Comparison of a 20 degree and 70 degree tilt test in adolescent ME/CFS patients, 2023, van Campen, Rowe, Visser

[Andy]

Introduction: During a standard 70-degree head-up tilt test, 90% of adults with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) develop an abnormal reduction in cerebral blood flow (CBF). A 70-degree test might not be tolerated by young ME/CFS patients because of the high incidence of syncopal spells. This study examined whether a test at 20 degrees would be sufficient to provoke important reductions in CBF in young ME/CFS patients.

Methods: We analyzed 83 studies of adolescent ME/CFS patients. We assessed CBF using extracranial Doppler measurements of the internal carotid and vertebral arteries supine and during the tilt. We studied 42 adolescents during a 20 degree and 41 during a 70 degree test.

Results: At 20 degrees, no patients developed postural orthostatic tachycardia (POTS), compared to 32% at 70 degrees (p = 0.0002). The CBF reduction during the 20 degree tilt of −27(6)% was slightly less than during the reduction during a 70 degree test [−31(7)%; p = 0.003]. Seventeen adolescents had CBF measurements at both 20 and 70 degrees. The CBF reduction in these patients with both a 20 and 70 degrees test was significantly larger at 70 degrees than at 20 degrees (p < 0.0001).

Conclusions: A 20 degree tilt in young ME/CFS patients resulted in a CBF reduction comparable to that in adult patients during a 70 degree test. The lower tilt angle provoked less POTS, emphasizing the importance of using the 70 degree angle for that diagnosis. Further study is needed to explore whether CBF measurements during tilt provide an improved standard for classifying orthostatic intolerance.

Open access, https://www.frontiersin.org/articles/10.3389/fped.2023.1169447/full

 

[Hutan]

The CBF reduction during the 20 degree tilt of −27(6)% was slightly less than during the reduction during a 70 degree test [−31(7)%; p = 0.003].

That's really quite remarkable, that such a low deviation from supine can cause that amount of reduction in cerebral blood flow. From the abstract, I think this study is worth a close read, to assess how water-tight the finding is, how long that measurement was sustained. Could it perhaps just be a temporary alteration that healthy young people would also experience in the same conditions?

 

[Trish]

It does sound like an important finding. Do we have any information on cerebral blood flow reduction in healthy children and adults under the same conditions.

 

[Hutan]

Do we have any information on cerebral blood flow reduction in healthy children and adults under the same conditions.

Usefulness of an abnormal cardiovascular response during low-grade head-up tilt-test for ... adolescents with chronic fatigue ..., 2007, Wyller et al

Incredibly, it looks as though Wyller was all over this years ago.

 

[Hutan]

The tilts were 5 to 15 minutes long. The assessments were done as part of a clinical workup.

Figure 2 is the percentage reduction in cerebral blood flow for the 20 degree (turquoise) and 70 degree tilt (red).



Figure 3 is for the 17 patients who underwent a 20 degree tilt followed by a 70 degree tilt - again the percentage reduction in cerebral blood flow.


@Jonathan Edwards suggested for the Wyller study (linked above) that perhaps the cardiovascular changes are due to the patients feeling apprehensive about what is going to happen, while the healthy controls wouldn't have the same concerns. I guess it's possible that that has occurred with these measurements. The similarity of change between the 20 degree tilt and the 70 degree tilt perhaps points to that e.g. the nurse saying 'now we are going to tilt you and if you feel faint or dizzy, let us know and we'll stop the test' could well cause apprehension, regardless of whether the tilt is 20 or 70 degrees.

Could fear reduce cerebral blood flow, and as much as is indicated? Maybe. Googling, there's the suggestion that hyperventilation restricts blood vessels and so reduces blood flow throughout the body. But, anxiety is also reported to increase cerebral blood flow. So... I don't know.

 

[SNT Gatchaman]

For reference here's the graphic from the Wyller study at full scale, split for ease of viewing. These are aggregates of mean and range for the two groups. The thing that strikes me is the onset and offset changes in relation to the actual mechanical tilting (T0 and T900) in both patients (red) and controls (grey). Yes you can see some anticipatory change in HR in patients (+2 bpm), but most other measures are almost digital: off then on. But look at the other end — on return to supine there is an immediate move to recovery in both patients and controls across all measures (there's only a brief descent in Mean Arterial Pressure in both). Interestingly, the patients don't seem to have an initial drop in MAP whereas controls do. Did their anticipatory HR rise maintain MAP? I favour this to represent a trained accomodation in the patients, rather than apprehension per se.

All experiments started at 9 A.M. and were carried out in a quiet room with dimmed lights and no windows. The ambient temperature was kept at about 23°C. The participants had been offered a light meal (1 or 2 pieces of bread, 1 glass of juice) 30 minutes before testing but were otherwise not allowed to eat or drink. They were lightly dressed.

The subjects lay supine on an electronically operated tilt table with foot-board support (model 900-00, CNSystems Medizintechnik, Graz, Austria). They were attached to the Task Force Monitor (model 3040i, CNSystems Medizintechnik), a combined hardware and software device for the noninvasive recording of cardiovascular variables.

Five-minute baseline recordings were obtained. Subjects were then head-up tilted 20° over approximately 10 seconds. They were maintained at 20° for 15 minutes and then tilted back to the horizontal position, after which the recordings were continued for another 5 minutes, making the total experimental period 25 minutes (Figure 1). Subjects were asked not to speak during the recording period.