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Home > Research > Important Points from Research Articles:
- Introduction
- Faces of CFS - Case Histories of Chronic Fatigue Syndrome
- Postural hypotension and the anti-gravity suit
- Application of USAF G-Suit Technology for Clinical Orthostatic Hypotension: A Case Study
- Efficacy of compression of different capacitance beds in the amelioration of orthostatic hypotension
Important Points from Research Articles
These are points from the research that I thought were important when I read them. To see the whole research articles, please click the links provided.
Faces of CFS - Case Histories of Chronic Fatigue Syndrome by David S. Bell, MD, FAAP
. . . The myriad of symptoms revolving around exhaustion, weakness, lightheadedness, and inability to concentrate were likely due to the inability of the body to circulate blood to the brain when standing, or sometimes even sitting. When the CFS [Chronic Fatigue Syndrome] patient is lying down, the symptoms are improved, although not gone entirely. The disability of CFS has to do with the fact that we spend our non-sleeping lives in the upright position.
. . . He hypothesized that the pressure on Andrea's legs and abdomen by the MAST [military anti-shock trousers] trousers had forced a more vigorous blood flow through Andrea's brain, and that this increased blood flow stopped the pain. Andrea wanted to buy a pair of MAST trousers for home use. (Later on we actually tried this, but it turns out to be impossible to walk around with these things on which sort of cancels out the purpose.)
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Copyright © David S. Bell MD, 2000
Postural hypotension and the anti-gravity suit by Wilfrid H. Brook RFD, MB, BS(Melb), MS(Mon), FRCSEd, FICA
Also available to view as PDF/Adobe Acrobat format. (1.5 MB)
The use of water in applying external pressure to correct postural hypotension was reported by Stead and Ebert in 1941. They had two subjects with postural hypotension stand in water up to the level of the heart. With the water at this level the arterial pressure and the heart rate were essentially the same as when the subjects were lying down. As the level of the water was lowered, the arterial pressure fell progressively.
A similar discovery was made by the husband of the patient with the Shy-Drager syndrome reported in this paper. He found that his wife, confined to a wheelchair because of postural hypotension, could walk in a swimming pool with water up to the level of the heart. Unfortunately by the time the anti-G suit was fitted her neurological condition had so deteriorated that she was unable to walk.
The effective use of an air force anti-G suit in patients with postural hypotension has previously been described. A comparison between an air-filled suit (an experimental anti-G suit) and an elastic form of garment providing counterpressure showed that the air-filled suit was more effective in treating postural hypotension. As Burton has pointed out, the anti-G suit is not routinely used clinically to raise blood pressure, and it requires someone to suggest the role. The purpose of this paper is to draw attention to this clinical use of the anti-G suit.
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Copyright © 1994 by Australian Family Physician and Dr. Wilfrid H. Brook
Application of USAF G-Suit Technology for Clinical Orthostatic Hypotension: A Case Study
Also available to view as PDF/Adobe Acrobat format. (1.6 MB)
Lori L. Elizondo, B.S., Donald F. Doerr, B.S.E.E., Mark A. Sims, M.D., G. Wyckliffe Hoffler, M.D., and Victor A. Convertino, Ph.D.
. . . Blood pressures and heart rate were measured during three 5-min stand tests to assess orthostatic responses: a) without G-suit [control]; b) with noninflated G-suit; and c) with inflated G-suit (50 mm Hg). . .
. . . Upon standing, the IDDM [insulin dependent diabetes mellitus] patient demonstrated severe orthostatic hypotension (90 mm Hg SBP) [systolic blood pressure] and tachycardia without the G-suit. The G-suit, with and without pressure, reduced hypotension and tachycardia during standing. . .
Fig. 1. Stimulus-response relationship of the carotid-cardiac baroreflex in the IDDM patient (open triangles) compared to the average response of 11 healthy subjects before (closed circles) and after (open circles) 30 d of bedrest.
. . . With the noninflated (0 mm Hg) and inflated (50 mm Hg) G-suit, the reduction in SBP was 31-33 mm Hg, but remained at or above 125 throughout standing. . .
. . . The primary finding of this study was that the G-suit successfully compensated for these compromised mechanisms of blood pressure regulation in our IDDM patient by ameliorating orthostatic hypotension during passive standing without complicating the patient's supine hypertension. The success of the G-suit alone without pressure application may reflect the simple effectiveness of wearing tight-fitting garments in patients with conditions similar to those of our patient.
