Squatting maneuver - an easy and efficient method to evaluate postural effect on human arterial blood pressure regulation.
To study the baroreceptor reflex and integrity of autonomic nervous system in man, we have been using number of methods to change the effective filling pressure of heart and the difference in response between the normal and changed filling pressure, especially failing circulation is being noted.  Filling pressure can be decreased by number of methods such as immediate change in posture from supine to standing, Valsalva maneuver, and venesection. However, to increase the filling pressure is very difficult. Earlier it is found that the children with cyanotic congenital heart disease used to squat when breathless but the reason was less studied. There is sudden and a prompt increase in cardiac output (CO) and arterial blood pressure (BP) due to squatting which is accompanied by an immediate decrease in heart rate (HR) and forearm vascular resistance. 
In the general population, about 20% of young subjects frequent complaints of light-headedness or even (near) syncope are reported to occur on standing after squatting [4,5] Thus to prevent syncope, squatting is a potent physical maneuver, however, a major drawback is that standing up from squatting is a large hemodynamic stressor that often causes new pre-syncopal symptoms.
To perform their morning rituals, people mostly of Indian population are mostly using squatting position. Furthermore, this posture is used for other daily activities such as micturition, bathing, washing, and sitting by most of the people. Complaints of light-headedness and even fainting on active standing are related to a marked transient fall in Arterial BP that also occurs in healthy subjects on active standing. [6-8] Comparable events are observed on arising from sitting [9-12] or squatting [13,14] This initial BP response to the upright position is exclusively associated with active rising.
In most of the previous studies, squatting position has been used to evaluate patients with Tetralogy of Fallot, individuals prone to vasovagal syncope, and heart transplant including diabetic cardiovascular autonomic neuropathy, and also been used as a therapeutic means to counteract the fall in BP in patients suffering from dizziness and orthostatic hypotension or presenting pre-syncope symptoms, such as soon after exercise. [15-19]
However, there have been very few studies using the squatting position as a diagnostic tool to evaluate the effect of this posture on BP regulation. Moreover, almost there are no studies in Indians where this position is used by most of the population frequently. [20-23] Hence, careful analysis of alteration in hemodynamic parameters during the transition from standing to squatting and from squatting to standing helps in the early detection of altered vagal and/or sympathetic function.
The present study has been designed to assess the validity of the observation and to give more stress on including squatting maneuver as one of the important postural methods to investigate the effect of posture on blood posture regulation.
The aims of the present review are to analyze the hemodynamic pattern during a squatting test in various situations and to describe what may be the negative and positive hemodynamic changes associated with this posture. We were, especially, interested in using the squatting test for the assessment of cardiovascular autonomic neuropathy associated with normal subjects.
Orthostatic hemodynamic alterations have been studied in much detail both in normal subjects and in those with autonomic dysfunction with a change in posture from supine to standing. Such a study is expected to clarify or confirm our overall observation regarding IOH onset after squatting as mentioned earlier and may throw some light on a possible triggering factor. Several practice guidelines, including the World Health Organization and the American Heart Association guidelines, recommend that BP should be routinely measured in the sitting or supine followed by the standing position provided that the arm of the patient is placed at the level of the right atrium in each position,  in practice, BP is often measured either in a sitting or supine position in a busy clinic or hospital ward. [24,25]
Aims and Objective
The aim of this study is to investigate the clinical value of a new non-invasive method for assessing baroreflex sensitivity using postural change after squatting and to confirm the role of the squatting test in the detection of early sympathetic neuropathy in normal subjects.
MATERIALS AND METHODS
This was a pretest/post-test study.
The sample size of 100 students between the age group of 18-25 years residing in Kalaburagi district was included in the study. Any subject with a case history of initial orthostatic hypotension or any orthopedic problem or inconvenience for squatting was excluded from the study.
The study was approved by the medical ethical committee of our institution. All the participants were clinically examined to rule out any systemic diseases. After explaining the complete study protocol, the written informed consent was obtained. Investigations took place in the afternoon, at least 1 h after lunch, in a room with a temperature of 37[degrees]C. After a 5 min rest on couch in supine position, a basal BP is recorded in the right upper limb in supine position, and subjects were instructed to stand-up immediately and record the BP in standing position immediately and the readings are noted.
Then, subjects are asked to squat for 2 min, and at the end of 1 min, BP is recorded in the right upper limb in squatting position and again subjects were asked to stand-up immediately, and BP was recorded in standing position and again difference is noted. To avoid the effect of diurnal variation in BP, readings are recorded at the same time of the day in the same room with same room temperature. To eliminate the effect of age, height and weight of these parameters were considered for statistical analysis.
