Respiratory change in ECG-wave amplitude is a reliable parameter to estimate intravascular volume status

Electrocardiogram (ECG) is a standard type of monitoring in intensive care medicine. Several studies suggest that changes in ECG morphology may reflect changes in volume status. The “Brody effect”, a theoretical analysis of left ventricular (LV) chamber size influence on QRS-wave amplitude, is the key element of this phenomenon. It is characterised by an increase in QRS-wave amplitude that is induced by an increase in ventricular preload. This study investigated the influence of changes in intravascular volume status on respiratory variations of QRS-wave amplitudes (ΔECG) compared with respiratory pulse pressure variations (ΔPP), considered as a reference standard. In 17 pigs, ECG and arterial pressure were recorded. QRS-wave amplitude was measured from the Biopac recording to ensure that in all animals ECG electrodes were always at the same location. Maximal QRS amplitude (ECGmax) and minimal QRS amplitude (ECGmin) were determined over one respiratory cycle. ΔECG was calculated as 100 × [(ECGmax ? ECGmin)/(ECGmax + ECGmin)/2]. ΔECG and ΔPP were simultaneously recorded. Measurements were performed at different time points: during normovolemic conditions, after haemorrhage (25 mL/kg), and following re-transfusion (25 mL/kg) with constant tidal volume (10 mL/kg) and respiration rate (15 breath/min). At baseline, ΔPP and ΔECG were both <12 %. ΔPP were significantly correlated with ΔECG (r² = 0.89, p < 0.001). Volume loss induced by haemorrhage increased significantly ΔPP and ΔECG. Moreover, during this state, ΔPP were significantly correlated with ΔECG (r² = 0.86, p < 0.001). Re-transfusion significantly decreased ΔPP and ΔECG, and ΔPP were significantly correlated with ΔECG (r² = 0.90, p < 0.001). The observed correlations between ΔPP and ΔECG at each time point of the study suggest that ΔECG is a reliable parameter to estimate the changes in intravascular volume status and provide experimental confirmation of the “Brody effect.”     

Validity of single‐point assessments for determining leg pulse wave velocity in sitting and supine positions

There has been a great deal of interest into the effects of prolonged sitting on lower limb vascular function. However, most studies use flow‐mediated dilation which is technically challenging. A simpler technique is pulse wave velocity (PWV) which can be estimated at any single arterial site of interest using a number of different calculations (Bramwell–hill [PWV_BH], β‐stiffness index [PWV_β] and blood flow [PWV_BF]). Findings from this technique would be better inferred if they compare to a standard criterion 2‐point PWV assessment. The current study used ultrasound to determine which estimation of single‐point PWV is most valid. The criterion was traditional ECG‐gated 2‐point (superficial femoral [SF]‐posterior tibialis [PT]) PWV. Single‐point estimates were calculated at the SF and PT arteries in both supine and seated positions. Single‐point PWV was considered valid if the aSEE was <1.0 m·s. Findings show that for both postural positions, the absolute standard error of estimates (aSEE) criterion of <1.0 m·s was not achieved in either the PT or SF arteries using any of the single‐point PWV calculations. However, single‐point calculations consistently demonstrated the lowest error at the SF artery using PWV_β in both supine (SF aSEE = 1.7 vs. PT 2.7 m·s) and seated (SF aSEE = 1.5 vs. PT 3.0 m·s) positions. All single‐point ΔPWV (supine – seated) calculations were higher in sitting, with PWV_β having the closest agreement (ΔSF aSEE 1.7 m·s) to the 2‐point criterion. Single‐point PWV calculations do not directly reflect regional 2‐point PWV. However, they are sensitive to change when moving from supine to seated positions.     

