Methods for Qualitative and Quantitative Assessment of Extravascular Lung Water–Clinical Application, Advantages, and Disadvantages

Exercise elicits dynamic changes in extravascular lung water and haemodynamic congestion in heart failure patients with preserved ejection fraction.

Reproducibility of thermal-dye extravascular lung water (EVLW) estimation by a lung water computer was studied by performing ten consecutive measurements in 45 critically ill patients. EVLW ranged over a wide spectrum from 187 to 1163 ml (2.4 to 18.6 ml/kg). The mean coefficient of variation of ten consecutive measurements was 13.6%. Spontaneously breathing patients showed significantly (p less than .05) higher coefficients of variation (16.1 +/- 6.8%) than patients on mechanical ventilation (10.8 +/- 4.2%). Other factors affecting reproducibility could not be clearly identified. Because in lung water estimation mean values of consecutive measurements are compared, we defined an EVLW determination as the mean value of three consecutive EVLW measurements. When comparing consecutive EVLW determinations in hemodynamically stable patients, we found in many that consecutive EVLW determinations varied no more than +/- 15%. These differences probably have to be attributed to the reproducibility of EVLW measurements and have to be considered, when changes in thermal-dye lung water measured by a lung water computer are discussed.

Pulmonary edema is a cardinal feature of the life-threatening condition known as acute respiratory distress syndrome (ARDS). Patients with chronic alcohol abuse are known to be at increased risk of developing and dying from ARDS. Based upon preclinical data, we hypothesized that a history of chronic alcohol abuse in ARDS patients is associated with greater quantities and slower resolution of pulmonary edema compared with ARDS patients without a history of alcohol abuse. A PiCCO transpulmonary thermodilution catheter was inserted into 35 patients within 72 hours of meeting American European Consensus Criteria definition of ARDS. Pulmonary edema was quantified as extravascular lung water (EVLW) and measured for up to 7 days in 13 patients with a history of chronic alcohol abuse and 22 patients without a history of chronic alcohol abuse. Mean EVLW was higher in patients with a history of chronic alcohol abuse (16.6 vs. 10.5 ml/kg, p < 0.0001). Patients with alcohol abuse had significantly greater EVLW over the duration of the study (RM-ANOVA p = 0.003). There was a trend towards slower resolution of EVLW in patients with a history of alcohol abuse (a decrease of 0.5 ml/kg vs. 2.4 ml/kg, p = 0.17) over the study period. A history of alcohol abuse conferred a greater than 3-fold increased risk of elevated EVLW [OR 3.16, (1.26 to 7.93)] using multivariate logistic regression analysis. In patients who develop ARDS, alcohol abuse is associated with greater levels EVLW and a trend towards slower resolution of EVLW. Combined with mechanistic and preclinical evidence linking chronic alcohol consumption and ARDS, targeted therapies should be developed for these patients.

Accurate quantification of extravascular lung water is an important issue in the management of patients with pulmonary edema. The single transpulmonary thermal indicator method has been available since the late 1990s. Its simplicity and easy application make it clinically attractive. Several experimental studies have confirmed the accuracy of the single transpulmonary thermal indicator technique in comparisons with postmortem gravimetric method. Whereas changes in extravascular lung water of less than 100-200% are undetectable by other clinically applicable methods of lung injury assessment (chest radiograph and oxygenation), the single transpulmonary indicator has proven highly sensitive to small (10-20%) increases and is therefore useful to detect incipient pulmonary edema. In patients with sepsis or acute respiratory distress syndrome, extravascular lung water measurement offers information unobtainable by other means. Extravascular lung water can be considered a relevant parameter that contributes to rational management of fluid and vasoactive therapy of many critically ill patients and offers a fuller picture of their overall lung function.

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.

We decided to investigate the pathogenesis of pulmonary ventilatory and radiographic abnormalities in patients after major vascular surgery. Sixteen mechanically ventilated patients without heart failure were studied, within 3 h after major abdominal surgery. We measured extravascular lung water, intrathoracic, global end-diastolic and pulmonary blood volumes, (67)Ga-transferrin pulmonary leak index and ventilatory and radiographic variables. The latter allowed computation of the lung injury score as a measure of lung injury. The extravascular lung water was elevated (>7 mL kg(-1)) in 5 of 16 patients, while the pulmonary leak index was elevated in 11 patients and a supranormal extravascular lung water was associated with a high pulmonary leak index and higher extravascular lung water relative to intrathoracic blood volume or pulmonary blood volume. Patients were arbitrarily divided into those with a lung injury score >1 and < or =1, and only differed in the factors composing the score as well as in extravascular lung water divided by pulmonary blood volume. A lung injury score >1 was associated with a longer duration of mechanical ventilation. Our data suggest that mild, subclinical, pulmonary oedema is relatively common after major vascular surgery, mainly caused by increased pulmonary capillary permeability in the absence of overt heart failure. However, permeability oedema only partially contributes to postoperative lung injury score and need for mechanical ventilation, suggesting a major contribution by atelectasis.

