Respiratory Variation Research Articles

Influence of fasting duration on blood volume status of pediatric patients evaluated by ultrasonic technique

Objective: To evaluate the influence of preoperative fasting duration on blood volume status of pediatric patients during induction based on ultrasonic technique. Methods: One hundred and ten pediatric patients, scheduled for elective operation in the Second Affiliated Hospital & Yuying Children's Hospital, were recruited during January and October in 2018. After sedation by inhalation of sevoflurane, the maximum (expiratory) and minimum (inspiratory) diameter of inferior vena cava (IVC(max), IVC(min)) and aorta velocity-time integral (VTI) in apical five-chamber cardiac view were measured with an ultrasound machine. Respiratory variabilities of these parameters were further calculated. Furthermore, passive leg raising (PLR) test was performed and above measurements/calculations were repeated. The correlation between the duration of fasting and IVC respiratory variations index (IVC(RVI)) or aortic VTI variability (ΔVTI) was then analyzed. Results: Before PLR, IVC(max), IVC(min) and IVC(RVI) were (0.78±0.19), (0.43±0.15) cm and 0.45±0.12, respectively. After PLR, IVC(max) and IVC(min) increased to (0.94±0.20), (0.55±0.18) cm, while IVC(RVI) decreased to 0.42±0.13, the differences were statistically significant (t=15.66, 10.85, 3.14, all P<0.05). However, IVC(max), IVC(min) and IVC(RVI) were not significantly correlated with the duration of fasting analyzed by linear regression (before PLR: r=0.052, 0.163, 0.171; after PLR, r=0.062, 0.169, 0.165, all P>0.05). Before PLR, expiratory aortic VTI (VTI(max)), inspiratory aortic VTI (VTI(min)) and ΔVTI were 21±5, 17±4 and 17±8, respectively. After PLR, the VTI(max) and VTI(min) significantly increased to 23±5 and 19±4 (t=13.60, 10.43, all P<0.05), but ΔVTI was not changed significantly, which was 17±8(t=0.34, P>0.05). Linear regression analysis showed that VTI(max), VTI(min) and ΔVTI were not significantly correlated with the duration of fasting (before PLR: r=0.111, 0.100, 0.047; after PLR: r=0.003, 0.033, 0.073, all P>0.05). Further multiple linear regression analysis indicated that, age and body weight were independent factors influencing IVC(RVI) and ΔVTI before and after PLR (IVC(RVI): β=-0.441, 0.515, -0.451, 0.507; ΔVTI: β=-0.442, 0.545, -2.422, 2.850; all P<0.05). However, the duration of fasting was not correlated with IVC(RVI) and ΔVTI after adjusting the age and weight (IVC(RVI): β=0.177, 0.160; ΔVTI: β=0.037, 0.054; all P>0.05). Conclusion: Age and weight, but not preoperative fasting duration, are correlated with respiratory variabilities of inferior vena cava diameter and aortic VTI in pediatric patients.

Interchangeability between Respiratory Variations of Subclavian Vein and Pulse Pressure Variation in Ventilated Patients in the Operating Room.

ObjectiveFor mechanically ventilated patients, the best predictors of fluid responsiveness are dynamic parameters. Many methods that reflect cardiopulmonary interactions have been proposed to evaluate the preload dependency. In this study, we describe the interchangeability between respiratory variations of the subclavian (ΔSCV) vein and pulse pressure variation (PPV) in sedated and mechanically ventilated patients benefiting from kidney transplantation.MethodsThe ΔSCV via infraclavicular transthoracic echocardiography and PPV measurements were recorded simultaneously by a single operator. The Bland–Altman method assessed the interchangeability between ΔSCV and PPV.ResultsA total of 27 patients were prospectively included in the study. The Bland–Altman analysis showed a bias of +1.6 % for ΔSCV measurements vs. PPV. The limit of agreements was, respectively, −4% and 8%. The agreement between PPV >13% and ΔSCV >13% was 100%, and the agreement between PPV<9% and ΔSCV<9% was 58%. No misclassification (PPV<9% [0%] and PPV>13% [0%]) was observed.ConclusionΔSCV and PPV are interchangeable when assessing preload dependency in mechanically ventilated patients benefiting from kidney transplantation. ΔSCV appears to be a suitable tool because it is non-invasive, simple, easy and almost always available.

