The measurement of lung water

In vivo evaluation of Andrographis paniculata and Boesenbergia rotunda extract activity against SARS-CoV-2 Delta variant in Golden Syrian hamsters: Potential herbal alternative for COVID-19 treatment

The ongoing COVID-19 pandemic has triggered extensive research, mainly focused on identifying effective therapeutic agents, specifically those targeting highly pathogenic SARS-CoV-2 variants. This study aimed to investigate the in vivo antiviral efficacy and anti-inflammatory activity of herbal extracts derived from Andrographis paniculata and Boesenbergia rotunda, using a Golden Syrian hamster model infected with Delta, a representative variant associated with severe COVID-19. Hamsters were intranasally inoculated with the SARS-CoV-2 Delta variant and orally administered either vehicle control, B. rotunda, or A. paniculata extract at a dosage of 1000 mg/kg/day. Euthanasia was conducted on days 1, 3, and 7 post-inoculation, with 4 animals per group. The results demonstrated that oral administration of A. paniculata extract significantly alleviated both lethality and infection severity compared with the vehicle control and B. rotunda extract. However, neither extract exhibited direct antiviral activity in terms of reducing viral load in the lungs. Nonetheless, A. paniculata extract treatment significantly reduced IL-6 protein levels in the lung tissue (7278 ± 868.4 pg/g tissue) compared to the control (12,495 ± 1118 pg/g tissue), indicating there was a decrease in local inflammation. This finding is evidenced by the ability of A. paniculata extract to reduce histological lesions in the lungs of infected hamsters. Furthermore, both extracts significantly decreased IL-6 and IP-10 mRNA expression in peripheral blood mononuclear cells of infected hamsters compared to the control group, suggesting systemic anti-inflammatory effects occurred. In conclusion, A. paniculata extract's potential therapeutic application for SARS-CoV-2 arises from its observed capacity to lessen inflammatory cytokine concentrations and mitigate lung pathology.

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.

Shock lung is not "wet" but characterized as necroptotic inflammation in a mouse model of hypotension

OBJECTIVES

Hypotension episodes before or after donor brain death are assumed to trigger hypoxia-reoxygenation, causing diffuse alveolar-capillary damage via necrosis. However, alveolar-capillary membranes have direct access to oxygen in alveoli. We hypothesized hypotension-induced lung injury is not diffuse alveolar-capillary damage but interstitial inflammation resulting from nonhypoxic lung ischemia and systemic responses to hypoxic extrapulmonary ischemia.

METHODS

The 4-hour hypotension model was established by subjecting C57BL/6J mice to 4-hour hypotension at 15 ± 5 mm Hg of mean artery pressure and resuscitated with whole shed blood and norepinephrine. Nonhypoxic lung ischemia model was established by 4-hour left pulmonary artery ligation. At 24 hours postprocedure, an arterial blood gas analysis and a gastroduodenal occult blood test were conducted. Lung samples were assessed for histology, cytokine transcripts, regulated cell death, and alveolar-capillary permeability.

RESULTS

The 4-hour hypotension model had an intraoperative mortality rate of 17.7% (41/231) and a stress-ulcer bleeding rate of 15.3% (29/190). No signs of alveolar flooding were observed in both models. Four-hour hypotension without stress ulcer showed normal oxygenation and permeability but increased interstitial infiltration, transcription of Tnf and Il1b, phosphorylation of MLKL and RIPK3, and cleaved caspase 3 compared with 4-hour pulmonary artery ligation and naïve control. Animals that developed stress ulcer presented with worse pulmonary infiltration, intracellular edema, and oxygenation but just slightly increased permeability. Immunoblotting showed significant upregulations of protein expression and phosphorylation of MLKL and RIPK3, cleaved Caspase-3, but not its prototype in 4-hour hypotension with stress ulcer.

CONCLUSIONS

Hypotensive lung injury is essentially a nonhypoxic ischemia-reperfusion injury enhanced by systemic responses. It is predominated by necroptosis-induced inflammation rather than necrosis-induced diffuse alveolar-capillary damage.

Whole-lung finite-element models for mechanical ventilation and respiratory research applications

Mechanical ventilation has been a vital treatment for Covid-19 patients with respiratory failure. Lungs assisted with mechanical ventilators present a wide variability in their response that strongly depends on air-tissue interactions, which motivates the creation of simulation tools to enhance the design of ventilatory protocols. In this work, we aim to create anatomical computational models of the lungs that predict clinically-relevant respiratory variables. To this end, we formulate a continuum poromechanical framework that seamlessly accounts for the air-tissue interaction in the lung parenchyma. Based on this formulation, we construct anatomical finite-element models of the human lungs from computed-tomography images. We simulate the 3D response of lungs connected to mechanical ventilation, from which we recover physiological parameters of high clinical relevance. In particular, we provide a framework to estimate respiratory-system compliance and resistance from continuum lung dynamic simulations. We further study our computational framework in the simulation of the supersyringe method to construct pressure-volume curves. In addition, we run these simulations using several state-of-the-art lung tissue models to understand how the choice of constitutive models impacts the whole-organ mechanical response. We show that the proposed lung model predicts physiological variables, such as airway pressure, flow and volume, that capture many distinctive features observed in mechanical ventilation and the supersyringe method. We further conclude that some constitutive lung tissue models may not adequately capture the physiological behavior of lungs, as measured in terms of lung respiratory-system compliance. Our findings constitute a proof of concept that finite-element poromechanical models of the lungs can be predictive of clinically-relevant variables in respiratory medicine.

The Association Between Extravascular Lung Water and Critical Care Outcomes Following Bilateral Lung Transplantation

Primary graft dysfunction (PGD) is a form of acute respiratory failure that complicates 30% of bilateral lung transplants. Higher grades of PGD correlate with higher severity of respiratory failure and unfavorable outcomes. Immediate PGD determination posttransplant‚ however, is not always predictive of PGD over subsequent days or intensive care unit outcomes. We aimed to evaluate whether extravascular lung water index (ELWI) measured immediately post bilateral lung transplant was associated with higher severity of PGD at 72 h and duration of mechanical ventilation.

