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PurposeTo assess the validity of and compare applanation and rebound tonometry readings of intraocular pressure in alert normal chicks from ages 3 to 45 days.MethodsIntraocular pressures (IOPs) were measured weekly in awake White Leghorn chicks, from ages 3-45 days (n = 22-30 per age group), with both applanation Tono-Pen and rebound TonoLab tonometers. Three repeated measurements on individual eyes were used to derive variance data for both instruments at each age. Calibration curves were also derived for each instrument and each age, weekly from ages 10-45 days (n = 3-4 per age group), from in situ manometry data collected over IOP settings of 0 to 100 mmHg in 5 mmHg steps in cannulated eyes.ResultsThe TonoLab showed less within measurement variability, but more variability with age, than the Tono-Pen. The coefficient of variation ranged from 3.8-8.3% for the TonoLab, compared to 11.0-19.7% for the Tono-Pen across all ages. For the youngest, 3 day-old chicks, mean IOPs recorded with the Tono-Pen and TonoLab were not significantly different (17.0 ± 5.6 and 15.2 ± 3.7 mmHg, respectively, P = .27). However, with increasing age, IOP readings significantly increased for the TonoLab (P < .001), whereas Tono-Pen readings did not. Compared to manometry settings, the Tono-Pen tended to underestimate IOPs while the TonoLab overestimated IOPs over the range 20-60 mmHg, saturating thereafter; there were also age-dependent differences for the TonoLab.ConclusionsBoth the Tono-Pen and TonoLab gave IOP readings that differed from manometry settings in normal young chicks over some or all of the ages tested. These results reinforce the importance of calibrating clinical tonometers in animal studies involving IOP as a key variable.

We test a new wireless soft capacitance sensor (CAP) based on applanation tonometry at the radial and dorsalis pedis arteries against the gold standard, invasive arterial line (A-Line), for continuous beat to beat blood pressure (BP) measurements in the Operating Room during surgical procedures under anesthesia in 17 subjects with the mean age and body mass index (BMI) of 57. 35 ± 18.72 years and 27.36 ± 4.20 kg/m2, respectively. We have identified several parameters to monitor in order to compare how well the CAP sensor tracks the entire hemodynamic waveform as compared to the A-Line. This includes waveform similarity, heart rate (HR), absolute systolic BP (SBP), diastolic BP (DBP), and temporal response to a vasopressor. Overall, the CAP sensor shows good correlations with A-Line with respect to hemodynamic shape (r > 0.89), HR (mean bias = 0.0006; SD = 0.17), absolute SBP, and DBP in a line of best fit (slope = 0.98 in SBP; 1.08 in DBP) and the mean bias derived from Bland-Altman method to be 1.92 (SD = 12.55) in SBP and 2.38 (SD = 12.19) in DBP across body habitus and age in OR patients under general anesthesia. While we do observe drifts in the system, we still obtain decent correlations with respect to the A-Line as evidenced by excellent linear fit and low mean bias across patients. When we post-process using a different calibration method to account for the drift, the mean bias and SD improve dramatically to -1.85 and 7.19 DBP as well as 1.43 and 7.43 SBP, respectively, indicating a promising potential for improvement when we integrate strategies to account for movement identified by our integrated accelerometer data.

We test a new wireless soft capacitance sensor (CAP) based on applanation tonometry at the radial and dorsalis pedis arteries against the gold standard, invasive arterial line (A-Line), for continuous beat to beat blood pressure (BP) measurements in the Operating Room during surgical procedures under anesthesia in 17 subjects with the mean age and body mass index (BMI) of 57. 35 ± 18.72 years and 27.36 ± 4.20 kg/m2, respectively. We have identified several parameters to monitor in order to compare how well the CAP sensor tracks the entire hemodynamic waveform as compared to the A-Line. This includes waveform similarity, heart rate (HR), absolute systolic BP (SBP), diastolic BP (DBP), and temporal response to a vasopressor. Overall, the CAP sensor shows good correlations with A-Line with respect to hemodynamic shape (r > 0.89), HR (mean bias = 0.0006; SD = 0.17), absolute SBP, and DBP in a line of best fit (slope = 0.98 in SBP; 1.08 in DBP) and the mean bias derived from Bland-Altman method to be 1.92 (SD = 12.55) in SBP and 2.38 (SD = 12.19) in DBP across body habitus and age in OR patients under general anesthesia. While we do observe drifts in the system, we still obtain decent correlations with respect to the A-Line as evidenced by excellent linear fit and low mean bias across patients. When we post-process using a different calibration method to account for the drift, the mean bias and SD improve dramatically to -1.85 and 7.19 DBP as well as 1.43 and 7.43 SBP, respectively, indicating a promising potential for improvement when we integrate strategies to account for movement identified by our integrated accelerometer data.

