Activation of Carotid Baroreceptors and Respiratory Resistance: Disappearance of the Respiratory Component of Baroreflex in the Course of Aging

Wstęp Jednym z efektorów odruchu z baroreceptorów zatokowych są drogi oddechowe. Na uwagę zasługuje wpływ pobudzenia baroreceptorów zatokowych na opór oddechowy u ludzi w różnym wieku. Materiał i metody Badaniom poddano 125 zdrowych mężczyzn w różnych grupach wiekowych. U wszystkich badanych analizowano odpowiedź sercową (wydłużenie odstępu R-R EKG) i zmiany oporu oddechowego w odpowiedzi na pobudzenie baroreceptorów zatok szyjnych podciśnieniem aplikowanym od zewnątrz na okolicę zatok szyjnych. Opór oddechowy mierzono metodą oscylacyjną. Wyniki W młodszych grupach wiekowych (21-40 lat) obserwowano spadek oporu obwodowego w odpowiedzi na pobudzenie baroreceptorów tętniczych. Reakcja ta była stopniowo coraz mniej wyraźna u badanych z coraz starszych grup wiekowych, a u osób w wieku 51-70 lat całkowicie zanikła. Odpowiedź sercowa była mniejsza w kolejnych grupach wiekowych. Wnioski Uzyskane wyniki świadczą o zmniejszającej się wraz z wiekiem efektywności odruchu z baroreceptorów zatokowych, obejmującej zarówno komponent sercowy, jak i oddechowy odruchu.Background Previous study shows a respiratory effector of carotid baroreceptor activation: the respiratory resistance. In the present study the age-related changes of respiratory response to carotid baroreceptor activation were studied. Material and methods 125 healthy men 21-70 years old were involved in the study. The heart responses (the increase in R-R interval) and reflex changes of respiratory resistance were analysed during activation of carotid baroreceptors. Results In the younger groups of subjects (21-40) a brief decrease of respiratory resistance was observed in response to carotid baroreceptors activation. In the course of aging we found a decrease of heart response and a disappearance of respiratory response. Conclusions We suggest that both components of carotid baroreceptors reflex: cardiac and respiratory, are impaired during biological aging

Is Low Baroreflex Sensitivity only a Consequence of Essential Hypertension or also a Factor Conditioning Its Development?

Baroreflex sensitivity (BRS) is an individually characteristic index. It fluctuates spontaneously even at rest and therefore a particular value measured represents an approximate estimate of its size. Bearing in mind the fact that essential hypertension (EH) is a disease of higher age, the majority of studies done in previous years were naturally focused on BRS in older population. The increased arterial stiffness, increased IMT, and sympathetic activation in obesity represent indubitable factors which lead to hypertension and, consequently, result in a decrease of BRS. The hypothesis ensuing from these studies, which states that the drop in BRS accompanies the development of hypertension as a secondary manifestation of the disease, is proved by these studies. On the other hand, measurements of BRS in children and adolescents and the first genetic studies on the inborn conditionality of BRS have provided enough evidence that some individuals possess congenitally low BRS. Without a targeted study, we cannot even speculate on how this assumption will manifest itself in advanced age in terms of increased risk of sudden cardiac death, since in the meantime the long-term pathological influence of other mechanisms lowering BRS will have presented itself in the other risky patients. Low BRS will manifest itself as blood pressure hyperreactivity. It may lead to white coat hypertension in adolescents as a step in the development of EH. Therefore, congenitally low BRS may be considered as another risk factor for the development of EH. This is the reason why in the young population increased emphasis should be put on the prevention of obesity and sufficient physical activity as on easily influence able stimuli which additively increase blood pressure.Baroreflex sensitivity (BRS) is an individually characteristic index. It fluctuates spontaneously even at rest and therefore a particular value measured represents an approximate estimate of its size. Bearing in mind the fact that essential hypertension (EH) is a disease of higher age, the majority of studies done in previous years were naturally focused on BRS in older population. The increased arterial stiffness, increased IMT, and sympathetic activation in obesity represent indubitable factors which lead to hypertension and, consequently, result in a decrease of BRS. The hypothesis ensuing from these studies, which states that the drop in BRS accompanies the development of hypertension as a secondary manifestation of the disease, is proved by these studies. On the other hand, measurements of BRS in children and adolescents and the first genetic studies on the inborn conditionality of BRS have provided enough evidence that some individuals possess congenitally low BRS. Without a targeted study, we cannot even speculate on how this assumption will manifest itself in advanced age in terms of increased risk of sudden cardiac death, since in the meantime the long-term pathological influence of other mechanisms lowering BRS will have presented itself in the other risky patients. Low BRS will manifest itself as blood pressure hyperreactivity. It may lead to white coat hypertension in adolescents as a step in the development of EH. Therefore, congenitally low BRS may be considered as another risk factor for the development of EH. This is the reason why in the young population increased emphasis should be put on the prevention of obesity and sufficient physical activity as on easily influence able stimuli which additively increase blood pressure