Abstract 16347: Simplified Workflow to Improve the Precision of Non-invasive Radio-ablation of Ventricular Tachycardia Storm

Background: Stereotactic ablative radiotherapy (SAbR) is an emerging therapy for ventricular tachycardia (VT) storm, but the feasibility and outcomes guided by computational 12-lead ECG mapping and respiratory-gated radiation delivery have not been reported. Hypothesis: We hypothesized that a novel 12-lead ECG-based mapping system and respiratory-gated radiotherapy delivery may simplify the workflow and improve precision of SAbR in critically ill patients with VT storm. Methods: We enrolled patients with VT storm who were not candidates for catheter ablation. VT was induced using non-invasive stimulation and recorded on 12-lead ECGs. Computational ECG mapping was performed to localize VT exit sites. Target volumes were contoured onto an averaged free-breathing CT. Ionizing radiation (25 Gy) was delivered using a linear accelerator (Varian, Palo Alto). In patients with significant respiratory motion, radiotherapy was delivered at end-expiration, guided by ICD lead fiducials. Results: In 5 patients (age 74±6.1 years, EF 29±14%) refractory to 2±1 ablation procedures, 1.5±0.6 VT morphologies were localized on 3D models (Fig 1A) using ECG-based mapping (mapping time 1.2±0.3 min). In patients whom respiratory gating (Fig 1B) was used prospectively due to respiratory variation, the planned target volume (PTV) was smaller compared to patients who were not gated (71 ± 7 vs 153 ± 35 cc, p&lt;0.01). These patients also had VT targets (crux or inferior LV) close to the stomach, and did not experience adverse events. ICD shocks were decreased after SAbR compared to before (0.25±0.5 vs 26±19 shocks, p&lt;0.001) at 4.4±3.4 months follow-up. Conclusion: Non-invasive computational mapping based upon the 12-lead ECG alone simplifies radioablation workflow in critically ill VT storm patients and reduces the burden of ICD shocks. Respiratory gated radiotherapy ablation appears feasible and may help reduce target volume of therapy. Studies with longer follow-up are ongoing.

Prediction of fluid responsiveness using lung recruitment manoeuvre in paediatric patients receiving lung-protective ventilation: A prospective observational study.

Pressure-based dynamic variables are poor predictors of fluid responsiveness in children, and their predictability is expected to reduce further during lung-protective ventilation with a low tidal volume. We hypothesised that lung recruitment manoeuvre (LRM)-induced changes in dynamic variables improve their ability to predict fluid responsiveness in children. Prospective observational study. Tertiary care children's hospital, single-centre study performed from June 2017 to May 2019. We included patients less than 7 years of age undergoing cardiac surgery. Neonates and patients with pulmonary hypertension, significant dysrhythmia, ventricular ejection fraction of less than 30% or pulmonary disease were excluded. All patients were provided with lung-protective volume-controlled ventilation (tidal volume 6 ml kg-1, positive end-expiratory pressure 6 cmH2O). A LRM was applied with a continuous inspiratory pressure of 25 cmH2O for 20 s. The ability of dynamic variables to predict fluid responsiveness was evaluated by the area under the receiver operating characteristic curve [area under the curve (AUC)]. Fluid responsiveness was defined as an increase in the cardiac index by more than 15% with crystalloid administration (10 ml kg-1). Thirty patients were included in the final analysis, of whom 19 were responders. The baseline pleth variability index (PVI) (AUC 0.794, 95% confidence interval 0.608 to 0.919, P < 0.001) and LRM-induced PVI (AUC 0.711, 95% confidence interval 0.517 to 0.861, P = 0.026) could predict fluid responsiveness. The respiratory variation of pulse oximetry photoplethysmographic waveform and pulse pressure variation did not predict fluid responsiveness regardless of the LRM. The PVI is effective in predicting fluid responsiveness in paediatric patients with lung-protective ventilation regardless of a LRM. However, the LRM did not improve the ability of the other dynamic variables to predict fluid responsiveness in these patients. www.clinicaltrials.gov identifier: NCT03184961.

