Ventilator Weaning and Terminal Extubation: Withdrawal of Life-Sustaining Therapy in Children. Secondary Analysis of the Death One Hour After Terminal Extubation Study.

OBJECTIVE: Terminal extubation (TE) and terminal weaning (TW) during withdrawal of life-sustaining therapies (WLSTs) have been described and defined in adults. The recent Death One Hour After Terminal Extubation study aimed to validate a model developed to predict whether a child would die within 1 hour after discontinuation of mechanical ventilation for WLST. Although TW has not been described in children, pre-extubation weaning has been known to occur before WLST, though to what extent is unknown. In this preplanned secondary analysis, we aim to describe/define TE and pre-extubation weaning (PW) in children and compare characteristics of patients who had ventilatory support decreased before WLST with those who did not. DESIGN: Secondary analysis of multicenter retrospective cohort study. SETTING: Ten PICUs in the United States between 2009 and 2021. PATIENTS: Nine hundred thirteen patients 0-21 years old who died after WLST. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: 71.4% ( n = 652) had TE without decrease in ventilatory support in the 6 hours prior. TE without decrease in ventilatory support in the 6 hours prior = 71.4% ( n = 652) of our sample. Clinically relevant decrease in ventilatory support before WLST = 11% ( n = 100), and 17.6% ( n = 161) had likely incidental decrease in ventilatory support before WLST. Relevant ventilator parameters decreased were F io2 and/or ventilator set rates. There were no significant differences in any of the other evaluated patient characteristics between groups (weight, body mass index, unit type, primary diagnostic category, presence of coma, time to death after WLST, analgosedative requirements, postextubation respiratory support modality). CONCLUSIONS: Decreasing ventilatory support before WLST with extubation in children does occur. This practice was not associated with significant differences in palliative analgosedation doses or time to death after extubation.

Effort and work-of-breathing parameters strongly correlate with increased resistance in an animal model.

BACKGROUND: Effort of Breathing (EOB) calculations may be a reliable alternative to Work of Breathing (WOB) calculations in which Respiratory Inductance Plethysmography (RIP) replaces spirometry. We sought to compare EOB and WOB measurements in a nonhuman primate model of increasing extrathoracic inspiratory resistance simulating upper airway obstruction (UAO). METHODS: RIP, spirometry, and esophageal manometry were measured in spontaneously breathing, intubated Rhesus monkeys utilizing 11 calibrated resistors randomly applied for 2-min. EOB was calculated breath-by-breath as Pressure Rate Product (PRP) and Pressure Time Product (PTP). WOB was calculated from the Pressure-Volume curve based on spirometry (WOBSPIR) or RIP flow (WOBRIP). RESULTS: WOB, PRP and PTP showed similar linear increases when exposed to higher levels of resistive loads. When comparing WOBSPIR to WOBRIP, a similar strong correlation was seen for both signals as resistance increased and there were no statistically significant differences. CONCLUSION: EOB and WOB parameters utilizing esophageal manometry and RIP, independent of spirometry, showed a strong correlation as a function of increasing inspiratory resistance in nonhuman primates. This allows several potential monitoring possibilities for non-invasively ventilated patients or situations where spirometry is not available. IMPACT: EOB and WOB parameters showed a strong correlation as a function of increasing inspiratory resistance in nonhuman primates. There was a strong correlation between spirometry-based WOB versus RIP-based WOB. To date, it has remained untested as to whether EOB is a reliable alternative for WOB and if RIP can replace spirometry in these measurements. Our results enable additional potential monitoring possibilities for non-invasively ventilated patients or situations where spirometry is not available. Where spirometry is not available, there is no need to apply a facemask post extubation to a spontaneously breathing, non-intubated infant to make objective EOB measurements.

Subglottic Post-Extubation Upper Airway Obstruction Is Associated With Long-Term Airway Morbidity in Children.

