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Guluzade NA, Huggard JD. Does central chemoreceptor blood flow increase with CO 2 tension? J Physiol 2024. [PMID: 38713148 DOI: 10.1113/jp286058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Accepted: 04/25/2024] [Indexed: 05/08/2024] Open
Affiliation(s)
- Nasimi A Guluzade
- School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
| | - Joshua D Huggard
- School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
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2
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Byrne DP, Studer N, Secombe C, Cieslewicz A, Hosgood G, Raisis A, Adler A, Mosing M. Validation of three-dimensional thoracic electrical impedance tomography of horses during normal and increased tidal volumes. Physiol Meas 2024; 45:035010. [PMID: 38422515 DOI: 10.1088/1361-6579/ad2eb3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2023] [Accepted: 02/29/2024] [Indexed: 03/02/2024]
Abstract
Objective. Data from two-plane electrical impedance tomography (EIT) can be reconstructed into various slices of functional lung images, allowing for more complete visualisation and assessment of lung physiology in health and disease. The aim of this study was to confirm the ability of 3D EIT to visualise normal lung anatomy and physiology at rest and during increased ventilation (represented by rebreathing).Approach. Two-plane EIT data, using two electrode planes 20 cm apart, were collected in 20 standing sedate horses at baseline (resting) conditions, and during rebreathing. EIT data were reconstructed into 3D EIT whereby tidal impedance variation (TIV), ventilated area, and right-left and ventral-dorsal centres of ventilation (CoVRLand CoVVD, respectively) were calculated in cranial, middle and caudal slices of lung, from data collected using the two planes of electrodes.Main results. There was a significant interaction of time and slice for TIV (p< 0.0001) with TIV increasing during rebreathing in both caudal and middle slices. The ratio of right to left ventilated area was higher in the cranial slice, in comparison to the caudal slice (p= 0.0002). There were significant effects of time and slice on CoVVDwhereby the cranial slice was more ventrally distributed than the caudal slice (p< 0.0009 for the interaction).Significance. The distribution of ventilation in the three slices corresponds with topographical anatomy of the equine lung. This study confirms that 3D EIT can accurately represent lung anatomy and changes in ventilation distribution during rebreathing in standing sedate horses.
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Affiliation(s)
- David P Byrne
- School of Veterinary Medicine, Murdoch University, Murdoch, Western Australia, Australia
| | | | - Cristy Secombe
- School of Veterinary Medicine, Murdoch University, Murdoch, Western Australia, Australia
| | | | - Giselle Hosgood
- School of Veterinary Medicine, Murdoch University, Murdoch, Western Australia, Australia
| | - Anthea Raisis
- School of Veterinary Medicine, Murdoch University, Murdoch, Western Australia, Australia
| | - Andy Adler
- Department of Systems and Computer Engineering, Carleton University, Ottowa, ON, Canada
| | - Martina Mosing
- Anaesthesia and Perioperative Intensive Care, Department of Companion Animals and Horses Vetmeduni, Vienna, Austria
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Guluzade NA, Huggard JD, Duffin J, Keir DA. A test of the interaction between central and peripheral respiratory chemoreflexes in humans. J Physiol 2023; 601:4591-4609. [PMID: 37566804 DOI: 10.1113/jp284772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Accepted: 07/25/2023] [Indexed: 08/13/2023] Open
Abstract
How central and peripheral chemoreceptor drives to breathe interact in humans remains contentious. We measured the peripheral chemoreflex sensitivity to hypoxia (PChS) at various isocapnic CO2 tensions (P C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ) to determine the form of the relationship between PChS and centralP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ . Twenty participants (10F) completed three repetitions of modified rebreathing tests with end-tidalP O 2 ${P_{{{\mathrm{O}}_{\mathrm{2}}}}}$ (P ET O 2 ${P_{{\mathrm{ET}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ) clamped at 150, 70, 60 and 45 mmHg. End-tidalP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ (P ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ),P ET O 2 ${P_{{\mathrm{ET}}{{\mathrm{O}}_{\mathrm{2}}}}}$ , ventilation (V ̇ $\dot{V}$ E ) and calculated oxygen saturation (SC O2 ) were measured breath-by-breath by gas-analyser and pneumotach. TheV ̇ $\dot{V}$ E -P ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ relationship of repeat-trials were linear-interpolated, combined, averaged into 1 mmHg bins, and fitted with a double-linear function (V ̇ $\dot{V}$ E S, L min-1 mmHg-1 ). PChS was computed at intervals of 1 mmHg ofP ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ as follows: the difference inV ̇ $\dot{V}$ E between the three hypoxic profiles and the hyperoxic profile (∆V ̇ $\dot{V}$ E ) was calculated; three ∆V ̇ $\dot{V}$ E values were plotted against corresponding SC O2 ; and linear regression determined PChS (Lmin-1 mmHg-1 %SC O2 -1 ). These processing steps were repeated at eachP ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ to produce the PChS vs. isocapnicP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ relationship. These were fitted with linear and polynomial functions, and Akaike information criterion identified the best-fit model. One-way repeated measures analysis of variance assessed between-condition differences.V ̇ $\dot{V}$ E S increased (P < 0.0001) with isoxicP ET O 2 ${P_{{\mathrm{ET}}{{\mathrm{O}}_{\mathrm{2}}}}}$ from 3.7 ± 1.5 L min-1 mmHg-1 at 150 mmHg to 4.4 ± 1.8, 5.0 ± 1.6 and 6.0 ± 2.2 Lmin-1 mmHg-1 at 70, 60 and 45 mmHg, respectively. Mean SC O2 fell progressively (99.3 ± 0%, 93.7 ± 0.1%, 90.4 ± 0.1% and 80.5 ± 0.1%; P < 0.0001). In all individuals, PChS increased withP ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ , and this relationship was best described by a linear model in 75%. Despite increasing central chemoreflex activation, PChS increased linearly withP ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ indicative of an additive central-peripheral chemoreflex response. KEY POINTS: How central and peripheral chemoreceptor drives to breathe interact in humans remains contentious. We measured peripheral chemoreflex sensitivity to hypoxia (PChS) at various isocapnic carbon dioxide tensions (P C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ) to determine the form of the relationship between PChS and centralP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ . Participants performed three repetitions of modified rebreathing with end-tidalP O 2 ${P_{{{\mathrm{O}}_{\mathrm{2}}}}}$ fixed at 150, 70, 60 and 45 mmHg. PChS was computed at intervals of 1 mmHg of end-tidalP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ (P ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ) as follows: the difference inV ̇ $\dot{V}$ E between the three hypoxic profiles and the hyperoxic profile (∆V ̇ $\dot{V}$ E ) was calculated; three ∆V ̇ $\dot{V}$ E values were plotted against corresponding calculated oxygen saturation (SC O2 ); and linear regression determined PChS (Lmin-1 mmHg-1 %SC O2 -1 ). In all individuals, PChS increased withP ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ , and this relationship was best described by a linear (rather than polynomial) model in 15 of 20. Most participants did not exhibit a hypo- or hyper-additive effect of central chemoreceptors on the peripheral chemoreflex indicating that the interaction was additive.
