EXpert consensus On Diaphragm UltraSonography in the critically ill (EXODUS): a Delphi consensus statement on the measurement of diaphragm ultrasound-derived parameters in a critical care setting.

BACKGROUND: Diaphragm ultrasonography is rapidly evolving in both critical care and research. Nevertheless, methodologically robust guidelines on its methodology and acquiring expertise do not, or only partially, exist. Therefore, we set out to provide consensus-based statements towards a universal measurement protocol for diaphragm ultrasonography and establish key areas for research. METHODS: To formulate a robust expert consensus statement, between November 2020 and May 2021, a two-round, anonymous and online survey-based Delphi study among experts in the field was performed. Based on the literature review, the following domains were chosen: "Anatomy and physiology", "Transducer Settings", "Ventilator Impact", "Learning and expertise", "Daily practice" and "Future directions". Agreement of ≥ 68% (≥ 10 panelists) was needed to reach consensus on a question. RESULTS: Of 18 panelists invited, 14 agreed to participate in the survey. After two rounds, the survey included 117 questions of which 42 questions were designed to collect arguments and opinions and 75 questions aimed at reaching consensus. Of these, 46 (61%) consensus was reached. In both rounds, the response rate was 100%. Among others, there was agreement on measuring thickness between the pleura and peritoneum, using > 10% decrease in thickness as cut-off for atrophy and using 40 examinations as minimum training to use diaphragm ultrasonography in clinical practice. In addition, key areas for research were established. CONCLUSION: This expert consensus statement presents the first set of consensus-based statements on diaphragm ultrasonography methodology. They serve to ensure high-quality and homogenous measurements in daily clinical practice and in research. In addition, important gaps in current knowledge and thereby key areas for research are established. Trial registration The study was pre-registered on the Open Science Framework with registration digital object identifier https://doi.org/10.17605/OSF.IO/HM8UG .

Positive end-expiratory pressure in COVID-19 acute respiratory distress syndrome: the heterogeneous effects.

BACKGROUND: We hypothesized that as CARDS may present different pathophysiological features than classic ARDS, the application of high levels of end-expiratory pressure is questionable. Our first aim was to investigate the effects of 5-15 cmH2O of PEEP on partitioned respiratory mechanics, gas exchange and dead space; secondly, we investigated whether respiratory system compliance and severity of hypoxemia could affect the response to PEEP on partitioned respiratory mechanics, gas exchange and dead space, dividing the population according to the median value of respiratory system compliance and oxygenation. Thirdly, we explored the effects of an additional PEEP selected according to the Empirical PEEP-FiO2 table of the EPVent-2 study on partitioned respiratory mechanics and gas exchange in a subgroup of patients. METHODS: Sixty-one paralyzed mechanically ventilated patients with a confirmed diagnosis of SARS-CoV-2 were enrolled (age 60 [54-67] years, PaO2/FiO2 113 [79-158] mmHg and PEEP 10 [10-10] cmH2O). Keeping constant tidal volume, respiratory rate and oxygen fraction, two PEEP levels (5 and 15 cmH2O) were selected. In a subgroup of patients an additional PEEP level was applied according to an Empirical PEEP-FiO2 table (empirical PEEP). At each PEEP level gas exchange, partitioned lung mechanics and hemodynamic were collected. RESULTS: At 15 cmH2O of PEEP the lung elastance, lung stress and mechanical power were higher compared to 5 cmH2O. The PaO2/FiO2, arterial carbon dioxide and ventilatory ratio increased at 15 cmH2O of PEEP. The arterial-venous oxygen difference and central venous saturation were higher at 15 cmH2O of PEEP. Both the mechanics and gas exchange variables significantly increased although with high heterogeneity. By increasing the PEEP from 5 to 15 cmH2O, the changes in partitioned respiratory mechanics and mechanical power were not related to hypoxemia or respiratory compliance. The empirical PEEP was 18 ± 1 cmH2O. The empirical PEEP significantly increased the PaO2/FiO2 but also driving pressure, lung elastance, lung stress and mechanical power compared to 15 cmH2O of PEEP. CONCLUSIONS: In COVID-19 ARDS during the early phase the effects of raising PEEP are highly variable and cannot easily be predicted by respiratory system characteristics, because of the heterogeneity of the disease.

Hysteresis and Lung Recruitment in Acute Respiratory Distress Syndrome Patients: A CT Scan Study.

