Quantitative computed tomography in comparison with transpulmonary thermodilution for the estimation of pulmonary fluid status: a clinical study in critically ill patients

Approximation of EVLWI in severe COVID-19 pneumonia using quantitative imaging techniques: an observational study

BACKGROUND

This study aimed to approximate the level of extravascular lung water (EVLW) in patients with severe COVID-19 pneumonia using quantitative imaging techniques. The elevation of EVLW is known to correlate with the degree of diffuse alveolar damage and linked with the mortality of critically ill patients. Transpulmonary thermodilution (TPTD) is the gold standard technique to estimate the total amount of EVLW, but it is invasive and requires specialized equipment and trained personnel.

METHODS

The study included patients with severe COVID-19 who required chest CT scanning within the first 48 h of Intensive Care Unit (ICU) admission and had TPTD monitoring. Using in-house software tools for automatic semantic segmentation, lung masks were obtained for estimating the EVLW content. The results were compared with the TPTD measurements.

RESULTS

The results demonstrate a significant correlation between EVLW-TPTP measured by thermodilution and EVLW-CT estimated from the patient's CT-image (r = 0.629, p = 0.0014).

CONCLUSION

The study showed that quantitative imaging techniques using chest CT-scans could be used as a convenient and low-cost option for ICUs without TPTD equipment for the assessment of EVLW in severe COVID-19 pneumonia.

Deep phenotyping of pulmonary edema and pulmonary vascular permeability in COVID-19 ARDS

Clinical monitoring of pulmonary edema due to vascular hyperpermeability in acute respiratory distress syndrome (ARDS) poses significant clinical challenges. Presently, no biological or radiological markers are available for quantifying pulmonary edema. Our aim was to phenotype pulmonary edema and pulmonary vascular permeability in patients with coronavirus disease 2019 (COVID-19) ARDS. Transpulmonary thermodilution measurements were conducted in 65 patients with COVID-19 ARDS on the day of intubation to determine the extravascular lung water index (EVLWi) and pulmonary vascular permeability index (PVPi). In parallel, ventilatory parameters, clinical outcomes, the volume of lung opacity measured by chest computed tomography (CT), radiographic assessment of lung edema (RALE) score by chest radiography, and plasma proteomics (358 unique proteins) were compared between tertiles based on the EVLWi and PVPi. Regression models were used to associate EVLWi and PVPi with plasma, radiological, and clinical parameters. Computational pathway analysis was performed on significant plasma proteins in the regression models. Patients with the highest EVLWi values at intubation exhibited poorer oxygenation parameters and more days on the ventilator. Extravascular lung water strongly correlated with the total volume of opacity observed on CT (r = 0.72, P < 0.001), whereas the PVPi had weaker associations with clinical and radiological parameters. Extravascular lung water did not correlate with the RALE score (r = 0.15, P = 0.33). Plasma protein concentrations demonstrated a stronger correlation with PVPi than with EVLWi. The highest tertile of PVPi was associated with proteins linked to the acute phase response (cytokine and chemokine signaling) and extracellular matrix turnover. In the clinical setting of COVID-19 ARDS, pulmonary edema (EVLWi) can be accurately quantified through chest CT and parallels deterioration in ventilatory parameters and clinical outcomes. Vascular permeability (PVPi) is strongly reflected by inflammatory plasma proteins.NEW & NOTEWORTHY This study is unique in that it phenotypes pulmonary edema in COVID-19 ARDS using various clinical parameters and biomarkers. First, there is a noteworthy tipping point in the amount of pulmonary edema at which ventilatory and clinical parameters deteriorate. Second, chest CT gives a good approximation of the amount of pulmonary edema. Finally, pulmonary vascular permeability is strongly reflected by inflammatory plasma proteins.

Lung water density is increased in patients at risk of heart failure and is largely independent of conventional cardiovascular magnetic resonance measures

Aims

Non-invasive methods to quantify pulmonary congestion are lacking in clinical practice. Cardiovascular magnetic resonance (CMR) lung water density (LWD) mapping is accurate and reproducible and has prognostic value. However, it is not known whether LWD is associated with routinely acquired CMR parameters.

Methods and results

This was an observational cohort including healthy controls and patients at risk of heart failure. LWD was measured using CMR with a free-breathing short echo time 3D Cartesian gradient-echo sequence with a respiratory navigator at 1.5 T. Associations were assessed between LWD, lung water volume and cardiac volumes, left ventricular (LV) mass and function, myocardial native T1, and extracellular volume fraction. In patients at risk for heart failure (n = 155), LWD was greater than in healthy controls (n = 15) (30.4 ± 5.0 vs. 27.2 ± 4.3%, P = 0.02). Using receiver operating characteristic analysis, the optimal cut-off for LWD was 27.6% to detect at-risk patients (sensitivity 72%, specificity 73%, positive likelihood ratio 2.7, and inverse negative likelihood ratio 2.6). LWD was univariably associated with body mass index (BMI), hypertension, right atrial area, and LV mass. In multivariable linear regression, only BMI remained associated with LWD (R 2 = 0.32, P < 0.001).

Conclusion

LWD is increased in patients at risk for heart failure compared with controls and is only weakly explained by conventional CMR measures. LWD provides diagnostic information that is largely independent of conventional CMR measures.

