Feasibility study on full closed-loop control ventilation (IntelliVent-ASV™) in ICU patients with acute respiratory failure: a prospective observational comparative study

Epidemiology, Ventilation Management and Outcomes of COPD Patients Receiving Invasive Ventilation for COVID-19-Insights from PRoVENT-COVID

Chronic obstructive pulmonary disease (COPD) is a risk factor for death in patients admitted to intensive care units (ICUs) for respiratory support. Previous reports suggested higher mortality in COPD patients with COVID-19. It is yet unknown whether patients with COPD were treated differently compared to non-COPD patients. We compared the ventilation management and outcomes of invasive ventilation for COVID-19 in COPD patients versus non-COPD patients. This was a post hoc analysis of a nation-wide, observational study in the Netherlands. COPD patients were compared to non-COPD patients with respect to key ventilation parameters. The secondary endpoints included adjunctive treatments for refractory hypoxemia, and 28-day mortality. Of a total of 1090 patients, 88 (8.1%) were classified as having COPD. The ventilation parameters were not different between COPD patients and non-COPD patients, except for FiO2, which was higher in COPD patients. Prone positioning was applied more often in COPD patients. COPD patients had higher 28-day mortality than non-COPD patients. COPD had an independent association with 28-day mortality. In this cohort of patients who received invasive ventilation for COVID-19, only FiO2 settings and the use of prone positioning were different between COPD patients and non-COPD patients. COPD patients had higher mortality than non-COPD patients.

Electrical impedance tomography for titration of positive end-expiratory pressure in acute respiratory distress syndrome patients with chronic obstructive pulmonary disease

Background

Chronic obstructive pulmonary disease (COPD) is one of most common comorbidities in acute respiratory distress syndrome (ARDS). There are few specific studies on the appropriate ventilation strategy for patients with ARDS comorbid with COPD, especially regarding on positive end-expiratory pressure (PEEP) titration.

Methods

To compare the respiratory mechanics in mechanical ventilated ARDS patients with or without COPD and to determine whether titration of PEEP based on electrical impedance tomography (EIT) is superior to the ARDSnet protocol. This is a single center, perspective, repeated measure study. ARDS patients requiring mechanical ventilation who were admitted to the intensive care unit between August 2017 and December 2020 were included. ARDS patients were divided according to whether they had COPD into a COPD group and a non-COPD group. Respiratory mechanics, gas exchange, and hemodynamics during ventilation were compared between the groups according to whether the PEEP level was titrated by EIT or the ARDSnet protocol.

Results

A total of twenty-seven ARDS patients including 14 comorbid with and 13 without COPD who met the study eligibility criteria were recruited. The PEEP levels titrated by EIT and the ARDSnet protocol were lower in the COPD group than in the non-COPD group (6.93 ± 1.69 cm H₂O vs. 12.15 ± 2.40 cm H₂O, P < 0.001 and 10.43 ± 1.20 cm H₂O vs. 14.0 ± 3.0 cm H₂O, P < 0.001, respectively). In the COPD group, the PEEP level titrated by EIT was lower than that titrated by the ARDSnet protocol (6.93 ± 1.69 cm H₂O vs. 10.43 ± 1.20 cm H₂O, P < 0.001), as was the global inhomogeneity (GI) index (0.397 ± 0.040 vs. 0.446 ± 0.052, P = 0.001), plateau airway pressure (16.50 ± 4.35 cm H₂O vs. 20.93 ± 5.37 cm H₂O, P = 0.001), dead space ventilation ratio (48.29 ± 6.78% vs. 55.14 ± 8.85%, P < 0.001), ventilation ratio (1.63 ± 0.33 vs. 1.87 ± 0.33, P < 0.001), and mechanical power (13.92 ± 2.18 J/min vs. 15.87 ± 2.53 J/min, P < 0.001). The cardiac index was higher when PEEP was treated by EIT than when it was titrated by the ARDSnet protocol (3.41 ± 0.50 L/min/m² vs. 3.02 ± 0.43 L/min/m², P < 0.001), as was oxygen delivery (466.40 ± 71.08 mL/min/m² vs. 411.10 ± 69.71 mL/min/m², P = 0.001).

Conclusion

Titrated PEEP levels were lower in patients with ARDS with COPD than in ARDS patients without COPD. In ARDS patient comorbid with COPD, application of PEEP titrated by EIT was lower than those titrated by the ARDSnet protocol, which contributed to improvements in the ventilation ratio, mechanical energy, cardiac index, and oxygen delivery with less of an adverse impact on hemodynamics.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-04201-y.

Efficacy of adaptive ventilation support combined with lung recruitment maneuvering for acute respiratory distress syndrome

OBJECTIVE

This study was designed to evaluate the efficacy of adaptive support ventilation (ASV) and lung recruitment maneuvering (LRM) on the hemodynamics and respiratory mechanics of patients with acute respiratory distress syndrome (ARDS).