OBJECTIVES: Hysteresis of the respiratory system pressure-volume curve is related to alveolar surface forces, lung stress relaxation, and tidal reexpansion/collapse. Hysteresis has been suggested as a means of assessing lung recruitment. The objective of this study was to determine the relationship between hysteresis, mechanical characteristics of the respiratory system, and lung recruitment assessed by a CT scan in mechanically ventilated acute respiratory distress syndrome patients. DESIGN: Prospective observational study. SETTING: General ICU of a university hospital. PATIENTS: Twenty-five consecutive sedated and paralyzed patients with acute respiratory distress syndrome (age 64 ± 15 yr, body mass index 26 ± 6 kg/m, PaO2/FIO2 147 ± 42, and positive end-expiratory pressure 9.3 ± 1.4 cm H2O) were enrolled. INTERVENTIONS: A low-flow inflation and deflation pressure-volume curve (5-45 cm H2O) and a sustained inflation recruitment maneuver (45 cm H2O for 30 s) were performed. A lung CT scan was performed during breath-holding pressure at 5 cm H2O and during the recruitment maneuver at 45 cm H2O. MEASUREMENTS AND MAIN RESULTS: Lung recruitment was computed as the difference in noninflated tissue and in gas volume measured at 5 and at 45 cm H2O. Hysteresis was calculated as the ratio of the area enclosed by the pressure-volume curve and expressed as the hysteresis ratio. Hysteresis was correlated with respiratory system compliance computed at 5 cm H2O and the lung gas volume entering the lung during inflation of the pressure-volume curve (R = 0.749, p < 0.001 and R = 0.851, p < 0.001). The hysteresis ratio was related to both lung tissue and gas recruitment (R = 0.266, p = 0.008, R = 0.357, p = 0.002, respectively). Receiver operating characteristic analysis showed that the optimal cutoff value to predict lung tissue recruitment for the hysteresis ratio was 28% (area under the receiver operating characteristic curve, 0.80; 95% CI, 0.62-0.98), with sensitivity and specificity of 0.75 and 0.77, respectively. CONCLUSIONS: Hysteresis of the respiratory system computed by low-flow pressure-volume curve is related to the anatomical lung characteristics and has an acceptable accuracy to predict lung recruitment.

Bedside calculation of mechanical power during volume- and pressure-controlled mechanical ventilation.

BACKGROUND: Mechanical power (MP) is the energy delivered to the respiratory system over time during mechanical ventilation. Our aim was to compare the currently available methods to calculate MP during volume- and pressure-controlled ventilation, comparing different equations with the geometric reference method, to understand whether the easier to use surrogate formulas were suitable for the everyday clinical practice. This would warrant a more widespread use of mechanical power to promote lung protection. METHODS: Forty respiratory failure patients, sedated and paralyzed for clinical reasons, were ventilated in volume-controlled ventilation, at two inspiratory flows (30 and 60 L/min), and pressure-controlled ventilation with a similar tidal volume. Mechanical power was computed both with the geometric method, as the area between the inspiratory limb of the airway pressure and the volume, and with two algebraic methods, a comprehensive and a surrogate formula. RESULTS: The bias between the MP computed by the geometric method and by the comprehensive algebraic method during volume-controlled ventilation was respectively 0.053 (0.77, - 0.81) J/min and - 0.4 (0.70, - 1.50) J/min at low and high flows (r2 = 0.96 and 0.97, p < 0.01). The MP measured and computed by the two methods were highly correlated (r2 = 0.95 and 0.94, p < 0.01) with a bias of - 0.0074 (0.91, - 0.93) and - 1.0 (0.45, - 2.52) J/min at high-low flows. During pressure-controlled ventilation, the bias between the MP measured and the one calculated with the comprehensive and simplified methods was correlated (r2 = 0.81, 0.94, p < 0.01) with mean differences of - 0.001 (2.05, - 2.05) and - 0.81 (2.11, - 0.48) J/min. CONCLUSIONS: Both for volume-controlled and pressure-controlled ventilation, the surrogate formulas approximate the reference method well enough to warrant their use in the everyday clinical practice. Given that these formulas require nothing more than the variables already displayed by the intensive care ventilator, a more widespread use of mechanical power should be encouraged to promote lung protection against ventilator-induced lung injury.

Effect of mechanical power on intensive care mortality in ARDS patients.