Our patient demonstrated complete carotid-cardiac baroreflex dysfunction compared to normal subjects before and after 30 d of bedrest confinement (Fig. 1). We are unaware of any previous studies to demonstrate this finding. Previous investigations using both human and animal models have demonstrated that impaired responsiveness of the vagally-mediated carotid-cardiac baroreflex response reduced the ability of subjects to adjust to transient reductions of blood pressure during standing and was associated with orthostatic incompetence. The findings from our IDDM patient were consistent with these data and extended this relationship to indicate that positive pressure applied to the lower extremities can compensate for this dysfunction.
. . . It is possible that G-suit effectiveness may be limited to specific abnormalities and may not be effective with other abnormalities. We believe our data are unique in that they are the first to our knowledge to identify specific physiological deficiencies of blood pressure regulation in a patient with IDDM; identification of these autonomic dysfunctions was important to our assessment of the effectiveness of the G-suit application in our patient independent of whether they were caused by the disease or secondary to drug therapy. Unexpectantly, our results also demonstrated the effectiveness of an anti-G suit without pressure application in compensating for these pathologies in our patient. This observation suggests that simple tight-fitting garments designed to apply pressure to the legs and abdomen without the requirement of air pressure sources can be equally effective in providing protection against orthostatic instability in these patients. Our results suggest that application of anti-G suit technology could prove effective in ameliorating orthostatic incompetence in individuals with combinations of moderate hypovolemia and complete impairment of carotid-cardiac baroreflex responsiveness and peripheral vasoconstriction without adversely affecting their supine hypertension. This finding is not only important to patients with idiopathic orthostatic hypotension, but could prove effective in astronauts returning from spaceflight who share in common the development of hypovolemia and carotid-cardiac baroreflex impairment.
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Reprint & Copyright © 1996 by Aerospace Medical Association, Alexandria, VA.
Efficacy of compression of different capacitance beds in the amelioration of orthostatic hypotension
Also available to view as PDF/Adobe Acrobat format. (1.4 MB)
J.-C. Denq MD, T.L. Opfer-Gehrking, M. Giuliani MD, J. Felten, V.A. Convertino PhD, and P.A. Low MD
We used a modified G suit to evaluate the effectiveness of compression of different capacitance beds. The aim of this study was to evaluate, in patients with chronic symptomatic OH [orthostatic hypotension], the differential efficacy of compression of the limbs versus the abdomen versus combined compression.
Visual analog scale: Individuals varied in their responses to compression. Ten of 14 patients chose All [bilateral calves and bilateral thighs and low abdomen] as the most efficacious maneuver in reducing their symptoms. Two of 14 chose Abdo [low abdomen] as the preferred compression (better than All). One patient preferred Calves alone. One patient did not feel there was any significant improvement with any of the compressions.
There was some individual variability in the response to regional compression, Figures 3 and 4 show two patterns of responses in two representative patients. In Figure 3, baseline recordings (no compression) show a large orthostatic fall in BP [blood pressure], with insignificant improvement with compression of either the calves or thighs. However, compression of both the calves and thighs (C + T), Abdo or All resulted in major amelioration of the orthostatic fall in BP. In Figure 4, a more graded response of compression is evident. Compression of Calves or Thighs was not beneficial. Some initial improvement was seen with C + T and Abdo. However, Abdo resulted in a progressive amelioration of orthostatic BP, whereas the improvement with C + T was not sustained. All resulted in a near total prevention of the orthostatic fall in BP.
The main findings of our study were that compression of capacitance beds will reduce the deficit in standing BP if both the legs and the abdomen (13/14; 93%) are compressed or if the abdomen alone is compressed (9/14; 64%). The improvement is due primarily to an increase in total peripheral resistance. The improvement in BP is accompanied by an improvement in orthostatic symptoms. Compression of the legs alone is much less beneficial.
The clinical implications of these observations are as follows. Some patients could be significantly helped by abdominal compression alone. These patients can wear a corset or abdominal binder, without resort to the application of compression stockings, which are difficult to put on, and are uncomfortable on hot and humid days. Patient who derive insufficient benefits from abdominal compression alone can benefit from the use of compression garments such as stockings that extend to the waist. Some patients need help only during periods of increased orthostatic stress. One modification is to use an inflatable abdominal binder, constructed using a large size sphygmomanometer.
Venous compression by a G suit positive pressure of 40 mmHg improves OH. Compression of all compartments is the most efficacious, followed by abdominal compression. The mechanism of improvement, in these patients with increased vascular capacity, is due primarily to an increase of PRI [peripheral resistance index].
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0959-9851 © 1997 Rapid Science Publishers
Information in brackets has been added.