Comparison of Respiratory Variations of Subclavian Vein and Inferior Vena Cava in Hospitalized Patients with Kidney Disease.

BackgroundAccurate assessment of relative intravascular volume is critical for appropriate volume management of patients with kidney disease. Respiratory variations of inferior vena cava (IVC) diameter have been used and may correlate with those of subclavian vein (SCV) by bedside ultrasound. The purpose of this study was to assess the relationship between SCV and IVC respiratory variations by bedside ultrasound in a large group of hospitalized patients with acute and/or chronic kidney disease.MethodsWe compared 160 paired SCV and IVC bedside ultrasound studies from 102 semi-recumbent hospitalized adult patients with kidney disease. Patient encounters in which the SCV or IVC could not be clearly visualized were excluded. Collapsibility index=(Dmax–Dmin)/Dmax*100%; D=venous diameter.ResultsRelationships between SCV collapsibility index and IVC collapsibility index were not different for longitudinal and transverse views of the SCV. Correlation of SCV collapsibility index with IVC collapsibility index was 0.75 for mechanical ventilation (n=65, P<0.0001) and 0.67 for spontaneous breathing (n=95, P<0.0001). IVC collapsibility index cut-offs <20% for hypervolemia and >50% for hypovolemia corresponded to SCV collapsibility index cut-offs of <22% and >39%, respectively, for both mechanical ventilation and spontaneous breathing encounters. Using these cut-offs for SCV collapsibilities, assessment as hypervolemia versus not-hypervolemia had maximal sensitivity and specificity for predicting respective IVC collapsibility cut-offs of 88% for mechanical ventilation and 74% for spontaneous breathing, and assessment as hypovolemia versus not-hypovolemia had maximal sensitivity and specificity of 91% and 70%, respectively. Concordance, defined as agreement between assessment using SCV CI and assessment using IVC CI, was 85% for mechanical ventilation and 72% for spontaneous breathing when differentiating hypervolemia versus not-hypervolemia and was 89% and 71% respectively when differentiating hypovolemia versus not-hypovolemia.ConclusionAssessment using SCV collapsibility index in the semi-recumbent position has a reasonable concordance with assessment using IVC collapsibility index for both spontaneous breathing and mechanical ventilation, in a wide range of hospitalized patients with concurrent kidney disease, and may be a useful adjunct to assess relative intravascular volume in patients with kidney disease.

Reconstruction of respiratory variation signals from fMRI data

Functional MRI signals can be heavily influenced by systemic physiological processes in addition to local neural activity. For example, widespread hemodynamic fluctuations across the brain have been found to correlate with natural, low-frequency variations in the depth and rate of breathing over time. Acquiring peripheral measures of respiration during fMRI scanning not only allows for modeling such effects in fMRI analysis, but also provides valuable information for interrogating brain-body physiology. However, physiological recordings are frequently unavailable or have insufficient quality. Here, we propose a computational technique for reconstructing continuous low-frequency respiration volume (RV) fluctuations from fMRI data alone. We evaluate the performance of this approach across different fMRI preprocessing strategies. Further, we demonstrate that the predicted RV signals can account for similar patterns of temporal variation in resting-state fMRI data compared to measured RV fluctuations. These findings indicate that fluctuations in respiration volume can be extracted from fMRI alone, in the common scenario of missing or corrupted respiration recordings. The results have implications for enriching a large volume of existing fMRI datasets through retrospective addition of respiratory variations information.

Baclofen destabilises breathing during sleep in healthy humans: A randomised, controlled, double-blind crossover trial.