OBJECTIVES: Post-extubation upper airway obstruction is the most common cause of extubation failure in children, but there are few data regarding long-term morbidity. We aim to describe the frequency of long-term airway sequelae in intubated children and determine the association with post-extubation upper airway obstruction. DESIGN: Retrospective, post hoc analysis of previously identified prospective cohort of children in the pediatric/cardiothoracic ICU at Children's Hospital Los Angeles from July 2012 to April 2015. A single provider blinded to the upper airway obstruction classification reviewed the electronic medical records of all patients in the parent study, before and after the index extubation (extubation during parent study), to identify pre-index and post-index upper airway disease. Primary outcomes were prevalence of newly diagnosed airway anomalies following index extubation. SETTING: Single center, tertiary, 391-bed children's hospital. PATIENTS: From the parent study, 327 children younger than 18 years (intubated for at least 12 hr) were included if they received subsequent care (regardless of specialty) after the index extubation. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: New airway anomalies were identified in 40 of 327 children (12.2%). Patients labeled with subglottic upper airway obstruction at the index extubation were more likely to be diagnosed with new airway anomalies on subsequent follow-up, receive long-term Otolaryngology follow-up, or receive airway surgery (all p ≤ 0.006). In multivariable modeling, upper airway obstruction as the primary reason for initial intubation (odds ratio, 3.71; CI, 1.50-9.19), reintubation during the index ICU admission (odds ratio, 4.44; CI, 1.67-11.80), pre-index airway anomaly (odds ratio, 3.31; CI, 1.36-8.01), and post-extubation subglottic upper airway obstruction (odds ratio, 3.50; CI, 1.46-8.34) remained independently associated with the diagnosis of new airway anomalies. CONCLUSIONS: Post-extubation subglottic upper airway obstruction is associated with a three-fold greater odds of long-term airway morbidity. These patients may represent an at-risk population that should be monitored closely after leaving the ICU.

Machine Learning to Predict Cardiac Death Within 1 Hour After Terminal Extubation.

OBJECTIVES: Accurate prediction of time to death after withdrawal of life-sustaining therapies may improve counseling for families and help identify candidates for organ donation after cardiac death. The study objectives were to: 1) train a long short-term memory model to predict cardiac death within 1 hour after terminal extubation, 2) calculate the positive predictive value of the model and the number needed to alert among potential organ donors, and 3) examine associations between time to cardiac death and the patient's characteristics and physiologic variables using Cox regression. DESIGN: Retrospective cohort study. SETTING: PICU and cardiothoracic ICU in a tertiary-care academic children's hospital. PATIENTS: Patients 0-21 years old who died after terminal extubation from 2011 to 2018 (n = 237). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The median time to death for the cohort was 0.3 hours after terminal extubation (interquartile range, 0.16-1.6 hr); 70% of patients died within 1 hour. The long short-term memory model had an area under the receiver operating characteristic curve of 0.85 and a positive predictive value of 0.81 at a sensitivity of 94% when predicting death within 1 hour of terminal extubation. About 39% of patients who died within 1 hour met organ procurement and transplantation network criteria for liver and kidney donors. The long short-term memory identified 93% of potential organ donors with a number needed to alert of 1.08, meaning that 13 of 14 prepared operating rooms would have yielded a viable organ. A Cox proportional hazard model identified independent predictors of shorter time to death including low Glasgow Coma Score, high Pao2-to-Fio2 ratio, low-pulse oximetry, and low serum bicarbonate. CONCLUSIONS: Our long short-term memory model accurately predicted whether a child will die within 1 hour of terminal extubation and may improve counseling for families. Our model can identify potential candidates for donation after cardiac death while minimizing unnecessarily prepared operating rooms.

Thresholds for oximetry alarms and target range in the NICU: an observational assessment based on likely oxygen tension and maturity.

