Measurement Of Extravascular Lung Water Research Articles

Electrical Impedance as a Noninvasive Metric of Quality in Allografts Undergoing Normothermic Ex Vivo Lung Perfusion.

Ex vivo lung perfusion (EVLP) increases the pool of suitable organs for transplant by facilitating assessment and repair at normothermia, thereby improving identification of quality of marginal organs. However, there exists no current objective approach for assessing total organ edema. We sought to evaluate the use of electrical impedance as a metric to assess total organ edema in lungs undergoing EVLP. Adult porcine lungs (40 kg) underwent normothermic EVLP for 4 hours. To induce varying degrees of lung injury, the allografts were perfused with either Steen, a modified cell culture media, or 0.9% normal saline. Physiologic parameters (peak airway pressure and compliance), pulmonary artery and left atrial blood gases, and extravascular lung water measurements were evaluated over time. Wet-to-dry ratios were evaluated postperfusion. Modified Murray scoring was used to calculate lung injury. Impedance values were associated with lung injury scores ( p = 0.007). Peak airway pressure ( p = 0.01) and PaO 2 /FiO 2 ratios ( p = 0.005) were both significantly associated with reduced impedance. Compliance was not associated with impedance ( p = 0.07). Wet/dry ratios were significantly associated with impedance and Murray Scoring within perfusion groups of Steen, Saline, and Modified Cell Culture ( p = 0.0186, 0.0142, 0.0002, respectively). Electrical impedance offers a noninvasive modality for measuring lung quality as assessed by tissue edema in a porcine model of normothermic EVLP. Further studies evaluating the use of impedance to assess organ edema as a quality marker in human clinical models and abdominal organs undergoing ex vivo perfusion warrant investigation.

Sıvı Yönetiminde EVLW ve Önemi

Fluid management and optimization is one of the most frequently observed problems in anesthesiology and critical care. An ideal hemodynamic management increases oxygen supply to tissues, improves postoperative outcomes and decreases surgical costs. Extravascular lung water (EVLW) measurement has gained widespread acceptance in the early prediction and management of adverse effects caused by fluid treatment. The fundamental aim of acute circulatory failure treatment is to improve tissue perfusion and oxygenation while avoiding fluid overload. EVLW consists of extravascular interstitial, intracellular, alveolar and lymphatic fluid in the lungs and its normal values are 3-7 ml kg-1. Studies have reported that values above 10 ml kg-1 as a cut-off value points to pulmonary edema. Although the gold standard in EVLW measurement is the gravimetric method, lung ultrasound and transpulmonary thermodilution is more widely utilized since gravimetric measurement can only be performed post-mortem. EVLW measurement is expected to gain importance in the hemodynamic measurement of ALI/ARDS patients and future studies will benefit from focusing on EVLW based fluid therapy.

Majör Cerrahilerde Ekstravasküler Akciğer Sıvısı Ölçümünün Önemi

The incidence of postoperative pulmonary complications varies between 1-23 % and these complications can cause serious mortality. Measurement of extravascular lung water (EVLW) is beneficial not only for the prevention of complications but also in weaning, fluid management and monitorization of response to pharmacological interventions. EVLW consists of interstitial, intracellular, alveolar and lymphatic fluid in lungs except for pulmonary vasculature. Its normal range is 3-7 m/kg in healthy adults, values greater than 10 ml/kg point to pulmonary edema. Although the gold standard for measurement of EVLW is the gravimetric method, due to the fact it can only be applied postmortem, measurement methods by using ultrasonography and transpulmonary thermodilution have been developed. EVLW measurement can be affected by renal replacement therapy, extracorporeal membrane oxygenation (ECMO), pleural effusions and high PEEP. New research focusing on the effect of EVLW measurement on postoperative hemodynamic management is necessary in the future.

Extravascular Lung Water and Effect on Oxygenation Assessed by Lung Ultrasound in Adult Cardiac Surgery.