Periodic breathing is frequent in patients with severe heart failure. Apart from being an indicator of severity, periodic breathing has its own deleterious consequences (sleep-related oxygen desaturations, sleep fragmentation), which justifies attempts to correct it irrespective of the underlying disease. Animal models and human data suggest that baclofen can reconfigure respiratory central pattern generators. We hypothesised that baclofen, a GABAB agonist, may thus be able to correct periodic breathing in humans. Healthy volunteers were exposed to hypoxia during sleep. Participants who developed periodic breathing (n = 14 [53 screened]) were randomly assigned to double-blind oral baclofen (progressively increased to 60 mg/d) or placebo. The primary outcome was the coefficient of variation (CoVar) of respiratory cycle total time considered as an indicator of breathing irregularity. Secondary outcomes included the CoVar of tidal volume, apnoea-hypopnoea index, sleep fragmentation index and ventilatory complexity (noise limit). The analysis was conducted in 9 subjects after exclusion of incomplete datasets. CoVar of respiratory cycle total time significantly increased with baclofen during non-rapid eye movement sleep (median with placebo 56.00% [37.63-78.95]; baclofen 85.42% [68.37-86.40], P = .020; significant difference during the N1-N2 phases of sleep but not during the N3 phase). CoVar of tidal volume significantly increased during N1-N2 sleep. The apnoea-hypopnoea index, sleep fragmentation index and ventilatory complexity were not significantly different between placebo and baclofen. Baclofen did not stabilise breathing in our model. On the contrary, it increased respiratory variability. Baclofen should probably not be used in patients with or at risk of periodic breathing.

Predicting nasal high-flow therapy failure by pediatric respiratory rate-oxygenation index and pediatric respiratory rate-oxygenation index variation in children.

The primary objective of this study was to evaluate whether pediatric respiratory rate-oxygenation index (p-ROXI) and variation in p-ROXI (p-ROXV) can serve as objective markers in children with high-flow nasal cannula (HFNC) failure. In this prospective, single-center observational study, all patients who received HFNC therapy in the general pediatrics ward, pediatric intensive care unit, and the pediatric emergency department were included. High-flow nasal cannula success was achieved for 116 (88.5%) patients. At 24h, if both p-ROXI and p-ROXV values were above the cutoff point (≥ 66.7 and ≥ 24.0, respectively), HFNC failure was 1.9% and 40.6% if both were below their values (p < 0.001). At 48h of HFNC initiation, if both p-ROXI and p-ROXV values were above the cutoff point (≥ 65.1 and ≥ 24.6, respectively), HFNC failure was 0.0%; if both were below these values, HFNC failure was 100% (p < 0.001).Conclusion: We observed that these parameters can be used as good markers in pediatric clinics to predict the risk of HFNC failure in patients with acute respiratory failure. What is Known: • Optimal timing for transitions between invasive and noninvasive ventilation strategies is of significant importance. • The complexity of data requires an objective marker that can be evaluated quickly and easily at the patient's bedside for predicting HFNC failure in children with acute respiratory failure. What is New: • Our data showed that combining p-ROXI and p-ROXV can be successful in predicting HFNC failure at 24 and 48h of therapy.

Pulmonary Artery Wedge Pressure Respiratory Variation Increases With Sodium Nitroprusside Vasodilator Challenge

BackgroundThe physiologic factors leading to pulmonary arterial wedge pressure respiratory variation (PAWPvar) are underexplored. We hypothesized that PAWPvar is associated with baseline PAWP and would predict response to sodium nitroprusside (SNP). Methods and ResultsWe performed a retrospective study of right heart catheterization studies in 51 subjects with SNP challenge at our institution from 2012 to 2019. PAWPvar was defined as expiratory minus inspiratory PAWP. Baseline %PAWPvar was inversely correlated with baseline PAWP (R = –0.5). SNP administration led to increased %PAWPvar (+27%, P < .01). Subjects with low baseline PAWPvar (less than the median) had an increase in PAWPvar with SNP (3 ± 4 mm Hg), whereas those with a high baseline PAWPvar (greater than the median) did not (–0.6 ± 4 mm Hg, P = .003). Those who had a greater than the median PAWPvar increase with SNP had greater cardiac output augmentation compared with those who had less than a median increase in PAWPvar (1.7 ± 1.5 L/min vs 0.9 ± 0.7 L/min, P = .02). An increasing PAWPvar after SNP was associated with significant discrepancy in the number of subjects achieving transplant-acceptable pulmonary vascular resistance (<2.5 Wood units) when calculated by expiratory versus mean PAWP (37 vs 27 subjects, 20% discrepancy rate). Subjects with a higher PAWPvar after SNP were more likely to demonstrate discrepant transplant-acceptable pulmonary vascular resistance calculations comparing expiratory versus mean PAWP than those with lower PAWPvar post-SNP (47% vs 13%, odds ratio 5.5, P = .03). ConclusionsOur findings indicate that PAWPvar is a meaningful physiologic parameter that is influenced by the compliance of the left heart/pulmonary vascular system and its relative preload and afterload states.