BACKGROUND: Continuous monitoring of SpO2 in the neonatal ICU is the standard of care. Changes in SpO2 exposure have been shown to markedly impact outcome, but limiting extreme episodes is an arduous task. Much more complicated than setting alarm policy, it is fraught with balancing alarm fatigue and compliance. Information on optimum strategies is limited. METHODS: This is a retrospective observational study intended to describe the relative chance of normoxemia, and risks of hypoxemia and hyperoxemia at relevant SpO2 levels in the neonatal ICU. The data, paired SpO2-PaO2 and post-menstrual age, are from a single tertiary care unit. They reflect all infants receiving supplemental oxygen and mechanical ventilation during a 3-year period. The primary measures were the chance of normoxemia (PaO2 50-80 mmHg), risks of severe hypoxemia (PaO2 ≤ 40 mmHg), and of severe hyperoxemia (PaO2 ≥ 100 mmHg) at relevant SpO2 levels. RESULTS: Neonates were categorized by postmenstrual age: < 33 (n = 155), 33-36 (n = 192) and > 36 (n = 1031) weeks. From these infants, 26,162 SpO2-PaO2 pairs were evaluated. The post-menstrual weeks (median and IQR) of the three groups were: 26 (24-28) n = 2603; 34 (33-35) n = 2501; and 38 (37-39) n = 21,058. The chance of normoxemia (65, 95%-CI 64-67%) was similar across the SpO2 range of 88-95%, and independent of PMA. The increasing risk of severe hypoxemia became marked at a SpO2 of 85% (25, 95%-CI 21-29%), and was independent of PMA. The risk of severe hyperoxemia was dependent on PMA. For infants < 33 weeks it was marked at 98% SpO2 (25, 95%-CI 18-33%), for infants 33-36 weeks at 97% SpO2 (24, 95%-CI 14-25%) and for those > 36 weeks at 96% SpO2 (20, 95%-CI 17-22%). CONCLUSIONS: The risk of hyperoxemia and hypoxemia increases exponentially as SpO2 moves towards extremes. Postmenstrual age influences the threshold at which the risk of hyperoxemia became pronounced, but not the thresholds of hypoxemia or normoxemia. The thresholds at which a marked change in the risk of hyperoxemia and hypoxemia occur can be used to guide the setting of alarm thresholds. Optimal management of neonatal oxygen saturation must take into account concerns of alarm fatigue, staffing levels, and FiO2 titration practices.

Impact of Anesthetic and Ventilation Strategies on Invasive Hemodynamic Measurements in Pediatric Heart Transplant Recipients.

BACKGROUND: Care of pediatric heart transplant recipients relies upon serial invasive hemodynamic evaluation, generally performed under the artificial conditions created by anesthesia and supportive ventilation. OBJECTIVES: This study aimed to evaluate the hemodynamic impacts of different anesthetic and ventilatory strategies. METHODS: We compared retrospectively the cardiac index, right- and left-sided filling pressures, and pulmonary and systemic vascular resistances of all clinically well and rejection-free heart transplant recipients catheterized from 2005 through 2017. Effects of spontaneous versus positive pressure ventilation and of sedation versus general anesthesia were tested with generalized linear mixed models for repeated measures using robust sandwich estimators of the covariance matrices. Least squared means showed adjusted mean outcome values, controlled for appropriate confounders. RESULTS: 720 catheterizations from 101 recipients met inclusion criteria. Adjusted cardiac index was 3.14 L/min/m2 (95% CI 3.01-3.67) among spontaneously breathing and 2.71 L/min/m2 (95% CI 2.56-2.86) among ventilated recipients (p < 0.0001). With spontaneous breathing, left filling pressures were lower (9.9 vs 11.0 mmHg, p = 0.030) and systemic vascular resistances were higher (24.0 vs 20.5 Woods units, p < 0.0001). After isolating sedated from anesthetized spontaneously breathing patients, the observed differences in filling pressures and resistances emerged as a function of sedation versus general anesthesia rather than of spontaneous versus positive pressure ventilation. CONCLUSION: In pediatric heart transplant recipients, positive pressure ventilation reduces cardiac output but does not alter filling pressures or vascular resistances. Moderate sedation yields lower left filling pressures and higher systemic vascular resistances than does general anesthesia. Differences are quantitatively small.