BACKGROUND: In ARDS patients, mechanical ventilation should minimize ventilator-induced lung injury. The mechanical power which is the energy per unit time released to the respiratory system according to the applied tidal volume, PEEP, respiratory rate, and flow should reflect the ventilator-induced lung injury. However, similar levels of mechanical power applied in different lung sizes could be associated to different effects. The aim of this study was to assess the role both of the mechanical power and of the transpulmonary mechanical power, normalized to predicted body weight, respiratory system compliance, lung volume, and amount of aerated tissue on intensive care mortality. METHODS: Retrospective analysis of ARDS patients previously enrolled in seven published studies. All patients were sedated, paralyzed, and mechanically ventilated. After 20 min from a recruitment maneuver, partitioned respiratory mechanics measurements and blood gas analyses were performed with a PEEP of 5 cmH2O while the remaining setting was maintained unchanged from the baseline. A whole lung CT scan at 5 cmH2O of PEEP was performed to estimate the lung gas volume and the amount of well-inflated tissue. Univariate and multivariable Poisson regression models with robust standard error were used to calculate risk ratios and 95% confidence intervals of ICU mortality. RESULTS: Two hundred twenty-two ARDS patients were included; 88 (40%) died in ICU. Mechanical power was not different between survivors and non-survivors 14.97 [11.51-18.44] vs. 15.46 [12.33-21.45] J/min and did not affect intensive care mortality. The multivariable robust regression models showed that the mechanical power normalized to well-inflated tissue (RR 2.69 [95% CI 1.10-6.56], p = 0.029) and the mechanical power normalized to respiratory system compliance (RR 1.79 [95% CI 1.16-2.76], p = 0.008) were independently associated with intensive care mortality after adjusting for age, SAPS II, and ARDS severity. Also, transpulmonary mechanical power normalized to respiratory system compliance and to well-inflated tissue significantly increased intensive care mortality (RR 1.74 [1.11-2.70], p = 0.015; RR 3.01 [1.15-7.91], p = 0.025). CONCLUSIONS: In our ARDS population, there is not a causal relationship between the mechanical power itself and mortality, while mechanical power normalized to the compliance or to the amount of well-aerated tissue is independently associated to the intensive care mortality. Further studies are needed to confirm this data.

Oesophageal pressure and respiratory muscle ultrasonographic measurements indicate inspiratory effort during pressure support ventilation.

BACKGROUND: Bedside measures of patient effort are essential to properly titrate the level of pressure support ventilation. We investigated whether the tidal swing in oesophageal (ΔPes) and transdiaphragmatic pressure (ΔPdi), and ultrasonographic changes in diaphragm (TFdi) and parasternal intercostal (TFic) thickening are reliable estimates of respiratory effort. The effect of diaphragm dysfunction was also considered. METHODS: Twenty-one critically ill patients were enrolled: age 73 (14) yr, BMI 27 (7) kg m-2, and Pao2/Fio2 33.3 (9.2) kPa. A three-level pressure support trial was performed: baseline, 25% (PS-medium), and 50% reduction (PS-low). We recorded the oesophageal and transdiaphragmatic pressure-time products (PTPs), work of breathing (WOB), and diaphragm and intercostal ultrasonography. Diaphragm dysfunction was defined by the Gilbert index. RESULTS: Pressure support was 9.0 (1.6) cm H2O at baseline, 6.7 (1.3) (PS-medium), and 4.4 (1.0) (PS-low). ΔPes was significantly associated with the oesophageal PTP (R2=0.868; P<0.001) and the WOB (R2=0.683; P<0.001). ΔPdi was significantly associated with the transdiaphragmatic PTP (R2=0.820; P<0.001). TFdi was only weakly correlated with the oesophageal PTP (R2=0.326; P<0.001), and the correlation improved after excluding patients with diaphragm dysfunction (R2=0.887; P<0.001). TFdi was higher and TFic lower in patients without diaphragm dysfunction: 33.6 (18.2)% vs 13.2 (9.2)% and 2.1 (1.7)% vs 12.7 (9.1)%; P<0.0001. CONCLUSIONS: ΔPes and ΔPdi are adequate estimates of inspiratory effort. Diaphragm ultrasonography is a reliable indicator of inspiratory effort in the absence of diaphragm dysfunction. Additional measurement of parasternal intercostal thickening may discriminate a low inspiratory effort or a high effort in the presence of a dysfunctional diaphragm.

Urine Electrolytes in the Intensive Care Unit: From Pathophysiology to Clinical Practice.

Assessment of urine concentrations of sodium, chloride, and potassium is a widely available, rapid, and low-cost diagnostic option for the management of critically ill patients. Urine electrolytes have long been suggested in the diagnostic workup of hypovolemia, kidney injury, and acid-base and electrolyte disturbances. However, due to the wide range of normal reference values and challenges in interpretation, their use is controversial. To clarify their potential role in managing critical patients, we reviewed existing evidence on the use of urine electrolytes for diagnostic and therapeutic evaluation and assessment in critical illness. This review will describe the normal physiology of water and electrolyte excretion, summarize the use of urine electrolytes in hypovolemia, acute kidney injury, acid-base, and electrolyte disorders, and suggest some practical flowcharts for the potential use of urine electrolytes in daily critical care practice.