Orally delivered MK-4482 inhibits SARS-CoV-2 replication in the Syrian hamster model

The COVID-19 pandemic progresses unabated in many regions of the world. An effective antiviral against SARS-CoV-2 that could be administered orally for use following high-risk exposure would be of substantial benefit in controlling the COVID-19 pandemic. Herein, we show that MK-4482, an orally administered nucleoside analog, inhibits SARS-CoV-2 replication in the Syrian hamster model. The inhibitory effect of MK-4482 on SARS-CoV-2 replication is observed in animals when the drug is administered either beginning 12 h before or 12 h following infection in a high-risk exposure model. These data support the potential utility of MK-4482 to control SARS-CoV-2 infection in humans following high-risk exposure as well as for treatment of COVID-19 patients.

Hydroxychloroquine prophylaxis and treatment is ineffective in macaque and hamster SARS-CoV-2 disease models

We remain largely without effective prophylactic/therapeutic interventions for COVID-19. Although many human COVID-19 clinical trials are ongoing, there remains a deficiency of supportive preclinical drug efficacy studies to help guide decisions. Here we assessed the prophylactic/therapeutic efficacy of hydroxychloroquine (HCQ), a drug of interest for COVID-19 management, in 2 animal disease models. The standard human malaria HCQ prophylaxis (6.5 mg/kg given weekly) and treatment (6.5 mg/kg given daily) did not significantly benefit clinical outcome, nor did it reduce SARS-CoV-2 replication/shedding in the upper and lower respiratory tract in the rhesus macaque disease model. Similarly, when used for prophylaxis or treatment, neither the standard human malaria dose (6.5 mg/kg) nor a high dose (50 mg/kg) of HCQ had any beneficial effect on clinical disease or SARS-CoV-2 kinetics (replication/shedding) in the Syrian hamster disease model. Results from these 2 preclinical animal models may prove helpful in guiding clinical use of HCQ for prophylaxis/treatment of COVID-19.

Validation of radiofrequency determined lung fluid using thoracic CT: Findings in acute decompensated heart failure patients

Background

Noninvasive outpatient monitoring for heart failure (HF) has significant opportunity to reduce patient morbidity and the costs associated with recurrent hospitalization. The purpose of this study was to validate the ability of radiofrequency (RF) to assess lung fluid via a wearable patch device compared to thoracic CT in order to characterize volume overload.

Methods

120 subjects were studied: 66 acute heart failure (AHF) inpatients and 54 subjects without AHF (Control – 44 healthy and 10 stable HF). All underwent supine thoracic CT scans and supine RF readings from the wearable patch device placed on the left mid-axillary line (age = 74 ± 16 vs. 57 ± 15 yrs.; female = 38 vs. 44%; BMI = 33.2 ± 9.0 vs. 27.3 ± 5.1, AHF vs. Control respectively). Reflected RF signals and subject-specific anthropometric data were used to calculate the RF-determined lung fluid content. CT Lung fluid was reported as percentage of lung volume. Classification analyses were used to compare RF and CT performance.

Results

AHF presented with higher lung fluid than controls by both CT and RF (CT: 20.1 ± 4.2% vs. 15.4 ± 2.4%; RF: 20.7 ± 5.6% vs. 15.6 ± 3.3%; p < 0.05 for all). The correlation between lung fluid measured by CT vs. RF was r = 0.7 (p < 0.001). RF determined lung fluid performed as well as CT in distinguishing AHF from control subjects: Sensitivity: 70% vs. 86%; Specificity: 82% vs. 83%; Positive Predictive Value: 82% vs. 86%; Negative Predictive Value: 69% vs. 83%, CT vs. RF respectively.

Conclusions

Noninvasive nonionizing RF determined lung fluid provides a potential alternative to other measures for diagnosing and monitoring pulmonary fluid overload.

Orally delivered MK-4482 inhibits SARS-CoV-2 replication in the Syrian hamster model

The COVID-19 pandemic progresses unabated in many regions of the world. An effective antiviral against SARS-CoV-2 that could be administered orally for use following high-risk exposure would be of substantial benefit in controlling the COVID-19 pandemic. Herein, we show that MK-4482, an orally administered nucleoside analog, inhibits SARS-CoV-2 replication in the Syrian hamster model. The inhibitory effect of MK-4482 on SARS-CoV-2 replication was observed in animals when the drug was administered either beginning 12 hours before or 12 hours following infection in a high-risk exposure model. These data support the potential utility of MK-4482 to control SARS-CoV-2 infection in humans following high-risk exposure as well as for treatment of COVID-19 patients.

Hydroxychloroquine Proves Ineffective in Hamsters and Macaques Infected with SARS-CoV-2

We remain largely without effective prophylactic/therapeutic interventions for COVID-19. Although many human clinical trials are ongoing, there remains a deficiency of supportive preclinical drug efficacy studies. Here we assessed the prophylactic/therapeutic efficacy of hydroxychloroquine (HCQ), a drug of interest for COVID-19 management, in two animal models. When used for prophylaxis or treatment neither the standard human malaria dose (6.5 mg/kg) nor a high dose (50 mg/kg) of HCQ had any beneficial effect on clinical disease or SARS-CoV-2 kinetics (replication/shedding) in the Syrian hamster disease model. Similarly, HCQ prophylaxis/treatment (6.5 mg/kg) did not significantly benefit clinical outcome nor reduce SARS-CoV-2 replication/shedding in the upper and lower respiratory tract in the rhesus macaque disease model. In conclusion, our preclinical animal studies do not support the use of HCQ in prophylaxis/treatment of COVID-19.

Relationship Between Noninvasive Assessment of Lung Fluid Volume and Invasively Measured Cardiac Hemodynamics

Background

Right heart catheterization is the gold standard in clinical practice for the assessment of cardiovascular hemodynamics, but it is an invasive procedure requiring expertise in both insertion and reading. Remote dielectric sensing (ReDS) is a noninvasive electromagnetic‐based technology intended to quantify lung fluid content.