Extra vascular lung water (EVLW) following pulmonary resection increases due to fluid infusion and rises in capillary surface and permeability of the alveolar capillary membranes. EVLW increase clinically correlates to pulmonary oedema and it may generate impairments of gas exchanges and acute lung injury. An early and reliable assessment of postoperative EVLW, especially following major pulmonary resection, is useful in terms of reducing the risk of postoperative complications. The currently used methods, though satisfying these criteria, tend to be invasive and cumbersome and these factors might limit its use. The presence and burden of EVLW has been reported to correlate with sonographic B-line artefacts (BLA) assessed by lung ultrasound (LUS). This observational study investigated if bedside LUS could detect EVLW increases after major pulmonary resection. Due to the clinical association between EVLW increase and impairment of gas exchange, secondary aims of the study included investigating for associations between any observed EVLW increases and both respiratory ratio (PaO2/FiO2) and fluid retention, measured by brain natriuretic peptide (BNP). Overall, 74 major pulmonary resection patients underwent bedside LUS before surgery and at postoperative days 1 and 4, in the inviolate hemithorax which were divided into four quadrants. BLA were counted with a four-level method. The respiratory ratio PaO2/FiO2 and fluid retention were both assessed. BLA resulted being increased at postoperative day 1 (OR 9.25; 95% CI, 5.28-16.20; P<0.0001 vs. baseline), and decreased at day 4 (OR 0.50; 95% CI, 0.31-0.80; P=0.004 vs. day 1). Moreover, the BLA increase was associated with both increased BNP (OR 1.005; 95% CI, 1.003-1.008; P<0.0001) and body weight (OR 1.040; 95% CI, 1.008-1.073; P=0.015). Significant inverse correlations were observed between the BLA values and the PaO2/FiO2 respiratory ratios. Our results suggest that LUS, due to its non-invasiveness, affordability and capacity to detect increases in EVLW, might be useful in better managing postoperative patients.

Fluid balance is important in patients undergoing hemodialysis. "Dry" weight is usually estimated clinically, and also, bioimpedance is considered reliable. Ultrasonography of inferior vena cava (IVC) estimates central venous pressure, and lung ultrasound evaluates extravascular (counting B-lines artifact) lung water. Our study was aimed to clarify their usefulness in the assessment of volume status during hemodialysis. A total of 71 consecutive patients undergoing hemodialysis underwent lung and IVC ultrasound and bioimpedance spectroscopy immediately before and after dialysis. There was a significant reduction in the number of B-lines (3.13 vs 1.41) and in IVC diameters (end-expiratory diameter 1.71 vs 1.37; end-inspiratory diameter 1.19 vs 0.95) during dialysis. The reduction in B-lines correlated with weight reduction during dialysis (p 0.007); none of the parameters concerning the IVC correlated with fluid removal. At the end of the dialysis session, the total number of B-lines correlated with bioimpedance residual weight (p 0.002). The reduction in B-lines correlated with fluid loss due to hemodialysis, despite the small pre-dialysis number, confirming that lung ultrasound can identify even modest variations in extravascular lung water. IVC ultrasound, which reflects the intravascular filling grade, might not be sensitive enough to detect rapid volume decrease. Clinically estimated dry weight had a poor correlation with both bioimpedance and ultrasound techniques. Post-dialysis B-lines number correlates with residual weight assessed with bioimpedance, suggesting a role for ultrasound in managing hemodialysis patients.

