Ineffective Triggering Research Articles

Measurement of intrinsic positive end-expiratory pressure and clinical outcomes of infants with severe bronchopulmonary dysplasia

To investigate the levels of intrinsic positive end-expiratory pressure (PEEPi) in infants with severe bronchopulmonary dysplasia (sBPD) and the relationship between different levels of PEEPi and clinical outcomes. A retrospective analysis was conducted on the clinical data of 12 sBPD infants who underwent PEEPi measurement and were hospitalized at Guangzhou Women and Children's Medical Center from January 2022 to June 2023. The clinical manifestations and outcomes at discharge were compared between infants with very high PEEPi (≥10 cmH2O) and those with lower PEEPi (<10 cmH2O). PEEPi measurements were taken in 12 sBPD infants between gestational age 31+3 and 67+2 weeks postmenstrual age, with the lowest PEEPi measured at 0.9 cmH2O and the highest at 19.6 cmH2O; 50% (6/12) of the infants had PEEPi ≥10 cmH2O. All infants with very high PEEPi exhibited ineffective triggering and patient-ventilator asynchrony. Among them, 5 infants could not be weaned off invasive ventilation, resulting in 4 deaths and 1 infant being discharged with a tracheostomy and ventilator support. In contrast, among the infants with PEEPi <10 cmH2O, only 1 infant died, while the others were successfully extubated and discharged. Infants with sBPD may have elevated PEEPi levels, and very high PEEPi may be associated with adverse outcomes in these patients.

Establishment and Application of a Patient-Ventilator Asynchrony Remote Network Platform for ICU Mechanical Ventilation: A Retrospective Study

In the process of mechanical ventilation, the problem of patient-ventilator asynchrony (PVA) is faced. This study proposes a self-developed remote mechanical ventilation visualization network system to solve the PVA problem. The algorithm model proposed in this study builds a remote network platform and achieves good results in the identification of ineffective triggering and double triggering abnormalities in mechanical ventilation. The algorithm has a sensitivity recognition rate of 79.89% and a specificity of 94.37%. The sensitivity recognition rate of the trigger anomaly algorithm was as high as 67.17%, and the specificity was 99.92%. The asynchrony index was defined to monitor the patient's PVA. The system analyzes real-time transmission of respiratory data, identifies double triggering, ineffective triggering, and other anomalies through the constructed algorithm model, and outputs abnormal alarms, data analysis reports, and data visualizations to assist or guide physicians in handling abnormalities, which is expected to improve patients' breathing conditions and prognosis.

Patient-Ventilator Asynchrony: The Power Struggle

Patient ventilator asynchrony (PVA) is a prevalent phenomenon seen in almost 25% of our intensive care unit patients. PVA can be trigger asynchrony, flow asynchrony, cycle asynchrony or mode asynchrony. Ineffective triggering is the most commonly occurring asynchrony. The best way to identify PVA is via the ventilator graphics. Corrective steps and manipulating the ventilator on the conventional mode to suit the patient's needs can help reduce the incidence of PVA. Recent advances have given rise to newer modes of ventilation such as Neurally Adjusted Ventilatory Assist and Proportional Assist Ventilation with the goal of reducing the frequency of PVA. Many new methods to reduce asynchronies are being studied; however additional large scale trials are needed to come to conclusive results. This article is an attempt to simplify the various asynchronies for better application to all healthcare professionals.

P019 Automatic Detection of Patient-Ventilator Asynchrony during Non-Invasive Ventilation using Matrix Profiles

Abstract Automated Patient-Ventilator Asynchrony (PVA) detection and classification has been described previously, however most approaches target specific asynchrony types, are not applicable in non-invasive ventilation, and require manual pre-processing, removing the opportunity for real-time analysis. During our previous study of polysomnography-assisted NIV implementation (Hannan 2019), each participants’ sleep studies were manually, breath-by-breath scored for PVA. The data were collected over approximately 8 hours and included &amp;gt; 650,000 breath cycles. The source data for the machine learning consisted of the 21 recorded signal traces exported as text files. We employed an outlier detection approach to detect asynchrony with Artificial Intelligence (AI) models as the core engine. The fully automated approach starts with pre-processing to filter and de-noise the polysomnography data, with AI models, including Multidimensional Matrix Profiles, employed to find asynchronies from a signal subset. We initially investigated the best features for PVA and arousal detection in a subset of the 59 participant sleep studies with the highest number of labelled asynchronies and arousals. These six participants had a total of 6,942 events: 799 Arousal, 3,026 Ineffective Triggering, 1,983 Double Triggering and 1,134 Auto Triggering. All events were used in the training/testing stage. The best-balanced model employed a denoising technique with 300 milliseconds as the aggregating data points interval across: mask pressure, ventilator measured flow, abdominal, and thoracic band traces. This approach resulted in 0.80 for both sensitivity and specificity.