Methods and Results

In this prospective single‐center study, ReDS readings were obtained in supine position just before right heart catheterization procedure in patients with heart failure. Agreement between ReDS and pulmonary artery wedge pressure (PAWP) was analyzed. Of all, 139 patients with heart failure received hemodynamic assessment and ReDS measurement. A good correlation was found between ReDS and PAWP measurement (r=0.492, P<0.001). Receiver operating characteristic analysis of the ability to identify a PAWP ≥18 mm Hg resulted in a ReDS cutoff value of 34%, with an area under the curve of 0.848, a sensitivity of 90.7%, and a specificity of 77.1%. Overall, ReDS <34% carries a high negative predictive value of 94.9%.

Conclusions

Lung fluid content, as measured by ReDS, correlates well with PAWP. The high sensitivity and specificity and especially the high negative predictive value make ReDS a reliable noninvasive tool at the point of care, to rule out elevated PAWP in patients with heart failure and to help with medical management of patients with heart failure. Further studies are warranted to compare this tool with existing tests and to relate the findings to the clinical outcomes.

Role of Lung Ultrasound in Adjusting Ultrafiltration Volume in Hemodialysis Patients

Chronic fluid over-hydration is common in dialysis patients. It is associated with mortality and cardiovascular events. Optimal methods for adjusting fluid volume status and ideal dry weight remain uncertain. The purpose of this study was to evaluate the usefulness of ultrasound in quantifying body water. In 35 hemodialysis patients, we performed ultrasound of the chest, pre-tibial skin tissue thickness (TT), heart and inferior vena cava (IVC) before and after dialysis. We compared B-line scores of lungs, IVC diameters and cardiac functions in pre-dialysis and post-dialysis groups. We then estimated the correlations between ultrasound parameters and ultrafiltration volumes. Ultrafiltration parameters were adjusted prospectively for subsequent dialysis. As a result, both extravascular and intravascular water decreased during ultrafiltration. The median numbers of B-line scores (10 [0-42] vs. 4 [0-30]; p < 0.001); mitral valve blood flow velocities E (0.83 ± 0.23 m/s vs. 0.70 ± 0.20 m/s; p < 0.001), A (0.93 ± 0.28 vs. 0.89 ± 0.23 m/s; p < 0.001) and E/e' (12.47 ± 4.92 vs. 10.37 ± 4.0; p < 0.001); IVC diameters at end-expiration (17.51 ± 3.33 mm vs. 14.26 ± 3.45 mm; p < 0.001); and right pre-tibial TT (2.86 ± 1.36 mm vs. 2.43 ± 1.24 mm; p < 0.001) decreased during dialysis. Ultrafiltration volume was most associated with B-line score (adjusting for age and sex) (β = -3.340; p = 0.003). In addition, the B-line score after dialysis was significantly associated with left ventricular ejection fraction (r = -0.393; p = 0.019) and TT (r = -0.447; p = 0.007). Ultrafiltration volume was prospectively increased then if the B-line score was >6 in the previous dialysis. All patients tolerated the protocol well without any symptoms. Ultrafiltration volume was most associated with lung water, reflected by variation in B-line score. It was not associated with cardiac function, IVC diameter, IVC collapse rate or TT. Lung ultrasound is a useful imaging tool for dialysis patients.

Usefulness of radiological signs of pulmonary congestion in predicting failed spontaneous breathing trials

Objective:

Inspiratory fall in intrathoracic pressure during a spontaneous breathing trial (SBT) may precipitate cardiac dysfunction and acute pulmonary edema. We aimed to determine the relationship between radiological signs of pulmonary congestion prior to an SBT and weaning outcomes.

Methods:

This was a post hoc analysis of a prospective cohort study involving patients in an adult medical-surgical ICU. All enrolled individuals met the eligibility criteria for liberation from mechanical ventilation. Tracheostomized subjects were excluded. The primary endpoint was SBT failure, defined as the inability to tolerate a T-piece trial for 30-120 min. An attending radiologist applied a radiological score on interpretation of digital chest X-rays performed before the SBT.

Results:

A total of 170 T-piece trials were carried out; SBT failure occurred in 28 trials (16.4%), and 133 subjects (78.3%) were extubated at first attempt. Radiological scores were similar between SBT-failure and SBT-success groups (median [interquartile range] = 3 [2-4] points vs. 3 [2-4] points; p = 0.15), which, according to the score criteria, represented interstitial lung congestion. The analysis of ROC curves demonstrated poor accuracy (area under the curve = 0.58) of chest x-rays findings of congestion prior to the SBT for discriminating between SBT failure and SBT success. No correlation was found between fluid balance in the 48 h preceding the SBT and radiological score results (ρ = −0.13).

Conclusions:

Radiological findings of pulmonary congestion should not delay SBT indication, given that they did not predict weaning failure in the medical-surgical critically ill population.

(ClinicalTrials.gov identifier: NCT02022839 [http://www.clinicaltrials.gov/])

A Simplified Ultrasound Comet Tail Grading Scoring to Assess Pulmonary Congestion in Patients with Heart Failure

Ultrasound lung comets (ULCs) are a nonionizing bedside approach to assess extravascular lung water. We evaluated a protocol for grading ULC score to estimate pulmonary congestion in heart failure patients and investigated clinical and echocardiographic correlates of the ULC score. Ninety-three patients with congestive heart failure, admitted to the emergency department, underwent pulmonary ultrasound and echocardiography. A ULC score was obtained by summing the ULC scores of 7 zones of anterolateral chest scans. The results of ULC score were compared with echocardiographic results, the New York Heart Association (NYHA) functional classification, radiologic score, and N-terminal pro-b-type natriuretic peptide (NT-proBNP). Positive linear correlations were found between the 7-zone ULC score and the following: E/e′, systolic pulmonary artery pressure, severity of mitral regurgitation, left ventricular global longitudinal strain, NYHA functional classification, radiologic score, and NT-proBNP. However, there was no significant correlation between ULC score and left ventricular ejection fraction, left ventricle diameter, left ventricular volume, or left atrial volume. A multivariate analysis identified the E/e′, systolic pulmonary artery pressure, and radiologic score as the only independent variables associated with ULC score increase. The simplified 7-zone ULC score is a rapid and noninvasive method to assess lung congestion. Diastolic rather than systolic performance may be the most important determinant of the degree of lung congestion in patients with heart failure.

