Impaired respiratory variation of right atrial pressure (RAP) in severe pulmonary hypertension (PH) suggests difficulty tolerating increased preload during inspiration. Our study explores whether this impairment links to specific factors: right ventricular (RV) diastolic function, elevated RV afterload, systolic RV function, or RV-pulmonary arterial (PA) coupling. We retrospectively evaluated respiratory RAP variation in all participants enrolled in the EXERTION study. Impaired respiratory variation was defined as end-expiratory RAP - end-inspiratory RAP ≤ 2 mm Hg. RV function and afterload were evaluated using conductance catheterization. Impaired diastolic RV function was defined as end-diastolic elastance (Eed) ≥ median (0.19 mm Hg/mL). Seventy-five patients were included; PH was diagnosed in 57 patients and invasively excluded in 18 patients. Of the 75 patients, 31 (41%) had impaired RAP variation, which was linked with impaired RV systolic function and RV-PA coupling and increased tricuspid regurgitation and Eed as compared to patients with preserved RAP variation. In backward regression, RAP variation associated only with Eed. RAP variation but not simple RAP identified impaired diastolic RV function (area under the receiver operating characteristic curve [95% confidence interval]: 0.712 [0.592, 0.832] and 0.496 [0.358, 0.634], respectively). During exercise, patients with impaired RAP variation experienced greater RV dilatation and reduced diastolic reserve and cardiac output/index compared with patients with preserved RAP variation. Preserved RAP variation was associated with a better prognosis than impaired RAP variation based on the 2022 European Society of Cardiology/European Respiratory Society risk score (chi-square P = 0.025) and survival free from clinical worsening (91% vs 71% at 1 year and 79% vs 50% at 2 years [log-rank P = 0.020]; hazard ratio: 0.397 [95% confidence interval: 0.178, 0.884]). Subgroup analyses in patients with group 1 and group 4 PH demonstrated consistent findings with those observed in the overall study cohort. Respiratory RAP variations reflect RV diastolic function, are independent of RV-PA coupling or tricuspid regurgitation, are associated with exercise-induced haemodynamic changes, and are prognostic in PH.Trial registration. NCT04663217.

UNASSIGNED: The objective of this study is to assess concordance between the subcostal and right lateral view for ultrasonographic inferior vena cava measurements including the end-inspiratory diameter, end-expiratory diameter and respiratory variation represented by the caval index in spontaneously breathing healthy adults.
UNASSIGNED: We recruited a convenience sample of 33 healthy adults. A phased array ultrasound probe was used to obtain inferior vena cava measurements from a subcostal view in the sagittal plane and from a right lateral view in the coronal plane with B-mode ultrasound. End-inspiratory diameter, end-expiratory diameter and caval index were obtained for each view. A two-tailed t-test was performed to compare the caval indices obtained by the two views. Bland-Altman analysis was used to obtain the limits of agreement for the inferior vena cava diameter and caval index across the two views.
UNASSIGNED: Subcostal and right lateral caval indices across all participants were significantly different according to a paired t-test (p < 0.0001). The Bland-Altman analysis showed wide limits of agreement in end-inspiratory diameter (-0.97 and 0.50 cm) and in end-expiratory diameter (-0.94 and 0.90 cm). The right lateral view underestimated the inferior vena cava caval index relative to the subcostal view.
UNASSIGNED: The subcostal and right lateral views are not equivalent in obtaining inferior vena cava measurements in spontaneously breathing healthy adults. Current cut-off values for measurement-based applications of inferior vena cava ultrasound, including fluid responsiveness using caval indices, may not be accurate when values are obtained from the right lateral view in the coronal plane of the inferior vena cava in patients.