IntroductionThe extravascular lung water content is determined by the use of lung ultrasound (LUS) which is represented as B-lines. The aim of this study was to investigate whether the LUS measurement of extravascular lung water was correlated to changes in oxygenation.MethodsThis prospective cohort study was comprised of 73 patients with an average age of 56 (range: 18 to 87 years) who underwent elective cardiac surgery using cardiopulmonary bypass. The LUS score was performed preoperatively, time zero (T0), at one hour (T1), and at 24 hours (T2) post-surgery. Additionally, arterial oxygen partial pressure and fraction of inspired oxygen (PaO2/FiO2) ratio were measured at each time and the time-to-extubation.ResultsA negative correlation was found between the LUS score and PaO2/FiO2 at T1 (p < 0.004). Extubation time and changes in the lung ultrasound score at T0 - T2 were positively correlated (p < 0.03). Plus, there was a positive correlation between fluid balance and lung ultrasound score at T2 (p < 0.03).ConclusionWe found three significant correlations that support the use of LUS in cardiac surgery: 1) the more B-lines, the lower the oxygenation; 2) the more B-lines, the longer the period of ventilation; 3) the more B-lines, the more positive the fluid balance. LUS is a non-invasive bedside investigation that can be used to judge extravascular lung water, providing useful information in the management of patient oxygenation, fluid balance, and extubation.

Does the antisecretory peptide AF-16 reduce lung oedema in experimental ARDS?

Background: Acute respiratory distress syndrome (ARDS) is an acute inflammatory condition with pulmonary capillary leakage and lung oedema formation. There is currently no pharmacologic treatment for the condition. The antisecretory peptide AF-16 reduces oedema in experimental traumatic brain injury. In this study, we tested AF-16 in an experimental porcine model of ARDS.Methods: Under surgical anaesthesia 12 piglets were subjected to lung lavage followed by 2 hours of injurious ventilation. Every hour for 4 hours, measurements of extravascular lung water (EVLW), mechanics of the respiratory system, and hemodynamics were obtained.Results: There was a statistically significant (p = 0.006, two-way ANOVA) reduction of EVLW in the AF-16 group compared with controls. However, this was not mirrored in any improvement in the wet-to-dry ratio of lung tissue samples, histology, inflammatory markers, lung mechanics, or gas exchange.Conclusions: This pilot study suggests that AF-16 might improve oedema resolution as indicated by a reduction in EVLW in experimental ARDS.

Quantitative lung ultrasonography: a putative new algorithm for automatic detection and quantification of B-lines

BackgroundThis pilot study was designed to develop a fully automatic and quantitative scoring system of B-lines (QLUSS: quantitative lung ultrasound score) involving the pleural line and to compare it with previously described semi-quantitative scores in the measurement of extravascular lung water as determined by standard thermo-dilution.MethodsThis was a prospective observational study of 12 patients admitted in the intensive care unit with acute respiratory distress and each provided with 12 lung ultrasound (LUS) frames. Data collected from each patient consisted in five different scores, four semi-quantitative (nLUSS, cLUSS, qLUSS, %LUSS) and quantitative scores (QLUSS). The association between LUS scores and extravascular lung water (EVLW) was determined by simple linear regression (SLR) and robust linear regression (RLR) methods. A correlation analysis between the LUS scores was performed by using the Spearman rank test. Inter-observer variability was tested by computing intraclass correlation coefficient (ICC) in two-way models for agreement, basing on scores obtained by different raters blinded to patients’ conditions and clinical history.ResultsIn the SLR, QLUSS showed a stronger association with EVLW (R2 = 0.57) than cLUSS (R2 = 0.45) and nLUSS (R2 = 0.000), while a lower association than qLUSS (R2 = 0.85) and %LUSS (R2 = 0.72) occurred. By applying RLR, QLUSS showed an association for EVLW (R2 = 0.86) comparable to qLUSS (R2 = 0.85) and stronger than %LUSS (R2 = 0.72). QLUSS was significantly correlated with qLUSS (r = 0.772; p = 0.003) and %LUSS (r = 0.757; p = 0.005), but not with cLUSS (r = 0.561; p = 0.058) and nLUSS (r = 0.105; p = 0.744). Moreover, QLUSS showed the highest ICC (0.998; 95%CI from 0.996 to 0.999) among the LUS scores.ConclusionsThis study demonstrates that computer-aided scoring of the pleural line percentage affected by B-lines has the potential to assess EVLW. QLUSS may have a significant impact, once validated with a larger dataset composed by multiple real-time frames. This approach has the potentials to be advantageous in terms of faster data analysis and applicability to large sets of data without increased costs. On the contrary, it is not useful in pleural effusion or consolidations.

