Respiratory Variation Research Articles

RESPIRATORY VARIABILITY OF VALVULAR PEAK SYSTOLIC VELOCITY AS A NEW INDICATOR OF FLUID RESPONSIVENESS IN PATIENTS WITH SEPTIC SHOCK.

Objective: The aim of this study was to evaluate the reliability and feasibility of pulse Doppler measurements of peak velocity respiratory variability of mitral and tricuspid valve rings during systole as new dynamic indicators of fluid responsiveness in patients with septic shock. Methods: Transthoracic echocardiography (TTE) was performed to measure the respiratory variability of aortic velocity-time integral (∆VTI), respiratory variability of tricuspid annulus systolic peak velocity (∆RVS), respiratory variability of mitral annulus systolic peak velocity (∆LVS), and other related indicators. Fluid responsiveness was defined as a 10% increase in cardiac output after fluid expansion, assessed by TTE. Results: A total of 33 patients with septic shock were enrolled in this study. First, there was no significant difference in the population characteristics between the fluid responsiveness positive group (n = 17) and the fluid responsiveness negative group (n = 16) ( P > 0.05). Second, Pearson correlation test showed that ∆RVS, ∆LVS, and TAPSE with the relative increase in cardiac output after fluid expansion ( R = 0.55, P = 0.001; R = 0.40, P = 0.02; R = 0.36, P = 0.041). Third, multiple logistic regression analysis demonstrated that ∆RVS, ∆LVS, and TAPSE were significantly correlated with fluid responsiveness in patients with septic shock. Fourth, receiver operating characteristic (ROC) curve analysis revealed that ∆VTI, ∆LVS, ∆RVS, and TAPSE had good predictive ability for fluid responsiveness in patients with septic shock. The area under the curve (AUC) of ∆VTI, ∆LVS, ∆RVS, and TAPSE for predicting fluid responsiveness was 0.952, 0.802, 0.822, and 0.713, respectively. The sensitivity (Se) values were 1.00, 0.73, 0.81, and 0.83, whereas the specificity (Sp) values were 0.84, 0.91, 0.76, and 0.67, respectively. The optimal thresholds were 0.128, 0.129, 0.130, and 13.9 mm, respectively. Conclusion: Tissue Doppler ultrasound evaluation of respiratory variability of mitral and tricuspid annular peak systolic velocity could be a feasible and reliable method for the simple assessment of fluid responsiveness in patients with septic shock.

Rapid extraction of respiratory waveforms from photoplethysmography: A deep corr-encoder approach

Much of the information related to breathing is contained within the photoplethysmography (PPG) signal, through changes in venous blood flow, heart rate and stroke volume. We aim to leverage this fact, by employing a novel deep learning framework which is a based on a repurposed convolutional autoencoder. Our corr-encoder model aims to encode all of the relevant respiratory information contained within photoplethysmography waveform, and decode it into a waveform that is similar to a gold standard respiratory reference — the Capnogram. The model is employed on two photoplethysmography data sets, namely Capnobase and BIDMC. We show that the model is capable of producing respiratory waveforms that approach the gold standard, while in turn producing state of the art respiratory rate estimates. We also show that when it comes to capturing more advanced respiratory waveform characteristics such as duty cycle, our model is for the most part unsuccessful. A suggested reason for this, in light of a previous study on in-ear PPG, is that the respiratory variations in finger-PPG are far weaker compared with other recording locations. Importantly, our model can perform these waveform estimates in a fraction of a millisecond, giving it the capacity to produce over 6 hours of respiratory waveforms in a single second. Moreover, we attempt to interpret the behaviour of the kernel weights within the model, showing that in part our model intuitively selects different breathing frequencies. The model proposed in this work could help to improve the usefulness of consumer PPG-based wearables for medical applications, where detailed respiratory information is required.

Carotid artery corrected flow time and respiratory variation of blood flow peak velocity for prediction of hypotension after induction of general anesthesia in adult patients undergoing emergency laparotomy for peritonitis: A prospective, observational study.

