Comparison of caries diagnostic modalities: A clinical study in 40 subjects.

BACKGROUND AND OBJECTIVES: Few studies have been published that evaluate the usefulness of different caries- diagnostic modalities in general dental practice. The goal of this study was to compare the results of screening for coronal dental caries in a general dental practice using clinical observations, radiographs, laser fluorescence (DIAGNOdent™) (LF), and optical coherence tomography (OCT). Diagnostic agreement between OCT and LF versus standard clinical techniques for detecting caries was determined in 40 subjects. STUDY DESIGNS/MATERIALS AND METHODS: Forty patients with >1 coronal carious lesion as determined by prescreening using clinical examination and radiographs were enrolled in this study. Subjects with gross caries were excluded. Subsequently each patient underwent a full detailed dental examination by an experienced clinician, using visual examination and radiographs according to standard clinical practice. The coronal surfaces of a total of 932 teeth were examined and charted. Teeth were then photographed, rediagnosed using the LF system, and imaged using OCT. Two blinded pre-standardized examiners reviewed radiographic and OCT images and assigned caries status. RESULTS: Based on manufacturer's cutoff values, sensitivity and specificity for coronal caries using LF technique (i) on unaltered tooth surfaces were 73.7% and 94.1%, respectively and (ii) in previously restored or sealed teeth, they were 19.2% and 95.8%, respectively. LF technique was unable to assess tissue health underneath sealants and restorations. Clinician agreement (kappa [k]) regarding caries diagnosis using OCT imaging was overall 0.834 (SE = 0.034). Sensitivity and specificity for caries using OCT technique (i) on unaltered tooth surfaces approximated 74.1% and 95.7%, respectively and, (ii) in previously restored or sealed teeth, they approximated 76.0% and 95.6%, respectively. Although OCT was able to detect lesions beneath many resin restorations and sealants, results varied considerably between materials. OCT imaging was unable to detect caries when caries was >2 mm below the tooth surface. CONCLUSION: These findings support the usefulness of LF for primary caries detection, and the clinical utility of OCT for early caries detection and monitoring under dental resin restorations and sealants. Lasers Surg. Med. 48:924-928, 2016. © 2016 Wiley Periodicals, Inc.

Does diving affect the hearing of Asian military divers? A study in the Republic of Singapore Navy.

OBJECTIVE: This study examined whether military diving during a National Serviceman's two-year term of service affected his hearing threshold levels. METHODS: A retrospective cohort study was designed to examine the hearing thresholds of divers (mean age 20.9 years) who enlisted between 2001 and 2010 (n = 748). Their pre-enlistment and pre-discharge audiograms were collected. All made dives using scuba dive sets, averaged 200 dives over two years and depths of 30 meters of sea water/msw or less. RESULTS: The divers' hearing levels in the left ear were not affected except for a marginal decrease in hearing level at the 2kHz level. There was a marginal decrease in hearing level in 0.5, 1 and 2 kHz in the right ear. These changes are physiologically insignificant. There were more low-frequency (0.5, 1 and 2 kHz) changes compared to high-frequency (4 and 8 kHz) changes in both ears, with a larger number of changes noted in the right ear, as compared to the left. However, no diver had a hearing threshold increase greater than 20dB or exceeded the hearing threshold levels required of military divers. CONCLUSION: There was no decrease of clinical significance in hearing function of the Republic of Singapore Navy national serviceman naval divers after diving for two years.

Impact of Brewers' Spent Grain-Containing Biscuit on Postprandial Glycaemic Response in Individuals with Metabolic Syndrome: A Crossover Randomised Controlled Trial.