Measurement of extravascular lung water to diagnose severe reperfusion lung injury following pulmonary endarterectomy: a prospective cohort clinical validation study.

SummaryThe measurement of extravascular lung water is a relatively new technology which has not yet been well validated as a clinically useful tool. We studied its utility in patients undergoing pulmonary endarterectomy as they frequently suffer reperfusion lung injury and associated oedematous lungs. Such patients are therefore ideal for evaluating this new monitor. We performed a prospective observational cohort study during which extravascular lung water index measurements were taken before and immediately after surgery and postoperatively in intensive care. Data were analysed for 57 patients; 21 patients (37%) experienced severe reperfusion lung injury. The first extravascular lung water index measurement after cardiopulmonary bypass failed to predict severe reperfusion lung injury, area under the receiver operating characteristic curve 0.59 (95%CI 0.44–0.74). On intensive care, extravascular lung water index correlated most strongly at 36 h, area under the receiver operating characteristic curve 0.90 (95%CI 0.80–1.00). Peri‐operative extravascular lung water index is not a useful measure to predict severe reperfusion lung injury after pulmonary endarterectomy, however, it does allow monitoring and measurement during the postoperative period. This study implies that extravascular lung water index can be used to directly assess pulmonary fluid overload and that monitoring patients by measuring extravascular lung water index during their intensive care stay is useful and correlates with their clinical course. This may allow directed, pre‐empted therapy to attenuate the effects and improve patient outcomes and should prompt further studies.

Quantitative estimation of extravascular lung water volume and preload by dynamic 15O-water positron emission tomography.

Left ventricular filling pressure (preload) can be assessed by pulmonary capillary wedge pressure (PCWP) during pulmonary arterial catheterization (PAC). An emerging method [pulse indexed contour cardiac output (PICCO)] can estimate preload by global end-diastolic volume (GEDV) and congestion as extravascular lung water (EVLW) content. However, no reliable quantitative non-invasive methods are available. Hence, in a porcine model of pulmonary congestion, we evaluated EVLW and GEDV by positron emission tomography (PET). The method was applied in 35 heart failure (HF) patients and 9 healthy volunteers. Eight pigs were studied. Pulmonary congestion was induced by a combination of beta-blockers, angiotensin-2 agonist and saline infusion. PAC, PICCO, computerized tomography, and 15O-H2O-PET were performed. EVLW increased from 521 ± 76 to 973 ± 325 mL (P < 0.001) and GEDV from 1068 ± 170 to 1254 ± 85 mL (P < 0.001). 15O-H2O-PET measures of EVLW increased from 566 ± 151 to 797 ± 231 mL (P < 0.001) and GEDV from 364 ± 60 to 524 ± 92 mL (P < 0.001). Both EVLW and GEDV measured with PICCO and 15O-H2O-PET correlated (r2 = 0.40, P < 0.001; r2 = 0.40, P < 0.001, respectively). EVLW correlated with Hounsfield units (HU; PICCO: r2 = 0.36, P < 0.001, PET: r2 = 0.46, P < 0.001) and GEDV with PCWP (PICCO: r2 = 0.20, P = 0.01, PET: r2 = 0.29, P = 0.002). In human subjects, measurements were indexed (I) for body surface area. Neither EVLWI nor HU differed between chronic stable HF patients and healthy volunteers (P = 0.11, P = 0.29) whereas GEDVI was increased in HF patients (336 ± 66 mL/m2 vs. 276 ± 44 mL/m2, P = 0.01). The present study demonstrates that 15O-H2O-PET can assess pulmonary congestion and preload quantitatively. Hence, prognostic information from 15O-H2O-PET examinations should be evaluated in clinical trials.