All variables were checked for normal distribution. When normally distributed changes are expressed as mean and standard variation, otherwise as median and range. Changes in the hemodynamic variables during the maneuvers were tested by Paired t-test. A P < 0.05 was consider to indicate a statistically significant difference. For statistical analysis, SPSS software version 17.0 is used. The influence of age, gender, height, and weight on the effects of the maneuvers on hemodynamic variables was analyzed by Pearson's correlation.
The findings of the present study are depicted in Tables 1 and 2.
The present study has tested the hypothesis that the fall in the hemodynamic parameters, systolic, and diastolic BP is more significant during squatting to standing than supine to standing. As noted in the observation, the change in the position from supine to standing causes a fall in the systolic as well as diastolic BP which was not statistically significant (P values for systolic and diastolic BP difference were 0.2033 and 0.9921, respectively), whereas in another postural change that is change in position from squatting to standing, the fall in the systolic and diastolic BP was statistically significant (P values for systolic and diastolic BP difference were 0.0213 and 0.002, respectively).
Most of the data published in the literature focused mainly on standing to squatting and have been published. Later on studies done by Sharpey-Schafer and Alimi et al., the possible reason for the large BP fall after standing from a squat may be as follows. The leg and buttock muscles are active and there is a restriction of blood flow due to elevated intramuscular pressure compression of the vasculature during squatting. [26,27] This combination of compression of blood vessels, leading to relative ischemia and active muscle contraction, is likely to result in local vasodilatation of the leg and buttock muscle vasculature. Further by Rossberg and Penaz and Krediet and Wieling added that on standing and loss of compression of the legs, there would be an immediate reduction in leg vascular resistance due to already existing locally mediated vasodilatation. [26-29] Moreover, also supported by studies by Tschakovsky and Sheriff as the muscular effort involved in standing up from a squat position is considerable, it has been demonstrated that rapid vasodilatory mechanisms act in proportion to contraction intensity.  This would be expected to cause further vasodilatation. It would therefore be expected that lower limb vasodilatation would be greater in standing up from a squat than from supine or sitting. The combination of the two factors results in a rapid translocation of a large amount of arterial blood from the chest to the distensible venous capacitance system below the diaphragm.
Borst et al., Sprangers et al., Tanaka et al., Wieling et al. suggested that healthy teenagers and young adult subjects using the beat-to-beat measurement of stroke volume with calculation of CO and systemic vascular resistance (SVR) have established that CO actually increases with the onset of standing up, whereas SVR falls markedly. [31-34]
This study confirms the findings suggested by Tschakovsky et al. and Rossberg and Penaz that the fall in BP after arising from squatting is based primarily on a fall in SVR. [35,36] In accordance with the previous studies in healthy young adults, the CO at the moment of the nadir was increased, however, for the large initial fall in BP on standing after supine rest, the hemodynamic mechanism can be either a large fall in CO or in SVR. CO at the moment of the nadir after standing from supine was, in contrast to arising from squatting, tended to be lower. The rapid dilatation in leg muscles on arising from a squatting position can be attributed to the combination of relative ischemia due to compression of blood vessels, active muscle contraction, and elevated lower limb arteriovenous pressure gradient.
Syncopal episodes can be embarrassing, cause injuries, and have a profound impact on the quality of patients' lives. A clear explanation of the underlying mechanism and avoidance of the main trigger (rapid rise) are the principal treatment options. Understanding the pathophysiology provides the rationale for advising patients to rise slowly from supine, especially at night, and possibly sitting at the edge of the bed first. Changing provoking medication regimens that interfere with rapid BP control, such as [alpha]-blockers should be considered. Considering the Indian scenario, this research work alerts clinicians and clinician scientists to a common, yet often neglected condition that occurs only on an active change of posture and discusses its epidemiology, pathophysiology, and management.
The result of prompt squatting is an increase of the venous return and the arterial resistance. Consequences are increasing of the end-diastolic and systolic chamber pressure, stroke volume, and average arterial BP as well as decreasing of the frequency of the pulse controlled by baroreceptor.
For IOH on standing after supine rest, the hemodynamic mechanism can be either a large fallin CO or in SVR, and for IOH on arising from squatting, a large fall in SVR is a consistent finding.
The BP responses observed after both squatting and standing are thought to be of reflex nature and may be useful to assess the functional integrity of parasympathetic and sympathetic nerves in diabetes.
The intrinsic orthostatic load of the squatting test, which is greater than conventional postural maneuvers, makes the squatting test an easy and useful test to detect early orthostatic dysregulation.
[1.] Scheen AJ, Philips JC. Squatting test: A dynamic postural manoeuvre to study baroreflex sensitivity. Clin Auton Res. 2012;22(1):35-41.
[2.] Sharpey-Schafer EP. Effect of squatting on normal and failing circulation. Br Med J. 1956;1(4975):1072-4.
[3.] Hanson P, Slane PR, Rueckert PA, Clark SV. Squatting revisited: Comparison of haemodynamic responses in normal individuals and heart transplantation recipients. Br Heart J. 1995;74(2):154-8.