Body Position Alters Mechanical Power and Respiratory Mechanics During Thoracic Surgery.

BACKGROUND: During thoracic surgery, patients are usually positioned in lateral decubitus and only the dependent lung ventilated. The ventilated lung is thus exposed to the weight of the contralateral hemithorax and restriction of the dependent chest wall. We hypothesized that mechanical power would increase during one-lung ventilation in the lateral position. METHODS: We performed a prospective, observational, single-center study from December 2016 to May 2017. Thirty consecutive patients undergoing general anesthesia with mechanical ventilation (mean age, 68 ± 11 years; body mass index, 25 ± 5 kg·m) for thoracic surgery were enrolled. Total and partitioned mechanical power, lung and chest wall elastance, and esophageal pressure were compared in supine and lateral position with double- and one-lung ventilation and with closed and open chest both before and after surgery. Mixed factorial ANOVA for repeated measurements was performed, with both step and the period before or after surgery as 2 within-subject factors, and left or right body position during surgery as a fixed, between-subject factor. Appropriate interaction terms were included. RESULTS: The mechanical power was higher in lateral one-lung ventilation compared to both supine and lateral position double-lung ventilation (11.1 ± 3.0 vs 8.2 ± 2.7 vs 8.7 ± 2.6; mean difference, 2.9 J·minute [95% CI, 1.4-4.4 J·minute] and 2.4 J·minute [95% CI, 0.9-3.9 J·minute]; P < .001 and P = .002, respectively). Lung elastance was higher during lateral position one-lung ventilation compared to both lateral and supine double-lung ventilation (24.3 ± 8.7 vs 9.5 ± 3.8 vs 10.0 ± 3.8; mean difference, 14.7 cm H2O·L [95% CI, 11.2-18.2 cm H2O·L] and 14.2 cm H2O·L [95% CI, 10.8-17.7 cm H2O·L], respectively) and was higher compared to predicted values (20.1 ± 7.5 cm H2O·L). Chest wall elastance increased in lateral position double-lung ventilation compared to supine (11.1 ± 3.8 vs 6.6 ± 3.4; mean difference, 4.5 cm H2O·L [95% CI, 2.6-6.3 cm H2O·L]) and was lower in lateral position one-lung ventilation with open chest than with a closed chest (3.5 ± 1.9 vs 7.1 ± 2.8; mean difference, 3.6 cm H2O·L [95% CI, 2.4-4.8 cm H2O·L]). The end-expiratory esophageal pressure decreased moving from supine position to lateral position one-lung ventilation while increased with the opening of the chest wall. CONCLUSIONS: Mechanical power and lung elastance are increased in the lateral position with one-lung ventilation. Esophageal pressure monitoring may be used to follow these changes.

Global and Regional Diagnostic Accuracy of Lung Ultrasound Compared to CT in Patients With Acute Respiratory Distress Syndrome.

OBJECTIVES: Lung CT is the reference imaging technique for acute respiratory distress syndrome, but requires transportation outside the intensive care and x-ray exposure. Lung ultrasound is a promising, inexpensive, radiation-free, tool for bedside imaging. Aim of the present study was to compare the global and regional diagnostic accuracy of lung ultrasound and CT scan. DESIGN: A prospective, observational study. SETTING: Intensive care and radiology departments of a University hospital. PATIENTS: Thirty-two sedated, paralyzed acute respiratory distress syndrome patients (age 65 ± 14 yr, body mass index 25.9 ± 6.5 kg/m, and PaO2/FIO2 139 ± 47). INTERVENTIONS: Lung CT scan and lung ultrasound were performed at positive end-expiratory pressure 5 cm H2O. A standardized assessment of six regions per hemithorax was used; each region was classified for the presence of normal aeration, alveolar-interstitial syndrome, consolidation, and pleural effusion. Agreement between the two techniques was calculated, and diagnostic variables were assessed for lung ultrasound using lung CT as a reference. MEASUREMENTS AND MAIN RESULTS: Global agreement between lung ultrasound and CT ranged from 0.640 (0.391-0.889) to 0.934 (0.605-1.000) and was on average 0.775 (0.577-0.973). The overall sensitivity and specificity of lung ultrasound ranged from 82.7% to 92.3% and from 90.2% to 98.6%, respectively. Similar results were found with regional analysis. The diagnostic accuracy of lung ultrasound was significantly higher when those patterns not reaching the pleural surface were excluded (area under the receiver operating characteristic curve: alveolar-interstitial syndrome 0.854 [0.821-0.887] vs 0.903 [0.852-0.954]; p = 0.049 and consolidation 0.851 [0.818-0.884] vs 0.896 [0.862-0.929]; p = 0.044). CONCLUSIONS: Lung ultrasound is a reproducible, sensitive, and specific tool, which allows for bedside detections of the morphologic patterns in acute respiratory distress syndrome. The presence of deep lung alterations may impact the diagnostic performance of this technique.

