Equilibration Time Required for Respiratory System Compliance and Oxygenation Response Following Changes in Positive End-Expiratory Pressure in Mechanically Ventilated Children.

OBJECTIVES: Increases in positive end-expiratory pressure are implemented to improve oxygenation through the recruitment and stabilization of collapsed alveoli. However, the time it takes for a positive end-expiratory pressure change to have maximum effect upon oxygenation and pulmonary compliance has not been adequately described in children. Therefore, we sought to quantify the time required for oxygenation and pulmonary system compliance changes in children requiring mechanical ventilation. DESIGN: Retrospective analysis of continuous data. SETTINGS: Multidisciplinary ICU of a pediatric university hospital. PATIENTS: Mechanically ventilated pediatric subjects. INTERVENTIONS: A case was eligible for analysis if during a 90-minute window following an increase in positive end-expiratory pressure, no other changes to the ventilator were made, ventilator and physiologic data were continuously available and a positive oxygenation response was observed. Time to 90% (T90) of the maximum change in oxygenation and compliance was computed. Differences between oxygenation and compliance T90 were compared using a paired t test. The effect of severity of illness (by oxygen saturation index) upon oxygenation and compliance was analyzed. MEASUREMENTS AND MAIN RESULTS: A total of 200 subjects were enrolled and 1,150 positive end-expiratory pressure change cases were analyzed. Of these, 54 subjects with 171 positive end-expiratory pressure change case were included in the analysis (67% were responders).Changes in dynamic compliance (T90 = 38 min) preceded changes in oxygenation (T90 = 71 min; p < 0.001). Oxygenation response differed depending on severity of illness quantified by oxygen saturation index; lung dysfunction was associated with a longer response time (p = 0.001). CONCLUSIONS: T90 requires 38 and 71 minutes for dynamic pulmonary compliance and oxygenation, respectively; the latter was directly observed to be dependent upon severity of illness. To our knowledge, this is the first report of oxygenation and compliance equilibration data following positive end-expiratory pressure increases in pediatric mechanically ventilated subjects.

High-Frequency Oscillatory Ventilation in Pediatric Acute Lung Injury: A Multicenter International Experience.

OBJECTIVE: We aim to describe current clinical practice, the past decade of experience and factors related to improved outcomes for pediatric patients receiving high-frequency oscillatory ventilation. We have also modeled predictive factors that could help stratify mortality risk and guide future high-frequency oscillatory ventilation practice. DESIGN: Multicenter retrospective, observational questionnaire study. SETTING: Seven PICUs. PATIENTS: Demographic, disease factor, and ventilatory and outcome data were collected, and 328 patients from 2009 to 2010 were included in this analysis. INTERVENTIONS: None. MEASUREMENT AND MAIN RESULTS: Patients were classified into six cohorts based on underlying diagnosis. We used univariate analysis to identify factors associated with mortality risk and multivariate logistic regression to identify independent predictors of mortality risk. An oxygenation index greater than 35 and immunocompromise exhibited the greatest predictive power (p < 0.0001) for increased mortality risk, and respiratory syncytial virus was associated with lowest mortality risk (p = 0.003). Differences in mortality risk as a function of oxygenation index were highly dependent on primary underlying condition. A trend toward an increase in oscillator amplitude and frequency was observed when compared with historical data. CONCLUSIONS: Given the number of centers and subjects included in the database, these findings provide a robust description of current practice regarding the use of high-frequency oscillatory ventilation for pediatric hypoxic respiratory failure. Patients with severe hypoxic respiratory failure and immunocompromise had the highest mortality risk, and those with respiratory syncytial virus had the lowest. A means of identifying the risk of 30-day mortality for subjects can be obtained by identifying the underlying disease and oxygenation index on conventional ventilation preceding the initiation of high-frequency oscillatory ventilation.

Mechanical ventilation guided by electrical impedance tomography in experimental acute lung injury.

