Bench assessment of PC-CMVs modes in transport and emergency ventilators under ICU conditions.

Although there has been an increase in bench test evaluation of mechanical ventilators in recent years, a publication gap remains in assessing Pressure Control Continuous Mandatory Ventilation Modes with a set point targeting scheme PC-CMVs. This study evaluates the operational variability in PC-CMVs of eleven transport and emergency ventilators used in ICU units in Brazil during the COVID-19 pandemic. The assessment involved a comprehensive set of test scenarios derived from existing literature and the NBR ISO 80601-2-12:2014 standard. Nine parameters were computed for five consecutive breaths, offering a comprehensive characterization of pressure and flow waveforms. Most ventilators had Inspiratory pressure and PEEP values that fell outside of the tolerance ranges. Notably, three mechanical ventilators failed to reach the target pressures within the specified inspiratory times during test scenarios with a higher time constant (τ). We observed significant differences among emergency and transport ventilators in all assessed parameters, indicating a performance difference in PC-CMVs modes. The current results might help clinicians determine which ventilator models are suitable for specific clinical situations, particularly when unfavorable circumstances compel doctors to use ventilators that may not provide adequate support for patients in intensive care units.

Prophylactic non-invasive positive pressure ventilation reduces complications and length of hospital stay after invasive thoracic procedures: a systematic review.

QUESTION: In patients undergoing invasive thoracic procedures, what are the effects of prophylactic non-invasive positive pressure ventilation (NIV)? DESIGN: Systematic review with meta-analysis of randomised trials. Methodological quality was assessed using the PEDro scale and the certainty of evidence with the GRADE approach. PARTICIPANTS: Patients undergoing invasive thoracic procedures. INTERVENTION: Continuous positive airway pressure (CPAP) or bi-level positive airway pressure (BiPAP). OUTCOME MEASURES: Length of hospital stay, postoperative pulmonary complications, need for tracheal intubation, mortality, hypoxaemia, pulmonary function and adverse events. Meta-analysis was performed for all outcomes. Subgroup analyses estimated the effects of CPAP and BIPAP independently. RESULTS: Sixteen trials with 1,814 participants were included. The average quality of the included studies was fair. Moderate certainty evidence indicated that NIV reduces postoperative pulmonary complications (RD -0.09, 95% CI -0.15 to -0.04) without increasing the rate of adverse events (RD 0.01, 95% CI -0.02 to 0.04). Low certainty evidence indicated that NIV reduces length of hospital stay (MD -1.4 days, 95% CI -2.2 to -0.5) compared with usual care. The effects on intubation and mortality rates were very close to no effect, indicating that NIV is safe. Subgroup analyses showed that the evidence for CPAP had more precise estimates that that for BiPAP. CONCLUSION: NIV reduces postoperative pulmonary complications and length of stay after invasive chest procedures without increasing the risk of adverse events. REGISTRATION: PROSPERO CRD42015019004.

Utilidad de la tomografía de impedancia eléctrica para la programación del ventilador mecánico en paciente crítico pediátrico, una alternativa dinámica y no invasiva: revisión de dos casos clínicos / Utility of electrical impedance tomography for mechanical ventilator programming in pediatric critical patients, a dynamic and non-invasive alternative: a review of two clinical cases

La tomografía por impedancia eléctrica (TIE) es una modalidad de monitorización funcional respiratoria por imagen, no invasiva y libre de radiación, que permite visualizar en tiempo real la ventilación pulmonar regional y global en pacientes adultos y pediátricos conectados a Ventilación Mecánica (VM). OBJETIVO: Se describe la utilidad de la TIE en dos pacientes críticos pediátricos, en quienes no fue factible realizar medición de mecánica pulmonar, como herramienta para el ajuste de parámetros ventilatorios. CASOS CLÍNICOS: Se presentan dos pacientes pediátricos de 27 y 11 meses con condiciones clínicas diferentes, conectados a VM, en quienes se utilizó la TIE como método de monitoreo de la distribución pulmonar y titulación de la presión positiva al final de la espiración (PEEP) óptima, con el objetivo de obtener una ventilación pulmonar más homogénea. Se presentan mediciones funcionales con diferentes niveles de PEEP y valores de distribución en las distintas regiones de interés (ROI), además de un flujograma de situaciones en las que la TIE podría resultar útil para el ajuste ventilatorio. CONCLUSIÓN: La información funcional proporcionada por la TIE, permitió monitorizar de forma dinámica la VM y optimizar los parámetros ventilatorios, facilitando la implementación de estrategias de protección pulmonar en ambos pacientes, imposibilitados de realizar una medición estática de la mecánica respiratoria.