Cardiovascular failure and weaning.

Cardiac patients are at high risk of weaning failure due to the abrupt burden to the cardiovascular system resulting from the transition from positive-pressure ventilation to spontaneous breathing. Similarly, numerous patients with borderline cardiac function, left ventricular diastolic dysfunction, chronic obstructive pulmonary disease, especially with associated fluid overload or cumulative positive fluid balance, are at high risk of weaning failure of cardiac origin. The diagnosis of weaning-induced pulmonary oedema (WiPO) relies on the measurement of elevated left ventricular filling pressure, or on the presence of a surrogate reflecting pulmonary or cardiac congestion. Plasma concentration of B-type natriuretic peptide and N-terminal proBNP, biological signs of hemoconcentration (increased circulating protein or hemoglobin levels), or measurement of extravascular pulmonary lung water using transpulmonary thermodilution have been proved valuable surrogates for the identification of weaning failure. Nevertheless, studies have not yet compared these indirect methods to precisely determine their respective diagnostic values for the identification of WiPO, especially in heart failure patients. In addition, none of these approaches directly assess left ventricular filling pressure and the mechanism of WiPO. In contrast, critical care echocardiography is ideally suited to establish the diagnosis of weaning failure of cardiac origin. It allows identifying the high-risk population, monitoring hemodynamically the patient at risk, depicting an abrupt increase of left ventricular filling pressure consistent with WiPO when the patient fails weaning, identifying the underlying mechanism of WiPO, and finally it allows tailoring the therapeutic management of the patient who failed weaning. The impact on patient-centered outcomes of such integrated management strategy based on critical care echocardiography deserves to be prospectively tested in a large population of patients at high risk of weaning failure of cardiac origin.

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.

Extravascular lung water measurements in acute respiratory distress syndrome: why, how, and when?

Purpose of reviewIncrease in pulmonary vascular permeability accompanied with accumulation of excess extravascular lung water (EVLW) is the hallmark of acute respiratory distress syndrome (ARDS). Currently, EVLW and pulmonary vascular permeability index (PVPI) can be quantitatively measured using the transpulmonary thermodilution (TPTD) technique. We will clarify why, how, and when EVLW and PVPI measurements should be performed.Recent findingsAlthough the Berlin criteria of ARDS are simple and widely used, several criticisms of them have been published. The last 2 decades have witnessed the introduction and evolution of the TPTD technique for measuring EVLW and PVPI. Several publications have recommended to evaluate EVLW and the PVPI during the treatment of critically ill patients. Accurate and objective diagnoses can be made for ARDS patients using EVLW and PVPI. EVLW more than 10 ml/kg is a reasonable criterion for pulmonary edema, and EVLW more than 15 ml/kg for a severe condition. In addition to EVLW more than 10 mL/kg, PVPI more than three suggests increased vascular permeability (i.e., ARDS), and PVPI less than 2 represent normal vascular permeability (i.e., cardiogenic pulmonary edema).SummaryEVLW and PVPI measurement will open the door to future ARDS clinical practice and research, and have potential to be included in the future ARDS definition.

Effects of 6% Tetrastarch and Lactated Ringer's Solution on Extravascular Lung Water and Markers of Acute Renal Injury in Hemorrhaged, Isoflurane-Anesthetized Healthy Dogs.

