Spontaneous Breathing Efforts Research Articles

Effect of Higher or Lower PEEP on Pendelluft During Spontaneous Breathing Efforts in Acute Hypoxemic Respiratory Failure

Effect of Higher or Lower PEEP on Pendelluft During Spontaneous Breathing Efforts in Acute Hypoxemic Respiratory Failure

Abstract 4135318: Comparison of Right Ventricular Function Changes Between Volume Control and Pressure Support Ventilation Modes: A Prospective Study Using S' Prime Values

Background: This study assesses changes in right ventricular function by measuring S' values during the transition from volume control-assist control (VC-AC) to pressure support ventilation (PSV). Transitioning from VC-AC to PSV reduces the mean airway pressure (P mean) which causes a decrease in right ventricular afterload and also potentially improves venous return and right ventricular preload. PSV allows spontaneous breathing efforts, possibly increasing cardiac output. Thus, we expect a consistent increase in S' value when changing ventilator modes. Methods: This prospective observational study included ICU patients on invasive mechanical ventilation for over 24 hours. The clinical team decided when to switch from VC-AC to PSV. An average of three S' measurements was taken during VC-AC and within 10 minutes of transitioning to PSV. Sedation, vasopressor use, and Richmond Agitation-Sedation Scale scores were consistent throughout the measurements. The study was approved by the Albert Einstein College of Medicine IRB (#2023-15068) Results: Seventeen patients were included in the study, with an average age of 61.29 years (SD 11.39). Of these, 6 (35.3%) were female. The mean S' during VC-AC was 12.79 ± 4.52, and upon transitioning to PSV, it was 14.56 ± 3.89 (p-value 0.47). The intra-observer variability for S' was 5.3%. Of the seventeen patients, 5/17 (29%) showed an S' change of less than 5.3% and were deemed to have no significant variation; 7/17 (41%) experienced a significant decrease in S' (15.41% ± 7.29% SD), while the remaining 5/17 (29%) showed a significant increase (19.31 ± 13.23%). Conclusion: Our study demonstrates that transitioning from VC-AC to PSV results in variable changes in right ventricular systolic function, as indicated by S' values. Contrary to our expectations of a consistent increase, the interplay between S' values and ventilator mode changes appears to be non-linear, suggesting other factors may influence cardiopulmonary interactions in spontaneously breathing ventilated patients. These findings highlight the complexity of these interactions, underscoring the need for individualized patient management and paving the way for further research with a larger cohort.

INhaled Sedation versus Propofol in REspiratory failure in the Intensive Care Unit (INSPiRE-ICU1): protocol for a randomised, controlled trial

IntroductionSedation in mechanically ventilated adults in the intensive care unit (ICU) is commonly achieved with intravenous infusions of propofol, dexmedetomidine or benzodiazepines. Significant limitations associated with each can impact their...

Detection of spontaneous breathing during an apnea test in a patient with suspected brain death using electrical impedance tomography: a case report

IntroductionThe apnea test (AT) is a crucial procedure in determining brain death (BD), with detection of spontaneous breathing efforts serving as a key criterion. Numerous national statutes mandate complete disconnection of the patient from the ventilator during the procedure to open the airway directly to the atmosphere. These regulations mandate visual observation as an exclusive option for detecting breathing efforts. However, reliance on visual observation alone can pose challenges in identifying subtle respiratory movements.Case PresentationThis case report presents a 55-year-old morbidly obese male patient with suspected BD due to cerebral hemorrhage undergoing an AT. The AT was performed with continuous electrical impedance tomography (EIT) monitoring. Upon detection of spontaneous breathing movements by both visual observation and EIT, the AT was aborted, and the patient was reconnected to the ventilator. EIT indicated a shift in ventilation distribution from the ventral to the dorsal regions, indicating the presence of spontaneous breathing efforts. EIT results also suggested the patient experienced a slow but transient initial recovery phase, likely due to atelectasis induced by morbid obesity, before returning to a steady state of ventilatory support.ConclusionThe findings suggest EIT could enhance the sensitivity and accuracy of detecting spontaneous breathing efforts, providing additional insights into the respiratory status of patients during the AT.

