1
|
Burma JS, Seok J, Johnston NE, Smirl JD. Cerebral blood velocity during concurrent supine cycling, lower body negative pressure, and head-up tilt challenges: implications for concussion rehabilitation. Physiol Meas 2023; 44:084002. [PMID: 37531960 DOI: 10.1088/1361-6579/acecd4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Accepted: 08/02/2023] [Indexed: 08/04/2023]
Abstract
Introduction. The effect of concurrent head-up tilt and lower body negative pressure (LBNP) have been examined on middle cerebral artery velocity (MCAv) at rest; however, it is unknown the superimposed effect these factors have on blunting the elevation in cerebral blood velocity associated with moderate-intensity exercise.Methods. 23 healthy adults (11 females / 12 males, 20-33 years) completed three visits. The first consisted of a maximal ramp supine cycling test to identify the wattage associated with individualized maximal MCAv. Subsequent visits included randomized no LBNP (control) or LBNP at -40 Torr (experimental) with successively increasing head-up tilt stages of 0, 15, 30, and 45 degrees during the pre-described individualized wattage. Transcranial Doppler ultrasound was utilized to quantify MCAv. Two-factorial repeated measures analysis of variance with effect sizes were used to determine differences between days and tilt stages.Results. Between-day baseline values for MCAv, heart rate, and blood pressure displayed low variability with <5% variation. With no LBNP, MCAv was above baseline on average for all participants; however, 15 degrees and 30 degrees tilt with concurrent -40 Torr LBNP was sufficient to return MCAv to 100% of baseline values in females and males, respectively. Body-weight did not impact the association between tilt and pressure (R2range: 0.01-0.12).Conclusion. Combined LBNP and tilt were sufficient to reduce the increase in MCAv associated with moderate-intensity exercise. This exercise modality shows utility to enable individuals with a concussion to obtain the positive physiological adaptions associated with exercise while minimizing symptom exacerbation due to the notion of the Monro-Kellie doctrine.
Collapse
Affiliation(s)
- Joel S Burma
- Cerebrovascular Concussion Lab, Faculty of Kinesiology, University of Calgary, Alberta, Canada
- Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
- Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada
- Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
- Integrated Concussion Research Program, University of Calgary, Calgary, AB, Canada
| | - Jina Seok
- Cerebrovascular Concussion Lab, Faculty of Kinesiology, University of Calgary, Alberta, Canada
| | - Nathan E Johnston
- Cerebrovascular Concussion Lab, Faculty of Kinesiology, University of Calgary, Alberta, Canada
| | - Jonathan D Smirl
- Cerebrovascular Concussion Lab, Faculty of Kinesiology, University of Calgary, Alberta, Canada
- Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
- Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada
- Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
- Integrated Concussion Research Program, University of Calgary, Calgary, AB, Canada
| |
Collapse
|
2
|
Detection of a Stroke Volume Decrease by Machine-Learning Algorithms Based on Thoracic Bioimpedance in Experimental Hypovolaemia. SENSORS 2022; 22:s22145066. [PMID: 35890746 PMCID: PMC9316072 DOI: 10.3390/s22145066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 06/23/2022] [Accepted: 07/01/2022] [Indexed: 02/04/2023]
Abstract
Compensated shock and hypovolaemia are frequent conditions that remain clinically undetected and can quickly cause deterioration of perioperative and critically ill patients. Automated, accurate and non-invasive detection methods are needed to avoid such critical situations. In this experimental study, we aimed to create a prediction model for stroke volume index (SVI) decrease based on electrical cardiometry (EC) measurements. Transthoracic echo served as reference for SVI assessment (SVI-TTE). In 30 healthy male volunteers, central hypovolaemia was simulated using a lower body negative pressure (LBNP) chamber. A machine-learning algorithm based on variables of EC was designed. During LBNP, SVI-TTE declined consecutively, whereas the vital signs (arterial pressures and heart rate) remained within normal ranges. Compared to heart rate (AUC: 0.83 (95% CI: 0.73–0.87)) and systolic arterial pressure (AUC: 0.82 (95% CI: 0.74–0.85)), a model integrating EC variables (AUC: 0.91 (0.83–0.94)) showed a superior ability to predict a decrease in SVI-TTE ≥ 20% (p = 0.013 compared to heart rate, and p = 0.002 compared to systolic blood pressure). Simulated central hypovolaemia was related to a substantial decline in SVI-TTE but only minor changes in vital signs. A model of EC variables based on machine-learning algorithms showed high predictive power to detect a relevant decrease in SVI and may provide an automated, non-invasive method to indicate hypovolaemia and compensated shock.
