Loss Of Aeration Research Articles

The impact of heart, lung and diaphragmatic ultrasound on prediction of failed extubation from mechanical ventilation in critically ill patients: a prospective observational pilot study

BackgroundFailed extubation from mechanical ventilation in critically ill patients is multifactorial, complex and not well understood. We aimed to identify whether combined transthoracic echocardiography, lung and diaphragmatic ultrasound can predict extubation failure in critically ill patients.ResultsFifty-three participants who were intubated > 48 h and deemed by the treating intensivist ready for extubation underwent a 60-min pre-extubation weaning trial (pressure support ≤ 10 cmH2O and positive end expiratory pressure 5 cmH2O). Prior to extubation, data collected included ultrasound assessment of left ventricular ejection fraction, left atrial area, early diastolic trans-mitral flow velocity wave (E), early diastolic trans-mitral flow velocity wave/late diastolic trans-mitral flow velocity wave (E/A), early diastolic trans-mitral flow velocity wave/early diastolic mitral annulus velocity (E/E′), interatrial septal motion, lung loss of aeration score and diaphragm movement. At the end of the weaning trial, the rapid shallow breathing index and serum B-type natriuretic peptide concentration were measured. Success and failure of weaning was assessed by defined criteria. Decision to extubate was at the discretion of the treating intensivist. Failure of extubation was defined as re-intubation, non-invasive ventilation or death within 48 h after extubation. Of 53 extubated participants, 11 failed extubation. Failed extubation was associated with diabetes, ischaemic heart disease, higher E/E′ (OR 1.27, 95% CI 1.05–1.54), left atrial area (OR 1.14, CI 1.02–1.28), fixed rightward curvature of the interatrial septum (OR 12.95, CI 2.73–61.41), and higher loss of aeration score of anterior and lateral regions of the lungs (OR 1.41, CI 1.01–1.82).ConclusionsFailed extubation in mechanically ventilated patients is more prevalent if markers of left ventricular diastolic dysfunction and loss of lung aeration are present.

Ultrasound appearance of lungs in patients with ventilator associated pneumonia

Objectives: To document ultrasound appearance of lungs in mechanically ventilated patients with (ventilator associated pneumonia) VAP. Methods: This was a prospective observational cohort, single centre study conducted in PICU of a university affiliated tertiary care hospital. A total of 28 patients of age 1 year to 14 years who were receiving invasive mechanical ventilation for reasons other than pneumonia and other lung diseases were selected by consecutive sampling technique. The lung ultrasound (LUS) was performed whenever there was a suspicion of VAP and these were diagnosed as per CDC criteria. LUS was performed with Aloka SSD-90 machine with both 5MHz linear and 7.5MHz linear transducer. Each lung was divided into six areas (superior and inferior of anterior, lateral and posterior zones). Anterior axillary line divided anterior from lateral and posterior axillary line divided lateral from posterior area. The probe orientation was perpendicular to the ribs. Results: A total of 28 patients (18 males) were enrolled. Median age was 6.5 years ranging from 1-13 years Dynamic linear/arborescent air-bronchograms were seen in all 100% cases. Shred sign was seen in 28% cases. Partial loss of aeration was seen in 68% while total loss of aeration was seen in 32% cases. Hepatisation was noticed in 21 % patients. Thickened pleural line heterogenous echotexture were also noticed. Pleural effusion was seen in two patients. Conclusion: LUS is feasible in mechanically ventilated children and Specific LUS findings are seen in VAP which can be used to diagnose it rapidly at bedside.

Performance assessment of aeration and radial oxygen loss assisted cathode based integrated constructed wetland-microbial fuel cell systems

The present study explores low-cost cathode development possibility using radial oxygen loss (ROL) of Canna indica plants and intermittent aeration (IA) for wastewater treatment and electricity generation in constructed wetland-microbial fuel cell (CW-MFC) system. Two CW-MFC microcosms were developed. Amongst them, one microcosm was planted with Canna indica plants for evaluating the ROL dependent cathode reaction (CW-MFC dependent on ROL) and another microcosm was equipped with intermittent aeration for evaluating the intermittent aeration dependent cathode reaction (CW-MFC with additional IA). The CW-MFC with additional IA has achieved 78.71% and 53.23%, and CW-MFC dependent on ROL has achieved 72.17% and 46.77% COD removal from synthetic wastewater containing glucose loads of 0.7gL−1and 2.0gL−1, respectively. The maximum power density of 31.04mWm−3 and 19.60mWm−3 was achieved in CW-MFC with additional IA and CW-MFC dependent on ROL, respectively.