Brewers' spent grain (BSG) is a fibre and protein-rich by-product of beer-brewing. Fermenting BSG with Rhizopus oligosporus can further increase its content of soluble fibre, protein and certain antioxidants. Since nutrients rich in BSG can improve postprandial glycaemic response, this study assessed the postprandial glucose response (PPGR) and postprandial insulin response (PPIR) controlling effect of consuming 30% wheat flour substituted biscuits with autoclaved BSG (ABSG) or fermented BSG (FBSG) in individuals with metabolic syndrome (MetS). The effect on postprandial lipid panel, breath hydrogen (H2) and methane (CH4) concentration and subjective appetite response was also examined. Fifteen subjects with MetS participated in this crossover randomised controlled trial, and blood was collected at 9 time-points for 4 h after consumption of control biscuits (Control), ABSG and FBSG. A significant interaction effect was observed (Pinteraction = 0.013) for the glucose time-points concentration. At 180 min, the glucose concentration was lowered after the consumption of ABSG (p = 0.010) and FBSG (p = 0.012) compared to the Control. Moreover, the FBSG resulted in a significantly lower glucose incremental area under curve (iAUC) compared to the Control (p = 0.028). Insulin level was also lowered at 180 min after the ABSG (p = 0.010) and FBSG (p = 0.051) consumption compared to the Control. However, no difference was noted for postprandial lipid panel, breath H2 and CH4 concentration and subjective appetite response. In conclusion, the consumption of BSG-incorporated biscuits can attenuate PPGR, and fermented BSG incorporation conferred a further PPGR controlling benefit.

Estimation of cardiac output and systemic vascular resistance using a multivariate regression model with features selected from the finger photoplethysmogram and routine cardiovascular measurements.

BACKGROUND: Cardiac output (CO) and systemic vascular resistance (SVR) are two important parameters of the cardiovascular system. The ability to measure these parameters continuously and noninvasively may assist in diagnosing and monitoring patients with suspected cardiovascular diseases, or other critical illnesses. In this study, a method is proposed to estimate both the CO and SVR of a heterogeneous cohort of intensive care unit patients (N=48). METHODS: Spectral and morphological features were extracted from the finger photoplethysmogram, and added to heart rate and mean arterial pressure as input features to a multivariate regression model to estimate CO and SVR. A stepwise feature search algorithm was employed to select statistically significant features. Leave-one-out cross validation was used to assess the generalized model performance. The degree of agreement between the estimation method and the gold standard was assessed using Bland-Altman analysis. RESULTS: The Bland-Altman bias ±precision (1.96 times standard deviation) for CO was -0.01 ±2.70 L min-1 when only photoplethysmogram (PPG) features were used, and for SVR was -0.87 ±412 dyn.s.cm-5 when only one PPG variability feature was used. CONCLUSIONS: These promising results indicate the feasibility of using the method described as a non-invasive preliminary diagnostic tool in supervised or unsupervised clinical settings.

Regular Consumption of Biovalorized Okara-Containing Biscuit Improves Circulating Short-Chain Fatty Acids and Fecal Bile Acids Concentrations by Modulating the Gut Microbiome: A Randomized Controlled Crossover Trial.

SCOPE: Okara is a fiber-rich food by-product whereby biovalorization with Rhizopus oligosporus can improve its nutritional quality, generating fermentable substrates for improved gut health maintenance. This study evaluates the impact of okara- and biovalorized okara-containing biscuits consumption on gut health in Singapore adults. METHODS AND RESULTS: Participants consume control (C), 20% flour-substituted okara (AOK), and 20% flour-substituted biovalorized okara (RO) biscuits for three weeks, with assessment of gut metabolites, microbiome, and dietary intake. Fecal valeric acid is significantly higher with RO compared to AOK (p = 0.005). RO and AOK have significantly higher total serum short-chain fatty acids (p = 0.002 and 0.018 respectively) and acetic acid (p = 0.007 and 0.030 respectively) compared to C. Higher serum propionic acid (p = 0.004) and lower fecal lithocholic acid (p = 0.009) are observed with RO. Although serum zonulin shows no significant difference amongst interventions, AOK reduces Clostridiales while RO increases Bifidobacterium. CONCLUSION: Okara consumption improves serum SCFA regardless of fermentation while biovalorized okara further enhances gut metabolites by modulating gut microbiome.