Collapse
|
3
|
The effect of hypercapnia on regional cerebral blood flow regulation during progressive lower-body negative pressure. Eur J Appl Physiol 2020; 121:339-349. [PMID: 33089364 DOI: 10.1007/s00421-020-04506-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 09/19/2020] [Indexed: 10/23/2022]
Abstract
PURPOSE Previous work indicates that dynamic cerebral blood flow (CBF) regulation is impaired during hypercapnia; however, less is known about the impact of resting hypercapnia on regional CBF regulation during hypovolemia. Furthermore, there is disparity within the literature on whether differences between anterior and posterior CBF regulation exist during physiological stressors. We hypothesized: (a) lower-body negative pressure (LBNP)-induced reductions in cerebral blood velocity (surrogate for CBF) would be more pronounced during hypercapnia, indicating impaired CBF regulation; and (b) the anterior and posterior cerebral circulations will exhibit similar responses to LBNP. METHODS In 12 healthy participants (6 females), heart rate (electrocardiogram), mean arterial pressure (MAP; finger photoplethosmography), partial pressure of end-tidal carbon dioxide (PETCO2), middle cerebral artery blood velocity (MCAv) and posterior cerebral artery blood velocity (PCAv; transcranial Doppler ultrasound) were measured. Cerebrovascular conductance (CVC) was calculated as MCAv or PCAv indexed to MAP. Two randomized incremental LBNP protocols were conducted (- 20, - 40, - 60 and - 80 mmHg; three-minute stages), during coached normocapnia (i.e., room air), and inspired 5% hypercapnia (~ + 7 mmHg PETCO2 in normoxia). RESULTS The main findings were: (a) static CBF regulation in the MCA and PCA was similar during normocapnic and hypercapnic LBNP trials, (b) MCA and PCA CBV and CVC responded similarly to LBNP during normocapnia, but (c) PCAv and PCA CVC were reduced to a greater extent at - 60 mmHg LBNP (P = 0.029; P < 0.001) during hypercapnia. CONCLUSION CBF regulation during hypovolemia was preserved in hypercapnia, and regional differences in cerebrovascular control may exist during superimposed hypovolemia and hypercapnia.
Collapse
|
4
|
van Mil ACCM, Tymko MM, Kerstens TP, Stembridge M, Green DJ, Ainslie PN, Thijssen DHJ. Similarity between carotid and coronary artery responses to sympathetic stimulation and the role of α 1-receptors in humans. J Appl Physiol (1985) 2018; 125:409-418. [PMID: 29565771 DOI: 10.1152/japplphysiol.00386.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Carotid artery (CCA) dilation occurs in healthy subjects during cold pressor test (CPT), while the magnitude of dilation relates to cardiovascular risk. To further explore this phenomenon and mechanism, we examined carotid artery responses to different sympathetic tests, with and without α1-receptor blockade and assessed similarity to these responses between carotid and coronary arteries. In randomized order, 10 healthy participants (25 ± 3 yr) underwent sympathetic stimulation using the CPT (3-min left-hand immersion in ice-slush) and lower-body negative pressure (LBNP). Before and during sympathetic tests, CCA diameter and velocity (Doppler ultrasound) and left anterior descending (LAD) coronary artery velocity (echocardiography) were recorded across 3 min. Measures were repeated 90 min following selective α1-receptor blockade via oral prazosin (0.05 mg/kg body wt). CPT significantly increased CCA diameter, LAD maximal velocity, and velocity-time integral area-under-the-curve (all P < 0.05). In contrast, LBNP resulted in a decrease in CCA diameter, LAD maximal velocity, and velocity time integral (VTI; all P < 0.05). Following α1-receptor blockade, CCA and LAD velocity responses to CPT were diminished. In contrast, during LBNP (-30 mmHg), α1-receptor blockade did not alter CCA or LAD responses. Finally, changes in CCA diameter and LAD VTI responses to sympathetic stimulation were positively correlated ( r = 0.66, P < 0.01). We found distinct carotid artery responses to different tests of sympathetic stimulation, where α1 receptors partly contribute to CPT-induced responses. Finally, we found agreement between carotid and coronary artery responses. These data indicate similarity between carotid and coronary responses to sympathetic tests and the role of α1 receptors that is dependent on the nature of the sympathetic challenge. NEW & NOTEWORTHY We showed distinct carotid artery responses to cold pressor test (CPT; i.e., dilation) and lower-body negative pressure (LBNP; i.e., constriction). Blockade of α1-receptors significantly attenuated dilator responses in carotid and coronary arteries during CPT, while no changes were found during LBNP. Our findings indicate strong similarity between carotid and coronary artery responses to distinct sympathetic stimuli, and for the role of α-receptors.
Collapse
Affiliation(s)
- Anke C C M van Mil
- Department of Physiology, Radboudumc, Nijmegen , The Netherlands.,Research Institute for Sport and Exercise Sciences, Liverpool John Moores University , Liverpool , United Kingdom
| | - Michael M Tymko
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia , Kelowna , Canada
| | - Thijs P Kerstens
- Department of Physiology, Radboudumc, Nijmegen , The Netherlands
| | - Mike Stembridge
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia , Kelowna , Canada.,Cardiff School of Sport, Cardiff Metropolitan University , Cardiff , United Kingdom
| | - Daniel J Green
- School of Sports Science, Exercise and Health, the University of Western Australia , Nedlands , Australia
| | - Philip N Ainslie
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia , Kelowna , Canada
| | - Dick H J Thijssen
- Department of Physiology, Radboudumc, Nijmegen , The Netherlands.,Research Institute for Sport and Exercise Sciences, Liverpool John Moores University , Liverpool , United Kingdom
| |
Collapse
|