[4.] Task Force for the Diagnosis and Management of Syncope; European Society of Cardiology (ESC); European Heart Rhythm Association (EHRA); Heart Failure Association (HFA); Heart Rhythm Society (HRS), Moya A, Sutton R, Ammirati F, Blanc JJ, Brignole M, et al. Guidelines for the diagnosis and management of syncope (version 2009). Eur Heart J. 2009;30(21):2631-71.
[5.] Stewart JM. Transient orthostatic hypotension is common in adolescents. J Pediatr. 2002;140(4):418-24.
[6.] Sprangers RL, Wesseling KH, Imholz AL, Imholz BP, Wieling W. Initial blood pressure fall on stand up and exercise explained by changes in total peripheral resistance. J Appl Physiol. 1991;70(2):523-30.
[7.] Borst C, van Brederode JF, Wieling W, van Montfrans GA, Dunning AJ. Mechanisms of initial blood pressure response to postural change. Clin Sci (Lond). 1984;67(3):321-7.
[8.] Borst C, Wieling W, van Brederode JF, Hond A, de Rijk LG, Dunning AJ. Mechanisms of initial heart rate response to postural change. Am J Physiol. 1982;243(5):H676-81.
[9.] Imholz BP, Settels JJ, van der Meiracker AH, Wesseling KH, Wieling W. Non-invasive continuous finger blood pressure measurement during orthostatic stress compared to intra-arterial pressure. Cardiovasc Res. 1990;24(3):214-21.
[10.] Sprangers RL, van Lieshout JJ, Karemaker JM, Wesseling KH, Wieling W. Circulatory responses to stand up: Discrimination between the effects of respiration, orthostasis and exercise. Clin Physiol. 1991;11(3):221-30.
[11.] Rossberg F, Penaz J. Initial cardiovascular response on change of posture from squatting to standing. Eur J Appl Physiol Occup Physiol. 1988;57(1):93-7.
[12.] Holmgren A. Circulatory changes during muscular work in man; With special reference to arterial and central venous pressures in the systemic circulation. Scand J Clin Lab Invest. 1956;8 Suppl 24:1-97.
[13.] Wieling W, Harms MP, ten Harkel AD, van Lieshout JJ, Sprangers RL. Circulatory response evoked by a 3 s bout of dynamic leg exercise in humans. J Physiol. 1996;494:601-11.
[14.] Krediet CT. Initial orthostatic hypotension in a 37-year old horse rider. Clin Auton Res. 2002;12(5):404.
[15.] Krediet CT, Go-Schon IK, Kim YS, Linzer M, Van Lieshout JJ, Wieling W. Management of initial orthostatic hypotension: Lower body muscle tensing attenuates the transient arterial blood pressure decrease upon standing from squatting. Clin Sci (Lond). 2007;113(10):401-7.
[16.] Krediet CT, de Bruin IG, Ganzeboom KS, Linzer M, van Lieshout JJ, Wieling W. Leg crossing, muscle tensing, squatting, and the crash position are effective against vasovagal reactions solely through increases in cardiac output. J Appl Physiol. 2005;99(5):1697-703.
[17.] Krediet CT, Go-Schon IK, van Lieshout JJ, Wieling W. Optimizing squatting as a physical maneuver to prevent vasovagal syncope. Clin Auton Res. 2008;18(4):179-86.
[18.] van Dijk N, de Bruin IG, Gisolf J, de Bruin-Bon HA, Linzer M, van Lieshout JJ, et al. Hemodynamic effects of leg crossing and skeletal muscle tensing during free standing in patients with vasovagal syncope. J Appl Physiol. 2005;98(2):584-90.
[19.] Philips JC, Scheen AJ. Squatting test: A posture to study and counteract cardiovascular abnormalities associated with autonomic dysfunction. Auton Neurosci. 2011;162(1-2):3-9.
[20.] Cicolini G, Pizzi C, Palma E, Bucci M, Schioppa F, Mezzetti A, et al. Differences in blood pressure by body position (supine, fowler's, and sitting) in hypertensive subjects. Am J Hypertens. 2011;24(10):1073-9.
[21.] Philips JC, Marchand M, Scheen AJ. Squatting, a posture test for studying cardiovascular autonomic neuropathy in diabetes. Diabetes Metab. 2011;37(6):489-96.
[22.] Philips JC, Marchand M, Scheen AJ. Haemodynamic changes during a squat test, pulsatile stress and indices of cardiovascular autonomic neuropathy in patients with long-duration Type 1 diabetes. Diabetes Metab. 2012;38(1):54-62.