METHODS

A total of 100 patients with ARDS admitted to the intensive care unit (ICU) of our hospital from July 2016 to October 2019 were randomly divided into the control group (n=50) receiving synchronized intermittent mandatory ventilation (SIMV) and the study group (n=50) receiving ASV + LRM. The hemodynamics, respiratory mechanics, oxygen metabolism parameters, pulmonary index of microcirculatory resistance and prognosis were compared between the two groups.

RESULTS

No significant difference was observed between the two groups in terms of baseline data (P > 0.05). Positive end-expiratory pressure (PEEP), mean arterial pressure (MAP), central venous pressure (CVP), heart rate (HR), systemic vascular resistance index (SVRI), pulmonary arterial pressure (PAP), and cardiac output index (CI) were not significantly different between the two groups (P > 0.05). PEEP, peak inspiratory pressure (PIP), pulmonary vascular resistance index (PVRI), and extravascular lung water (EVLW) were lower, and arterial oxygen pressure (PaO₂), global oxygen delivery (DO₂), oxygen-uptake (VO₂), and dynamic compliance (Cdyn) were higher in the study group than in the control group (P < 0.05). Time to withdrawal, APACHE II score, and length of stay in ICU were lower in the study group than in the control group (P < 0.05).

CONCLUSION

ASV + LRM can improve respiratory mechanics, oxygen metabolism, reduce microcirculatory resistance, shorten ICU stay and alleviate the conditions of ARDS patients, but has no significant effect on hemodynamics.

Accuracy of two pulse-oximetry measurements for INTELLiVENT-ASV in mechanically ventilated patients: a prospective observational study

Recently, maintaining a certain oxygen saturation measured by pulse oximetry (SpO₂) range in mechanically ventilated patients was recommended; attaching the INTELLiVENT-ASV to ventilators might be beneficial. We evaluated the SpO₂ measurement accuracy of a Nihon Kohden and a Masimo monitor compared to actual arterial oxygen saturation (SaO₂). SpO₂ was simultaneously measured by a Nihon Kohden and Masimo monitor in patients consecutively admitted to a general intensive care unit and mechanically ventilated. Bland–Altman plots were used to compare measured SpO₂ with actual SaO₂. One hundred mechanically ventilated patients and 1497 arterial blood gas results were reviewed. Mean SaO₂ values, Nihon Kohden SpO₂ measurements, and Masimo SpO₂ measurements were 95.7%, 96.4%, and 96.9%, respectively. The Nihon Kohden SpO₂ measurements were less biased than Masimo measurements; their precision was not significantly different. Nihon Kohden and Masimo SpO₂ measurements were not significantly different in the “SaO₂ < 94%” group (P = 0.083). In the “94% ≤ SaO₂ < 98%” and “SaO₂ ≥ 98%” groups, there were significant differences between the Nihon Kohden and Masimo SpO₂ measurements (P < 0.0001; P = 0.006; respectively). Therefore, when using automatically controlling oxygenation with INTELLiVENT-ASV in mechanically ventilated patients, the Nihon Kohden SpO₂ sensor is preferable.

Trial registration UMIN000027671. Registered 7 June 2017.

A Novel Mainstream Capnometer System for Non-invasive Positive Pressure Ventilation

Capnometry is a method to measure carbon dioxide (CO₂) in exhaled gas and it has been used to monitor patient respiratory status. CO₂ monitoring is also used for patients receiving non-invasive positive pressure ventilation (NPPV) therapy during mechanical ventilation. Ventilators actively dilute exhaled gas during non-invasive ventilation. In order to accurately measure end-tidal CO₂, an adequate amount of expired gas needs to be filled in a CO₂ measurement cell before expiratory positive airway pressure (EPAP) gas from the ventilator arrives to the cell. This is the reason why it is difficult to measure CO₂ stably during non-invasive ventilation using the conventional CO₂ measurement method. Therefore, we developed NPPV cap-ONE mask, which accurately measures CO₂ in exhaled gas during non-invasive ventilation. In this study, we evaluated the basic performance of the NPPV cap-ONE mask system. The NPPV cap-ONE mask system could accurately measure CO₂ in exhaled gas comparing to the conventional device in this study.

Proportional modes of ventilation: technology to assist physiology

Proportional modes of ventilation assist the patient by adapting to his/her effort, which contrasts with all other modes. The two proportional modes are referred to as neurally adjusted ventilatory assist (NAVA) and proportional assist ventilation with load-adjustable gain factors (PAV+): they deliver inspiratory assist in proportion to the patient’s effort, and hence directly respond to changes in ventilatory needs. Due to their working principles, NAVA and PAV+ have the ability to provide self-adjusted lung and diaphragm-protective ventilation. As these proportional modes differ from ‘classical’ modes such as pressure support ventilation (PSV), setting the inspiratory assist level is often puzzling for clinicians at the bedside as it is not based on usual parameters such as tidal volumes and PaCO₂ targets. This paper provides an in-depth overview of the working principles of NAVA and PAV+ and the physiological differences with PSV. Understanding these differences is fundamental for applying any assisted mode at the bedside. We review different methods for setting inspiratory assist during NAVA and PAV+ , and (future) indices for monitoring of patient effort. Last, differences with automated modes are mentioned.