Dynamic hyperinflation and intrinsic positive end-expiratory pressure in ARDS patients.

BACKGROUND: In ARDS patients, changes in respiratory mechanical properties and ventilatory settings can cause incomplete lung deflation at end-expiration. Both can promote dynamic hyperinflation and intrinsic positive end-expiratory pressure (PEEP). The aim of this study was to investigate, in a large population of ARDS patients, the presence of intrinsic PEEP, possible associated factors (patients' characteristics and ventilator settings), and the effects of two different external PEEP levels on the intrinsic PEEP. METHODS: We made a secondary analysis of published data. Patients were ventilated with a tidal volume of 6-8 mL/kg of predicted body weight, sedated, and paralyzed. After a recruitment maneuver, a PEEP trial was run at 5 and 15 cmH2O, and partitioned mechanics measurements were collected after 20 min of stabilization. Lung computed tomography scans were taken at 5 and 45 cmH2O. Patients were classified into two groups according to whether or not they had intrinsic PEEP at the end of an expiratory pause. RESULTS: We enrolled 217 sedated, paralyzed patients: 87 (40%) had intrinsic PEEP with a median of 1.1 [1.0-2.3] cmH2O at 5 cmH2O of PEEP. The intrinsic PEEP significantly decreased with higher PEEP (1.1 [1.0-2.3] vs 0.6 [0.0-1.0] cmH2O; p < 0.001). The applied tidal volume was significantly lower (480 [430-540] vs 520 [445-600] mL at 5 cmH2O of PEEP; 480 [430-540] vs 510 [430-590] mL at 15 cmH2O) in patients with intrinsic PEEP, while the respiratory rate was significantly higher (18 [15-20] vs 15 [13-19] bpm at 5 cmH2O of PEEP; 18 [15-20] vs 15 [13-19] bpm at 15 cmH2O). At both PEEP levels, the total airway resistance and compliance of the respiratory system were not different in patients with and without intrinsic PEEP. The total lung gas volume and lung recruitability were also not different between patients with and without intrinsic PEEP (respectively 961 [701-1535] vs 973 [659-1433] mL and 15 [0-32] % vs 22 [0-36] %). CONCLUSIONS: In sedated, paralyzed ARDS patients without a known obstructive disease, the amount of intrinsic PEEP during lung-protective ventilation is negligible and does not influence respiratory mechanical properties.

Enteral versus intravenous approach for the sedation of critically ill patients: a randomized and controlled trial.

BACKGROUND: ICU patients must be kept conscious, calm, and cooperative even during the critical phases of illness. Enteral administration of sedative drugs might avoid over sedation, and would be as adequate as intravenous administration in patients who are awake, with fewer side effects and lower costs. This study compares two sedation strategies, for early achievement and maintenance of the target light sedation. METHODS: This was a multicenter, single-blind, randomized and controlled trial carried out in 12 Italian ICUs, involving patients with expected mechanical ventilation duration > 72 h at ICU admission and predicted mortality > 12% (Simplified Acute Physiology Score II > 32 points) during the first 24 h on ICU. Patients were randomly assigned to receive intravenous (midazolam, propofol) or enteral (hydroxyzine, lorazepam, and melatonin) sedation. The primary outcome was percentage of work shifts with the patient having an observed Richmond Agitation-Sedation Scale (RASS) = target RASS ±1. Secondary outcomes were feasibility, delirium-free and coma-free days, costs of drugs, length of ICU and hospital stay, and ICU, hospital, and one-year mortality. RESULTS: There were 348 patients enrolled. There were no differences in the primary outcome: enteral 89.8% (74.1-100), intravenous 94.4% (78-100), p = 0.20. Enteral-treated patients had more protocol violations: n = 81 (46.6%) vs 7 (4.2%), p < 0.01; more self-extubations: n = 14 (8.1%) vs 4 (2.4%), p = 0.03; a lighter sedative target (RASS = 0): 93% (71-100) vs 83% (61-100), p < 0.01; and lower total drug costs: 2.39 (0.75-9.78) vs 4.15 (1.20-20.19) €/day with mechanical ventilation (p = 0.01). CONCLUSIONS: Although enteral sedation of critically ill patients is cheaper and permits a lighter sedation target, it is not superior to intravenous sedation for reaching the RASS target. TRIAL REGISTRATION: ClinicalTrials.gov, NCT01360346 . Registered on 25 March 2011.