Potential SCG Predictors of Heart Failure Readmission

Introduction Recent advances in sensor technology, digital processing and artificial intelligence can be used to potentially increase the utility of seismocardiography (SCG) for ambulatory assessment of heart failure (HF) patients. SCG respiratory variability, energy spectrum shifts to ultra-low frequencies, third heart sound amplitude and other features may provide early warning of HF deterioration. If these non-invasively detected changes prove to be reliable, then earlier intervention may reduce readmissions, costs, and perhaps morbidity and mortality. Objective The objective of this study was to investigate early SCG waveform features that may be predictive of HF re-admission. Methods SCG was longitudinally followed in 40 HF patients, 9 (23%) of whom were readmitted during the study period (median follow-up 1.5 mos). SCG waveforms were clustered into two groups (that correlate with respiration) using unsupervised machine learning. Following this, various signal features were calculated using digital signal processing including waveform respiratory variability, sub-audible spectral energy distribution, and SCG3 (“S3”) amplitude. Results Similar to prior observations with heart rate variability, the intra group SCG variability tended to decrease as the patient approached re-admission (table below). The energy ratio between the ultra-low frequency band (0.5-5 Hz) and the broader sub-audible frequency band (0.5-15 Hz) showed a shift towards the lower frequencies as the subjects approached re-admission. In addition, SCG3 amplitude (which corresponds to S3) appeared to increase as the subjects approached readmission. Conclusions We report preliminary data showing some SCG features that appeared to be early predictors of HF readmission. Features included Intra-group variability, along with the SCG downward frequency shifts and increased SCG3 amplitude Ongoing work will help to better characterize and validate these initial observations

Optimizing Our Patients' Entropy Production as Therapy? Hypotheses Originating from the Physics of Physiology.

Understanding how nature drives entropy production offers novel insights regarding patient care. Whilst energy is always preserved and energy gradients irreversibly dissipate (thus producing entropy), increasing evidence suggests that they do so in the most optimal means possible. For living complex non-equilibrium systems to create a healthy internal emergent order, they must continuously produce entropy over time. The Maximum Entropy Production Principle (MEPP) highlights nature’s drive for non-equilibrium systems to augment their entropy production if possible. This physical drive is hypothesized to be responsible for the spontaneous formation of fractal structures in space (e.g., multi-scale self-similar tree-like vascular structures that optimize delivery to and clearance from an organ system) and time (e.g., complex heart and respiratory rate variability); both are ubiquitous and essential for physiology and health. Second, human entropy production, measured by heat production divided by temperature, is hypothesized to relate to both metabolism and consciousness, dissipating oxidative energy gradients and reducing information into meaning and memory, respectively. Third, both MEPP and natural selection are hypothesized to drive enhanced functioning and adaptability, selecting states with robust basilar entropy production, as well as the capacity to enhance entropy production in response to exercise, heat stress, and illness. Finally, a targeted focus on optimizing our patients’ entropy production has the potential to improve health and clinical outcomes. With the implications of developing a novel understanding of health, illness, and treatment strategies, further exploration of this uncharted ground will offer value.

Ultrasonography in the Critical Care Unit.

Purpose of ReviewThis article summarizes the utility and evidence supporting the use of ultrasound exams in the intensive care unit.Recent FindingsPoint-of-care ultrasonography (POCUS) is widely used by intensivists managing critically ill patients whereby they can accurately and rapidly assess for many pathologies such as pneumothorax, pulmonary edema, hydronephrosis, hemoperitoneum, and deep vein thrombosis among others. Basic and advanced critical care echocardiography, including transesophageal echocardiography, are routinely performed to determine the etiology of hemodynamic instability in undifferentiated shock and to guide subsequent therapy. The use of POCUS in the assessment of volume status is controversial with studies demonstrating that respiratory variation of the IVC is not reliable and with analysis of aortic blood flow velocity after passive leg raising maneuvers being the most promising.SummaryPoint-of-care ultrasonography allows frontline clinicians to make real-time diagnoses and treatment decisions. This article will provide the reader with a broad overview of this important topic.Electronic supplementary materialThe online version of this article (10.1007/s11886-020-01393-z) contains supplementary material, which is available to authorized users.