PurposeTo assess the validity of and compare applanation and rebound tonometry readings of intraocular pressure in alert normal chicks from ages 3 to 45 days.MethodsIntraocular pressures (IOPs) were measured weekly in awake White Leghorn chicks, from ages 3-45 days (n = 22-30 per age group), with both applanation Tono-Pen and rebound TonoLab tonometers. Three repeated measurements on individual eyes were used to derive variance data for both instruments at each age. Calibration curves were also derived for each instrument and each age, weekly from ages 10-45 days (n = 3-4 per age group), from in situ manometry data collected over IOP settings of 0 to 100 mmHg in 5 mmHg steps in cannulated eyes.ResultsThe TonoLab showed less within measurement variability, but more variability with age, than the Tono-Pen. The coefficient of variation ranged from 3.8-8.3% for the TonoLab, compared to 11.0-19.7% for the Tono-Pen across all ages. For the youngest, 3 day-old chicks, mean IOPs recorded with the Tono-Pen and TonoLab were not significantly different (17.0 ± 5.6 and 15.2 ± 3.7 mmHg, respectively, P = .27). However, with increasing age, IOP readings significantly increased for the TonoLab (P < .001), whereas Tono-Pen readings did not. Compared to manometry settings, the Tono-Pen tended to underestimate IOPs while the TonoLab overestimated IOPs over the range 20-60 mmHg, saturating thereafter; there were also age-dependent differences for the TonoLab.ConclusionsBoth the Tono-Pen and TonoLab gave IOP readings that differed from manometry settings in normal young chicks over some or all of the ages tested. These results reinforce the importance of calibrating clinical tonometers in animal studies involving IOP as a key variable.

Background: The prevalence of obese children with sleep disordered breathing (SDB) is increasing. Obesity and SDB are independent cardiovascular risk factors, of which arterial stiffness is an early sign. Pulse wave velocity (PWV), is a marker of arterial stiffness and central systolic blood pressure (cSBP) is a better predictor of cardiovascular outcome than peripheral blood pressure. Therefore, we aimed to determine PWV and cSBP in overweight/obese or normal weight children with sleep disordered breathing (SDB), and non-snoring normal weight controls. Method(s): Children (3-18 y) with SDB (overweight/obese [BMI z-scores >= 1.04], n = 48; normal weight n = 44) referred for clinical assessment of SDB and normal weight non-snoring controls recruited from the community (n = 38) underwent overnight polysomnography. PWV was calculated using photoplethysmography. cSBP was calculated using applanation tonometry in a subset of children older than 8 y (n = 55) who had usable waveforms. Result(s): Overweight/obese SDB group had higher PWV (mean cm/s (95% CI); wake: 366 (355-380); sleep: 340 (324-357)), than the normal-weight SDB group (wake: 257 (247-267), p = 0.002; sleep: 255 (242-269), p = 0.005), and non-snoring controls (wake: 238 (226-249), p = 0.002; sleep: 235 (220-250), p < 0.001). The normal-weight SDB group had higher PWV than controls (p = 0.03). Overweight/obese children with SDB had higher cSBP (105 (100-110) mmHg) compared with the normal weight children with SDB (96 (90-102)) and the non-snoring controls (97 (91-104); p < 0.05 for both). Conclusion(s): This study suggests that overweight/obesity substantially worsens the cardiovascular sequelae of SDB, highlighting the imperative to treat obesity and SDB in children early in order to reduce future cardiovascular disease risk.Copyright © 2018 Elsevier B.V.