The Electrical Impedance Tomography (EIT) is a non-invasive and radiation-free respiratory functional imaging monitoring modality that allows real-time visualization of regional and global lung ventilation in adult and pediatric patients connected to mechanical ventilation (MV). OBJECTIVE: This paper describes the utility of EIT in two critical pediatric patients for whom measuring pulmonary mechanics was not feasible. EIT is used as a tool for adjusting ventilatory parameters. CLINICAL CASES: Two pediatric patients aged 27 and 11 months, with different clinical conditions, connected to MV are presented. EIT was used to monitor lung distribution and titrate the optimal Positive End-Expiratory Pressure (PEEP), to achieve more homogeneous lung ventilation. Functional measurements are presented with different PEEP levels and distribution values in different regions of interest (ROI), along with a flowchart illustrating situations where EIT could be useful for ventilatory adjustment. CONCLUSION: The functional information provided by EIT, allowed dynamic monitoring of MV, optimizing ventilatory parameters and facilitating the implementation of lung protective strategies in both patients, unable to undergo static respiratory mechanics measurements.

Predictors for prescription of noninvasive ventilation in the postoperative period of cardiac surgery: a systematic review.

INTRODUCTION: The postoperative (PO) period after cardiac surgery is associated with the occurrence of respiratory complications. Noninvasive positive pressure ventilation (NIPPV) is largely used as a ventilatory support strategy after the interruption of invasive mechanical ventilation. However, the variables associated with NIPPV prescription are unclear. OBJECTIVE: To describe the literature on predictors of NIPPV prescription in patients during the PO period of cardiac surgery. MATERIALS AND METHODS: This systematic review was registered on the International Prospective Register of Systematic Reviews (PROSPERO) platform in December 2021 (CRD42021291973). Bibliographic searches were performed in February 2022 using the PubMed, Lilacs, Embase and PEDro databases, with no year or language restrictions. The Predictors for the prescription of NIPPV were considered among patients who achieved curative NIPPV. RESULTS: A total of 349 articles were identified, of which four were deemed eligible and were included in this review. Three studies were retrospective studies, and one was a prospective safety pilot study. The total sample size in each study ranged from 109 to 1657 subjects, with a total of 3456 participants, of whom 283 realized NIPPV. Curative NIPPV was the only form of NIPPV in 75% of the studies, which presented this form of prescription in 5-9% of the total sample size, with men around 65 years old being the majority of the participants receiving curative NIPPV. The main indication for curative NIPPV was acute respiratory failure. Only one study realized prophylactic NIPPV (28% of 32 participants). The main predictors for the prescription of curative NIPPV in the PO period of cardiac surgery observed in this study were elevated body mass index (BMI), hypercapnia, PO lung injury, cardiogenic oedema and pneumonia. CONCLUSIONS: BMI and lung alterations related to gas exchange disturbances are major predictors for NIPPV prescription in patients during the PO period of cardiac surgery. The identification of these predictors can benefit clinical decision-making regarding the prescription of NIPPV and help conserve human and material resources, thereby preventing the indiscriminate use of NIPPV.

The Impact of Increased PEEP on Hemodynamics, Respiratory Mechanics, and Oxygenation in Pediatric ARDS.

BACKGROUND: PEEP is a cornerstone treatment for children with pediatric ARDS. Unfortunately, its titration is often performed solely by evaluating oxygen saturation, which can lead to inadequate PEEP level settings and consequent adverse effects. This study aimed to assess the impact of increasing PEEP on hemodynamics, respiratory system mechanics, and oxygenation in children with ARDS. METHODS: Children receiving mechanical ventilation and on pressure-controlled volume-guaranteed mode were prospectively assessed for inclusion. PEEP was sequentially changed to 5, 12, 10, 8 cm H2O, and again to 5 cm H2O. After 10 min at each PEEP level, hemodynamic, ventilatory, and oxygenation variables were collected. RESULTS: A total of 31 subjects were included, with median age and weight of 6 months and 6.3 kg, respectively. The main reasons for pediatric ICU admission were respiratory failure caused by acute viral bronchiolitis (45%) and community-acquired pneumonia (32%). Most subjects had mild or moderate ARDS (45% and 42%, respectively), with a median (interquartile range) oxygenation index of 8.4 (5.8-12.7). Oxygen saturation improved significantly when PEEP was increased. However, although no significant changes in blood pressure were observed, the median cardiac index at PEEP of 12 cm H2O was significantly lower than that observed at any other PEEP level (P = .001). Fourteen participants (45%) experienced a reduction in cardiac index of > 10% when PEEP was increased to 12 cm H2O. Also, the estimated oxygen delivery was significantly lower, at 12 cm H2O PEEP. Finally, respiratory system compliance significantly reduced when PEEP was increased. At a PEEP of 12 cm H2O, static compliance had a median reduction of 25% in relation to the initial assessment (PEEP of 5 cm H2O). CONCLUSIONS: Although it may improve arterial oxygen saturation, inappropriately high PEEP levels may reduce cardiac output, oxygen delivery, and respiratory system compliance in pediatric subjects with ARDS with low potential for lung recruitability.