OBJECTIVE: To utilize real-time electrical impedance tomography to guide lung protective ventilation in an animal model of acute respiratory distress syndrome. DESIGN: Prospective animal study. SETTING: Animal research center. SUBJECTS: Twelve Yorkshire swine (15 kg). INTERVENTIONS: Lung injury was induced with saline lavage and augmented using large tidal volumes. The control group (n = 6) was ventilated using ARDSnet guidelines, and the electrical impedance tomography-guided group (n = 6) was ventilated using guidance with real-time electrical impedance tomography lung imaging. Regional electrical impedance tomography-derived compliance was used to maximize the recruitment of dependent lung and minimize overdistension of nondependent lung areas. Tidal volume was 6 mL/kg in both groups. Computed tomography was performed in a subset of animals to define the anatomic correlates of electrical impedance tomography imaging (n = 5). Interleukin-8 was quantified in serum and bronchoalveolar lavage samples. Sections of dependent and nondependent regions of the lung were fixed in formalin for histopathologic analysis. MEASUREMENTS AND MAIN RESULTS: Positive end-expiratory pressure levels were higher in the electrical impedance tomography-guided group (14.3 cm H2O vs. 8.6 cm H2O; p < 0.0001), whereas plateau pressures did not differ. Global respiratory system compliance was improved in the electrical impedance tomography-guided group (6.9 mL/cm H2O vs. 4.7 mL/cm H2O; p = 0.013). Regional electrical impedance tomography-derived compliance of the most dependent lung region was increased in the electrical impedance tomography group (1.78 mL/cm H2O vs. 0.99 mL/cm H2O; p = 0.001). Pao2/FIO2 ratio was higher and oxygenation index was lower in the electrical impedance tomography-guided group (Pao2/FIO2: 388 mm Hg vs. 113 mm Hg, p < 0.0001; oxygentation index, 6.4 vs. 15.7; p = 0.02) (all averages over the 6-hr time course). The presence of hyaline membranes (HM) and airway fibrin (AF) was significantly reduced in the electrical impedance tomography-guided group (HMEIT 42% samples vs. HMCONTROL 67% samples, p < 0.01; AFEIT 75% samples vs. AFCONTROL 100% samples, p < 0.01). Interleukin-8 level (bronchoalveolar lavage) did not differ between the groups. The upper and lower 95% limits of agreement between electrical impedance tomography and computed tomography were ± 16%. CONCLUSIONS: Electrical impedance tomography-guided ventilation resulted in improved respiratory mechanics, improved gas exchange, and reduced histologic evidence of ventilator-induced lung injury in an animal model. This is the first prospective use of electrical impedance tomography-derived variables to improve outcomes in the setting of acute lung injury.

Reversal of dependent lung collapse predicts response to lung recruitment in children with early acute lung injury.

OBJECTIVE: To describe the resolution of regional atelectasis and the development of regional lung overdistension during a lung-recruitment protocol in children with acute lung injury. DESIGN: Prospective interventional trial. SETTING: Pediatric intensive care unit. PATIENTS: Ten children with early (<72 hrs) acute lung injury. INTERVENTIONS: Sustained inflation maneuver (positive airway pressure of 40 cm H2O for 40 secs), followed by a stepwise recruitment maneuver (escalating plateau pressures by 5 cm H2O every 15 mins) until physiologic lung recruitment, defined by PaO2 + PaCO2 ≥400 mm Hg, was achieved. Regional lung volumes and mechanics were measured using electrical impedance tomography. MEASUREMENTS AND MAIN RESULTS: Patients that responded to the stepwise lung-recruitment maneuver had atelectasis in 54% of the dependent lung regions, while nonresponders had atelectasis in 10% of the dependent lung regions (p = .032). In the pressure step preceding physiologic lung recruitment, a significant reversal of atelectasis occurred in 17% of the dependent lung regions (p = .016). Stepwise recruitment overdistended 8% of the dependent lung regions in responders, but 58% of the same regions in nonresponders (p < .001). Lung compliance in dependent lung regions increased in responders, while compliance in nonresponders did not improve. In contrast to the stepwise recruitment maneuver, the sustained inflation did not produce significant changes in atelectasis or oxygenation: atelectasis was only reversed in 12% of the lung (p = .122), and there was only a modest improvement in oxygenation (27 ± 14 mm Hg, p = .088). CONCLUSIONS: Reversal of atelectasis in the most dependent lung region preceded improvements in gas exchange during a stepwise lung-recruitment strategy. Lung recruitment of dependent lung areas was accompanied by considerable overdistension of nondependent lung regions. Larger amounts of atelectasis in dependent lung areas were associated with a positive response to a stepwise lung-recruitment maneuver.