Melatonin Pharmacological Blood Levels Increase Total Antioxidant Capacity in Critically Ill Patients.

In this study, the aim was to test the biochemical effects of melatonin supplementation in Intensive Care Unit (ICU) patients, since their blood levels are decreased. Sixty-four patients were enrolled in the study. From the evening of the 3rd ICU day, patients were randomized to receive oral melatonin (3 mg, group M) or placebo (group P) twice daily, at 20:00 and 24:00, until discharged. Blood was taken (at 00:00 and 14:00), on the 3rd ICU day to assess basal nocturnal melatonin values, and then during the treatment period on the 4th and 8th ICU days. Melatonin, total antioxidant capacity, and oxidative stress were evaluated in serum. Melatonin circadian rhythm before treatment was similar in the two groups, with a partial preservation of the cycle. Four hours from the 1st administration (4th ICU day, 00:00), melatonin levels increased to 2514 (982.3; 7148) pg·mL-1 in group M vs. 20.3 (14.7; 62.3) pg·mL-1 in group P (p < 0.001). After five treatment days (8th ICU day), melatonin absorption showed a repetitive trend in group M, while in group P nocturnal secretion (00:00) was impaired: 20 (11.5; 34.5) pg·mL-1 vs. 33.8 (25.0; 62.2) on the 3rd day (p = 0.029). Immediately from the beginning of treatment, the total antioxidant capacity was significantly higher in melatonin treated subjects at 00:00; a significant correlation was found between total antioxidant capacity and blood melatonin values (ρ = 0.328; p < 0.001). The proposed enteral administration protocol was adequate, even in the early phase, to enhance melatonin blood levels and to protect the patients from oxidative stress. The antioxidant effect of melatonin could play a meaningful role in the care and well-being of these patients.

Current Concepts of ARDS: A Narrative Review.

Acute respiratory distress syndrome (ARDS) is characterized by the acute onset of pulmonary edema of non-cardiogenic origin, along with bilateral pulmonary infiltrates and reduction in respiratory system compliance. The hallmark of the syndrome is refractory hypoxemia. Despite its first description dates back in the late 1970s, a new definition has recently been proposed. However, the definition remains based on clinical characteristic. In the present review, the diagnostic workup and the pathophysiology of the syndrome will be presented. Therapeutic approaches to ARDS, including lung protective ventilation, prone positioning, neuromuscular blockade, inhaled vasodilators, corticosteroids and recruitment manoeuvres will be reviewed. We will underline how a holistic framework of respiratory and hemodynamic support should be provided to patients with ARDS, aiming to ensure adequate gas exchange by promoting lung recruitment while minimizing the risk of ventilator-induced lung injury. To do so, lung recruitability should be considered, as well as the avoidance of lung overstress by monitoring transpulmonary pressure or airway driving pressure. In the most severe cases, neuromuscular blockade, prone positioning, and extra-corporeal life support (alone or in combination) should be taken into account.

Diaphragm ultrasound as indicator of respiratory effort in critically ill patients undergoing assisted mechanical ventilation: a pilot clinical study.

INTRODUCTION: Pressure-support ventilation, is widely used in critically ill patients; however, the relative contribution of patient's effort during assisted breathing is difficult to measure in clinical conditions. Aim of the present study was to evaluate the performance of ultrasonographic indices of diaphragm contractile activity (respiratory excursion and thickening) in comparison to traditional indices of inspiratory muscle effort during assisted mechanical ventilation. METHOD: Consecutive patients admitted to the ICU after major elective surgery who met criteria for a spontaneous breathing trial with pressure support ventilation were enrolled. Patients with airflow obstruction or after thoracic/gastric/esophageal surgery were excluded. Variable levels of inspiratory muscle effort were achieved by delivery of different levels of ventilatory assistance by random application of pressure support (0, 5 and 15 cmH2O). The right hemidiaphragm was evaluated by B- and M-mode ultrasonography to record respiratory excursion and thickening. Airway, gastric and oesophageal pressures, and airflow were recorded to calculate indices of respiratory effort (diaphragm and esophageal pressure-time product). RESULTS: 25 patients were enrolled. With increasing levels of pressure support, parallel reductions were found between diaphragm thickening and both diaphragm and esophageal pressure-time product (respectively, R = 0.701, p < 0.001 and R = 0.801, p < 0.001) during tidal breathing. No correlation was found between either diaphragm or esophageal pressure-time product and diaphragm excursion (respectively, R = -0.081, p = 0.506 and R = 0.003, p = 0.981), nor was diaphragm excursion correlated to diaphragm thickening (R = 0.093, p = 0.450) during tidal breathing. CONCLUSIONS: In patients undergoing in assisted mechanical ventilation, diaphragm thickening is a reliable indicator of respiratory effort, whereas diaphragm excursion should not be used to quantitatively assess diaphragm contractile activity.