Refractory ineffective triggering during pressure support ventilation: effect of proportional assist ventilation with load-adjustable gain factors

BackgroundIneffective triggering is frequent during pressure support ventilation (PSV) and may persist despite ventilator adjustment, leading to refractory asynchrony. We aimed to assess the effect of proportional assist ventilation with load-adjustable gain factors (PAV+) on the occurrence of refractory ineffective triggering.DesignObservational assessment followed by prospective cross-over physiological study.SettingAcademic medical ICU.PatientsIneffective triggering was detected during PSV by a twice-daily inspection of the ventilator’s screen. The impact of pressure support level (PSL) adjustments on the occurrence of asynchrony was recorded. Patients experiencing refractory ineffective triggering, defined as persisting asynchrony at the lowest tolerated PSL, were included in the physiological study.InterventionsPhysiological study: Flow, airway, and esophageal pressures were continuously recorded during 10 min under PSV with the lowest tolerated PSL, and then under PAV+ with the gain adjusted to target a muscle pressure between 5 and 10 cmH2O.MeasurementsPrimary endpoint was the comparison of asynchrony index between PSV and PAV+ after PSL and gain adjustments.ResultsAmong 36 patients identified having ineffective triggering under PSV, 21 (58%) exhibited refractory ineffective triggering. The lowest tolerated PSL was higher in patients with refractory asynchrony as compared to patients with non-refractory ineffective triggering. Twelve out of the 21 patients with refractory ineffective triggering were included in the physiological study. The median lowest tolerated PSL was 17 cmH2O [12–18] with a PEEP of 7 cmH2O [5–8] and FiO2 of 40% [39–42]. The median gain during PAV+ was 73% [65–80]. The asynchrony index was significantly lower during PAV+ than PSV (2.7% [1.0–5.4] vs. 22.7% [10.3–40.1], p < 0.001) and consistently decreased in every patient with PAV+. Esophageal pressure–time product (PTPes) did not significantly differ between the two modes (107 cmH2O/s/min [79–131] under PSV vs. 149 cmH2O/s/min [129–170] under PAV+, p = 0.092), but the proportion of PTPes lost in ineffective triggering was significantly lower with PAV+ (2 cmH2O/s/min [1–6] vs. 8 cmH2O/s/min [3–30], p = 0.012).ConclusionsAmong patients with ineffective triggering under PSV, PSL adjustment failed to eliminate asynchrony in 58% of them (21 of 36 patients). In these patients with refractory ineffective triggering, switching from PSV to PAV+ significantly reduced or even suppressed the incidence of asynchrony.

Accuracy of Algorithms and Visual Inspection for Detection of Trigger Asynchrony in Critical Patients : A Systematic Review.

Objective This study aimed to summarize the accuracy of the different methods for detecting trigger asynchrony at the bedside in mechanically ventilated patients. Method A systematic review was conducted from 1990 to 2020 in PubMed, Lilacs, Scopus, and ScienceDirect databases. The reference list of the identified studies, reviews, and meta-analyses was also manually searched for relevant studies. The reference standards were esophageal pressure catheter and/or electrical activity of the diaphragm. Studies were assessed following the QUADAS-2 recommendations, while the review was prepared according to the PRISMA criteria. Results One thousand one hundred and eleven studies were selected, and four were eligible for analysis. Esophageal pressure was the predominant reference standard, while visual inspection and algorithms/software comprised index tests. The trigger asynchrony, ineffective expiratory effort, double triggering, and reverse triggering were analyzed. Sensitivity and specificity ranged from 65.2% to 99% and 80% to 100%, respectively. Positive predictive values reached 80.3 to 100%, while the negative predictive values reached 92 to 100%. Accuracy could not be calculated for most studies. Conclusion Algorithms/software validated directly or indirectly using reference standards present high sensitivity and specificity, with a diagnostic power similar to visual inspection of experts.