Quality of life of pediatric cardiac patients who previously required extracorporeal membrane oxygenation.

OBJECTIVES: We sought to assess quality of life of pediatric cardiac extracorporeal membrane oxygenation survivors. We hypothesized that these patients would have decreased quality of life when compared to that of a general U.S. population sample. DESIGN: Cross-sectional study. SETTING: Patient homes and Children's Hospital Boston. PATIENTS: Cardiac extracorporeal membrane oxygenation survivors currently 5-18 yrs old. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Quality of life was assessed by parent proxy report using the Child Health Questionnaire Parent Form 50 and was compared to that of a general U.S. population sample and other cardiac populations. Factors associated with lower quality of life were sought. Physical summary scores for 41 cardiac extracorporeal membrane oxygenation survivors were lower than the mean of the general population sample (42.4 ± 16.4 vs. 53.0 ± 8.8; p < .001) but similar to those of children with Fontan physiology or an automatic implantable cardioverter defibrillator. Psychosocial summary scores in extracorporeal membrane oxygenation patients were not different from those of the general population (48.2 ± 11.8 vs. 51.2 ± 9.1; p = .11) or of other cardiac samples. Postcardiotomy extracorporeal membrane oxygenation, more noncardiac operations, total intensive care and hospital days, noncardiac medical conditions, medications, and the need for physical, occupational, or speech therapy were associated with low physical summary scores. More noncardiac operations, noncardiac medical conditions, and the need for special education, physical, occupational, or speech therapy were associated with low psychosocial summary scores. CONCLUSIONS: In pediatric cardiac extracorporeal membrane oxygenation survivors, the physical component of health-related quality of life is lower than that of the general population but similar to that of patients with complex cardiac disease, whereas psychosocial quality of life is similar to that of the general population and of other pediatric cardiac populations.

Isoflurane for life-threatening bronchospasm: a 15-year single-center experience.

BACKGROUND: Children with severe bronchospasm requiring mechanical ventilation may become refractory to conventional therapy. In these critically ill patients, isoflurane is an inhaled anesthetic agent available in some centers to treat bronchospasm. We hypothesized that isoflurane is safe and would lead to improved gas exchange in children with life-threatening bronchospasm refractory to conventional therapy. METHODS: A retrospective review was conducted and included mechanically ventilated children treated with isoflurane in a quaternary pediatric ICU for life-threatening bronchospasm, from 1993 to 2007. Demographic, blood gas, ventilator, and outcome data were collected. RESULTS: Thirty-one patients, with a mean age of 9.5 years (range 0.4-23 years) were treated with isoflurane, from 1993 to 2007. Mean time to initiation of isoflurane after intubation was 13 hours (0-120 h), and the mean maximum isoflurane dose was 1.1% (0.3-2.5%). Mean duration of isoflurane administration was 54.5 hours (range 1-181 h), with a total mean duration of mechanical ventilation of 252 hours (range 16-1,444 h). Isoflurane led to significant improvement in pH and P(CO(2)) within 4 hours of initiation (P ≤ .001). Complications during isoflurane administration included hypotension requiring vasoactive infusions in 24 (77%), arrhythmia in 3 (10%), neurologic side effects in 3 (10%), and pneumothorax in 1 (3%) patient. CONCLUSIONS: Isoflurane led to improvement in pH and P(CO(2)) within 4 hours in this series of mechanically ventilated patients with life-threatening bronchospasm. The majority of patients in this series developed hypotension, but there was a low incidence of other side effects related to isoflurane administration. Isoflurane appears to be an effective therapy in patients with life-threatening bronchospasm refractory to conventional therapy. However, further investigation is warranted, given the uncertain overall impact of isoflurane in this context.