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Affiliation(s)
- Nasimi A Guluzade
- School of Kinesiology, The University of Western Ontario, London, ON, Canada
| | - Joshua D Huggard
- School of Kinesiology, The University of Western Ontario, London, ON, Canada
| | - James Duffin
- Department of Anaesthesia and Pain Management, University of Toronto, Toronto, ON, Canada
- Department of Physiology, University of Toronto, Toronto, ON, Canada
- Thornhill Research Inc., Toronto, ON, Canada
| | - Daniel A Keir
- School of Kinesiology, The University of Western Ontario, London, ON, Canada
- Toronto General Research Institute, Toronto General Hospital, Toronto, ON, Canada
- Lawson Health Research Institute, London, ON, Canada
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Carr JMJR, Day TA, Ainslie PN, Hoiland RL. The jugular venous-to-arterial P C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ difference during rebreathing and end-tidal forcing: Relationship with cerebral perfusion. J Physiol 2023; 601:4251-4262. [PMID: 37635691 DOI: 10.1113/jp284449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Accepted: 08/11/2023] [Indexed: 08/29/2023] Open
Abstract
We examined two assumptions of the modified rebreathing technique for the assessment of the ventilatory central chemoreflex (CCR) and cerebrovascular CO2 reactivity (CVR), hypothesizing: (1) that rebreathing abolishes the gradient between the partial pressures of arterial and brain tissue CO2 [measured via the surrogate jugular venousP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ and arterialP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ difference (Pjv-a CO2 )] and (2) rebreathing eliminates the capacity of CVR to influence the Pjv-a CO2 difference, and thus affect CCR sensitivity. We also evaluated these variables during two separate dynamic end-tidal forcing (ETF) protocols (termed: ETF-1 and ETF-2), another method of assessing CCR sensitivity and CVR. Healthy participants were included in the rebreathing (n = 9), ETF-1 (n = 11) and ETF-2 (n = 10) protocols and underwent radial artery and internal jugular vein (advanced to jugular bulb) catheterization to collect blood samples. Transcranial Doppler ultrasound was used to measure middle cerebral artery blood velocity (MCAv). The Pjv-a CO2 difference was not abolished during rebreathing (6.2 ± 2.6 mmHg; P < 0.001), ETF-1 (9.3 ± 1.5 mmHg; P < 0.001) or ETF-2 (8.6 ± 1.4 mmHg; P < 0.001). The Pjv-a CO2 difference did not change during the rebreathing protocol (-0.1 ± 1.2 mmHg; P = 0.83), but was reduced during the ETF-1 (-3.9 ± 1.1 mmHg; P < 0.001) and ETF-2 (-3.4 ± 1.2 mmHg; P = 0.001) protocols. Overall, increases in MCAv were associated with reductions in the Pjv-a CO2 difference during ETF (-0.095 ± 0.089 mmHg cm-1 s-1 ; P = 0.001) but not during rebreathing (-0.028 ± 0.045 mmHg · cm-1 · s-1 ; P = 0.067). These findings suggest that, although the Pjv-a CO2 is not abolished during any chemoreflex assessment technique, hyperoxic hypercapnic rebreathing is probably more appropriate to assess CCR sensitivity independent of cerebrovascular reactivity to CO2 . KEY POINTS: Modified rebreathing is a technique used to assess the ventilatory central chemoreflex and is based on the premise that the rebreathing method eliminates the difference between arterial and brain tissueP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ . Therefore, rebreathing is assumed to isolate the ventilatory response to central chemoreflex stimulation from the influence of cerebral blood flow. We assessed these assumptions by measuring arterial and jugular venous bulbP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ and middle cerebral artery blood velocity during modified rebreathing and compared these data against data from another test of the ventilatory central chemoreflex using hypercapnic dynamic end-tidal forcing. The difference between arterial and jugular venous bulbP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ remained present during both rebreathing and end-tidal forcing tests, whereas middle cerebral artery blood velocity was associated with theP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ difference during end-tidal forcing but not rebreathing. These findings offer substantiating evidence that clarifies and refines the assumptions of modified rebreathing tests, enhancing interpretation of future findings.
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Affiliation(s)
- Jay M J R Carr
- Centre for Heart, Lung and Vascular Health, University of British Columbia Okanagan, Kelowna, BC, Canada
| | - Trevor A Day
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, AB, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, University of British Columbia Okanagan, Kelowna, BC, Canada
| | - Ryan L Hoiland
- Centre for Heart, Lung and Vascular Health, University of British Columbia Okanagan, Kelowna, BC, Canada
- Department of Anesthesiology, Pharmacology and Therapeutics, Vancouver General Hospital, University of British Columbia, Vancouver, BC, Canada
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, BC, Canada
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Persson G, Lodin-Sundström A, Linér MH, Andersson SHA, Sjögreen B, Andersson JPA. Splenic contraction and cardiovascular responses are augmented during apnea compared to rebreathing in humans. Front Physiol 2023; 14:1109958. [PMID: 36960158 PMCID: PMC10028099 DOI: 10.3389/fphys.2023.1109958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Accepted: 02/22/2023] [Indexed: 03/09/2023] Open
Abstract
The spleen contracts during apnea, releasing stored erythrocytes, thereby increasing systemic hemoglobin concentration (Hb). We compared apnea and rebreathing periods, of equal sub-maximal duration (mean 137 s; SD 30), in eighteen subjects to evaluate whether respiratory arrest or hypoxic and hypercapnic chemoreceptor stimulation is the primary elicitor of splenic contraction and cardiovascular responses during apnea. Spleen volume, Hb, cardiovascular variables, arterial (SaO2), cerebral (ScO2), and deltoid muscle oxygen saturations (SmO2) were recorded during the trials and end-tidal partial pressure of oxygen (PETO2) and carbon dioxide (PETCO2) were measured before and after maneuvers. The spleen volume was smaller after apnea, 213 (89) mL, than after rebreathing, 239 (95) mL, corresponding to relative reductions from control by 20.8 (17.8) % and 11.6 (8.0) %, respectively. The Hb increased 2.4 (2.0) % during apnea, while there was no significant change with rebreathing. The cardiovascular responses, including bradycardia, decrease in cardiac output, and increase in total peripheral resistance, were augmented during apnea compared to during rebreathing. The PETO2 was higher, and the PETCO2 was lower, after apnea compared to after rebreathing. The ScO2 was maintained during maneuvers. The SaO2 decreased 3.8 (3.1) % during apnea, and even more, 5.4 (4.4) %, during rebreathing, while the SmO2 decreased less during rebreathing, 2.2 (2.8) %, than during apnea, 8.3 (6.2) %. We conclude that respiratory arrest per se is an important stimulus for splenic contraction and Hb increase during apnea, as well as an important initiating factor for the apnea-associated cardiovascular responses and their oxygen-conserving effects.