Patient\u2013ventilator asynchrony, impact on clinical outcomes and effectiveness of interventions: a systematic review and meta-analysis

BackgroundPatient–ventilator asynchrony (PVA) is a common problem in patients undergoing invasive mechanical ventilation (MV) in the intensive care unit (ICU), and may accelerate lung injury and diaphragm mis-contraction. The impact of PVA on clinical outcomes has not been systematically evaluated. Effective interventions (except for closed-loop ventilation) for reducing PVA are not well established.MethodsWe performed a systematic review and meta-analysis to investigate the impact of PVA on clinical outcomes in patients undergoing MV (Part A) and the effectiveness of interventions for patients undergoing MV except for closed-loop ventilation (Part B). We searched the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, ClinicalTrials.gov, and WHO-ICTRP until August 2020. In Part A, we defined asynchrony index (AI) ≥ 10 or ineffective triggering index (ITI) ≥ 10 as high PVA. We compared patients having high PVA with those having low PVA.ResultsEight studies in Part A and eight trials in Part B fulfilled the eligibility criteria. In Part A, five studies were related to the AI and three studies were related to the ITI. High PVA may be associated with longer duration of mechanical ventilation (mean difference, 5.16 days; 95% confidence interval [CI], 2.38 to 7.94; n = 8; certainty of evidence [CoE], low), higher ICU mortality (odds ratio [OR], 2.73; 95% CI 1.76 to 4.24; n = 6; CoE, low), and higher hospital mortality (OR, 1.94; 95% CI 1.14 to 3.30; n = 5; CoE, low). In Part B, interventions involving MV mode, tidal volume, and pressure-support level were associated with reduced PVA. Sedation protocol, sedation depth, and sedation with dexmedetomidine rather than propofol were also associated with reduced PVA.ConclusionsPVA may be associated with longer MV duration, higher ICU mortality, and higher hospital mortality. Physicians may consider monitoring PVA and adjusting ventilator settings and sedatives to reduce PVA. Further studies with adjustment for confounding factors are warranted to determine the impact of PVA on clinical outcomes.Trial registration protocols.io (URL: https://www.protocols.io/view/the-impact-of-patient-ventilator-asynchrony-in-adu-bsqtndwn, 08/27/2020).

Patient-ventilator dyssynchrony in the intensive care unit: A practical approach to diagnosis and management.

Patient-ventilator dyssynchrony or asynchrony occurs when, for any parameter of respiration, discordance exists between the patient's spontaneous effort and the ventilator's provided support. If not recognised, it may promote oversedation, prolong the duration of mechanical ventilation, create risk for lung injury, and generally confuse the clinical picture. Seven forms of dyssynchrony are common: (a) ineffective triggering; (b) autotriggering; (c) inadequate flow; (d) too much flow; (e) premature cycling; (f) delayed cycling; and (g) peak pressure apnoea. 'Reverse triggering' also occurs and may mimic premature cycling. Correct diagnosis of these phenomena often permits management by simple ventilator optimisation rather than by less desirable measures.

Neural control of pressure support ventilation improved patient-ventilator synchrony in patients with different respiratory system mechanical properties: a prospective, crossover trial.