A spontaneous breathing trial with pressure support overestimates readiness for extubation in children.

OBJECTIVE: To evaluate the performance of an extubation readiness test based on a spontaneous breathing trial using pressure support. DESIGN: Retrospective chart review. SETTING: Pediatric intensive care unit. PATIENTS: All infants and children admitted to the pediatric intensive care unit requiring intubation from July 2007 to December 2008 were eligible for this study. INTERVENTIONS: Routine use of an extubation readiness test using pressure support set according to endotracheal tube size to determine completion of weaning and readiness for extubation. MEASUREMENTS AND MAIN RESULTS: A total of 755 extubation readiness tests were performed in 538 patients with a pass rate of 83%. Of 500 children who passed the extubation readiness test and were extubated without planned noninvasive ventilation use, the extubation failure rate was 11.2% (5.8% required reintubation). Extubation failure was defined as need for noninvasive ventilation or reintubation within 24 hrs of planned extubation. Logistic regression analysis revealed a significant association between duration of mechanical ventilation and extubation failure. Children ventilated for over 48 hrs had an 18.5% failure rate despite passing an extubation readiness test before extubation and the extubation readiness test was not a significant predictor of extubation success. Most extubation failures were the result of inadequate gas exchange attributable to lower respiratory tract dysfunction. CONCLUSIONS: A spontaneous breathing trial using pressure support set at higher levels for smaller endotracheal tubes overestimates readiness for extubation in children and contributes to a higher failed extubation rate. The objective data obtained during an extubation readiness test may help to identify patients who will benefit from extubation to noninvasive ventilation.

Pediatric respiratory diseases: 2011 update for the Rogers' Textbook of Pediatric Intensive Care.

OBJECTIVES: To review articles relevant to the field of pediatric respiratory disease that were published after the 2008 Rogers' Textbook of Pediatric Intensive Care. DATA SOURCES: The authors searched the PubMed database (http://www.ncbi.nlm.nih.gov/sites/entrez) from the National Library of Medicine for citations from the pediatric and adult literature relevant to pediatric status asthmaticus, bronchiolitis, pneumonia, acute lung injury, acute respiratory distress syndrome, and neonatal respiratory failure. The authors also searched the reference lists of key primary publications and recent review articles, and queried the National Institutes of Health's ClinicalTrials.gov Web site (www.clinicaltrials.gov) to obtain information about ongoing clinical trials for acute lung injury. The authors had knowledge of new publications in the field of respiratory monitoring, which were considered for inclusion in the review. STUDY SELECTION AND DATA EXTRACTION: The authors reviewed the promising articles and the decision to include any article in the review was based on its potential to inform pediatric intensive care practice or future research. DATA SYNTHESIS: Articles in six categories were selected for inclusion: status asthmaticus, bronchiolitis, pneumonia, acute lung injury/acute respiratory distress syndrome, respiratory monitoring, and neonatal respiratory failure. CONCLUSIONS: There have been important new developments relevant to the pathogenesis and management of pediatric respiratory diseases. In particular, new insights into the causal pathways of respiratory syncytial virus-induced airways disease can potentially lead to novel therapies. Computed tomography imaging of the injured lung during mechanical ventilation has opened new avenues for future research directed at testing new treatments in acute lung injury subpopulations defined according to lung mechanics. Promising new monitoring techniques may play a supporting role in the conduct of these studies. Finally, evidence from the neonatal literature recently has shown how the course and future consequences of respiratory failure in this population may be modified through more widespread use of noninvasive support.

Electrical activity of the diaphragm during extubation readiness testing in critically ill children.