Simultaneous non-invasive assessment of arterial stiffness and haemodynamics - a validation study

The purpose of the study was to estimate the reliability of whole-body impedance cardiography (ICGWB)-derived pulse wave velocity (PWV) and stroke volume index to pulse pressure (SI/PP) measurements. The repeatability and reproducibility of ICGWB parameters were also determined. Agreement between the impedance and Doppler ultrasound-based PWV measurements was estimated in 25 healthy subjects in two consecutive measurements. Impedance-derived SI/PP (SIICG/PP) estimates were compared with simultaneously measured SI/PP based on thermodilution (SITD/PP) and direct Fick (SIFICK/PP) methods in 30 surgical patients. PWV measured between the aortic arch and popliteal artery using the impedance technique with selective electrode configuration (PWVIS) agreed well with the Doppler ultrasound method (PWVDOPP), the bias (PWVDOPP - PWVIS) and precision (+/- SD of differences) being 0.00 and 0.79 m s-1, respectively. PWV derived from the whole-body and popliteal impedance plethysmograms (PWVICG) overestimated slightly PWVDOPP values. The repeatability value for PWVIS was excellent, being 0.54 m s-1. The reproducibility values for PWVDOPP and PWVIS were very similar (2.17 and 2.42 m s-1, respectively). Changes in PWVIS correlated strongly with changes in PWVDOPP (r=0.74; P<0.0001), indicating that both methods reflected the true physiological variation in PWV. The agreement between SIICG/PP and SITD/PP or SIFICK was almost identical to the agreement between the SITD/PP and SIFICK/PP. In conclusion,whole-body impedance cardiography provides handy and reliable means of evaluating arterial stiffness on the basis of PWV and SI/PP simultaneously with conventional haemodynamic parameters. The method is highly repeatable and reproducible.     

Fluid challenge: tracking changes in cardiac output with blood pressure monitoring (invasive or non-invasive)

Purpose

To assess whether invasive and non-invasive blood pressure (BP) monitoring allows the identification of patients who have responded to a fluid challenge, i.e., who have increased their cardiac output (CO).

Methods

Patients with signs of circulatory failure were prospectively included. Before and after a fluid challenge, CO and the mean of four intra-arterial and oscillometric brachial cuff BP measurements were collected. Fluid responsiveness was defined by an increase in CO ≥10 or ≥15 % in case of regular rhythm or arrhythmia, respectively.

Results

In 130 patients, the correlation between a fluid-induced increase in pulse pressure (Δ_500mlPP) and fluid-induced increase in CO was weak and was similar for invasive and non-invasive measurements of BP: r² = 0.31 and r² = 0.29, respectively (both p < 0.001). For the identification of responders, invasive Δ_500mlPP was associated with an area under the receiver-operating curve (AUC) of 0.82 (0.74–0.88), similar (p = 0.80) to that of non-invasive Δ_500mlPP [AUC of 0.81 (0.73–0.87)]. Outside large gray zones of inconclusive values (5–23 % for invasive Δ_500mlPP and 4–35 % for non-invasive Δ_500mlPP, involving 35 and 48 % of patients, respectively), the detection of responsiveness or unresponsiveness to fluid was reliable. Cardiac arrhythmia did not impair the performance of invasive or non-invasive Δ_500mlPP. Other BP-derived indices did not outperform Δ_500mlPP.

Conclusions

As evidenced by large gray zones, BP-derived indices poorly reflected fluid responsiveness. However, in our deeply sedated population, a high increase in invasive pulse pressure (>23 %) or even in non-invasive pulse pressure (>35 %) reliably detected a response to fluid. In the absence of a marked increase in pulse pressure (<4–5 %), a response to fluid was unlikely.     

Associations of Urinary Caffeine and Caffeine Metabolites With Arterial Stiffness in a Large Population-Based Study

Objective

To assess the influence of caffeine on arterial stiffness by exploring the association of urinary excretion of caffeine and its related metabolites with pulse pressure (PP) and pulse wave velocity (PWV).

联合运用多普勒探头与脉搏波传感器检测脉搏波传导速度的可行性

目的 探讨联合运用超声多普勒探头与脉搏波传感器检测脉搏波传导速度(PWV)方法的可行性.方法 纳入30名正常人,分别将超声多普勒探头与脉搏波传感器放置于受试者左侧颈总动脉起始段及左侧踝部胫后动脉,将两测量点间距离与测得动脉多普勒血流流速曲线的起点和动脉脉搏波曲线起点间的传播时间相比,以所得比值作为颈-踝动脉段的PWV(caPWV);并对检测结果与动脉硬化仪检测同一受试者肱-踝动脉段PWV(baPWV)的检测结果进行相关性分析.结果 将脉搏波传感器放置于颈总动脉、多普勒探头放置于胫后动脉时的PWV与动脉硬化仪检测得到的baPWV呈显著正相关(r=0.657,P＜0.01).将多普勒探头放置于颈总动脉、脉搏波传感器放置于胫后动脉时的PWV与动脉硬化仪检测得到的baPWV呈显著正相关(r=0.526,P＜0.01).结论 联合运用超声多普勒探头与脉搏波传感器检测PWV为检测PWV提供了一种新方法,具有一定临床实用价值,值得推广.     