Spontaneous fluctuations in the peripheral photoplethysmographic waveform: roles of arterial pressure and muscle sympathetic nerve activity.

Assessment of spontaneous slow waves in the peripheral blood volume using the photoplethysmogram (PPG) has shown potential clinical value, but the physiological correlates of these fluctuations have not been fully elucidated. This study addressed the contribution of arterial pressure and muscle sympathetic nerve activity (MSNA) in beat-to-beat PPG variability in resting humans under spontaneous breathing conditions. Peripheral PPG waveforms were measured from the fingertip, earlobe, and toe in young and healthy individuals (n = 13), together with the arterial pressure waveform, electrocardiogram, respiration, and direct measurement of MSNA by microneurography. Cross-spectral coherence analysis revealed that among the PPG waveforms, low-frequency fluctuations (0.04-0.15 Hz) in the ear PPG had the highest coherence with arterial pressure (0.71 ± 0.15) and MSNA (0.44 ± 0.18, with a peak of 0.71 ± 0.16 at 0.10 ± 0.03 Hz). The normalized midfrequency powers (0.08-0.15 Hz), with an emphasis on the 0.1-Hz region, were positively correlated between MSNA and the ear PPG (r = 0.77, P = 0.002). Finger and toe PPGs had lower coherence with arterial pressure (0.35 ± 0.10 and 0.30 ± 0.11, respectively) and MSNA (0.33 ± 0.10 and 0.26 ± 0.10, respectively) in the LF band but displayed higher coherence between themselves (0.54 ± 0.09) compared with the ear (P < 0.001), which may suggest the dominance of regional vasomotor activities and a common sympathetic influence in the glabrous skin. These findings highlight the differential mechanisms governing PPG waveform fluctuations across different body sites. Spontaneous PPG variability in the ear includes a major contribution from arterial pressure and MSNA, which may provide a rationale for its clinical utility.

Determinants of human cerebral pressure-flow velocity relationships: new insights from vascular modelling and Ca²âº channel blockade.

The fundamental determinants of human dynamic cerebral autoregulation are poorly understood, particularly the role of vascular compliance and the myogenic response. We sought to 1) determine whether capacitive blood flow associated with vascular compliance and driven by the rate of change in mean arterial blood pressure (dMAP/dt) is an important determinant of middle cerebral artery velocity (MCAv) dynamics and 2) characterise the impact of myogenic blockade on these cerebral pressure-flow velocity relations in humans. We measured MCAv and mean arterial pressure (MAP) during oscillatory lower body negative pressure (n =8) at 0.10 and 0.05 Hz before and after cerebral Ca²âº channel blockade (nimodipine). Pressure-flow velocity relationships were characterised using transfer function analysis and a regression-based Windkessel analysis that incorporates MAP and dMAP/dt as predictors of MCAv dynamics. Results show that incorporation of dMAP/dt accounted for more MCAv variance (R² 0.80-0.99) than if only MAP was considered (R2 0.05-0.90). The capacitive gain relating dMAP/dt and MCAv was strongly correlated to transfer function gain (0.05 Hz, r =0.93, P<0.01; 0.10 Hz, r =0.91, P<0.01), but not to phase or coherence. Ca²âº channel blockade increased the conductive gain relation between MAP and MCAv (P<0.05), and reduced phase at 0.05 Hz (P<0.01). Capacitive and transfer function gain were unaltered. The findings suggest capacitive blood flow is an important determinant of cerebral haemodynamics that bears strong relations to some metrics of dynamic cerebral autoregulation derived from transfer function analysis, and that Ca²âº channel blockade enhances pressure-driven resistive blood flow but does not alter capacitive blood flow. the causes and effects of cerebrovascular diseases such as stroke and dementia.