BackgroundConventional pressure support ventilation (PSP) is triggered and cycled off by pneumatic signals such as flow. Patient-ventilator asynchrony is common during pressure support ventilation, thereby contributing to an increased inspiratory effort. Using diaphragm electrical activity, neurally controlled pressure support (PSN) could hypothetically eliminate the asynchrony and reduce inspiratory effort. The purpose of this study was to compare the differences between PSN and PSP in terms of patient-ventilator synchrony, inspiratory effort, and breathing pattern.MethodsEight post-operative patients without respiratory system comorbidity, eight patients with acute respiratory distress syndrome (ARDS) and obvious restrictive acute respiratory failure (ARF), and eight patients with chronic obstructive pulmonary disease (COPD) and mixed restrictive and obstructive ARF were enrolled. Patient-ventilator interactions were analyzed with macro asynchronies (ineffective, double, and auto triggering), micro asynchronies (inspiratory trigger delay, premature, and late cycling), and the total asynchrony index (AI). Inspiratory efforts for triggering and total inspiration were analyzed.ResultsTotal AI of PSN was consistently lower than that of PSP in COPD (3% vs. 93%, P = 0.012 for 100% support level; 8% vs. 104%, P = 0.012 for 150% support level), ARDS (8% vs. 29%, P = 0.012 for 100% support level; 16% vs. 41%, P = 0.017 for 150% support level), and post-operative patients (21% vs. 35%, P = 0.012 for 100% support level; 15% vs. 50%, P = 0.017 for 150% support level). Improved support levels from 100% to 150% statistically increased total AI during PSP but not during PSN in patients with COPD or ARDS. Patients’ inspiratory efforts for triggering and total inspiration were significantly lower during PSN than during PSP in patients with COPD or ARDS under both support levels (P < 0.05). There was no difference in breathing patterns between PSN and PSP.ConclusionsPSN improves patient-ventilator synchrony and generates a respiratory pattern similar to PSP independently of any level of support in patients with different respiratory system mechanical properties. PSN, which reduces the trigger and total patient's inspiratory effort in patients with COPD or ARDS, might be an alternative mode for PSP.Trial RegistrationClinicalTrials.gov, NCT01979627; https://clinicaltrials.gov/ct2/show/record/NCT01979627.

Patient\u2013ventilator asynchrony in acute brain-injured patients: a prospective observational study

BackgroundPatient–ventilator asynchrony is common in mechanically ventilated patients and may be related to adverse outcomes. Few studies have reported the occurrence of asynchrony in brain-injured patients. We aimed to investigate the prevalence, type and severity of patient–ventilator asynchrony in mechanically ventilated patients with brain injury.MethodsThis prospective observational study enrolled acute brain-injured patients undergoing mechanical ventilation. Esophageal pressure monitoring was established after enrollment. Flow, airway pressure, and esophageal pressure–time waveforms were recorded for a 15-min interval, four times daily for 3 days, for visually detecting asynchrony by offline analysis. At the end of each dataset recording, the respiratory drive was determined by the airway occlusion maneuver. The asynchrony index was calculated to represent the severity. The relationship between the prevalence and the severity of asynchrony with ventilatory modes and settings, respiratory drive, and analgesia and sedation were determined. Association of severe patient–ventilator asynchrony, which was defined as an asynchrony index ≥ 10%, with clinical outcomes was analyzed.ResultsIn 100 enrolled patients, a total of 1076 15-min waveform datasets covering 330,292 breaths were collected, in which 70,156 (38%) asynchronous breaths were detected. Asynchrony occurred in 96% of patients with the median (interquartile range) asynchrony index of 12.4% (4.3%–26.4%). The most prevalent type was ineffective triggering. No significant difference was found in either prevalence or asynchrony index among different classifications of brain injury (p > 0.05). The prevalence of asynchrony was significantly lower during pressure control/assist ventilation than during other ventilatory modes (p < 0.05). Compared to the datasets without asynchrony, the airway occlusion pressure was significantly lower in datasets with ineffective triggering (p < 0.001). The asynchrony index was significantly higher during the combined use of opioids and sedatives (p < 0.001). Significantly longer duration of ventilation and hospital length of stay after the inclusion were found in patients with severe ineffective triggering (p < 0.05).ConclusionsPatient–ventilator asynchrony is common in brain-injured patients. The most prevalent type is ineffective triggering and its severity is likely related to a long duration of ventilation and hospital stay. Prevalence and severity of asynchrony are associated with ventilatory modes, respiratory drive and analgesia/sedation strategy, suggesting treatment adjustment in this particular population.Trial registration The study has been registered on 4 July 2017 in ClinicalTrials.gov (NCT03212482) (https://clinicaltrials.gov/ct2/show/NCT03212482).

Impact of Early Passive Exercise With Cycle Ergometer on Ventilator Interaction.