Assessment of aortic pulse wave velocity and cardiac diastolic function in subjects with and without the metabolic syndrome: HDL cholesterol is independently associated with cardiovascular function

OBJECTIVE—To evaluate the influence of lipid and glucose metabolism in the metabolic syndrome on aortic pulse wave velocity (PWV) and left ventricular (LV) diastolic function using magnetic resonance imaging (MRI).RESEARCH DESIGN AND METHODS—Aortic PWV and LV diastolic function were assessed using MRI in 16 subjects with the metabolic syndrome and 16 subjects without the metabolic syndrome matched for age, waist circumference, and blood pressure. The groups were compared using the unpaired t test or Mann-Whitney U test, and linear regression analysis was applied.RESULTS—Aortic PWV was increased and LV diastolic function was decreased in subjects with compared with those without the metabolic syndrome. HDL cholesterol was independently associated with aortic PWV (R = −0.470, P < 0.01) and LV diastolic function (R = −0.421, P = 0.02).CONCLUSIONS—Increased aortic PWV and decreased LV diastolic function is observed in subjects with the metabolic syndrome, regardless of blood pressure. Moreover, HDL cholesterol is independently associated with aortic PWV and LV diastolic function.Previous studies have demonstrated that the metabolic syndrome is associated with increased arterial stiffness and left ventricular (LV) dysfunction (1,2). However, the exact mechanism responsible for these alterations is unclear and has not yet been studied with magnetic resonance imaging (MRI). We hypothesized that abnormalities in lipid or glucose metabolism contribute to the adverse cardiovascular changes in the metabolic syndrome. Accordingly, the study purpose was to compare aortic pulse wave velocity (PWV) and LV function using MRI in subjects with and without the metabolic syndrome and to evaluate the relation between lipid and glucose metabolism and cardiovascular function.     

Comparison of biochemical,functional and structural aspects of arterial wall properties in elderly men

Objective. A variety of methods are available to assess arterial wall properties. The aim of this study was to investigate the relationship between some of the biochemical, functional and structural measurements of arterial wall characteristics. Material and methods. The study comprised 563 elderly men at high risk of coronary heart disease. Circulating levels of intercellular adhesion molecule‐1 (ICAM‐1), vascular cell adhesion molecule‐1 (VCAM‐1), E‐selectin, von Willebrand factor (vWF) and tissue‐type plasminogen activator antigen (tPAag) were compared with pulse wave velocity (PWV) measured by finger photoplethysmography and intima‐media thickness (IMT) and plaque score of the common carotid artery. Results. Levels of ICAM‐1 were significantly correlated with plaque score (r = 0.17, p<0.001). Levels of vWF were significantly correlated with plaque score (r = 0.11, p = 0.009) and PWV (r = 0.12, p = 0.007), and levels of tPAag were significantly correlated with PWV (r = 0.16, p<0.001). These associations, although generally weak, remained statistically significant after adjustment for relevant cardiovascular risk factors. PWV did not correlate significantly with IMT or plaque score. Conclusions. The limited intercorrelation between biochemical, functional and structural measurements of arterial wall properties observed in the present population indicate that the various methods reflect different aspects of the atherosclerotic process.     

Arterial Stiffness Assessment by Shear Wave Elastography and Ultrafast Pulse Wave Imaging: Comparison with Reference Techniques in Normotensives and Hypertensives