Evaluating Extravascular Lung Water in Sepsis: Three Lung-Ultrasound Techniques Compared against Transpulmonary Thermodilution

Background:

Excessive extravascular lung water (EVLW) is associated with increased morbidity and mortality. We compared three lung-ultrasound (L-US) techniques against the reference-standard transpulmonary thermodilution (TPTD) technique to access EVLW.

Materials and Methods:

This was a prospective, single-blind, cross-sectional study. Forty-four septic patients were enrolled. EVLW index was measured by the TPTD method, and an index of ≥10 mL/kg was considered diagnostic of pulmonary edema. EVLW index was then compared to three established bedside L-US protocols that evaluate sonographic B-lines: (1) a 28-zone protocol (total B-line score [TBS]) (2) a scanning 8-region examination, and (3) a 4-point examination.

Results:

Eighty-nine comparisons were obtained. A statistically significant positive correlation was found between L-US TBS and an EVLW index ≥10 mL/kg (r = 0.668,P < 0.001). The 28-zone protocol score ≥39 has a sensitivity of 81.6% and a specificity of 76.5% to define EVLW index ≥10 mL/kg. In contrast, the positive 4-point examination and scanning 8-regions showed low sensitivity (23.7% and 50.0%, respectively) but high specificity (96.1% and 88.2%, respectively). Ten patients with a total of 21 comparisons met criteria for acute respiratory distress syndrome (ARDS). In this subgroup, only the TBS had statistically significant positive correlation to EVLW (r = 0.488,P = 0.025).

Conclusion:

L-US is feasible in patients with severe sepsis. In addition, L-US 28-zone protocol demonstrated high specificity and better sensitivity than abbreviated 4- and 8-zone protocols. In ARDS, the L-US 28-zone protocol was more accurate than the 4- and 8-zone protocols in predicting EVLW. Consideration of limitations of the latter protocols may prevent clinicians from reaching premature conclusions regarding the prediction of EVLW.

Trial Registration:

ISRCTN11419081. Registered 4 February 2015 retrospectively.

Lung liquid clearance in preterm lambs assessed by magnetic resonance imaging

BACKGROUND

Postnatal adaptation requires liquid clearance and lung aeration. However, their relative contribution to the expansion of functional residual capacity (FRC) has not been fully investigated. We studied evolution of lung liquid removal and lung aeration after birth in preterm lambs.

METHODS

Lung liquid content and lung volume were assessed at birth and every 30 min over 2 h using magnetic resonance imaging (MRI) in three groups of lambs delivered by cesarean: preterm, late preterm, and late preterm with antenatal steroids. Lung function and mechanics of the respiratory system were also measured.

RESULTS

Lung liquid content increased by approximately 30% in the preterm group (P < 0.05), whereas it did not change significantly in the late preterm lambs. Antenatal steroids induced a 50% drop in the lung liquid content (P < 0.05). Total lung volume increased in all groups (P < 0.05) but was higher in the late preterm + steroids group relative to other groups (P < 0.05). Compliance and resistances of the respiratory system were significantly correlated with lung liquid content (P < 0.05).

CONCLUSION

FRC expansion results mainly from an increase in lung volume rather than a decrease in lung liquid in preterm and late preterm lambs. Antenatal steroids promote FRC expansion through increases in lung volume and liquid clearance.

Assessment of extravascular lung water by ultrasound after congenital cardiac surgery

BACKGROUND

Lung ultrasounds show vertical artifacts known as B-lines in the presence of increased extravascular lung water (EVLW). We aimed to investigate whether lung ultrasound could estimate EVLW after congenital cardiac surgery.

METHODS

This prospective observational study comprised 61 children (age range 3 days to 7.4 years) undergoing congenital cardiac surgery. We compared postoperative B-line scores from lung ultrasounds, early postoperative ultrasound as our primary interest, with corresponding postoperative chest radiography (CXR) lung edema scores, with static lung compliance, and with short-term clinical outcome interpreted as time on mechanical ventilation and length of pediatric intensive care unit (PICU) stay.

RESULTS

Our findings showed lung ultrasound B-line scores and CXR lung edema scores as correlating 1-6 hr postoperatively (r²  = 0.41, P < 0.0001), on the first postoperative day (r²  = 0.15, P = 0.004) and on the fourth postoperative day (r²  = 0.28, P = 0.008). The B-line score or CXR lung edema score showed no correlation with lung compliance. We found that in multivariable analyses, with length of perfusion and presence of postoperative complications as covariates, both lung ultrasound (P ≤ 0.02) and CXR (P ≤ 0.002) 1-6 hr postoperatively predicted the length of mechanical ventilation and PICU stay. The interobserver variability was less for lung ultrasound B-line score than for CXR lung edema score (P = 0.001).

CONCLUSIONS

Our results show that lung ultrasound in assessment of postoperative EVLW predicted length of mechanical ventilation and stay in the PICU, and it had less interobserver variability than CXR. Accordingly, lung ultrasound may complement CXR in assessment of lung edema after surgery for congenital heart defect. Pediatr Pulmonol. 2017;52:345-352. © 2016 Wiley Periodicals, Inc.

Chronic Hypoxemia in Children With Congenital Heart Defect Impairs Airway Epithelial Sodium Transport

OBJECTIVE

Ambient hypoxia impairs the airway epithelial Na transport, which is crucial in lung edema reabsorption. Whether chronic systemic hypoxemia affects airway Na transport has remained largely unknown. We have therefore investigated whether chronic systemic hypoxemia in children with congenital heart defect affects airway epithelial Na transport, Na transporter-gene expression, and short-term lung edema accumulation.

DESIGN

Prospective, observational study.

SETTING

Tertiary care medical center responsible for nationwide pediatric cardiac surgery.

PATIENTS

Ninety-nine children with congenital heart defect or acquired heart disease (age range, 6 d to 14.8 yr) were divided into three groups based on their level of preoperative systemic hypoxemia: 1) normoxemic patients (SpO2% ≥ 95%; n = 44), 2) patients with cyanotic congenital heart defect and moderate hypoxemia (SpO2 86-94%; n = 16), and 3) patients with cyanotic congenital heart defect and profound systemic hypoxemia (SpO2 ≤ 85%; n = 39).