Automated vs. conventional ventilation in the ICU: a randomized controlled crossover trial comparing blood oxygen saturation during daily nursing procedures (I-NURSING)

Background

Hypoxia is common during daily nursing procedures (DNPs) routinely performed on mechanically ventilated patients. The impact of automated ventilation on the incidence and severity of blood oxygen desaturation during DNPs remains unknown.

Methods

A prospective randomized controlled crossover trial was carried out in a French intensive care unit to compare blood oxygen pulse saturation (SpO₂) during DNPs performed on patients mechanically ventilated in automated and conventional ventilation modes (AV and CV, respectively). All patients with FiO₂ ≤ 60% and without prone positioning or neuromuscular blocking agents were included. Patients underwent two DNPs on the same day using AV (INTELLiVENT-ASV®) and CV (volume control, biphasic positive airway pressure, or pressure support ventilation) in a randomized order. The primary outcome was the percentage of time spent with SpO₂ in the acceptable range of 90–95% during the DNP.

Results

Of the 265 included patients, 93% had been admitted for a medical pathology, the majority for acute respiratory failure (52%). There was no difference between the two periods in terms of DNP duration, sedation requirements, or ventilation parameters, but patients had more spontaneous breaths and lower peak airway pressures during the AV period (p <  0.001). The percentage of time spent with SpO₂ in the acceptable range during DNPs was longer in the AV period than in the CV period (48 ± 37 vs. 43 ± 37, percentage of DNP period; p = 0.03). After adjustment, AV was associated with a higher number of DNPs carried out with SpO₂ in the acceptable range (odds ratio, 1.82; 95% CI, 1.28 to 2.6; p = 0.001) and a lower incidence of blood oxygen desaturation ≤ 85% (adjusted odds ratio, 0.50; 95% CI, 0.30 to 0.85; p = 0.01).

Conclusion

AV appears to reduce the incidence and severity of blood oxygen desaturation during daily nursing procedures (DNPs) in comparison to CV.

Trial registration

This study was registered in clinical-trial.gov (NCT03176329) in June 2017.

Graphical abstract

Predictive factors for successful INTELLiVENT-ASV® use: a retrospective observational study

Background

INTELLiVENT-ASV® (I-ASV) is a closed-loop ventilation mode that automatically controls the ventilation settings. Although a number of studies have reported the usefulness of I-ASV, the clinical situations in which it may be useful have not yet been clarified. We aimed to report our initial 3 years of experience using I-ASV, particularly the clinical conditions and the technical and organizational factors associated with its use. Furthermore, we evaluated the usefulness of I-ASV and determined the predictive factors for successful management with I-ASV.

Methods

This single-center, retrospective observational study included patients who were ventilated using the Hamilton G5® ventilator (Hamilton Medical AG, Rhäzüns, Switzerland) from January 2016 to December 2018. The patients were categorized into the “I-ASV success” group and “I-ASV failure” group (those receiving mechanical ventilation with I-ASV along with any other mode). Multivariate analysis was performed to identify factors associated with successful I-ASV management.

Results

Of the 189 patients, 135 (71.4%) were categorized into the I-ASV success group. In the I-ASV success group, the reasons for ICU admission included post-elective surgery (94.1%), post-emergent surgery (81.5%), and other medical reasons (55.6%). I-ASV failure was associated with a low P/F ratio (278 vs. 167, P = 0.0003) and high Acute Physiology and Chronic Health Evaluation (APACHE) II score (21 vs. 26, P < 0.0001). The main reasons for not using I-ASV included strong inspiratory effort and asynchrony. The APACHE II score was an independent predictive factor for successful management with I-ASV, with an odds ratio of 0.92 (95% confidential interval 0.87–0.96, P = 0.0006). The area under the receiver operating curve for the APACHE II score was 0.722 (cut-off: 24).

Conclusions

In this study, we found that 71.4% of the fully mechanically ventilated patients could be managed successfully with I-ASV. The APACHE II score was an independent factor that could help predict the successful management of I-ASV. To improve I-ASV management, it is necessary to focus on patient-ventilator interactions.

