Abstract
The physiological differences between active and passive changes in posture have been previously established. This study determined the extent of the differences in the initial cardiovascular responses to the passive head-up tilt (HUT) and the active squat-stand test (SST). Eleven females and 13 males underwent one +75° HUT and one SST. Beat-to-beat diastolic blood pressure (DBP), systolic blood pressure (SBP), mean arterial pressure (MAP) and heart rate (HR) were determined non-invasively. Data were recorded 10 s prior to (control) and 30 s after tilt or stand (event). Blood pressure and HR responses were analysed by calculating the deviation from control at 10 s (T10), 20 s (T20) and 30 s (T30) after the onset of each test. The DBP response (reflecting changes in systemic vascular resistance) at T10 was −10 (2) mmHg [mean (SEM)] for the HUT and −25 (2) mmHg for the SST (P<0.01). DBP returned to control levels by T30 for the HUT, but remained depressed for the SST. MAP responses directly reflected these changes in DBP. HR significantly increased from control values (P<0.001) for the HUT [+14 (1) bpm] and the SST [+16 (1) bpm], and remained elevated for the entire 30-s period for both tests. This study demonstrates that although the magnitude of the initial blood pressure decrease is greater for the active SST compared with the passive HUT, the reflex compensatory response is no different, making the SST a greater challenge for the cardiovascular reflexes.
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Barbey K, Brecht K, Kutscha W (1966) Uber die orthostatische Soforteaktion [On immediate orthostatic regulation]. Med Welt 17:1648–1653
Bland JM, Altman DG (1986) Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1:307–310
Blomqvist CG, Stone HL (1983) Cardiovascular adjustments to gravitational stress. In: Handbook of physiology. American Physiological Society, Besthesda, Md., pp 1025–1063
Borst C, Wieling W, Van Brederode JFM, Hond A, De Rijk LG, Dunning AJ (1982) Mechanisms of initial heart rate response to postural change. Am J Physiol 243:H676–H681
Charloux A, Lonsdorfer-Wolf E, Richard R, Lampert E, Oswald-Mammosser M, Mettauer B, Geny B, Lonsdorfer J (2000) A new impedence cardiograph device for the non-invasive evaluation of cardiac output at rest and during exercise: comparison with the "direct" Fick method. Eur J Appl Physiol 82:313–320
Convertino VA (1987) Aerobic fitness, endurance training and orthostatic intolerance. Exerc Sports Sci Rev 15:223–259
Convertino VA, Tripp LD, Ludwig DA, Duff J, Chelette TL (1998) Female exposure to high G: chronic adaptations of cardiovascular functions. Aviat Space Environ Med 69:875–882
De Mey C, Enterling D (1988) Noninvasive assessment of cardiac performance by impedence cardiography: disagreement between two equations to estimate stroke volume. Aviat Space Environ Med 59:57–62
El-Sayed H, Hainsworth R (1995) Relationship between plasma volume, carotid baroreceptor sensitivity and orthostatic tolerance. Clin Sci 88:463–470
Fulco CS, Cymerman A, Rock PB, Farese G (1985) Hemodynamic responses to upright tilt at sea level and high altitude. Aviat Space Environ Med 56:1172–1176
Gotshall RW, Davrath LR, Sadeh WZ, Coonts CC, Luckasen GJ, Downes TR, Tucker A (1999) Validation of impedence cardiography during lower body negative pressure. Aviat Space Environ Med 70:6–10
Graybiel A, McFarland RA (1941) The use of the tilt-table test in aviation medicine. J Aviat Med 12:194–211
Hainsworth R (1991) Reflexes from the heart. Physiol Rev 71:617–658
Hanson P, Slane PR, Rueckert PA, Clark SV (1995) Squatting revisited: comparison of haemodynamic responses in normal individuals and heart transplant recipients. Br Heart J 74:154–158
Hyatt KH, Jacobson LB, Schneider VS (1975) Comparison of 70° tilt, LBNP, and passive standing as measures of orthostatic tolerance. Aviat Space Environ Med 46:801–808