OBJECTIVES: To investigate the electrical activity of the diaphragm during extubation readiness testing. DESIGN: Prospective observational trial. SETTING: A 29-bed medical-surgical pediatric intensive care unit. PATIENTS: Mechanically ventilated children between 1 month and 18 yrs of age. INTERVENTIONS: Twenty patients underwent a standardized extubation readiness test using a minimal pressure support ventilation strategy. A size-appropriate multiple-array esophageal electrode (electrical diaphragmatic activity catheter), which doubled as a feeding tube, was inserted. The electrical diaphragmatic activity, ventilatory parameters, and spirometry measurements were recorded with the Servo-i ventilator (Maquet, Solna, Sweden). Measurements were obtained before the extubation readiness test and 1 hr into the extubation readiness test. MEASUREMENTS AND MAIN RESULTS: During extubation readiness testing, the ratio of tidal volume to delta electrical diaphragmatic activity was significantly lower in those patients who passed the extubation readiness test compared to those who failed the extubation readiness test (extubation readiness test, pass: 24.8 ± 20.9 mL/µV vs. extubation readiness test, fail: 67.2 ± 27 mL/µV, respectively; p = .02). Delta electrical diaphragmatic activity correlated significantly with neuromuscular drive assessed by airway opening pressure at 0.1 secs (before extubation readiness test: r = .591, p < .001; during extubation readiness test: r = .682, p < .001). Eight out of 20 patients had ventilator dys-synchrony identified with electrical diaphragmatic activity during extubation readiness testing. CONCLUSIONS: Patients who generate higher diaphragmatic activity in relation to tidal volume may have better preserved diaphragmatic function and a better chance of passing the extubation readiness test as opposed to patients who generate lower diaphragmatic activity in relation to tidal volume, indicating diaphragmatic weakness. Electrical activity of the diaphragm also may be a useful adjunct to assess neuromuscular drive in ventilated children.

Electrocardiographic guidance for the placement of gastric feeding tubes: a pediatric case series.

BACKGROUND: The placement of nasal or oral gastric tubes is one of the most frequently performed procedures in critically ill children; tube malposition, particularly in the trachea, is an important complication. Neurally adjusted ventilatory assist (NAVA) ventilation (available only on the Servo-i ventilator, Maquet Critical Care, Solna, Sweden) requires a proprietary-design catheter (Maquet Critical Care, Solna, Sweden) with embedded electrodes that detect the electrical activity of the diaphragm (EA(di)). The EA(di) catheter has the potential benefit of confirming proper positioning of a gastric catheter, based on and the EA(di) waveforms. METHODS: In a case series study, our multidisciplinary team used EA(di) guidance for immediate, real-time confirmation of proper nasal or oral gastric tube placement in 20 mechanically ventilated pediatric patients who underwent 23 oral or nasal gastric tube placements. The catheters were placed with our standard practice, with the addition of a team member monitoring the EA(di) waveforms. As the tube passes down the esophagus and posterior to the heart, a characteristic EA(di) pattern is identified and the position of the atrial signal confirms correct placement of the gastric tube. If the EA(di) waveforms indicate incorrect placement, the tube is repositioned until the proper EA(di) waveform pattern is obtained. Then proper tube placement is reconfirmed via auscultation over the stomach while air is injected into the catheter, checking the pH of fluid suctioned from the catheter (gastric pH indicates correct positioning), and/or radiograph. RESULTS: The group's median age was 3 years (range 4 d to 16 y). All 20 patients had successful gastric catheter placement. The EA(di) catheter provided characteristic patterns for correctly placed tubes, tubes malpositioned above or below the gastroesophageal junction, and curled tubes. Proper catheter position was confirmed via radiograph and/or gastric pH in all 20 patients. CONCLUSIONS: EA(di) guidance helps confirm proper gastric catheter position, is equivalent to our standard practice for confirming gastric catheter placement, and may reduce the need for radiographs and improve patient safety by avoiding catheter malpositions.

Regional lung volume changes during high-frequency oscillatory ventilation.