Prospective, randomized, controlled trial assessing the effects of a driving pressure-limiting strategy for patients with acute respiratory distress syndrome due to community-acquired pneumonia (STAMINA trial): protocol and statistical analysis plan.

BACKGROUND: Driving pressure has been suggested to be the main driver of ventilator-induced lung injury and mortality in observational studies of acute respiratory distress syndrome. Whether a driving pressure-limiting strategy can improve clinical outcomes is unclear. OBJECTIVE: To describe the protocol and statistical analysis plan that will be used to test whether a driving pressure-limiting strategy including positive end-expiratory pressure titration according to the best respiratory compliance and reduction in tidal volume is superior to a standard strategy involving the use of the ARDSNet low-positive end-expiratory pressure table in terms of increasing the number of ventilator-free days in patients with acute respiratory distress syndrome due to community-acquired pneumonia. METHODS: The ventilator STrAtegy for coMmunIty acquired pNeumoniA (STAMINA) study is a randomized, multicenter, open-label trial that compares a driving pressure-limiting strategy to the ARDSnet low-positive end-expiratory pressure table in patients with moderate-to-severe acute respiratory distress syndrome due to community-acquired pneumonia admitted to intensive care units. We expect to recruit 500 patients from 20 Brazilian and 2 Colombian intensive care units. They will be randomized to a driving pressure-limiting strategy group or to a standard strategy using the ARDSNet low-positive end-expiratory pressure table. In the driving pressure-limiting strategy group, positive end-expiratory pressure will be titrated according to the best respiratory system compliance. OUTCOMES: The primary outcome is the number of ventilator-free days within 28 days. The secondary outcomes are in-hospital and intensive care unit mortality and the need for rescue therapies such as extracorporeal life support, recruitment maneuvers and inhaled nitric oxide. CONCLUSION: STAMINA is designed to provide evidence on whether a driving pressure-limiting strategy is superior to the ARDSNet low-positive end-expiratory pressure table strategy for increasing the number of ventilator-free days within 28 days in patients with moderate-to-severe acute respiratory distress syndrome. Here, we describe the rationale, design and status of the trial.

Association between (ΔPaO2/FiO2)/PEEP and in-hospital mortality in patients with COVID-19 pneumonia: A secondary analysis.

BACKGROUND: The arterial pressure of oxygen (PaO2)/inspiratory fraction of oxygen (FiO2) is associated with in-hospital mortality in patients with Coronavirus Disease 2019 (COVID-19) pneumonia. ΔPaO2/FiO2 [the difference between PaO2/FiO2 after 24 h of invasive mechanical ventilation (IMV) and PaO2/FiO2 before IMV] is associated with in-hospital mortality. However, the value of PaO2 can be influenced by the end-expiratory pressure (PEEP). To the best of our knowledge, the relationship between the ratio of (ΔPaO2/FiO2)/PEEP and in-hospital mortality remains unclear. This study aimed to evaluate their association. METHODS: The study was conducted in southern Peru from April 2020 to April 2021. A total of 200 patients with COVID-19 pneumonia requiring IMV were included in the present study. We analyzed the association between (ΔPaO2/FiO2)/PEEP and in-hospital mortality by Cox proportional hazards regression models. RESULTS: The median (ΔPaO2/FiO2)/PEEP was 11.78 mmHg/cmH2O [interquartile range (IQR) 8.79-16.08 mmHg/cmH2O], with a range of 1 to 44.36 mmHg/cmH2O. Patients were divided equally into two groups [low group (< 11.80 mmHg/cmH2O), and high group (≥ 11.80 mmHg/cmH2O)] according to the (ΔPaO2/FiO2)/PEEP ratio. In-hospital mortality was lower in the high (ΔPaO2/FiO2)/PEEP group than in the low (ΔPaO2/FiO2)/PEEP group [18 (13%) vs. 38 (38%)]; hazard ratio (HR), 0.33 [95% confidence intervals (CI), 0.17-0.61, P < 0.001], adjusted HR, 0.32 (95% CI, 0.11-0.94, P = 0.038). The finding that the high (ΔPaO2/FiO2)/PEEP group exhibited a lower risk of in-hospital mortality compared to the low (ΔPaO2/FiO2)/PEEP group was consistent with the results from the sensitivity analysis. After adjusting for confounding variables, we found that each unit increase in (ΔPaO2/FiO2)/PEEP was associated with a 12% reduction in the risk of in-hospital mortality (HR, 0.88, 95%CI, 0.80-0.97, P = 0.013). CONCLUSIONS: The (ΔPaO2/FiO2)/PEEP ratio was associated with in-hospital mortality in patients with COVID-19 pneumonia. (ΔPaO2/FiO2)/PEEP might be a marker of disease severity in COVID-19 patients.