The effect of Ventricular Assist Devices on cerebral autoregulation: A preliminary study.

BACKGROUND: The insertion of Ventricular Assist Devices is a common strategy for cardiovascular support in patients with refractory cardiogenic shock. This study sought to determine the impact of ventricular assist devices on the dynamic relationship between arterial blood pressure and cerebral blood flow velocity. METHODS: A sample of 5 patients supported with a pulsatile ventricular assist device was compared with 5 control patients. Controls were matched for age, co-morbidities, current diagnosis and cardiac output state, to cases. Beat-to-beat recordings of mean arterial pressure and cerebral blood flow velocity, using transcranial Doppler were obtained. Transfer function analysis was performed on the lowpass filtered pressure and flow signals, to assess gain, phase and coherence of the relationship between mean arterial blood pressure and cerebral blood flow velocity. These parameters were derived from the very low frequency (0.02-0.07 Hz), low frequency (0.07-0.2 Hz) and high frequency (0.2-0.35 Hz). RESULTS: No significant difference was found in gain and phase values between the two groups, but the low frequency coherence was significantly higher in cases compared with controls (mean ± SD: 0.65 ± 0.16 vs 0.38 ± 0.19, P = 0.04). The two cases with highest coherence (~0.8) also had much higher spectral power in mean arterial blood pressure. CONCLUSIONS: Pulsatile ventricular assist devices affect the coherence but not the gain or phase of the cerebral pressure-flow relationship in the low frequency range; thus whether there was any significant disruption of cerebral autoregulation mechanism was not exactly clear. The augmentation of input pressure fluctuations might contribute in part to the higher coherence observed.

Electrocardiographic and Echocardiographic Insights From a Prospective Registry of Asian Elite Athletes.

Background: Asian representation in sport is increasing, yet there remains a lack of reference values for the Asian athlete's heart. Consequently, current guidelines for cardiovascular screening recommend using Caucasian athletes' norms to evaluate Asian athletes. This study aims to outline electrocardiographic and echocardiographic characteristics of the Asian athlete's heart using a Singaporean prospective registry of Southeast (SE) Asian athletes. Methods and Results: One hundred and fifty elite athletes, mean age of 26.1 ± 5.7 years (50% males, 88% Chinese), were evaluated using a questionnaire, 12-lead electrocardiogram (ECG) and transthoracic echocardiogram. All ECGs were analyzed using the 2017 International Recommendations. Echocardiographic data were presented by gender and sporting discipline. The prevalence of abnormal ECGs among SE Asian athletes was 6.7%-higher than reported figures for Caucasian athletes. The abnormal ECGs comprised mainly anterior T wave inversions (ATWI) beyond lead V2, predominantly in female athletes from mixed/endurance sport (9.3% prevalence amongst females). None had echocardiographic structural abnormalities. Male athletes had reduced global longitudinal strain compared to females (-18.7 ± 1.6 vs. -20.7 ± 2.1%, p < 0.001). Overall, SE Asian athletes had smaller left ventricular cavity sizes and wall thickness compared to non-Asian athletes. Conclusion: SE Asian athletes have higher abnormal ECG rates compared to Caucasian athletes, and also demonstrate structural differences that should be accounted for when interpreting their echocardiograms compared to athletes of other ethnicities.

Asian Pacific Society of Cardiology Consensus Recommendations for Pre-participation Screening in Young Competitive Athletes.

