Cerebrovascular Reactivity Evaluated by Transcranial Doppler: Reproducibility of Different Methods

Abstract

Transcranial Doppler is routinely used to assess the cerebrovascular reactivity, despite scarce information on its reproducibility. We evaluated the reproducibility of cerebrovascular reactivity measurements by this method utilizing different vasodilatory and vasoconstrictor stimuli. The cerebrovascular reactivity was measured in 45 healthy volunteers during hypercapnia induced by inhalation of a mixture of 5% CO₂ and 95% O₂, breath holding and rebreathing, and during hypocapnia induced by voluntary hyperventilation. Three sets of measurements were performed at times 0, 1, and 24 h to assess the within-observer short- and long-term reproducibility. The reproducibility was analyzed using the intraclass correlation coefficient. For the CO₂ inhalation method, a good short-term (r_I = 0.55; 95% CI = 0.39–0.68) and a good long-term (r_I = 0.43; 95% CI = 0.25–0.59) reproducibility was found. For the breath-holding method a good short-term agreement was found (r_I = 0.41; 95% CI = 0.22–0.57), while the long-term reproducibility was poor (r_I = 0.17; 95% CI = –0.03–0.36). Rebreathing showed a fair (r_I = 0.31; 95% CI = 0.11–0.48) short-term and a poor (r_I = 0.17; 95% CI = –0.03–0.36) long-term reproducibility. For voluntary hyperventilation, the short-term reproducibility was good (r_I = 0.53; 95% CI = 0.36–0.66), and the long- term reproducibility was fair (r_I = 0.31; 95% CI = 0.11–0.48). In our study, CO₂ inhalation and voluntary hyperventilation had the highest reproducibility and should be preferred when assessing cerebral vasoreactivity, especially in follow-up studies.

Both Nitric Oxide and Endothelin-1 Influence Cerebral Blood Flow Velocity at Rest and after Hyper- and Hypocapnic Stimuli in Hypertensive and Healthy Adolescents

“…In that study we also proved that pCO 2 in capillary blood does not change significantly during the BH test, whereas pCO 2 significantly decreases after HV (arterial samples were not drawn as it was considered to be unethical in healthy volunteers). Previous studies reported on satisfactory reproducibility of both methods and a good agreement with other vasodilatory testing using different stimuli [29,30] .…”

Transcranial Doppler estimation of cerebral blood flow and cerebrovascular conductance during modified rebreathing

“…The reproducibility of model parameters and estimates of CVMR are comparable with other Doppler-CO2 tests (44,45,48). Nonetheless, the coefficient of variation of the model parameter b was relatively large compared with the other parameters ( Table 2).…”

Hyperventilation-Induced Cerebrovascular Reactivity among Hypertensive and Healthy Adolescents

“…In a previous study we proved that pCO 2 in capillary blood does not change significantly during the breath-holding test, whereas pCO 2 significantly decreases after HV (arterial samples were not drawn as it was considered to be unethical in healthy volunteers) [36] . Previous studies reported on satisfactory reproducibility of both methods and a good agreement with other vasodilatory testing using different stimuli [37,38] .…”

“…Therefore, changes in blood flow velocities measured by transcranial Doppler sonography during hypocapnia reflect the increase of the vascular tone at the level of the cerebral arterioles and are proportional to changes of cerebral blood flow in the territory of the assessed artery. A good short-and long-term reproducibility of the HV-induced cerebral vasoreactivity responses was demonstrated previously [27] and the method has been used in different conditions for assessing cerebrovascular reactivity [28][29][30] .…”