Pressure Support Ventilation Versus T-piece as Spontaneous Breathing Trials for Extubation of Patients with Chronic Obstructive Pulmonary Disease: A Systematic Review and Meta-analysis of Randomized Controlled Trials.

BACKGROUND: Weaning patients with COPD from mechanical ventilation (MV) presents a challenge, as literature on this topic is limited. This study compares PSV and T-piece during spontaneous breathing trials (SBT) in this specific population. METHODS: A search of PubMed, EMBASE, and Cochrane in September 2023 yielded four randomized controlled trials (RCTs) encompassing 560 patients. Among these, 287 (51%) used T-piece during SBTs. RESULTS: The PSV group demonstrated a significant improvement in the successful extubation rate compared to the T-piece (risk ratio [RR] 1.14; 95% confidence interval [CI] 1.03-1.26; p = 0.02). Otherwise, there was no statistically significant difference in the reintubation (RR 1.07; 95% CI 0.79-1.45; p = 0.67) or the ICU mortality rates (RR 0.99; 95% CI 0.63-1.55; p = 0.95). CONCLUSION: Although PSV in SBTs exhibits superior extubation success, consistent weaning protocols warrant further exploration through additional studies.

Expiratory Muscle Activity Counteracts Positive End-Expiratory Pressure and Is Associated with Fentanyl Dose in Patients with Acute Respiratory Distress Syndrome.

Rationale: Hypoxemia during mechanical ventilation might be worsened by expiratory muscle activity, which reduces end-expiratory lung volume through lung collapse. A proposed mechanism of benefit of neuromuscular blockade in acute respiratory distress syndrome (ARDS) is the abolition of expiratory efforts. This may contribute to the restoration of lung volumes. The prevalence of this phenomenon, however, is unknown. Objectives: To investigate the incidence and amount of end-expiratory lung impedance (EELI) increase after the administration of neuromuscular blocking agents (NMBAs), clinical factors associated with this phenomenon, its impact on regional lung ventilation, and any association with changes in pleural pressure. Methods: We included mechanically ventilated patients with ARDS monitored with electrical impedance tomography (EIT) who received NMBAs in one of two centers. We measured changes in EELI, a surrogate for end-expiratory lung volume, before and after NMBA administration. In an additional 10 patients, we investigated the characteristic signatures of expiratory muscle activity depicted by EIT and esophageal catheters simultaneously. Clinical factors associated with EELI changes were assessed. Measurements and Main Results: We included 46 patients, half of whom showed an increase in EELI of >10% of the corresponding Vt (46.2%; IQR, 23.9-60.9%). The degree of EELI increase correlated positively with fentanyl dosage and negatively with changes in end-expiratory pleural pressures. This suggests that expiratory muscle activity might exert strong counter-effects against positive end-expiratory pressure that are possibly aggravated by fentanyl. Conclusions: Administration of NMBAs during EIT monitoring revealed activity of expiratory muscles in half of patients with ARDS. The resultant increase in EELI had a dose-response relationship with fentanyl dosage. This suggests a potential side effect of fentanyl during protective ventilation.

The effects of positive end-expiratory pressure (PEEP) application on optic nerve sheath diameter in patients undergoing laparoscopic cholecystectomy: a randomized trial

Abstract Background: Positive end-expiratory pressure (PEEP) can overcome respiratory changes that occur during pneumoperitoneum application in laparoscopic procedures, but it can also increase intracranial pressure. We investigated PEEP vs. no PEEP application on ultrasound measurement of optic nerve sheath diameter (indirect measure of increased intracranial pressure) in laparoscopic cholecystectomy. Methods: Eighty ASA I-II patients aged between 18 and 60 years scheduled for elective laparoscopic cholecystectomy were included. The study was registered in the Australian New Zealand Clinical Trials (ACTRN12618000771257). Patients were randomly divided into either Group C (control, PEEP not applied), or Group P (PEEP applied at 10 cmH20). Optic nerve sheath diameter, hemodynamic, and respiratory parameters were recorded at six different time points. Ocular ultrasonography was used to measure optic nerve sheath diameter. Results: Peak pressure (PPeak) values were significantly higher in Group P after application of PEEP (p = 0.012). Mean respiratory rate was higher in Group C at all time points after application of pneumoperitoneum (p < 0.05). The mean values of optic nerve sheath diameters measured at all time points were similar between the groups (p > 0.05). The pulmonary dynamic compliance value was significantly higher in group P as long as PEEP was applied (p = 0.001). Conclusions: During laparoscopic cholecystectomy, application of 10 cmH2O PEEP did not induce a significant change in optic nerve sheath diameter (indirect indicator of intracranial pressure) compared to no PEEP application. It would appear that PEEP can be used safely to correct

Dynamic relative regional lung strain estimated by computed tomography and electrical impedance tomography in ARDS patients.