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Affiliation(s)
- Gustav Persson
- Department of Experimental Medical Science, Lund University, Lund, Sweden
- *Correspondence: Gustav Persson, ; Johan P. A. Andersson,
| | - Angelica Lodin-Sundström
- Department of Health Sciences, Mid Sweden University, Sundsvall, Sweden
- Department of Biology, Lund University, Lund, Sweden
| | - Mats H. Linér
- Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Samuel H. A. Andersson
- Department of Biology, Lund University, Lund, Sweden
- Department of Clinical Sciences, Malmö, Lund University, Lund, Sweden
| | | | - Johan P. A. Andersson
- Department of Experimental Medical Science, Lund University, Lund, Sweden
- *Correspondence: Gustav Persson, ; Johan P. A. Andersson,
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Guluzade NA, Huggard JD, Keltz RR, Duffin J, Keir DA. Strategies to improve respiratory chemoreflex characterization by Duffin's rebreathing. Exp Physiol 2022; 107:1507-1520. [PMID: 36177675 DOI: 10.1113/ep090668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 09/21/2022] [Indexed: 12/14/2022]
Abstract
NEW FINDINGS What is the central question of this study? We assessed the test-retest variability of respiratory chemoreflex characterization by Duffin's modified rebreathing method and explored whether signal averaging of repeated trials improves confidence in parameter estimation. What is the main finding and its importance? Modified rebreathing is a reproducible method to characterize responses of central and peripheral respiratory chemoreflexes. Signal averaging of multiple repeated tests minimizes within- and between-test variability, improves the confidence of chemoreflex characterization and reduces the minimal change in parameters required to establish an effect. Future experiments that apply this method might benefit from signal averaging to improve its discriminatory effect. ABSTRACT We assessed the test-retest variability of central and peripheral respiratory chemoreflex characterization by Duffin's modified rebreathing method and explored whether signal averaging of repeated trials improves confidence in parameter estimation. Over four laboratory visits, 13 participants (mean ± SD age, 25 ± 5 years) performed six repetitions of modified rebreathing in isoxic-hypoxic conditions [end-tidal P O 2 ${P_{{{\rm{O}}_{\rm{2}}}}}$ ( P ET , O 2 ${P_{{\rm{ET,}}{{\rm{O}}_{\rm{2}}}}}$ ) = 50 mmHg] and isoxic-hyperoxic conditions ( P ET , O 2 ${P_{{\rm{ET,}}{{\rm{O}}_{\rm{2}}}}}$ = 150 mmHg). End-tidal P C O 2 ${P_{{\rm{C}}{{\rm{O}}_{\rm{2}}}}}$ ( P ET , C O 2 ${P_{{\rm{ET,C}}{{\rm{O}}_{\rm{2}}}}}$ ), P ET , O 2 ${P_{{\rm{ET,}}{{\rm{O}}_{\rm{2}}}}}$ and minute ventilation ( V ̇ $\dot {\rm V}$ E ) were measured breath-by-breath, by gas analyser and pneumotachograph. The V ̇ $\dot {\rm V}$ E versus P ET , C O 2 ${P_{{\rm{ET,C}}{{\rm{O}}_{\rm{2}}}}}$ relationships were fitted with a piecewise model to estimate the ventilatory recruitment threshold (VRT) and the slope above the VRT ( V ̇ $\dot {\rm V}$ E S). Breath-by-breath data from the three within- and between-day trials were averaged using two approaches [simple average (fit then average) and ensemble average (average then fit)] and compared with a single-trial fit. Variability was assessed by intraclass correlation (ICC) and coefficient of variance (CV), and the minimal detectable change was computed for each approach using two independent sets of three trials. Within days, the VRT and V ̇ $\dot {\rm V}$ E S exhibited excellent test-retest variability in both hyperoxic conditions (VRT: ICC = 0.965, CV = 2.3%; V ̇ $\dot {\rm V}$ E S: ICC = 0.932, CV = 15.5%) and hypoxic conditions (VRT: ICC = 0.970, CV = 2.9%; V ̇ $\dot {\rm V}$ E S: ICC = 0.891, CV = 17.2%). Between-day reproducibility was also excellent (hyperoxia, VRT: ICC = 0.930, CV = 2.2%; V ̇ $\dot {\rm V}$ E S: ICC = 0.918, CV = 14.2%; and hypoxia, VRT: ICC = 0.940, CV = 3.0%; V ̇ $\dot {\rm V}$ E S: ICC = 0.880, CV = 18.1%). Compared with a single-trial fit, there were no differences in VRT or V ̇ $\dot {\rm V}$ E S using the simple average or ensemble average approaches; however, ensemble averaging reduced the minimal detectable change for V ̇ $\dot {\rm V}$ E S from 2.95 to 1.39 L min-1 mmHg-1 (hyperoxia) and from 3.64 to 1.82 L min-1 mmHg-1 (hypoxia). Single trials of modified rebreathing are reproducible; however, signal averaging of repeated trials improves confidence in parameter estimation.
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Affiliation(s)
- Nasimi A Guluzade
- School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
| | - Joshua D Huggard
- School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
| | - Randi R Keltz
- School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
| | - James Duffin
- Department of Anesthesiology and Pain Medicine, University of Toronto, Toronto, Ontario, Canada.,Department of Physiology, University of Toronto, Toronto, Ontario, Canada.,Thornhill Research Inc., Toronto, Ontario, Canada
| | - Daniel A Keir
- School of Kinesiology, The University of Western Ontario, London, Ontario, Canada.,Toronto General Research Institute, Toronto General Hospital, Toronto, Ontario, Canada.,Lawson Health Research Institute, London, Ontario, Canada
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Dhar M, Sharma S, Esquinas AM. Rebreathing of carbon dioxide during non-invasive ventilation. Is PEEP the final solution? Can J Respir Ther 2022; 58:169. [PMID: 36320681 PMCID: PMC9556029 DOI: 10.29390/cjrt-2022-054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Mridul Dhar
- Department of Anaesthesiology, All India Institute of Medical Sciences, Rishikesh, India
| | - Sameer Sharma
- Department of Anaesthesiology, All India Institute of Medical Sciences, Rishikesh, India
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Burma JS, Macaulay A, Copeland P, Khatra O, Bouliane KJ, Smirl JD. Comparison of cerebrovascular reactivity recovery following high-intensity interval training and moderate-intensity continuous training. Physiol Rep 2021; 8:e14467. [PMID: 32506845 PMCID: PMC7276190 DOI: 10.14814/phy2.14467] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2019] [Revised: 04/21/2020] [Accepted: 04/25/2020] [Indexed: 12/27/2022] Open
Abstract
A common inclusion criterion when assessing cerebrovascular (CVR) metrics is for individuals to abstain from exercise for 12–24 hr prior to data collections. While several studies have examined CVR during exercise, the literature describing CVR throughout post‐exercise recovery is sparse. The current investigation examined CVR measurements in nine participants (seven male) before and for 8 hr following three conditions: 45‐min moderate‐continuous exercise (at ~50% heart‐rate reserve), 25‐min high‐intensity intervals (ten, one‐minute intervals at ~85% heart‐rate reserve), and a control day (30‐min quiet rest). The hypercapnic (40–60 mmHg) and hypocapnic (25–40 mmHg) slopes were assessed via a modified rebreathing technique and controlled stepwise hyperventilation, respectively. All testing was initiated at 8:00a.m. with transcranial Doppler ultrasound measurements to index cerebral blood velocity performed prior to the condition (pre) with serial follow‐ups at zero, one, two, four, six, and eight hours within the middle and posterior cerebral artery (MCA, PCA). Absolute and relative MCA and PCA hypercapnic slopes were attenuated following high‐intensity intervals at hours zero and one (all p < .02). No alterations were observed in either hypocapnic or hypercapnic slopes following the control or moderate‐continuous exercise (all p > .13), aside from a reduced relative hypercapnic MCA slope at hours zero and one following moderate‐continuous exercise (all p < .005). The current findings indicate the common inclusion criteria of a 12–24 hr time restriction on exercise can be reduced to two hours when performing CVR measures. Furthermore, the consistent nature of the CVR indices throughout the control day indicate reproducible testing sessions can be made between 8:00a.m. and 7:00p.m.
