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

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 (P<0.001), 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(-1) and 0.6 m s(-1), 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.