Background: COVID-19 has wide-ranging physiological effects, with many patients complaining of persistent asthenia following recovery from the acute phase of the infection. The frequent term for this is Long Haul COVID (LHC). While we have tools to measure effects on general physiology in human subjects, a metric for cerebral dysregulation is lacking. Cerebral blood flow (CBF) is closely regulated in the healthy young person. Dysregulation has been well described in many conditions, including Posterior Reversible Encephalopathy Syndrome (PRES), and is associated with neurological deficits. Cerebral Vasomotor Reactivity was used as a tool to assess this dysregulation.

Methods: Transcranial Doppler (TCD) study for CVR was performed under the influence of Carbogen gas. A questionnaire collected prior to the procedure provided additional details on subjects demographics and COVID history. Cases and controls were recruited using self-reported questionnaire. Statistics involved assessing the reproducibility of the test as well as discovering differences between cases and control groups.

Results: CVR was assessed for 26 subjects. CBF velocity in the left MCA was analyzed at baseline, at peak Carbogen exposure, and in hypercapnic phase. The reproducibility of the test was established within the longitudinal repeated measures data. The cases and control groups were insignificant in difference at base level but significant when controlled for confounders. CVR was found to increase by 3.76 units in cases compared to controls. Confounders like BMI, gender and age was found significantly different between cases and controls. Number of COVID episodes and symptom severity was significant for CVR.

Conclusion: This simple bedside test was found to be to be effective in producing a reactivity among all the subjects and was homogenous in its effect irrespective of baseline subject differences. As a preliminary test, the test showed differences among cases and control groups. The sample for the test lacked sufficient power and observations. A bigger sample size and a subsequent longitudinal follow up may help better understand the use of CVR to screen high-risk population for cerebrovascular anomalies.

Date of publication

Summer 7-11-2023

Document Type




Persistent identifier


Committee members

Dr. William Sorensen, Ph. D.; Dr. Cheryl Cooper, Ph. D.; Dr. Arturo Arce-Esquivel, Ph. D.


Master of Science in Health Sciences