Music performance anxiety from the challenge and threat perspective: psychophysiological and performance outcomes

BackgroundAlthough many musicians perceive music performance anxiety (MPA) as a significant problem, studies about the psychobiological and performance-related concomitants of MPA are limited. Using the biopsychosocial model of challenge and threat as theoretical framework, we aim to investigate whether musicians’ changes in their psychobiological responses and performance quality from a private to a public performance are moderated by their general MPA level. According to the challenge and threat framework, individuals are in a threat state when the perceived demands of a performance situation outweigh the perceived resources, whereas they are in a challenge state when the perceived resources outweigh the perceived demands. The resources-demands differential (resources minus demands) and the cardiovascular challenge-threat index (sum of cardiac output and reverse scored total peripheral resistance) are the main indices of these states. We postulate that the relationship between general MPA level and performance quality is mediated by these challenge and threat measures.MethodsWe will test 100 university music students reporting general MPA levels ranging from low to high. They will perform privately (i.e., without audience) and publicly (i.e., with an audience) on two separate days in counterbalanced order. During each performance session, we will record their cardiovascular and respiratory activity and collect saliva samples and self-reported measures. Measures of primary interest are self-reported anxiety, the resources-demands differential, the cardiovascular challenge-threat index, sigh rate, total respiratory variability, partial pressure of end-tidal carbon dioxide and the salivary biomarkers cortisol, dehydroepiandrosterone, and alpha-amylase. Both, the participants and anonymous experts will evaluate the performance quality from audio recordings.DiscussionThe results of the planned project are expected to contribute to a more comprehensive understanding of the psychobiology of MPA and of the processes that influence musicians’ individual reactions to performance situations. We also anticipate the findings of this project to have important implications for the development and implementation of theory-based interventions aimed at managing musicians’ anxiety and improving performance quality. Thanks to the use of multimethod approaches incorporating psychobiology, it might be possible to better assess the progress and success of interventions and ultimately improve musicians’ chance to have a successful professional career.Trial registrationNot applicable.

High Breath-by-Breath Variability Is Associated With Extubation Failure in Children.

Extubation failure is multifactorial, and most tools to assess extubation readiness only evaluate snapshots of patient physiology. Understanding variability in respiratory variables may provide additional information to inform extubation readiness assessments. Secondary analysis of prospectively collected physiologic data of children just prior to extubation during a spontaneous breathing trial. Physiologic data were cleaned to provide 40 consecutive breaths and calculate variability terms, coefficient of variation and autocorrelation, in commonly used respiratory variables (i.e., tidal volume, minute ventilation, and respiratory rate). Other clinical variables included diagnostic and demographic data, median values of respiratory variables during spontaneous breathing trials, and the change in airway pressure during an occlusion maneuver to measure respiratory muscle strength (maximal change in airway pressure generated during airway occlusion [PiMax]). Multivariable models evaluated independent associations with reintubation and prolonged use of noninvasive respiratory support after extubation. Acute care, children's hospital. Children were included from the pediatric and cardiothoracic ICUs who were greater than 37 weeks gestational age up to and including 18 years who were intubated greater than or equal to 12 hours with planned extubation. We excluded children who had a contraindication to an esophageal catheter or respiratory inductance plethysmography bands. Noninterventional study. A total of 371 children were included, 32 of them were reintubated. Many variability terms were associated with reintubation, including coefficient of variation and autocorrelation of the respiratory rate. After controlling for confounding variables such as age and neurologic diagnosis, both coefficient of variation of respiratory rate(p < 0.001) and low PiMax (p = 0.002) retained an independent association with reintubation. Children with either low PiMax or high coefficient of variation of respiratory rate had a nearly three-fold higher risk of extubation failure, and when these children developed postextubation upper airway obstruction, reintubation rates were greater than 30%. High respiratory variability during spontaneous breathing trials is independently associated with extubation failure in children, with very high rates of extubation failure when these children develop postextubation upper airway obstruction.