Early exercise has been recommended in critically ill patients, but its impact on subject-ventilator interaction is still unclear. Therefore, the aim of this study was to evaluate the occurrence of subject-ventilator asynchrony during passive exercise in mechanically ventilated subjects. This study included deeply sedated subjects who were under mechanical ventilation for < 72 h. Subjects were coupled to a cycle ergometer and maintained at rest for 5 min (baseline period). After this period, they started 20 min of passive exercise, followed by 10 min of rest (recovery period). The occurrence of asynchrony was monitored by the analysis of flow and airway pressure waveforms, registered throughout the protocol during the baseline, exercise, and recovery periods. Hemodynamic and respiratory parameters were registered at the end of each period. Finally, arterial blood gas analysis was performed twice, at the end of the baseline period and at the end of the recovery period. 8 subjects were enrolled (63.3 ± 16.7 y old, 50% male). The asynchrony index increased during exercise (median 32.1% [interquartile range (IQR) 18.6-47.6%]), compared to baseline (median 6.6% [IQR 3.9-10.4%]), returning to initial levels during the recovery period (median 2.7% [IQR 0-12.2%]). The most frequent types of asynchrony were ineffective triggering (index of 11.8% [IQR 1.2-22.5%] during exercise, compared to 2.0% [IQR 1.4-4.4%] at baseline), and insufficient flow (index of 11.7% [IQR 4.7-19.3%] during exercise, compared to 2.0% [IQR 1.1 to 3.3%] at baseline). There were no significant changes in the hemodynamic and respiratory variables. Early cycle ergometer passive exercise in deeply sedated subjects can worsen subject-ventilator interaction, due to ineffective triggering and insufficient flow. Adjustments in the ventilatory parameters may be necessary to avoid asynchrony during exercise.

Patient-Ventilator Asynchrony in Critical Care Settings: National Outcomes of Ventilator Waveform Analysis

BackgroundPatient–ventilator asynchrony (PVA) is a prevalent and often underrecognized problem in mechanically ventilated patients. Ventilator waveform analysis is a noninvasive and reliable means of detecting PVAs, but the use of this tool has not been broadly studied. MethodsOur observational analysis leveraged a validated evaluation tool to assess the ability of critical care practitioners (CCPs) to detect different PVA types as presented in three videos. This tool consisted of three videos of common PVAs (i.e., double-triggering, auto-triggering, and ineffective triggering). Data were collected via an evaluation sheet distributed to 39 hospitals among the various CCPs, including respiratory therapists (RTs), nurses, and physicians. ResultsA total of 411 CCPs were assessed; of these, only 41 (10.2%) correctly identified the three PVA types, while 92 (22.4%) correctly detected two types and 174 (42.3%) correctly detected one; 25.3% did not recognize any PVA. There were statistically significant differences between trained and untrained CCPs in terms of recognition (three PVAs, p < 0.001; two PVAs, p = 0.001). The majority of CCPs who identified one or zero PVAs were untrained, and such differences among groups were statistically significant (one PVA, p = 0.001; zero PVAs, p = 0.004). Female gender and prior training on ventilator waveforms were found to increase the odds of identifying more than two PVAs correctly, with odds ratios (ORs) (95% confidence intervals [CIs]) of 1.93 (1.07–3.49) and 5.41 (3.26–8.98), respectively. Profession, experience, and hospital characteristics were not found to correlate with increased odds of detecting PVAs; this association generally held after applying a regression model on the RT profession, with the ORs (95% CIs) of prior training (2.89 [1.28–6.51]) and female gender (2.49 [1.15–5.39]) showing the increased odds of detecting two or more PVAs. ConclusionCommon PVAs detection were found low in critical care settings, with about 25% of PVA going undetected by CCPs. Female gender and prior training on ventilator graphics were the only significant predictive factors among CCPs and RTs in correctly identifying PVAs. There is an urgent need to establish teaching and training programs, policies, and guidelines vis-à-vis the early detection and management of PVAs in mechanically ventilated patients, so as to improve their outcomes.

Validation of an automated system for detecting ineffective triggering asynchronies during mechanical ventilation: a retrospective study.

We compare thesensitivity and specificity of clinician visual waveform analysis against an automated system's waveform analysis in detecting ineffective triggering in mechanically ventilated intensive care unit patients when compared against a reference label set based upon analysis ofrespiratory muscle activity. Electrical activity of the diaphragm or esophageal/transdiaphragmatic pressure waveforms were available to a single clinician for the generation of a reference label set indicating the ground truth, that is, presence or absence of ineffective triggering, on a breath-by-breath basis. Pressure and flow versus time tracings were made available to (i) a group of three clinicians; and (ii) the automated Syncron-E™ system capable of detecting patient-ventilator asynchrony in real-time, in order to obtain breath-by-breath labels indicatingthe presence or absence of ineffective triggering. The clinicians and the automated system did not have access to other waveforms such as electrical activity of the diaphragm or esophageal/transdiaphragmatic pressure. In total, 926 breaths were analyzed across the seven patients. Specificity for clinicians and the automated system were high (99.3% for clinician and 98.5% for the automated system). The automated system had a significantly higher sensitivity (83.2%) compared to clinicians (41.1%). Ineffective triggering detected by the automated system, which has access onlyto airway pressure and flow versus time tracings, is in substantial agreement with a reference detection derived from analysis of invasively measured patient effort waveforms.