Combined Use of Alkaline Agents With Low-Flow Extracorporeal Carbon Dioxide Removal in Carbon Dioxide Inhalation Models Preserving Inspiratory Efforts.

Low-flow extracorporeal CO 2 removal (ECCO 2 R), managed using a renal replacement platform, is useful in achieving lung-protective ventilation with low tidal volume. However, its capacity for CO 2 elimination is limited. Whether this system is valuable in reducing strong inspiratory efforts in respiratory failure is unclear. The combined use of alkaline agents with low-flow ECCO 2 R might be useful in hypercapnic subjects preserving inspiratory efforts. This study examined the effects of low-flow ECCO 2 R on respiratory status and investigated the effects of NaHCO 3 , trometamol, and saline on respiratory status during low-flow ECCO 2 R in CO 2 inhalation models. Although low-flow ECCO 2 R did not significantly change the respiratory rate (92.2% ± 24.3% [mean ± standard deviation] of that before ECCO 2 R), it reduced minute ventilation (MV) (78.9% ± 13.5% of that before ECCO 2 R). The addition of NaHCO 3 improved acidemia but did not change MV compared with that of the saline group (0.451 ± 0.026 L/min/kg body weight [BW] vs. 0.556 ± 0.138 L/min/kg BW, respectively). The addition of trometamol improved acidemia and reduced MV compared with that of the saline group (0.381 ± 0.050 L/min/kg BW vs. 0.556 ± 0.138 L/min/kg BW, respectively). The total amounts of CO 2 removed during ECCO 2 R in the NaHCO 3 group were lower than those in the saline and trometamol groups. The low-flow ECCO 2 R reduced MV in subjects preserving spontaneous breathing efforts with CO 2 overload. The addition of NaHCO 3 improved acidemia but did not change MV, whereas the addition of trometamol improved acidemia and reduced MV.

Hyperventilation worsens inflammatory lung injury in spontaneously breathing rats.

Here, we investigated the effects of hyperventilation on acute lung injury (ALI) in spontaneously breathing rats. Wistar rats were randomized to receive either intraperitoneal lipopolysaccharides (LPS) or saline, and intravenous infusion of NH4Cl (to induce metabolic acidosis and hyperventilation) or saline. Four groups were established: control-control (C-C), control-hyperventilation (C-HV), LPS-control (LPS-C), and LPS-hyperventilation (LPS-HV). Venous blood gases were collected before and after NH4Cl infusion and analyzed to confirm the presence of metabolic acidosis and hyperventilation. After euthanasia, lung injury was assessed using the ALI score, morphometric quantification of perivascular edema, neutrophil counts in the bronchoalveolar lavage, and mRNA expression of biological markers in the lung tissue. Hyperventilation induced inflammatory lung injury in previously healthy lungs and exacerbated injuries previously induced by LPS (ALI score: C-C=0.14 [IQR 0.12; 0.14]; C-HV=0.36 [IQR 0.31; 0.37]; LPS-C=0.51 [IQR 0.50; 0.54]; LPS-HV=0.58 [IQR 0.56; 0.62]; p<0.01). Perivascular edema, neutrophil counts in bronchoalveolar lavage, and amphiregulin mRNA expression were higher in the LPS-HV group compared to the control group. Hyperventilation increased inflammatory injury in rats with ALI during spontaneous ventilation. These results suggest that the impact of vigorous spontaneous breathing efforts on worsening inflammatory lung injury warrants further investigation.

Feasibility of HEMS performed prehospital extracorporeal-cardiopulmonary resuscitation in paediatric cardiac arrests; two case reports