Subcostal versus transhepatic view to assess the inferior vena cava in critically ill patients.

Evaluation of the inferior vena cava (IVC) is not always possible through the subcostal (SC) window. Inferior vena cava diameters measured by transhepatic (TH) and SC views were compared by Bland and Altman analysis. 131 patients were enrolled, including 88 (67%) under mechanical ventilation. The echogenicity was statistically poorer through the TH view in comparison with the SC view (P=.002). The correlation between the SC and TH views was good and better for respiratory variation than for end-expiratory or end-inspiratory diameter measurements (r=0.86). Despite low bias, the limits of agreement were wide (-7.5 and 7.7mm for end-expiratory diameter, -8.7 and 8.5mm for end-inspiratory diameter, and -5.3 and 5.8mm for respiratory variation). Complementary analysis showed that the concordance between the SC and the TH views was better when the IVC was distended. However, the limits of agreement remained broad. Although feasible in almost all patients, the TH view does not provide better echogenicity in comparison with the SC view. Despite a good correlation with the SC view and a low bias, the limits of agreement were wide, especially when the IVC has an ellipsoidal shape, suggesting caution in the interpretation of data obtained by the TH view.

A RARE CASE OF CARDIAC TAMPONADE DUE TO RIFAMPICIN-RESISTANT TUBERCULOSIS: A REAL DIAGNOSTIC AND THERAPEUTIC CHALLENGE

Pericarditis is a rare manifestation of tuberculosis. We report here the case of a 35-year-old woman admitted to clinical tamponade. The echocardiogram revealed a pericardial effusion of great circumferential abundance with significant respiratory variations and a bilateral pleural effusion of average abundance on chest radiography. The patient underwent emergency pericardial drainage. The initial tuberculosis assessment was negative. The culture of the liquid returned positive at 8 days revealing rifampicin-resistant tuberculosis (RR-TB).Therefore, examination of the pericardial fluid is useful in the diagnosis of tuberculous pericarditis. This case was considered TB-RR. The patient was put on a special treatment regimen after consensus, with good clinical improvement. Pericardial tuberculosis remains a rare disease. It is important to consider it as an etiological diagnosis, especially in endemic countries because it has a poor therapeutic prognosis. Early diagnosis would allow better management of these cases in order to limit cases of resistance.

Comparative effects of neurally adjusted ventilatory assist and variable pressure support on lung and diaphragmatic function in a model of acute respiratory distress syndrome: A randomised animal study.

Variable assisted mechanical ventilation has been shown to improve lung function and reduce lung injury. However, differences between extrinsic and intrinsic variability are unknown. To investigate the effects of neurally adjusted ventilatory assist (NAVA, intrinsic variability), variable pressure support ventilation (Noisy PSV, extrinsic variability) and conventional pressure-controlled ventilation (PCV) on lung and diaphragmatic function and damage in experimental acute respiratory distress syndrome (ARDS). Randomised controlled animal study. University Hospital Research Facility. A total of 24 juvenile female pigs. ARDS was induced by repetitive lung lavage and injurious ventilation. Animals were randomly assigned to 24 h of either: 1) NAVA, 2) Noisy PSV or 3) PCV (n=8 per group). Mechanical ventilation settings followed the ARDS Network recommendations. The primary outcome was histological lung damage. Secondary outcomes were respiratory variables and patterns, subject-ventilator asynchrony (SVA), pulmonary and diaphragmatic biomarkers, as well as diaphragmatic muscle atrophy and myosin isotypes. Global alveolar damage did not differ between groups, but NAVA resulted in less interstitial oedema in dorsal lung regions than Noisy PSV. Gas exchange and SVA incidence did not differ between groups. Compared with Noisy PSV, NAVA generated higher coefficients of variation of tidal volume and respiratory rate. During NAVA, only 40.4% of breaths were triggered by the electrical diaphragm signal. The IL-8 concentration in lung tissue was lower after NAVA compared with PCV and Noisy PSV, whereas Noisy PSV yielded lower type III procollagen mRNA expression than NAVA and PCV. Diaphragmatic muscle fibre diameters were smaller after PCV compared with assisted modes, whereas expression of myosin isotypes did not differ between groups. Noisy PSV and NAVA did not reduce global lung injury compared with PCV but affected different biomarkers and attenuated diaphragmatic atrophy. NAVA increased the respiratory variability; however, NAVA yielded a similar SVA incidence as Noisy PSV. This trial was registered and approved by the Landesdirektion Dresden, Germany (AZ 24-9168.11-1/2012-2).