BACKGROUND: In the acute distress respiratory syndrome (ARDS), specific lung regions can be exposed to excessive strain due to heterogeneous disease, gravity-dependent lung collapse and injurious mechanical ventilation. Computed tomography (CT) is the gold standard for regional strain assessment. An alternative tool could be the electrical impedance tomography (EIT). We aimed to determine whether EIT-based methods can predict the dynamic relative regional strain (DRRS) between two levels of end-expiratory pressure (PEEP) in gravity-non-dependent and dependent lung regions. METHODS: Fourteen ARDS patients underwent CT and EIT acquisitions (at end-inspiratory and end-expiratory) at two levels of PEEP: a low-PEEP based on ARDS-net strategy and a high-PEEP titrated according to EIT. Three EIT-based methods for DRRS were compared to relative CT-based strain: (1) the change of the ratio between EIT ventilation and end-expiratory lung impedance in arbitrary units ([ΔZAU low-PEEP/EELIAU low-PEEP]/[ΔZAU high-PEEP/EELIAU high-PEEP]), (2) the change of ΔZ/EELI ratio calibrated to mL ([ΔZml low-PEEP/EELIml low-PEEP]/[ΔZml high-PEEP/EELIml high-PEEP]) using CT data, and (3) the relative change of ∆ZAU (∆ZAU low-PEEP/∆ZAU high-PEEP). We performed linear regressions analysis and calculated bias and limits of agreement to assess the performance of DRRS by EIT in comparison with CT. RESULTS: The DRRS assessed by (ΔZml low-PEEP/EELIml low-PEEP)/(ΔZml high-PEEP/EELIml high-PEEP) and ∆ZAU low-PEEP/∆ZAU high-PEEP showed good relationship and agreement with the CT method (R2 of 0.9050 and 0.8679, respectively, in non-dependent region; R2 of 0.8373 and 0.6588, respectively, in dependent region; biases ranging from - 0.11 to 0.51 and limits of agreement ranging from - 0.73 to 1.16 for both methods and lung regions). Conversely, DRRS based on EELIAU ([ΔZAU low-PEEP/EELIAU low-PEEP]/[ΔZAU high-PEEP/EELIAU high-PEEP]) exhibited a weak negative relationship and poor agreement with the CT method for both non-dependent and dependent regions (R2 ~ 0.3; bias of 3.11 and 2.08, and limits of agreement of - 2.13 to 8.34 and from - 1.49 to 5.64, respectively). CONCLUSION: Changes in DRRS during a PEEP trial in ARDS patients could be monitored using EIT, based on changes in ΔZmL/EELIml and ∆ZAU. The relative change ∆ZAU offers the advantage of not requiring CT data for calibration.

Outcomes of Invasive and Noninvasive Ventilation in a Haitian Emergency Department.

Background: Limited data exist on the outcomes of patients requiring invasive ventilation or noninvasive positive pressure ventilation (NIPPV) in low-income countries. To our knowledge, no study has investigated this topic in Haiti. Objectives: We describe the clinical epidemiology, treatment, and outcomes of patients requiring NIPPV or intubation in an emergency department (ED) in rural Haiti. Methods: This is an observational study utilizing a convenience sample of adult and pediatric patients requiring NIPPV or intubation in the ED at an academic hospital in central Haiti from January 2019-February 2021. Patients were prospectively identified at the time of clinical care. Data on demographics, clinical presentation, management, and ED disposition were extracted from patient charts using a standardized form and analyzed in SAS v9.4. The primary outcome was survival to discharge. Findings: Of 46 patients, 27 (58.7%) were female, mean age was 31 years, and 14 (30.4%) were pediatric (age <18 years). Common diagnoses were cardiogenic pulmonary edema, pneumonia/pulmonary sepsis, and severe asthma. Twenty-three (50.0%) patients were initially treated with NIPPV, with 4 requiring intubation; a total of 27 (58.7%) patients were intubated. Among those for whom intubation success was documented, first-pass success was 57.7% and overall success was 100% (one record missing data); intubation was associated with few immediate complications. Twenty-two (47.8%) patients died in the ED. Of the 24 patients who survived, 4 were discharged, 19 (intubation: 12; NIPPV: 9) were admitted to the intensive care unit or general ward, and 1 was transferred. Survival to discharge was 34.8% (intubation: 22.2%; NIPPV: 52.2%); 1 patient left against medical advice following admission. Conclusions: Patients with acute respiratory failure in this Haitian ED were successfully treated with both NIPPV and intubation. While overall survival to discharge remains relatively low, this study supports developing capacity for advanced respiratory interventions in low-resource settings.

Assessing swallowing disorders in adults on high-flow nasal cannula in critical and non-critical care settings. A scoping review protocol.