Reason analysis of ineffective triggering caused by a continuous nebulization airflow in mechanical ventilation

To analyze the ineffective triggering caused by nebulization in the way of respiratory mechanics. A test-lung and an oxygen-driven jet nebulizer were connected to the circuit in a PB840 ventilator. The test-lung was pulled outwards in manual way till an inspiration was effectively triggered separately in different flow-trigger modes [flow-trigger sensitivity (VTrig) 3 L/min and 5 L/min] and pressure-trigger modes [pressure-trigger sensitivity (PTrig) 2 cmH2O and 4 cmH2O, 1 cmH2O = 0.098 kPa] with the nebulizer being closed and opened in turn. The corresponding relationship and characteristics between the flow and pressure in the circuit under different triggering conditions were observed by adjusting the curve amplitude in the screen. The minimum alveolar pressure (Pa) which could cause an effective triggering and the variation span of Pa during the triggering period were analyzed in respiratory mechanics. (1) In flow-trigger mode: Pa was pulled down from positive end-expiratory pressure (PEEP) or intrinsic positive end-expiratory pressure (PEEPi) to "PEEP-VTrigR" (R meant airway resistance) without nebulization, and the span of Pa was "VTrigR" or "PEEPi-PEEP+VTrigR". Pa was pulled down from PEEP or PEEPi to "PEEP-(VTrig+N)R" (N meant nebulization airflow) with nebulization, and the span of Pa was "(VTrig+N)R" or "PEEPi-PEEP+(VTrig+N)R". (2) In pressure-trigger mode: Pa was pulled down from PEEP or PEEPi to "PEEP-PTrig-1R" without nebulization, and the span of Pa was "PTrig+1R" or "PEEPi-PEEP+PTrig+1R". Pa was pulled down from PEEP or PEEPi to "PEEP-PTrig-(N+1)R" with nebulization, and the span of Pa was "PTrig+(N+1)R" or "PEEPi-PEEP+PTrig+(N+1)R". Nebulization airflow increases the difficulty of inspiratory triggering in mechanical ventilation. PEEPi makes it more difficult.

The Injurious Effects of Elevated or Nonelevated Respiratory Rate during Mechanical Ventilation.

Respiratory rate is one of the key variables that is set and monitored during mechanical ventilation. As part of increasing efforts to optimize mechanical ventilation, it is prudent to expand understanding of the potential harmful effects of not only volume and pressures but also respiratory rate. The mechanisms by which respiratory rate may become injurious during mechanical ventilation can be distinguished in two broad categories. In the first, well-recognized category, concerning both controlled and assisted ventilation, the respiratory rate per se may promote ventilator-induced lung injury, dynamic hyperinflation, ineffective efforts, and respiratory alkalosis. It may also be misinterpreted as distress delaying the weaning process. In the second category, which concerns only assisted ventilation, the respiratory rate may induce injury in a less apparent way by remaining relatively quiescent while being challenged by chemical feedback. By responding minimally to chemical feedback, respiratory rate leaves the control of e almost exclusively to inspiratory effort. In such cases, when assist is high, weak inspiratory efforts promote ineffective triggering, periodic breathing, and diaphragmatic atrophy. Conversely, when assist is low, diaphragmatic efforts are intense and increase the risk for respiratory distress, asynchronies, ventilator-induced lung injury, diaphragmatic injury, and cardiovascular complications. This review thoroughly presents the multiple mechanisms by which respiratory rate may induce injury during mechanical ventilation, drawing the attention of critical care physicians to the potential injurious effects of respiratory rate insensitivity to chemical feedback during assisted ventilation.

