Counter pressure maneuvers for syncope prevention: A semi-systematic review and meta-analysis

Abstract

Physical counter pressure maneuvers (CPM) are movements that are recommended to delay or prevent syncope (fainting) by recruiting the skeletal muscle pump to augment cardiovascular control. However, these recommendations are largely based on theoretical benefit, with limited data evaluating the efficacy of CPM to prevent syncope in the real-world setting. We conducted a semi-systematic literature review and meta-analysis to assess CPM efficacy, identify literature gaps, and highlight future research needs. Articles were identified through a literature search (PubMed, April 2022) of peer-reviewed publications evaluating the use of counter pressure or other lower body maneuvers to prevent syncope. Two team members independently screened records for inclusion and extracted data. From 476 unique records identified by the search, 45 met inclusion criteria. Articles considered various syncopal conditions (vasovagal = 12, orthostatic hypotension = 8, postural orthostatic tachycardia syndrome = 1, familial dysautonomia = 2, spinal cord injury = 1, blood donation = 10, healthy controls = 11). Maneuvers assessed included hand gripping, leg fidgeting, stepping, tiptoeing, marching, calf raises, postural sway, tensing (upper, lower, whole body), leg crossing, squatting, "crash" position, and bending foreword. CPM were assessed in laboratory-based studies (N = 28), the community setting (N = 4), both laboratory and community settings (N = 3), and during blood donation (N = 10). CPM improved standing systolic blood pressure (+ 14.8 ± 0.6 mmHg, p < 0.001) and heart rate (+ 1.4 ± 0.5 bpm, p = 0.006), however, responses of total peripheral resistance, stroke volume, or cerebral blood flow were not widely documented. Most patients experienced symptom improvement following CPM use (laboratory: 60 ± 4%, community: 72 ± 9%). The most prominent barrier to employing CPM in daily living was the inability to recognize an impending faint. Patterns of postural sway may also recruit the skeletal muscle pump to enhance cardiovascular control, and its potential as a discrete, proactive CPM needs further evaluation. Physical CPM were successful in improving syncopal symptoms and producing cardiovascular responses that may bolster against syncope; however, practical limitations may restrict applicability for use in daily living.

Keywords: blood pressure; cardiovascular control; counter pressure maneuvers; orthostatic intolerance; postural sway; skeletal muscle pump; syncope.

Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Copyright © 2022 Williams, Khan and Claydon.

Figures

FIGURE 1

Effects of gravity on arterial and venous pressures in an upright, motionless human. Orthostatic arterial and venous pressures are shown on the left and right, respectively. With orthostasis, arterial and venous pressures above heart level decrease while pressures below the heart increase due to the gravitational redistribution of blood (venous pooling). The white inset diagram shows Starling forces of hydrostatic pressure (PHYD, light red shading; generated by the circulating blood pressure, which force fluid out of the vessel) and oncotic pressure (PONC, solid line; generated by plasma proteins, which promote fluid reabsorption) at the capillaries. In orthostasis, the increased lower extremity hydrostatic pressure (dark red shading, dashed line) promotes fluid loss at the capillaries and thus the accumulation of edema in the tissue. The combined venous pooling and capillary filtration reduce the effective circulating blood volume compromising cardiovascular control. Adapted from Hainsworth et al. (78).

FIGURE 2

The Skeletal Muscle Pump. (A) Pumping cycle of the skeletal muscle pump is shown. (1) Prior to contraction, venous valves are open, and blood freely enters the vessel. (2) Muscular contraction compresses the vessel, forcing blood through the superior valves, meanwhile inferior valves close to prevent backflow. (3) With relaxation, negative pressure closes the superior valves and blood is drawn into the vessel through the inferior valve in preparation for the next cycle. (B) Representative sample tracings of pressure responses to the crash position (top; squatting with the head placed between the knees), squatting (middle), and leg crossing performed with buttock and abdominal tensing (bottom). The patient performed these maneuvers following a vasovagal reaction accompanied by prodromal pallor and sweating. All three maneuvers successfully restored blood pressure. BP, blood pressure. Adapted from (A) OpenStax College, Anatomy and Physiology (133) (licensed under the Creative Commons Attribution 3.0 Unreported license) and Boron and Boulpaep, Medical Physiology (27), (B) Krediet et al. (134).