Background Lung ultrasound could identify increased levels of extra-vascular lung water (EVLW) in severe preeclampsia (PE) also; increased optic nerve sheath diameter (ONSD) can indirectly reflect intracranial edema that could be a part of PE generalized edema. Our study aimed to evaluate the correlation between ONSD and EVLW in severe PE and to calculate ONSD cutoffs for prediction of pulmonary congestion severity degrees. Methods This prospective cohort study was conducted on 54 consecutively admitted singleton pregnant females complicated with severe preeclampsia from October 2019 to April 2020. Lung ultrasound for quantification of The Echo Comet Score (ECS) and optic nerve ultrasound assessments were performed for all enrolled parturients within 24 h before delivery and at 24 h post-delivery. Results Statistically high significant correlation was found between ECS and ONSD measurements both before and after delivery (r2 = 0.960, p < 0.001 and r2 = 0.847, p < 0.001 for before and after delivery, respectively). Statistically, both ECS and ONSD were highly significant lower at 24 h after delivery compared to the before delivery. The albumin level was statistically highly significant low in patients with severe pulmonary congestion. ONSD measured within 24 hours before delivery with 5.6–6.4 mm in diameter could predict moderate pulmonary congestion with 94.12% sensitivity and 100% specificity and ONSD > 6.4 mm predict severe pulmonary congestion with 100% sensitivity and 94% specificity. Conclusion ONSD is significantly correlated with EVLW in severe preeclampsia and it can predict the degree of pulmonary congestion with cutoff >6.4 mm predicts severe pulmonary congestion.

Caught between a rock and a hard place: seeking an optimal resuscitation strategy for hemorrhaging patients with lung injury.

Extravascular lung water (extravascular lung water, EVLW) is defined as the amount of water accumulated in the interstitial and alveolar space outside the pulmonary vasculature. EVLW is often used to estimate the severity of pulmonary edema in order to guide fluid management, and to predict prognosis of critically ill patients in the ICU. This editorial provides a comprehensive review by focusing the discussion on EVLW assessment, recent advance in clinical application, as well as limitations in critically ill patients. Key words: Extravascular lung water; Septic; Shock; Respiratory distress syndrome

Predictive variables of delayed cerebral ischemia (DCI) and pulmonary edema following subarachnoid hemorrhage (SAH) remain unknown. We aimed to determine associations between transpulmonary thermodilution-derived variables and DCI and pulmonary edema occurrence after SAH. We reviewed 34 consecutive SAH patients monitored by the PiCCO system. Six patients developed DCI at 7 days after SAH on average; 28 did not (non-DCI). We compared the variable measures for 1 day before DCI occurred (DCI day -1) in the DCI group and 6 days after SAH (non-DCI day -1) in the non-DCI group for control. The mean value of the global end-diastolic volume index (GEDI) for DCI day -1 was lower than that for non-DCI day -1 (676 ± 65 vs. 872 ± 85 mL/m, P = 0.04). Central venous pressure (CVP) was not significantly different (7.8 ± 3.1 vs. 9.4 ± 1.9 cm H2O, P = 0.45). At day -1 for both DCI and non-DCI, 11 patients (32%) had pulmonary edema. Global end-diastolic volume index was significantly higher in patients with pulmonary edema than in those without this condition (947 ± 126 vs. 766 ± 81 mL/m, P = 0.02); CVP was not significantly different (8.7 ± 2.8 vs. 9.2 ± 2.1 cm H2O, P = 0.78). Although significant correlation was found between extravascular lung water (EVLW) measures and GEDI (r = 0.58, P = 0.001), EVLW and CVP were not correlated (r = 0.03, P = 0.88). Thus, GEDI might be associated with DCI occurrence and EVLW accumulation after SAH.

The thermal-dye method of lung water measurement is reliable at a low cardiac output

Extravascular lung water in children immediately after operative closure of either isolated atrial septal defect or ventricular septal defect

To test the effects of eicosapentaenoic acid (EPA) infusion on pulmonary edema induced by coronary ligation and reperfusion, extravascular lung water (EVLW) was measured in situ by the thermal-dye double indicator dilution method in dogs. In the control group of five dogs, 30 mL of a 10% soybean oil emulsion was infused through a leg vein. One hour after infusion, the left anterior descending coronary artery below the first diagonal branch was ligated for 15 min and then reperfused for 30 min. In the EPA group, six dogs were similarly treated with an emulsion of a 10% trieicosapentaenoyl-glycerol (90% pure). EVLW, pulmonary capillary wedge pressure, mean pulmonary artery pressure, mean blood pressure, and cardiac index were measured before and 15 min after coronary ligation, and 15 min and 30 min after coronary reperfusion. There were no significant differences in the hemodynamic indices between the two groups. EVLW significantly increased up to two times of baseline during coronary ligation in the control group (P < 0.05) and more during reperfusion (P < 0.01), whereas EVLW did not increase in the EPA group. In conclusion, EPA inhibited EVLW accumulation and may be useful for ameliorating one of the ischemia-reperfusion-induced complications, pulmonary edema.