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Affiliation(s)
- Joel S Burma
- Sport Concussion Research Lab, University of British Columbia, Kelowna, BC, Canada.,Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada.,Human Performance Laboratory, University of Calgary, Calgary, AB, Canada.,Integrated Concussion Research Program, University of Calgary, Calgary, AB, Canada
| | - Alannah Macaulay
- Sport Concussion Research Lab, University of British Columbia, Kelowna, BC, Canada
| | - Paige Copeland
- Sport Concussion Research Lab, University of British Columbia, Kelowna, BC, Canada
| | - Omeet Khatra
- Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Kevin J Bouliane
- Sport Concussion Research Lab, University of British Columbia, Kelowna, BC, Canada
| | - Jonathan D Smirl
- Sport Concussion Research Lab, University of British Columbia, Kelowna, BC, Canada.,Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada.,Human Performance Laboratory, University of Calgary, Calgary, AB, Canada.,Integrated Concussion Research Program, University of Calgary, Calgary, AB, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, AB, Canada.,Libin Cardiovascular Institute, University of Calgary, Calgary, AB, Canada
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9
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Gultyaeva VV, Uryumtsev DY, Zinchenko MI, Melnikov VN, Balioz NV, Krivoschekov SG. Cardiorespiratory Coordination in Hypercapnic Test Before and After High-Altitude Expedition. Front Physiol 2021; 12:673570. [PMID: 34108888 PMCID: PMC8181754 DOI: 10.3389/fphys.2021.673570] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Accepted: 04/16/2021] [Indexed: 12/12/2022] Open
Abstract
Coordination of cardiovascular and respiratory systems enables a wide range of human adaptation and depends upon the functional state of an individual organism. Hypoxia is known to elicit changes in oxygen and carbon dioxide sensitivity, while training alters cardiorespiratory coordination (CRC). The delayed effect of high altitude (HA) acclimatization on CRC in mountaineers remains unknown. The objective of this study was to compare CRC in acute hypercapnia in mountaineers before and after a HA expedition. Nine trained male mountaineers were investigated at sea level before (Pre-HA) and after a 20-day sojourn at altitudes of 4,000–7,000 m (Post-HA) in three states (Baseline, Hypercapnic Rebreathing, and Recovery). A principal component (PC) analysis was performed to evaluate the CRC. The number of mountaineers with one PC increased Post-HA (nine out of nine), compared to Pre-HA (five out of nine) [Chi-square (df = 1) = 5.14, P = 0.023]; the percentage of total variance explained by PC1 increased [Pre-HA median 65.6 (Q1 64.9/Q3 74.9), Post-HA 75.6 (73.3/77.9), P = 0.028]. Post-HA, the loadings of the expired fraction of O2, CO2, and ventilation onto PC1 did not change, and the loading of heart rate increased [Pre-HA 0.64 (0.45/0.68) and Post-HA 0.76 (0.65/0.82), P = 0.038]. During the Recovery, the percentage of total variance explained by PC1 was higher than during the Baseline. Post-HA, there was a high correlation between the Exercise addiction scores and the eigenvalues of PC1 (r = 0.9, P = 0.001). Thus, acute hypercapnic exposure reveals the Post-HA increase in cardiorespiratory coordination, which is highly related to the level of exercise addiction.
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Affiliation(s)
- Valentina V Gultyaeva
- Laboratory of Functional Reserves of Human Organism, Scientific Research Institute of Neurosciences and Medicine, Novosibirsk, Russia
| | - Dmitriy Y Uryumtsev
- Laboratory of Functional Reserves of Human Organism, Scientific Research Institute of Neurosciences and Medicine, Novosibirsk, Russia
| | - Margarita I Zinchenko
- Laboratory of Functional Reserves of Human Organism, Scientific Research Institute of Neurosciences and Medicine, Novosibirsk, Russia
| | - Vladimir N Melnikov
- Laboratory of Functional Reserves of Human Organism, Scientific Research Institute of Neurosciences and Medicine, Novosibirsk, Russia
| | - Natalia V Balioz
- Laboratory of Functional Reserves of Human Organism, Scientific Research Institute of Neurosciences and Medicine, Novosibirsk, Russia
| | - Sergey G Krivoschekov
- Laboratory of Functional Reserves of Human Organism, Scientific Research Institute of Neurosciences and Medicine, Novosibirsk, Russia
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10
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Sabino-Carvalho JL. The ventilatory and sympathetic responses to central and peripheral chemoreflex stimulation in disease states: the other side of the same coin. J Physiol 2019; 597:5045-5046. [PMID: 31430836 DOI: 10.1113/jp278458] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Jeann L Sabino-Carvalho
- NeuroV̇ASQ̇-Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasília, DF, Brazil
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11
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Abstract
The rebreathing of expire air, with high carbon dioxide and low oxygen concentrations, has long been implicated in unexplained Sudden Infant Death Syndrome (SIDS) when infants are placed to sleep in a prone (facedown) position. This study elucidates the effect of the aerodynamic parameters Reynolds number, Strouhal number, and Froude number on the percentage of expired air that is reinspired (rebreathed). A nasal module was designed that served as a simplified geometric representation of infant nostrils and placed above a hard, flat surface. Quantitative and flow visualization experiments were performed to measure rebreathing, using water as the working medium, under conditions of dynamic similarity. Different anatomic (e.g., tidal volume, nostril diameter), physiological (e.g., breathing frequency), and environmental (e.g., temperature, distance from the surface) factors were considered. Increases in Strouhal number (simultaneously faster and shallower breathing) always produced higher rebreathed percentages, because rolled-up vortices in the vicinity of the nostrils had less time to move away by self-induction. Positively and negatively buoyant flows resulted in significant rebreathing. In the latter case, consistent with a warm environment and a high percentage of rebreathed CO2, denser gas pooled in the vicinity of the nostrils. Reynolds numbers below 200 also dramatically increased rebreathing because the expired gas pooled much closer to the nostrils. These results clearly elucidated how the prone position dramatically increases rebreathing by a number of different mechanisms. Furthermore, the results offer plausible explanations of why a high-temperature environment and low birthweight are SIDS risk factors. NEW & NOTEWORTHY A fundamentally new aerodynamics-based approach to the study of rebreathing of expired air in infants is presented. Rebreathing is implicated in unexplained Sudden Infant Death Syndrome (SIDS) when infants sleep in a prone position. This is the first time that aerodynamic parameters are systematically varied and their effects on rebreathing quantified. The study provides us with a deeper understanding of the effects of breathing frequency, tidal volume (birthweight) and environmental conditions.