Doppler waveform analysis of carotid artery has been found to predict fluid responsiveness in patients undergoing elective surgeries. We evaluated the role of carotid artery corrected flow time (FTc) and respiratory variation of blood flow peak velocity (ðVpeak) in predicting post induction hypotension in patients undergoing emergency laparotomy for peritonitis. Adult patients (n = 60) with perforation peritonitis undergoing emergency laparotomy under general anesthesia (GA) were recruited in this prospective, observational study. Carotid ultrasonography was performed pre-induction, to determine FTc and ðVpeak. Post-induction hemodynamic parameters were recorded for 5 minutes. Spearman's rank correlation coefficient was used to determine the relationship between hypotension and carotid artery measurements. Post-induction hypotension occurred in 48.3% of patients. The carotid artery FTc was significantly lower (P = 0.008) in patients who developed post-induction hypotension, but ðVpeak was statistically similar (P = 0.62) in both groups. Spearman's rank correlation coefficient revealed a statistically significant correlation between FTc and systolic blood pressure (SBP) change at one-minute post induction (r2 = -0.29, P = 0.03); however statistical significance were not achieved at 2 minutes and 3 minutes (P = 0.05 at both time points). Carotid artery FTc had an area under the receiver operating characteristic (AUROC) curve (95% CI) of 0.70 (0.57-0.84) to predict post-induction hypotension and best cutoff value of 344.8 ms with a sensitivity and specificity of 61% and 79%, respectively. Carotid artery ðVpeak had an AUROC curve (95% CI) of 0.54 (0.39-0.69) to predict post-induction hypotension and best cutoff value of 7.9% with a sensitivity and specificity of 62% and 55%, respectively. Carotid artery FTc and ðVpeak are not reasonable predictors of hypotension in patients undergoing emergency laparotomy for perforation peritonitis.

AB-453068-1 NOVEL ‘SCORE-MAPPING’ OF DIAPHRAGMATIC COMPOUND MOTOR ACTION POTENTIAL FOR EARLY DETECTION OF PHRENIC NERVE INJURY DURING CRYOABLATION

The proximity of the phrenic nerve to right-sided pulmonary veins makes it susceptible to injury during cryoballoon ablation (CBA) for atrial fibrillation (AF). Although there are no specific preprocedural predictors for phrenic nerve injury (PNI), monitoring of diaphragmatic compound motor action potentials (CMAP) has been used for the early detection of PNI. A 30% drop in CMAP amplitude has been shown in animal and clinical studies as the threshold for the prevention of PNI The aims of this study were to assess the relationship of change in CMAP amplitude with change in score map and then use the automated score map prospectively for early detection of PNI during CBA In the first half of the study, we paced the phrenic nerve at 10,8,6,4,2 milliamperes or till loss of capture in 20 pts. The relationship between the change in amplitude of CMAP with a corresponding change in the score map was studied by linear regression. 30% drop in CMAP amplitude was associated with a score map of 89%(R2 0.77). In the second half of the study, we used a score map threshold of 90% and studied 84 pts. Ablation was stopped if the score map of CMAP dipped below 90% consistently for >4 beats to take respiratory variation into account A total of 174 cryo applications were done for the right-sided veins in 84 pts. A consistent score-map >98% was obtained in all pts before the beginning of the CBA. Ablation had to be stopped in 13 pts due to a drop in the score map or CMAP amplitude or decreased diaphragm contraction. 5 pts had transient PNI. Change in score map was noticeable before change in CMAP amplitude or decrease in diaphragm contraction. In 8 pts drop in the score map was attributed to catheter movement which was noted by the change in catheter position on the 3D mapping system. Score-map of CMAP returned to >98% with catheter adjustment or within 5 minutes of ablation termination along with improvement of CMAP amplitude in all cases. No pts were noted to have persistent PNI at the end of the procedure Beat-to-beat changes in CMAP amplitude can be noted with respiratory variation or catheter movement making it difficult to monitor the change in amplitude. By using an automated score rather than continuously measuring CMAP amplitude, score mapping can make monitoring changes in CMAP amplitude easier. This descriptive study demonstrates that a 90 % score-map threshold correlates with a 30% drop in CMAP amplitude and can be safely and reliably used for the early detection of PNI

