Prevalence, Proportionality, and Cause of Ventilator Alarms in a Pediatric Intensive Care Setting.

BACKGROUND: Clinical alarms play an important role in monitoring physiological parameters, vital signs and medical device function in the hospital intensive care environment. Delays in staff response to alarms are well documented as health care providers become desensitized to increased rates of nuisance alarms. Patients can be at increased risk of harm due to alarm fatigue. Current literature suggests alarms from ventilators contribute significantly to nonactionable alarms. A greater understanding of which specific ventilator alarms are most common and the rates at which they occur is fundamental to improving alarm management. METHODS: A retrospective review was performed on alarms that occurred on the Avea and Servo-i ventilators used in the pediatric ICU and pediatric cardiothoracic ICU at a major metropolitan children's hospital. High- and medium-priority alarms, as classified by the manufacturer, were studied between June 1, 2017, and November 31, 2017. Descriptive data analysis and a 2-proportion z-test were performed to identify proportionality, cause, and prevalence rates in the pediatric ICU and the cardiothoracic ICU. RESULTS: Eleven distinct ventilator alarms were identified during 2,091 d of mechanical ventilation. The Inspiratory Flow Overrange alarm (42.4%) on the Servo-i, Low VTE (20.4%; expiratory tidal volume) and Circuit Integrity alarm (20.0%) on the Avea were the most prevalent causes according to ventilator type. Medium-priority alarms comprised 68.7% of all Servo-i alarms, and high-priority alarms comprised 84% of all Avea alarms. The 2-sample test of proportions was significant for differences between both areas (P < .001). The overall alarm prevalence rate was 22.5 ventilator alarms per ventilator-day per patient. CONCLUSIONS: The cause and proportion of alarms varied by ventilator and care unit. High-priority alarms were most common with the Avea and medium-priority alarms for the Servo-i. The overall combined ventilator alarm prevalence rate was 22.5 alarms per ventilator-day per patient.

High Breath-by-Breath Variability Is Associated With Extubation Failure in Children.

OBJECTIVES: Extubation failure is multifactorial, and most tools to assess extubation readiness only evaluate snapshots of patient physiology. Understanding variability in respiratory variables may provide additional information to inform extubation readiness assessments. DESIGN: Secondary analysis of prospectively collected physiologic data of children just prior to extubation during a spontaneous breathing trial. Physiologic data were cleaned to provide 40 consecutive breaths and calculate variability terms, coefficient of variation and autocorrelation, in commonly used respiratory variables (i.e., tidal volume, minute ventilation, and respiratory rate). Other clinical variables included diagnostic and demographic data, median values of respiratory variables during spontaneous breathing trials, and the change in airway pressure during an occlusion maneuver to measure respiratory muscle strength (maximal change in airway pressure generated during airway occlusion [PiMax]). Multivariable models evaluated independent associations with reintubation and prolonged use of noninvasive respiratory support after extubation. SETTING: Acute care, children's hospital. PATIENTS: Children were included from the pediatric and cardiothoracic ICUs who were greater than 37 weeks gestational age up to and including 18 years who were intubated greater than or equal to 12 hours with planned extubation. We excluded children who had a contraindication to an esophageal catheter or respiratory inductance plethysmography bands. INTERVENTIONS: Noninterventional study. MEASUREMENTS AND MAIN RESULTS: A total of 371 children were included, 32 of them were reintubated. Many variability terms were associated with reintubation, including coefficient of variation and autocorrelation of the respiratory rate. After controlling for confounding variables such as age and neurologic diagnosis, both coefficient of variation of respiratory rate(p < 0.001) and low PiMax (p = 0.002) retained an independent association with reintubation. Children with either low PiMax or high coefficient of variation of respiratory rate had a nearly three-fold higher risk of extubation failure, and when these children developed postextubation upper airway obstruction, reintubation rates were greater than 30%. CONCLUSIONS: High respiratory variability during spontaneous breathing trials is independently associated with extubation failure in children, with very high rates of extubation failure when these children develop postextubation upper airway obstruction.

Phenotype of ventilatory control in children with moderate to severe persistent asthma and obstructive sleep apnea.