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Affiliation(s)
- Nadav Itzhak
- Faculty of Mechanical Engineering, Technion-Israel Institute of Technology, Technion City , Haifa , Israel
| | - David Greenblatt
- Faculty of Mechanical Engineering, Technion-Israel Institute of Technology, Technion City , Haifa , Israel
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12
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Signori D, Bellani G, Calcinati S, Grassi A, Patroniti N, Foti G. Effect of Face Mask Design and Bias Flow on Rebreathing During Noninvasive Ventilation. Respir Care 2019; 64:793-800. [PMID: 30914487 DOI: 10.4187/respcare.06269] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Noninvasive ventilation (NIV) is used to treat respiratory failure because it reduces the risks of endotracheal intubation and postextubation respiratory failure. A wide range of different interfaces is available, but concerns exist about rebreathing. This study evaluated a total face mask with a 2-limb ventilation circuit and separate access for inflow and outflow gas, which was developed to reduce rebreathing. METHODS In a bench test, a standard total face mask (with a single connector to the ventilation circuit) and the modified total face mask were applied to a mannequin connected to an active breathing simulator. A known CO2 flow (V̇CO2 ) was delivered to the mannequin's trachea. We tested the following settings: CPAP with the mechanical PEEP valve set at 8 cm H2O (with 60 and 90 L/min continuous flow) and pressure support of 6 and 12 cm H2O (with 2 and 15 L/min bias flow). The settings were tested at simulated breathing frequencies of 15 and 30 breaths/min and with V̇CO2 of 200 and 300 mL/min. The active simulator generated a tidal volume of 500 mL. Airway pressure, air flow, CO2 concentration, and CO2 flow as the product of air flow and CO2 were recorded. RESULTS The mean volume of CO2 rebreathed and the minimum CO2 inspiratory concentration were significantly lower with the modified mask than with the standard mask. The 15 L/min bias flow significantly decreased rebreathing with the DiMax0 mask, whereas it had no effect with the traditional mask. CONCLUSIONS A face mask with a two-limb ventilation circuit and separate access for inflow and outflow gas reduces rebreathing during NIV. The addition of bias flow enhances this effect. Further studies are required to verify the clinical relevance.
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Affiliation(s)
- Davide Signori
- School of Medicine and Surgery, University of Milan-Bicocca, Monza, Italy
| | - Giacomo Bellani
- School of Medicine and Surgery, University of Milan-Bicocca, Monza, Italy. .,Department of Emergency and Intensive Care, San Gerardo Hospital, Monza, Italy
| | - Serena Calcinati
- Department of Emergency and Intensive Care, San Gerardo Hospital, Monza, Italy
| | - Alice Grassi
- School of Medicine and Surgery, University of Milan-Bicocca, Monza, Italy.,Department of Emergency and Intensive Care, San Gerardo Hospital, Monza, Italy
| | - Nicolò Patroniti
- Department of Surgical and Integrated Diagnostical Science, University of Genoa, San Martino Hospital, Genoa, Italy
| | - Giuseppe Foti
- School of Medicine and Surgery, University of Milan-Bicocca, Monza, Italy.,Department of Emergency and Intensive Care, San Gerardo Hospital, Monza, Italy
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13
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Maltese MR, Leshner M. Carbon dioxide rebreathing induced by crib bumpers and mesh liners using an infant manikin. BMJ Paediatr Open 2019; 3:e000374. [PMID: 31206068 PMCID: PMC6542454 DOI: 10.1136/bmjpo-2018-000374] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Revised: 01/15/2019] [Accepted: 01/21/2019] [Indexed: 12/05/2022] Open
Abstract
OBJECTIVES Quantify impaired respiration in currently marketed crib bumpers (CBs), mesh liners (MLs) and alternative products (ALTs) used to attenuate the interaction between the baby and the crib sides and elucidate the relationship between impaired respiration and permeability. METHODS We experimentally quantified carbon dioxide rebreathing (CO2RB) via an infant manikin and air permeability via previously published test protocols, in commercially available CBs, MLs and ALTs. RESULTS Differences in CO2RB in ML (median [m]=8.2%, 25th percentile [P25]=6.8, 75th percentile [P75]=8.6), ALT (m=10.5%, P25=9.8, P75=10.7) and CB (m=11.6%, P25=10.2, P75=14.3) were significant (p<0.0001). For comparison, manikin tests with a pacifier yielded CO2RB of 5.6%-5.9%, blanket draped over the face/torso yielded CO2RB of 7.7%-8.6% and stuffed animal in various positions yielded CO2RB from 6.1% to 16.1%. Differences in permeability between ML (m=529.5 cubic feet per minute [CFM], P25=460, P75=747.5), ALT (m=29.0 CFM, P25=27.7, P75=37.7) and CB (m=46.6 CFM, P25=30.1, P75=58.7) groups were significant (p<0.0001). CO2RB was poorly correlated with air permeability (max R2=0.36). In a subset of tests, CB CO2RB increased by 50%-80% with increasing penetration force, whereas the ML CO2RB was nominally unchanged. CONCLUSIONS Government agencies and standards organisations are presently considering regulation of bedding including CBs. As paediatricians are consulted in the development of such regulations, our findings that permeability by itself was a poor predictor of CO2RB should be considered.
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Affiliation(s)
- Matthew R Maltese
- Department of Anesthesiology and Critical Care, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
- Perelman School of Medicine, The University of Pennsylvania, Philadelphia, Pennsylvania, USA
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14
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Abstract
Background Impaired brain oxygen delivery can trigger and exacerbate migraine attacks. Normoxic hypercapnia increases brain oxygen delivery markedly by vasodilation of the cerebral vasculature, and hypercapnia has been shown to abort migraine attacks. Stable normoxic hypercapnia can be induced by a compact partial rebreathing device. This pilot study aimed to provide initial data on the device's efficacy and safety. Methods Using a double-blinded, randomized, cross-over study design, adult migraine-with-aura patients self-administered the partial rebreathing device or a sham device for 20 minutes at the onset of aura symptoms. Results Eleven participants (mean age 35.5, three men) self-treated 41 migraine attacks (20 with the partial rebreathing device, 21 with sham). The partial rebreathing device increased mean End Tidal CO2 by 24%, while retaining mean oxygen saturation above 97%. The primary end point (headache intensity difference between first aura symptoms and two hours after treatment (0-3 scale) - active/sham difference) did not reach statistical significance (-0.55 (95% CI: -1.13-0.04), p = 0.096), whereas the difference in percentage of attacks with pain relief at two hours was significant ( p = 0.043), as was user satisfaction ( p = 0.022). A marked efficacy increase was seen from first to second time use of the partial rebreathing device. No adverse events occurred, and side effects were absent or mild. Conclusion Normoxic hypercapnia shows promise as an adjunctive/alternative migraine treatment, meriting further investigation in a larger population. Clinical study registered at ClinicalTrials.gov with identifier NCT03472417.
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Affiliation(s)
| | - Troels Johansen
- 2 Aarhus University School of Engineering, Aarhus University, Aarhus, Denmark.,3 BalancAir, Kongens Lyngby, Denmark
| | - Kai Kaila
- 4 Molecular and Integrative Biosciences Research Program and HiLife, University of Helsinki, Helsinki, Finland
| | - Helge Kasch
- 5 Spinal Cord Injury Center of Western Denmark, Department of Neurology, Regional Hospital of Viborg, Viborg, Denmark
| | - Flemming W Bach
- 1 Department of Neurology, Aarhus University Hospital, Aarhus, Denmark
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15
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Abstract
Any technique that employs a fresh gas flow that is less than the alveolar ventilation can be classified as low-flow anaesthesia. The complexities involved in the calculation of uptake of anaesthetic agents during the closed-circuit anaesthesia made this technique less popular. However, the awareness of the dangers of theatre pollution with trace amounts of the anaesthetic agents and the prohibitively high cost of the new inhalational agents, have helped in the rediscovery of low-flow anaesthesia. Moreover, the time has arrived for each of us, the practicing anaesthesiologists, to move towards the practice of low-flow anaesthesia, to achieve lesser theatre and environmental pollution and also to make anaesthesia more economical. The article also reviews low-flow anaesthesia (LFA) in paediatrics, recent advances such as automated LFA and updates on currently undergoing research to retrieve and reuse anaesthetic agents.