Imholz BPM, Wieling W, Montfrans GA van, Wesseling KH (1998) Fifteen years experience with finger arterial pressure monitoring: assessment of technology. Cardiovasc Res 38:605–616
Jellema WT, Imholz BPM, Van Goudoever J, Wesseling KH, Van Lieshout JJ (1996) Finger arterial versus intrabrachial pressure and continuous cardiac output during head-up tilt testing in healthy subjects. Clin Sci 91:193–200
Kautzner J, Hartikainen JEK, Camm AJ, Malik M (1996) Arterial baroreflex sensitivity assessed from phase IV of the Valsalva maneuver. Am J Cardiol 78:575–579
Lewis BS, Lewis N, Gotsman MS (1980) Effect of standing and squatting on echocardiographic left ventricular function. Eur J Cardiol 11:405–412
Lipsitz LA, Mukai S, Hamner J, Gagnon M, Babikian V (2000) Dynamic regulation of middle cerebral artery blood flow velocity in aging and hypertension. Stroke 31:1897–1903
Marfella R, Giugliano D, Maro G di, Acampora R, Giunta R, D'Onofrio F (1994) The squatting test: a useful tool to assess both parasympathetic and sympathetic involvement of the cardiovascular autonomic neuropathy in diabetes. Diabetes 43:607–612
Newman DG, White SW, Callister R (1998) Evidence of baroreflex adaptation to repetitive +Gz in fighter pilots. Aviat Space Environ Med 69:446–451
Newman DG, White SW, Callister R (2000) The effect of baroreflex adaptation on the dynamic cardiovascular response to head-up tilt. Aviat Space Environ Med 71:225–229
Raczak G, La Rovere MT, Pinna GD, Maestri R, Swiatecka G (2000) Assessment of baroreflex sensitivity in patients with preserved and impaired left ventricular function by means of the Valsalva manoeuvre and the phenylephrine test. Clin Sci 100:33–41
Richard R, Lonsdorfer-Wolf E, Charloux A, Doutreleau S, Buchheit M, Oswald-Mammosser M, Lampert E, Mettauer B, Geny B, Lonsdorfer J (2001) Non-invasive cardiac output evaluation during a maximal progressive exercise test, using a new impedence cardiograph device. Eur J Appl Physiol 85:202–207
Rickards CA, Newman DG (2002) The effect of low-level normobaric hypoxia on orthostatic responses. Aviat Space Environ Med 73:460–465
Rossberg R, Penaz J (1988) Initial cardiovascular response on change of posture from squatting to standing. Eur J Appl Physiol 57:93–97
Rowell LB (1986) Adjustments to upright posture and blood loss. In: Rowell L (ed) Human circulation: regulation during physical stress. Oxford University Press, New York, pp 137–173
Rowell LB (1993) Reflex control during orthostasis. In: Rowell L (ed) Human cardiovascular control. Oxford University Press, New York, pp 37–77
Spodick DH, Lance VQ (1977) Comparative orthostatic responses: standing versus head-up tilt. Aviat Space Environ Med 48:432–433
Sprangers RLH, Wesseling KH, Imholz ALT, Imholz BPM, Wieling W (1991) Initial blood pressure fall on stand up and exercise explained in total peripheral resistance. J Appl Physiol 70:523–530
Tanaka H, Sjoberg BJ, Thulesius O (1996) Cardiac output and blood pressure during active and passive standing. Clin Physiol 16:157–170
Van Lieshout JJ, Derk Jan Ten Harkel A, Wieling W (1992) Physical manoeuvres for combating orthostatic dizziness in autonomic failure. Lancet 11:897–898
Ward RJ, Danziger F, Bonica JJ, Allen GD, Tolas AG (1966) Cardiovascular effects of change of posture. Aerosp Med 33:257–259
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The authors thank the subjects who participated in this study for their time and co-operation. The experiments comply with the current laws of the country in which they were performed.
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Rickards, C.A., Newman, D.G. A comparative assessment of two techniques for investigating initial cardiovascular reflexes under acute orthostatic stress. Eur J Appl Physiol 90, 449–457 (2003). https://doi.org/10.1007/s00421-003-0852-0
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DOI: https://doi.org/10.1007/s00421-003-0852-0