Prognostic value of modified lung ultrasound aeration loss score in shock patient in intensive care unit

Objective: To investigate the prognostic value of modified lung ultrasound aeration loss score(mLUS) in shock patients in intensive care unit(ICU). Methods: This was a prospective study.Shock patients who were admitted to ICU from April 2016 to August 2016 were eligible; 90 consecutive shock patients were enrolled.Chest ultrasound examination were done within the first 6 hours after included. The mLUS and other ultrasound variables were recorded as well as the clinical data and the outcome. Data has been analyzed, and a bivariate logistic regression model was established to identify the correlation between mLUS on admission and the ICU mortality. Results: The mean APACHE Ⅱ score, lactate, mLUS were significantly increased in non-survivors while the PaO(2)/FiO(2) was decreased in these patients(P=0.048, 0.000, 0.048, 0.000, 0.004). The univariate analysis revealed that the above variables were significantly related to ICU mortality.The multivariate analysis demonstrated that mLUS are the independent risk factors of ICU mortality as well as the lactate(P=0.045, 0.006; AUC=0.733, 0.793, respectively). Conclusion: Modified lung ultrasound aeration loss score can predict the outcome of shock patients in ICU.

Rationale, study design and analysis plan of the lung imaging morphology for ventilator settings in acute respiratory distress syndrome study (LIVE study): Study protocol for a randomised controlled trial

Different acute respiratory distress syndrome (ARDS) phenotypes may explain controversial results in clinical trials. Lung-morphology is one of the ARDS-phenotypes and physiological studies suggest different responses in terms of positive-end-expiratory-pressure (PEEP) and recruitment-manoeuvres (RM) according to loss of aeration. To evaluate whether tailored ventilator regimens may impact ARDS outcomes, our group has designed a randomised-clinical-trial of ventilator settings according to lung morphology in moderate-to-severe ARDS (LIVE study). MethodPatients will be enrolled within the first 12hours of ARDS onset. In both groups, volume-controlled ventilation with low tidal-volumes (Vt) will be used to target a plateau pressure≤30 cmH2O. In the control group, the PEEP level and inspired fraction of oxygen (FiO2) will be set using the ARDSNet table; a Vt of 6 mL/kg of predicted body weight (PBW) will be set and prone position (PP) will be applied. In the intervention arm, the ventilator will be set according to lung morphology (focal/non-focal) that will be assessed according to CT-scan±chest x-ray+lung echography. For focal ARDS patients, a Vt of 8 mL/kg PBW will be used along with low PEEP and PP. For non-focal ARDS patients, a Vt of 6 mL/kg PBW will be used with RM and PEEP to reach a plateau pressure≤30 cmH2O. The primary outcome is all-cause 90-day mortality and the secondary outcomes are: in-hospital mortality, mortality at day 28, 60, 180 and 365; ventilator-free days at day 30, quality of life at one year; ventilator-associated pneumonia rate; barotrauma; ICU and hospital length of stay. This RCT is registered on Clinicaltrials.gov under identifier NCT02149589.

Modified Lung Ultrasound Score for Assessing and Monitoring Pulmonary Aeration.