MEASUREMENTS AND MAIN RESULTS

Nasal transepithelial potential difference served as a surrogate measure for epithelial Na transport of the respiratory tract. Profoundly hypoxemic patients had 29% lower basal nasal transepithelial potential difference (p = 0.02) and 55% lower amiloride-sensitive nasal transepithelial potential difference (p = 0.0003) than normoxemic patients. In profoundly hypoxemic patients, nasal epithelial messenger RNA expressions of two airway Na transporters (amiloride-sensitive epithelial Na channel and β1- Na-K-ATPase) were not attenuated, but instead α1-Na-K-ATPase messenger RNA levels were higher (p = 0.03) than in the normoxemic patients, indicating that posttranscriptional factors may impair airway Na transport. The chest radiograph lung edema score increased after congenital cardiac surgery in profoundly hypoxemic patients (p = 0.0004) but not in patients with normoxemia or moderate hypoxemia.

CONCLUSIONS

The impaired airway epithelial amiloride-sensitive Na transport activity in profoundly hypoxemic children with cyanotic congenital heart defect may hinder defense against lung edema after cardiac surgery.

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.

Ultrashort echo time MRI of pulmonary water content: assessment in a sponge phantom at 1.5 and 3.0 Tesla

PURPOSE

We aimed to develop a predictive model for lung water content using ultrashort echo time (UTE) magnetic resonance imaging (MRI) and a sponge phantom.

MATERIALS AND METHODS

Image quality was preliminarily optimized, and the signal-to-noise ratio (SNR) of UTE was compared with that obtained from a three-dimensional fast gradient echo (FGRE) sequence. Four predetermined volumes of water (3.5, 3.0, 2.5, and 2.0 mL) were soaked in cellulose foam sponges 1.8 cm3 in size and were imaged with UTE-MRI at 1.5 and 3.0 Tesla (T). A multiple echo time experiment (range, 0.1-9.6 ms) was conducted, and the T2 signal decay curve was determined at each volume of water. A three-parameter equation was fitted to the measured signal, allowing for the calculation of proton density and T2*. The calculation error of proton density was determined as a function of echo time. The constants that allowed for the determination of unknown volumes of water from the measured proton density were calculated using linear regression.

RESULTS

UTE-MRI provided excellent image quality for the four phantoms and showed a higher SNR, compared to that of FGRE. Proton density decreased proportionally with the decreases in both lung water and field strength (from 3.5 to 2.0 mL; proton density range at 1.5 T, 30.5-17.3; at 3.0 T, 84.2-41.5). Minimum echo time less than 0.6 ms at 1.5 T and 1 ms at 3.0 T maintained calculation errors for proton density within the range of 0%-10%. The slopes of the lines for determining the unknown volumes of water with UTE-MRI were 0.12±0.003 at 1.5 T and 0.05±0.002 at 3.0 T (P < 0.0001).

CONCLUSION

In a sponge phantom imaged at 1.5 and 3.0 T, unknown volumes of water can be predicted with high accuracy using UTE-MRI.

Comparison of thermodilution measured extravascular lung water with chest radiographic assessment of pulmonary oedema in patients with acute lung injury

Background

Acute lung injury and the acute respiratory distress syndrome (ALI/ARDS) are characterized by pulmonary oedema, measured as extravascular lung water (EVLW). The chest radiograph (CXR) can potentially estimate the quantity of lung oedema while the transpulmonary thermodilution method measures the amount of EVLW. This study was designed to determine whether EVLW as estimated by a CXR score predicts EVLW measured by the thermodilution method and whether changes in EVLW by either approach predict mortality in ALI/ARDS.

Methods

Clinical data were collected within 48 hours of ALI/ARDS diagnosis and daily up to 14 days on 59 patients with ALI/ARDS. Two clinicians scored each CXR for the degree of pulmonary oedema, using a validated method. EVLW indexed to body weight was measured using the single indicator transpulmonary thermodilution technique.

Results

The CXR score had a modest, positive correlation with the EVLWI measurements (r = 0.35, p < 0.001). There was a 1.6 ml/kg increase in EVLWI per 10-point increase in the CXR score (p < 0.001, 95% confidence interval 0.92-2.35). The sensitivity of a high CXR score for predicting a high EVLWI was 93%; similarly the negative predictive value was high at 94%; the specificity (51%) and positive predictive value (50%) were lower. The CXR scores did not predict mortality but the EVLW thermodilution did predict mortality.

Conclusion

EVLW measured by CXR was modestly correlated with thermodilution measured EVLW. Unlike CXR findings, transpulmonary thermodilution EVLWI measurements over time predicted mortality in patients with ALI/ARDS.

Ulinastatin suppresses burn-induced lipid peroxidation and reduces fluid requirements in a Swine model

Objective. Lipid peroxidation plays a critical role in burn-induced plasma leakage, and ulinastatin has been reported to reduce lipid peroxidation in various models. This study aims to examine whether ulinastatin reduces fluid requirements through inhibition of lipid peroxidation in a swine burn model. Methods. Forty miniature swine were subjected to 40% TBSA burns and were randomly allocated to the following four groups: immediate lactated Ringer's resuscitation (ILR), immediate LR containing ulinastatin (ILR/ULI), delayed LR resuscitation (DLR), and delayed LR containing ulinastatin (DLR/ULI). Hemodynamic variables, net fluid accumulation, and plasma thiobarbituric acid reactive substances (TBARS) concentrations were measured. Heart, liver, lung, skeletal muscle, and ileum were harvested at 48 hours after burn for evaluation of TBARS concentrations, activities of antioxidant enzymes, and tissue water content. Results. Ulinastatin significantly reduced pulmonary vascular permeability index (PVPI) and extravascular lung water index (ELWI), net fluid accumulation, and water content of heart, lung, and ileum in both immediate or delayed resuscitation groups. Furthermore, ulinastatin infusion significantly reduced plasma and tissue concentrations of TBARS in both immediate or delayed resuscitation groups. Conclusions. These results indicate that ulinastatin can reduce fluid requirements through inhibition of lipid peroxidation.