Shear wave elastography and ultrafast imaging of the carotid artery pulse wave were performed in 27 normotensive participants and 29 age- and sex-matched patients with essential hypertension, and compared with reference techniques: carotid–femoral pulse wave velocity (cfPWV) determined via arterial tonometry and carotid stiffness (carPWV) determined via echotracking. Shear wave speed in the carotid anterior (a–SWS) and posterior (p-SWS) walls were assessed throughout the cardiac cycle. Ultrafast PWV was measured in early systole (ufPWV–FW) and in end-systole (dicrotic notch, ufPWV-DN). Shear wave speed in the carotid anterior appeared to be the best candidate to evaluate arterial stiffness from ultrafast imaging. In univariate analysis, a-SWS was associated with carPWV (r?=?0.56, p?=?0.003) and carotid-to-femoral PWV (r?=?0.66, p < 0.001). In multivariate analysis, a–SWS was independently associated with age (R²?=?0.14, p?=?0.02) and blood pressure (R²?=?0.21, p?=?0.004). Moreover, a–SWS increased with blood pressure throughout the cardiac cycle and did not differ between normotensive participants and patients with essential hypertension when compared at similar blood pressures.     

Assessment of aortic stiffness among patients with systemic lupus erythematosus and rheumatoid arthritis by magnetic resonance imaging

To evaluate aortic stiffness by MRI in female patients with systemic lupus erythematosus (SLE) or rheumatoid arthritis (RA) in comparison to controls. We measured aortic strain, distensibility and pulse wave velocity (PWV) by MRI in 30 SLE patients, 31 RA patients and 53 matched controls. Mean PWV in SLE and RA patients were higher in comparison to controls (9.2 ± 4.4 vs. 7.6 ± 3.0 m/s, p = 0.04) and (6.2 ± 2.3 vs. 5.4 ± 1.7, p = 0.04) respectively. Aortic distensibility among RA patients was significantly lower in comparison to controls (4.4 ± 4.6 vs. 5.8 ± 4.9 kPa^?1 × 10^?3, p = 0.04). A significant correlation was found between PWV and age (r = 0.67, p < 0.001), Framingham risk score (r = 0.61, p < 0.001), waist to hip ratio (r = 0.45, p < 0.001), systolic blood pressure (r = 0.37, p = 0.01), diabetes (r = 0.32, p = 0.001) and dyslipidemia (r = 0.32, p = 0.001). In multivariate analysis for the prediction of PWV, variables which were found significant included: RA (p = 0.01), age (p < 0.001) and hypertension (p = 0.01) for patients with RA and SLE (p = 0.02), waist to hip ratio (p < 0.001) and total cholesterol (p < 0.001) for patients with SLE. Arterial stiffness, characterized by metrics of aortic distensibility and pulse wave velocity derived from MRI, is increased in SLE and RA female patients.     

Flow Complexity Estimation in Dysfunctional Arteriovenous Dialysis Fistulas using Vector Flow Imaging

Non-invasive assessment is preferred for monitoring arteriovenous dialysis fistulas (AVFs). Vector concentration assesses flow complexity, which may correlate with stenosis severity. We determined whether vector concentration could assess stenosis severity in dysfunctional AVFs. Vector concentration was estimated in four stenotic phantoms at different pulse repetition frequencies. Spectral Doppler peak velocity and vector concentration were measured in 12 patients with dysfunctional AVFs. Additionally, 5 patients underwent digital subtraction angiography (DSA). In phantoms, vector concentration exhibited an inverse relationship with stenosis severity and was less affected by aliasing in severe stenoses. In nine stenoses of 5 patients undergoing DSA, vector concentration correlated strongly with stenosis severity (first stenosis: r = –0.73, p = 0.04; other stenoses; r = –0.69, p = 0.02) and mid-stenotic diameter (first stenosis: r = 0.87, p = 0.006; other stenoses: r = 0.70, p = 0.02) as opposed to peak velocities (p > 0.05). Vector concentration is less affected by aliasing in severe stenoses and correlates with DSA in patients with dysfunctional AVF.     

Aortic pathophysiology by cardiovascular magnetic resonance in patients with clinical suspicion of coronary artery disease.

PURPOSE: To correlate cardiovascular magnetic resonance (CMR)-based measurement of aortic pulse wave velocity (PWV) with serum markers for atherosclerosis and plaque burden in the thoracic aorta. METHOD: Individuals with risk factors for coronary atherosclerosis underwent CMR pulse wave velocity examination of the descending thoracic aorta and computed tomography for coronary calcium scoring. Inversion recovery images allowed quantification of aortic plaque. Serum lipids and c-reactive protein levels were measured. RESULTS: Mean PWV did not correlate with presence of aortic plaque (p = 0.55). Subgroup analysis showed no significant correlation with PWV and total plaque. PWV and pulse pressure correlated (PP) (R2 0.38, p = 0.0003), but PWV and other predictor variables did not. Total plaque area correlated with aortic diameter (p = 0.0066). CONCLUSIONS: In patients with suspected coronary artery disease, aortic pulse wave velocity reflects increased aortic stiffness demonstrated by elevated pulse pressure, but does not directly correlate with aortic plaque or serum markers for arterial disease.     