Lung recruitment in acute respiratory distress syndrome: what is the best strategy?

PURPOSE OF REVIEW: Supporting patients with acute respiratory distress syndrome (ARDS) using a low tidal volume strategy is a standard practice in the ICU. Recruitment maneuvers can be used to augment other methods, like positive end-expiratory pressure and positioning, to improve aerated lung volume. Clinical practice varies widely, and optimal method and patient selection for recruitment maneuvers have not been determined. RECENT FINDINGS: Recent developments include experimental and clinical evidence that a stepwise extended recruitment maneuver may match the improvement in aerated lung volume seen with sustained inflation traditionally used, with less adverse effects. Positioning and other chest wall modifications may be useful adjuncts to recruitment maneuvers. In addition, evidence from clinical studies in the operating room suggests that recruitment maneuvers, as a component of an open lung strategy, may be helpful for mechanically ventilated patients with normal lungs. SUMMARY: As a component of ventilation strategy for patients with ARDS, the use of recruitment maneuvers, especially a stepwise maneuver, in addition to adequate positive end-expiratory pressure and appropriate positioning, is suggested by currently available data. Until their effect on clinical outcomes is further defined, the use of recruitment maneuvers in ARDS and other settings will continue to be guided by individual clinician experience and patient factors.

The effect of protein administration during critical illness depends on body composition: A secondary analysis of a prospective, observational study.

BACKGROUND & AIMS: The most adequate amount of protein that should be administered to critically ill patients is still debated and diverging findings are recently accumulating. We hypothesized that the effect of protein administration might depend on the amount of muscle mass. METHODS: A secondary analysis of a single-centre prospective observational study of body composition in critically ill patients. Mechanically-ventilated subjects with an expected intensive care unit (ICU) stay >72 h were enrolled. Within 24 h from ICU admission, bioimpedance-derived muscle mass (BIA MM) and rectus femoris cross-sectional area (RF CSA) were measured. The amount of proteins and calories administered on the 7th ICU day was recorded. RESULTS: We enrolled 94 subjects (65 males, actual body weight 72.9 ± 14.4 Kg, BMI 26.0 ± 4.8 kg/m2). Actual body weight was only weakly related to BIA MM (R = 0.478, p < 0.001) and not related to RF CSA (R = 0.114, p = 0.276). A higher protein intake was associated with a reduced mortality in the highest quartile of BIA MM (OR 0.68 [0.46; 0.99] per each 10 g of proteins administered) and in the third (OR 0.74 [0.57; 0.98]) and highest quartile of RF CSA (OR 0.68 [0.48; 0.96]). CONCLUSION: A higher protein intake was associated with lower ICU mortality only in patients admitted with a higher muscle mass, as either assessed by BIA or muscle ultrasound.

Methodologies and clinical applications of lower limb muscle ultrasound in critically ill patients: a systematic review and meta-analysis.

BACKGROUND: Reduced muscle mass upon admission and development of muscle wasting are frequent in critically ill patients, and linked to unfavorable outcomes. Muscle ultrasound is a promising instrument for evaluating muscle mass. We summarized the findings of lower limb muscle ultrasound values and investigated how the muscle ultrasound parameters of the examination or the patient characteristics influence the results. METHODS: Systematic review and meta-analysis of studies of lower limb ultrasound critically ill adults. PubMed, CINAHL, Embase, PEDro and Web of Science were searched. PRISMA guidelines were followed, and studies evaluated with the appropriate NIH quality assessment tool. A meta-analysis was conducted to compare the values at admission, short and long follow-up during ICU stay, and the association between baseline values and patient characteristics or ultrasound parameters was investigated with a meta-regression. RESULTS: Sixty-six studies (3839 patients) were included. The main muscles investigated were rectus femoris cross-sectional area (RF-CSA, n = 33/66), quadriceps muscle layer thickness (n = 32/66), and rectus femoris thickness (n = 19/66). Significant differences were found in the anatomical landmark and ultrasound settings. At ICU admission, RF-CSA ranged from 1.1 [0.73-1.47] to 6.36 [5.45-7.27] cm2 (pooled average 2.83 [2.29-3.37] cm2) with high heterogeneity among studies (I2 = 98.43%). Higher age, higher BMI, more distal landmark and the use of probe compression were associated with lower baseline muscle mass. CONCLUSIONS: Measurements of muscle mass using ultrasound varied with reference to patient characteristics, patient position, anatomical landmarks used for measurement, and the level of compression applied by the probe; this constrains the external validity of the results and highlights the need for standardization. STUDY REGISTRATION: PROSPERO CRD42023420376.