Body Habitus and Risk of Mortality in Pediatric Sepsis and Septic Shock: A Retrospective Cohort Study.

OBJECTIVE: To investigate the association between body habitus and mortality in critically ill children with sepsis or septic shock. STUDY DESIGN: This was a retrospective cohort study of prospectively collected data of children admitted to US pediatric intensive care units (PICUs) with a primary or secondary diagnosis of sepsis or septic shock. We separated body habitus into underweight, normal weight, overweight, and obese. Outcomes were mortality (primary), treatment with invasive mechanical ventilation (secondary), and time to PICU discharge for survivors (secondary). Multivariable analyses using mixed-effects logistic regression and shared frailty models clustered by unit and adjusted for confounding variables were used to assess the association between body habitus and outcomes. RESULTS: There were 7038 children with sepsis or septic shock. Mortality was 10.1% (n = 714) and 52.9% (n = 3720) required invasive mechanical ventilation. Body habitus was not associated with mortality after controlling for hospital level effects and confounding variables. Children who were overweight and obese had greater odds of invasive mechanical ventilation (overweight OR 1.23 [95% CI 1.05-1.45], P = .011 and obese OR 1.57 [95% CI 1.37-1.80], P < .001) compared with children of normal weight. In survivors treated with invasive mechanical ventilation, children who were obese had a longer time to PICU discharge than children of normal weight (obese hazard ratio for discharge 0.84 [95% CI, 0.77-0.92], P < .0001). CONCLUSIONS: There was no association between body habitus and mortality in critically ill children with sepsis. Children who were overweight and obese were more likely to receive invasive mechanical ventilation and mechanically ventilated survivors who were obsese had a longer time to PICU discharge.

Evaluating the Practice of Repositioning Endotracheal Tubes in Neonates and Children Based on Radiographic Location.

OBJECTIVES: Chest radiographs are commonly performed in the ICU setting to confirm the position of the endotracheal tube. The purpose of this study was to evaluate the practice and accuracy of repositioning endotracheal tubes in the pediatric population based on chest radiograph. DESIGN: Retrospective review of patient's medical record and chest radiograph. SETTING: Single-institution, academic children's hospital. PATIENTS: PICU and cardiothoracic ICU patients who had repositioning of their endotracheal tube from September 1, 2016, to September 1, 2017. MEASUREMENTS AND MAIN RESULTS: Chest radiograph before and after endotracheal tube repositioning were examined measuring the distance from the endotracheal tube tip to carina. A total of 183 endotracheal tube repositionings were assessed. Twenty-nine percent of endotracheal tube repositionings resulted in a persistently malpositioned endotracheal tube, requiring another intervention. For intended endotracheal tube repositioning of ± 2.0 cm, the actual change measured compared to intended adjustment was a median of 0.7 cm (interquartile range, 0.35-1.1 cm). For intended ± 1.5 cm, the median difference was 0.4 cm (interquartile range, 0.16-0.90 cm). For intended ± 1.0 cm, the median difference was 0.5 cm (interquartile range, 0.20-0.90 cm). For intended ± 0.5 cm, the median difference was 0.3 cm (interquartile range, 0.2-0.88 cm). When the head was malpositioned the difference from intended endotracheal tube repositioning to actual was median 0.70 cm (interquartile range, 0.40-1.1 cm), this was significantly higher than when the head was in a good position CONCLUSIONS:: When repositioning endotracheal tubes based on chest radiograph, there is a significant difference between intended and actual adjustment with great variability. Avoiding very small repositionings (± 0.5 cm) and standardizing head position prior to daily chest radiograph may reduce these errors.

Intraoperative Hypothermia is Common, but not Associated With Blood Loss or Transfusion in Pediatric Posterior Spinal Fusion.