Cardiorespiratory and Vascular Variability Analysis to Classify Patients with Ischemic and Dilated Cardiomyopathy.

Heart diseases are the leading cause of death in developed countries. Ascertaining the etiology of cardiomyopathies is still a challenge. The objective of this study was to classify cardiomyopathy patients through cardio, respiratory and vascular variability analysis, considering the vascular activity as the input and output of the baroreflex response. Forty-one cardiomyopathy patients (CMP) classified as ischemic (ICM, 24 patients) and dilated (DCM, 17 patients) were analyzed. Thirty-nine elderly control subjects (CON) were used as reference. From the electrocardiographic, respiratory flow, and blood pressure signals, following temporal series were extracted: beat-to-beat intervals (BBI), total respiratory cycle time series (TT), and end- systolic (SBP) and diastolic (DBP) blood pressure amplitudes, respectively. Three-dimensional representation of the cardiorespiratory and vascular activities was characterized geometrically, by fitting a polygon that contains 95% of data, and by statistical descriptive indices. The best classifiers were used to build support vector machine models. The optimal model to classify ICM versus DCM patients achieved 92.7% accuracy, 94.1% sensitivity, and 91.7% specificity. When comparing CMP patients and CON subjects, the best model achieved 86.2% accuracy, 82.9% sensitivity, and 89.7% specificity. These results suggest a limited ability of cardiac and respiratory systems response to regulate the vascular variability in these patients.

Respiratory Variation in Carotid Artery Peak Systolic Velocity Is Unable to Predict Fluid Responsiveness in Spontaneously Breathing Critically Ill Patients When Assessed by Novice Physician Sonologists.

Respiratory variation in carotid artery peak systolic velocity (ΔVpeak) assessed by point-of-care ultrasound (POCUS) has been proposed as a noninvasive means to predict fluid responsiveness. We aimed to evaluate the ability of carotid ΔVpeak as assessed by novice physician sonologists to predict fluid responsiveness. This study was conducted in 2 intensive care units. Spontaneously breathing, nonintubated patients with signs of volume depletion were included. Patients with atrial fibrillation/flutter, cardiogenic, obstructive or neurogenic shock, or those for whom further intravenous (IV) fluid administration would be harmful were excluded. Three novice physician sonologists were trained in POCUS assessment of carotid ΔVpeak. They assessed the carotid ΔVpeak in study participants prior to the administration of a 500 mL IV fluid bolus. Fluid responsiveness was defined as a ≥10% increase in cardiac index as measured using bioreactance. Eighty-six participants were enrolled, 50 (58.1%) were fluid responders. Carotid ΔVpeak performed poorly at predicting fluid responsiveness. Test characteristics for the optimum carotid ΔVpeak of 8.0% were: area under the receiver operating curve = 0.61 (95% CI: 0.48-0.73), sensitivity = 72.0% (95% CI: 58.3-82.56), specificity = 50.0% (95% CI: 34.5-65.5). Novice physician sonologists using POCUS are unable to predict fluid responsiveness using carotid ΔVpeak. Until further research identifies key limiting factors, clinicians should use caution directing IV fluid resuscitation using carotid ΔVpeak.

A Potential Utility of Pulsed-Wave Doppler in Iliocaval Outflow Obstruction

Proximal venous outflow obstruction (PVOO) in the iliocaval veins is frequently suspected after history and physical examination. A simple, noninvasive test that can indicate if PVOO is present, prior to more invasive imaging, would be very helpful but is currently unavailable. We undertook this study to determine if pulsed-wave Doppler (PW) can signify PVOO. PW is known to indicate proximal occlusion when it does not exhibit any respiratory variations. Does PW exhibit any clues when the proximal vein is stenotic but not occluded?