Patient-ventilator asynchrony identified with electrical impedance tomography

Abstract Patient-ventilator asynchrony increases work-of-breathing and prolongs patient weaning from ventilator. Inappropriate triggering might sometimes not be recognized via pressure or flow patterns. In the present study, we demonstrated the feasibility to identify the ineffective triggering of the ventilator using electrical impedance tomography (EIT) in a patient with chronic obstructive pulmonary disease. The patient was mechanically ventilated under assisted-controlled ventilation. Analysis of either global relative impedance-time curves or EIT-derived normalized breathing-cycle-map is able to identify the asynchrony of respiratory time, while the asynchrony was not evident with traditional methods, e.g. ventilator waveforms.

Effects of Propofol on Respiratory Drive and Patient-ventilator Synchrony during Pressure Support Ventilation in Postoperative Patients

Background:Propofol is increasingly used during partial support mechanical ventilation such as pressure support ventilation (PSV) in postoperative patients. However, breathing pattern, respiratory drive, and patient-ventilator synchrony are affected by the sedative used and the sedation depth. The present study aimed to evaluate the physiologic effects of varying depths of propofol sedation on respiratory drive and patient-ventilator synchrony during PSV in postoperative patients.Methods:Eight postoperative patients receiving PSV for <24 h were enrolled. Propofol was administered to achieve and maintain a Ramsay score of 4, and the inspiratory pressure support was titrated to obtain a tidal volume (VT) of 6–8 ml/kg. Then, the propofol dose was reduced to achieve and maintain a Ramsay score of 3 and then 2. At each Ramsay level, the patient underwent 30-min trials of PSV. We measured the electrical activity of the diaphragm, flow, airway pressure, neuro-ventilatory efficiency (NVE), and patient-ventilator synchrony.Results:Increasing the depth of sedation reduced the peak and mean electrical activity of the diaphragm, which suggested a decrease in respiratory drive, while VT remained unchanged. The NVE increased with an increase in the depth of sedation. Minute ventilation and inspiratory duty cycle decreased with an increase in the depth of sedation, but this only achieved statistical significance between Ramsay 2 and both Ramsay 4 and 3 (P < 0.05). The ineffective triggering index increased with increasing sedation depth (9.5 ± 4.0%, 6.7 ± 2.0%, and 4.2 ± 2.1% for Ramsay 4, 3, and 2, respectively) and achieved statistical significance between each pair of depth of sedation (P < 0.05). The depth of sedation did not affect gas exchange.Conclusions:Propofol inhibits respiratory drive and deteriorates patient-ventilator synchrony to the extent that varies with the depth of sedation. Propofol has less effect on breathing pattern and has no effect on VT and gas exchange in postoperative patients with PSV.

Effect of Tidal Volume Size and Its Delivery Mode on Patient-Ventilator Dyssynchrony.

Although increasingly recommended, compliance with low Vt ventilation remains suboptimal. Dyssynchrony induced by low Vts may be a reason for it. To determine the effect of Vt size, and of the ventilator mode used for its delivery (volume vs. pressure control), on the magnitude of patient-ventilator dyssynchrony in patients with or at risk for acute respiratory distress syndrome. Nineteen mechanically ventilated patients underwent six consecutive ventilatory conditions: three on volume assist-control (VC) mode, each with set Vt of 6, 7.5, and 9 ml/kg, and three on adaptive pressure-control (APC) mode, with those same set Vts and matching inspiratory times. Triggering, cycling, and flow dyssynchronies were identified by inspection of airway flow and pressure tracings. A dyssynchrony index (DI) was calculated as the total number of dyssynchronies divided by the sum of ventilator cycles and ineffective triggering events, expressed as percentage. A severe DI was calculated including only double triggering and severe flow dyssynchronies. Under VC mode, the median (interquartile range) DIs were 100% (22-100%) at set Vt of 6 ml/kg, and 78% (7-100) at 7.5 ml/kg, both higher than 25% (0-45%) at 9 ml/kg (P = 0.02 and 0.01, respectively). Severe DI was higher at each reduction of Vt size. Under APC mode, compared with VC, DIs were lower at set Vt of 6 and 7.5 ml/kg (P = 0.004 for both). Changing from VC to APC resulted in an increase in exhaled Vt ≥ 1 ml/kg predicted body weight in a minority of patients. Lower Vts during VC ventilation result in higher patient-ventilator dyssynchrony in most patients with or at risk for acute respiratory distress syndrome. The use of APC mode is an option to reduce dyssynchrony, but it requires careful monitoring to avoid larger-than-target delivered volumes.