Sports-related sudden cardiac death is a rare but devastating consequence of sports participation. Certain pathologies underlying sports-related sudden cardiac death could have been picked up pre-participation and the affected athletes advised on appropriate preventive measures and/or suitability for training or competition. However, mass screening efforts - especially in healthy young populations - are fraught with challenges, most notably the need to balance scarce medical resources and sustainability of such screening programmes, in healthcare systems that are already stretched. Given the rising trend of young sports participants across the Asia-Pacific region, the working group of the Asian Pacific Society of Cardiology (APSC) developed a sports classification system that incorporates dynamic and static components of various sports, with deliberate integration of sports events unique to the Asia-Pacific region. The APSC expert panel reviewed and appraised using the Grading of Recommendations Assessment, Development, and Evaluation system. Consensus recommendations were developed, which were then put to an online vote. Consensus was reached when 80% of votes for a recommendation were agree or neutral. The resulting statements described here provide guidance on the need for cardiovascular pre-participation screening for young competitive athletes based on the intensity of sports they engage in.

Assessing the human cardiovascular response to moderate exercise: feature extraction by support vector regression.

This study aims to quantitatively describe the steady-state relationships among percentage changes in key central cardiovascular variables (i.e. stroke volume, heart rate (HR), total peripheral resistance and cardiac output), measured using non-invasive means, in response to moderate exercise, and the oxygen uptake rate, using a new nonlinear regression approach-support vector regression. Ten untrained normal males exercised in an upright position on an electronically braked cycle ergometer with constant workloads ranging from 25 W to 125 W. Throughout the experiment, VO(2) was determined breath by breath and the HR was monitored beat by beat. During the last minute of each exercise session, the cardiac output was measured beat by beat using a novel non-invasive ultrasound-based device and blood pressure was measured using a tonometric measurement device. Based on the analysis of experimental data, nonlinear steady-state relationships between key central cardiovascular variables and VO(2) were qualitatively observed except for the HR which increased linearly as a function of increasing VO(2). Quantitative descriptions of these complex nonlinear behaviour were provided by nonparametric models which were obtained by using support vector regression.

Detecting change in left ventricular ejection time during head-up tilt-induced progressive central hypovolemia using a finger photoplethysmographic pulse oximetry wave form.

BACKGROUND: Change in cardiac preload caused by mild hypovolemia can alter left ventricular ejection time (LVET) without noticeable change in blood pressure (BP). Previously our group has explored a novel method of LVET monitoring using a noninvasive finger photoplethysmographic pulse oximetry wave form. The current study investigated the ability of photoplethysmographic pulse oximetry wave form-derived LVET (LVETp) to identify progressive central hypovolemia induced by head-up tilt and evaluated the potential use of LVETp as an early noninvasive indicator of blood loss. METHODS: Thirteen healthy subjects underwent graded head-up tilt from 0 degrees to 80 degrees. The response of LVETp to tilt was compared with that of interbeat heart interval (RR) and BP. Least-squares linear regression analysis was performed on an intrasubject basis between various physiologic variables and sine of the tilt angle (which is associated with the decrease in central blood volume). RESULTS: During graded tilt, LVETp had a very strong negative linear correlation with sine of the tilt angle, with correlation coefficients (r) ranging from -0.961 to -0.985. At a very mild hypovolemic state (10 degrees), there was a significant decrease in LVETp compared with baseline (0 degrees) but without a significant change in RR and BP. Gradient analysis showed that LVETp was sensitive to central volume loss at all volume states (0 degrees-80 degrees), whereas RR was only responsive at mild-to-moderate and moderate hypovolemic states (20 degrees-80 degrees) but not mild hypovolemic state (0 degrees-20 degrees). CONCLUSIONS: LVETp has a strong association with the change in central blood volume and may be a sensitive early marker of nonhypotensive progressive central hypovolemia. Joint interpretation of LVETp and RR trends may help to characterize the extent of blood volume loss.

Automatic detection of left ventricular ejection time from a finger photoplethysmographic pulse oximetry waveform: comparison with Doppler aortic measurement.