FIGURE 3

Semi-systematic method for literature review. The above flow diagram depicts our article selection process. Articles were screened at various levels (titles, abstracts, full text) to identify those that were relevant. Works were included if they evaluated the role of counter pressure and other lower body maneuvers in preventing syncope. Articles were selected for meta-analysis based on common themes amongst the article pool. Articles identified for our review that did not evaluate outcomes considered for meta-analysis were discussed in narrative form. POTS, postural orthostatic tachycardia syndrome.

FIGURE 4

Meta-analysis of cardiovascular responses to commonly prescribed counter pressure maneuvers. Responses of systolic arterial pressure [SAP, (A)] and heart rate [HR, (B)] are shown. The most highly studied counter pressure maneuvers were arm tensing (black), leg crossing (blue), leg crossing with muscle tensing (red), and squatting (gray). Data for each study are presented as the mean (circle) and standard deviation (whiskers), with the size of the circle proportional to the study sample size. Bolded whisker plots show the weighted (wt.) mean and standard deviation of group analyses. Vertical dotted lines indicate zero effect. The population considered is indicated to the right of each plot: vasovagal syncope (VVS), orthostatic hypotension (OH, included classical OH, and hypoadrenergic OH), and healthy controls (control).

FIGURE 5

Effects of counter pressure maneuvers on symptoms of syncope and presyncope. Bars show the proportion of patients (%) who reported recovered symptoms following counter pressure maneuver implementation in (A) the laboratory and (B) the community setting. White text indicates the counter pressure maneuvers investigated in each study. Vertical dotted lines indicate the pooled mean.

FIGURE 6

Kaplan–Meier syncope-free survival curve. Pooled time to first syncopal recurrence over a 1-year follow up in groups provided with usual care and trained in counter pressure maneuvers (CPM), and controls (usual care only) were compared (9, 87). Each study followed patients with vasovagal syncope who experienced prodromal symptoms prior to syncope. Data reported by Croci et al. (86) and Romme et al. (93), (dashed) did not include a control group and therefore were not included in combined analysis.

FIGURE 7

Relationships between postural sway and susceptibility to syncope. Data summarize relationships between postural sway behavior (measured as total path length or sway velocity), and cardiovascular control (measured as orthostatic tolerance, OT, time to presyncope in minutes during standard head upright tilt test with lower body negative pressure). Participant groups studied: patients with vasovagal syncope (VVS), healthy participants with good orthostatic tolerance (good OT), healthy participants with poor orthostatic tolerance (poor OT). Significant increases in the distance (A) and velocity (B) of postural sway are observed during quiet standing in individuals with poor OT who do not experience syncope in daily life, particularly in the AP direction. In patients with VVS, there is no such enhancement of postural sway to compensate for their orthostatic intolerance. The distance (C) and velocity (D) moved in the AP direction was significantly correlated with OT, where those with the lowest OT had greater postural sway. *Denotes significant difference where p < 0.05. ML, mediolateral component of sway; AP, anteroposterior component of sway. Adapted from Claydon and Hainsworth 2005 (111), and Claydon and Hainsworth (110).

FIGURE 8

Postural sway response to cerebral hypoperfusion. Repeated measures within-participant correlations between diastolic cerebral blood flow velocity deficit (dCBFv, quantified as the difference between dCBFv in the middle cerebral artery following the supine-stand transition and its baseline value in the supine posture before any intervention) and mean center of pressure vector (COPv) are shown. Analyses were performed among (A) all participants, and groups of (B) strong regulators only, or (C) weak regulators only, as identified through an a posteriori cluster analysis (112). The number of participants (n) included in each condition are shown at the top of each respective plot. Parallel slopes are fitted for each participant with ANCOVA using data from the 3 postural transitions, such that the overall model error is minimized. The repeated measures correlation coefficient (rrm) is derived from a ratio of the sum of squares. Adapted from Fitzgibbon-Collins et al. (112).

FIGURE 9

Cardio-postural causality. (A) Example tracing of simultaneously recorded systolic arterial pressure (SAP), calf electromyography (EMG), and center of pressure (COPr) signals. (B) Convergence plot of causality between signals over time during a quiet upright standing trial. Causality between signals, as calculated from the convergent cross mapping method (130, 135, 136), was measured on a scale between 0 and 1 (unitless). Gray shading indicates stabilization period following upright stance. Adapted from Verma et al. (137).