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Abstract Background Reverse triggering (RT) was described in 2013 as a form of patient-ventilator asynchrony, where patient’s respiratory effort follows mechanical insufflation. Diagnosis requires esophageal pressure (Pes) or diaphragmatic electrical activity (EAdi), but RT can also be diagnosed using standard ventilator waveforms. Hypothesis We wondered (1) how frequently RT would be present but undetected in the figures from literature, especially before 2013; (2) whether it would be more prevalent in the era of small tidal volumes after 2000. Methods We searched PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials, from 1950 to 2017, with key words related to asynchrony to identify papers with figures including ventilator waveforms expected to display RT if present. Experts labelled waveforms. ‘Definite’ RT was identified when Pes or EAdi were in the tracing, and ‘possible’ RT when only flow and pressure waveforms were present. Expert assessment was compared to the author’s descriptions of waveforms. Results We found 65 appropriate papers published from 1977 to now, containing 181 ventilator waveforms. 21 cases of ‘possible’ RT and 25 cases of ‘definite’ RT were identified by the experts. 18.8% of waveforms prior to 2013 had evidence of RT. Most cases were published after 2000 (1 before vs. 45 after, p = 0.03). 54% of RT cases were attributed to different phenomena. A few cases of identified RT were already described prior to 2013 using different terminology (earliest in 1997). While RT cases attributed to different phenomena decreased after 2013, 60% of ‘possible’ RT remained missed. Conclusion RT has been present in the literature as early as 1997, but most cases were found after the introduction of low tidal volume ventilation in 2000. Following 2013, the number of undetected cases decreased, but RT are still commonly missed. Prior Abstract Reverse Triggering, A Missed Phenomenon in the Literature. Critical Care Canada Forum 2019 Abstracts. Can J Anesth/J Can Anesth 67 (Suppl 1), 1–162 (2020). https://doi-org.myaccess.library.utoronto.ca/ https://doi.org/10.1007/s12630-019-01552-z .

Background: Reverse triggering (RT) was described in 2013 as a form of patient-ventilator asynchrony, where patient's respiratory effort follows mechanical insufflation. Diagnosis requires esophageal pressure (Pes) or diaphragmatic electrical activity (EAdi), but RT can also be diagnosed using standard ventilator waveforms. Hypothesis: We wondered (1) how frequently RT would be present but undetected in the figures from literature, especially before 2013; (2) whether it would be more prevalent in the era of small tidal volumes after 2000. Methods: We searched PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials, from 1950 to 2017, with key words related to asynchrony to identify papers with figures including ventilator waveforms expected to display RT if present. Experts labelled waveforms. 'Definite' RT was identified when Pes or EAdi were in the tracing, and 'possible' RT when only flow and pressure waveforms were present. Expert assessment was compared to the author's descriptions of waveforms. Results: We found 65 appropriate papers published from 1977 to now, containing 181 ventilator waveforms. 21 cases of 'possible' RT and 25 cases of 'definite' RT were identified by the experts. 18.8% of waveforms prior to 2013 had evidence of RT. Most cases were published after 2000 (1 before vs. 45 after, p = 0.03). 54% of RT cases were attributed to different phenomena. A few cases of identified RT were already described prior to 2013 using different terminology (earliest in 1997). While RT cases attributed to different phenomena decreased after 2013, 60% of 'possible' RT remained missed. Conclusion: RT has been present in the literature as early as 1997, but most cases were found after the introduction of low tidal volume ventilation in 2000. Following 2013, the number of undetected cases decreased, but RT are still commonly missed. Reverse Triggering, A Missed Phenomenon in the Literature. Critical Care Canada Forum 2019 Abstracts. Can J Anesth/J Can Anesth 67 (Suppl 1), 1–162 (2020). https://doi-org.myaccess.library.utoronto.ca/https://doi.org/10.1007/s12630-019-01552-z. [ABSTRACT FROM AUTHOR]

Abstract Background Ineffective 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. Design Observational assessment followed by prospective cross-over physiological study. Setting Academic medical ICU. Patients Ineffective 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. Interventions Physiological 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. Measurements Primary endpoint was the comparison of asynchrony index between PSV and PAV+ after PSL and gain adjustments. Results Among 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