BACKGROUND: Intraoperative hypothermia may be associated with increased blood loss due to the effects of temperature on clotting but this has not been evaluated in the setting of pediatric posterior spinal fusion (PSF). The purpose of this study was to determine if a correlation exists between intraoperative hypothermia and estimated blood loss (EBL) or transfusion requirements in pediatric patients undergoing PSF. METHODS: A retrospective review of consecutive patients undergoing PSF for scoliosis at a single institution between 6/2004 and 3/2012 was performed. Exclusion criteria were fewer than 10 levels fused, anterior spinal fusion, and patients below 9 years old at time of surgery. Temperature was measured every 15 seconds using esophageal temperature probe. Input variable of hypothermia was analyzed as a binary variable Tmin ≤35°C at any point during anesthesia and as integrated temperature area under the curve (TAUC). RESULTS: A total of 510 with an average age of 14.6 years (range, 9.0 to 24.3 y) met inclusion criteria. Totally, 56% (287/510) had idiopathic scoliosis (IS) and 44% (223/510) were non-IS. Hypothermia (Tmin≤35°C) was experienced by 45% (230/510) of all patients [48% (137/287) of IS; 42% (93/223) of non-IS]. A total of 63% (323/510) of patients were transfused with packed red blood cells (PRBC) [49% (141/287) of IS patients; 82% (182/223) of non-IS patients]. There was no correlation between Tmin≤35°C and transfusion of PRBC in all included patients (P=0.49); (IS patients P=0.45, non-IS patients P=0.61). There was no significant difference in EBL between patients who experienced hypothermia and those who did not (P=0.33; IS patients P=0.21, non-IS patients P=0.87). There was no significant correlation between TAUC and transfusion of PRBC for all patients (P=0.35), IS patients (P=0.26) and non-IS patients (P=0.54) or between TAUC and EBL (P=0.80); (IS patients P=0.57. non-IS patients P=0.62). CONCLUSIONS: There was no significant correlation between intraoperative hypothermia and EBL or transfusion of PRBC in pediatric patients undergoing PSF. LEVEL OF EVIDENCE: Level III.

Comparison of Effort of Breathing for Infants on Nasal Modes of Respiratory Support.

OBJECTIVE: To directly compare effort of breathing between high flow nasal cannula (HFNC), nasal intermittent mechanical ventilation (NIMV), and nasal continuous positive airway pressure (NCPAP). STUDY DESIGN: This was a single center prospective cross-over study for patients <6 months in the cardiothoracic or pediatric intensive care unit receiving nasal noninvasive respiratory support after extubation. We measured effort of breathing using esophageal manometry with pressure-rate product (PRP) on all 3 modes. NIMV synchrony was determined by comparing patient efforts (esophageal manometry) with mechanically delivered breaths (spirometry in ventilator circuit). On NIMV, PRP and synchrony was also measured after adding a nasal clip on 26 patients. RESULTS: Forty-two children were included. Median (IQR) age was 2 (0.5, 4) months. There was no difference in median PRP between HFNC 6 liters per minute, 355 (270,550), NIMV 12/5 cm H2O, 341 (235, 472), and NCPAP 5 cm H2O, 340 (245,506) (P?=?.33). Results were similar regardless of HFNC flow rate or NIMV inspiratory pressure. Median PRP on CPAP of 5 cm H2O prior to extubation 255 (176, 375) was significantly lower than all postextubation values (P??.07)). However, as NIMV synchrony improved (>60%), PRP on NIMV was lower than on HFNC. CONCLUSIONS: For infants, effort of breathing is similar on HFNC, NIMV, and NCPAP after extubation, regardless of flow rate or inspiratory pressure. We speculate that bi-level NIMV may be superior if high levels of synchrony can be achieved.

The Relationship between High Flow Nasal Cannula Flow Rate and Effort of Breathing in Children.