Social isolation stress favors cardiometabolic comorbidities of sleep apnea

Sleep apnea (SA) is a multifactorial and sex-specific respiratory disorder characterized by repeated respiratory arrests during sleep. However, the origins of this disease are not clearly identified. Chronic stress increases risk for obesity, hypertension, and depression, which are common comorbidities of SA. With the increasing prevalence of obesity and about one-third of the world population reported feeling stressed, the study of the impact of stress on respiratory homeostasis has never been so relevant. Since chronic stress induces the main comorbidities of SA, we hypothesized that social isolation (SI) stress induces sex-specific cardiorespiratory and metabolic disorders in rats similar to patients with SA.80 Sprague Dawley male and female rats (8 weeks old) were kept in: 1) standard housing (2/cage; controls) or in 2) social isolation (1/cage). At the end of the three-week protocol, apneas were quantified by whole-body plethysmography during sleep; respiratory variability was assessed by Poincaré plot analysis. Cardiovascular measurements were obtained by tail cuff, body composition by preclinical magnetic resonance, and plasma leptin and corticosterone levels by multiplex immunoassay. The amount of food was weighed before and after the experiments to calculate the intake.By comparison with controls, SI elevated corticosterone levels in male but not females. SI increased the apnea index in intact rat by 21% and augmented respiratory instability. SI also increased blood pressure (+11mmHg) and food intake (+11g/day); however, females had lower increases than males. In males, SI increases weight gains, fat mass, and decreases plasma leptin levels; these effects were not observed in females.SI promotes the emergence of apnea and respiratory instability during sleep. Since the cardiorespiratory and metabolic disturbances are similar to clinical features of SA patient, we propose that stress plays an important role in the etiology of SA. SI offers a novel and unique opportunity to study the origins and pathophysiology of SA. This research is supported by operating grants from the Canadian Institutes of Health Research (CIRH, RK and VJ). N.J.M. was supported by a Sentinel North Partnered Research Chair in Sleep Pharmacometabolism and a Fonds de Recherche du Quebec Sante (FRQS) Research Scholar J1 award. MG is the recipient of a doctoral scholarship from the FRQS. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Role of Power and Frequency Characteristics of the Cardiorespiratory System in Conditions of Minimal Physical Exercise

It is our point of view that it is necessary to study in more detail and consistently the dynamics of joint reactions of respiration and blood circulation during physical load. The study aims to determine which component of the cardiorespiratory system is a more labile parameter in forming the body's adaptive reactions in minimal physical loads. The objectives of the study are to reveal the role of respiratory and cardiovascular components of the cardiorespiratory system in achieving the overall useful result during bicycle ergometry exercises of minimal power and to make a comparison of expressiveness changes in respiratory amplitude and its rate as well as to carry out comparing human cardiorespiratory system activity and the one in animals. Healthy young people of both sexes were examined. They were provided with standard stages of short-term physical exercise load ranging from negligible to moderate. A bicycle ergometer with a pedaling rhythm of 40 per minute was used to ensure this. Before loading, at its peak, and after it, spirography, pulsometry, and tonometry were performed. These parameters were obtained for each subject simultaneously. The principles of forming cardiorespiratory interaction, revealed in the given study in humans, corresponded with the parameters of baro - and chemoreflex obtained by us earlier in acute experiments on cats. The statistical analysis was carried out using Statistica ® 7.0 package (StatSoft Inc., USA). The results' significance was assessed using Student's t-test and sign test. At minimal physical exercises, pulmonary ventilation is performed through more pronounced changes in respiratory amplitude and less markedly through respiratory rate variations. Under given conditions, domination of the respiratory system, activity was proved to be most effective. Arterial pressure and pulse react least of all. First, the systemic blood pressure increases, and the changes in cardiac frequency activity are realized last. In such cases, this parameter even can remain unchanged. The principles that define the different intensities of cardiorespiratory system components' activity for human organisms and animals turn out to be similar.

Bending Saturation Index – A Novel Index of Old Symptom a Marker of Elevated Filling Pressure in Heart Failure

