Lower Body Negative Pressure: Physiological Effects, Applications, and Implementation

Abstract

This review presents lower body negative pressure (LBNP) as a unique tool to investigate the physiology of integrated systemic compensatory responses to altered hemodynamic patterns during conditions of central hypovolemia in humans. An early review published in Physiological Reviews over 40 yr ago (Wolthuis et al. Physiol Rev 54: 566–595, 1974) focused on the use of LBNP as a tool to study effects of central hypovolemia, while more than a decade ago a review appeared that focused on LBNP as a model of hemorrhagic shock (Cooke et al. J Appl Physiol (1985) 96: 1249–1261, 2004). Since then there has been a great deal of new research that has applied LBNP to investigate complex physiological responses to a variety of challenges including orthostasis, hemorrhage, and other important stressors seen in humans such as microgravity encountered during spaceflight. The LBNP stimulus has provided novel insights into the physiology underlying areas such as intolerance to reduced central blood volume, sex differences concerning blood pressure regulation, autonomic dysfunctions, adaptations to exercise training, and effects of space flight. Furthermore, approaching cardiovascular assessment using prediction models for orthostatic capacity in healthy populations, derived from LBNP tolerance protocols, has provided important insights into the mechanisms of orthostatic hypotension and central hypovolemia, especially in some patient populations as well as in healthy subjects. This review also presents a concise discussion of mathematical modeling regarding compensatory responses induced by LBNP. Given the diverse applications of LBNP, it is to be expected that new and innovative applications of LBNP will be developed to explore the complex physiological mechanisms that underline health and disease.

Cardiovascular biomarkers and echocardiographic findings at rest and during graded hypovolemic stress in women with recurrent vasovagal syncope

“…LBNP redistributes blood from the upper body to the lower extremities and is an excellent model for inducing hypovolemic circulatory stress, as well as widely used technique for evaluating responses to orthostatic stress and orthostatic tolerance . LBNP induces similar central hypovolemia as the in clinical routine used head‐up tilt test . A major advantage with the LBNP technique is that the subject's body position does not change when generating hypovolemic stress, facilitating hemodynamic monitoring, including measurements of CO.…”

“…LBNP redistributes blood from the upper body to the lower extremities and is an excellent model for inducing hypovolemic circulatory stress, 19 as well as widely used technique for evaluating responses to orthostatic stress and orthostatic tolerance. 5 [LTI = (ΔP 1 × t 1 ) + (ΔP 2 × t 2 ) + … (ΔP n × t n )], 21 for example, LTI in a subject withstanding LBNP stress test up to 2.5 minutes of LBNP 40mm Hg: (30 × 4) + (10 × 2.5) = 145 Δmm Hg · min.…”

Acute Effects of Whole-Body Vibration on Peripheral Blood Flow, Vibrotactile Perception and Balance in Older Adults

“…The corresponding eight-hour energy-equivalent frequency-weighted acceleration or A(8) values were 0.76 m/s 2 rms, 1.12 m/s 2 rms, and 1.41 m/s 2 rms, respectively, which were calculated according to the specifications mentioned in ISO 2631-1 [23]. To account for the effects of circadian rhythms and seasonal variations on physiological responses [30], we carried out the four experimental sessions randomly on four different days separated by at least 24 h, approximately at the same time for each subject, between 9.00 am and 4:00 pm during the winter season (November 2018-January 2019).…”

Evidence for misleading decision support in characterizing differences in tolerance to reduced central blood volume using measurements of tissue oxygenation

“…Valid application of the CRM algorithm to critically ill patients requires incorporation of data that represents potential individual confounding variables that could impact tolerance to reduced central blood volume such as that experienced by bleeding trauma patients. Such confounding variables include sex, age, relative anemia and physical fitness as well as hydration and prandial status . In this regard, we strategically included for algorithm development human subjects that represented both sexes across a wide range of age, race, ethnicity and fitness in normal states of hydration and nutrition.…”