Occurrence Of Asynchrony Research Articles

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.

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).

Clinical Influence and Predictors of Pacing-Induced Mechanical Asynchrony in Patients with Normal Cardiac Function with Ventricular Lead Placed in Non-Apical Position.

Right ventricular apical (RVA) pacing often causes left ventricular (LV) mechanical asynchrony, which is enhanced by impaired cardiac contraction and intrinsic conduction abnormality. However, data on patients with normal cardiac function and under RV non-apical (non-RVA) pacing are limited.We retrospectively investigated 97 consecutive patients with normal ejection fraction who received pacemaker implantation for atrioventricular block with the ventricular lead placed in a non-RVA position. We defined mechanical asynchrony as discoordinate contraction between opposing regions of the LV wall evaluated by echocardiography. Asynchrony was detected in 9 (9%) patients at baseline and in 38 (39%) under non-RVA pacing (P < 0.001). Asynchrony at baseline was significantly associated with complete left bundle branch block (CLBBB) [odds ratio (OR) = 20.8, P < 0.001]. Asynchrony under non-RVA pacing was significantly associated with left anterior fascicular block (LAFB) (OR = 7.14, P < 0.001) and CLBBB (OR = 13.3, P = 0.002) at baseline. New occurrence of asynchrony was significantly associated with LAFB at baseline (OR = 5.88, P = 0.001). During a median follow-up period of 4.8 years, the incidence of device-detected atrial fibrillation (AF) was more frequent in patients who developed asynchrony than in those who did not (53.3% versus 27.5%, hazard ratio = 2.17, 95% confidence interval = 1.02-4.61, P = 0.03).In patients with normal cardiac function, LAFB at baseline was significantly associated with new occurrence of mechanical asynchrony under non-RVA pacing. Abnormal contraction had a significant influence on the incidence of device-detected AF.

EARLY OVULE DEVELOPMENT, MEGASPOROGENESIS AND MEGAGAMETOGENESIS IN SOLIDAGO GRAMINIFOLIA VAR. NUTTALLII AND SOLIDAGO CANADENSIS VAR. CANADENSIS (ASTERALES: ASTERACEAE: TUBULIFLORAE: ASTEREAE)

A description of developmental sequences leading to maturity of the megagametophyte in two species of Solidago (L.) is presented to allow comparisons in: (1) dimensional relationships; (2) simultaneity of homotypic meiotic divisions of megasporogenesis; and (3) tetrad formation. A lack of consistency in the coordination of nucellar and integumental development, the occurrence of asynchrony in the mitotic divisions of megagametogenesis, polyantipodality in mature female gametophytes, and ease of tissue clearing are attributes common to both species. They are presented as additional distinguishing features to augment the characterization of the megagametophyte generation of Solidago, a highly plastic genus which is, embryologically, virtually unknown.

Early Ovule Development, Megasporogenesis and Megagametogenesis in Solidago Graminifolia Var. Nuttallii and Solidago Canadensis Var. Canadensis (Asterales: Asteraceae: Tubuliflorae: Astereae)

A description of developmental sequences leading to maturity of the megagametophyte in two species of Solidago (L.) is presented to allow comparisons in: (1) dimensional relationships; (2) simultaneity of homotypic meiotic divisions of megasporogenesis; and (3) tetrad formation. A lack of consistency in the coordination of nucellar and integumental development, the occurrence of asynchrony in the mitotic divisions of megagametogenesis, polyantipodality in mature female gametophytes, and ease of tissue clearing are attributes common to both species. They are presented as additional distinguishing features to augment the characterization of the megagametophyte generation of Solidago, a highly plastic genus which is, embryologically, virtually unknown.