Precapillary pulmonary hypertension is characterized by elevated mean pulmonary artery pressure from increased pulmonary vascular resistance. Lack of respiratory variation in right atrial pressure can be viewed as a surrogate for severe pulmonary hypertension and inability of the right ventricle to tolerate preload augmentation during inspiration.
Is the lack of respiratory variation in right atrial pressure predictive of right ventricular dysfunction and worse clinical outcomes in precapillary pulmonary hypertension?
We retrospectively reviewed right atrial pressure tracings of patients with precapillary pulmonary hypertension who underwent right heart catheterization. Patients with respiratory variation in right atrial pressure (end expiratory-end inspiratory) ≤ 2 mm Hg were considered to have effectively no meaningful variation in right atrial pressure.
Lack of respiratory variation in right atrial pressure was associated with lower cardiac index by indirect Fick (2.34 ± 0.09 vs 2.76 ± 0.1 L/min/m2; P = .001), lower pulmonary artery saturation (60% ± 1.02% vs 64% ± 1.15%; P = .007), higher pulmonary vascular resistance (8.9 ± 0.44 vs 6.1 ± 0.49 Wood units, P < .0001), right ventricular dysfunction on echocardiography (87.3% vs 38.8%; P < .0001), higher pro brain natriuretic peptide (2,163 ± 2,997 vs 633 ± 402 ng/mL; P < .0001), and more hospitalizations within 1 year for right ventricular failure (65.4% vs 29.6%; P < .0001). There was also a trend toward higher mortality at 1 year in patients with no respiratory variation in right atrial pressure (25.4% vs 11.1%; P = .06).
Lack of respiratory variation in right atrial pressure is associated with poor clinical outcomes, adverse hemodynamic parameters, and right ventricular dysfunction in patients with precapillary pulmonary hypertension. Larger studies are needed to further evaluate its utility in prognosis and potential risk stratification in patients with precapillary pulmonary hypertension.

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.

OBJECTIVE: This study aimed to determine the predictive value of carotid artery blood flow (CABF), corrected carotid flow time (CFT), and respiratory variation in carotid peak systolic velocity (DVPeakCA) for fluid responsiveness in mechanically ventilated patients undergoing coronary artery bypass grafting (CABG) surgery. It also aimed to correlate each of these indices with changes in stroke volume index (SVI) after a fluid bolus.
METHODS: This prospective, interventional, before-after study recruited 45 adult patients undergoing CABG. Following induction of anesthesia, a fluid challenge of 6 ml/kg of a crystalloid solution was delivered over 10 min. Mean arterial pressure (MAP), heart rate (HR), central venous pressure (CVP), CABF, CFT, and DVPeakCA were recorded before and following the intervention. Patients with an increase in SVI of >15% from baseline were considered responders.
RESULTS: We had 22 responders and 23 nonresponders. Areas under the receiver operating characteristic (AUROC) curves for the studied indices (CABF, 0.516, CFT, 0.502, and DVPeakCA, 0.671) did not suggest any strong predictive value to detect fluid responsiveness. Similarly, the r values for correlation of these carotid doppler-derived indices, both baseline and as % change from baseline with the % alteration of SVI were all <0.2, which demonstrates a very weak correlation between these variables.
CONCLUSIONS: Carotid doppler indices are unreliable to assess fluid responsiveness, and cannot replace invasive methods of analyzing preload optimization. There was no significant correlation between carotid doppler-derived indices and alterations in SVI before and after the fluid bolus.

Background: The autonomic nervous system (ANS) is known as a potent modulator of the initiation and perpetuation of atrial fibrillation (AF), hence information about ANS activity during AF may improve treatment strategy. Respiratory induced ANS variation in the f-waves of the ECG may provide such information. Objective: This paper proposes a novel approach for improved estimation of such respiratory induced variations and investigates the impact of deep breathing on the f-wave frequency in AF patients. Methods: A harmonic model is fitted to the f-wave signal to estimate a high-resolution f-wave frequency trend, and an orthogonal subspace projection approach is employed to quantify variations in the frequency trend that are linearly related to respiration using an ECG-derived respiration signal. The performance of the proposed approach is evaluated and compared to that of a previously proposed bandpass filtering approach using simulated f-wave signals. Further, the proposed approach is applied to analyze ECG data recorded for 5 min during baseline and 1 min deep breathing from 28 AF patients from the Swedish cardiopulmonary bioimage study (SCAPIS). Results: The simulation results show that the estimates of respiratory variations obtained using the proposed approach are more accurate than estimates obtained using the previous approach. Results from the analysis of SCAPIS data show no significant differences between baseline and deep breathing in heart rate (75.5 ± 22.9 vs. 74 ± 22.3) bpm, atrial fibrillation rate (6.93 ± 1.18 vs. 6.94 ± 0.66) Hz and respiratory f-wave frequency variations (0.130 ± 0.042 vs. 0.130 ± 0.034) Hz. However, individual variations are large with changes in heart rate and atrial fibrillatory rate in response to deep breathing ranging from -9% to +5% and -8% to +6%, respectively and there is a weak correlation between changes in heart rate and changes in atrial fibrillatory rate (r = 0.38, p < 0.03). Conclusion: Respiratory induced f-wave frequency variations were observed at baseline and during deep breathing. No significant changes in the magnitude of these variations in response to deep breathing was observed in the present study population.

