Pulse pressure response to the strain of the valsalva maneuver in humans with preserved systolic function

Additive influence of exercise pressor reflex activation on Valsalva responses in white and black adults

AIM

This study aimed to determine if activation of the exercise pressor reflex exerts additive or redundant influences on the autonomic responses to the Valsalva maneuver (VL), and if these responses differ between White and Black or African American (B/AA) individuals.

METHODS

Twenty participants (B/AA n = 10, White n = 10) performed three separate experimental trials. In the first trial, participants performed two VLs in a resting condition. In a second trial, participants performed 5 min of continuous handgrip (HG) exercise at 35% of the predetermined maximal voluntary contraction. In a third and final trial, participants repeated the 5-min bout of HG while also performing two VLs during the 4th and 5th minutes. Beat by beat blood pressure and heart rate (HR) were recorded continuously and the absolute systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), pulse pressure (PP), and heart rate (HR) responses were reported for phases I-IV of each VL.

RESULTS

No significant group by trial interactions or main effects of group were observed for any phase of the VL (all p ≥ 0.36). However, significant main effects of time were observed for blood pressure and heart rate during phases IIa-IV (all p ≤ 0.02). Specifically, the addition of HG exercise exaggerated the hypertensive responses during phases IIb and IV (all p ≤ 0.04) and blunted the hypotensive responses during phases IIa and III (all p ≤ 0.01).

CONCLUSIONS

These results suggest that activation of the exercise pressor reflex exerts an additive influence on autonomic responses to the VL maneuver in both White and B/AA adults.

Time-Controlled Adaptive Ventilation Does Not Induce Hemodynamic Impairment in a Swine ARDS Model

Background

The current standard of care during severe acute respiratory distress syndrome (ARDS) is based on low tidal volume (VT) ventilation, at 6 mL/kg of predicted body weight. The time-controlled adaptive ventilation (TCAV) is an alternative strategy, based on specific settings of the airway pressure release ventilation (APRV) mode. Briefly, TCAV reduces lung injury, including: (1) an improvement in alveolar recruitment and homogeneity; (2) reduction in alveolar and alveolar duct micro-strain and stress-risers. TCAV can result in higher intra-thoracic pressures and thus impair hemodynamics resulting from heart-lung interactions. The objective of our study was to compare hemodynamics between TCAV and conventional protective ventilation in a porcine ARDS model.

Methods

In 10 pigs (63–73 kg), lung injury was induced by repeated bronchial saline lavages followed by 2 h of injurious ventilation. The animals were then randomized into two groups: (1) Conventional protective ventilation with a VT of 6 mL/kg and PEEP adjusted to a plateau pressure set between 28 and 30 cmH₂O; (2) TCAV group with P-high set between 27 and 29 cmH₂O, P-low at 0 cmH₂O, T-low adjusted to terminate at 75% of the expiratory flow peak, and T-high at 3–4 s, with I:E > 6:1.

Results

Both lung elastance and PaO₂:FiO₂ were consistent with severe ARDS after 2 h of injurious mechanical ventilation. There was no significant difference in systemic arterial blood pressure, pulmonary blood pressure or cardiac output between Conventional protective ventilation and TCAV. Levels of total PEEP were significantly higher in the TCAV group (p < 0.05). Driving pressure and lung elastance were significantly lower in the TCAV group (p < 0.05).

Conclusion

No hemodynamic adverse events were observed in the TCAV group compared as to the standard protective ventilation group in this swine ARDS model, and TCAV appeared to be beneficial to the respiratory system.

Value of DYnamicVariation of impedance cardiac output in the diagnosis of heart failure in emergency department patients with undifferentiated dyspnea

AIM OF STUDY

Cardiac output (CO) responses to acute changes in body position and Valsalva maneuver (VM) were proposed to assess cardiac contractile reserve. We investigated the value of sitting position (SP), leg raising (LR), and VM for identifying heart failure (HF) in patients with undifferentiated dyspnea.