IntroductionA broad range of pathophysiologic conditions can lead to cardiopulmonary arrest in children. Some of these children suffer from refractory cardiac arrest, not responding to basic and advanced life support. Extracorporeal-Cardiopulmonary Resuscitation (E-CPR) might be a life-saving option for this group. Currently this therapy is only performed in-hospital, often necessitating long transport times, thereby negatively impacting eligibility and chances of survival. We present the first two cases of prehospital E-CPR in children performed by regular Helicopter Emergency Medical Services (HEMS).Case presentationsThe first patient was a previously healthy 7 year old boy who was feeling unwell for a couple of days due to influenza. His course deteriorated into a witnessed collapse. Direct bystander CPR and subsequent ambulance advanced life support was unsuccessful in establishing a perfusing rhythm. While doing chest compressions, the patient was seen moving both his arms and making spontaneous breathing efforts. Echocardiography however revealed a severe left ventricular impairment (near standstill). The second patient was a 15 year old girl, known with bronchial asthma and poor medication compliance. She suffered yet another asthmatic attack, so severe that she progressed into cardiac arrest in front of the attending ambulance and HEMS crews. Despite maximum bronchodilator therapy, intubation and the exclusion of tension pneumothoraxes and dynamic hyperinflation, no cardiac output was achieved.InterventionAfter consultation with the nearest paediatric E-CPR facilities, both patients were on-scene cannulated by regular HEMS. The femoral artery and vein were cannulated (15-17Fr and 21Fr respectively) under direct ultrasound guidance using an out-of-plane Seldinger approach. Extracorporeal Life Support flow of 2.1 and 3.8 l/min was established in 20 and 16 min respectively (including preparation and cannulation). Both patients were transported uneventfully to the nearest paediatric intensive care with spontaneous breathing efforts and reactive pupils during transport.ConclusionThis case-series shows that a properly trained regular HEMS crew of only two health care professionals (doctor and flight nurse) can establish E-CPR on-scene in (older) children. Ambulance transport with ongoing CPR is challenging, even more so in children since transportation times tend to be longer compared to adults and automatic chest compression devices are often unsuitable and/or unapproved for children. Prehospital cannulation of susceptible E-CPR candidates has the potential to reduce low-flow time and offer E-CPR therapy to a wider group of children suffering refractory cardiac arrest.

Evaluation of IntelliVent-ASV® and PS-SIMV Mode Using Ultrasound (US) Measurements in Terms of Diaphragm Atrophy.

Mechanical ventilation is a life-saving intervention for critically ill patients, but it can also lead to diaphragm atrophy, which may prolong the duration of mechanical ventilation and the length of stay in the intensive care unit. IntelliVent-ASV® (Hamilton Medical, Rhäzüns, Switzerland) is a new mode of ventilation that has been developed to reduce diaphragm atrophy by promoting spontaneous breathing efforts. In this study, we aimed to evaluate the effectiveness of IntelliVent-ASV® and pressure support-synchronized intermittent mandatory ventilation (PS-SIMV) mode in reducing diaphragm atrophy by measuring diaphragm thickness using ultrasound (US) imaging. We enrolled 60 patients who required mechanical ventilation due to respiratory failure and were randomized into two groups: IntelliVent-ASV®and PS-SIMV. We measured the diaphragm thickness using US imaging at admission and on the seventh day of mechanical ventilation. Our results showed that diaphragm thickness decreased significantly in the PS-SIMV group but remained unchanged in the IntelliVent-ASV®group. The difference in diaphragm thickness between the two groups was statistically significant on the seventh day of mechanical ventilation. IntelliVent-ASV®may reduce diaphragm atrophy by promoting spontaneous breathing efforts. Our study suggests that this new mode of ventilation may be a promising approach to preventing diaphragm atrophy in mechanically ventilated patients. Further studies using invasive measures of diaphragm function are warranted to confirm these findings.

Regional peak flow as a novel approach to assess regional pulmonary mechanics by electrical impedance tomography: an observational validation study.