A novel approach to monitoring pulmonary congestion in heart failure: initial animal and clinical experiences using remote dielectric sensing technology

Despite current therapies and disease management approaches, rates of heart failure (HF) rehospitalization remain high. New tools are needed to assess preclinical (asymptomatic) pulmonary congestion to enable outpatient management. Hence, a novel monitoring system based on noninvasive remote dielectric sensing (ReDS) technology was developed. Validation of the ReDS technology was conducted in preclinical and clinical studies. In a porcine HF model, acute fluid overload followed by administration of diuretics were performed. Changes in ReDS values were correlated to serial computed tomographic (CT) assessments of lung fluid concentrations. In hospitalized decompensated HF patients, changes in ReDS values were correlated to net fluid balance changes. A nearly linear pattern between the changes in ReDS and CT fluid concentration values was observed in 6 discrete experiments (Intraclass correlation=0.95). Results from 24 patients demonstrated a reduction in ReDS values of 17.53%±11% throughout hospitalization, consistent with a reduction in pulmonary congestion. This finding strongly correlated with changes in net fluid balance (Pearson correlation=0.86; 95% confidence interval, 0.68-0.94; R(2) =0.74). These findings suggest that ReDS technology accurately quantifies lung fluid concentration and has potential for monitoring HF patients through hospitalization and possibly at home.

Clinical review: Respiratory monitoring in the ICU - a consensus of 16

Monitoring plays an important role in the current management of patients with acute respiratory failure but sometimes lacks definition regarding which 'signals' and 'derived variables' should be prioritized as well as specifics related to timing (continuous versus intermittent) and modality (static versus dynamic). Many new techniques of respiratory monitoring have been made available for clinical use recently, but their place is not always well defined. Appropriate use of available monitoring techniques and correct interpretation of the data provided can help improve our understanding of the disease processes involved and the effects of clinical interventions. In this consensus paper, we provide an overview of the important parameters that can and should be monitored in the critically ill patient with respiratory failure and discuss how the data provided can impact on clinical management.

Injection of deuterated water into the pulmonary/alveolar circulation; measurement of HDO in exhaled breath and implications to breath analysis

The results of experiments are described in which a known quantity of sterile deuterated water is injected directly into the pulmonary circulation via the right internal jugular vein of several haemodialysis patients and the deuterium to hydrogen ratio, D/H, in the exhaled lung water was measured using the flowing afterglow mass spectrometry technique. The breath D/H abundance was measured in sequential breath exhalations before and after the injection, providing data that are sufficiently detailed to follow the production and loss rate of D/H in the exhaled breath. Thus, in principle, considering isotope dilution the volume of water in the lungs and pulmonary circulation can be derived. However, it is seen that the maximum abundance that the breath D/H reached was much lower than anticipated by considering the likely volume of blood/water in the pulmonary circulation and so it is deduced that either 'leakage' of the injected deuterated water rapidly occurs from the pulmonary to the systemic circulation and/or isotope exchange of deuterium with hydrogen along the bronchial tree efficiently occurs, thus reducing the D/H in the exhaled breath. This latter phenomenon has important implications to breath analysis in which it is often assumed that so-called alveolar breath concentrations of metabolites reflect blood/systemic levels. Detailed consideration of the breath D/H abundances when the deuterium is equilibrated amongst the total body water, TBW, of the patients, which occurs about 40 min after injection of the deuterated water, allows the TBW of the patients to be estimated.

Lung ultrasound in diagnosing and monitoring pulmonary interstitial fluid

Chronic heart failure is a complex clinical syndrome often characterised by recurrent episodes of acute decompensation. This is acknowledged as a major public health problem, leading to a steadily increasing number of hospitalisations in developed countries. In decompensated heart failure, the redistribution of fluids into the pulmonary vascular bed leads to respiratory failure, a common cause of presentation to the emergency department. The ability to diagnose, quantify and monitor pulmonary congestion is particularly important in managing the disease. Lung ultrasound (US) is a relatively new method that has gained a growing acceptance as a bedside diagnostic tool to assess pulmonary interstitial fluid and alveolar oedema. The latest developments in lung US are not because of technological advance but are based on new applications and discovering the meanings of specific sonographic artefacts designated as B-lines. Real-time sonography of the lung targeted to detection of B-lines allows bedside diagnosis of respiratory failure due to impairment of cardiac function, as well as quantification and monitoring of pulmonary interstitial fluid. Lung US saves time and cost, provides immediate information to the clinician and relies on very easy-to-acquire and highly reproducible data.

The PiCCO Monitor: A Review

Advanced haemodynamic monitoring remains a cornerstone in the management of the critically ill. While rates of pulmonary artery catheter use have been declining, there has been an increase in the number of alternatives for monitoring cardiac output as well as greater understanding of the methods and criteria with which to compare devices. The PiCCO (Pulse index Continuous Cardiac Output) device is one such alternative, integrating a wide array of both static and dynamic haemodynamic data through a combination of trans-cardiopulmonary thermodilution and pulse contour analysis. The requirement for intra-arterial and central venous catheterisation limits the use of PiCCO to those with evolving critical illness or at high risk of complex and severe haemodynamic derangement. While the accuracy of trans-cardiopulmonary thermodilution as a measure of cardiac output is well established, several other PiCCO measurements require further validation within the context of their intended clinical use. As with all advanced haemodynamic monitoring systems, efficacy in improving patient-centred outcomes has yet to be conclusively demonstrated. The challenge with PiCCO is in improving the understanding of the many variables that can be measured and integrating those that are clinically relevant and adequately validated with appropriate therapeutic interventions.

Lung ultrasound in the management of acute decompensated heart failure

Once thought impracticable, lung ultrasound is now used in patients with a variety of pulmonary processes. This review seeks to describe the utility of lung ultrasound in the management of patients with acute decompensated heart failure (ADHF). A literature search was carried out on PubMed/Medline using search terms related to the topic. Over three thousand results were narrowed down via title and/or abstract review. Related articles were downloaded for full review. Case reports, letters, reviews and editorials were excluded. Lung ultrasonographic multiple B-lines are a good indicator of alveolar interstitial syndrome but are not specific for ADHF. The absence of multiple B-lines can be used to rule out ADHF as a causative etiology. In clinical scenarios where the assessment of acute dyspnea boils down to single or dichotomous pathologies, lung ultrasound can help rule in ADHF. For patients being treated for ADHF, lung ultrasound can also be used to monitor response to therapy. Lung ultrasound is an important adjunct in the management of patients with acute dyspnea or ADHF.