OBJECTIVE: To investigate regional lung volume changes occurring during an inflation-deflation maneuver using high-frequency oscillatory ventilation. DESIGN: Prospective animal trial. SETTING: Animal research laboratory. SUBJECTS: Six Yorkshire swine. INTERVENTIONS: Electrical impedance tomography was used to quantify regional ventilation during high-frequency oscillatory ventilation. The electrical impedance tomography-derived center of ventilation was used to describe the distribution of regional ventilation, whereas spectral analysis was used to describe regional ventilation-induced impedance changes. Lung injury was induced using surfactant lavage. Animals were transitioned to high-frequency oscillatory ventilation and a slow inflation-deflation maneuver was performed by changing mean airway pressure by 5 cm H2O every 15 mins to a maximum mean airway pressure of 40 cm H2O. MEASUREMENTS AND MAIN RESULTS: The induction of lung injury was associated with a significant shift of the center of ventilation toward nondependent areas and an increase in shunt fraction (p < .001). During the following inflation-deflation maneuver using high-frequency oscillatory ventilation, inflation was associated with a shift of the center of ventilation from nondependent to dependent areas. Center of ventilation was significantly correlated with the shunt fraction (p < .001). Analyzing different lung layers along the gravitational axis separately, nondependent lung areas showed significantly decreased regional ventilation-induced impedance changes at higher pressures, suggesting overdistension, whereas dependent lung areas showed increased impedance changes, suggesting recruitment. The reverse was observed during deflation (all p < .05). CONCLUSIONS: The center of ventilation during high-frequency oscillatory ventilation correlated with oxygenating efficiency as measured by the shunt fraction. Lung recruitment during high-frequency oscillatory ventilation produced a significant shift of regional ventilation toward dependent areas of the lung and led to overdistension of nondependent areas.

Respiratory distress associated with inadequate mechanical ventilator flow response in a neonate with congenital diaphragmatic hernia.

The incidence of congenital diaphragmatic hernia has been reported as 0.17-0.66 per 1,000 births. Despite advances in neonatal intensive care, congenital diaphragmatic hernia is associated with high mortality and morbidity. We report a neonate who was born with a left congenital diaphragmatic hernia and underwent surgical repair. The lack of ventilator flow response and flow cycling was identified via interpretation of the ventilator graphic and clinical assessment. Presumably, the ventilator failed to respond to the patient's peak inspiratory flow demand, despite the clinician's setting the highest peak flow available. A time-cycled pressure-limited mode with adjustable peak flow rate was the only option that met the infant's flow requirement, and alleviated the respiratory distress. This clinical finding follows bench research that raises the concern that so called "cradle-to-grave" ventilators may not optimally support all neonates.

Distribution of Ventilation Measured by Electrical Impedance Tomography in Critically Ill Children.

BACKGROUND: Electrical impedance tomography (EIT) is a noninvasive, portable lung imaging technique that provides functional distribution of ventilation. We aimed to describe the relationship between the distribution of ventilation by mode of ventilation and level of oxygenation impairment in children who are critically ill. We also aimed to describe the safety of EIT application. METHODS: A prospective observational study of EIT images obtained from subjects in the pediatric ICU. Images were categorized by whether the subjects were on intermittent mandatory ventilation (IMV), continuous spontaneous ventilation, or no positive-pressure ventilation. Images were categorized by the level of oxygenation impairment when using [Formula: see text]/[Formula: see text]. Distribution of ventilation is described by the center of ventilation. RESULTS: Sixty-four images were obtained from 25 subjects. Forty-two images obtained during IMV with a mean ± SD center of ventilation of 55 ± 6%, 14 images during continuous spontaneous ventilation with a mean ± SD center of ventilation of 48.1 ± 11%, and 8 images during no positive-pressure ventilation with a mean ± SD center of ventilation of 47.5 ± 10%. Seventeen images obtained from subjects with moderate oxygenation impairment with a mean ± SD center of ventilation of 59.3 ± 1.9%, 12 with mild oxygenation impairment with a mean ± SD center of ventilation of 52.6 ± 2.3%, and 4 without oxygenation impairment with a mean ± SD center of ventilation of 48.3 ± 4%. There was more ventral distribution of ventilation with IMV versus continuous spontaneous ventilation (P = .009), with IMV versus no positive-pressure ventilation (P = .01) cohorts, and with moderate oxygenation impairment versus cohorts without oxygenation impairment (P = .009). There were no adverse events related to the placement and use of EIT in our study. CONCLUSIONS: Children who had worse oxygen impairment or who received controlled modes of ventilation had more ventral distribution of ventilation than those without oxygen impairment or the subjects who were spontaneously breathing. The ability of EIT to detect changes in the distribution of ventilation in real time may allow for distribution-targeted mechanical ventilation strategies to be deployed proactively; however, future studies are needed to determine the effectiveness of such a strategy.