Spontaneous breathing efforts during mechanical ventilation are a widely accepted weaning approach for acute respiratory distress syndrome (ARDS) patients. These efforts can be too vigorous, possibly inflicting lung and diaphragm damage. Higher positive end expiratory pressure (PEEP) levels can be used to lower the magnitude of vigorous breathing efforts. Nevertheless, PEEP titrating tools are lacking in spontaneous mechanical ventilation (SMV). Therefore, the aim is to develop an electrical impedance tomography (EIT) algorithm for quantifying regional lung mechanics independent from a stable plateau pressure phase based on regional peak flow (RPF) by EIT, which is hypothetically applicable in SMV and to validate this algorithm in patients on controlled mechanical ventilation (CMV). The RPF algorithm quantifies a cumulative overdistension (ODRPF) and collapse (CLRPF) rate and is validated in a prospective cohort of mechanically ventilated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) patients on CMV. ODRPF and CLRPF are compared with compliance-based cumulative overdistension (ODP500) and collapse (CLP500) rates from the Pulmovista 500 EIT device at multiple PEEP levels (PEEP 10 cmH2O to PEEP 24 cmH2O) in EIT measurements from CMV patients by linear mixed models, Bland-Altman analysis and intraclass correlation coefficient (ICC). Seventy-eight patients were included. Linear mixed models revealed an association between ODRPF and ODP500 of 1.02 (0.98-1.07, P<0.001) and between CLRPF and CLP500 of 0.93 (0.80-1.05, P<0.001). ICC values ranged from 0.78 to 0.86 (P<0.001) for ODRPF and ODP500 and from 0.70 to 0.85 (P<0.001) for CLRPF and CLP500 (PEEP 10 to PEEP 24). The mean bias between ODRPF and ODP500 in these PEEP levels ranged from 0.80% to 4.19% and from -1.31% to 0.13% between CLRPF and CLP500. A RPF approach for quantifying regional lung mechanics showed a moderate to good agreement in coronavirus disease 2019 (COVID-19) related ARDS patients on CMV compared to the compliance-based approach. This, in addition to being independent of a plateau pressure phase, indicates that the RPF approach is a valid method to explore for quantifying regional lung mechanics in SMV.

Automatic air volume control system for ventilation of two patients using a single ventilator: a large animal model study

The COVID-19 pandemic outbreak led to a global ventilator shortage. Hence, various strategies for using a single ventilator to support multiple patients have been considered. A device called Ventil previously validated for independent lung ventilation was used in this study to evaluate its usability for shared ventilation. We performed experiments with a total number of 16 animals. Eight pairs of pigs were ventilated by a ventilator or anesthetic machine and by Ventil for up to 27 h. In one experiment, 200 ml of saline was introduced to one subject’s lungs to reduce their compliance. The experiments were analyzed in terms of arterial blood gases and respiratory parameters. In addition to the animal study, we performed a series of laboratory experiments with artificial lungs (ALs). The resistance and compliance of one AL (affected) were altered, while the tidal volume (TV) and peak pressure (Ppeak) in the second (unaffected) AL were analyzed. In addition, to assess the risk of transmission of pathogens between AL respiratory tracts, laboratory tests were performed using phantoms of virus particles. The physiological level of analyzed parameters in ventilated animals was maintained, except for CO2 tension, for which a permissive hypercapnia was indicated. Experiments did not lead to injuries in the animal’s lungs except for one subject, as indicated by CT scan analysis. In laboratory experiments, changes in TV and Ppeak in the unaffected AL were less than 11%, except for 2 cases where the TV change was 20%. No cross-contamination was found in simulations of pathogen transmission. We conclude that ventilation using Ventil can be considered safe in patients undergoing deep sedation without spontaneous breathing efforts.

A Novel Agnostic Respiratory Stimulant as a Treatment for Apnea of Prematurity: A Proof-of-Concept Study.