Temporal Changes in Ventilator Settings in Patients With Uninjured Lungs: A Systematic Review

In patients with uninjured lungs, increasing evidence indicates that tidal volume (VT) reduction improves outcomes in the intensive care unit (ICU) and in the operating room (OR). However, the degree to which this evidence has translated to clinical changes in ventilator settings for patients with uninjured lungs is unknown. To clarify whether ventilator settings have changed, we searched MEDLINE, Cochrane Central Register of Controlled Trials, and Web of Science for publications on invasive ventilation in ICUs or ORs, excluding those on patients <18 years of age or those with >25% of patients with acute respiratory distress syndrome (ARDS). Our primary end point was temporal change in VT over time. Secondary end points were changes in maximum airway pressure, mean airway pressure, positive end-expiratory pressure, inspiratory oxygen fraction, development of ARDS (ICU studies only), and postoperative pulmonary complications (OR studies only) determined using correlation analysis and linear regression. We identified 96 ICU and 96 OR studies comprising 130,316 patients from 1975 to 2014 and observed that in the ICU, VT size decreased annually by 0.16 mL/kg (-0.19 to -0.12 mL/kg) (P < .001), while positive end-expiratory pressure increased by an average of 0.1 mbar/y (0.02-0.17 mbar/y) (P = .017). In the OR, VT size decreased by 0.09 mL/kg per year (-0.14 to -0.04 mL/kg per year) (P < .001). The change in VTs leveled off in 1995. Other intraoperative ventilator settings did not change in the study period. Incidences of ARDS (ICU studies) and postoperative pulmonary complications (OR studies) also did not change over time. We found that, during a 39-year period, from 1975 to 2014, VTs in clinical studies on mechanical ventilation have decreased significantly in the ICU and in the OR.

Airway and transpulmonary driving pressures and mechanical powers selected by INTELLiVENT-ASV in passive, mechanically ventilated ICU patients

BACKGROUND

Driving pressure (ΔP) and mechanical power (MP) are predictors of the risk of ventilation- induced lung injuries (VILI) in mechanically ventilated patients. INTELLiVENT-ASV® is a closed-loop ventilation mode that automatically adjusts respiratory rate and tidal volume, according to the patient's respiratory mechanics.

OBJECTIVES

This prospective observational study investigated ΔP and MP (and also transpulmonary ΔP (ΔP_L) and MP (MP_L) for a subgroup of patients) delivered by INTELLiVENT-ASV.

METHODS

Adult patients admitted to the ICU were included if they were sedated and met the criteria for a single lung condition (normal lungs, COPD, or ARDS). INTELLiVENT-ASV was used with default target settings. If PEEP was above 16 cmH2O, the recruitment strategy used transpulmonary pressure as a reference, and ΔP_L and MP_L were computed. Measurements were made once for each patient.

RESULTS

Of the 255 patients included, 98 patients were classified as normal-lungs, 28 as COPD, and 129 as ARDS patients. The median ΔP was 8 (7 - 10), 10 (8 - 12), and 9 (8 - 11) cmH2O for normal-lungs, COPD, and ARDS patients, respectively. The median MP was 9.1 (4.9 - 13.5), 11.8 (8.6 - 16.5), and 8.8 (5.6 - 13.8) J/min for normal-lungs, COPD, and ARDS patients, respectively. For the 19 patients managed with transpulmonary pressure ΔP_L was 6 (4 - 7) cmH2O and MP_L was 3.6 (3.1 - 4.4) J/min.

CONCLUSIONS

In this short term observation study, INTELLiVENT-ASV selected ΔP and MP considered in safe ranges for lung protection. In a subgroup of ARDS patients, the combination of a recruitment strategy and INTELLiVENT-ASV resulted in an apparently safe ΔP_L and MP_L.

In Vitro Study of the Effect of Breathing Pattern on Aerosol Delivery During High-Flow Nasal Therapy

Introduction

The use of concurrent aerosol delivery during high-flow nasal therapy (HFNT) may be exploited to facilitate delivery of a variety of prescribed medications for inhalation. The study assessed the effect of tidal volume, breath rate, and inspiratory:expiratory (I:E) ratio on the quantity of aerosol captured at the level of the trachea during simulated HFNT.

Methods

Testing was completed according to a factorial statistical design of experiments (DOE) approach. Tracheal dose was characterized with a vibrating mesh nebulizer (Aerogen Solo, Aerogen Ltd) using simulated adult, small child, and infant HFNT models. Furthermore, aerosol delivery was evaluated across a range of adult patient profiles with clinically representative test setups.

Results

Aerosol delivery increased with a large tidal volume, a rapid breath rate, and a long inspiratory time. Tidal volume, breath rate, and I:E ratio each had a significant effect on tracheal dose across simulated adult, small child, and infant breathing.

Conclusion

The main trends that were identified in the statistical DOE predicted aerosol delivery across adult patient breathing profiles, in terms of tidal volume, breath rate, and I:E ratio. Therefore, patients with distressed breathing profiles may be expected to receive a larger aerosol dose than those with normal breathing rates.