Left ventricular ejection time (LVET) is a useful measure of ventricular performance and preload. The present study explores a novel method of continuous LVET monitoring using a noninvasive finger photoplethysmographic pulse oximetry waveform (PPG-POW). A method for the automatic beat-to-beat detection of LVET from the finger PPG-POW is presented based on a combination of derivative analysis, waveform averaging and rule-based logic. The performance of the detection method was evaluated on 13 healthy subjects during graded head-up tilt. Overall, the correlation between the PPG-POW derived LVET and the aortic flow derived LVET was high and significant (r = 0.897, p < 0.05). The bias was -14 +/- 14 ms (mean +/- SD), and the percentage error was 9.7%. Although these results would not be sufficient to satisfy the requirement for clinical evaluation of LVET when absolute accuracy was demanded, the strong correlation between the PPG-POW LVET and the aortic LVET on an intra-subject basis (r = 0.945 +/- 0.043, mean +/- SD) would support the application of PPG-POW to detect the directional change in LVET of an individual. This could be very useful for the early identification of progressive hypovolaemia or blood loss. The present study has demonstrated a promising approach to extract potentially useful information from a noninvasive, easy-to-obtain signal that could be readily acquired either from existing patient monitoring equipment or from inexpensive instrumentation. More extensive investigation is necessary to evaluate the applicability of the present approach in clinical care monitoring.

Severe acute respiratory syndrome in a naval diver.

Severe acute respiratory syndrome (SARS) is a highly infectious, rapidly progressive, emerging disease. Early diagnosis and preventive measures are key for treatment and minimization of secondary spread. In the context of the armed forces, aggressive containment measures are essential to prevent an outbreak. In this study, we present the first reported case, to our knowledge, of SARS in a naval diver. The special physical requirements for divers and the potential complications associated with deep sea diving necessitate extensive investigation before certification of fitness for diving after SARS. In the early recovery period, potential problems during diving are caused by inadequate lung ventilation in relation to exercise level and increased breathing resistance attributable to weak respiratory muscles, with corresponding risk of hypoxia and hypercapnia, as well as decreased ability to respond to nonrespiratory problems during diving. Problems in the late recovery period include increased risk of diving complications (such as pulmonary barotrauma) resulting from fibrosis and scarring within the lung parenchyma, which are known complications of SARS. From our experience, we suggest that computed tomographic scans of the thorax, lung function tests, and careful follow-up monitoring should play a vital role in the assessment of patients during the convalescent period, before certification of fitness to dive.

Reviewing lessons learnt of SARS in Singapore during planning for influenza pandemic.

There were many lessons learnt in Singapore's fight against SARS, and they have proven to be all the more important in our preparations for an influenza pandemic. The following lessons are discussed in this paper including: the widespread ramifications among the various sectors in Singapore (individuals, organizations, community and economy), the first principles of outbreak response, need for enhanced infectious disease control measures, high demands on the healthcare system, the role of management policies implementation and dissemination, multidisciplinary involvement, importance of communication, and business continuity planning.

A comparison of motion sickness prevalence between seafarers and non-seafarers onboard naval platforms.

BACKGROUND: Motion sickness may crucially affect the operational performance of soldiers at sea and this differs between individuals and environments. OBJECTIVES: To report on the prevalence and understand the risk factors for motion sickness among Singaporean sailors (seafarers) and attached army servicemen (non-seafarers) onboard naval platforms. METHODOLOGY: Cross sectional study using self-administered survey of 503 personnel over the monsoon period from January to April 2001. RESULTS: The prevalence of motion sickness was distinctly higher in the army (59.2%) personnel compared with the navy (38.3%) over a series of sea states. The most common symptoms were headache, nausea and dizziness. The Motion Sickness Susceptibility Questionnaire was used to score susceptibility and appeared to correlate better among non-seafarers rather than seafarers. The discomfort experienced in one's environment was perceived to contribute towards onset and smoking appeared to be protective against motion sickness. Regular sailing appears to be an important factor in minimising motion sickness. CONCLUSION: While we understand motion sickness to be a continuum of physiological responses to the whole body vibration, it is especially apparent among the non-seafarers. Seafarers by themselves will become less susceptible with regular sailing and they are also more cognizant of the modalities available to alleviate symptoms.