Objectives: Bendopnea is a symptom in patients with heart failure (HF) defined as shortness of breath when bending forward. It is mediated by increased ventricular filling pressure during bending forward. Qualification of bendopnea and its correltion with other symptoms and parameters of HF is not a much explored area. In this study, we studied the frequency of bendopnea in patients admitted with HF and a index of difference between sitting and bending saturations and its correlation with clinical, laboratory, and echocardiographic and short-term mortality. Material and Methods: We conducted a study of 150 patients admitted with DHF in the span of 5 month and followed for 1 month. Bendopnea is defined as subjective sensation of worsening shortness of breath after bending for 1 min or more. Saturations after bending for 1 min are also recorded for each patient. Bendopnea saturation index (BOSI) is calculated as difference between saturations at baseline and after bending over, its percentage over baseline saturation (SaO2 sitting - SaO2 bending/SaO2 sitting*100). Results: It was present in 61 patients (40.7%). Among 150 patients, 11 patientns (7.3%) expired. Orthopnea was more frequent in patients with bendopnea compared to patients without (59% of patients with bendopnea also had orthopnea and 34.8% of patients without bendopnea had orthopnea, and the difference was statistically significant (P = 0.03). Paroxysmal nocturnal dyspnea (PND) was present in 29.5% of patients with bendopnea and 11% of patients without bendopnea (P = 0.05). The patients with bendopnea had higher right ventricular systolic pressure (RVSP) (49.9 ± 1.6) compared to patients without bendopnea (33.5 ± 0.9). Average NT pro BNP values were 8717 ± 950 pg/mL in patients with bendopnea and 1110 ± 99 pg/mL in patients without bendopnea (P < 0.005). Mean BOSI was 4.4 (±2.9) in patients with bendopnea and 0.4 (±0.09) in patients without bendopnea. There was a negative correlation between BOSI and left ventricular ejection fraction (LVEF), and positive correlation between BOSI and RVSP. Among patients with bendopnea, six patients expired, when compared with patients who were alive after 1 month using t-test, patients who expired have higher average BOSI (P < 0.005). Conclusion: Bendopnea and falling of desaturation on bending is a sign of significance in HF patients. The presence of bendopnea correlated with increased pulmonary arterial pressure and with other symptoms of respiratory variation, namely – orthopnea and PND, and higher values of biomarker (NTproBNP). BOSI, but not bendopnea had significant positive correlation with RVSP, and negative correlation with LVEF. BOSI also correlated with short-term mortality.

Assessment of the inferior vena cava collapsibility from subcostal and trans-hepatic imaging using both M-mode or artificial intelligence: a prospective study on healthy volunteers

PurposeAssessment of the inferior vena cava (IVC) respiratory variation may be clinically useful for the estimation of fluid-responsiveness and venous congestion; however, imaging from subcostal (SC, sagittal) region is not always feasible. It is unclear if coronal trans-hepatic (TH) IVC imaging provides interchangeable results. The use of artificial intelligence (AI) with automated border tracking may be helpful as part of point-of-care ultrasound but it needs validation.MethodsProspective observational study conducted in spontaneously breathing healthy volunteers with assessment of IVC collapsibility (IVCc) in SC and TH imaging, with measures taken in M-mode or with AI software. We calculated mean bias and limits of agreement (LoA), and the intra-class correlation (ICC) coefficient with their 95% confidence intervals.ResultsSixty volunteers were included; IVC was not visualized in five of them (n = 2, both SC and TH windows, 3.3%; n = 3 in TH approach, 5%). Compared with M-mode, AI showed good accuracy both for SC (IVCc: bias − 0.7%, LoA [− 24.9; 23.6]) and TH approach (IVCc: bias 3.7%, LoA [− 14.9; 22.3]). The ICC coefficients showed moderate reliability: 0.57 [0.36; 0.73] in SC, and 0.72 [0.55; 0.83] in TH. Comparing anatomical sites (SC vs TH), results produced by M-mode were not interchangeable (IVCc: bias 13.9%, LoA [− 18.1; 45.8]). When this evaluation was performed with AI, such difference became smaller: IVCc bias 7.7%, LoA [− 19.2; 34.6]. The correlation between SC and TH assessments was poor for M-mode (ICC = 0.08 [− 0.18; 0.34]) while moderate for AI (ICC = 0.69 [0.52; 0.81]).ConclusionsThe use of AI shows good accuracy when compared with the traditional M-mode IVC assessment, both for SC and TH imaging. Although AI reduces differences between sagittal and coronal IVC measurements, results from these sites are not interchangeable.

Prognostic Value of Respiratory Variation in Right Atrial Pressure in Patients With Precapillary Pulmonary Hypertension