OBJECTIVE: To use an objective metric of effort of breathing to determine optimal high flow nasal cannula (HFNC) flow rates in children <3 years of age. STUDY DESIGN: Single-center prospective trial in a 24-bed pediatric intensive care unit of children <3 years of age on HFNC. We measured the percent change in pressure∙rate product (PRP) (an objective measure of effort of breathing) as a function of weight-indexed flow rates of 0.5, 1.0, 1.5, and 2.0 L/kg/minute. For a subgroup of patients, 2 different HFNC delivery systems (Fisher & Paykel [Auckland, New Zealand] and Vapotherm [Exeter, New Hampshire]) were compared. RESULTS: Twenty-one patients (49 titration episodes) were studied. The most common diagnoses were bronchiolitis and pneumonia. Overall, there was a significant difference in the percent change in PRP from baseline (of 0.5 L/kg/minute) with increasing flow rates for the entire cohort (P < .001) with largest change at 2.0 L/kg/min (-21%). Subgroup analyses showed no significant difference in percent change in PRP from baseline when comparing the 2 different HFNC delivery systems (P = .12). Patients ≤8 kg experienced a larger percent change in PRP as HFNC flow rates were increased (P = .001) than patients >8 kg. CONCLUSIONS: The optimal HFNC flow rate to reduce effort of breathing in infants and young children is approximately 1.5-2.0 L/kg/minute with more benefit seen in children ≤8 kg.

Volume and Pressure Delivery During Pediatric High-Frequency Oscillatory Ventilation.

OBJECTIVE: Identify variables independently associated with delivered tidal volume (VT) and measured mean airway pressure during high-frequency oscillatory ventilation across the range of pediatric endotracheal tube sizes. DESIGN: In vitro study. SETTING: Research laboratory. INTERVENTIONS: An in vitro bench model of the intubated pediatric respiratory system during high-frequency oscillatory ventilation was used to obtain delivered VT and mean airway pressure (in the distal lung) for various endotracheal tube sizes. Measurements were taken at different combinations of ventilator set mean airway pressure (Paw), amplitude (ΔP), frequency, and test lung compliance. Multiple regression analysis was used to construct multivariable models predicting delivered VT and mean airway pressure. MEASUREMENTS AND MAIN RESULTS: Variables independently associated with higher delivered VT for all endotracheal tube sizes include higher ΔP (p < 0.001), lower frequency (p < 0.001), and higher test lung compliance (p < 0.001). A multiplicative interaction between frequency and ΔP magnifies the delivered VT when ΔP is high and frequency is low (p < 0.001). Delivered mean airway pressure becomes lower than set Paw as ΔP increases (p < 0.001) and frequency increases (p < 0.05). Ventilator set Paw is the largest determinant of delivered mean airway pressure; however, increasing ΔP resulted in a lower delivered mean airway pressure. For example, in a 4.0 mm ID endotracheal tube, increasing ΔP by 10 cm H2O resulted in an average decrease of delivered mean airway pressure by 4.5%. CONCLUSIONS: This is the first study to quantify the interaction between ΔP and frequency in delivered VT and the effect of ΔP and frequency on delivered mean airway pressure. These results demonstrate the need to measure or estimate VT and delivered pressures during high-frequency oscillatory ventilation and may be useful in determining optimal strategies for lung protective ventilation during high-frequency oscillatory ventilation.

Change in Oxygen Consumption Following Inhalation of Albuterol in Comparison with Levalbuterol in Healthy Adult Volunteers.