MATERIALS AND METHODS

It is a prospective study including patients over 18 years old admitted to the emergency department (ED) for dyspnea. Bioimpedance CO was measured at baseline, under SP, LR, and VM. HF diagnosis was based on clinical assessment, serum levels of brain natriuretic peptide (BNP) and echocardiography findings. Study population was divided into patients with heart failure (HF group) and patients without HF (non-HF group). Diagnostic performance of CO change under the three maneuvers was calculated by sensitivity, specificity, likelihood ratio and receiver operating characteristic (ROC) curve.

RESULTS

290 patients were enrolled in the study. The final diagnosis was dyspnea due to congestive heart failure in 147 patients (50.7%). CO change with VM was the most accurate exam in identifying congestive heart failure as the cause of dyspnea with a sensitivity, specificity, positive and negative likelihood ratios of 79%, 60%, 1.97, and 0.36 respectively. Area under ROC curve was 0.62(95% CI, 0.55-0.69), 0.63(95% CI, 0.56-0.69), and 0.70(95% CI, 0.64-0.76) respectively for SP, LR, and VM. In a multivariate analysis, CO change with VM, but not with SP or LR, carried independent diagnostic value (p < 0.001).

CONCLUSION

the diagnosis of HF can be aided with use of analyzing the effect of VM on non-invasively measured CO among patients admitted to the ED with undifferentiated dyspnea. Diagnostic yield of SP and LR was poor.

The Valsalva manoeuvre: physiology and clinical examples

The Valsalva manoeuvre (VM), a forced expiratory effort against a closed airway, has a wide range of applications in several medical disciplines, including diagnosing heart problems or autonomic nervous system deficiencies. The changes of the intrathoracic and intra-abdominal pressure associated with the manoeuvre result in a complex cardiovascular response with a concomitant action of several regulatory mechanisms. As the main aim of the reflex mechanisms is to control the arterial blood pressure (BP), their action is based primarily on signals from baroreceptors, although they also reflect the activity of pulmonary stretch receptors and, to a lower degree, chemoreceptors, with different mechanisms acting either in synergism or in antagonism depending on the phase of the manoeuvre. A variety of abnormal responses to the VM can be seen in patients with different conditions. Based on the arterial BP and heart rate changes during and after the manoeuvre several dysfunctions can be hence diagnosed or confirmed. The nature of the cardiovascular response to the manoeuvre depends, however, not only on the shape of the cardiovascular system and the autonomic function of the given patient, but also on a number of technical factors related to the execution of the manoeuvre including the duration and level of strain, the body position or breathing pattern. This review of the literature provides a comprehensive analysis of the physiology and pathophysiology of the VM and an overview of its applications. A number of clinical examples of normal and abnormal haemodynamic response to the manoeuvre have been also provided.

Optimizing measures of HIV-associated neuropathy

INTRODUCTION

Distal symmetric polyneuropathy (DSP) is common in HIV and is associated with autonomic impairment. However tools to measure HIV-DSP do not include autonomic indices. We sought to optimize the Total Neuropathy Score (TNS) and the Composite Autonomic Severity Score (CASS) for use in HIV.

METHODS

HIV-infected adults (n = 102) underwent neurologic examination, quantitative sensory testing (QST), nerve conduction studies, and autonomic testing. Modifications of the TNS and CASS were assessed for validity based on correlation with the original measure and internal consistency.

RESULTS

The TNS version commonly used in HIV-DSP is valid, but it is improved by elimination of QST and addition of autonomic indices. A modified version of the CASS (M-CASS) which was designed for sensitivity to milder impairment was also valid.

CONCLUSIONS

A modified TNS that excludes QST and includes autonomic indices is optimal for HIV-DSP. The M-CASS is a valid measure of autonomic impairment in HIV.