Background: The prevalence of obese children with sleep disordered breathing (SDB) is increasing. Obesity and SDB are independent cardiovascular risk factors, of which arterial stiffness is an early sign. Pulse wave velocity (PWV), is a marker of arterial stiffness and central systolic blood pressure (cSBP) is a better predictor of cardiovascular outcome than peripheral blood pressure. Therefore, we aimed to determine PWV and cSBP in overweight/obese or normal weight children with sleep disordered breathing (SDB), and non-snoring normal weight controls. Method(s): Children (3-18 y) with SDB (overweight/obese [BMI z-scores >= 1.04], n = 48; normal weight n = 44) referred for clinical assessment of SDB and normal weight non-snoring controls recruited from the community (n = 38) underwent overnight polysomnography. PWV was calculated using photoplethysmography. cSBP was calculated using applanation tonometry in a subset of children older than 8 y (n = 55) who had usable waveforms. Result(s): Overweight/obese SDB group had higher PWV (mean cm/s (95% CI); wake: 366 (355-380); sleep: 340 (324-357)), than the normal-weight SDB group (wake: 257 (247-267), p = 0.002; sleep: 255 (242-269), p = 0.005), and non-snoring controls (wake: 238 (226-249), p = 0.002; sleep: 235 (220-250), p < 0.001). The normal-weight SDB group had higher PWV than controls (p = 0.03). Overweight/obese children with SDB had higher cSBP (105 (100-110) mmHg) compared with the normal weight children with SDB (96 (90-102)) and the non-snoring controls (97 (91-104); p < 0.05 for both). Conclusion(s): This study suggests that overweight/obesity substantially worsens the cardiovascular sequelae of SDB, highlighting the imperative to treat obesity and SDB in children early in order to reduce future cardiovascular disease risk.Copyright © 2018 Elsevier B.V.

Applanation tonometry is a non-invasive and reproducible method that evaluates the pulse wave, allowing estimation of arterial elasticity in pathology or health conditions affecting the cardiovascular system such as hypertension, diabetes mellitus, dyslipidemia and others. In this study we set ourselves the objective of evaluating, through applanation tonometry, pulse wave velocity, augmentation pressure and augmentation index (IAx) in patients with normal-high blood pressure and high blood pressure. METHODOLOGY: This was a descriptive cross-sectional study with a sample of 90 patients of both sexes, aged between 18 and 70 years. Once the written consent was signed, they were given a complete medical history, physical examination, peripheral arterial pressure and categorized by study group. Later, they were determined by applanation tonometry, using Sphygmocor®, the pulse waveform and parameters central arterial pressures, pulse wave velocity, pulse pressure, augmentation pressure and IAx. RESULTS: It was observed that as increased central blood pressure, especially systolic and arterial pulse pressure increased, the speed of pulse wave, pressure augmentation and IAx, a significantly (P <0.05) and there was a positive correlation (r = 0.2 to 0.5, p <0.05). CONCLUSION: The pulse wave, measured through applanation tonometry, could provide tools for the early detection of vascular alterations in already asymptomatic individuals and / or with established pathology causing arterial stiffness, such as arterial hypertension., La tonometría por aplanamiento es un método no invasivo y reproducible que evalúa la onda de pulso, permitiendo estimar la elasticidad arterial en patología o condiciones de salud que afectan el sistema cardiovascular como hipertensión, diabetes mellitus, dislipidemia y otras. En este estudio nos planteamos como objetivo evaluar, a través de tonometría por aplanamiento, la velocidad de onda de pulso, la presión de aumentación y el índice de aumentación (IAx) a pacientes con presión arterial-normal, normal-alta e hipertensión arterial. METODOLOGÍA: se trató de un estudio descriptivo transversal, con una muestra conformada por 90 pacientes de ambos sexos, con edades entre 18 y 70 años. Una vez firmado el consentimiento escrito, se les realizó historia clínica completa, examen físico, se midió la presión arterial periférica y se categorizaron por grupo de estudio. Posteriormente, se les determinaron por tonometría por aplanamiento, usando Sphygmocor®, la onda de pulso y los parámetros presiones arteriales centrales, velocidad de onda de pulso, presión de pulso, presión de aumentación e IAx. RESULTADOS: se observó que a medida que aumentaron las presiones arteriales centrales, en especial, la sistólica y la presión de pulso arterial se incrementaron, la velocidad de onda de pulso, la presión de aumentación y el IAx, de una manera significativa (p?0,05) existiendo además una correlación positiva (r=0,2 a 0,5; p<0,05). CONCLUSIÓN: la onda de pulso, medida a través de la tonometría por aplanamiento podría aportar herramientas para la detección precoz de alteraciones vasculares en individuos aún asintomáticos y/o con patología ya establecidas que ocasionen rigidez arterial, como la hipertensión arterial.