Purpose Lung Ultrasound Score (LUSS) is a useful tool for lung aeration assessment but presents two theoretical limitations. First, standard LUSS is based on longitudinal scan and detection of number/coalescence of B lines. In the longitudinal scan pleura visualization is limited by intercostal space width. Moreover, coalescence of B lines to define severe loss of aeration is not suitable for non-homogeneous lung pathologies where focal coalescence is possible. We therefore compared longitudinal vs. transversal scan and also cLUSS (standard coalescence-based LUSS) vs. qLUSS (quantitative LUSS based on % of involved pleura). Materials and methods 38 ICU patients were examined in 12 thoracic areas in longitudinal and transversal scan. B lines (number, coalescence), subpleural consolidations (SP), pleural length and pleural involvement (> or ≤ 50 %) were assessed. cLUSS and qLUSS were computed in longitudinal and transversal scan. Results Transversal scan visualized wider (3.9 [IQR 3.8 - 3.9] vs 2.0 [1.6 - 2.5] cm, p < 0.0001) and more constant (variance 0.02 vs 0.34 cm, p < 0.0001) pleural length, more B lines (70 vs 59 % of scans, p < 0.0001), coalescence (39 vs 28 %, p < 0.0001) and SP (22 vs 14 %, p < 0.0001) compared to longitudinal scan. Pleural involvement > 50 % was observed in 17 % and coalescence in 33 % of cases. Focal coalescence accounted for 52 % of cases of coalescence. qLUSS-transv generated a different distribution of aeration scores compared to cLUSS-long (p < 0.0001). Conclusion In unselected ICU patients, variability of pleural length in longitudinal scans is high and focal coalescence is frequent. Transversal scan and quantification of pleural involvement are simple measures to overcome these limitations of LUSS.

Lung Ultrasonography for the Assessment of Perioperative Atelectasis: A Pilot Feasibility Study

Few diagnostic tools are available to anesthesiologists when confronted with intraoperative hypoxemia. Lung ultrasonography is a safe and accurate bedside imaging modality. The aim of this study was to evaluate the feasibility of lung ultrasonography during the perioperative period and assess its ability to detect intraoperative respiratory complications and oxygenation changes resulting from perioperative atelectasis. In this prospective observational pilot study, 30 consecutive patients scheduled for laparoscopic surgery were recruited. Mechanical ventilation was standardized. Lung ultrasonography was performed at 5 predefined time points: before induction of general anesthesia (GA), after induction of GA, after pneumoperitoneum insufflation, on arrival in the recovery room, and before recovery room discharge. For each echographic examination, 12 pulmonary quadrants were imaged. From these, a semiquantitative score, the lung ultrasound (LUS) score, was calculated to assess lung aeration at each time point. Lung ultrasonography was possible in all patients. Changes in the LUS score between the postinduction period and arrival in the recovery room were correlated with changes in oxygenation (Spearman r = -0.43, P = .018). Induction of GA was associated with an increase in the LUS score, which gradually worsened at all time points until recovery room discharge. This increase was significantly worse in the basal and dependent lung zones. Lung ultrasonography helped in the detection of 2 capnothoraces, 1 endobronchial intubation, and 1 episode of subclinical pulmonary edema. Lung ultrasonography in the perioperative period is feasible, allows tracking of perioperative atelectasis, and facilitates the diagnosis of respiratory complications. The evolution of aeration loss correlates moderately with changes in oxygenation.

Behavior of lung ultrasound findings during spontaneous breathing trial.

ObjectiveWe aimed to investigate a potential association between B-lines and weaning failure.MethodsFifty-seven subjects eligible for ventilation liberation were enrolled. Patients with tracheostomy were excluded. Lung ultrasound assessments of six thoracic zones were performed immediately before and at the exnd of the spontaneous breathing trial. B-predominance was defined as any profile with anterior bilateral B-pattern. Patients were followed up to 48 hours after extubation.ResultsThirty-eight individuals were successfully extubated; 11 failed the spontaneous breathing trial and 8 needed reintubation within 48 hours of extubation. At the beginning of the T-piece trial, B-pattern or consolidation was already found at the lower and posterior lung regions in more than half of the individuals and remained non-aerated at the end of the trial. A trend toward loss of lung aeration during spontaneous breathing trials was observed only in the spontaneous breathing trial-failure group (p = 0.07), and there was higher B-predominance at the end of the trial (p = 0.01).ConclusionA loss of lung aeration during the spontaneous breathing trial in non-dependent lung zones was demonstrated in subjects who failed to wean.

