The Pressor Response to the Drinking of Cold Water and Cold Carbonated Water in Healthy Younger and Older Adults.

Purpose: Water drinking has been proposed for the treatment of orthostatic hypotension because it can increase blood pressure in patients. This study aimed to investigate whether drinking water with a cold or carbonation stimulus would cause a more effective pressor response, and whether it would be greater in older than in younger adults. Methods: We assessed blood pressure and heart rate from non-invasive arterial pressure (a volume-clamp method) and type II electrocardiography in 13 healthy young adults (6 females, 7 males; mean age, 19.9 ± 1.1 years) and nine healthy older adults (all females; mean age, 71.4 ± 4.2 years) who drank 200 mL of cold, cold carbonated, and room temperature water. Results: The pressor response to the drinking of cold and cold carbonated water was greater than that to room temperature water in both younger and older participants (p < 0.05; changes in systolic blood pressure of room temperature water, cold water and cold carbonated water in young: 15.31 ± 9.66, 22.56 ± 11.51 and 32.6 ± 17.98 mmHg, respectively; changes in systolic blood pressure of room temperature water, cold water and cold carbonated water in elderly: 21.84 ± 14.31, 41.53 ± 19.82 and 48.16 ± 16.77 mmHg, respectively). In addition, the pressor response to cold and cold carbonated water was persistent during the recovery period by about 5-10 mmHg (p < 0.05). Furthermore, the pressor response during the drinking and recovery periods was greater in the older than in the younger participants (p < 0.05). Conclusion: Our data suggest that even smaller amounts of water are able to elicit a sustained pressor response, in particular if the water is cold and carbonated. We speculate that the pressor effect may render cold and carbonated water an appropriate first aid method against certain forms of acute hypotension.

Assessment of effects of differences in trunk posture during Fowler's position on hemodynamics and cardiovascular regulation in older and younger subjects.

BACKGROUND: Downward shifts in blood volume with changing position generally cause tachycardic responses. Age-related decreases in vagal nerve activity could contribute to orthostatic hypotension in older individuals. Fowler's position is a reclined position with the back between 30° and 60°, used to facilitate breathing, eating, and other routine daily activities in frail and elderly patients. OBJECTIVE: This study examined whether stroke volume (SV) was higher and heart rate (HR) lower in Fowler's position with an upright upper trunk than in Fowler's position with the whole trunk upright in both older and younger subjects, based on the assumption that lower HR would result from reduced sympathetic activation in older individuals. METHODS: We assessed hemodynamics and HR variability from electrocardiography, noninvasive arterial pressure and impedance cardiography in 11 younger male subjects (age range, 20-22 years) and 11 older male subjects (age range, 64-79 years), using three positions: supine, or Fowler's positions with either 30° of lower trunk inclination and 60° of upper trunk inclination (UT60) or 60° of whole trunk inclination (WT60). Comparisons were then made between age groups and between positions. RESULTS: Reductions in SV and tachycardic response were smaller with UT60 than with WT60, in both younger and older subjects. In addition, reduced tachycardic response with upright upper trunk appeared attributable to decreased vagal withdrawal in younger subjects and to reduced sympathetic activation in older subjects. CONCLUSION: Our findings indicate that an upright upper trunk during Fowler's position allowed maintenance of SV and inhibited tachycardic response compared to an upright whole trunk regardless of age, although the autonomic mechanisms underlying tachycardic responses differed between younger and older adults. An upright upper trunk in Fowler's position might help to reduce orthostatic stress and facilitate routine activities and conversation in frail patients.

Effects of trunk posture in Fowler's position on hemodynamics.

We speculated that stroke volume would be higher and heart rate would be lower when the head and upper trunk were mainly upright in the Fowler's position. We therefore analyzed the effects of three trunk postures in Fowler's position on heart rate, blood pressure and circulatory volume. Heart rate (HR), blood pressure (BP), stroke volume (SV), cardiac output (Q), systemic vascular resistance (SVR), ejection time (ET) and pre-ejection period (PEP) were measured in 10 healthy male volunteers (mean age ± SEM, 20.7 ± 0.5 y; range, 19-23 y) while in three trunk postures in Fowler's position. Stroke volume and Q were measured using impedance cardiography. The three trunk postures were 30° of lower and upper trunk inclination (WT30°), 30° and 60° of lower and upper trunk inclination (UT 60°), respectively and 60° of upper and lower trunk inclination (WT60°). Both SV and ET were significantly higher and HR and PEP were lower at UT60° than at WT60° (p < 0.01) whereas these values did not significantly differ between WT30° and UT60° (p > 0.05). None of Q, SVR and BP significantly differed among the three conditions (p > 0.05). These findings suggested that SV and preload are higher when the upper trunk is upright (UT60°) than when the entire trunk is upright (WT60°) while in Fowler's position. In addition, Q might be maintained without increasing HR through vagal withdrawal when only the upper trunk is upright in healthy young males in Fowler's position.

Effect of upper torso inclination in Fowler's position on autonomic cardiovascular regulation.

The present study investigates autonomic cardiovascular regulation during postural changes while in Fowler's position. Respiratory sinus arrhythmia (RSA) and sequence baroreflex sensitivity (sBRS) were measured in 12 healthy individuals in three positions (Experiment 1). We also measured RSA, sBRS, tidal volume (TV), lung volume spectrum (LV spectrum), and transfer gain and phase between lung volume and RR interval (RSA-TF, RSATF-phase) in 11 healthy individuals in two positions (Experiment 2). All participants maintained respiratory frequency at 15 breaths/min. The three positions in Experiment 1 were 30°, 45°, and 60° of upper torso inclination with a lower torso inclination of 30° throughout all evaluations. The two positions in Experiment 2 were 30° and 60° of upper torso backrest inclination with a lower torso inclination of 30° throughout all evaluations. The results of Experiment 1 showed significantly higher RSA and sBRS at 60° and 45° than at 30°, whereas RR interval (RRI), systolic blood pressure (SBP), and diastolic blood pressure (DBP) did not differ significantly under any condition. The results of Experiment 2 showed that RSA, RSA-TF, sBRS, TV, and LV spectrum were significantly higher at 60° than at 30°, and that RRI, SBP, DBP, and the RSATF phase did not significantly differ under any condition. These findings suggested that slight flexion of the upper torso in Fowler's position activates respiratory function and increases the contribution of vagal nerve activity to the cardiovascular system in young participants under conditions of a fixed respiratory rate.