Funding

Aerogen Limited.

Automation of Mechanical Ventilation

Closed loop control of mechanical ventilation is routine and operates behind the ventilator interface. Reducing caregiver interactions is neither an advantage for the patient or the staff. Automated systems causing lack of situational awareness of the intensive care unit are a concern. Along with autonomous systems must come monitoring and displays that display patients' current condition and response to therapy. Alert notifications for sudden escalation of therapy are required to ensure patient safety. Automated ventilation is useful in remote settings in the absence of experts. Whether automated ventilation will be accepted in large academic medical centers remains to be seen.

Advanced modes of mechanical ventilation and optimal targeting schemes

Recent research results provide new incentives to recognize and prevent ventilator-induced lung injury (VILI) and create targeting schemes for new modes of mechanical ventilation. For example, minimization of breathing power, inspiratory power, and inspiratory pressure are the underlying goals of optimum targeting schemes used in the modes called adaptive support ventilation (ASV), adaptive ventilation mode 2 (AVM2), and MID-frequency ventilation (MFV). We describe the mathematical models underlying these targeting schemes and present theoretical analyses for minimizing tidal volume, tidal pressure (also known as driving pressure), or tidal power as functions of ventilatory frequency. To go beyond theoretical equations, these targeting schemes were compared in terms of expected tidal volumes using different patient models. Results indicate that at the same ventilation efficiency (same PaCO₂ level), we expect tidal volume dosage in the range of 7.4 mL/kg (for ASV), 6.2 mL/kg (for AVM2), and 6.7 mL/kg (for MFV) for adult ARDS simulation. For a neonatal RDS model, we expect 5.5 mL/kg (for ASV), 4.6 mL/kg (for AVM2), and 4.5 (for MFV).

[Use of the IntelliVent-ASV mode for maintaining the target EtCO2 range in patients with severe TBI]

PURPOSE

the study purpose was to evaluate the efficacy of the IntelliVent-ASV mode in maintaining the target range of PaCO2 in patients with severe TBI.

MATERIAL AND METHODS

The study included 12 severe TBI patients with the wakefulness level scored 4-9 (GCS). This was a crossover design study. Two ventilation modes were consecutively used: IntelliVent-ASV and P-CMV, for 12 h each. When using the P-CMV mode, the ventilation parameters were set to maintain PaCO2 in a range of 35-38 mm Hg. The IntelliVent-ASV mode involved the Brain Injury ventilation algorithm. The target range of EtCO2 was set in accordance with the delta PaCO2-EtCO2 to maintain PaCO2 in a range of 35-38. At the beginning of each ventilation period and every 3 hours, the arterial blood gas composition was analyzed. When PaCO2 occurred out of the 35-38 range, appropriate adjustments were made to the ventilation parameters. In the P-CMV mode, the Pinsp and RR parameters were adjusted to achieve the target PaCO2 range. In IntelliVent mode, a shift of the target EtCO2 range was adjusted in accordance with a changed PaCO2-EtCO2 difference. In all patients, ICP, blood pressure, and EtCO2 were monitored; the arterial blood gas composition was analyzed every 3 h; the frequency of manual settings of ventilation parameters was recorded.

RESULTS

The EtCO2 and PaCO2 parameters were found not to be significantly different in the P-CMV and IntelliVent modes, but the spread in these parameters was significantly lower in the IntelliVent ventilation mode. The PaCO2 parameter occurred out of the target range significantly less often in the IntelliVent mode than in the P-CMV mode. The mean frequency of manual respirator settings needed to maintain the target EtCO2 range was significantly lower in the IntelliVent-ASV mode than in the P-CMV mode.

CONCLUSION

The IntelliVent-ASV mode provides more efficient maintenance of PaCO2 in the target range compared to traditional artificial ventilation using fewer manual settings of the ventilation parameters.

The Equilibration of PCO2 in Pigs Is Independent of Lung Injury and Hemodynamics

OBJECTIVES

In mechanical ventilation, normoventilation in terms of PCO2 can be achieved by titration of the respiratory rate and/or tidal volume. Although a linear relationship has been found between changes in respiratory rate and resulting changes in end-tidal cO2 (△PetCO2) as well as between changes in respiratory rate and equilibration time (teq) for mechanically ventilated patients without lung injury, it is unclear whether a similar relationship holds for acute lung injury or altered hemodynamics.

DESIGN

We performed a prospective randomized controlled animal study of the change in PetCO2 with changes in respiratory rate in a lung-healthy, lung-injury, lung-healthy + altered hemodynamics, and lung-injury + altered hemodynamics pig model.

SETTING

University research laboratory.

SUBJECTS

Twenty mechanically ventilated pigs.

INTERVENTIONS

Moderate lung injury was induced by injection of oleic acid in 10 randomly assigned pigs, and after the first round of measurements, cardiac output was increased by approximately 30% by constant administration of noradrenalin in both groups.

