Application of USAF G-suit technology for clinical orthostatic hypotension: a case study.
BACKGROUND
The purpose of this study was to determine the effectiveness of a USAF anti-gravity suit (G-suit) on the stability of a patient with chronic orthostatic hypotension.


METHODS
A 37-yr-old female with a history of insulin-dependent diabetes mellitus (IDDM) and symptomatic orthostasis was evaluated and the results were compared with those of non-diabetic controls, matched for age, height, and weight. Cardiac vagal tone was assessed by determination of standard deviation of 100 R-R intervals (R-R SD). We assessed the carotid-cardiac baroreflex response by plotting R-R intervals (ms) at each of eight neck pressure steps with their respective carotid distending pressures (mm Hg). Heart rate and blood pressure were recorded in response to the Valsalva maneuver (VM) performed at an expiratory pressure of 30 mmHg to assess integrated baroreflex responses. Blood pressures and heart rate were measured during three 5-min stand tests to assess orthostatic responses: a) without G-suit; b) with noninflated G-suit; and c) with inflated G-suit (50 mm Hg).


RESULTS
The IDDM patient had minimal baseline cardiac vagal tone (R-R SD = 8.5 ms) compared with the average response of a control group of 24 subjects with orthostatic stability (R-R SD = 67.2 +/- 7.1 ms). Carotid-cardiac baroreflex response was virtually non-existent in the IDDM patient (Gain = 0.06 ms.mm Hg-1) compared to the control subjects (4.4 +/- 0.8 ms.mm Hg-1). VM responses corroborated the lack of cardiac baroreflex response in the IDDM patient, while blood pressure changes during the VM were similar to those of the controls. Upon standing, the IDDM patient demonstrated severe orthostatic hypotension (90 mm Hg SBP) and tachycardia without the G-suit. The G-suit, with and without pressure, reduced hypotension and tachycardia during standing.


CONCLUSIONS
These results demonstrate successful application of Air Force technology as a useful alternative to pharmacologic intervention in the treatment of a patient with autonomic dysfunction leading to supine hypertension and orthostatic hypotension.
Clinical Science Division, Brooks Air Force Base, TX 78235-5117, USA.
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D000328:Adult; D000337:Aerospace Medicine; D001127:Arginine Vasopressin / Q000097:blood; D009320:Atrial Natriuretic Factor / Q000097:blood; D017704:Baroreflex / Q000502:physiology; D003925:Diabetic Angiopathies / Q000628:therapy*; D005260:Female; D018495:Fluid Shifts / Q000502:physiology; D005676:Gravity Suits; D006339:Heart Rate; D006801:Humans; D007024:Hypotension, Orthostatic / Q000628:therapy*; D009638:Norepinephrine / Q000097:blood; D010953:Plasma Volume; D012083:Renin / Q000097:blood; D014636:Valsalva Maneuver / Q000502:physiology; D014666:Vasomotor System / Q000502:physiology
D001127:Arginine Vasopressin; D009320:Atrial Natriuretic Factor; D012083:Renin; D009638:Norepinephrine