The role of pancreatic innervation and cholecystokinin in the intestinal phase of pancreatic polypeptide release in conscious dogs

Besides vagal cholinergic mechanisms, pancreatic polypeptide (PP) secretion is thought to be mediated by hormones. This study was performed to delineate the role of extrinsic pancreatic innervation and cholecystokinin (CCK) in amino acid- and fat-stimulated PP secretion. In ten mongrel dogs, pancreatic denervation was performed by the method of Debas et al. [3]. Total denervation of the pancreas did not alter PP response to intraduodenal application of amino acids (integrated output 24434±3260 pmol/1×120 min before vs 22797±2470 pmol/1×120 min after operation) and to intraduodenal fat solution (19595±2121 pmol/1×120 min vs 19983±2031 pmol/1×120 min). Also, no significant differences were measured in CCK release (491±71 pmol/1×120 min vs 430±57 pmol/1×120 min for amino acids, 571=63 pmol/1×120 min vs 563±89 pmol/1×120 min for fat solution). Plasma PP and CCK levels were compared by linear regression analysis. Correlations between PP and CCK were high in the intact pancreas (amino acids,r=0.92; fat,r=0.99) as well as in the denervated pancreas (r=0.93 amino acids andr=0.98 fat). These results show that extrinsic pancreatic innervation does not influence PP and CCK release after intraduodenal amino acids or fat solution and that PP secretion seems to be mediated to some extent through the release of CCK.     

Respiratory variations in aortic blood flow predict fluid responsiveness in ventilated children

Objective

To investigate whether respiratory variations in aortic blood flow velocity (ΔVpeak ao), systolic arterial pressure (ΔPS) and pulse pressure (ΔPP) could accurately predict fluid responsiveness in ventilated children.

Design and setting

Prospective study in a 18-bed pediatric intensive care unit.

Patients

Twenty-six children [median age 28.5 (16–44) months] with preserved left ventricular (LV) function.

Intervention

Standardized volume expansion (VE).

Measurements and main results

Analysis of aortic blood flow by transthoracic pulsed-Doppler allowed LV stroke volume measurement and on-line ΔVpeak ao calculation. The VE-induced increase in LV stroke volume was >?15% in 18 patients (responders) and p?=?0.001], whereas ΔPP and ΔPS did not significantly differ between groups. The prediction of fluid responsiveness was higher with ΔVpeak ao [ROC curve area 0.85 (95% IC 0.99–1.8), p?=?0.001] than with ΔPS (0.64) or ΔPP (0.59). The best cut-off for ΔVpeak ao was 12%, with sensitivity, specificity, and positive and negative predictive values of 81.2%, 85.7%, 93% and 66.6%, respectively. A positive linear correlation was found between baseline ΔVpeak ao and VE-induced gain in stroke volume (rho?=?0.68, p?=?0.001).

Conclusions

While respiratory variations in aortic blood flow velocity measured by pulsed Doppler before VE accurately predict the effects of VE, ΔPS and ΔPP are of little value in ventilated children.

     

Carotid–Femoral Pulse Wave Velocity Assessed by Ultrasound: A Study with Echotracking Technology

Described here is a new method for determination of carotid–femoral pulse wave velocity (PWV) based on arterial diameter waveform recording by an ultrasound system. The study was carried out on 120 consecutive patients. Carotid–femoral PWV was determined using a tonometric technique (PWVpp, PulsePen, DiaTecne, Milan, Italy) and an echotracking ultrasound system (PWVet, E-Track, Aloka, Tokyo, Japan). The relationship between PWVpp and PWVet was evaluated by linear regression and Bland–Altman analysis. There was excellent agreement between PWVet and PWVpp (Pearson's r = 0.94, 95% confidence interval: 0.91–0.96, p < 0.0001; PWVet = 0.88 × PWVpp + 0.57). The Bland–Altman plot revealed an offset of ?0.33 m/s with limits of agreement from ?2.21 to 1.54 m/s. The coefficients of variation for within-subject repeatability between PWVet and PWVpp had were 5.79% and 8.47%, respectively, without significant differences in the Bland–Altman analysis. The results suggest that echotracking technology can provide a reliable estimate of aortic stiffness comparable to that of the tonometric techniques.     