Aim/Objective: ENA-001 is a novel selective antagonist of large-conductance BK (big potassium) channels located in the carotid bodies, where they act as chemoreceptors that sense low arterial oxygen levels and establish a feedback loop to brainstem nuclei responsible for initiating spontaneous breathing and maintaining adequate oxygen to tissues. ENA-001 attenuates respiratory depression induced by a variety of chemical agents, essentially "agnostic" to the precipitating drug (e.g., opioid(s), benzodiazepine, alcohol, or propofol). But it had not been tested against respiratory depression resulting from a physiological cause, such as apnea of prematurity (AOP). This proof-of-principle study used a well-described animal model (premature lamb) to test the effectiveness of ENA-001 in the setting of an under-developed respiratory control system, similar to that in human AOP.Materials and Methods: A set of twin lambs was delivered prematurely via caesarian section at 135 ± 2 d gestational age (GA). An arterial catheter was connected to a transducer for pressure monitoring and a venous catheter was connected to a pump for continuous infusion of 5% dextrose in water (D5W). Lambs were to receive four mechanical breaths for lung recruitment and then started on continuous positive airway pressure (CPAP). After a stabilization period of 15 minutes, the protocol called for the first lamb to be started on continuous infusion of ENA-001, with ascending dose hourly (0.4, 1.1, 2.0, 12.0 mg/kg/hr), while the second lamb was to serve as a sham (D5W) control. At least 10 representative breaths free of artifact from motion or atypical breaths were recorded using a pulmonary function system designed for neonatal research. To maintain a stable plane of anesthesia, repeat doses of fentanyl (1 µg IM) were given as needed based on blood pressure response to stimulation.Results: Two male lambs were delivered. Unexpectedly, neither lamb exhibited a drive for spontaneous breathing. Each required manual ventilation, with a complete absence of spontaneous effort. Despite the poor prognosis owing to the absence of ventilatory effort, continuous infusion of the first dose of ENA-001 was started 20 minutes after birth. The test animal continued to require manual ventilation, which was continued for an additional 10 minutes. An intravenous (IV) bolus of ENA-001 was given. Nearly instantaneously following the delivery of the IV bolus, the lamb began breathing spontaneously and did not require manual intervention for the remainder of the study. The sham animal was delivered approximately an hour following the test animal. As with the test animal, the sham animal lacked spontaneous breathing efforts. A decision was made to manually ventilate for 30 minutes to match the course for the test animal. At the 30-minute time point, an IV bolus infusion of ENA-001 was delivered. Nearly instantaneously following the delivery of the IV bolus, the lamb began breathing spontaneously. After several minutes, the spontaneous breathing efforts abated, and manual ventilation was resumed. The animal was then sacrificed for tissue harvest.Conclusion: These results suggest that ENA-001 might be an effective therapy, alone or as a co-medication, for the treatment of AOP. They further suggest that ENA-001 might have broader applications in situations of neurological ventilatory insufficiency.

Mechanical Power Differs Between Pressure-Controlled Ventilation and Different Volume-Controlled Ventilation Modes

OBJECTIVES:Mechanical power (MP) is a way of estimating the energy delivered by the ventilator to the patient. For both volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV) methods have been described to calculate the MP. The pressure-volume (PV) loop, from which the MP is calculated, is different for VCV compared with PCV. We aimed to compare the MP of VCV with zero pause time (VCV-0), VCV with 10% pause time (VCV-10), and PCV within patients in different patient categories based on severity of lung injury.DESIGN:In a proof-of-concept study, we enrolled 46 mechanically ventilated patients without spontaneous breathing efforts. Baseline measurements were done in pressure-controlled mode. Subsequently, measurements were done in VCV-0 and VCV-10. Tidal volume and all other settings were kept the same.SETTING:ICU, single university medical center.PATIENTS:Fifty-eight cases in 46 patients on controlled ventilation modes.INTERVENTIONS:Comparison between the MP of PCV, VCV-0, and VCV-10.MEASUREMENT AND MAIN RESULTS:The mean MP of VCV-0, VCV-10, and PCV was 19.30, 21.80, and 20.87 J/min, respectively (p < 0.05 for all comparisons). The transpulmonary MP of VCV-0, VCV-10, and PCV was 6.75, 8.60, and 7.99 J/min, respectively (p < 0.05 for all comparisons).CONCLUSIONS:In patients ventilated in a controlled mode, VCV without pause time had the lowest MP followed by PCV. VCV with 10% pause time had the highest MP.

Estimating the incidence of spontaneous breathing effort of mechanically ventilated patients using a non-linear auto regressive (NARX) model