INTRODUCTION: The high-flow nasal cannula (HFNC) has become a widely used respiratory support system, which has proven to be effective in different populations. The facilitation of oral communication and feeding have been described as advantages of this support. Nevertheless, swallowing disorders associated with the use of HFNC have been postulated. However, such evidence is scattered in the literature, not systematically searched, and needs to be adequately summarised. This review aimed to explore the literature, to identify and map the evidence, regarding the frequency and methods of assessment of swallowing disorders in adult HFNC users, in both critical and non-critical units. MATERIALS AND METHODS: A scoping review will be conducted. A systematic search in MEDLINE (Ovid), Embase (Ovid), CENTRAL, CINAHL (EBSCOhost), and other resources will be conducted. Primary studies, in any language or publication status, assessing the incidence of swallowing disorders in adults with HFNC support will be included. Two reviewers will independently select studies and extract data. Disagreements will be resolved by consensus or a third reviewer. The results will be reported narratively, using tables and figures to support them. DISCUSSION: Positive end-expiratory pressure generated in the airway by HFNC could impair the proper swallowing performance. Knowing the methodological characteristics, the instruments or scales used to assess the presence of dysphagia, and the results of the studies may contribute to considering swallowing assessment in this population on a routine basis, as well as to guide the conduct of new studies that may respond to less researched areas in this topic. REGISTRATION: Registration number: INPLASY2022110078.

Effect of manual hyperinflation with versus without positive end-expiratory pressure on dynamic compliance in pediatric patients following congenital heart surgery: A randomized controlled trial.

BACKGROUND: We aimed to compare the effect of manual hyperinflation with versus without positive end-expiratory pressure (PEEP) on dynamic compliance of the respiratory system in pediatric patients undergoing congenital heart surgery; to assess the safety of the technique in this population. METHODS: This was a randomized controlled trial conducted at the pediatric intensive care unit (PICU) of a tertiary-care hospital. Patients admitted to the PICU following cardiac surgery and receiving postoperative mechanical ventilation were randomized to the experimental or control group. Patients in the experimental group (n = 14) underwent manual hyperinflation with a PEEP valve set at 5 cm H2O, once daily, during the first 48 hours after surgery. Patients allocated to the control group (n = 16) underwent manual hyperinflation without PEEP, at the same time points. Lung mechanics was assessed before (T0) and 5 minutes (T5) after manual hyperinflation. The primary endpoint was dynamic compliance. Secondary outcomes included oxygen saturation index, duration of mechanical ventilation, length of stay, 28-day mortality and safety. RESULTS: Demographic and clinical characteristics were comparable in both groups. There was no significant difference in dynamic compliance between times in each group (Day 1: (mean) 0.78 vs 0.81 and 0.70 vs 0.77; Day 2: 0.85 vs 0.78 and 0.67 vs 0.68 mL/kg/cm H2O, in experimental and control groups, respectively; P > .05). Mean deltas of dynamic compliance were not significantly different between groups. The proportion of patients extubated <72 hours after surgery was similar in experimental and control groups (43% vs 50%, respectively; P = .73). Oxygen saturation index, length of stay, and 28-day mortality were not significantly different between groups. None of the patients had hemodynamic instability. CONCLUSIONS: Manual hyperinflation was safe and well tolerated in pediatric patients following surgery for congenital heart disease. No significant change in dynamic compliance of the respiratory system or in oxygenation was observed with the use of manual hyperinflation with or without PEEP in this population.

Protocolo de uso de Ventilación Mecánica no Invasiva en la Unidad Adultos Área de Cuidados Intensivos / Protocol for the use of Noninvasive Mechanical Ventilation in the Adult Unit Intensive Care Area

La ventilación mecánica no invasiva (VMNI) se utiliza en pacientes con insuficiencia respiratoria aguda, para mejorar el in-tercambio de gases y reducir el trabajo respiratorio, sin la ne-cesidad de una vía aérea artificial1. Es una modalidad de asis-tencia ventilatoria que proporciona dos niveles de presión. Cabe destacar que la presión aumenta durante la fase inspiratoria de la respiración, aumentando el volumen corriente, mejorando así el intercambio de gases, aliviando los músculos respiratorios y esto regresa a una línea de base alta en la exhalación. El aumento de presión durante la fase inspiratoria IPAP (presión inspiratoria positiva en las vías respiratorias) es similar a la presión de so-porte de los ventiladores convencionales. Durante la espiración, el ajuste de la presión en los dispositivos diseñados principal-mente para VMNI se denomina presión espiratoria positiva en las vías respiratorias (EPAP). Se debe considerar que la EPAP es similar al PEEP en un ventilador convencional 2. El conoci-miento de su funcionalidad permite determinar en qué pacientes está indicado el uso de la ventilación no invasiva y establecer una estrategia de manejo inicial. Debe considerarse que, a mayor gravedad de la patología respiratoria, la ventilación no invasiva no redujo la necesidad de intubación ni la mortalidad 3,4. Estos resultados se relacionaron con estudios realizados en el con-texto de la pandemia de SARS COV 2 donde se encontró que, la ventilación no invasiva en pacientes con determinado grado de afectación respiratoria, redujo el uso de ventilación invasiva y la mortalidad 5-8.