O idoso portador de sopro sistólico

Resumo: Com o objetivo de se levantar a prevalência e de identificar-se a natureza dos sopros sistólicos na terceira idade, foram estudados, prospectivamente, 170 idosos, 77 do sexo masculino e 93 feminino, média etária de 72,84 ± 7,15 anos, realizando-se exame clínico e eletrocardiograma em todos os pacientes, complementados com radiografia de tórax e ecocardiograma unidimensional nos portadores de sopro. Ao exame clínico detectou-se a presença de sopro sistólico em 71 (41,76%) idosos - grupo I não identificado em 99 (58,24%) pacientes - grupo II -. Houve predominância significativa de sopro mesossistólico de ejeção, grau 1-2/6, observado em 78,87% dos pacientes do grupo I. Hipertensão sistólica isolada foi observado em 30,99% e 12,12% e hipertensão sisto-diastólica associada em 21,13% e 13,13%, respectivamente, nos pacientes do grupo I e do grupo II. A diferença entre os dois grupos mostrou- se estatisticamente significativa. Com relação ao eletrocardiograma, 26,76% dos traçados foram normais nos pacientes do grupo I, enquanto 51,51% o foram nos pacientes do grupo II. Os achados que apresentaram diferença mais expressiva nos dois grupos foram: sobrecarga ventricular esquerda, observada em 36,62% no grupo I e 12,12% no grupo II (p< 0,05); sobrecarga atrial esquerda, em 21,27% e 6,06% e extrassístoles ventriculares em 14,08% e 5,05%, respectivamente, nos grupos I e II. Quanto à radiografia de tórax (grupo I), os principais achados foram: ectasia de aorta em 92,75% dos idosos, sendo 42,03% com calcificação de croça e cardiomegalia em 43,48%. A média do índice cardiotorácico foi de 50,20 ± 6,46%. À ecocardiografia unidimensional (grupo I), observou- se dilatação da raiz da aorta em 15,94% e alterações na valva aórtica em 30,43% dos pacientes, sendo 10,14 com sinais sugestivos de calcificação e 20,29% com folhetos espessados, dos quais 14,49% com abertura diminuída. Hipertrofia septal assimétrica foi evidenciada em 2,90%, calcificação do anel mitral em 4,35% e prolapso de val^a mitral em 4,35%. Quando ao ventrículo esquerdo, 18,84% dos pacientes apresentaram hipertrofia, 24,64% com dilatação e 20,29% com hipocontratilidade. 0 exame foi normal em 34,78% dos pacientes. Em conclusão, observa-se uma alta prevalência de sopro sistólico na terceira idade, evidenciando-se amplo espectro de achados fisiopatológicos que contribuem para sua gênese, decorrentes de alterações morfo-funcionais próprias da senescência e/ou processos patológicos. Justifica-se uma avaliação cardiológica mais acurada através de métodos complementares não invasivos para se determinar, com segurança, as repercussões hemodinamicas, uma vez que a anamnese e o exame físico do idoso nem sempre refletem a gravidade do quadro