Noninvasive Ventilation Is Interrupted Frequently and Mostly Used at Night in the Pediatric Intensive Care Unit.

BACKGROUND: Noninvasive ventilation (NIV) is commonly used to support children with respiratory failure, but detailed patterns of real-world use are lacking. The aim of our study was to describe use patterns of NIV via electronic medical record (EMR) data. METHODS: We performed a retrospective electronic chart review in a tertiary care pediatric ICU in the United States. Subjects admitted to the pediatric ICU from 2014 to 2017 who were mechanically ventilated were included in the study. RESULTS: The median number of discrete device episodes, defined as a time on support without interruption, was 20 (interquartile range [IQR] 8-49) per subject. The median duration of bi-level positive airway pressure (BPAP) support prior to interruption was 6.3 h (IQR 2.4-10.4); the median duration of CPAP was 6 h (IQR 2.1-10.4). Interruptions to BPAP had a median duration of 6.3 h (IQR 2-15.5); interruptions to CPAP had a median duration of 8.6 h (IQR 2.2-16.8). Use of NIV followed a diurnal pattern, with 44% of BPAP and 42% of CPAP subjects initiating support between 7:00 pm and midnight, and 49% of BPAP and 46% of CPAP subjects stopping support between 5:00 am and 10:00 am. CONCLUSIONS: NIV was frequently interrupted, and initiation and discontinuation of NIV follows a diurnal pattern. Use of EMR data collected for routine clinical care allowed the analysis of granular details of typical use patterns. Understanding NIV use patterns may be particularly important to understanding the burden of pediatric ICU bed utilization for nocturnal NIV. To our knowledge, this is the first study to examine in detail the use of pediatric NIV and to define diurnal use and frequent interruptions to support.

Adding Continuous Vital Sign Information to Static Clinical Data Improves the Prediction of Length of Stay After Intubation: A Data-Driven Machine Learning Approach.

BACKGROUND: Bedside monitors in the ICU routinely measure and collect patients' physiologic data in real time to continuously assess the health status of patients who are critically ill. With the advent of increased computational power and the ability to store and rapidly process big data sets in recent years, these physiologic data show promise in identifying specific outcomes and/or events during patients' ICU hospitalization. METHODS: We introduced a methodology designed to automatically extract information from continuous-in-time vital sign data collected from bedside monitors to predict if a patient will experience a prolonged stay (length of stay) on mechanical ventilation, defined as >4 d, in a pediatric ICU. RESULTS: Continuous-in-time vital signs information and clinical history data were retrospectively collected for 284 ICU subjects from their first 24 h on mechanical ventilation from a medical-surgical pediatric ICU at Boston Children's Hospital. Multiple machine learning models were trained on multiple subsets of these subjects to predict the likelihood that each of these subjects would experience a long stay. We evaluated the predictive power of our models strictly on unseen hold-out validation sets of subjects. Our methodology achieved model performance of >83% (area under the curve) by using only vital sign information as input, and performances of 90% (area under the curve) by combining vital sign information with subjects' static clinical data readily available in electronic health records. We implemented this approach on 300 independently trained experiments with different choices of training and hold-out validation sets to ensure the consistency and robustness of our results in our study sample. The predictive power of our approach outperformed recent efforts that used deep learning to predict a similar task. CONCLUSIONS: Our proposed workflow may prove useful in the design of scalable approaches for real-time predictive systems in ICU environments, exploiting real-time vital sign information from bedside monitors. (ClinicalTrials.gov registration NCT02184208.).

Automated measurement of the lower inflection point in a pediatric lung model.