Autonomic dysfunction is common in HIV and associated with distal symmetric polyneuropathy

Neurologic complications of HIV are well characterized in the central and peripheral nervous systems but not in the autonomic nervous system, perhaps due to the complexities of measuring autonomic function in medically ill populations. We hypothesized that autonomic dysfunction is common in HIV, can be meaningfully measured with an autonomic reflex screen, and is associated with distal symmetric polyneuropathy (DSP) but not with signs of CNS disease. We also sought to characterize immunovirologic and medical factors associated with autonomic dysfunction. We assessed 102 HIV-infected adults for autonomic dysfunction with a laboratory-based autonomic reflex screen summarized as the composite autonomic severity score (CASS). The total neuropathy score (TNS) was used to quantify DSP based on neurologic interview/examination, quantitative sensory testing, and nerve conduction studies. Autonomic dysfunction was common, with a CASS  ≥  3 in 61 % of participants, of whom 86 % were symptomatic. Greater CASS abnormalities demonstrated univariate association with increasing TNS, age, viral load, hypertension, and use of medications (particularly anticholinergics), but not with antiretrovirals, current/nadir CD(4+) count, HIV duration, metabolic factors, or signs of CNS disease. The TNS was the only significant predictor of the CASS in multivariate analysis; anticholinergic medications were marginally significant. This study demonstrates that autonomic dysfunction is common and frequently symptomatic in HIV and that an autonomic reflex screen, adjusted for anticholinergic medication, is useful in its assessment. Association of autonomic dysfunction with DSP suggests common factors in their pathogenesis, and autonomic neuropathy may be part of the spectrum of HIV-associated peripheral nerve pathologies.

Finger photoplethysmography during the Valsalva maneuver reflects left ventricular filling pressure

It is often challenging to assess cardiac filling pressure clinically. An improved system for detecting or ruling out elevated cardiac filling pressure may help reduce hospitalizations for heart failure. The blood pressure response to the Valsalva maneuver reflects left heart filling pressure, but its underuse clinically may be due in part to lack of continuous blood pressure recording along with lack of standardization of expiratory effort. In this study, we tested whether Valsalva-induced changes in the pulse amplitude of finger photoplethysmography (PPG), a technology already widely available in medical settings, correlate with invasively measured left ventricular end-diastolic pressure (LVEDP). We tested 33 subjects before clinically scheduled cardiac catheterizations. A finger photoplethysmography waveform was recorded during a Valsalva effort of 20 mmHg expiratory pressure sustained for 10 s, an effort most patients can achieve. Pulse amplitude ratio (PAR) was calculated as the PPG waveform amplitude just before release of expiratory effort divided by the waveform amplitude at baseline. PAR was well correlated with LVEDP (r = 0.68; P < 0.0001). For identifying LVEDP > 15 mmHG, PAR > 0.4 was 85% sensitive [95% confidence interval (95CI): 54-97%] and 80% specific (95CI: 56-93%). In conclusion, finger PPG, a technology already ubiquitous in medical centers, may be useful for assessing clinically meaningful categories of left heart filling pressure, using simple analysis of the waveform after a Valsalva maneuver effort that most patients can achieve.

Mechanism of loss of consciousness during vascular neck restraint

Vascular neck restraint (VNR) is a technique that police officers may employ to control combative individuals. As the mechanism of unconsciousness is not completely understood, we tested the hypothesis that VNR simply compresses the carotid arteries, thereby decreasing middle cerebral artery blood flow. Twenty-four healthy police officers (age 35 ± 4 yr) were studied. Heart rate (HR), arterial pressure, rate of change of pressure (dP/d t), and stroke volume (SV) were measured using infrared finger photoplethysmography. Bilateral mean middle cerebral artery flow velocity (MCAVmean) was measured by using transcranial Doppler ultrasound. Neck pressure was measured using flat, fluid-filled balloon transducers positioned over both carotid bifurcations. To detect ocular fixation, subjects were asked to focus on a pen that was moved from side to side. VNR was released 1–2 s after ocular fixation. Ocular fixation occurred in 16 subjects [time 9.5 ± 0.4 (SE) s]. Pressures over the right (R) and left (L) carotid arteries were 257 ± 22 and 146 ± 18 mmHg, respectively. VNR decreased MCAVmean (R 45 ± 3 to 8 ± 4 cm/s; L 53 ± 2 to 10 ± 3 cm/s) and SV (92 ± 4 to 75 ± 4 ml; P < 0.001). Mean arterial pressure (MAP), dP/d t, and HR did not change significantly. We conclude that the most important mechanism in loss of consciousness was decreased cerebral blood flow caused by carotid artery compression. The small decrease in CO (9.6 to 7.5 l/min) observed would not seem to be important as there was no change in MAP. In addition, with no significant change in HR, ventricular contractility, or MAP, the carotid sinus baroreceptor reflex appears to contribute little to the response to VNR.