Cardiac arrest related lung edema: examining the role of downtimes in transpulmonary thermodilution analysis

Pulmonary edema and its association with low flow times has been observed in postcardiac arrest patients. However, diagnosis of distinct types of lung pathology is difficult.The aim of this study was to investigate pulmonary edema by transpulmonary thermodilution (TPTD) after out-of-hospital cardiac arrest (OHCA), and the correlation to downtimes. In this retrospective single-center study consecutive patients with return of spontaneous circulation (ROSC) following OHCA, age ≥ 18, and applied TPTD were enrolled. According to downtimes, patients were divided into a short and a long no-flow-time group, and data of TPTD were analysed. We identified 45 patients (n = 25 short no-flow time; n = 20 long no-flow time) who met the inclusion criteria. 24 h after ROSC, the extra vascular lung water index (EVLWI) was found to be lower in the group with short no-flow time compared to the group with long no-flow time (10.7 ± 3.5 ml/kg vs. 12.8 ± 3.9 ml/kg; p = 0.08) and remained at a similar level 48 h (10.9 ± 4.3 ml/kg vs. 12.9 ± 4.9 ml/kg; p = 0.25) and 72 h (11.1 ± 5.0 ml/kg vs. 13.9 ± 7.7 ml/kg; p = 0.27) post-ROSC. We found a statistically significant and moderate correlation between no-flow duration and EVLWI 48 h (r = 0.51; p = 0.002) and 72 h (r = 0.54; p = 0.004) post-ROSC. Pulmonary vascular permeability index (PVPI) was not correlated with downtimes. Our observation underlines the presence of cardiac arrest-related lung edema by determination of EVLWI. The duration of no-flow times is a relevant factor for increased extravascular lung water index.

Noninvasive Imaging Methods for Quantification of Pulmonary Edema and Congestion: A Systematic Review

Quantification of pulmonary edema and congestion is important to guide diagnosis and risk stratification, and to objectively evaluate new therapies in heart failure. Herein, we review the validation, diagnostic performance, and clinical utility of noninvasive imaging modalities in this setting, including chest x-ray, lung ultrasound (LUS), computed tomography (CT), nuclear medicine imaging methods (positron emission tomography [PET], single photon emission CT), and magnetic resonance imaging (MRI). LUS is a clinically useful bedside modality, and fully quantitative methods (CT, MRI, PET) are likely to be important contributors to a more accurate and precise evaluation of new heart failure therapies and for clinical use in conjunction with cardiac imaging. There are only a limited number of studies evaluating pulmonary congestion during stress. Taken together, noninvasive imaging of pulmonary congestion provides utility for both clinical and research assessment, and continued refinement of methodologic accuracy, validation, and workflow has the potential to increase broader clinical adoption.

Journal of Clinical Monitoring and Computing 2018-2019 end of year summary: respiration

This paper reviews 28 papers or commentaries published in Journal of Clinical Monitoring and Computing in 2018 and 2019, within the field of respiration. Papers were published covering endotracheal tube cuff pressure monitoring, ventilation and respiratory rate monitoring, lung mechanics monitoring, gas exchange monitoring, CO2 monitoring, lung imaging, and technologies and strategies for ventilation management.

The effects of static and dynamic measurements using transpulmonary thermodilution devices on fluid therapy in septic shock: A systematic review

Transpulmonary thermodilution devices have been widely shown to be accurate in septic shock patients in assessing fluid responsiveness. We conducted a systematic review to assess the relationship between fluid therapy protocols guided by transpulmonary thermodilution devices on fluid balance and the amount of intravenous fluid used in septic shock. We searched MEDLINE, Embase and The Cochrane Library. Studies were eligible for inclusion if they were prospective, parallel trials that were conducted in an intensive care setting in patients with septic shock. The comparator group was either central venous pressure, early goal-directed therapy or pulmonary artery occlusion pressure. Studies assessing only the accuracy of fluid responsiveness prediction by transpulmonary thermodilution devices were excluded. Two reviewers independently performed the search, extracted data and assessed the bias of each study. In total 27 full-text articles were identified for eligibility; of these, nine studies were identified for inclusion in the systematic review. Three of these trials used dynamic parameters derived from transpulmonary thermodilution devices and six used primarily static parameters to guide fluid therapy. There was evidence for a significant reduction in positive fluid balance in four out of the nine studies. From the available studies, the results suggest the benefit of transpulmonary thermodilution monitoring in the septic shock population with regard to reducing positive fluid balance is seen when the devices are utilised for at least 72 hours. Both dynamic and static parameters derived from transpulmonary thermodilution devices appear to lead to a reduction in positive fluid balance in septic shock patients compared to measurements of central venous pressure and early goal-directed therapy.

Lung water assessment: from gravimetry to wearables

Several techniques are now available to detect and quantify pulmonary edema, from the laboratory postmortem method (gravimetry) to non-invasive wearable sensors. In critically ill patients with adult respiratory distress syndrome (ARDS), computed tomography scans are often performed to visualize lung lesions and quantify lung aeration, but their value seems somewhat limited to quantify pulmonary edema on a routine basis and of course to track changes with therapy. In this context, transpulmonary thermodilution is a convenient technique. It is invasive but most patients with ARDS have a central line and an arterial catheter in place. In addition to extravascular lung water measurements, transpulmonary thermodilution enables the measurement of hemodynamic variables that are useful to guide fluid and diuretic therapy. Echo probes are about to replace the stethoscope in our pocket and, if B lines (aka comet tails) do not allow a real quantification of pulmonary edema, they are useful to detect an increase in lung water. Finally, wireless and wearable sensors are now available to monitor patients on hospital wards and beyond (home monitoring). They should enable the detection of pulmonary congestion at a very early stage, and if combined with a proactive therapeutic strategy, have potential to improve outcome.