BACKGROUND: Albuterol is the most commonly used ß agonist to treat reversible lower airway obstruction. Albuterol contains a racemic mixture of two enantiomers. Levalbuterol contains the single R form enantiomer. Levalbuterol is frequently prescribed to limit cardiovascular toxicity. OBJECTIVE: We examined changes in oxygen consumption (V'O2) and heart rate (HR) following administration of albuterol and levalbuterol. METHODS: This is a prospective, randomized, single-blinded, controlled study of healthy adult volunteers. Subjects separately received albuterol (5 mg) and levalbuterol (2.5 mg) aerosolized over 15 min. V'O2 and vital signs were measured before the medications and 5, 10, 20, 40, and 60 min after. RESULTS: We enrolled 24 volunteers with a median age of 32 years. Compared to baseline, there was a significant maximum increase in V'O2 following administration of both albuterol (median 17% (1, 3 IQR 9, 43%) p < 0.001) and levalbuterol (median 23% (1, 3 IQR 10, 32%) p < 0.001). There was no significant difference between the maximum increase in V'O2 following administration of albuterol compared to levalbuterol (p = 0.57). Compared to baseline, there was a significant maximal increase in HR with both albuterol (median 30% (1, 3 IQR 19, 43%) p < 0.001) and levalbuterol (median 23% (1, 3 IQR 19, 31%) p < 0.001). There was a statistically significant greater increase in maximal HR following administration of albuterol as compared to levalbuterol (p = 0.009). CONCLUSION: Albuterol and levalbuterol both cause a significant increase in V'O2 and HR. There was no significant difference between albuterol and levalbuterol regarding the maximum increase in V'O2. There was a statistically significant but likely clinically insignificant difference in maximum increase in HR in patients with adequate oxygen delivery when comparing albuterol to levalbuterol.

Evaluating Risk Factors for Pediatric Post-extubation Upper Airway Obstruction Using a Physiology-based Tool.

RATIONALE: Subglottic edema is the most common cause of pediatric extubation failure, but few studies have confirmed risk factors or prevention strategies. This may be due to subjective assessment of stridor or inability to differentiate supraglottic from subglottic disease. OBJECTIVES: Objective 1 was to assess the utility of calibrated respiratory inductance plethysmography (RIP) and esophageal manometry to identify clinically significant post-extubation upper airway obstruction (UAO) and differentiate subglottic from supraglottic UAO. Objective 2 was to identify risk factors for subglottic UAO, stratified by cuffed versus uncuffed endotracheal tubes (ETTs). METHODS: We conducted a single-center prospective study of children receiving mechanical ventilation. UAO was defined by inspiratory flow limitation (measured by RIP and esophageal manometry) and classified as subglottic or supraglottic based on airway maneuver response. Clinicians performed simultaneous blinded clinical UAO assessment at the bedside. MEASUREMENTS AND MAIN RESULTS: A total of 409 children were included, 98 of whom had post-extubation UAO and 49 (12%) of whom were subglottic. The reintubation rate was 34 (8.3%) of 409, with 14 (41%) of these 34 attributable to subglottic UAO. Five minutes after extubation, RIP and esophageal manometry better identified patients who subsequently received UAO treatment than clinical UAO assessment (P < 0.006). Risk factors independently associated with subglottic UAO included low cuff leak volume or high preextubation leak pressure, poor sedation, and preexisting UAO (P < 0.04) for cuffed ETTs; and age (range, 1 mo to 5 yr) for uncuffed ETTs (P < 0.04). For uncuffed ETTs, the presence or absence of preextubation leak was not associated with subglottic UAO. CONCLUSIONS: RIP and esophageal manometry can objectively identify subglottic UAO after extubation. Using this technique, preextubation leak pressures or cuff leak volumes predict subglottic UAO in children, but only if the ETT is cuffed.

Validation of an Ultrasound Cardiac Output Monitor as a Bedside Tool for Pediatric Patients.

The aim of our study was to determine the validity of cardiac output (CO) measurements taken with the ultrasonic cardiac output monitor (USCOM) by comparing to CO measured by pulmonary arterial catheter (PAC) thermodilution during cardiac catheterization. We enrolled thirty-one children (<18 years) undergoing cardiac catheterization in this double-blinded, prospective, observational study. The median CO measured by USCOM was 4.37 L/min (IQR 3.73, 5.60 L/min) compared to 4.28 L/min (IQR 3.52, 5.26 L/min) by PAC thermodilution. The bias (mean difference) between the two methods was 0.2 L/min, and the 95% limits of agreement were -1.2 to 1.6 L/min. The mean percentage error of CO between USCOM and PAC thermodilution was 11%. When excluding a sole outlier, the bias between the two measures decreased to 0.1 L/min (95% limits of agreement -0.6 to 0.9 L/min), and the percentage error was reduced to 8%. The median SVRI measured by USCOM was 22.0 Wood Units (IQR 17.0, 26.8 Wood Units) compared to 22.1 Wood Units (IQR 17.6, 27.4 Wood Units) by PAC thermodilution. Bias (mean difference) between the two methods was -0.6 Wood Units, and the 95% limits of agreement were -8.2 to 6.9 Wood Units. We found that the estimation of CO and by extension SVRI with USCOM is reliable against pulmonary artery catheter thermodilution in children with normal cardiac anatomy. Given the noninvasive nature of USCOM, speed of measurement, and relative ease of use, it may be useful as a bedside tool for pediatric patients.