Quantification of aortic stiffness in stroke patients using 4D flow MRI in comparison with transesophageal echocardiography

To quantify stiffness of the descending aorta (DAo) in stroke patients using 4D flow MRI and compare results with transesophageal echocardiography (TEE). 48 acute stroke patients undergoing 4D flow MRI and TEE were included. Intima-media-thickness (IMT) was measured in the DAo and the aorta was scrutinized for atherosclerotic plaques using TEE. Stiffness of the DAo was determined by (a) 4D flow MRI at 3 T by calculating pulse wave velocity (PWV) and by (b) TEE calculating arterial strain, stiffness index, and distensibility coefficient. Mean IMT was 1.43?±?1.75. 7 (14.6%) subjects had no sign of atherosclerosis, 10 (20.8%) had IMT-thickening or plaques?<?4 mm, and 31 (66.7%) had at least one large and/or complex plaque in the aorta. Increased IMT significantly correlated (p?<?0.001) with increased DAo stiffness in MRI (PWV r?=?0.66) and in TEE (strain r?=?0.57, stiffness index r?=?0.64, distensibility coefficient r?=?0.57). Patients with at least IMT-thickening had significantly higher stiffness values compared to patients without atherosclerosis. However, no difference was observed between patients with plaques?<?4 mm and patients with plaques?≥?4 mm. PWV and TEE parameters of stiffness correlated significantly [strain (r?=???0.36; p?=?0.011), stiffness index (r?=?0.51; p?=?0.002), and distensibility coefficient (r?=???0.59; p?<?0.001)]. 4D flow MRI and TEE-based parameters of aortic stiffness were associated with markers of atherosclerosis such as IMT-thickness and presence of plaques. We believe that 4D flow MRI is a promising tool for future studies of aortic atherosclerosis, due to its longer coverage of the aorta and non-invasiveness.     

In Vivo Comparison of Pulse Wave Velocity Estimation Based on Ultrafast Plane Wave Imaging and High-Frame-Rate Focused Transmissions

Ultrasound-based local pulse wave velocity (PWV) estimation, as a measure of arterial stiffness, can be based on fast focused imaging (FFI) or plane wave imaging (PWI). This study was aimed at comparing the accuracy of in vivo PWV estimation using FFI and PWI. Ultrasound radiofrequency data of carotid arteries were acquired in 14 healthy volunteers (25–57 y) by executing the FFI (12 lines, 7200 Hz) and PWI (128 lines, 2000 Hz) methods consecutively. PWV was derived at two time-reference points, dicrotic notch (DN) and systolic foot (SF), for multiple pressure cycles by fitting a linear function through the positions of the peaks of low-pass filtered wall acceleration curves as a function of time. The accuracy of PWV estimation was determined for various cutoff frequencies (10–200 Hz). No statistically significant difference was observed between PWVs estimated by both approaches. The PWV and R² at DN were higher, on average, than those at SF (PWV/R²: FFI SF 5.5/0.92, FFI DN 6.1/0.92; PWI SF 5.4/0.89, PWI DN 6.3/0.95). The use of cutoff frequencies between 40 and 80 Hz provided the most accurate PWVs. Both methods seemed equally suitable for use in clinical practice, although we have a preference for the PWV at DN given the higher R² values.     