BackgroundTetrastarch can cause acute kidney injury (AKI) in humans with sepsis, but less likely to result in tissue edema than lactated Ringer's solution (LRS).ObjectivesCompare effects of volume replacement (VR) with LRS and 6% tetrastarch solution (TS) on extravascular lung water (EVLW) and markers of AKI in hemorrhaged dogs.AnimalsSix healthy English Pointer dogs (19.7–35.3 kg).MethodsProspective crossover study. Animals underwent anesthesia without hemorrhage (Control). Two weeks later, dogs hemorrhaged under anesthesia on 2 occasions (8‐week washout intervals) and randomly received VR with LRS or TS at 3 : 1 or 1 : 1 of shed blood, respectively. Anesthesia was maintained until 4 hour after VR for EVLW measurements derived from transpulmonary thermodilution cardiac output. Neutrophil gelatinase‐associated lipocalin (NGAL) and creatinine concentrations in plasma and urine were measured until 72 hour after VR.ResultsThe EVLW index (mL/kg) was lower at 1 hour after TS (10.0 ± 1.9) in comparison with controls (11.9 ± 3.4, P = 0.04), and at 4 hour after TS (9.7 ± 1.9) in comparison with LRS (11.8 ± 2.7, P = 0.03). Arterial oxygen partial pressure‐to‐inspired oxygen fraction ratio did not differ among treatments from 0.5 to 4 hour after VR. Urine NGAL/creatinine ratio did not differ among treatments and remained below threshold for AKI (120,000 pg/mg).Conclusions and Clinical ImportanceAlthough TS causes less EVLW accumulation than LRS, neither fluid produced evidence of lung edema (impaired oxygenation). Both fluids appear not to cause AKI when used for VR after hemorrhage in healthy nonseptic dogs.

Extravascular lung water measurement in critically ill patients

In intensive care patients, due to increase in hydrostatic pressure and hyperpermeability state, pulmonary edema occurs. In this review, we discussed about definition and amount of extravascular lung water index (EVLWI) which relates to an increasing pulmonary capillary hydrostatic pressure or increasing capillary permeability. EVLWI-to-intrathoracic blood volume ratio is useful in determining the cause of pulmonary edema. EVLWI can be helpful in approximation of the amount of fluid overload and capillary leak in acute inflammatory injury. This is identified as a prognostic marker that is related to respiratory function and mortality in patients with acute respiratory distress syndrome and sepsis. Usage of EVLWI for determining of pulmonary edema in children would be beneficial.

P6186Quantitative computer tomographic derived measurements of extravascular lung water and left ventricular filling pressure in a porcine model of pulmonary congestion

P6186Quantitative computer tomographic derived measurements of extravascular lung water and left ventricular filling pressure in a porcine model of pulmonary congestion

Evaluation of Reperfusion Pulmonary Edema by Extravascular Lung Water Measurements After Pulmonary Endarterectomy.

Reperfusion pulmonary edema is a specific complication of pulmonary endarterectomy for chronic thromboembolic pulmonary hypertension. Extravascular lung water measurement may be valuable for diagnosing reperfusion pulmonary edema. The primary objective of this study was to describe and assess the clinical significance of extravascular lung water variations after pulmonary endarterectomy. Prospective observational study. Nineteen-bed cardiothoracic ICU. Consecutive patients who were hemodynamically stable after pulmonary endarterectomy were divided into two groups based on whether their preoperative pulmonary vascular resistance indicated severe or nonsevere chronic thromboembolic pulmonary hypertension (> 900 or ≤ 900 dynes·s/cm, respectively). Hemodynamic variables obtained by right heart catheterization and transpulmonary thermodilution measurements were recorded 1 hour, 1 day, and 2 days after pulmonary endarterectomy. Extravascular lung water was indexed to predicted body weight (EVLWPBW). We studied 31 patients. Overall, 26 patients (84%) experienced reperfusion pulmonary edema during the first 72 hours after pulmonary endarterectomy. EVLWPBW significantly increased between the first hour after pulmonary endarterectomy and day 2 (10.2 ± 2.6 vs 11.4 ± 3.6; p = 0.03). EVLWPBW measured at the first hour after pulmonary endarterectomy is closely associated with reperfusion pulmonary edema occurrence in the next 48 hours (area under the receiver-operating characteristics curve = 0.88 ± 0.07). EVLWPBW correlated with duration of mechanical ventilation (ρ = 0.59; p < 0.0001) and ICU stay (ρ = 0.52; p < 0.0001). Patients with severe chronic thromboembolic pulmonary hypertension (n = 15) had higher EVLWPBW values at day 2 compared with those without (n = 16) (13.2 ± 3.6 vs 9.7 ± 2.7 mL/kg; p = 0.004). Cardiac output was measured simultaneously by pulmonary artery catheter and aortic transpulmonary thermodilution on 92 occasions; agreement was good, with a bias of 0.50 ± 0.95 L/min (95% CI, -1.36-2.36). Accurate extravascular lung water measurements were obtained after pulmonary endarterectomy. Extravascular lung water may prove valuable for diagnosing reperfusion pulmonary edema after pulmonary endarterectomy and had prognostic value. Extravascular lung water values were significantly higher in patients with severe compared with nonsevere chronic thromboembolic pulmonary hypertension.