The biochemical and clinical pharmacology of debrisoquine

Imperial Users onl

Cardiac cycle related modulation of electrocutaneous pain and tactile stimuli

Research suggests hypertension is associated with reduced somatosensory perception. Further, natural fluctuations in blood pressure (BP) across the cardiac cycle have been shown to modulate nociceptive responding, pain and tactile sensitivity, suggesting that arterial baroreceptors may be important moderators of somatosensation. This thesis further examined the influence of natural fluctuations in BP, and thus baroreceptor activity, across the cardiac cycle on electrocutaneous pain and tactile sensory thresholds and pain-related evoked potentials (PREPs) in normotensive individuals. Study 1 found pain thresholds were higher, i.e. pain was reduced, during systole compared to diastole. Further analysis revealed only participants with low-normal systolic BP displayed this cardiac cycle modulation, suggesting tonic BP may moderate cardiac cycle-related pain modulation. In the second study, tactile sensory thresholds did not vary across the cardiac cycle. However, when participants were split into high-normal and low-normal BP groups, interactions between BP and tactile sensory thresholds across the cardiac cycle were revealed. This finding suggests tonic BP may be an important factor determining the cardiac cycle modulation of tactile sensation. Study 3 found no variation in the N2 or P2 peak amplitudes, or N2-P2 peak-to-peak amplitudes across the cardiac cycle at scalp recording sites Cz, C3, or C4. Furthermore, BP median split analyses revealed no BP Group or interaction effect. As previous work reported a systolic dampening of PREPs, these data suggest the cardiac cycle-related modulation of PREPs may not be as robust as other measures of pain such as the nociceptive flexion reflex. Study 4 reported, in line with Study 3, no cardiac cycle related modulation of PREPs following stimulation of the right and left hands. However, a Hand × Scalp Electrode Site × Interval interaction was revealed for N2 peak amplitudes. These data suggest that the combination of side of stimulation and scalp recording site may be important in determining the patterning of PREPs across the cardiac cycle. Taken together, the findings of these studies suggest that pain perception, and to a lesser extent tactile sensation, are influenced by natural variations in BP across the cardiac cycle. However, modulation appears dependent on tonic BP. Conversely, pain-related brain activity across the cardiac cycle was not affected by tonic BP, but may be influenced by the combination of stimulation and recording sites

Carotid sinus baroreceptor reflexes and their interactions with trigeminal and respiratory stimuli in man, and their modification by sex, age, hypertension, antihypertensive therapy, alcohol and endogenous opioids

The work in this thesis follows the use of the established neck suction technique for the assessment of carotid sinus baroreceptors in man and the development of a computer-based system for the analysis of responses to baroreceptor, trigeminal and respiratory stimuli. These methods have been used to study the carotid sinus baroreceptor reflexes, their interactions with trigeminal and respiratory stimuli, and their modification by gender, alcohol consumption, increasing age, essential hypertension and antihypertensive therapy. The role of endogenous opioids as putative neurotransmitters in these reflex pathways has been examined. The results obtained indicate that; 1) Endogenous opioids do not modulate carotid sinus baroreceptor reflexes and their interactions in normal man. 2) There was a difference in the extent of the linear portion of the carotid sinus baroreceptor heart rate reflex between closely age matched groups of young men and women. 3) The acute administration of alcohol reduced the sensitivity of the carotid sinus baroreceptor heart-rate reflex, but did not alter the response to cold facial stimuli, or the nature of the interaction of these (a simple linear summation of the effects of each applied separately). The effectiveness of respiratory stimuli in reducing vagal tone may have been reduced by alcohol. 4) The sensitivity of the carotid sinus baroreceptor reflex declined with increasing age, and with hypertension. This decline was significantly correlated with age, systolic, diastolic and arterial pulse pressure. 5) The response to trigeminal (cold facial) stimuli declined with age, but did not decline further in hypertension. Because the trigeminal and baroreceptor reflexes share a common efferent pathway, the vagus nerve, this is strong evidence for the preservation of the efferent pathway of the baroreceptor reflex in essential hypertension. The qualitative nature of the interaction between inspiration and the carotid sinus baroreceptor reflex was unchanged by hypertension. 6) The administration of two different antihypertensive agents, atenolol and lisinopril, whilst effective in reducing blood pressure, did not alter the sensitivity of the carotid sinus baroreceptor reflex, but the reflex was reset in each case to operate around a lower blood pressure, and with atenolol was also reset towards bradycardia. The response to cold facial stimuli, and the interaction with the carotid sinus baroreceptor heart- rate reflex were unchanged by therapy with either agent