Noninvasive mechanical ventilation (NIMV) is used in patients with acute respiratory failure to improve gas exchange and reduce the work of breathing, without the need for an artificial airway1. It is a modality of ventilatory assistance that provides two levels of pressure. It should be noted that the pressure in-creases during the inspiratory phase of breathing, increasing the tidal volume, thus improving gas exchange, relieving the respi-ratory muscles and this returns to a high baseline on exhalation. The pressure rise during the IPAP (inspiratory positive airway pressure) inspiratory phase is similar to pressure support venti-lation of conventional ventilators. During expiration, the pres-sure setting in devices designed primarily for NIMV is called expiratory positive airway pressure (EPAP). It should be consi-dered that EPAP is similar to PEEP on a conventional ventilator2. Knowledge of its functionality allows determining in which pa-tients the use of non-invasive ventilation is indicated and esta-blishing an initial management strategy. It should be considered that, with greater severity of the respiratory pathology, non-in-vasive ventilation did not reduce the need for intubation or mor-tality3,4. These results were related to studies carried out in the context of the SARS COV 2 pandemic where it was found that non-invasive ventilation in patients with a certain degree of res-piratory involvement reduced the use of invasive ventilation and mortality5-8.

Protocol-directed weaning versus conventional weaning from mechanical ventilation for neurocritical patients in an intensive care unit: a nonrandomized quasi-experimental study.

OBJECTIVE: To investigate whether protocol-directed weaning in neurocritical patients would reduce the rate of extubation failure (as a primary outcome) and the associated complications (as a secondary outcome) compared with conventional weaning. METHODS: A quasi-experimental study was conducted in a medical-surgical intensive care unit from January 2016 to December 2018. Patients aged 18 years or older with an acute neurological disease who were on mechanical ventilation > 24 hours were included. All patients included in the study were ready to wean, with no or minimal sedation, Glasgow coma score ≥ 9, spontaneous ventilatory stimulus, noradrenaline ≤ 0.2µgr/kg/ minute, fraction of inspired oxygen ≤ 0.5, positive end-expiratory pressure ≤ 5cmH2O, maximal inspiratory pressure < -20cmH2O, and occlusion pressure < 6cmH2O. RESULTS: Ninety-four of 314 patients admitted to the intensive care unit were included (50 in the Intervention Group and 44 in the Control Group). There was no significant difference in spontaneous breathing trial failure (18% in the Intervention Group versus 34% in the Control Group, p = 0.12). More patients in the Intervention Group were extubated than in the Control Group (100% versus 79%, p = 0.01). The rate of extubation failure was not signifiantly diffrent between the groups (18% in the Intervention Group versus 17% in the Control Group; relative risk 1.02; 95%CI 0.64 - 1.61; p = 1.00). The reintubation rate was lower in the Control Group (16% in the Intervention Group versus 11% in the Control Group; relative risk 1.15; 95%CI 0.74 - 1.82; p = 0.75). The need for tracheotomy was lower in the Intervention Group [4 (8%) versus 11 (25%) in the Control Group; relative risk 0.32; 95%CI 0.11 - 0.93; p = 0.04]. At Day 28, the patients in the Intervention Group had more ventilator-free days than those in the Control Group [28 (26 - 28) days versus 26 (19 - 28) days; p = 0.01]. The total duration of mechanical ventilation was shorter in the Intervention Group than in the Control Group [5 (2 - 13) days versus 9 (3 - 22) days; p = 0.01]. There were no diffrences in the length of intensive care unit stay, 28-day free from mechanical ventilation, hospital stay or 90-day mortality. CONCLUSION: Considering the limitations of our study, the application of a weaning protocol for neurocritical patients led to a high percentage of extubation, a reduced need for tracheotomy and a shortened duration of mechanical ventilation. However, there was no reduction in extubation failure or the 28-day free of from mechanical ventilation compared with the Control Group.ClinicalTrials.gov Registry: NCT03128086.

Factors associated with a nonresponse to prone positioning in patients with severe acute respiratory distress syndrome due to SARS-CoV-2.