The Sound of Lung – Ultrasound of the Lung and Mediastinum

The analysis of lung artefacts has gained increasing importance as markers of lung pathology. B-line artefact (BLA), caused by a reverberation phenomenon, is the most important lung artefact. In this presentation the current role of BLA in pneumology is discussed. The current literature about BLA is summarized in healthy subjects and patients with interstitial syndrome (pulmonary fibrosis and edema) including technical factors influencing BLA visualization. BLA imaging is influenced by more factors than recently assumed [(1, 2)]. When multiple BLA are visualized in the lung, they represent a sign of increased density due to the loss of aeration in the lung periphery. This condition may indicate different diseases including cardiogenic pulmonary edema, diffuse or focal interstitial lung diseases, infections and acute respiratory distress syndrome (ARDS). Correct interpretation of BLA in lung ultrasound is strongly influenced by associated sonographic signs and careful integration of all relevant clinical information. BLA are useful to monitor clinical response, and may become crucial in directing the diagnostic process [(3)].

Lung ultrasound can be used to predict the potential of prone positioning and assess prognosis in patients with acute respiratory distress syndrome.

BackgroundIt is very important to assess the effectiveness of prone positioning (PP) in patients with severe acute respiratory distress syndrome (ARDS). However, it is difficult to identify patients who may benefit from PP. The purpose of this study was to investigate whether prone positioning potential (PPP) can be predicted by lung ultrasound in patients with ARDS.MethodsIn this prospective study, 45 patients with ARDS were included for the assessment of PPP. A PP lung ultrasound examination (PLUE) protocol was performed in the dorsal regions of the lung in 16 areas at H0, H3, and H6 (0, 3, and 6 h after PP). The ultrasonography videos were blindly evaluated by two expert clinicians to classify the lung regions as normal pattern (N), moderate loss of lung aeration (B1), severe loss of lung aeration (B2), and consolidation (C). The aeration scores were collected at H0, H3, and H6. According to the ratio of partial pressure of arterial oxygen to fraction of inspired oxygen (P/F ratio) at 7 days, patients were classified into PPP-positive (P/F ratio >300) and PPP-negative groups; also, the patients were classified into survival and nonsurvival groups according to 28-day mortality.ResultsAeration scores was compared at H0, H3, and H6. The scores were significantly reduced between H3 and H0, but there was no difference between H3 and H6. The aeration score variation (ASV) of the PPP-positive group between H3 and H0 was significantly higher than that in the PPP-negative group, and the sensitivity and specificity of ASV ≥5.5 for the PPP-positive group were 73.9% and 86.4%, respectively. The area under the receiver operating characteristic curve (AUROC) was 0.852 for the ASV. The ASV between H3 and H0 in the survival group was significantly higher than in the nonsurvival group. The sensitivity and specificity of ASV ≥7 for survival were 51.5% and 75%, respectively. The AUROC was 0.702 for the ASV.ConclusionsThe PLUE protocol can be used to predict PPP and assess prognosis in patients with ARDS.

Lung B-line artefacts and their use.

The analysis of lung artefacts has gained increasing importance as markers of lung pathology. B-line artefact (BLA), caused by a reverberation phenomenon, is the most important lung artefact. In this review, we discuss the current role of BLA in pneumology and explore open questions of the published consensus. We summarized current literature about BLA. Also, we presented observations on healthy subjects and patients with interstitial syndrome (pulmonary fibrosis and edema), to investigate technical factors influencing BLA visualization. BLA imaging is influenced by more factors than recently assumed. When multiple BLA is visualized in the lung, they represent a sign of increased density due to the loss of aeration in the lung periphery. This condition may indicate different diseases including cardiogenic pulmonary edema, diffuse or focal interstitial lung diseases (ILD), infections and acute respiratory distress syndrome (ARDS). Correct interpretation of BLA in lung ultrasound is strongly influenced by associated sonographic signs and careful integration of all relevant clinical information. BLA is useful to monitor clinical response, and may become crucial in directing the diagnostic process. Further research is warranted to clarify technical adjustments, different probe and machine factors that influence the visualization of BLA.

Bedside Lung Ultrasound During Acute Chest Syndrome in Sickle Cell Disease.