[23.] Pickering TG, Hall JE, Appel LJ, Falkner BE, Graves J, Hill MN, et al. Recommendations for blood pressure measurement in humans and experimental animals: Part 1: Blood pressure measurement in humans: A statement for professionals from the Subcommittee of Professional and Public Education of the American Heart Association Council on High Blood Pressure Research. Circulation. 2005;111(5):697-716.
[24.] Beevers G, Lip GY, O'Brien E. ABC of hypertension. Blood pressure measurement. Part I-sphygmomanometry: Factors common to all techniques. BMJ. 2001;322(7292):981-5.
[25.] Sharpey-Schafer EP. Effects of squatting on the normal and failing circulation. Br Med J. 1956;1(4975):1072-4.
[26.] Alimi YS, Barthelemy P, Juhan C. Venous pump of the calf: A study of venous and muscular pressures. J Vasc Surg. 1994;20(5):728-35.
[27.] Krediet CT, Wieling W. Initial orthostatic hypotension by rising to erect from squatting. In: Esquirias B, Brignole M, Garcia-Civera R, Moya A, Granell R, Wieling W, editors. Syncope Cases. Oxford: Blackwell Publishers; 2006. p. 123-5.
[28.] Tschakovsky ME, Sheriff DD. Immediate exercise hyperemia: Contributions of the muscle pump vs. Rapid vasodilation. J Appl Physiol (1985). 2004;97(2):739-47.
[29.] Tanaka H, Sjoberg BJ, Thulesius O. Cardiac output and blood pressure during active and passive standing. Clin Physiol. 1996;16(2):157-70.
[30.] Tschakovsky ME, Matusiak K, Vipond C, McVicar L. Lower limb-localized vascular phenomena explain initial orthostatic hypotension upon standing from squat. Am J Physiol Heart
Circ Physiol. 2011;301(5):H2102-12.
[31.] Stewart JM, Clarke D. "He's dizzy when he stands up": An introduction to initial orthostatic hypotension. J Pediatr. 2011;158(3):499-504.
[32.] Linzer M, Gold DT, Pontinen M, Divine GW, Felder A, Brooks WB. Recurrent syncope as a chronic disease: Preliminary validation of a disease-specific measure of functional impairment. J Gen Intern Med. 1994;9(4):181-6.
[33.] van Dijk N, Sprangers MA, Colman N, Boer KR, Wieling W, Linzer M. Clinical factors associated with quality of life in patients with transient loss of consciousness. J Cardiovasc Electrophysiol. 2006;17(9):998-1003.
[34.] Postprandial reduction in blood pressure in the elderly. N Engl J Med. 1983;309(20):1255-6.
[35.] Wilt TJ, Macdonald R, Rutks I. WITHDRAWN: Tamsulosin for benign prostatic hyperplasia. Cochrane Database Syst Rev. 2011;9:CD002081.
[36.] Coupland NJ, Bailey JE, Wilson SJ, Horvath R, Nutt D. The effects of clonidine on cardiovascular responses to standing in healthy volunteers. Clin Auton Res. 1995;5(3):171-7.
Nilesh N Kate, Chandrakala B S, Abida Farheen, Arshiya Zeba
Department of Physiology, ESIC Medical College and Hospital, Gulbarga, Karnataka, India
Correspondence to: Nilesh N Kate, E-mail: firstname.lastname@example.org
Received: Jun 02, 2017; Accepted: Jun 16, 2017
How to cite this article: Kate NN, Chandrakala BS, Farheen A, Zeba A. Squatting maneuver - an easy and efficient method to evaluate postural effect on human arterial blood pressure regulation. Natl J Physiol Pharm Pharmacol 2017;7(11): 1177-1181.
Source of Support: Nil, Conflict of Interest: None declared.
Table 1: Changes in mean values of systolic and diastolic BP from supine to standing Parameters Systolic BP Diastolic BP Supine 111.9[+ or -]0.8379 75.98[+ or -]0.6845 Standing 106.9[+ or -]0.9521 74.26[+ or -]0.6852 Difference 5.050[+ or -]1.268 1.723[+ or -]0.9685 P value 0.2033 0.9921 Significance NS NS BP: Blood pressure, NS: Non-significant Table 2: Changes in the mean values of systolic and diastolic BP from squatting to standing Parameters Systolic BP Diastolic BP Squatting 125.6[+ or -]1.121 85.35[+ or -]0.9545 Standing 109.7[+ or -]0.8893 75.82[+ or -]0.6986 Difference 15.88[+ or -]1.431 9.525[+ or -]1.183 P value 0.0213 0.002 Significance Significant Highly significant BP: Blood pressure
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|Title Annotation:||RESEARCH ARTICLE|
|Author:||Kate, Nilesh N.; Chandrakala, B.S.; Farheen, Abida; Zeba, Arshiya|
|Publication:||National Journal of Physiology, Pharmacy and Pharmacology|
|Date:||Nov 1, 2017|
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