The validation of inferior vena cava (IVC) respiratory variation for predicting volume responsiveness is still under debate, especially in spontaneously breathing patients. The present study aims to verify the effectiveness and accuracy of IVC variability for volume assessment in the patients after abdominal surgery under artificially or spontaneously breathing.
A total of fifty-six patients after abdominal surgeries in the anesthesia intensive care unit ward were included. All patients received ultrasonographic examination before and after the fluid challenge of 5 ml/kg crystalloid within 15 min. The same measurements were performed when the patients were extubated. The IVC diameter, blood flow velocity-time integral of the left ventricular outflow tract, and cardiac output (CO) were recorded. Responders were defined as an increment in CO of 15% or more from baseline.
There were 33 (58.9%) mechanically ventilated patients and 22 (39.3%) spontaneously breathing patients responding to fluid resuscitation, respectively. The area under the curve was 0.80 (95% CI: 0.68-0.90) for the IVC dimeter variation (cIVC1) in mechanically ventilated patients, 0.87 (95% CI: 0.75-0.94) for the collapsibility of IVC (cIVC2), and 0.85 (95% CI: 0.73-0.93) for the minimum IVC diameter (IVCmin) in spontaneously breathing patients. The optimal cutoff value was 15.32% for cIVC1, 30.25% for cIVC2, and 1.14 cm for IVCmin. Furthermore, the gray zone for cIVC2 was 30.72 to 38.32% and included 23.2% of spontaneously breathing patients, while 17.01 to 25.93% for cIVC1 comprising 44.6% of mechanically ventilated patients. Multivariable logistic regression analysis indicated that cIVC was an independent predictor of volume assessment for patients after surgery irrespective of breathing modes.
IVC respiratory variation is validated in predicting patients\' volume responsiveness after abdominal surgery irrespective of the respiratory modes. However, cIVC or IVCmin in spontaneously breathing patients was superior to cIVC in mechanically ventilated patients in terms of clinical utility, with few subjects in the gray zone for the volume responsiveness appraisal.
ChiCTR-INR-17013093 . Initial registration date was 24/10/2017.

Ultrasound assessment of inferior vena cava (IVC) diameter and its respiratory variation is widely used to estimate right atrial pressure (RAP). Generally, the IVC distends as the RAP rises; however, there may be discrepancies between the values. Therefore, it is critical to recognize clinical factors other than RAP that may influence IVC measurements.
We obtained the IVC maximum diameter and IVC collapsibility index (IVCCI) simultaneously during right-heart catheterization in 71 consecutive patients. Then, we assessed various clinical and hemodynamic factors to elucidate the independent determinants of IVC measurements. Moreover, we tried to generate the regression equation to estimate mean RAP from the IVC maximum diameter and IVCCI.
The mean IVC maximum diameter and IVCCI were 15 ± 4 mm and 51 ± 15%, respectively. In stepwise multivariate analysis, the higher mean RAP (β = 0.52; p < 0.0001), the presence of significant tricuspid regurgitation (β = 0.31; p = 0.0005), a larger body surface area (β = 0.22; p = 0.0017), and younger age (β = -0.18; p = 0.049) were independently associated with the IVC maximum diameter. Only the mean RAP was independently associated with the IVCCI (β = -0.45; p < 0.0001). The regression equation (R2 = 0.43, p < 0.0001) was as follows: estimated mean RAP = 3.7 + 0.62 × maximum IVC diameter / BSA - 0.07 × IVCCI.
Distension of the IVC mainly occurs with elevated RAP. However, the presence of significant tricuspid regurgitation, a larger body surface area, and younger age are associated with the IVC maximum diameter, independently of RAP. Interestingly, IVCCI is influenced only by RAP.

A 20-year-old male without any symptoms was referred for heart murmur on a medical examination. A thrill was palpable at the upper left sternal border. His cardiac murmur showed respiratory variation. The systolic murmur was louder (Levine grade IV/VI) during expiration and diminished during inspiration (Levine grade I/VI). He was thin and had a narrow thoracic cage in the anteroposterior direction due to straight back syndrome (SBS). An echocardiogram and a right ventriculogram showed changes in the diameter of the right ventricular outflow tract (RVOT) on respiration. During expiration, the RVOT was compressed and narrow, while it was expanded during inspiration. Cardiac catheterization demonstrated a 10-mmHg of pressure gradient across the RVOT during expiration but no pressure gradient during inspiration. Thus, respiratory compression to the RVOT by a narrow thoracic cage due to SBS was the cause of the cardiac murmur with respiratory alterations. Our case highlights the importance of physical examination, including an inspection of the patient\'s physique. .

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.