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dc.contributor.authorHoiland, Ryan
dc.contributor.authorAinslie, Philip
dc.contributor.authorBain, Anthony
dc.contributor.authorMacLeod, David
dc.contributor.authorStembridge, Mike
dc.contributor.authorDrvis, Ivan
dc.contributor.authorMadden, Dennis
dc.contributor.authorBarak, Otto
dc.contributor.authorMacLeod, Doug
dc.contributor.authorDujic, Zeljko
dc.date.accessioned2016-05-05T09:20:23Z
dc.date.available2016-05-05T09:20:23Z
dc.date.issued2017-04-01
dc.identifier.citationHoiland, R., Ainslie, P., Bain, A., Macleod, David, Stembridge, M., Drvis, I., Madden, D., Barak, O., Macleod, Doug & Dujic, Z. (2016) 'Beta 1-blockade increases maximal apnea duration in elite breath hold divers', Journal of Applied Physiology, 122 (4), pp. 899-906en_US
dc.identifier.issn8750-7587
dc.identifier.urihttp://hdl.handle.net/10369/7876
dc.descriptionThis article was published in Journal of Applied Physiology on 28 April 2016 (online), available at http://dx.doi.org/10.1152/japplphysiol.00127.2016en_US
dc.description.abstractWe hypothesized that the cardioselective β1-adrenoreceptor antagonist esmolol would improve maximal apnea duration in elite breath hold divers. In elite national level divers (n=9), maximal apneas were performed in a randomized and counterbalanced order while receiving either i.v. esmolol (150μg ⋅ kg-1 ⋅ min-1) or volume matched saline (placebo). During apnea, heart rate (ECG), beat-by-beat blood pressure, stroke volume (SV), cardiac output (CO) and total peripheral resistance (TPR) were measured (finger photoplethysmography). Myocardial oxygen consumption (MVO2) was estimated from rate pressure product. Cerebral blood flow through the internal carotid (ICA) and vertebral arteries (VA) was assessed using Duplex ultrasound. Apnea duration improved in the esmolol trial when compared to placebo (356±57 vs. 323±61 seconds; P<0.01) despite similar end apnea peripheral oxyhemoglobin saturation (71.8±10.3% vs. 74.9±9.5; P=0.10). The HR response to apnea was reduced by esmolol at 10-30% of apnea duration, while MAP was unaffected. Esmolol reduced SV (main effect; P<0.05) and CO (main effect; P<0.05), and increased TPR (main effect; P<0.05) throughout apnea. Esmolol also reduced MVO2 throughout apnea (main effect; P<0.05). Cerebral blood flow through the ICA and VA were unchanged by esmolol at baseline and the last 30 seconds of apnea; however, global cerebral blood flow was reduced in the esmolol trial at end apnea (P<0.05). Our findings demonstrate that, in elite breath hold divers, apnea breakpoint is improved by β1-blockade, likely owing to an improved total body oxygen sparring through increased centralization of blood volume (↑TPR) and reduced MVO2.en_US
dc.description.sponsorshipThis study was funded through a Canadian Research Chair and NSERC Discovery grant held by Prof Ainslie. Drs. Dujic, Barak, and Ainslie were also funded through the Croatian Science Foundation (grant no. IP-2014-09-1937). We would like to specially acknowledge the apnea divers from the Croatia National Apnea team for their participation.en_US
dc.language.isoenen_US
dc.publisherAmerican Physiological Societyen_US
dc.relation.ispartofseriesJournal of Applied Physiology
dc.subjectesmololen_US
dc.subjectrate pressure producten_US
dc.subjectbreath hold divingen_US
dc.subjectcerebral blood flowen_US
dc.titleBeta 1-blockade increases maximal apnea duration in elite breath hold diversen_US
dc.typeArticleen_US
dc.identifier.doihttp://dx.doi.org/10.1152/japplphysiol.00127.2016
dc.date.dateAccepted2016-04-26
dc.rights.embargodate2017-04-28
dc.rights.embargoreason12 month embargo requested by publisher
dcterms.dateAccepted2016-04-26
rioxxterms.licenseref.urihttp://www.rioxx.net/licenses/all-rights-reserved
rioxxterms.freetoread.startdate2017-04-28


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