Lung ultrasound (LU) is increasingly used to assess pleural and lung disease in intensive care unit (ICU) and emergency unit at the bedside. We assessed the performance of bedside chest radiograph (CR) and LU during severe acute chest syndrome (ACS), using computed tomography (CT) as the reference standard.We prospectively explored 44 ACS episodes (in 41 patients) admitted to the medical ICU. Three imaging findings were evaluated (consolidation, ground-glass opacities, and pleural effusion). A score was used to quantify and compare loss of lung aeration with each technique and assess its association with outcome.A total number of 496, 507, and 519 lung regions could be assessed by CT scan, bedside CR, and bedside LU, respectively. Consolidations were the most common pattern and prevailed in lung bases (especially postero-inferior regions). The agreement with CT scan patterns was significantly higher for LU as compared to CR (κ coefficients of 0.45 ± 0.03 vs 0.30 ± 0.03, P < 0.01 for the parenchyma, and 0.73 ± 0.08 vs 0.06 ± 0.09, P < 0.001 for pleural effusion). The Bland and Altman analysis showed a nonfixed bias of −1.0 (P = 0.12) between LU score and CT score whereas CR score underestimated CT score with a fixed bias of −5.8 (P < 0.001). The specificity for the detection of consolidated regions or pleural effusion (using CT scan as the reference standard) was high for LU and CR, whereas the sensitivity was high for LU but low for CR. As compared to others, ACS patients with an LU score above the median value of 11 had a larger volume of transfused and exsanguinated blood, greater oxygen requirements, more need for mechanical ventilation, and a longer ICU length of stay.LU outperformed CR for the diagnosis of consolidations and pleural effusion during ACS. Higher values of LU score identified patients at risk of worse outcome.

Can lung ultrasonography predict prone positioning response in acute respiratory distress syndrome patients?

PurposeThe purpose was to assess whether lung ultrasonography (L-US) is a useful tool in prediction of prone positioning (PP) oxygenation response in patients with acute respiratory distress syndrome (ARDS). MethodsIn a prospective study, 19 ARDS patients were included for assessment of PP oxygenation response. The latter was assessed for at least 12 hours 6 different ultrasonography windows were performed on each hemithorax before prone (H0, H2, H12 before return to supine and at H14 (2 hours after return to supine). Patients were classified into 2 groups (responders / non responders) according their oxygenation response to PP. Ultrasonography videos were blindly evaluated by 3 expert clinicians to classify lung regions as “normal”, “moderate loss of aeration,” “severe loss of aeration,” or “lung consolidation.” Oxygenation parameters were collected at H0, H2, and H14. ResultsAssociation of each lung region aspect to PP oxygenation response was compared between the 2 groups. The normal aspect of the anterobasal regions was significantly associated with the oxygenation response (P = .0436), with a positive predictive value equal to or near 100%. DiscussionOur results demonstrated that a simple and short L-US examination could be a useful tool in prediction of PP oxygenation response in ARDS patients. A normal L-US pattern of both anterobasal lung regions in supine position may predict a significant Pao2/Fio2 ratio improvement.

Mild loss of lung aeration augments stretch in healthy lung regions.

Inspiratory stretch by mechanical ventilation worsens lung injury. However, it is not clear whether and how the ventilator damages lungs in the absence of preexisting injury. We hypothesized that subtle loss of lung aeration during general anesthesia regionally augments ventilation and distension of ventilated air spaces. In eight supine anesthetized and intubated rats, hyperpolarized gas MRI was performed after a recruitment maneuver following 1 h of volume-controlled ventilation with zero positive end-expiratory pressure (ZEEP), FiO2 0.5, and tidal volume 10 ml/kg, and after a second recruitment maneuver. Regional fractional ventilation (FV), apparent diffusion coefficient (ADC) of (3)He (a measurement of ventilated peripheral air space dimensions), and gas volume were measured in lung quadrants of ventral and dorsal regions of the lungs. In six additional rats, computed tomography (CT) images were obtained at each time point. Ventilation with ZEEP decreased total lung gas volume and increased both FV and ADC in all studied regions. Increases in FV were more evident in the dorsal slices. In each lung quadrant, higher ADC was predicted by lower gas volume and by increased mean values (and heterogeneity) of FV distribution. CT scans documented 10% loss of whole-lung aeration and increased density in the dorsal lung, but no macroscopic atelectasis. Loss of pulmonary gas at ZEEP increased fractional ventilation and inspiratory dimensions of ventilated peripheral air spaces. Such regional changes could help explain a propensity for mechanical ventilation to contribute to lung injury in previously uninjured lungs.

