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Shashikant L Sholapurkar
The survival of cardiotocography (CTG) as a tool for intrapartum fetal monitoring seems threatened somewhat unjustifiably and unwittingly despite the absence of better alternatives. Fetal heart rate (FHR) decelerations are center-stage (most important) in the interpretation of CTG with maximum impact on three-tier classification. The pattern-discrimination of FHR decelerations is inexorably linked to their nomenclature. Unscientific or flawed nomenclature of decelerations can explain the dysfunctional CTG interpretation leading to errors in detection of acidemic fetuses...
April 2018: Journal of Clinical Medicine Research
Tadayoshi Miyamoto, Kou Manabe, Shinya Ueda, Hidehiro Nakahara
NEW FINDINGS: What is the central question of this study? The lack of useful small animal models for studying exercise hyperpnoea makes it difficult to investigate the underlying mechanisms of exercise-induced ventilatory abnormalities in various disease states. What is the main finding and its importance? We developed an anesthetized rat model for studying exercise hyperpnoea, using respiratory equilibrium diagram for quantitative characterization of the respiratory chemoreflex feedback system...
March 6, 2018: Experimental Physiology
Alexandre F Cunha, Igor S A Felippe, Nilson C Ferreira-Junior, Leonardo B M Resstel, Daniela A M Guimarães, Vanessa Beijamini, Julian F R Paton, Karla N Sampaio
Although it is well-established that severe poisoning by organophosphorus (OP) compounds strongly affects the cardiorespiratory system, the effects of sub-lethal exposure to these compounds on the neural control of cardiovascular function are poorly explored. The aim of this study was to evaluate the effects of acute sub-lethal exposure to chlorpyrifos (CPF), a commonly used OP insecticide, on three basic reflex mechanisms involved in blood pressure regulation, the peripheral chemoreflex, the baroreflex and the Bezold-Jarisch reflex...
February 19, 2018: Toxicology
Nanduri R Prabhakar, Ying-Jie Peng, Guoxiang Yuan, Jayasri Nanduri
Sleep apnea is a prevalent respiratory disease characterized by periodic cessation of breathing during sleep causing intermittent hypoxia (IH). Sleep apnea patients and rodents exposed to IH exhibit elevated sympathetic nerve activity and hypertension. A heightened carotid body (CB) chemoreflex has been implicated in causing autonomic abnormalities in IH-treated rodents and in sleep apnea patients. The purpose of this article is to review the emerging evidence showing that interactions between reactive oxygen species (ROS) and gaseous transmitters as a mechanism cause hyperactive CB by IH...
February 22, 2018: Cell and Tissue Research
Igor A Fernandes, Marcos P Rocha, Monique O Campos, João D Mattos, Daniel E Mansur, Helena N M Rocha, Paulo A C Terra, Vinícius P Garcia, Natália G Rocha, Niels H Secher, Antonio C L Nóbrega
KEY POINTS: Hypoxaemia evokes a repertoire of homeostatic adjustments that maintain oxygen supply to organs and tissues including the brain and skeletal muscles. Because hypertensive patients have impaired endothelial-dependent vasodilatation and an increased sympathetic response to arterial oxygen desaturation, we investigated whether hypertension impairs isocapnic hypoxia-induced cerebral and skeletal muscle hyperaemia to an extent that limits oxygen supply. In middle-aged hypertensive men, vertebral and femoral artery blood flow do not increase in response to isocapnic hypoxia, limiting brain and peripheral hyperaemia and oxygen supply...
February 20, 2018: Journal of Physiology
Stanisław Zajączkowski, Wiesław Ziółkowski, Piotr Badtke, Miłosz A Zajączkowski, Damian J Flis, Adam Figarski, Maria Smolińska-Bylańska, Tomasz H Wierzba
BACKGROUND: It has long been suggested that reactive oxygen species (ROS) play a role in oxygen sensing via peripheral chemoreceptors, which would imply their involvement in chemoreflex activation and autonomic regulation of heart rate. We hypothesize that antioxidant affect neurogenic cardiovascular regulation through activation of chemoreflex which results in increased control of sympathetic mechanism regulating heart rhythm. Activity of xanthine oxidase (XO), which is among the major endogenous sources of ROS in the rat has been shown to increase during hypoxia promote oxidative stress...
2018: PloS One
Stephen A Busch, Hannah E Davies, Sean Van Diepen, Lydia L Simpson, Frances Sobierajski, Laurel Riske, Mike Stembridge, Philip N Ainslie, Christopher K Willie, Ryan L Hoiland, Jonathan P Moore, Craig D Steinback
Peripheral chemoreflex mediated increases in both parasympathetic and sympathetic drive under chronic hypoxia may evoke brady-arrhythmias during apneic periods. We determined if: a) voluntary apnea unmasks arrhythmia at sea level and altitude (5050m), b) if high altitude natives (Nepalese Sherpa) exhibit similar cardiovagal responses at altitude; and c) if brady-arrhythmias at altitude are partially chemoreflex mediated. Participants were grouped as Lowlanders (n=14; age=27{plus minus}6yrs) and Nepalese Sherpa (n=8; age=32{plus minus}11yrs)...