Arterial pulse wave velocity (PWV) depends on blood pressure (BP). Correction of PWV for BP is commonly performed using a statistical approach, requiring a patient cohort. We recently developed a mechanistic, model-predictive approach to assess BP-independent changes in carotid PWV (cPWV) at the level of the individual. The goal of the present study is to compare our novel technique to conventional statistical correction, in the context of anti-cancer therapy using anti-angiogenic drugs (AADs). AADs frequently lead to a PWV increase, but also to hypertension, underlining the need for BP correction of PWV measurements. We obtained carotid artery systolic and diastolic cross-sectional areas (echotracking) and corresponding BPs (tonometry) in 48 patients before starting AAD treatment (sorafenib/sunitinib), and at four follow-up visits spaced 2 weeks apart. For each patient, we derived cPWV and a baseline single-exponential BP cross-sectional area curve. Based on these baseline curves and follow-up BPs, we predicted cPWV at follow-up due to BP. By comparing predicted and measured cPWVs at follow-up, we assessed the BP-independent cPWV increase. In the same way, we assessed whether diastolic cross-sectional area (A(d)) changed beyond the BP-induced amount. The AAD-induced BP-independent increase in cPWV was 0.43(0.09,0.77) ms(-1) (mean (95% CI), P=0.014, mechanistic approach) and 0.48(0.14,0.82) ms(-1) (P=0.006, statistical approach). Ad increased with 1.92(0.93,2.92) mm(2) (P <0.001) and 2.14(1.06,3.23) mm(2) (P <0.001), respectively. In conclusion, the present study demonstrates the feasibility and potential of our mechanistic, model-predictive approach to quantify BP-independent effects on arterial stiffness at the level of the individual, in a clinically relevant setting of AAD therapy.

Arterial pulse wave velocity (PWV) depends on blood pressure (BP). Correction of PWV for BP is commonly performed using a statistical approach, requiring a patient cohort. We recently developed a mechanistic, model-predictive approach to assess BP-independent changes in carotid PWV (cPWV) at the level of the individual. The goal of the present study is to compare our novel technique to conventional statistical correction, in the context of anti-cancer therapy using anti-angiogenic drugs (AADs). AADs frequently lead to a PWV increase, but also to hypertension, underlining the need for BP correction of PWV measurements. We obtained carotid artery systolic and diastolic cross-sectional areas (echotracking) and corresponding BPs (tonometry) in 48 patients before starting AAD treatment (sorafenib/sunitinib), and at four follow-up visits spaced 2 weeks apart. For each patient, we derived cPWV and a baseline single-exponential BP cross-sectional area curve. Based on these baseline curves and follow-up BPs, we predicted cPWV at follow-up due to BP. By comparing predicted and measured cPWVs at follow-up, we assessed the BP-independent cPWV increase. In the same way, we assessed whether diastolic cross-sectional area (A(d)) changed beyond the BP-induced amount. The AAD-induced BP-independent increase in cPWV was 0.43(0.09,0.77) ms(-1) (mean (95% CI), P=0.014, mechanistic approach) and 0.48(0.14,0.82) ms(-1) (P=0.006, statistical approach). Ad increased with 1.92(0.93,2.92) mm(2) (P <0.001) and 2.14(1.06,3.23) mm(2) (P <0.001), respectively. In conclusion, the present study demonstrates the feasibility and potential of our mechanistic, model-predictive approach to quantify BP-independent effects on arterial stiffness at the level of the individual, in a clinically relevant setting of AAD therapy.

