Texas, USA). Waveforms will be band-pass filtered (2–30 Hz) and the arrival of waveforms at each site will be identified as the minimum value of the filtered signal.…”

Metabolically healthy obesity and subclinical atherosclerosis in persons with spinal cord injury

“…Aortic stiffness was measured as carotid-femoral pulse wave velocity (PWV) using applanation tonometry (SphygmoCor; Atcor Medical, Sydney, Australia) according to current recommendations (17). Applanation tonometry measurements of PWV are reliable in individuals with SCI (18,19). The distance between the super-sternal notch and the carotid pulse-site, as well as the distance between the super-sternal notch and the femoral pulse-site, were measured using a standard tape measure.…”

Physical exercise improves arterial stiffness after spinal cord injury

“…4 A trained rater collected pulse pressure waveforms at the left carotid, and femoral arteries for a minimum of 30 seconds using a handheld tonometer (Model SPT-301; Millar Instruments Inc., Houston, TX, USA), as previously described. 9 Aortic PWV was calculated using the equation, PWV = (0.8 × D)/Δt where D is the distance between the carotid and femoral arterial sites measured along the body surface using anthropometric measuring tape held parallel to the body, and Δt is the pulse transit time between those sites. 4 Arterial pressure waveforms were bandpass filtered (2-30 Hz), and the arrival of the waveform at each site was identified as the minimum value of the filtered signal.…”