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Affiliation(s)
- Madhusudan Upadya
- Department of Anaesthesiology, Kasturba Medical College, Manipal University, Mangalore, Karnataka, India
| | - P J Saneesh
- Department of Anesthesia, Sultan Qaboos University Hospital, Muscat, Sultanate of Oman
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16
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Möller W, Feng S, Domanski U, Franke KJ, Celik G, Bartenstein P, Becker S, Meyer G, Schmid O, Eickelberg O, Tatkov S, Nilius G. Nasal high flow reduces dead space. J Appl Physiol (1985) 2017; 122:191-197. [PMID: 27856714 PMCID: PMC5283847 DOI: 10.1152/japplphysiol.00584.2016] [Citation(s) in RCA: 139] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Revised: 11/11/2016] [Accepted: 11/11/2016] [Indexed: 11/22/2022] Open
Abstract
Recent studies show that nasal high flow (NHF) therapy can support ventilation in patients with acute or chronic respiratory disorders. Clearance of dead space has been suggested as being the key mechanism of respiratory support with NHF therapy. The hypothesis of this study was that NHF in a dose-dependent manner can clear dead space of the upper airways from expired air and decrease rebreathing. The randomized crossover study involved 10 volunteers using scintigraphy with 81mKrypton (81mKr) gas during a breath-holding maneuver with closed mouth and in 3 nasally breathing tracheotomized patients by volumetric capnography and oximetry through sampling CO2 and O2 in the trachea and measuring the inspired volume with inductance plethysmography following NHF rates of 15, 30, and 45 l/min. The scintigraphy revealed a decrease in 81mKr gas clearance half-time with an increase of NHF in the nasal cavities [Pearson's correlation coefficient cc = -0.55, P < 0.01], the pharynx (cc = -0.41, P < 0.01), and the trachea (cc = -0.51, P < 0.01). Clearance rates in nasal cavities derived from time constants and MRI-measured volumes were 40.6 ± 12.3 (SD), 52.5 ± 17.7, and 72.9 ± 21.3 ml/s during NHF (15, 30, and 45 l/min, respectively). Measurement of inspired gases in the trachea showed an NHF-dependent decrease of inspired CO2 that correlated with an increase of inspired O2 (cc = -0.77, P < 0.05). NHF clears the upper airways of expired air, which reduces dead space by a decrease of rebreathing making ventilation more efficient. The dead space clearance is flow and time dependent, and it may extend below the soft palate. NEW & NOTEWORTHY Clearance of expired air in upper airways by nasal high flow (NHF) can be extended below the soft palate and de facto causes a reduction of dead space. Using scintigraphy, the authors found a relationship between NHF, time, and clearance. Direct measurement of CO2 and O2 in the trachea confirmed a reduction of rebreathing, providing the actual data on inspired gases, and this can be used for the assessment of other forms of respiratory support.
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Affiliation(s)
- Winfried Möller
- Comprehensive Pneumology Center, German Center for Lung Research, Munich, Germany;
- Institute of Lung Biology and Disease, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Germany
| | - Sheng Feng
- Fisher & Paykel Healthcare, Auckland, New Zealand
| | - Ulrike Domanski
- HELIOS Klinik Hagen-Ambrock, Witten-Herdecke University, Hagen, Germany
| | - Karl-Josef Franke
- HELIOS Klinik Hagen-Ambrock, Witten-Herdecke University, Hagen, Germany
| | - Gülnaz Celik
- Comprehensive Pneumology Center, German Center for Lung Research, Munich, Germany
- Institute of Lung Biology and Disease, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Germany
| | - Peter Bartenstein
- Department of Nuclear Medicine, LMU Medical Center Grosshadern, Munich, Germany
| | - Sven Becker
- Department of Otolaryngology, Head and Neck Surgery, LMU Medical Center Grosshadern, Munich, Germany
| | - Gabriele Meyer
- Department of Nuclear Medicine, Asklepios Fachkliniken München-Gauting, Gauting, Germany; and
| | - Otmar Schmid
- Comprehensive Pneumology Center, German Center for Lung Research, Munich, Germany
- Institute of Lung Biology and Disease, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Germany
| | - Oliver Eickelberg
- Comprehensive Pneumology Center, German Center for Lung Research, Munich, Germany
- Institute of Lung Biology and Disease, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Germany
- University Hospital of the Ludwig Maximilian University, Munich, Germany
| | | | - Georg Nilius
- HELIOS Klinik Hagen-Ambrock, Witten-Herdecke University, Hagen, Germany
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17
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Theerapongpakdee S, Sathitkarnmanee T, Tribuddharat S, Sucher S, Thananun M, Nonlhaopol D. Comparative study of minimal fresh gas flow used in Lack-Plus and Lack's circuit in spontaneously breathing anesthetized adults. Med Devices (Auckl) 2016; 9:395-399. [PMID: 27877068 PMCID: PMC5108601 DOI: 10.2147/mder.s118722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND The Lack's circuit is a co-axial Mapleson A breathing system commonly used in spontaneously breathing anesthetized adults but still requires high fresh gas flow (FGF). The Lack-Plus circuit was invented with the advantage of lower FGF requirement. The authors compared the Lack-Plus and Lack's circuit for the minimal FGF requirement with no rebreathing in spontaneously breathing anesthetized adults. METHODS This was a randomized crossover study. We enrolled 24 adult patients undergoing supine elective surgery, with a body mass index ≤30 kg/m2 and an American Society of Anesthesiologists physical status I-II. They were randomly allocated to group 1 (LP-L) starting with Lack-Plus then switching to Lack's circuit or group 2 (L-LP) (with the reverse pattern). After induction and intubation, anesthesia was maintained with 50% N2O/O2 and desflurane (4%-6%) plus fentanyl titration to maintain an optimal respiratory rate between 10 and 16/min. Starting with the first circuit, all the patients were spontaneously breathing with a FGF of 4 L/min for 10 min, gradually decreased by 0.5 L/min every 5 min until FGF was 2.5 L/min. End-tidal CO2, inspired minimum CO2 (ImCO2), mean arterial pressure, and oxygen saturation were recorded until rebreathing (ImCO2 >0 mmHg) occurred. The alternate anesthesia breathing circuit was used and the measurements were repeated. RESULTS The respective minimal FGF at the point of rebreathing for the Lack-Plus and Lack's circuit was 2.7±0.8 and 3.3±0.5 L/min, respectively, p<0.001. At an FGF of 2.5 L/min, the respective ImCO2 was 1.5±2.0 and 4.2±2.6 mmHg, respectively, p<0.001. CONCLUSION The Lack-Plus circuit can be used safely and effectively, and it requires less FGF than Lack's circuit in spontaneously breathing anesthetized adults.