Lung ultrasound: a new tool for the cardiologist

For many years the lung has been considered off-limits for ultrasound. However, it has been recently shown that lung ultrasound (LUS) may represent a useful tool for the evaluation of many pulmonary conditions in cardiovascular disease. The main application of LUS for the cardiologist is the assessment of B-lines. B-lines are reverberation artifacts, originating from water-thickened pulmonary interlobular septa. Multiple B-lines are present in pulmonary congestion, and may help in the detection, semiquantification and monitoring of extravascular lung water, in the differential diagnosis of dyspnea, and in the prognostic stratification of chronic heart failure and acute coronary syndromes.

B-lines quantify the lung water content: a lung ultrasound versus lung gravimetry study in acute lung injury

B-lines (also termed ultrasound lung comets) obtained with lung ultrasound detect experimental acute lung injury (ALI) very early and before hemogasanalytic changes, with a simple, noninvasive, nonionizing and real-time method. Our aim was to estimate the correlation between B-lines number and the wet/dry ratio of the lung tissue, measured by gravimetry, in an experimental model of ALI. Seventeen Na-pentobarbital anesthetized, cannulated (central vein and carotid artery) minipigs were studied: five sham-operated animals served as controls and, in 12 animals, ALI was induced by injection of oleic acid (0.1 mL/kg) via the central venous catheter. B-lines were measured by echographic scanner in four predetermined chest scanning sites in each animal. At the end of each experiment, both lungs were dissected, weighed and dried to determine wet/dry weight ratio by gravimetry. After the injection of oleic acid, B-lines number increased over time. A significant correlation was found between the wet/dry ratio and B-lines number (r = 0.91, p < 0.001). These data suggest that in an experimental pig model of ALI/ARDS, B-lines assessed by lung ultrasound provide a simple, semiquantitative, noninvasive index of lung water accumulation, strongly correlated to invasive gravimetric assessment.

Nasal potential difference to detect Na+ channel dysfunction in acute lung injury

Pulmonary fluid clearance is regulated by the active transport of Na(+) and Cl(-) through respiratory epithelial ion channels. Ion channel dysfunction contributes to the pathogenesis of various pulmonary fluid disorders including high-altitude pulmonary edema (HAPE) and neonatal respiratory distress syndrome (RDS). Nasal potential difference (NPD) measurement allows an in vivo investigation of the functionality of these channels. This technique has been used for the diagnosis of cystic fibrosis, the archetypal respiratory ion channel disorder, for over a quarter of a century. NPD measurements in HAPE and RDS suggest constitutive and acquired dysfunction of respiratory epithelial Na(+) channels. Acute lung injury (ALI) is characterized by pulmonary edema due to alveolar epithelial-interstitial-endothelial injury. NPD measurement may enable identification of critically ill ALI patients with a susceptible phenotype of dysfunctional respiratory Na(+) channels and allow targeted therapy toward Na(+) channel function.

Extravascular lung water index measurement in critically ill children does not correlate with a chest x-ray score of pulmonary edema

INTRODUCTION

Extravascular lung water index (EVLWI) can be measured at the bedside using the transpulmonary thermodilution technique (TPTD). The goal of this study was to compare EVLWI values with a chest x-ray score of pulmonary edema and markers of oxygenation in critically ill children.

METHODS

This was a prospective observational study in a pediatric intensive care unit of a university hospital. We included 27 critically ill children with an indication for advanced invasive hemodynamic monitoring. No specific interventions for the purpose of the study were carried out. Measurements included EVLWI and other relevant hemodynamic variables. Blood gas analysis, ventilator parameters, chest x-ray and TPTD measurements were obtained within a three-hour time frame. Two radiologists assessed the chest x-ray and determined a score for pulmonary edema.

RESULTS

A total of 103 measurements from 24 patients were eligible for final analysis. Mean age was two years (range: two months to eight years). Median cardiac index was 4.00 (range: 1.65 to 10.85) l/min/m2. Median EVLWI was 16 (range: 6 to 31) ml/kg. The weighted kappa between the chest x-ray scores of the two radiologists was 0.53. There was no significant correlation between EVLWI or chest x-ray score and the number of ventilator days, severity of illness or markers of oxygenation. There was no correlation between EVLWI and the chest x-ray score. EVLWI was significantly correlated with age and length (r2 of 0.47 and 0.67 respectively).

CONCLUSIONS

The extravascular lung water index in critically ill children does not correlate with a chest x-ray score of pulmonary edema, nor with markers of oxygenation.

Why, when, and how to assess pulmonary congestion in heart failure: pathophysiological, clinical, and methodological implications

Acute heart failure syndrome (AHFS) is a major public health problem. It is defined as gradual or rapid change in heart failure (HF) signs and symptoms, which often results in an unplanned hospitalization and a need for urgent therapy. Many evidence-based pharmacologic, device, and surgical treatment for HF are available or under development. Despite these new treatments and improvement in survival, hospitalizations in HF have steadily increased over the last 30 years, and the post-discharge prognosis of patients hospitalized with AHFS remains poor (Gheorghiade et al. Circulation 112:3958-3968, 2005; Fonarow et al. Rev Cardiovasc Med 4:S21-30, 2003). Most hospitalizations for AHFS are related to "congestion" rather than to low cardiac output. The definition, identification, quantification, and monitoring of congestion are therefore essential in AHFS. The purpose of this article is: (1) to characterize the different types of hemodynamic, clinical, and pulmonary congestion in AHFS; (2) to focus on the different possible ways to assess pulmonary congestion (probably the most important, and up to now the most diagnostically elusive of the three types of congestions); (3) to propose new possible ways to implement objective and user-friendly measures of pulmonary congestion in clinical and scientific decision-making in AHFS in the near future.