December 21, 2017: Journal of Applied Physiology
Megan Bardgett Blackburn, Mary Ann Andrade, Glenn M Toney
Acute intermittent hypoxia (AIH) repetitively activates the arterial chemoreflex and triggers a progressive increase of sympathetic nerve activity (SNA) and phrenic nerve activity (PNA) referred to as sympathetic and phrenic long-term facilitation (S-LTF and P-LTF), respectively. Neurons of the hypothalamic paraventricular nucleus (PVN) participate in the arterial chemoreflex, but their contribution to AIH-induced LTF is unknown. To determine this, anesthetized rats were vagotomized and exposed to 10 cycles of AIH, each consisting of ventilation for 3 minutes with 100% O2 followed by 3 minutes with 15% O2...
December 21, 2017: Journal of Applied Physiology
Christopher Hazlett, Heather Edgell
Orthostatic intolerance is more common in women than men, and some studies have found that women in the early follicular (EF) phase of the menstrual cycle experience the greatest feelings of lightheadedness. Chemoreflex function while supine or upright was investigated to determine the potential contribution of ventilatory control to these phenomena. Men (n = 13) and women (n = 14) were tested while supine and 70° upright (head-up tilt [HUT]) and given: (1) normoxia or (2) hypercapnia (5% CO2 ). Women were tested during the EF phase (days 2-5) and the midluteal phase (ML; days 18-24)...
January 2018: Physiological Reports
David Wang, Keith K Wong, Luke Rowsell, Garrick W Don, Brendon J Yee, Ronald R Grunstein
There is no satisfactory treatment for obstructive sleep apnoea (OSA). Supplemental low-flow oxygen therapy (LFO2) has been shown to reduce hypoxaemia and is well tolerated by patients with OSA. However, oxygen therapy may be beneficial only to certain subsets of patients with OSA. In this study, we evaluated a 10-min awake ventilatory chemoreflex test in predicting individual OSA response to 2 months of LFO2 therapy.At baseline, patients with OSA underwent ventilatory chemoreflex testing in the afternoon, prior to the overnight polysomnography...
January 2018: European Respiratory Journal: Official Journal of the European Society for Clinical Respiratory Physiology
Wioletta Pijacka, Pedro L Katayama, Helio C Salgado, Gisele S Lincevicius, Ruy R Campos, Fiona D McBryde, Julian F R Paton
The carotid body has recently emerged as a promising therapeutic target for treating cardiovascular disease, however the potential impact of carotid bodies removal on the dynamic cardiovascular responses to acute stressors such as exercise, hypoxia and hypercapnia in hypertension is an important safety consideration that has not been studied. We first validated a novel surgical approach to selectively resect the carotid bodies bilaterally (CBR) sparing the carotid sinus baroreflex. Second, we evaluated the impact of CBR on the cardiovascular responses to exercise, hypoxia and hypercapnia in the conscious, chronically instrumented spontaneously hypertensive (SH) rats...
January 5, 2018: Journal of Physiology
Cécile Baldy, Simon Chamberland, Stéphanie Fournier, Richard Kinkead
The presence of liquid near the larynx of immature mammals triggers prolonged apneas with significant O2 desaturations and bradycardias. When excessive, this reflex (the laryngeal chemoreflex; LCR) can be fatal. Our understanding of the origins of abnormal LCR are limited; however, perinatal stress and male sex are risk factors for cardio-respiratory failure in infants. Because exposure to stress during early life has deleterious and sex-specific consequences on brain development it is plausible that respiratory reflexes are vulnerable to neuroendocrine dysfunction...
November 2017: ENeuro
Marc A Russo, Danielle M Santarelli, Dean O'Rourke
Slow breathing practices have been adopted in the modern world across the globe due to their claimed health benefits. This has piqued the interest of researchers and clinicians who have initiated investigations into the physiological (and psychological) effects of slow breathing techniques and attempted to uncover the underlying mechanisms. The aim of this article is to provide a comprehensive overview of normal respiratory physiology and the documented physiological effects of slow breathing techniques according to research in healthy humans...
December 2017: Breathe
David Cristobal Andrade, Alexis Arce-Alvarez, Camilo Toledo, Hugo S Diaz, Claudia Lucero, Rodrigo Quintanilla, Harold D Schultz, Noah J Marcus, Markus Amman, Rodrigo Del Rio
Heart failure (HF) is a global public health problem that, independent of its etiology (reduced (HFrEF) or preserved ejection fraction (HFpEF)), is characterized by functional impairments of cardiac function, chemoreflex hypersensitivity, baroreflex sensitivity (BRS) impairment, and abnormal autonomic regulation, all of which contribute to increased morbidity and mortality. Exercise training (ExT) has been identified as a nonpharmacological therapy capable of restoring normal autonomic function and improving survival in patients with HFrEF...