MEASUREMENTS AND MAIN RESULTS

We systematically increased and decreased changes in respiratory rate according to a set protocol: +2, -4, +6, -8, +10, -12, +14 breaths/min and awaited equilibration of Petco2. We found a linear relationship between changes in respiratory rate and △PetCO2 as well as between changes in respiratory rate and teq. A two-sample t test resulted in no significant differences between the lung injury and healthy control group before or after hemodynamic intervention. Furthermore, exponential extrapolation allowed prediction of the new PetCO2 equilibrium and teq after 5.7 ± 5.6 min.

CONCLUSIONS

The transition between PetCO2 equilibria after changes in respiratory rate might not be dependent on moderate lung injury or cardiac output but on the metabolic production or capacity of cO2 stores. Linear relationships previously found for lung-healthy patients and early prediction of PetCO2 equilibration could therefore also be used for the titration of respiratory rate on the PetCO2 for a wider range of pathologies by the physician or an automated ventilation system.

Automated Weaning from Mechanical Ventilation after Off-Pump Coronary Artery Bypass Grafting

BACKGROUND

The discontinuation of mechanical ventilation after coronary surgery may prolong and significantly increase the load on intensive care unit personnel. We hypothesized that automated mode using INTELLiVENT-ASV can decrease duration of postoperative mechanical ventilation, reduce workload on medical staff, and provide safe ventilation after off-pump coronary artery bypass grafting (OPCAB). The primary endpoint of our study was to assess the duration of postoperative mechanical ventilation during different modes of weaning from respiratory support (RS) after OPCAB. The secondary endpoint was to assess safety of the automated weaning mode and the number of manual interventions to the ventilator settings during the weaning process in comparison with the protocolized weaning mode.

MATERIALS AND METHODS

Forty adult patients undergoing elective OPCAB were enrolled into a prospective single-center study. Patients were randomized into two groups: automated weaning (n = 20) using INTELLiVENT-ASV mode with quick-wean option; and protocolized weaning (n = 20), using conventional synchronized intermittent mandatory ventilation (SIMV) + pressure support (PS) mode. We assessed the duration of postoperative ventilation, incidence and duration of unacceptable RS, and the load on medical staff. We also performed the retrospective analysis of 102 patients (standard weaning) who were weaned from ventilator with SIMV + PS mode based on physician's experience without prearranged algorithm.

RESULTS AND DISCUSSION

Realization of the automated weaning protocol required change in respiratory settings in 2 patients vs. 7 (5-9) adjustments per patient in the protocolized weaning group. Both incidence and duration of unacceptable RS were reduced significantly by means of the automated weaning approach. The FiO₂ during spontaneous breathing trials was significantly lower in the automated weaning group: 30 (30-35) vs. 40 (40-45) % in the protocolized weaning group (p < 0.01). The average time until tracheal extubation did not differ in the automated weaning and the protocolized weaning groups: 193 (115-309) and 197 (158-253) min, respectively, but increased to 290 (210-411) min in the standard weaning group.

CONCLUSION

The automated weaning system after off-pump coronary surgery might provide postoperative ventilation in a more protective way, reduces the workload on medical staff, and does not prolong the duration of weaning from ventilator. The use of automated or protocolized weaning can reduce the duration of postoperative mechanical ventilation in comparison with non-protocolized weaning based on the physician's decision.

Physiological closed-loop control of mechanical ventilation and extracorporeal membrane oxygenation

A new concept is presented for cooperative automation of mechanical ventilation and extracorporeal membrane oxygenation (ECMO) therapy for treatment of acute respiratory distress syndrome (ARDS). While mechanical ventilation is continuously optimized to promote lung protection, extracorporeal gas transfer rates are simultaneously adjusted to control oxygen supply and carbon dioxide removal using a robust patient-in-the-loop control system. In addition, the cooperative therapy management uses higher-level algorithms to adjust both therapeutic approaches. The controller synthesis is derived based on the introduced objectives, the experimental setup and the uncertain models. Finally, the autonomous ARDS therapy system capabilities are demonstrated and discussed based on

Mechanical Ventilation during Extracorporeal Membrane Oxygenation in Patients with Acute Severe Respiratory Failure

Conventionally, a substantial number of patients with acute respiratory failure require mechanical ventilation (MV) to avert catastrophe of hypoxemia and hypercapnia. However, mechanical ventilation per se can cause lung injury, accelerating the disease progression. Extracorporeal membrane oxygenation (ECMO) provides an alternative to rescue patients with severe respiratory failure that conventional mechanical ventilation fails to maintain adequate gas exchange. The physiology behind ECMO and its interaction with MV were reviewed. Next, we discussed the timing of ECMO initiation based on the risks and benefits of ECMO. During the running of ECMO, the protective ventilation strategy can be employed without worrying about catastrophic hypoxemia and carbon dioxide retention. There is a large body of evidence showing that protective ventilation with low tidal volume, high positive end-expiratory pressure, and prone positioning can provide benefits on mortality outcome. More recently, there is an increasing popularity on the use of awake and spontaneous breathing for patients undergoing ECMO, which is thought to be beneficial in terms of rehabilitation.