Cardiovascular disease (CVD) is a leading cause of morbidity and mortality in both the general and at-risk populations [e.g., end-stage renal disease (ESRD) patients]. Arterial stiffness is a major contributor to the occurrence and progression of CVD. The ability to measure arterial stiffness accurately and easily could be important in the detection and prevention of CVD. Applanation tonometry (AT) is considered the reference method for determining pulse wave velocity (PWV), an index of arterial stiffness; however, AT has been reported to have several limitations and practical problems. Photopleysmography (PPG) may be a potential alternative to AT in the determination of PWV, but its validity and reliability need to be more definitively established. Second, there is conflicting evidence as to whether peripheral measurements of arterial stiffness can be used as a surrogate for central measures. Accordingly, the primary objectives of this dissertation were: a) to aid in establishing the validity and/or reliability of PWV assessed using the new PPG method compared to the reference (AT) method (Study 2 and Study 3), and b) to provide further insight regarding whether peripheral PWV by PPG is in fact a valid surrogate measure of central PWV by PPG (Study 2). There are also many factors that can affect the interpretation of arterial stiffness measurements that are poorly understood in terms of their mechanisms and magnitude of impact. As such, this dissertation also addresses: c) the influence of hemodialysis (HD) on arterial stiffness (Study 1) and d) the influence of maximal aerobic exercise on arterial stiffness (Study 3). The findings of the studies in this dissertation established the validity and/or reliability of the PPG method (Study 2 and Study 3), refuted the use of peripheral PWV measurements as surrogates for central ones (Study 2), clarified the influence of HD on arterial stiffness (Study 1), and confirmed the acute impact of aerobic exercise on arterial sti, Thesis (Ph.D, Rehabilitation Science) -- Queen's University, 2014-12-15 19:40:34.894

Pathophysiologic mechanisms of central aortal pressure (CAP) are more complex than those of peripheral pressure, measured at brachial artery level. CAP indirectly reflects the state of circulatory system as a whole, since it is modulated by aorta elasticity, as well as structure and function of middle arteries and microcirculatory vessels. The difference between central and peripheral systolic blood pressure is maximal in young people and decreases in the elderly. For non-invasive CAP measurement, radial artery applanation tonometry is used, with subsequent computer transformation of peripheral pulse wave into central one, or applanation tonometry of carotid artery. The growing body of evidence supports the use of CAP measurement in assessing cardiovascular risk assessment and comparing various therapeutic regimens.

Most of large controlled randomized trials have not revealed superiority of "new" over "old" anti hypertensive drugs and posed a question of value of surrogate criteria for comparison of various treatment regimes. Data of ASCOT-CAFE trials allow to assume that estimation of central blood pressure (BP) opens novel perspectives in this direction. Most affordable methods of noninvasive measurement of central BP are radial artery applanation tonometry with subsequent computer transformation of peripheral to central pulse wave, and carotid artery applanation tonometry. Contrary to peripheral BP central BP level is modulated by elastic properties of major arteries and structural-functional state of medium caliber arteries and microcirculatory vascular bed, and thus is an index indirectly reflecting the state of the whole cardiovascular bed. Differences between central and peripheral BP levels are most clearly expressed in young age and diminish in the elderly. Effects of anti hypertensive drugs on central BP may vary at the account of difference of points of application of their effects in vascular bed. Prognostic and clinical value of the central BP requires further investigation.

In this work we compared parameters of central arterial pressure (AP) on the basis of analysis of pulse wave in young men in dependence of AP phenotype determined by repetitive clinical measurements and 24 hour AP monitoring (24HAPM). Comparison of characteristics of central pulse wave was carried out in 12 men with normal AP, 36 men with arterial hypertension (AH) according to clinical measurements and 24HAPM, and 17 men with white coat hypertension (WCH). Mean age was 21.0±2.1 years. Differences in levels of pulse pressure (PP) between groups with AH were revealed only at the level of the aorta. Studied patients with normal AP and 24HAPM did not differ by such characteristics as index of increment and reflected wave appearance time. Studied patients with AH confirmed by 24HAPM were characterized by significantly greater augmentation of central PP (100.0±12.6% vs 96.6±11.8% in persons with normal AP and 95.6±15.0% with WCH, p<0.05), earlier appearance of reflected wave (149.2±18.9 ms vs 160.6±16.2 and 160.3±28.6 ms, respectively, p<0.05), high rate of pulse wave propagation (8.6±1.2 m/s vs 7.2±1,2 and 7.0±1.7 m/s). Amplification was similar in three groups. The data obtained has shown that in men aged 18-25 years presence of AH, confirmed by 24HAPM) is associated with elevation of central systolic AP and PP and higher values of markers of both rigidity of the aorta and remodeling of peripheral vascular bed.