OBJECTIVE: To identify risk factors for nonresponse to prone positioning in mechanically ventilated patients with COVID-19-associated severe acute respiratory distress syndrome and refractory hypoxemia in a tertiary care hospital in Colombia. METHODS: Observational study based on a retrospective cohort of mechanically ventilated patients with severe acute respiratory distress syndrome due to SARS-CoV-2 who underwent prone positioning due to refractory hypoxemia. The study considered an improvement ≥ 20% in the PaO2/FiO2 ratio after the first cycle of 16 hours in the prone position to be a 'response'. Nonresponding patients were considered cases, and responding patients were controls. We controlled for clinical, laboratory, and radiological variables. RESULTS: A total of 724 patients were included (58.67 ± 12.37 years, 67.7% males). Of those, 21.9% were nonresponders. Mortality was 54.1% for nonresponders and 31.3% for responders (p < 0.001). Variables associated with nonresponse were time from the start of mechanical ventilation to pronation (OR 1.23; 95%CI 1.10 - 1.41); preintubation PaO2/FiO2 ratio (OR 0.62; 95%CI 0.40 - 0.96); preprone PaO2/FiO2 ratio (OR 1.88. 95%CI 1.22 - 2.94); and radiologic multilobe consolidation (OR 2.12; 95%CI 1.33 - 3.33) or mixed pattern (OR 1.72; 95%CI 1.07 - 2.85) compared with a ground-glass pattern. CONCLUSION: This study identified factors associated with nonresponse to prone positioning in patients with refractory hypoxemia and acute respiratory distress syndrome due to SARS-CoV-2 receiving mechanical ventilation. Recognizing such factors helps identify candidates for other rescue strategies, including more extensive prone positioning or extracorporeal membrane oxygenation. Further studies are needed to assess the consistency of these findings in populations with acute respiratory distress syndrome of other etiologies.

Airway and Transpulmonary Driving Pressure by End-Inspiratory Holds During Pressure Support Ventilation.

BACKGROUND: The precision of quasi-static airway driving pressure (ΔP) assessed in pressure support ventilation (PSV) as a surrogate of tidal lung stress is debatable because persistent muscular activity frequently alters the readability of end-inspiratory holds. In this study, we used strict criteria to discard excessive muscular activity during holds and assessed the accuracy of ΔP in predicting global lung stress in PSV. Additionally, we explored whether the physiological effects of high PEEP differed according to the response of respiratory system compliance (CRS). METHODS: Adults with ARDS undergoing PSV were enrolled. An esophageal catheter was inserted to calculate lung stress through transpulmonary driving pressure (ΔPL). ΔP and ΔPL were assessed in PSV at PEEP 5, 10, and 15 cm H2O by end-inspiratory holds. CRS was calculated as tidal volume (VT)/ΔP. We analyzed the effects of high PEEP on pressure-time product per minute (PTPmin), airway pressure at 100 ms (P0.1), and VT over PTP per breath (VT/PTPbr) in subjects with increased versus decreased CRS at high PEEP. RESULTS: Eighteen subjects and 162 end-inspiratory holds were analyzed; 51/162 (31.5%) of the holds had ΔPL ≥ 12 cm H2O. Significant association between ΔP and ΔPL was found at all PEEP levels (P < .001). ΔP had excellent precision to predict ΔPL, with 15 cm H2O being identified as the best threshold for detecting ΔPL ≥ 12 cm H2O (area under the receiver operating characteristics 0.99 [95% CI 0.98-1.00]). CRS changes from low to high PEEP corresponded well with lung compliance changes (R2 0.91, P < .001) When CRS increased, a significant improvement of PTPmin and VT/PTPbr was found, without changes in P0.1. No benefits were observed when CRS decreased. CONCLUSIONS: In subjects with ARDS undergoing PSV, high ΔP assessed by readable end-inspiratory holds accurately detected potentially dangerous thresholds of ΔPL. Using ΔP to assess changes in CRS induced by PEEP during assisted ventilation may inform whether higher PEEP could be beneficial.

Air velocity spatial variability in open Compost-Bedded Pack Barn system with positive pressure ventilation.

In Compost-Bedded Pack Barn (CBP) systems, air velocity is linked with the thermal comfort of housed dairy cattle and bedding quality and, therefore, assessing ventilation efficiency is essential. In this context, the objective of this study was to evaluate and characterize dependence and spatial distribution of air velocity at the 1.5 m height (vair,M) and at bedding level (vair,B) in an open CBP system with positive pressure ventilation. The study was conducted in 2021, in a facility located in the Zona da Mata region, Minas Gerais, Brazil. The facility area was divided into a mesh composed of 55 equidistant points, where vair,M and vair,B data were collected in the morning (09:00 a.m.) and afternoon (03:00 p.m.) periods, during three weeks in Brazilian winter. Geostatistics techniques were used to assess dependence and spatial distribution. In both periods evaluated, there were a strong occurrence of spatial dependence and non-uniform vair,M and vair,B distributions. The vair,M and vair,B values were lower than recommended (1.8 m∙s-1) in more than 65.0% of the area. Adequate ventilation levels were observed only in the first 20.0 m of the facility, from Southeast to Northwest, because of the fan lines present.