Precapillary pulmonary hypertension (PH) is characterized by elevated mean pulmonary artery pressure from increased pulmonary vascular resistance (PVR). Lack of respiratory variation in right atrial pressure (RAP) can be viewed as a surrogate for severe PH and inability of the right ventricle (RV) to tolerate preload augmentation during inspiration. Is the lack of respiratory variation in RAP predictive of RV dysfunction and worse clinical outcomes in precapillary PH? We retrospectively reviewed RAP tracings of patients with precapillary PH who underwent right heart catheterization. Patients with respiratory variation in RAP (end expiratory - end inspiratory) ≤2 mmHg were considered to have effectively no meaningful variation in RAP. Lack of respiratory variation in RAP was associated with lower cardiac index by indirect Fick (2.34±0.09 vs. 2.76±0.1 L/min/m2, p=0.001), lower pulmonary artery saturation (60±1.02% vs 64±1.15%, p=0.007), higher PVR (8.9±0.44 vs 6.1±0.49 Wood units, p<0.0001), RV dysfunction on echocardiography (87.3% vs 38.8%, p<0.0001), higher proBNP (2163±2997 vs 633±402 ng/ml, p<0.0001), and more hospitalizations within 1 year for RV failure (65.4% vs 29.6%, p<0.0001). There was also a trend toward higher mortality at 1 year in patients with no respiratory variation in RAP (25.4% vs 11.1%, p=0.06). Lack of respiratory variation in RAP is associated with poor clinical outcomes, adverse hemodynamic parameters, and RV dysfunction in patients with precapillary PH. Larger studies are needed to further evaluate its utility in prognosis and potential risk stratification in patients with precapillary PH.

Respiratory Variations of Central Venous Pressure as Indices of Pleural Pressure Swings: A Narrative Review

The measurement of pleural (or intrathoracic) pressure is a key element for a proper setting of mechanical ventilator assistance as both under- and over-assistance may cause detrimental effects on both the lungs and the diaphragm. Esophageal pressure (Pes) is the gold standard tool for such measurements; however, it is invasive and seldom used in daily practice, and easier, bedside-available tools that allow for rapid and continuous monitoring are greatly needed. The tidal swing of central venous pressure (CVP) has long been proposed as a surrogate for pleural pressure (Ppl); however, despite the wide availability of central venous catheters, this variable is very often overlooked in critically ill patients. In the present narrative review, the physiological basis for the use of CVP waveforms to estimate Ppl is presented; the findings of previous and recent papers that addressed this topic are systematically reviewed, and the studies are divided into those reporting positive findings (i.e., CVP was found to be a reliable estimate of Pes or Ppl) and those reporting negative findings. Both the strength and pitfalls of this approach are highlighted, and the current knowledge gaps and direction for future research are delineated.

Analysis of the Cardiorespiratory Pattern of Patients Undergoing Weaning Using Artificial Intelligence

The optimal extubating moment is still a challenge in clinical practice. Respiratory pattern variability analysis in patients assisted through mechanical ventilation to identify this optimal moment could contribute to this process. This work proposes the analysis of this variability using several time series obtained from the respiratory flow and electrocardiogram signals, applying techniques based on artificial intelligence. 154 patients undergoing the extubating process were classified in three groups: successful group, patients who failed during weaning process, and patients who after extubating failed before 48 hours and need to reintubated. Power Spectral Density and time-frequency domain analysis were applied, computing Discrete Wavelet Transform. A new Q index was proposed to determine the most relevant parameters and the best decomposition level to discriminate between groups. Forward selection and bidirectional techniques were implemented to reduce dimensionality. Linear Discriminant Analysis and Neural Networks methods were implemented to classify these patients. The best results in terms of accuracy were, 84.61 ± 3.1% for successful versus failure groups, 86.90 ± 1.0% for successful versus reintubated groups, and 91.62 ± 4.9% comparing the failure and reintubated groups. Parameters related to Q index and Neural Networks classification presented the best performance in the classification of these patients.

Aortic Peak Flow Velocity As a Predictor of Fluid Responsiveness in Mechanically Ventilated Children: A Systematic Review and Meta-Analysis.

This meta-analysis aimed to determine the accuracy of the respiratory variations in aortic peak flow velocity (delta Vpeak) in predicting fluid responsiveness and the moderators of that accuracy. We performed searches for studies that used delta Vpeak as a predictor of fluid responsiveness in mechanically ventilated children in PubMed, Embase, Scopus, and CINAHL from inception to June 20, 2022. Fifteen studies ( n = 452) were included in this meta-analysis. The diagnostic test data of the included studies were synthesized as pooled sensitivity, specificity, and diagnostic odds ratio (DOR) and the area under the curve (AUC) of the summary receiver operating characteristic of delta Vpeak. The delta Vpeak cutoff values applied in these studies had a median of 12.3% (interquartile range, 11.50-13.25%). The pooled sensitivity and specificity of delta Vpeak were 0.80 (95% CI, 0.71-0.87) and 0.82 (95% CI, 0.75-0.87), respectively. The DOR of delta Vpeak was 23.41 (95% CI, 11.61-47.20). The AUC of delta Vpeak was 0.87. Subgroup analyses revealed that the accuracy of delta Vpeak was not moderated by ventilator settings, measures of delta Vpeak, gold standard index, the cutoff gold standard value of responders, type and volume of fluid, duration of fluid challenge, use of vasoactive drugs, general anesthesia, and cardiopulmonary bypass. By using the cutoff of approximately 12.3%, the delta Vpeak appears to have good accuracy in predicting fluid responsiveness in mechanically ventilated children. The moderators of delta Vpeak predictability are not found.