STUDY OBJECTIVES: To examine the role of ventilatory control in asthmatic children with obstructive sleep apnea (OSA) and the relationships between measures of ventilatory control, OSA severity, and pulmonary function. METHODS: Five- to 18-year-old children with persistent asthma and nightly snoring were enrolled in the study. Children had physical examination, pulmonary function test, and polysomnography. Loop and controller gains were derived from 5 min segments which included a sigh during nonrapid eye movement sleep by applying a mathematical model that quantifies ventilatory control from the ensuing responses to the sighs. Plant gain was derived from 5 min segments of spontaneous breathing (i.e. without sighs). Nonparametric statistical tests were used for group comparisons. Cluster analysis was performed using Bayesian profile regression. RESULTS: One hundred thirty-four children were included in the study, 77 with and 57 without OSA. Plant gain was higher in children with OSA than in those without OSA (p = 0.002). A negative correlation was observed between plant gain and forced expiratory volume in 1 second (p = 0.048) and the ratio of f forced expiratory volume to forced vital capacity (p = 0.02). Plant gain correlated positively with severity of OSA. Cluster analysis demonstrated that children with more severe OSA and abnormal lung function had higher plant gain and a lower controller gain compared with the rest of the population. CONCLUSIONS: Children with OSA and persistent asthma with abnormal lung function have phenotypic characteristics which consist of diminished capacity of the lungs to maintain blood gas homeostasis reflected by an increase in plant gain and decreased chemoreceptor sensitivity.

The effect of adenotonsillectomy on ventilatory control in children with obstructive sleep apnea.

STUDY OBJECTIVES: The contribution of ventilatory control to the pathogenesis of obstructive sleep apnea (OSA) in children and the effect of adenotonsillectomy are unknown. We aimed to examine the difference in ventilatory control between children with OSA and those without OSA. We also examined the effect of adenotonsillectomy on parameters of ventilatory control. METHODS: Healthy children with OSA and matched controls were recruited. Polysomnography was performed before adenotonsillectomy in the OSA group and 6 months postoperatively. Controls underwent the same assessment at the two time points. Loop gain (LG), controller gain (CG), and plant gain (PG), which reflect the stability of ventilatory control, chemoreceptor sensitivity and the pulmonary control of blood gas in response to a change in ventilation, respectively, were estimated from polysomnographic tracings which included spontaneous sighs and tracings with tidal breathing. A linear mixed model was used to examine the changes of the ventilatory control parameters from baseline to 6 months. RESULTS: Ninety-nine children aged 7-13 were recruited to the study. Fifty-three with OSA and 46 controls. At baseline, compared with controls, children with OSA had higher PG and lower CG. LG did not differ between groups. Six months following adenotonsillectomy, there was a significant decrease in PG in the OSA group, while no change observed in the control group. CONCLUSIONS: The study demonstrates that the pulmonary control of blood gas homeostasis is disturbed in children with OSA and it normalizes following adenotonsillectomy.

Quantifying ventilatory control stability from spontaneous sigh responses during sleep: a comparison of two approaches.

RATIONALE: Ventilatory control instability is an important factor contributing to the pathogenesis of periodic breathing (PB) and other forms of sleep-related breathing disorders (SRBD). The development of tools for the quantification of such instabilities from non-invasive respiratory measurements during sleep could be useful to clinicians in identifying subjects that are at risk of developing SRBD. OBJECTIVES: To present and compare two different mathematical modeling approaches that allow the quantification of ventilatory control stability from the ventilatory responses to spontaneous sighs. MEASUREMENTS AND METHODS: Breath-by-breath measurements of normalized ventilation were derived from respiratory inductance plethysmography (RIP) traces collected during sleep from a cohort of 19 preterm infants with various degrees of periodic breathing. A hypothesis-based minimal closed-loop model consisting of a gain, time-constant and time delay; and a data-driven autoregressive model with time delay were used to fit the ventilatory responses to the spontaneous sighs. Loop gain, a quantitative measure of ventilatory control stability, was extracted from both models. RESULTS AND DISCUSSION: Both approaches accurately described the ensuing responses to the sighs. Significant and robust correlations were found in the loop gain estimates extracted with the two models in the frequency range spanning 2-8 cycles min-1, which corresponds to PB cycling oscillations in infants. In addition, the hypothesis-based model showed a decreased within-subject variability of the estimated stability quantifiers, while the data-driven better resembled the experimental data. There are advantages and limitations associated with each of the modeling approaches which are discussed in the paper. CONCLUSIONS: The agreement found between the two mathematical models indicates that either methodology can be used indistinctively providing reliable results and their application can expand to sigh data from other clinical cohorts of preterm infants.