Background and objectiveMechanical ventilation (MV) provides breathing support for acute respiratory distress syndrome (ARDS) patients in the intensive care unit, but is difficult to optimize. Too much, or too little of pressure or volume support can cause further ventilator-induced lung injury, increasing length of MV, cost and mortality. Patient-specific respiratory mechanics can help optimize MV settings. However, model-based estimation of respiratory mechanics is less accurate when patient exhibit un-modeled spontaneous breathing (SB) efforts on top of ventilator support. This study aims to estimate and quantify SB efforts by reconstructing the unaltered passive mechanics airway pressure using NARX model. MethodsNon-linear autoregressive (NARX) model is used to reconstruct missing airway pressure due to the presence of spontaneous breathing effort in mv patients. Then, the incidence of SB patients is estimated. The study uses a total of 10,000 breathing cycles collected from 10 ARDS patients from IIUM Hospital in Kuantan, Malaysia. In this study, there are 2 different ratios of training and validating methods. Firstly, the initial ratio used is 60:40 which indicates 600 breath cycles for training and remaining 400 breath cycles used for testing. Then, the ratio is varied using 70:30 ratio for training and testing data. Results and discussionThe mean residual error between original airway pressure and reconstructed airway pressure is denoted as the magnitude of effort. The median and interquartile range of mean residual error for both ratio are 0.0557 [0.0230 - 0.0874] and 0.0534 [0.0219 - 0.0870] respectively for all patients. The results also show that Patient 2 has the highest percentage of SB incidence and Patient 10 with the lowest percentage of SB incidence which proved that NARX model is able to perform for both higher incidence of SB effort or when there is a lack of SB effort. ConclusionThis model is able to produce the SB incidence rate based on 10% threshold. Hence, the proposed NARX model is potentially useful to estimate and identify patient-specific SB effort, which has the potential to further assist clinical decisions and optimize MV settings.

Assessment of respiratory system compliance under pressure control ventilation without an inspiratory pause maneuver

Objective. The measurement of the static compliance of the respiratory system (C stat) during mechanical ventilation requires zero end-inspiratory flow. An inspiratory pause maneuver is needed if the zero end-inspiratory flow condition cannot be satisfied under normal ventilation. Approach. We propose a method to measure the quasi-static respiratory compliance (C qstat) under pressure control ventilation mode without the inspiratory pause maneuver. First, a screening strategy was applied to filter out breaths affected strongly by spontaneous breathing efforts or artifacts. Then, we performed a virtual extrapolation of the flow-time waveform when the end-inspiratory flow was not zero, to allow for the calculation of C qstat for each kept cycle. Finally, the output C qstat was obtained as the average of the smallest 40 C qstat measurements. The proposed method was validated against the gold standard C stat measured from real clinical settings and compared with two reported algorithms. The gold standard C stat was obtained by applying an end-inspiratory pause maneuver in the volume-control ventilation mode. Main results. Sixty-nine measurements from 36 patients were analyzed. The Bland–Altman analysis showed that the bias of agreement for C qstat versus the gold standard measurement was –0.267 ml/cmH2O (95% limits of agreement was –4.279 to 4.844 ml/cmH2O). The linear regression analysis indicated a strong correlation (R 2 = 0.90) between the C qstat and gold standard. Significance. The results showed that the C qstat can be accurately estimated from continuous ventilator waveforms, including spontaneous breathing without an inspiratory pause maneuver. This method promises to provide continuous measurements compliant with mechanical ventilation.

Advanced cuff pressure control ventilation (ACPCV); a bench study of a new concept of mechanical ventilation

The concept of advanced cuff pressure control ventilation (ACPCV) is that the endotracheal tube (ETT) cuff volume could be controlled and allowed to exhale the gas through the vocal cords. The potential advantages of ACPCV are reduction of dead space, reduction of expiratory airway resistance, and preservation of vocal cord function. We developed the ACPCV system and investigated its performance in bench studies. The ETT cuff volume was regulated via four steps, depending on airway pressure and tracheal pressure. Two ventilatory settings were examined under several rates of spontaneous breathing efforts. Imposed expiratory resistance (RE ), imposed expiratory work of breathing (WOB), and auto-PEEP of ACPCV were compared with continuous mandatory ventilation (CMV). RE of ACPCV (2.6 ± 0.5 cm H2O/l/s) was significantly lower than that of CMV (11.6 ± 1.6 cm H2O/l/s) (p < 0.001). Expiratory WOB of ACPCV (0.25 ± 0.02 J/l) was significantly lower than that of CMV (0.54 ± 0.10 J/l) (p < 0.001). Auto-PEEP of ACPCV (−0.6 ± 0.2 cm H2O) was significantly lower than that of CMV (1.1 ± 0.7 cm H2O) (p < 0.001). ACPCV can significantly reduce RE and expiratory WOB by controlling the ETT cuff volume in synchronisation with mechanical ventilation.