Associations of Renal Augmented Velocity Index with Arterial Stiffness,Carotid Intima–Media Thickness and Blood Pressure,in Comparison with Renal Resistive Index

The augmented velocity index (Avi) is a new Doppler index associated with arterial stiffness. We examined associations of renal Avi with blood pressure (BP), aortic stiffness and carotid intima–media thickness (IMT), and compared its performance with that of resistive index (RI). One hundred forty-seven volunteers were recruited. Renal Avi had significant positive correlations with systolic BP (r = 0.37, p < 0.001), diastolic BP (r = 0.2, p = 0.016), mean arterial pressure (r = 0.29, p < 0.001), pulse pressure (r = 0.31, p < 0.001), carotid–femoral pulse wave velocity (r = 0.49, p < 0.001) and carotid IMT (r = 0.23, p = 0.005). RI correlated positively with pulse pressure (r = 0.3, p < 0.001) only. After adjustments for co-variables, the associations remained similar. Patients with abnormal BP values (≥130/80 mm Hg), IMT and aortic stiffness (≥1 standard deviation of mean value) had higher Avi than those with normal values, but not RI. In conclusion, renal Avi had stronger associations with BP, arterial stiffness and carotid IMT than RI in apparently healthy volunteers, and was significantly increased in abnormal patients.     

Arterial Stiffness Is Inversely Related to Plasma Adiponectin Levels in Young Normotensive Patients With Type 1 Diabetes

OBJECTIVE

This study investigated the association between arterial stiffness and plasma adiponectin in patients with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Participants were normotensive patients with type 1 diabetes who were up to age 40 years. Subjects on statins with macrovascular disease or overt nephropathy were excluded. Large artery stiffness was assessed by measurement of carotid-femoral pulse wave velocity (PWV), whereas plasma adiponectin was measured by radioimmunoassay.

RESULTS

Data from 80 patients (age 27.1 ± 6.1 years, BMI 24.2 ± 3.1 kg/m², HbA_1c 7.5 ± 1.6%, 39 men, adiponectin 13.9 ± 6.7 μg/mL, and PWV 5.6 ± 0.9 m/s) were analyzed. Log adiponectin inversely correlated with age-adjusted PWV (r = −0.291, P = 0.009) and waist circumference (r = −0.427, P < 0.001). In a fully adjusted model, age, expiration/inspiration index, and log adiponectin were independently associated with PWV, explaining 39.6% of its variance.

CONCLUSIONS

Arterial stiffness is inversely related to adiponectin concentration in young patients with type 1 diabetes without major complications.Arterial stiffness, an independent predictor of total and cardiovascular mortality, can be assessed noninvasively by measurement of pulse wave velocity (PWV) (1), which is increased at early stages of type 1 diabetes (2,3). Plasma adiponectin, an adipocytokine with insulin-sensitizing, antiatherogenic, and anti-inflammatory properties (4), is high in patients with type 1 diabetes (5,6). Although adiponectin is inversely related to arterial stiffness in subjects with essential hypertension (7,8), no adiponectin-PWV relationship has been shown in children/adolescents with type 1 diabetes (9). This study investigated the association between adiponectin and PWV in young adults with type 1 diabetes.     

Pulse oximeter plethysmograph variation and its relationship to the arterial waveform in mechanically ventilated children

The variations induced by mechanical ventilation in the arterial pulse pressure and pulse oximeter plethysmograph waveforms have been shown to correlate closely and be effective in adults as markers of volume responsiveness. The aims of our study were to investigate: (1) the feasibility of recording plethysmograph indices; and (2) the relationship between pulse pressure variation (ΔPP), plethysmograph variation (ΔPOP) and plethysmograph variability index (PVI) in a diverse group of mechanically ventilated children. A prospective, observational study was performed. Mechanically ventilated children less than 11 years of age, with arterial catheters, were enrolled during the course of their clinical care in the operating room or in the pediatric intensive care unit. Real time monitor waveforms and trend data were recorded. ΔPP and ΔPOP were manually calculated and the relationships between ΔPP, ΔPOP and PVI were compared using Bland-Altman analysis and Pearson correlations. Forty-nine children were recruited; four (8%) subjects were excluded due to poor quality of the plethysmograph waveforms. ΔPP and ΔPOP demonstrated a strong correlation (r = 0.8439, P < 0.0001) and close agreement (Bias = 1.44 ± 6.4%). PVI was found to correlate strongly with ΔPP (r = 0.7049, P < 0.0001) and ΔPOP (r = 0.715, P < 0.0001). This study demonstrates the feasibility of obtaining plethysmographic variability indices in children under various physiological stresses. These data show a similarly strong correlation to that described in adults, between the variations induced by mechanical ventilation in arterial pulse pressure and the pulse oximeter plethysmograph.