November 22, 2017: American Journal of Physiology. Heart and Circulatory Physiology
Ivan M Lang, Bidyut K Medda, Reza Shaker, Sudarshan Jadcherla
BackgroundIt has been hypothesized that life-threatening events are caused by supraesophageal reflux (SER) of gastric contents that activates laryngeal chemoreflex-stimulated apnea. Placing infants supine decreases the risk of sudden infant death syndrome (SIDS). The aim of this study was to determine whether body position affects esophageal reflexes that control SER.MethodsWe instrumented the pharyngeal and esophageal muscles of decerebrate cats (N=14) to record EMG or manometry, and investigated the effects of body position on the esophago-upper esophageal sphincter (UES) contractile reflex (EUCR), esophago-UES relaxation reflex (EURR), esophagus-stimulated pharyngeal swallow response (EPSR), secondary peristalsis (SP), and pharyngeal swallow (PS)...
December 20, 2017: Pediatric Research
Simon Malenfant, Patrice Brassard, Myriam Paquette, Olivier Le Blanc, Audrey Chouinard, Valérie Nadeau, Philip D Allan, Yu-Chieh Tzeng, Sébastien Simard, Sébastien Bonnet, Steeve Provencher
BACKGROUND: Functional cerebrovascular regulatory mechanisms are important for maintaining constant cerebral blood flow and oxygen supply in heathy individuals and are altered in heart failure. We aim to examine whether pulmonary arterial hypertension (PAH) is associated with abnormal cerebrovascular regulation and lower cerebral oxygenation and their physiological and clinical consequences. METHODS AND RESULTS: Resting mean flow velocity in the middle cerebral artery mean flow velocity in the middle cerebral artery (MCAvmean); transcranial Doppler), cerebral pressure-flow relationship (assessed at rest and during squat-stand maneuvers; analyzed using transfer function analysis), cerebrovascular reactivity to CO2, and central chemoreflex were assessed in 11 patients with PAH and 11 matched healthy controls...
October 12, 2017: Journal of the American Heart Association
Noah J Marcus, Rodrigo Del Rio, Yanfeng Ding, Harold D Schultz
KEY POINTS: Enhanced carotid body chemoreflex activity contributes to development of disordered breathing patterns, autonomic dysregulation and increases in incidence of arrhythmia in animal models of reduced ejection fraction heart failure. Chronic reductions in carotid artery blood flow are associated with increased carotid body chemoreceptor activity. Krüppel-like Factor 2 (KLF2) is a shear stress-sensitive transcription factor that regulates the expression of enzymes which have previously been shown to play a role in increased chemoreflex sensitivity...
September 6, 2017: Journal of Physiology
Tabinda Zafar, Charly Brouillard, Laurence Lanfumey, Caroline Sévoz-Couche
Recent studies have demonstrated that a mild stimulation of the dorsomedian nucleus of the hypothalamus (DMH), a defense area, induces the inhibition of the carotid chemoreflex tachypnea. DMH activation reduces the cardiac chemoreflex response via the dorsolateral part of the periaqueductal grey matter (dlPAG) and serotonin receptors (5-HT3 subtype) in the nucleus tractus solitarius (NTS). The objectives of this study were to assess whether dlPAG and subsequent NTS 5-HT3 receptors are involved in chemoreflex tachypnea inhibition during mild activation of the DMH...
January 2018: Neuropharmacology
Joshua M Bock, Kenichi Ueda, Aaron C Schneider, William E Hughes, Jacqueline K Limberg, Nathan S Bryan, Darren P Casey
Aging is associated with increased peripheral chemoreceptor activity, reduced nitric oxide (NO) bioavailability, as well as attenuation of cardiovagal baroreflex sensitivity (BRS), collectively increasing the risk of cardiovascular disease. Evidence suggests NO may attenuate peripheral chemoreflex sensitivity and increase BRS. Exogenous inorganic nitrate increases NO bioavailability via the nitrate-nitrite-nitric oxide pathway. Our hypothesis was that inorganic nitrate supplementation would attenuate peripheral chemoreflex sensitivity and enhance spontaneous cardiovagal BRS in older adults...
September 29, 2017: American Journal of Physiology. Heart and Circulatory Physiology
Joseph M Santin
Haldane and Priestley (1905) discovered that the ventilatory control system is highly sensitive to CO2. This "CO2 chemoreflex" has been interpreted to dominate control of resting arterial PCO2/pH (PaCO2/pHa) by monitoring PaCO2/pHa and altering ventilation through negative feedback. However, PaCO2/pHa varies little in mammals as ventilation tightly couples to metabolic demands, which may minimize chemoreflex control of PaCO2. The purpose of this synthesis is to (1) interpret data from experimental models with meager CO2 chemoreflexes to infer their role in ventilatory control of steady-state PaCO2, and (2) identify physiological causes of respiratory acidosis occurring normally across vertebrate classes...
September 29, 2017: Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology
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