Non-invasive assessment of Pulse Wave Transit Time (PWTT) is a poor predictor for intraoperative fluid responsiveness: a prospective observational trial (best-PWTT study)

BackgroundAim of this study is to test the predictive value of Pulse Wave Transit Time (PWTT) for fluid responsiveness in comparison to the established fluid responsiveness parameters pulse pressure (ΔPP) and corrected flow time (FTc) during major abdominal surgery.MethodsForty patients undergoing major abdominal surgery were enrolled with continuous monitoring of PWTT (LifeScope® Modell J BSM-9101 Nihon Kohden Europe GmbH, Rosbach, Germany) and stroke volume (Esophageal Doppler Monitoring CardioQ-ODM®, Deltex Medical Ltd, Chichester, UK). In case of hypovolemia (difference in pulse pressure [∆PP] ≥ 9%, corrected flow time [FTc] ≤ 350 ms) a fluid bolus of 7 ml/kg ideal body weight was administered. Receiver operating characteristics (ROC) curves and corresponding areas under the curve (AUCs) were used to compare different methods of determining PWTT. A Wilcoxon test was used to discriminate fluid responders (increase in stroke volume of ≥ 10%) from non-responders. The predictive value of PWTT for fluid responsiveness was compared by testing for differences between ROC curves of PWTT, ΔPP and FTc using the methods by DeLong.ResultsAUCs (area under the ROC-curve) to predict fluid responsiveness for PWTT-parameters were 0.61 (raw c finger Q), 0.61 (raw c finger R), 0.57 (raw c ear Q), 0.53 (raw c ear R), 0.54 (raw non-c finger Q), 0.52 (raw non-c finger R), 0.50 (raw non-c ear Q), 0.55 (raw non-c ear R), 0.63 (∆ c finger Q), 0.61 (∆ c finger R), 0.64 (∆ c ear Q), 0.66 (∆ c ear R), 0.59 (∆ non-c finger Q), 0.57 (∆ non-c finger R), 0.57 (∆ non-c ear Q), 0.61 (∆ non-c ear R) [raw measurements vs. ∆ = respiratory variation; c = corrected measurements according to Bazett’s formula vs. non-c = uncorrected measurements; Q vs. R = start of PWTT-measurements with Q- or R-wave in ECG; finger vs. ear = pulse oximetry probe location]. Hence, the highest AUC to predict fluid responsiveness by PWTT was achieved by calculating its respiratory variation (∆PWTT), with a pulse oximeter attached to the earlobe, using the R-wave in ECG, and correction by Bazett’s formula (AUC best-PWTT 0.66, 95% CI 0.54–0.79). ∆PWTT was sufficient to discriminate fluid responders from non-responders (p = 0.029). No difference in predicting fluid responsiveness was found between best-PWTT and ∆PP (AUC 0.65, 95% CI 0.51–0.79; p = 0.88), or best-PWTT and FTc (AUC 0.62, 95% CI 0.49–0.75; p = 0.68).ConclusionΔPWTT shows poor ability to predict fluid responsiveness intraoperatively. Moreover, established alternatives ΔPP and FTc did not perform better.Trial registrationPrior to enrolement on clinicaltrials.gov (NC T03280953; date of registration 13/09/2017).

Accuracy of Respiratory Variation in Inferior Vena Cava Diameter to Predict Fluid Responsiveness in Children Under Mechanical Ventilation.