Patient self-inflicted lung injury may be associated with worse clinical outcomes and higher mortality. Patient-ventilator asynchrony is associated with increased ventilator days and mortality, and it has been hypothesised as one of the important mechanisms leading to patient self-inflicted lung injury. However, given the observational nature of the key studies in the field so far, the hypothesis that patient-ventilator asynchrony causes patient self-inflicted lung injury has not been supported by evidence yet. Wittenstein and colleagues present a novel approach that enables controlling patient-ventilator asynchrony in a pig model of acute lung injury, to investigate the patient-ventilator asynchrony and patient self-inflicted lung injury causality. Their results suggest that increased patient-ventilator asynchrony associated with poor clinical outcomes reported in observational trials could be a marker, rather than a cause of patient self-inflicted lung injury. These findings on their own are not sufficient to justify a greater tolerance of patient-ventilator asynchrony amongst clinicians, a change for which further experimental work and clinical evidence is needed. [ABSTRACT FROM AUTHOR]

Background: Ineffective 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. Design: Observational assessment followed by prospective cross-over physiological study. Setting: Academic medical ICU. Patients: Ineffective 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. Interventions: Physiological 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. Measurements: Primary endpoint was the comparison of asynchrony index between PSV and PAV+ after PSL and gain adjustments. Results: Among 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). Conclusions: Among 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. [ABSTRACT FROM AUTHOR]

Research in the area of adult invasive mechanical ventilation is rich and diverse. With more than 3,200 articles on mechanical ventilation published in 2018, isolating the most relevant literature is a challenge. Separated into 5 themes (ie, ventilatory support, hyperoxia, ventilator-associated events, prevention of events, and ventilator liberation), this article will describe the most important papers published on adult invasive mechanical ventilation in 2018. [ABSTRACT FROM AUTHOR]

Ventilator auto-trigger is the delivery of an assisted mechanical ventilated breath over the set ventilator frequency in the absence of a spontaneous inspiratory effort and can be caused by inappropriate ventilator trigger sensitivity. Ventilator auto-trigger can be misinterpreted as a spontaneous breath and has the potential to delay or prevent brain death testing and confuse health-care professionals and/or patient families.~Context~Background~To determine the frequency of organ donor referrals from 1 Organ Procurement Organization (OPO) that could benefit from an algorithm designed to assist organ recovery coordinators to identify and correct ventilator auto-triggering.~Objective~Objective~This retrospective analysis evaluated documentation of organ donor referrals from 1 OPO in central Texas during the 2013 calendar year that resulted in the withdrawal of care by the patient's family and the recovery of organs.~Design~Methods~The frequency of referrals that presented with absent brain stem reflexes except for additional respirations over the set ventilator rate was determined to assess for the need of the proposed algorithm.~Main Outcome Measures~Methods~Documentation of 672 organ procurement organization referrals was evaluated. Documentation from 42 referrals that resulted in the withdrawal of care and 21 referrals that resulted in the recovery of organs were identified with absent brain stem reflexes except for spontaneous respirations on the mechanical ventilator. As a result, an algorithm designed to identify and correct ventilator auto-trigger could have been used 63 times during the 2013 calendar year.~Results~Results [ABSTRACT FROM AUTHOR]

Objectives: To report on the monitoring of diaphragm electrical activity (Edi) using neurally adjusted ventilator assist (NAVA) technology to investigate the mechanisms of ventilator dependence in children with neuromuscular and respiratory control disorders. Patients and methods: Using NAVA technology, electrical activity of the diaphragm (Edi) was monitored at the lowest achievable level of respiratory support in six ventilator-dependent patients with neuromuscular and respiratory control disorders, aged 6 weeks to 12 years, admitted to a tertiary paediatric intensive care unit between 2009 and 2011. Results: Edi monitoring identified markedly abnormal respiratory dynamic patterns that were not always apparent clinically. These were associated with disorders of central respiratory control, muscle weakness and diaphragm pathology. Conclusions: Edi monitoring using NAVA technology is a valuable, minimally invasive, diagnostic adjunct in children with neuromuscular and respiratory control disorders who are ventilator-dependent. [ABSTRACT FROM AUTHOR]