Glucose Control in the ICU: A Continuing Story

In the present era of near-continuous glucose monitoring (CGM) and automated therapeutic closed-loop systems, measures of accuracy and of quality of glucose control need to be standardized for licensing authorities and to enable comparisons across studies and devices. Adequately powered, good quality, randomized, controlled studies are needed to assess the impact of different CGM devices on the quality of glucose control, workload, and costs. The additional effects of continuing glucose control on the general floor after the ICU stay also need to be investigated. Current algorithms need to be adapted and validated for CGM, including effects on glucose variability and workload. Improved collaboration within the industry needs to be encouraged because no single company produces all the necessary components for an automated closed-loop system. Combining glucose measurement with measurement of other variables in 1 sensor may help make this approach more financially viable.

Automated weaning from mechanical ventilation

Mechanical ventilation (MV) is one of the lifesaving techniques applied to critically ill patients at bedside. However, some complications, such as ventilator-induced lung injury and ventilator-associated pneumonia, may occur in a patient undertaking MV and are often related to the duration of MV. Some written protocols have been proposed to reduce the risk of such complications, but they can be time consuming, leading to fluctuation in protocol implementation and compliance. Moreover, written instructions tend to be general and thus cannot cover all possible scenarios, resulting in variable interpretation of the protocol. To overcome these limiting factors, protocols have been computerized and there is convincing evidence in the literature showing that computerized protocols benefit management of the process and reduce the time a patient spends under MV. QuickWean is a computer-aided weaning protocol implemented on the Hamilton S1 ventilator (Hamilton Medical AG, Bonaduz, Switzerland), which guides the patient through the weaning process without requiring any intervention by the treating physician. The fully-automated ventilation mode is INTELLiVENT^®-ASV (Hamilton Medical AG), which is set according to the patient’s respiratory mechanics, patient-ventilator interaction, peripheral oxygen saturation (SpO₂) and pulmonary end-tidal carbon dioxide (PetCO₂). The INTELLiVENT^®-ASV mode sets automatically each minute to provide accurate ventilation, pressure support, fraction of inspired oxygen and positive end-expiratory pressure based on the patient’s needs. QuickWean can be pre-set to match the established weaning policy of an intensive care unit as well as being customized to a patient’s needs. It provides a progressive reduction of respiratory support, and guides the patient through the spontaneous breathing trial (SBT). At the end of the SBT, the ventilator re-starts the previous ventilation support and provides a report of the successful SBT. During all phases, PetCO₂, SpO₂ and all breathing parameters are monitored. This new automated weaning tool may improve the safety and effectiveness of an SBT, reducing the time spent in the process of weaning and providing a lower workload for the treating physician.

Tidal volume measurement error in pressure control modes of mechanical ventilation: A model study

Tidal volume (VT) measurement during pressure control (PC) ventilation with preset inspiratory time may produce errors due to patient inspiratory effort. We evaluated VT error in 3 common ICU ventilators.

METHODS

Simulated patient: 60kg adult with ARDS using IngMar Medical ASL 5000 having moderate inspiratory effort. Ventilators evaluated: Covidien PB 840, Maquet Servo-i, and Dräger Evita XL, PC breaths at preset inspiratory time (TI) 0.6-1.4s. VT error was defined as ventilator displayed VT minus the simulator displayed VT (mL/kg or % of true).

RESULTS

Relaxation of inspiratory effort caused flow reversal (exhalation) during TI, which led to VT error. For the PB 840, VT error was proportional to TI (maximum -2.0mL/kg, -19%). For the Servo-i, VT error was not related to TI (maximum error -0.2mL/kg or -1.2%). Volume error for Evita XL was not related to TI (maximum error was -0.7mL/kg or -6%).

CONCLUSIONS

Calculation of VT as the integral of flow over the preset inspiratory time rather than the period between zero crossings of flow may result in underestimation of both inhaled and exhaled volumes. The size of VT error can be large enough to potentially affect patient outcomes on some ventilators.

Approaches to ventilation in intensive care

BACKGROUND

Mechanical ventilation is a common and often life-saving intervention in intensive care medicine. About 35% of all patients in intensive care are mechanically ventilated; about 15% of these patients develop a ventilation-associated pneumonia. The goal of ventilation therapy is to lessen the work of respiration and pulmonary gas exchange and thereby maintain or restore an adequate oxygen supply to the body's tissues. Mechanical ventilation can be carried out in many different modes; the avoidance of ventilation-induced lung damage through protective ventilation strategies is currently a major focus of clinical interest.