OBJECTIVE: To determine which flow setting most accurately detects the lower inflection point (Pflex) using an automated constant flow method and varying endotracheal tube (ETT) sizes with and without an airleak in a pediatric lung model. DESIGN: Interventional laboratory study. SETTING: Children's hospital research center. INTERVENTIONS: A pediatric lung model was created with Pflexs of the inspiratory pressure-volume (P-V) curve set at 5 and 10 cm H2O using the ASL 5000 Test Lung (IngMar Medical, Pittsburgh, PA). Three ETT sizes (3.0, 4.0, 5.0 mm) were tested with and without a 25% airleak. P-V curves were obtained using an automated constant flow method at ten different flow rates. MEASUREMENTS AND MAIN RESULTS: Without an ETT airleak, the lowest flow of 0.5 L/min led to the most accurate determination of Pflex regardless of ETT size or set Pflex (p < 0.001). When a 25% leak was introduced, accuracy of measured Pflex depended on both ETT size (p < 0.001) and flow rate (p < 0.001). Optimum flow rates for Pflex determination were 0.5, 1.0, and 1.5 L/min at Pflex of 5 cm H2O, and 2.0, 3.5, and 4.5 L/min at 10 cm H2O for 3.0, 4.0, and 5.0 mm ETTs, respectively (p < 0.001). CONCLUSIONS: Estimation of Pflex can be achieved using automated P-V curves with ETTs appropriate for pediatric use, with and without an airleak. ETT size and flow rate affect the accuracy of these measurements when an airleak is present, and use of increased flow rates to create the automated P-V curves can reduce error. These data support the idea that a low-flow technique provides the most accurate determination of Pflex in pediatric patients without a leak around their ETT, whereas increased flows are needed to compensate when an ETT airleak is present.

Differences in regional pulmonary pressure-impedance curves before and after lung injury assessed with a novel algorithm.

Global pressure-volume (PV) curves are an adjunct measure to describe lung characteristics in patients with acute respiratory distress syndrome (ARDS). There is convincing evidence that high peak inspiratory pressures (PIP) cause barotrauma, while optimized positive end-expiratory pressure (PEEP) helps avoid mechanical injury to the lungs by preventing repeated alveolar opening and closing. The optimal values of PIP and PEEP are deduced from the shape of the PV curve by the identification of so-called lower and upper inflection points. However, it has been demonstrated using electrical impedance tomography (EIT) that the inflection points vary across the lung. This study employs a simple curve-fitting technique to automatically define inflection points on both pressure-volume (PV) and pressure-impedance (PI) curves to asses the differences between global PV and regional PI estimates in animals before and after induced lung injury. The results demonstrate a clear increase in lower inflection point (LIP) along the gravitational axis both before and after lung injury. Moreover, it is clear from comparison of the local EIT-derived LIPs with those derived from global PV curves that a ventilation strategy based on the PV curve alone may leave dependent areas of the lung collapsed. EIT-based PI curve analysis may help choosing an optimal ventilation strategy.

GREIT: a unified approach to 2D linear EIT reconstruction of lung images.

Electrical impedance tomography (EIT) is an attractive method for clinically monitoring patients during mechanical ventilation, because it can provide a non-invasive continuous image of pulmonary impedance which indicates the distribution of ventilation. However, most clinical and physiological research in lung EIT is done using older and proprietary algorithms; this is an obstacle to interpretation of EIT images because the reconstructed images are not well characterized. To address this issue, we develop a consensus linear reconstruction algorithm for lung EIT, called GREIT (Graz consensus Reconstruction algorithm for EIT). This paper describes the unified approach to linear image reconstruction developed for GREIT. The framework for the linear reconstruction algorithm consists of (1) detailed finite element models of a representative adult and neonatal thorax, (2) consensus on the performance figures of merit for EIT image reconstruction and (3) a systematic approach to optimize a linear reconstruction matrix to desired performance measures. Consensus figures of merit, in order of importance, are (a) uniform amplitude response, (b) small and uniform position error, (c) small ringing artefacts, (d) uniform resolution, (e) limited shape deformation and (f) high resolution. Such figures of merit must be attained while maintaining small noise amplification and small sensitivity to electrode and boundary movement. This approach represents the consensus of a large and representative group of experts in EIT algorithm design and clinical applications for pulmonary monitoring. All software and data to implement and test the algorithm have been made available under an open source license which allows free research and commercial use.