Proper assessment of fluid responsiveness using accurate predictors is crucial to guide fluid therapy and avoid the serious adverse effects of fluid overload. The main objective of this study was to investigate the accuracy of respiratory variations in inferior vena cava diameter (∆IVC) to predict fluid responsiveness in mechanically ventilated children. This prospective single-center study included 32 children (median age and weight of 17months and 10kg, respectively) who received a fluid infusion of 10ml kg-1 of crystalloid solutions over 10min. ∆IVC and respiratory variation in aortic blood flow peak velocity (∆Vpeak) were determined over one controlled respiratory cycle before and after fluid loading. Thirteen (41%) participants were fluid-responders. ∆IVC, ∆Vpeak, stroke volume index, and cardiac index were found to be predictors of fluid responsiveness. However, the area under the ROC curve of ∆IVC was smaller when compared to ∆Vpeak (0.709 vs. 0.935, p < 0.012). The best cut-off values were 7.7% for ∆IVC (sensitivity, 69.2%; specificity 78.9%, positive predictive value, 69.2%; and negative predictive value, 78.9%) and 18.2% for ∆Vpeak (sensitivity, 84.6%; specificity, 89.5%; positive predictive value, 84.6%; negative predictive value, 89.5%). Changes in stroke volume were positively correlated with ∆IVC (ρ = 0.566, p < 0.001) and ∆Vpeak (ρ = 0.603, p < 0.001). A significant correlation was also found between changes in MAP and ∆Vpeak (ρ = 0.382; p = 0.031), but the same was not observed with ∆IVC (ρ = 0.011; p = 0.951). In conclusion, ∆IVC was found to have a moderate accuracy in predicting fluid responsiveness in mechanically ventilated children and is an inferior predictor when compared to ∆Vpeak.

Study of Respiratory Variations of Mitral Valve Diastolic Flow in Hemodialysis Patients.

The respiratory variations in mitral valve (MV) Doppler flow in hemodialysis (HD) patients have not been investigated and the normal echocardiographic value is used as a reference for HD patients. The present study evaluated the respiratory variation in MV Doppler flow in HD patients to determine if it has a unique pattern. In this prospective cohort study, echocardiography was performed before and 6 h after dialysis. The transmitral spectral Doppler E wave was measured during inspiratory and expiratory phases. The percent changes in the E wave were calculated pre- and post-dialysis. The means of the percent variation in the MV inspiratory and expiratory E wave pre- and post-dialysis were 56 ± 7% and 44 ± 1.1%, respectively, with a significant reduction after dialysis (P = .000). There was a significant positive correlation between post-dialysis ∆E wave % change and post-dialysis % change in weight (r = .318; P = .000). The respiratory changes in the MV E wave in HD patients were higher than the normal reference values. This marked variation could be explained by fluid overloading in HD patients.

Direct machine learning reconstruction of respiratory variation waveforms from resting state fMRI data in a pediatric population

In many functional magnetic resonance imaging (fMRI) studies, respiratory signals are unavailable or do not have acceptable quality due to issues with subject compliance, equipment failure or signal error. In large databases, such as the Human Connectome Projects, over half of the respiratory recordings may be unusable. As a result, the direct removal of low frequency respiratory variations from the blood oxygen level-dependent (BOLD) signal time series is not possible. This study proposes a deep learning-based method for reconstruction of respiratory variation (RV) waveforms directly from BOLD fMRI data in pediatric participants (aged 5 to 21 years old), and does not require any respiratory measurement device. To do this, the Lifespan Human Connectome Project in Development (HCP-D) dataset, which includes respiratory measurements, was used to both train a convolutional neural network (CNN) and evaluate its performance. Results show that a CNN can capture informative features from the BOLD signal time course and reconstruct accurate RV timeseries, especially when the subject has a prominent respiratory event. This work advances the use of direct estimation of physiological parameters from fMRI, which will eventually lead to reduced complexity and decrease the burden on participants because they may not be required to wear a respiratory bellows.

Dynamic variables to predict fluid responsiveness in young children.

The evidence that dynamic variables predict fluid responsiveness in young children is limited by conflicting research results. Sixty patients, 1-3 years of age, undergoing major neurosurgery, received 10mL/kg of Ringer's solution over 10min after anesthesia induction. Respiratory variation in aortic blood flow peak velocity (∆Vpeak), plethysmographic variability index (PVI), FloTrac/Vigileo-derived stroke volume variation (SVV), dynamic arterial elastance (Eadyn ), and pulse pressure variation (PPV) were measured before and following fluid loading. An increase in the cardiac index (CI) of ≥10% following fluid loading identified fluid "responders." Twenty-six patients (43.3%) were fluid responders. Baseline ∆Vpeak was an excellent predictor of a CI increase following fluid loading with an area under the receiver operating characteristic curve (AUROC) of 0.982 (p < 0.001). The PVI showed fair diagnostic accuracy for CI-fluid responsiveness (AUROC 0.775, p < 0.001). Baseline ∆Vpeak and PVI cutoff values were 9.6% and 15%, respectively. PPV, SVV, and Eadyn were not predictors or were poor predictors for CI-fluid responsiveness (AUROC 0.669, 0.653, and 0.533, respectively). Volume-based PVI and ∆Vpeak showed acceptable reliability for fluid responsiveness prediction in young children undergoing major neurosurgery, whereas pressure-based SVV using FloTrac/Vigileo, Eadyn , and PPV did not.