Physiological Effects of the Open Lung Approach in Patients with Early, Mild, Diffuse Acute Respiratory Distress Syndrome: An Electrical Impedance Tomography Study.

To test the hypothesis that in early, mild, acute respiratory distress syndrome (ARDS) patients with diffuse loss of aeration, the application of the open lung approach (OLA) would improve homogeneity in lung aeration and lung mechanics, without affecting hemodynamics. Patients were ventilated according to the ARDS Network protocol at baseline (pre-OLA). OLA consisted in a recruitment maneuver followed by a decremental positive end-expiratory pressure trial. Respiratory mechanics, gas exchange, electrical impedance tomography (EIT), cardiac index, and stroke volume variation were measured at baseline and 20 min after OLA implementation (post-OLA). Esophageal pressure was used for lung and chest wall elastance partitioning. The tomographic lung image obtained at the fifth intercostal space by EIT was divided in two ventral and two dorsal regions of interest (ROIventral and ROIDorsal). Fifteen consecutive patients were studied. The OLA increased arterial oxygen partial pressure/inspired oxygen fraction from 216 ± 13 to 311 ± 19 mmHg (P < 0.001) and decreased elastance of the respiratory system from 29.4 ± 3 cm H2O/l to 23.6 ± 1.7 cm H2O/l (P < 0.01). The driving pressure (airway opening plateau pressure - total positive end-expiratory pressure) decreased from 17.9 ± 1.5 cm H2O pre-OLA to 15.4 ± 2.1 post-OLA (P < 0.05). The tidal volume fraction reaching the dorsal ROIs increased, and consequently the ROIVentral/Dorsal impedance tidal variation decreased from 2.01 ± 0.36 to 1.19 ± 0.1 (P < 0.01). The OLA decreases the driving pressure and improves the oxygenation and lung mechanics in patients with early, mild, diffuse ARDS. EIT is useful to assess the impact of OLA on regional tidal volume distribution.

Weaning indexes do not predict success with non invasive mechanical ventilation in extubation failure

Lung ultrasound (LUS) is a useful tool in the intensive care unit (ICU) and in mechanical ventilation it has been possible to measure lung collapse that presents after a spontaneous breathing test by measuring lung aeration loss and detecting those patients that probably will fail extubation and assessing the necessity of non invasive mechanical ventilation (NIMV) as well as those patients that fail the spontaneous breathing test as a weaning method. There is controversy whether the NIMV can help in weaning in patients other than those with chronic obstructive pulmonary disease (COPD).

Hazardous events in membrane bioreactors – Part 1: Impacts on key operational and bulk water quality parameters

In this series of articles, the potential impacts of a number of operational ‘hazardous events’ on membrane bioreactors (MBRs) removal performance were investigated. The hazardous events assessed included salinity shock, 2,4-dinitrophenol (DNP) shock, ammonia shock, organic carbon shock, feed starvation, loss of power supply, loss of aeration, complete wash out of biomass, defective fibres, and physical membrane damage. This initial study focuses on the removal of key bulk water quality and operational parameters, i.e. changes in pH, turbidity, chemical oxygen demand (COD), dissolved organic carbon (DOC), biomass concentrations, capillary suction time (CST) and membrane fouling rate. DNP, salinity and organic carbon shock conditions were shown to significantly impact removal of organic matter (in terms of COD and DOC). These findings suggest that changes in COD and DOC concentrations were determined to be effective parameters for monitoring the impacts of these shock load events. Feed starvation significantly impacted biomass concentrations but the overall system performance remained relatively resilient, as it continued to achieve effective COD and DOC removals. The results from physical membrane damage experiment confirm that turbidity is an effective indicator for online monitoring of physical membrane damage. The results of this study can assist with validation of MBR processes.

Lung ultrasound aeration assessment: comparison of two techniques

Lung ultrasound (LUS) allows semiquantification of lung aeration in PEEP trials [1], pneumonia [2] and weaning [3]. LUS score is based on number/coalescence of vertical artifacts (B-lines) in longitudinal scan (LONG) [4]: the pleura is identified between two ribs and its visualization limited by intercostal space (ICS) width. We hypothesized that a transversal scan (TRANSV) aligned with ICS would visualize longer pleura and a higher number of artifacts, with better assessment of loss of aeration (LoA).