Autonomic regulation and blood pressure in children

Vagal baroreflex sensitivity (BRS) is a measure of short term blood pressure (BP) regulation through alterations in heart rate. Low BRS reflects impaired autonomic system regulation and has been found to be a surrogate marker for cardiovascular health. In particular, it has found to be associated with the pathogenesis of adult hypertension. However, only limited information exists as to the negative consequences of childhood BP on baroreflex function. The objective of this study was to investigate BRS in children with 2 different BP profiles while controlling for the effects of age, maturation, sex, and body composition. A preliminary subsample of 11-14 year-old children from the HBEAT (Heart Behavioural Environmental Assessment Team) Study was selected. The children were divided into 2 BP groups; high BP (HBP; 2:95tl1 percentile, n=21) and normal BP (NBP; <90th percentile, n=85). Following an initial 15 minutes of supine rest, 5 minutes of continuous beat-to-beat BP (Finapres) and RR interval (RRI) were recorded (standard ECG). Spectral indices were computed using Fast Fourier Transform and transfer function analysis was used to compute BRS. High frequency (HF) and low frequency (LF) power spectral areas were set to 0.15-0.4 Hz and 0.04-0.15 Hz, respectively. Body composition was measured using body mass index. After adjusting for body composition, maturation, age and sex ANCOV A results were as follows; LF and HF BRS, LF and HF RRI, and RRI total power were lower in the HBP versus NBP participants (p<0.05). As well, LF IHF SBP ratio was significantly higher in the HBP compared to the NBP group (p<0.05). The regression coefficients (unstandardized B) indicated that in changing groups (NBP to HBP) LF and HF BRS decreases by 4.04 and 6.18 ms/mmHg, respectively. Thus, as BP increases, BRS decreases. These data suggest that changes in autonomic activity occur in children who have HBP, regardless of age, sex, maturation, and body composition. Thus, despite their young age and relatively short amount of time having high BP compared with adults, these children are already demonstrating poor BP regulation and reduced cardiovagal activity. Given that childhood BP is associated with hypertension in adulthood, there is a growing concern in regards to the current cardiovascular health of our children and future adults

Circulatory control in hypertension : studies in experimental renal hypertension and some aspects of human essential hypertension.

Reflex function and the role of autonomic and non—autonomic factors in circulatory haemodynamics have been studied in unanaesthetized rabbits with renal hypertension which was produced by bilateral wrapping of the kidneys with cellophane

Can frailty inform the management of hypertension in older people?

Background Hypertension increases the risk of cardiovascular disease. Whilst blood pressure (BP) lowering can reduce this risk, it can also cause adverse effects. This PhD study uses mixed methods to explore the utility of frailty to identify older people for whom the association of BP and outcomes is different. Methods Meta-analysis summarised observational studies to date. A retrospective cohort study used linked electronic health records from the Welsh Secure Anonymised Information Linkage (SAIL) databank. Frailty was measured using the electronic frailty index. Time to event analysis measured first ever major adverse cardiovascular event (MACE), all-cause mortality and injurious falls. Narrative interviews explored the perspectives of ten older people on the utility of frailty in managing hypertension on their terms. Results Meta-analysis identified that all-cause mortality was lower for older people who were not frail with systolic BP 140 mm Hg, but there was no association in the context of frailty. In a population of 145,598 people with hypertension over the age of 65, compared to participants who were fit, people with frailty were associated with significantly higher MACE events despite adjustment for known cardiovascular risk factors (increased risk of 38% in mild frailty, 84% in moderate frailty, 117% in severe frailty). Frailty did not modify the association of BP and outcomes, but frailty did modify the association of BP-lowering medication and outcomes. Narrative interviews explored ways in which frailty could guide hypertension management towards what matters most to the individual. Discussion Findings provide evidence that frailty can usefully identify older people with increased risk of cardiovascular and non-cardiovascular outcomes in the context of hypertension management and suggest that the modifying effect of frailty in this context is in the degree to which someone sustains benefit or suffers adverse effects of BP-lowering treatment