Hemodynamic monitoring in thoracic surgical patients

This article reviews the technology and clinical data describing hemodynamic monitoring devices available to anesthesiologists and intensivists caring for patients undergoing thoracic surgical procedures, so that they may better utilize available technology to improve outcomes in this high-risk surgical population. Noninvasive stroke volume monitors are based on several different technology platforms, all of which have distinct performance characteristics. Strong clinical outcomes data support the use of these devices in patients undergoing major surgical procedures although these studies generally do not target thoracic surgical procedures specifically. The predictive ability of respiratory variation (for measuring fluid responsiveness) is controversial in both one lung and low tidal volume ventilation. Extravascular lung water measurements are well validated, predict postoperative lung function, but require the use of transpulmonary thermodilution. Technology that has been shown to improve clinical outcomes in major surgical procedures is likely applicable to patients undergoing thoracic surgical procedures; however, several unique features of these procedures limit or modify the way in which these devices can be used. Understanding the scientific basis of these devices is the key to using them effectively.

How Useful is Extravascular Lung Water Measurement in Managing Lung Injury in Intensive Care Unit?

Context:The primary goal of septic shock management is optimization of organ perfusion, often at the risk of overloading the interstitium and causing pulmonary edema. The conventionally used end points of resuscitation do not generally include volumetric parameters such as extravascular lung water index (EVLWI) and pulmonary vascular permeability index (PVPI).Aims:This study aimed to assess the prognostic value of EVLWI and PVPI by calculating their correlation with the severity of lung injury.Settings and Design:This prospective observational study included twenty mechanically ventilated critically ill patients with Acute Physiology and Chronic Health Evaluation score (APACHE II) >20.Subjects and Methods:EVLWI and PVPI were measured using transpulmonary thermodilution, and simultaneously, PaO2:FiO2 ratio, alveolar-arterial gradient of oxygen (AaDO2), and chest radiograph scores from two radiologists were obtained.Statistical Analysis:The correlation of EVLWI and PVPI with chest radiograph scores, PaO2:FiO2 ratio, and AaDO2 were calculated. The inter-observer agreement between the two radiologists was tested using kappa test.Results:EVLWI and PVPI correlated modestly with PaO2:FiO2 (r = −0.32, P = 0.0004; r = −0.39, P = 0.0001). There was a better correlation of EVLWI and PVPI with PaO2:FiO2 ratio (r = −0.71, P < 0.0001; r = −0.58, P = 0.0001) in the acute respiratory distress syndrome (ARDS) subgroup. The EVLWI values correlated significantly with corresponding chest radiograph scores (r = 0.71, P < 0.0001 for observer 1 and r = 0.68, P < 0.0001 for observer 2).Conclusions:EVLWI and PVPI may have a prognostic significance in the assessment of lung injury in septic shock patients with ARDS. Further research is required to reveal the usefulness of EVLWI as an end point of fluid resuscitation in the management of septic shock with ARDS.

Ecografía pulmonar para la valoración del agua pulmonar extravascular en el seguimiento de pacientes con edema pulmonar en ventilación mecánica: estudio piloto

BackgroundThe extravascular lung water (EVLW) is the amount of water contained in the lungs, outside the pulmonary vasculature, and is the sum of interstitial, alveolar, intracellular, and lymphatic fluid. Some studies have demonstrated the use of lung ultrasound for the indirect measurement of EVLW. A pilot study was performed to assess the correlation between the measurement of lung water using lung ultrasound and the transpulmonary thermodilution method in mechanically ventilated patients with an established diagnosis of pulmonary oedema. DesignA double-blind pilot study for assessment of a diagnostic technique, over a 6 month period, for evaluating lung ultrasound with the PiCCO™ transpulmonary thermodilution technique for monitoring patients with pulmonary oedema on mechanical ventilation. ResultsA total of 22 lung ultrasound measurements were made with the corresponding evaluation by transpulmonary thermodilution. A correlation was found between the number of “lung comets” (B-lines) and EVLW, r=0.61 (P=.002). ConclusionThere is a positive correlation between the value of EVLW and “pulmonary comets” by ultrasound in patients with an established diagnosis of pulmonary oedema on mechanical ventilation.