Assessing ventilatory instability using the response to spontaneous sighs during sleep in preterm infants.

Study Objectives: Periodic breathing (PB) is common in newborns and is an obvious manifestation of ventilatory control instability. However, many infants without PB may still have important underlying ventilatory control instabilities that go unnoticed using standard clinical monitoring. Methods to detect infants with "subclinical" ventilatory control instability are therefore required. The current study aimed to assess the degree of ventilatory control instability using simple bedside recordings in preterm infants. Methods: Respiratory inductance plethysmography (RIP) recordings were analyzed from ~20 minutes of quiet sleep in 20 preterm infants at 36 weeks post-menstrual age (median [range]: 36 [34-40]). The percentage time spent in PB was also calculated for each infant (%PB). Spontaneous sighs were identified and breath-by-breath measurements of (uncalibrated) ventilation were derived from RIP traces. Loop gain (LG, a measure of ventilatory control instability) was calculated by fitting a simple ventilatory control model (gain, time-constant, delay) to the post-sigh ventilatory pattern. For comparison, periodic inter-breath variability was also quantified using power spectral analysis (ventilatory oscillation magnitude index [VOMI]). Results: %PB was strongly associated with LG (r2 = 0.77, p < 0.001) and moderately with the VOMI (r2 = 0.21, p = 0.047). LG (0.52 ± 0.05 vs. 0.30 ± 0.03; p = 0.0025) and the VOMI (-8.2 ± 1.1 dB vs. -11.8 ± 0.9 dB; p = 0.026) were both significantly higher in infants that displayed PB vs. those without. Conclusions: LG and VOMI determined from the ventilatory responses to spontaneous sighs can provide a practical approach to assessing ventilatory control instability in preterm infants. Such simple techniques may help identify infants at particular risk for ventilatory instabilities with concomitant hypoxemia and its associated consequences.

Cardioventilatory Control in Preterm-born Children and the Risk of Obstructive Sleep Apnea.

RATIONALE: The contribution of ventilatory control to the pathogenesis of obstructive sleep apnea (OSA) in preterm-born children is unknown. OBJECTIVES: To characterize phenotypes of ventilatory control that are associated with the presence of OSA in preterm-born children during early childhood. METHODS: Preterm- and term-born children without comorbid conditions were enrolled. They were categorized into an OSA group and a non-OSA group on the basis of polysomnography. MEASUREMENTS AND MAIN RESULTS: Loop gain, controller gain, and plant gain, reflecting ventilatory instability, chemoreceptor sensitivity, and blood gas response to a change in ventilation, respectively, were estimated from spontaneous sighs identified during polysomnography. Cardiorespiratory coupling, a measure of brainstem maturation, was estimated by measuring the interval between inspiration and the preceding electrocardiogram R-wave. Cluster analysis was performed to develop phenotypes based on controller gain, plant gain, cardiorespiratory coupling, and gestational age. The study included 92 children, 63 of whom were born preterm (41% OSA) and 29 of whom were born at term (48% OSA). Three phenotypes of ventilatory control were derived with risks for OSA being 8%, 47%, and 77% in clusters 1, 2, and 3, respectively. There was a stepwise decrease in controller gain and an increase in plant gain from clusters 1 to 3. Children in cluster 1 had significantly higher cardiorespiratory coupling and gestational age than clusters 2 and 3. No difference in loop gain was found between clusters. CONCLUSIONS: The risk for OSA could be stratified according to controller gain, plant gain, cardiorespiratory coupling, and gestational age. These findings could guide personalized care for children at risk for OSA.