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Affiliation(s)
| | | | - Sirirat Tribuddharat
- Department of Anesthesiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
| | - Siwalai Sucher
- Department of Anesthesiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
| | - Maneerat Thananun
- Department of Anesthesiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
| | - Duangthida Nonlhaopol
- Department of Anesthesiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
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18
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Harvey D, Pollock NW, Gant N, Hart J, Mesley P, Mitchell SJ. The duration of two carbon dioxide absorbents in a closed-circuit rebreather diving system. Diving Hyperb Med 2016; 46:92-97. [PMID: 27334997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2016] [Accepted: 05/05/2016] [Indexed: 06/06/2023]
Abstract
INTRODUCTION Diving rebreathers use canisters containing sodalime preparations to remove carbon dioxide (CO₂) from the expired gas. These preparations have a limited absorptive capacity and therefore may limit dive duration. The Inspiration™ rebreather is designed for use with Sofnolime 797™ but some divers use Spherasorb™ as an alternative. There are no published data comparing the CO2-absorbing efficacy of these sodalime preparations in an Inspiration rebreather. METHODS An Inspiration rebreather was operated in a benchtop circuit under conditions simulating work at 6 metabolic equivalents (MET). Ventilation was maintained at 45 L·min⁻¹ (tidal volume 1·5 L; respiratory rate 30 min⁻¹) with CO₂ introduced to the expiratory limb at 2·L·min⁻¹. The PiCO₂ was continuously monitored in the inspiratory limb. The rebreather canister was packed to full volume with either Sofnolime or Spherasorb and 10 trials were conducted (five using each absorbent), in which the circuit was continuously run until the PiCO₂ reached 1 kPa ('breakthrough'). Peak inspiratory and expiratory pressures during tidal ventilation of the circuit were also recorded. RESULTS The mean operating duration to CO₂ breakthrough was 138 ± 4 (SD) minutes for 2.38·kg Spherasorb and 202 ± minutes for 2.64·kg Sofnolime (P < 0.0001). The difference between peak inspiratory and expiratory pressures was 10% less during use of Spherasorb, suggesting lower work of breathing. CONCLUSIONS Under conditions simulating work at 6 MET during use of an Inspiration rebreather a canister packed with Spherasorb reached CO₂ breakthrough 32% earlier with 10% less mass than Sofnolime packed to similar volume. Divers cannot alternate between these two preparations and expect the same endurance.
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Affiliation(s)
- David Harvey
- Department of Anaesthesia, Auckland City Hospital, New Zealand
| | - Neal W Pollock
- Divers Alert Network, Durham, NC, USA
- Department of Anaesthesiology, School of Medicine, University of Auckland, Private Bag 92019, Auckland New Zealand,
| | - Nicholas Gant
- Exercise Neurometabolism Laboratory, Department of Exercise Sciences, University of Auckland, Auckland, New Zealand
| | - Jason Hart
- Exercise Neurometabolism Laboratory, Department of Exercise Sciences, University of Auckland, Auckland, New Zealand
| | | | - Simon J Mitchell
- Department of Anaesthesia, Auckland City Hospital, New Zealand
- Department of Anaesthesiology, School of Medicine, University of Auckland, Private Bag 92019, Auckland, New Zealand, Phone: +64-(0)2-7414-1212, E-mail:
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19
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Deng C, Pollock NW, Gant N, Hannam JA, Dooley A, Mesley P, Mitchell SJ. The five-minute prebreathe in evaluating carbon dioxide absorption in a closed-circuit rebreather: a randomized single-blind study. Diving Hyperb Med 2015; 45:16-24. [PMID: 25964034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Accepted: 01/14/2015] [Indexed: 06/04/2023]
Abstract
INTRODUCTION Closed-circuit underwater rebreather apparatus (CCR) recycles expired gas through a carbon dioxide (CO₂) 'scrubber'. Prior to diving, users perform a five-minute 'prebreathe' during which they self-check for symptoms of hypercapnia that might indicate a failure in the scrubber. There is doubt that this strategy is valid. METHODS Thirty divers were block-randomized to breathe for five minutes on a circuit in two of the following three conditions: normal scrubber, partly-failed scrubber, and absent scrubber. Subjects were blind to trial allocation and instructed to terminate the prebreathe on suspicion of hypercapnia. RESULTS Early termination was seen in 0/20, 2/20, and 15/20 of the normal, partly-failed, and absent absorber conditions, respectively. Subjects in the absent group experienced a steady, uncontrolled rise in inspired (PICO₂) and end-tidal CO₂ (PETCO₂). Seven subjects exhibited little or no increase in minute volume yet reported dyspnoea at termination, suggesting a biochemically-mediated stimulus to terminate. This was consistent with results in the partly-failed condition (which resulted in a plateaued mean PICO₂ near 20 mmHg), where a small increase in ventilation typically compensated for the inspired CO₂ increase. Consequently, mean PETCO₂ did not change and in the absence of a hypercapnic biochemical stimulus, subjects were very insensitive to this condition. CONCLUSIONS While prebreathes are useful to evaluate other primary functions, the five-minute prebreathe is insensitive for CO₂ scrubber faults in a rebreather. Partly-failed conditions are dangerous because most will not be detected at the surface, even though they may become very important at depth.
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Affiliation(s)
- Carolyn Deng
- Department of Anaesthesiology, University of Auckland
| | - Neal W Pollock
- Center for Hyperbaric Medicine and Environmental Physiology, Duke University Medical Center, Divers Alert Network, Durham, NC, USA
| | - Nicholas Gant
- Department of Sport and Exercise Science, University of Auckland
| | | | | | | | - Simon J Mitchell
- Department of Anaesthesia, Auckland City Hospital, Head of Department, Department of Anaesthesiology University of Auckland, Private Bag 92019, Auckland, New Zealand, Phone: +64-(0)9-923-2569, E-mail:
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20
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Abstract
The purpose of this study was to evaluate whether greater and sustainable stroke volume (SV) responses may be obtained by exercise intensities corresponding to peak SV (SVpeak) vs. maximal O2 consumption (VO2max), and short vs. long intervals (SI vs. LI). Nine moderate- to well-trained male athletes competing at regional level specialists of cyclist, track and field volunteered to take part in the study (VO2max: 59.7 ± 7.4 mL·min(-1)·kg(-1)). Following familiarisation sessions, VO2max was determined, and then SVpeak was evaluated using exercise intensities at 40%-100% of VO2max by nitrous-oxide rebreathing (N2ORB) method. Then each separate participant exercised wattages corresponding to individual VO2max and SVpeak during both SI (SIVO2max and SI(SVpeak)) and LI (LIVO2max and LI(SVpeak)) workouts on a cycle ergometer. Main results showed that both SIVO2max and SI(SVpeak) yielded greater SV responses than LIVO2max and LI(SVpeak) (p ≤ 0.05). Mean SV responses were greater in LI(SVpeak) than in LIVO2max (p ≤ 0.05), but there was no statistical difference between SI(SVpeak) and SIVO2max. However, there was significantly less physiological stress based on VO2, respiratory exchange ratio, heart rate and rate of perceived exhaustion in SVpeak than in [Formula: see text] intensities (p ≤ 0.05). Moreover, SV responses at exercise phases increased in the early stages and remain stable until the end of SIVO2max and SI(SVpeak) workouts (p > 0.05), while they were gradually decreasing in LIVO2max and LI(SVpeak) sessions (p ≤ 0.05). In conclusion, if the aim of a training session is to improve SVpeak with less physiological stress, SI(SVpeak) seems a better alternative than other modalities tested in the present study.