Electrical Impedance Tomography for Positive End-Expiratory Pressure Setting after Bilateral Lung Transplantation

Purpose After lung transplantation (LT) the magnitude of graft recruitability is variable, therefore postoperative personalized positive end-expiratory pressure (PEEP) setting is desirable in order to minimize ventilator-induced lung injury and to reduce pulmonary complications [1]. Electrical impedance tomography (EIT) offers this opportunity by bedside estimating both alveolar collapse and overdistension throughout a decremental PEEP trial [2]. This study aims to assess the reliability of EIT-based PEEP selection compared to PEEP titration to the best respiratory system static compliance (Crs) after LT [3]. Methods All patients were deeply sedated without spontaneous breathing efforts and ventilated in volume control mode with lung-protective settings [1]. At Intensive Care Unit admission after LT, PEEP was adjusted to best Crs (PEEPCrs). Subsequently, an EIT-based decremental PEEP trial was performed through a dedicated device (Pulmovista500, Drӓger-Medical, Germany). EIT optimal PEEP (PEEPEIT) was defined as the best compromise between lung collapse and overdistension [2]. PEEPEIT was compared with PEEPCrs using Mann-Whitney test. Data are expressed as median and interquartile ranges. Results Six bilateral LT patients were enrolled (4 pulmonary fibrosis, 1 bronchiectasis and 1 bronchiolitis obliterans syndrome). Age was 57 (52-63) years and body mass index was 23.3 (20.0-25.6) kg/m2. PEEPEIT was 9 (8-13) cmH2O, not significantly different from PEEPCrs [9 (7-9) cmH2O, p = 0.413]. The loss of lung compliance due to lung collapse observed with PEEPEIT [4.8% (4.1-7.3%)] was comparable to that obtained with PEEPCrs [8.0% (6.5-12.3%) (p = 0.195)]. The loss of lung compliance consequent to lung overdistension was similar between PEEPEIT and PEEPCrs [4.0% (2.5-5.0%) vs. 1.8% (1.1-2.4%) (p = 0.134)]. Conclusion After LT, EIT is a reliable tool for individualized PEEP setting, with analogous performances to PEEP titration to the best Crs. Whether EIT is to be preferred for this purpose and the overall clinical influence of personalizing PEEP based on EIT after LT remain to be determined.

Assessing SB effort via a non-invasive model-based method in mechanically ventilated patients in Malaysian ICU hospital

Patients with Acute Respiratory Distress Syndrome (ARDS) required mechanical ventilation (MV) for breathing support. However, some MV patients encountered spontaneous breathing (SB) efforts while fully sedated which can obscure the true underlying respiratory mechanics of these patients. Thus, a model-based method is required to reconstruct the missing pressure and calculate the breathing effort that produced by the patients without additional clinical protocols or invasive procedure. In this paper, results of spontaneous breathing effort in Malaysian critically-ill patients adopting the developed pressure reconstruction model are presented. By using the pressure reconstruction model, the SB affected pressure waveform is reconstructed to approximate true respiratory mechanics and quantifies the SB effort. The SB breathing efforts were computed and compared with the results from Christchurch Hospital, New Zealand. The substitute measure of SB effort can be indicated from the difference between the reconstructed and unreconstructed pressure. Results shows that all patients from both cohorts exhibited SB effort with the highest SB effort at 11.48% for Malaysian patient and 21.07% for Christchurch patient. Overall, the well-developed non-invasive pressure reconstruction method is able to measure the SB effort produced by Malaysian MV patients that help the clinicians in selecting the optimal MV setting. This first non-invasive guidance in selecting the optimal setting of MV in Malaysia is potentially reduced the ICU cost and improve the MV management in Malaysian hospital.

Interpretation of the transpulmonary pressure in the critically ill patient.