Cecal ligation and puncture accelerates development of ventilator-induced lung injury.

Sepsis is a leading cause of respiratory failure requiring mechanical ventilation, but the interaction between sepsis and ventilation is unclear. While prior studies demonstrated a priming role with endotoxin, actual septic animal models have yielded conflicting results regarding the role of preceding sepsis on development of subsequent ventilator-induced lung injury (VILI). Using a rat cecal ligation and puncture (CLP) model of sepsis and subsequent injurious ventilation, we sought to determine if sepsis affects development of VILI. Adult male Sprague-Dawley rats were subject to CLP or sham operation and, after 12 h, underwent injurious mechanical ventilation (tidal volume 30 ml/kg, positive end-expiratory pressure 0 cmH2O) for either 0, 60, or 120 min. Biochemical and physiological measurements, as well as computed tomography, were used to assess injury at 0, 60, and 120 min of ventilation. Before ventilation, CLP rats had higher levels of alveolar neutrophils and interleukin-1β. After 60 min of ventilation, CLP rats had worse injury as evidenced by increased alveolar inflammation, permeability, respiratory static compliance, edema, oxygenation, and computed tomography. By 120 min, CLP and sham rats had comparable levels of lung injury as assessed by many, but not all, of these metrics. CLP rats had an accelerated and worse loss of end-expiratory lung volume relative to sham, and consistently higher levels of alveolar interleukin-1β. Loss of aeration and progression of edema was more pronounced in dependent lung regions. We conclude that CLP initiated pulmonary inflammation in rats, and accelerated the development of subsequent VILI.

Therapeutic Range of Spontaneous Breathing during Mechanical Ventilation

In the 4th century before the common era, the Greek philosopher and physician Hippocrates expressed his wisdom on the value of activity to the sick and the healthy by stating that: “The sick will of course profit to a great extent from gymnastics with regard to the restoration of their health and the healthy will profit with regard to its maintenance” (On Regimen in Acute Diseases, 3, 400 BCE). In contemporary critical care medicine, driven by the goal of protecting our patients from self-inflicted injury, pain, and anxiety – and in contrast to Hippoctrates’ suggestions – we have built a culture of immobilizing our patients: we prescribe high doses of opioids, sedatives, anxiolytics, and anti-pychotics, and with the best intentions, place bed-rest and restraints orders. In patients with severe respiratory failure, we frequently use immobilizing ventilator settings such as volume control ventilation. Recent data have been increasingly challenging this tenet in relation to the fields of neuropsychiatry, rehabilitation, and respiratory medicine1–5. In this issue of Anesthesiology, two papers bring new information on why the concept of muscle activity is also relevant to lung biochemistry and regional function. Guldner et al.6 and Bruells et al.7 provide important experimental data on the relationship between the dose of diaphragmatic activity (spontaneous contribution to breathing during mechanical ventilation) and the resulting response in terms of lung mechanical stress, gas exchange, and markers of muscle deconditioning. As the main respiratory muscle, the diaphragm contributes 72% for tidal breathing8 and its role in respiratory mechanics and gas exchange goes well beyond this global number. One of the reasons is its curvature during spontaneous breathing in the supine position, which facilitates expansion of dependent lung regions9, optimizes the regional distribution of lung ventilation, and prevents loss of dependent lung aeration and increase in shunt observed when muscle paralysis is produced10. Accordingly, modes of ventilation proposed since the 1970s tried to explore those advantages in patients with acute respiratory failure. The beneficial effects of maintaining continuous spontaneous breathing during mechanical ventilation of patients with acute respiratory failure have been described by Putensen and coworkers in two well-designed studies11,12. However, in patients with severe respiratory failure, barriers to spontaneous breathing during mechanical ventilation including patient-ventilator asynchrony, high oxygen consumption of the respiratory pump muscles, and the risk of barotrauma, have hindered a clear determination of the value of spontaneous breathing during mechanical ventilation.