Detection of elevated pulmonary capillary wedge pressure in elderly patients with various cardiac disorders by the Valsalva manoeuvre

In the present study, we assessed whether elevated (> or =15 mmHg) PCWP (pulmonary capillary wedge pressure) can be detected using the blood pressure response to the Valsalva manoeuvre in a group of elderly patients with various cardiac disorders, including atrial fibrillation and valvular heart disease, and healthy elderly controls. The Valsalva manoeuvre was performed in 93 patients (71+/-4 years) and 28 healthy controls (70+/-4 years) undergoing right-sided cardiac catheterization. Blood pressure was measured non-invasively with Finapres. PPR (pulse pressure ratio), the ratio of minimum pulse pressure during phase 2 and maximum pulse pressure during phase 1 of the Valsalva manoeuvre, was correlated with PCWP (r=0.63, P<0.001). The area under the receiver operator characteristic curve of PPR with elevated PCWP was 0.85 (P<0.001). For PPR=0.62, sensitivity for elevated PCWP was 80%, specificity was 79%, positive predictive value was 76% and negative predictive value was 83%. Correlation of PPR with PCWP and the ability of PPR to detect elevated PCWP was present in atrial fibrillation, heart failure and valvular heart disease. In conclusion, PPR is a sensitive and specific instrument to diagnose elevated PCWP non-invasively in a large group of elderly patients with various cardiac disorders. This makes the Valsalva manoeuvre a useful non-invasive tool for diagnosing heart failure, applicable in elderly patients with common cardiac disorders, such as atrial fibrillation and valvular heart disease.

Arterial stiffness following repeated Valsalva maneuvers and resistance exercise in young men

The purpose of this study was to compare arterial stiffness after a bout of resistance exercise (RE) and an experimental condition consisting of repeated Valsalva maneuvers (VMs). Fourteen male participants randomly completed a lower-body, unilateral RE bout and a VM bout designed to alter blood pressure (BP) in a similar pulsatile fashion. Pulse-wave velocity (PWV, measured in metres per second (m.s-1)) was used to measure central and peripheral arterial stiffness and was assessed before and 20 min after each perturbation. Beat-to-beat blood pressure (BP) was assessed during bouts using finger plethysmography. Change in systolic BP, diastolic BP, mean arterial pressure, and pulse pressure were similar during both bouts. Central PWV increased after repeated VMs (7.1 +/- 0.3 m/s to 7.8 +/- 0.3 m/s), but not after RE (7.2 +/- 0.3 m/s to 7.2 +/- 0.3 m/s) (interaction, p = 0.032). There was no change in peripheral PWV after VM (8.9 +/- 0.3 m/s to 9.3 +/- 0.3 m/s) or RE (8.5 +/- 0.2 m/s to 8.4 +/- 0.2 m/s). Arterial stiffness increased after repeated VM. Even though presented with a similar BP load, arterial stiffness did not increase after acute RE. These findings suggest a role for VM in acutely altering arterial properties.