Mechanical ventilation is a life-saving procedure, which takes over the function of the respiratory muscles while buying time for healing to take place. However, it can also promote or worsen lung injury, so that careful monitoring of respiratory mechanics is suggested to titrate the level of support and avoid injurious pressures and volumes to develop. Standard monitoring includes flow, volume and airway pressure (Paw). However, Paw represents the pressure acting on the respiratory system as a whole, and does not allow to differentiate the part of pressure that is spent di distend the chest wall. Moreover, if spontaneous breathing efforts are allowed, the Paw is the sum of that applied by the ventilator and that generated by the patient. As a consequence, monitoring of Paw has significant shortcomings. Assessment of esophageal pressure (Pes), as a surrogate for pleural pressure (Ppl), may allow the clinicians to discriminate between the elastic behaviour of the lung and the chest wall, and to calculate the degree of spontaneous respiratory effort. In the present review, the characteristics and limitations of airway and transpulmonary pressure monitoring will be presented; we will highlight the different assumptions underlying the various methods for measuring transpulmonary pressure (i.e., the elastance-derived and the release-derived method, and the direct measurement), as well as the potential application of transpulmonary pressure assessment during both controlled and spontaneous/assisted mechanical ventilation in critically ill patients.

Estimation of Inspiratory Respiratory Elastance Using Expiratory Data

Abstract Models of respiratory mechanics can be used to titrate patient-specific mechanical ventilation (MV) settings in critical care, but often perform poorly in the presence of patient breathing effort. Respiratory mechanics are conventionally calculated using only inspiratory data. Muscle activity is normally assumed relatively minimal or absent during passive expiration regardless of the presence of inspiratory spontaneous breathing (SB) efforts. Hence, this study assesses whether expiratory lung elastance can be used to estimate inspiratory lung elastance for spontaneously breathing, reverse triggered patients. Clinical data from recruitment manoeuvres in fully sedated patients were used to determine a relationship between inspiratory and expiratory modeled lung elastance. The validity of this relationship was assessed using data recorded pre- and post- sedation from different patients. A strong, linear relationship was found between inspiratory and expiratory elastance in fully sedated patients, with gradient 1.04 [95% CI: 1.03-1.07] and intercept 1.66 [1.06-2.08] with R2 = 0.94. After adjustment according to the linear relationship, expiratory elastance produced stable estimations post sedation, with similar median and variance as inspiratory elastance. However, variation in estimates pre-sedation, although significantly improved, may be larger than clinically acceptable in some cases. The results of this study show that the typically ignored expiratory data may be able to provide insight into patient condition when conventional methods fail. Clinically, these methods could have an impact in guiding MV therapy by providing clinicians with information about lung mechanics under the effect of patient SB effort.

Airway Pressure Release Ventilation in Pediatric Acute Respiratory Distress Syndrome. A Randomized Controlled Trial.

Although case series describe benefits of airway pressure release ventilation (APRV), this mode of ventilation has not been evaluated against the conventional low-tidal volume ventilation (LoTV) in children with acute respiratory distress syndrome (ARDS). To compare the effect of APRV and conventional LoTV on ventilator-free days in children with ARDS. This open-label, parallel-design randomized controlled trial was conducted in a 15-bed ICU. Children aged 1 month to 12 years satisfying the modified Berlin definition were included. We excluded children with air leaks, increased intracranial pressure, poor spontaneous breathing efforts, chronic lung disease, and beyond 24 hours of ARDS diagnosis or 72 hours of ventilation. Children were randomized using unstratified, variable-sized block technique. A priori interim analysis was planned at 50% enrollment. All enrolled children were followed up until 180 days after enrollment or death, whichever was earlier. The trial was terminated after 50% enrollment (52 children) when analysis revealed higher mortality in the intervention arm. Ventilator-free days were statistically similar in both arms (P = 0.23). The 28-day all-cause mortality was 53.8% in APRV as compared with 26.9% among control subjects (risk ratio, 2.0; 95% confidence interval, 0.97-4.1; Fisher exact P = 0.089). The multivariate-adjusted risk ratio of death for APRV compared with LoTV was 2.02 (95% confidence interval, 0.99-4.12; P = 0.05). Higher mean airway pressures, greater spontaneous breathing, and early improvement in oxygenation were seen in the intervention arm. APRV, as a primary ventilation strategy in children with ARDS, was associated with a trend toward higher mortality compared with the conventional LoTV. Limitations should be considered while interpreting these results. Clinical trial registered with www.clinicaltrials.gov (NCT02167698) and Clinical Trials Registry of India (CTRI/2014/06/004677).