METHOD

This review is based on pertinent articles retrieved by a selective literature search.

RESULTS

Compared to conventional lung-protecting modes of mechanical ventilation, the modern modes of ventilation presented here are further developments that optimize lung protection while improving pulmonary function and the synchrony of the patient with the ventilator. In high-frequency ventilation, tidal volumes of 1-2 mL/kgBW (body weight) are given, at a respiratory rate of up to 12 Hz. Assisted forms of spontaneous respiration are also in use, such as proportional assist ventilation (PAV), neurally adjusted ventilatory assist (NAVA), and variable pressure-support ventilation. Computer-guided closed-loop ventilation systems enable automated ventilation; according to a recent meta-analysis, they shorten weaning times by 32% .

CONCLUSION

The currently available scientific evidence with respect to clinically relevant endpoints is inadequate for all of these newer modes of ventilation. It appears, however, that they can lower both the invasiveness and the duration of mechanical ventilation, and thus improve the care of patients who need ventilation. Randomized trials with clinically relevant endpoints must be carried out before any final judgments can be made.

Portable mechanical ventilation with closed-loop control of inspired fraction of oxygen maintains oxygenation in the setting of hemorrhage and lung injury

BACKGROUND

Closed-loop controllers (CLCs) embedded within portable mechanical ventilators may allow for autonomous weaning. The ability of CLCs to maintain adequate oxygenation in the setting of hemorrhage and lung injury is unknown. We hypothesized that a portable ventilator with a CLC for inspired fraction of oxygen (FIO2) could provide oxygenation in a porcine model of hemorrhage and lung injury.

METHODS

Female pigs randomized to the study group (n = 6) underwent a pressure-controlled bleed (mean arterial pressure = 40 mm Hg for 30 minutes). Acute lung injury was induced by saline lung lavage followed by intentional infliction of barotrauma. Sham pigs (n = 6) underwent placement of monitoring devices without hemorrhage or lung injury. All pigs were then placed on a portable ventilator modified with a CLC algorithm, which uses feedback from pulse oximetry (SpO2) and FIO2 trends to adjust FIO2 and maintain a target SpO2 of 94% (2%). The initial FIO2 was set at 0.60. Tidal volume, positive end-expiratory pressure, rate, and inspiratory-to-expiratory ratio were constant unless changes were required clinically.

RESULTS

Study pigs had lower mean arterial pressures than shams at all time points except baseline. PaO2/FIO2 ratios were less than 300 and significantly lower than both baseline values and corresponding sham values at all time points. The CLC weaned the FIO2 at a reduced rate in study pigs relative to shams with a final mean FIO2 of 0.54 and 0.29 in study and sham pigs, respectively (p < 0.05). There was a significant divergence in the study and sham FIO2 curves but no significant difference in oxygen saturation or hypoxemia.

CONCLUSION

Adequate oxygenation can be maintained in the setting of hemorrhage and lung injury using a portable ventilator embedded with a CLC of FIO2 based on pulse oximetry. These devices may be valuable for providing advanced medical care in resource-limited environments.

Automatic protective ventilation using the ARDSNet protocol with the additional monitoring of electrical impedance tomography

INTRODUCTION

Automatic ventilation for patients with respiratory failure aims at reducing mortality and can minimize the workload of clinical staff, offer standardized continuous care, and ultimately save the overall cost of therapy. We therefore developed a prototype for closed-loop ventilation using acute respiratory distress syndrome network (ARDSNet) protocol, called autoARDSNet.

METHODS

A protocol-driven ventilation using goal-oriented structural programming was implemented and used for 4 hours in seven pigs with lavage-induced acute respiratory distress syndrome (ARDS). Oxygenation, plateau pressure and pH goals were controlled during the automatic ventilation therapy using autoARDSNet. Monitoring included standard respiratory, arterial blood gas analysis and electrical impedance tomography (EIT) images. After 2-hour automatic ventilation, a disconnection of the animal from the ventilator was carried out for 10 seconds, simulating a frequent clinical scenario for routine clinical care or intra-hospital transport.

RESULTS

This pilot study of seven pigs showed stable and robust response for oxygenation, plateau pressure and pH value using the automated system. A 10-second disconnection at the patient-ventilator interface caused impaired oxygenation and severe acidosis. However, the automated protocol-driven ventilation was able to solve these problems. Additionally, regional ventilation was monitored by EIT for the evaluation of ventilation in real-time at bedside with one prominent case of pneumothorax.

CONCLUSIONS

We implemented an automatic ventilation therapy using ARDSNet protocol with seven pigs. All positive outcomes were obtained by the closed-loop ventilation therapy, which can offer a continuous standard protocol-driven algorithm to ARDS subjects.