Accuracy and Feasibility of Synthetic CT for Lung Adaptive Radiotherapy: A Phantom Study.

The respiratory variations will lead to inconsistency between the actual delivery dose and the planning dose. How the minor interfractional amplitude changes affect the geometry and dose delivery accuracy remains to be investigated in the context of lung adaptive radiotherapy. Planning 4-dimensional-computed tomography and kV-cone beam computed tomography were scanned based on the Computerized Imaging Reference Systems phantom, which was employed to simulate the minor interfractional amplitude variations. The corresponding synthetic computed tomography for a particular motion pattern can be generated from Velocity program. Then a clinically meaningful synthetic computed tomography was analyzed through the geometrical and dosimetric assessment. The image quality of synthetic computed tomography was improved obviously compared with cone beam computed tomography. Mean absolute error was minimized when no significant interfractional motion occurs and Velocity can be qualified for dealing with the regular breathing motion patterns. The mean percent hounsfield unit difference of the synthetic hounsfield unit values per organ relative to the planning 4-dimensional-computed tomography image was 22.3%. Under the same conditions, the mean percent hounsfield unit difference of the cone beam computed tomography hounsfield unit values per organ, relative to the planning 4-dimensional-computed tomography image was 83.9%. Overall, the accuracy of hounsfield unit in synthetic computed tomography was improved obviously and the variability of the synthetic image correlates with the planning 4-dimensional-computed tomography image variability. Meanwhile, the dose-volume histograms between planning 4-dimensional-computed tomography and synthetic computed tomography almost coincided each other, which indicates that Velocity program can qualify lung adaptive radiotherapy well when there were no interfractional respiratory variations. However, for cases with obvious interfractional amplitude change, the volume covered at least by 100% of the prescription dose was only 59.6% for that synthetic image. The synthetic computed tomography images generated from Velocity were close to the real images in anatomy and dosimetry, which can make clinical lung adaptive radiotherapy possible based on the actual patient anatomy during treatment.

Assessing the Complicated Venous Hemodynamics and Therapeutic Outcomes of Budd-Chiari Syndrome with Respiratory-gated 4D Flow MR Imaging During the Expiratory and Inspiratory Phases.

A man in his 50s with Budd-Chiari syndrome diagnosed with the suprahepatic inferior vena cava (IVC) obstruction on CT was assessed using 4D Flow MRI before and after balloon angioplasty. 4D Flow MRI acquired in two respiratory phases, depicted complex hemodynamic and respiratory variability, and a jet stream at the narrowed channel of the membranous IVC. Post-interventional 4D Flow MRI showed that the IVC blood flow increased with corrected flow directions in the infrarenal IVC.

Clinical applications of contactless photoplethysmography for monitoring in adults: A systematic review and meta-analysis.

Contactless photoplethysmography (cPPG) is a method of physiological monitoring. It differs from conventional monitoring methods (e.g., saturation probe) by ensuring no contact with the subject by use of a camera. The majority of research on cPPG is conducted in a laboratory setting or in healthy populations. This review aims to evaluate the current literature on monitoring using cPPG in adults within a clinical setting. Adhering to the Preferred Items for Systematic Reviews and Meta-analysis (PRISMA, 2020) guidelines, OVID, Webofscience, Cochrane library, and clinicaltrials.org were systematically searched by two researchers. Research articles using cPPG for monitoring purposes in adults within a clinical setting were selected. Twelve studies with a total of 654 individuals were included. Heart rate (HR) was the most investigated vital sign (n = 8) followed by respiratory rate ((n = 2), Sp02 (n = 2), and HR variability (n = 2). Four studies were included in a meta-analysis of HR compared to ECG data which demonstrated a mean bias of -0.13 (95% CI, -1.22-0.96). This study demonstrates cPPG can be a useful tool in the remote monitoring of patients and has demonstrated accuracy for HR. However, further research is needed into the clinical applications of this method.