Measurement of extravascular lung water using the single indicator method in patients: research and potential clinical value

Extravascular lung water includes all of the fluid within the lung but outside of the vasculature. Lung water increases as a result of increased hydrostatic vascular pressure or from an increase in lung endothelial and epithelial permeability or both. Experimentally, extravascular lung water has been measured gravimetrically. Clinically, the chest radiograph is used to determine whether extravascular lung water is present but is an insensitive instrument for determining the quantity of lung water. Bedside measurement of extravascular lung water in patients is now possible using a single indicator thermodilution method. This review critically evaluates the experimental and clinical evidence supporting the potential value of measuring extravascular lung water in patients using the single indicator method.

Measuring impedance in congestive heart failure: current options and clinical applications

Measurement of impedance is becoming increasingly available in the clinical setting as a tool for assessing hemodynamics and volume status in patients with heart failure. The 2 major categories of impedance assessment are the band electrode method and the implanted device lead method. The exact sources of the impedance signal are complex and can be influenced by physiologic effects such as blood volume, fluid, and positioning. This article provides a critical review of our current understanding and promises of impedance measurements, the techniques that have evolved, as well as the evidence and limitations regarding their clinical applications in the setting of heart failure management.

Pharmacodynamic characterization of ceftobiprole in experimental pneumonia caused by phenotypically diverse Staphylococcus aureus strains

Ceftobiprole (BPR) is an investigational cephalosporin with activity against Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA) strains. The pharmacodynamic (PD) profile of BPR against S. aureus strains with a variety of susceptibility phenotypes in an immunocompromised murine pneumonia model was characterized. The BPR MICs of the test isolates ranged from 0.25 to 2 mug/ml. Pharmacokinetic (PK) studies were conducted with infected neutropenic BALB/c mice; and the BPR concentrations were measured in plasma, epithelial lining fluid (ELF), and lung tissue. PD studies with these mice were undertaken with eight S. aureus isolates (two methicillin-susceptible S. aureus strains, three hospital-acquired MRSA strains, and three community-acquired MRSA strains). Subcutaneous BPR doses of 2 to 125 mg/kg of body weight/day were administered, and the change in the number of log(10) CFU/ml in lungs was evaluated after 24 h of therapy. The PD profile was characterized by using the free drug exposures (f) determined from the following parameters: the percentage of time that the concentration was greater than the MIC (T > MIC), the maximum concentration in serum/MIC, and the area under the concentration-time curve/MIC. The BPR PK parameters were linear over the dose range studied in plasma, and the ELF concentrations ranged from 60 to 94% of the free plasma concentration. fT > MIC was the parameter that best correlated with efficacy against a diverse array of S. aureus isolates in this murine pneumonia model. The 80% effective dose (ED(80)), ED(50), and stasis exposures appeared to be similar among the isolates studied. BPR exerted maximal antibacterial effects when fT > MIC ranged from 6 to 22%, regardless of the phenotypic profile of resistance to beta-lactam, fluoroquinolone, erythromycin, clindamycin, or tetracycline antibiotics.

Alveolar fluid clearance in acute lung injury: what have we learned from animal models and clinical studies?

Background

Acute lung injury and the acute respiratory distress syndrome continue to be significant causes of morbidity and mortality in the intensive care setting. The failure of patients to resolve the alveolar edema associated with these conditions is a major contributing factor to mortality; hence there is continued interest to understand the mechanisms of alveolar edema fluid clearance.

Discussion

The accompanying review by Vadász et al. details our current understanding of the signaling mechanisms and cellular processes that facilitate clearance of edema fluid from the alveolar compartment, and how these signaling processes may be exploited in the development of novel therapeutic strategies. To complement that report this review focuses on how intact organ and animal models and clinical studies have facilitated our understanding of alveolar edema fluid clearance in acute lung injury and acute respiratory distress syndrome. Furthermore, it considers how what we have learned from these animal and organ models and clinical studies has suggested novel therapeutic avenues to pursue.

Bedside assessment of extravascular lung water by dilution methods: temptations and pitfalls

OBJECTIVES

To review the advantages and limitations of dilution methods to assess extravascular lung water (EVLW) at the bedside and to discuss the clinical value of EVLW measurements.

DATA SOURCE

Experimental and clinical studies were searched in PUBMED by using "extravascular lung water" and "dilution method" as keywords and further selected as studies investigating either the reliability or the clinical usefulness of dilution methods to assess EVLW. Related articles and the reference lists of selected studies were scanned for additional relevant references.

CONCLUSIONS

Both the double-indicator (thermo-dye) dilution and the single-indicator (cold saline) dilution methods showed close agreement with gravimetric measurement of EVLW (the reference ex vivo method) and have the advantage of being available at the bedside. Most limitations of dilution methods have been described in experimental conditions and lead to an underestimation of EVLW. These limitations include large pulmonary vascular obstruction, focal lung injury, and lung resection. Dilution methods provide an easy and clinically acceptable estimation of EVLW in most critically ill patients, including those with acute respiratory distress syndrome (ARDS). Assessing EVLW may be useful to predict outcome, to diagnose pulmonary edema, to better characterize patients with ARDS, to guide fluid therapy, and to assess the value of new treatments or ventilatory strategies in patients with pulmonary edema.

The clinical application of pulse contour cardiac output and intrathoracic volume measurements in critically ill patients

Cardiac output (CO) determination by pulmonary artery (PA) catheter has increasingly been criticised within the literature due to its invasive nature and poor correlation between the pressure measurements and intravascular volume status in mechanically ventilated patients. Consequently, alternative less invasive technologies to PA catheterisation are emerging within intensive care. One such novel technology are pulse contour CO (PCCO) systems. They establish comprehensive and continuous haemodynamic monitoring utilising a central venous catheter (CVC) and an arterial line. Furthermore, a key feature of this technology is its ability to produce intrathoracic volume measurements which may provide a better estimation of cardiac preload as well as indicate the presence and severity of pulmonary oedema. This article aims to discuss the theoretical basis and clinical application of PCCO systems, how PCCO systems differ from PA catheters and how the intrathoracic volume measurements are derived. Understanding these advanced concepts will ensure that clinicians are able to employ this innovative monitoring technology more effectively.