Estimation of extravascular lung water using the transpulmonary ultrasound dilution (TPUD) method: a validation study in neonatal lambs.

Increased extravascular lung water (EVLW) may contribute to respiratory failure in neonates. Accurate measurement of EVLW in these patients is limited due to the lack of bedside methods. The aim of this pilot study was to investigate the reliability of the transpulmonary ultrasound dilution (TPUD) technique as a possible method for estimating EVLW in a neonatal animal model. Pulmonary edema was induced in 11 lambs by repeated surfactant lavages. In between the lavages, EVLW indexed by bodyweight was estimated by TPUD (EVLWItpud) and transpulmonary dye dilution (EVLWItpdd) (n = 22). Final EVLWItpud measurements were also compared with EVLWI estimations by gold standard post mortem gravimetry (EVLWIgrav) (n = 6). EVLWI was also measured in two additional lambs without pulmonary edema. Bland–Altman plots showed a mean bias between EVLWItpud and EVLWItpdd of −3.4 mL/kg (LOA ± 25.8 mL/kg) and between EVLWItpud and EVLWIgrav of 1.7 mL/kg (LOA ± 8.3 mL/kg). The percentage errors were 109 and 43 % respectively. The correlation between changes in EVLW measured by TPUD and TPDD was r2 = 0.22. Agreement between EVLWI measurements by TPUD and TPDD was low. Trending ability to detect changes between these two methods in EVLWI was questionable. The accuracy of EVLWItpud was good compared to the gold standard gravimetric method but the TPUD lacked precision in its current prototype. Based on these limited data, we believe that TPUD has potential for future use to estimate EVLW after adaptation of the algorithm. Larger studies are needed to support our findings.

Extravascular lung water in critical care: recent advances and clinical applications.

Extravascular lung water (EVLW) is the amount of fluid that is accumulated in the interstitial and alveolar spaces. In lung oedema, EVLW increases either because of increased lung permeability or because of increased hydrostatic pressure in the pulmonary capillaries, or both. Increased EVLW is always potentially life-threatening, mainly because it impairs gas exchange and reduces lung compliance. The only technique that provides an easy measurement of EVLW at the bedside is transpulmonary thermodilution. The validation of EVLW measurements by thermodilution was based on studies showing reasonable correlations with gravimetry or thermo-dye dilution in experimental and clinical studies. EVLW should be indexed to predicted body weight. This indexation reduces the proportion of ARDS patients for whom EVLW is in the normal range. Compared to non-indexed EVLW, indexed EVLW (EVLWI) is better correlated with the lung injury score and the oxygenation and it is a better predictor of mortality of patients with acute lung injury or acute respiratory distress syndrome (ARDS). Transpulmonary thermodilution also provides the pulmonary vascular permeability index (PVPI), which is an indirect reflection of the integrity of the alveolocapillary barrier. As clinical applications, EVLWI and PVPI may be useful to guide fluid management of patients at risk of fluid overload, as during septic shock and ARDS. High EVLWI and PVPI values predict mortality in several categories of critically ill patients, especially during ARDS. Thus, fluid administration should be limited when EVLWI is already high. Whatever the value of EVLWI, PVPI may indicate that fluid administration is particularly at risk of aggravating lung oedema. In the acute phase of haemodynamic resuscitation during septic shock and ARDS, high EVLWI and PVPI values may warn of the risk of fluid overload and prevent excessive volume expansion. At the post-resuscitation phase, they may prompt initiation of fluid removal thereby achieving a negative fluid balance.