The influence of condensate in the piezometric tube on patient ventilator interaction during noninvasive positive pressure ventilation

To study the effects of condensate in the piezometric tube on patient ventilator interaction during noninvasive positive pressure ventilation. Eleven healthy adults volunteered to receive noninvasive positive pressure ventilation. Different capacity of physiological saline was injected gradually into the piezometric tube until the volunteers could not trigger the ventilator or the total volume of the water reached 1.5 ml. The dynamic changes of the pressure of mask(Pmask), piezometric tube near mask (Ppro), piezometric tube near breathing machine(Pdis), and the flow were observed. With increasing volume of saline injected, the trigger time TItri(Pmask) increased from 0.09(0.07-0.11) to 0.31(0.22-0.39)s, the trigger pressure TPtri(Pmask) increased from 0.26(0.15-0.33) to 2.29(1.76-3.09)cmH2O, and the pressure-time product PTP (Pmask) increased from 0.02(0.01-0.03) to 0.55(0.41-0.68) cmH2O·s. Ineffective triggering rate increased from 0 up to 9 times/min, and spurious triggering rate increased from 0 up to 33 times/min. The plateau pressure of Pmask and Ppro exceeded the preset parameters, increased significantly as compared with 0 ml, from (9.74±0.34)to (15.79±3.10) cmH2O and from(9.80±0.31) to(15.44±3.47) cmH2O. The change of plateau pressure of Pdis was not significant [from (9.85±0.29)to (12.58±2.64)cmH2O]. The baseline pressure of Pmask, Ppro and Pdis changed from (3.67±0.36) to (8.40±3.22) cmH2O, from (3.71±0.32) to (8.13±3.55) cmH2O and from( 3.77±0.32) to (5.36±1.25) cmH2O, respectively. The pressure fluctuation of platform of Pmask increased significantly compare with 0 ml, from 0.60(0.48-0.71) to 7.94(7.11-8.63)cmH2O. The frequency of fluctuation of platform increased as many as 7 times during a single respiratory period. The time when the pressure of the Pdis began to change was delayed to Pmask and Ppro, 0.11(0.08-0.12)s compared with 0 ml. Condensate in the piezometric tube during noninvasive positive pressure ventilation could influence patient-ventilator synchrony. To improve patient ventilator interaction in noninvasive positive pressure ventilation, condensate in the piezometric tube should be avoided.

Patient-Ventilator Asynchrony During Assisted Ventilation in Children.

To describe the frequency and type of patient-ventilator asynchrony in mechanically ventilated children by analyzing ventilator flow and pressure signals. Prospective observational study. Tertiary PICU in a university hospital. Mechanically ventilated children between 0 and 18 years old and who were able to initiate and maintain spontaneous breathing were eligible for inclusion. Patients with congenital or acquired neuromuscular disorders, those with congenital or acquired central nervous system disorders, and those who were unable to initiate and maintain spontaneous breathing from any other cause were excluded. None. All patients were ventilated in a time-cycled, pressure-limited mode with flow triggering set at 1.0 L/min by using the Evita XL (Dräger, Lubeck, Germany). Patient-ventilator asynchrony was identified by a random 30-minute continuous recording and an offline analysis of the flow and pressure signals. Patient-ventilator asynchrony was categorized and labeled into four different groups: 1) trigger asynchrony (i.e., insensitive trigger, double triggering, autotriggering, or trigger delay), 2) flow asynchrony, 3) termination asynchrony (i.e., delayed or premature termination), and 4) expiratory asynchrony. Flow and pressure signals were recorded in 45 patients for 30 minutes. A total number of 57,651 breaths were analyzed. Patient-ventilator asynchrony occurred in 19,175 breaths (33%), and it was seen in every patient. Ineffective triggering was the most predominant type of asynchrony (68%), followed by delayed termination (19%), double triggering (4%), and premature termination (3%). Patient-ventilator asynchrony significantly increased with lower levels of peak inspiratory pressure, positive end-expiratory pressure, and set frequency. Patient-ventilator asynchrony is extremely common in mechanically ventilated children, and the predominant cause is ineffective triggering.