Exploring ultrasonographic diaphragmatic function in perioperative anesthesia setting: A comprehensive narrative review.

The ultrasound study of diaphragm function represents a valid method that has been extensively studied in recent decades in various fields, especially in intensive care, emergency, and pulmonology settings. Diaphragmatic function is pivotal in these contexts due to its crucial role in respiratory mechanics, ventilation support strategies, and overall patient respiratory outcomes. Dysfunction or weakness of the diaphragm can lead to respiratory failure, ventilatory insufficiency, and prolonged mechanical ventilation, making its assessment essential for patient management and prognosis in critical care and emergency medicine. While several studies have focused on diaphragmatic functionality in the context of intensive care, there has been limited attention within the field of anesthesia. The ultrasound aids in assessing diaphragmatic dysfunction (DD) by measuring muscle mass and contractility and their potential variations over time. Recent advancements in ultrasound imaging allow clinicians to evaluate diaphragm function and monitor it during mechanical ventilation more easily. In the context of anesthesia, early studies have shed light on the patho-physiological mechanisms of diaphragm function during general anesthesia. In contrast, more recent research has centered on evaluating diaphragmatic functionality at various phases of general anesthesia and by comparing diverse types of procedures or anatomical position during surgery. The objectives of this current review are to highlight the use of diaphragm ultrasound for the evaluation of diaphragmatic function during perioperative anesthesia and surgery. Specifically, we aim to examine the effects of anesthetic agents, surgical techniques, and anatomical positioning on diaphragmatic function. We explore how ultrasound aids in assessing DD by measuring muscle mass and contractility, as well as their potential variations over time. Additionally, we will discuss recent advancements in ultrasound imaging that allow clinicians to evaluate diaphragm function and monitor it during mechanical ventilation more easily.

Presepsin in Critical Illness: Current Knowledge and Future Perspectives.

The accurate identification of infections is critical for effective treatment in intensive care units (ICUs), yet current diagnostic methods face limitations in sensitivity and specificity, alongside cost and accessibility issues. Consequently, there is a pressing need for a marker that is economically feasible, rapid, and reliable. Presepsin (PSP), also known as soluble CD14 subtype (sCD14-ST), has emerged as a promising biomarker for early sepsis diagnosis. PSP, derived from soluble CD14, reflects the activation of monocytes/macrophages in response to bacterial infections. It has shown potential as a marker of cellular immune response activation against pathogens, with plasma concentrations increasing during bacterial infections and decreasing post-antibiotic treatment. Unlike traditional markers such as procalcitonin (PCT) and C-reactive protein (CRP), PSP specifically indicates monocyte/macrophage activation. Limited studies in critical illness have explored PSP's role in sepsis, and its diagnostic accuracy varies with threshold values, impacting sensitivity and specificity. Recent meta-analyses suggest PSP's diagnostic potential for sepsis, yet its standalone effectiveness in ICU infection management remains uncertain. This review provides a comprehensive overview of PSP's utility in ICU settings, including its diagnostic accuracy, prognostic value, therapeutic implications, challenges, and future directions.

Foot drop in critically ill patients: a narrative review of an elusive complication with intricate implications for recovery and rehabilitation.

Foot drop is a condition characterized by the inability to lift the foot upwards towards the shin bone. This condition may affect a proportion of critically ill patients, impacting on their recovery after the acute phase of the illness. The occurrence of foot drop in critical care patients may result from various underlying causes, including neurological injuries, muscular dysfunction, nerve compression, or vascular compromise. Understanding the etiology and assessing the severity of foot drop in these patients is essential for implementing appropriate management strategies and ensuring better patient outcomes. In this comprehensive review, we explore the complexities of foot drop in critically ill patients. We search for the potential risk factors that contribute to its development during critical illness, the impact it has on patients' functional abilities, and the various diagnostic techniques adopted to evaluate its severity. Additionally, we discuss current treatment approaches, rehabilitation strategies, and preventive measures to mitigate the adverse effects of foot drop in the critical care setting. Furthermore, we explore the roles of critical care physical therapists, neurologists, and other healthcare professionals in the comprehensive care of patients with foot drop syndrome and in such highlighting the importance of a multidisciplinary approach.