Normal values of pulmonary capillary wedge pressure and the blood pressure response to the Valsalva manoeuvre in healthy elderly subjects

The blood pressure response to the Valsalva manoeuvre is related to pulmonary capillary wedge pressure (PCWP) and can be used to diagnose heart failure. However, this has never been studied specifically in the elderly, in whom the prevalence of heart failure is highest. Furthermore, normal values of the Valsalva manoeuvre are lacking. We aimed to obtain normal values of PCWP and the blood pressure response to the Valsalva manoeuvre in elderly subjects. Therefore, 28 healthy subjects, aged 70 +/- 4 years, performed Valsalva manoeuvres before and after anti-G garment inflation, which was used for temporary increase of PCWP. Before inflation, PCWP was 9.8 +/- 1.9 mmHg in supine and 8.9 +/- 2.1 in semi-recumbent position. From the blood pressure response, measured with Finapres, the systolic blood pressure ratio (SBPR), pulse pressure ratio (PPR), stroke volume ratio (SVR) and heart rate ratio (HRR) were calculated. In supine position, SBPR was 0.76 +/- 0.11, PPR 0.51 +/- 0.16, SVR 0.42 +/- 0.11, and HRR 1.17 +/- 0.12. Semi-recumbently, SBPR was 0.74 +/- 0.10, PPR 0.46 +/- 0.14, SVR 0.41 +/- 0.10, and HRR 1.24 +/- 0.23. After inflation of the anti-G garment, the areas under the Receiver Operator Characteristics curves of SBPR, PPR and SVR for elevated (> or = 15 mmHg) PCWP were >0.85 in supine position. In conclusion, this is the first study to obtain normal values of the blood pressure response to the Valsalva manoeuvre and PCWP in healthy elderly subjects, which is essential for the interpretation of patient data. The Valsalva manoeuvre showed significant discriminatory power in the detection of elevated PCWP, which underscores its potential in the non-invasive diagnosis of heart failure.

Aortic pulse waveforms for evaluating cardiac performance in the human fetus

Pulse waveforms of the fetal descending aorta were obtained using an echo-tracking system to clarify the gestational age-related changes and the usefulness for detecting cardiac dysfunction. Peak systolic (PSD) and end diastolic diameter (EDD), pulse amplitude (Amp) and Amp:EDD ratio, calculated from the pulse waveforms, were adopted for analysis. In 196 normal fetuses after 20 weeks, the PSD, EDD and Amp increased, and Amp:EDD ratio decreased linearly with advancing gestation. The 19 fetuses with suspected cardiac dysfunction were divided into healthy and altered cardiac function subgroups, according to the values of fractional shortening and preload index. Of these, 7 fetuses with cardiac dysfunction had significantly higher incidence of low Amp (p < 0.01) and Amp:EDD ratio (p < 0.001) than remaining 12 fetuses with normal cardiac function. The pulse waveform analysis in the fetal descending aorta proved useful for detecting fetal cardiac dysfunction in utero.

Autonomic function in elderly patients with chronic heart failure

AIMS

Autonomic function (AF) is attenuated by heart failure (HF). Reports have been based on studies of young patients with systolic heart failure (SHF). However, HF is a disease of older patients who are more likely to have diastolic heart failure (DHF). We investigated whether age alters AF in elderly HF patients and whether the haemodynamic type of HF influences AF.

METHOD AND RESULTS

Thirty-six elderly HF (Framingham criteria) patients (11 with SHF, 25 with DHF) and 21 matched healthy subjects underwent simple bedside AF tests. Compared with the reference values for healthy adults, the mean E:I ratios and the median 30:15 ratios standing were all essentially normal. The median 30:15 ratios tilt and the mean Valsalva ratios were all significantly below the reference value (P for all cases <<0.050). Comparing three groups, there were no significant differences for mean E:I ratio (P=0.111), 30:15 tilt (P=0.619) and 30:15 standing (P=0.167), whereas there were significant differences for the mean Valsalva ratios (P=0.001). The mean Valsalva ratio of the SHF patients was significantly lower than that for the DHF patients (P<0.001) which in turn was significantly lower than the result of the healthy subjects (P<0.001).

CONCLUSION

There is an age-related impairment in AF with further impairment occurring in patients with HF. However, the severity of autonomic dysfunction is less in patients with DHF compared with patients with SHF.