Detrended fluctuation analysis of blood pressure in preterm infants with intraventricular hemorrhage.

Very preterm infants are at high risk of death and serious permanent brain damage, as occurs with intraventricular hemorrhage (IVH). Detrended fluctuation analysis (DFA) that quantifies the fractal correlation properties of physiological signals has been proposed as a potential method for clinical risk assessment. This study examined whether DFA of the arterial blood pressure (ABP) signal could derive markers for the identification of preterm infants who developed IVH. ABP data were recorded from a prospective cohort of 30 critically ill preterm infants in the first 1-3 h of life, 10 of which developed IVH. DFA was performed on the beat-to-beat sequences of mean arterial pressure (MAP), systolic blood pressure (SBP) and pulse interval, with short-term exponent (α1, for timescale of 4-15 beats) and long-term exponent (α2, for timescale of 15-50 beats) computed accordingly. The IVH infants were found to have higher short-term scaling exponents of both MAP and SBP (α1 = 1.06 ± 0.18 and 0.98 ± 0.20) compared to the non-IVH infants (α1 = 0.84 ± 0.25 and 0.78 ± 0.25, P = 0.017 and 0.038, respectively). The results have demonstrated that fractal dynamics embedded in the arterial pressure waveform could provide useful information that facilitates early identification of IVH in preterm infants.

A cardiovascular mathematical model of graded head-up tilt.

A lumped parameter model of the cardiovascular system has been developed and optimized using experimental data obtained from 13 healthy subjects during graded head-up tilt (HUT) from the supine position to [Formula: see text]. The model includes descriptions of the left and right heart, direct ventricular interaction through the septum and pericardium, the systemic and pulmonary circulations, nonlinear pressure volume relationship of the lower body compartment, arterial and cardiopulmonary baroreceptors, as well as autoregulatory mechanisms. A number of important features, including the separate effects of arterial and cardiopulmonary baroreflexes, and autoregulation in the lower body, as well as diastolic ventricular interaction through the pericardium have been included and tested for their significance. Furthermore, the individual effect of parameter associated with heart failure, including LV and RV contractility, baseline systemic vascular resistance, pulmonary vascular resistance, total blood volume, LV diastolic stiffness and reflex gain on HUT response have also been investigated. Our fitted model compares favorably with our experimental measurements and published literature at a range of tilt angles, in terms of both global and regional hemodynamic variables. Compared to the normal condition, a simulated congestive heart failure condition produced a blunted response to HUT with regards to the percentage changes in cardiac output, stroke volume, end diastolic volume and effector response (i.e., heart contractility, venous unstressed volume, systemic vascular resistance and heart rate) with progressive tilting.

Estimation of cardiac output and total peripheral resistance in preterm infants by arterial waveform analysis.

This study investigated whether arterial blood pressure waveform analysis could be useful for estimating left ventricular outflow (LVO) and total peripheral resistance (TPR) in preterm infants. A cohort of 27 infants were studied, with 89 measurements of left ventricular outflow (LVO) using Doppler echocardiography and arterial pressure using catheters, performed in 0, 12, 24 and 36 hours after birth. TPR was computed as mean arterial pressure divided by LVO. The diastolic decay rate (1/τ) was obtained via fitting an exponential function to the last one third of each arterial pulse, with the mean rate computed from 50 pulses selected from each infant. This decay rate was considered to be inversely related to TPR while positively related to LVO. The results of regression analysis have confirmed that the diastolic decay rate had significant positive and negative relationships with LVO and TPR respectively(r = 0.383, P = 0.0002 and r = -0.379, P = 0.0002 respectively). These preliminary results demonstrated the potential utility of arterial pressure waveform analysis for estimating LVO and TPR in preterm infants, but more advanced multi-parameter models may be needed to improve accuracy of the estimation.