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Affiliation(s)
- Muzaffer Colakoglu
- a School of Physical Education and Sports, Coaching Education Department , Ege University , Izmir , Turkey
| | - Ozgur Ozkaya
- a School of Physical Education and Sports, Coaching Education Department , Ege University , Izmir , Turkey
| | - Gorkem Aybars Balci
- a School of Physical Education and Sports, Coaching Education Department , Ege University , Izmir , Turkey
| | - Bulent Yapicioglu
- a School of Physical Education and Sports, Coaching Education Department , Ege University , Izmir , Turkey
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Sturesson LW, Bodelsson M, Jonson B, Malmkvist G. Anaesthetic conserving device AnaConDa: dead space effect and significance for lung protective ventilation. Br J Anaesth 2014; 113:508-14. [PMID: 24871871 DOI: 10.1093/bja/aeu102] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND The anaesthetic conserving device AnaConDa (ACD) reflects exhaled anaesthetic agents thereby facilitating the use of inhaled anaesthetic agents outside operating theatres. Expired CO₂ is, however, also reflected causing a dead space effect in excess of the ACD internal volume. CO₂ reflection from the ACD is attenuated by humidity. This study tests the hypothesis that sevoflurane further attenuates reflection of CO₂. An analysis of clinical implications of our findings was performed. METHODS Twelve postoperative patients received mechanical ventilation using a conventional heat and moisture exchanger (HME, internal volume 50 ml) and an ACD (100 ml), the latter with or without administration of sevoflurane. The ACD was also studied with a test lung at high sevoflurane concentrations. Reflection of CO₂ and dead space effects were evaluated with the single-breath test for CO2. RESULTS Sevoflurane reduced but did not abolish CO₂ reflection. In patients, the mean dead space effect with 0.8% sevoflurane was 88 ml larger using the ACD compared with the HME (P<0.001), of which 38 ml was due to CO₂ reflection. Our calculations show that with the use of the ACD, normocapnia cannot be achieved with tidal volume <6 ml kg(-1) even when respiratory rate is increased. CONCLUSIONS An ACD causes a dead space effect larger than its internal volume due to reflection of CO₂, which is attenuated but not abolished by sevoflurane administration. CO₂ reflection from the ACD limits its use with low tidal volume ventilation, such as with lung protection ventilation strategies. CLINICAL TRIAL REGISTRATION Clinical Trials NCT01699802.
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Affiliation(s)
- L W Sturesson
- Section of Anaesthesiology and Intensive Care, Lund University and Skane University Hospital, SE-221 85 Lund, Sweden
| | - M Bodelsson
- Section of Anaesthesiology and Intensive Care, Lund University and Skane University Hospital, SE-221 85 Lund, Sweden
| | - B Jonson
- Section of Clinical Physiology, Department of Clinical Sciences Lund, Lund University and Skane University Hospital, SE-221 85 Lund, Sweden
| | - G Malmkvist
- Section of Anaesthesiology and Intensive Care, Lund University and Skane University Hospital, SE-221 85 Lund, Sweden
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Fan JL, Subudhi AW, Evero O, Bourdillon N, Kayser B, Lovering AT, Roach RC. AltitudeOmics: enhanced cerebrovascular reactivity and ventilatory response to CO2 with high-altitude acclimatization and reexposure. J Appl Physiol (1985) 2013; 116:911-8. [PMID: 24356520 DOI: 10.1152/japplphysiol.00704.2013] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The present study is the first to examine the effect of high-altitude acclimatization and reexposure on the responses of cerebral blood flow and ventilation to CO2. We also compared the steady-state estimates of these parameters during acclimatization with the modified rebreathing method. We assessed changes in steady-state responses of middle cerebral artery velocity (MCAv), cerebrovascular conductance index (CVCi), and ventilation (V(E)) to varied levels of CO2 in 21 lowlanders (9 women; 21 ± 1 years of age) at sea level (SL), during initial exposure to 5,260 m (ALT1), after 16 days of acclimatization (ALT16), and upon reexposure to altitude following either 7 (POST7) or 21 days (POST21) at low altitude (1,525 m). In the nonacclimatized state (ALT1), MCAv and V(E) responses to CO2 were elevated compared with those at SL (by 79 ± 75% and 14.8 ± 12.3 l/min, respectively; P = 0.004 and P = 0.011). Acclimatization at ALT16 further elevated both MCAv and Ve responses to CO2 compared with ALT1 (by 89 ± 70% and 48.3 ± 32.0 l/min, respectively; P < 0.001). The acclimatization gained for V(E) responses to CO2 at ALT16 was retained by 38% upon reexposure to altitude at POST7 (P = 0.004 vs. ALT1), whereas no retention was observed for the MCAv responses (P > 0.05). We found good agreement between steady-state and modified rebreathing estimates of MCAv and V(E) responses to CO2 across all three time points (P < 0.001, pooled data). Regardless of the method of assessment, altitude acclimatization elevates both the cerebrovascular and ventilatory responsiveness to CO2. Our data further demonstrate that this enhanced ventilatory CO2 response is partly retained after 7 days at low altitude.
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Affiliation(s)
- Jui-Lin Fan
- Institute of Sports Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
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Canova D, Roatta S, Micieli G, Bosone D. Cerebral oxygenation and haemodynamic effects induced by nimodipine in healthy subjects. Funct Neurol 2012; 27:169-176. [PMID: 23402678 PMCID: PMC3812769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The cerebrovascular effects of nimodipine are still poorly understood even in the healthy condition; in particular, its effects on tissue oxygenation have never been investigated. The aim of the present study was to investigate changes in cerebral oxygenation and blood volume upon oral administration of nimodipine (90 mg) in the healthy condition. In eight subjects, changes in cerebral tissue oxygenation and blood volume were determined simultaneously with changes in blood velocity of the middle cerebral artery (VMCA) by using, respectively, near infrared spectroscopy (NIRS) and transcranial Doppler ultrasonography (TCD). The subjects also underwent noninvasive assessment of arterial blood pressure (ABP) and end-tidal CO2. TCD and NIRS CO2 reactivity indices were al-so extracted. Nimodipine significantly reduced ABP (11±13%) and increased heart rate, as well as NIRS oxygenation(6.0±4.8%) and blood volume indices (9.4±10.1%), while V(MCA) was not significantly decreased (2.0±3.5%). Nimodipine slightly but significantly reduced the V(MCA) response to changes in pCO2 whereas the CO2 reactivity of NIRS parameters was improved. The observed changes in cerebral tissue oxygenation and blood volume indicate nimodipine-induced cerebrovascular dilation and increased perfusion, while the effect on V(MCA)possibly results from dilation of the insonated artery. The present results cast doubt on the putative nimodipine-induced impairment of CO2 reactivity.
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Affiliation(s)
- Daniela Canova
- Neurovascular Laboratory, C. Mondino National Institute of Neurology, IRCCS, Pavia, Italy.
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