Fever is common postoperatively following posterior spinal fusion: infection is an uncommon cause.

OBJECTIVE: To determine the frequency and clinical significance of postoperative fever in pediatric patients undergoing posterior spinal fusion (PSF). STUDY DESIGN: A retrospective chart review was performed for consecutive patients undergoing PSF at a single institution between June 2005 and April 2011, with a minimum of 2-year follow up. Exclusion criteria were previous spine surgery, a combined anterior-posterior approach, and delayed wound closure at the time of surgery. RESULTS: Two hundred and seventy-eight patients with an average age of 13 years (1-22 years) met inclusion criteria, with the following diagnoses: adolescent idiopathic scoliosis 43%, neuromuscular/syndromic scoliosis 39%, congenital scoliosis 11%, spondylolisthesis 4%, and Scheuermann kyphosis 3%. Seventy-two percent (201/278) of patients had a maximum temperature (Tmax) >38(°) postoperatively, and 9% (27/278) Tmax >39(°). The percentage of febrile patients trended down following the first postoperative day. Infection rate was 4% (12/278). There was no correlation between Tmax >38(°) or Tmax >39(°), and timing of fever, positive blood or urine cultures, pneumonia, or surgical site infection. CONCLUSION: Seventy-two percent of pediatric patients undergoing PSF experienced postoperative fever, and 9% of patients had Tmax>39(°). There was no significant correlation between fever and positive blood culture, urine culture, pneumonia, or surgical site infection. This information may help relieve stress for families and healthcare providers, and obviate routine laboratory evaluation for fever alone.

Respiratory inductance plethysmography calibration for pediatric upper airway obstruction: an animal model.

BACKGROUND: We sought to determine optimal methods of respiratory inductance plethysmography (RIP) flow calibration for application to pediatric postextubation upper airway obstruction. METHODS: We measured RIP, spirometry, and esophageal manometry in spontaneously breathing, intubated Rhesus monkeys with increasing inspiratory resistance. RIP calibration was based on: ΔµV(ao) ≈ M[ΔµV(RC) + K(ΔµV(AB))] where K establishes the relationship between the uncalibrated rib cage (ΔµV(RC)) and abdominal (ΔµV(AB)) RIP signals. We calculated K during (i) isovolume maneuvers during a negative inspiratory force (NIF), (ii) quantitative diagnostic calibration (QDC) during (a) tidal breathing, (b) continuous positive airway pressure (CPAP), and (c) increasing degrees of upper airway obstruction (UAO). We compared the calibrated RIP flow waveform to spirometry quantitatively and qualitatively. RESULTS: Isovolume calibrated RIP flow tracings were more accurate (against spirometry) both quantitatively and qualitatively than those from QDC (P < 0.0001), with bigger differences as UAO worsened. Isovolume calibration yielded nearly identical clinical interpretation of inspiratory flow limitation as spirometry. CONCLUSION: In an animal model of pediatric UAO, isovolume calibrated RIP flow tracings are accurate against spirometry. QDC during tidal breathing yields poor RIP flow calibration, particularly as UAO worsens. Routine use of a NIF maneuver before extubation affords the opportunity to use RIP to study postextubation UAO in children.

Comparison of Tidal Volumes at the Endotracheal Tube and at the Ventilator.

OBJECTIVE: Lung protective ventilation for children with acute respiratory distress syndrome requires accurate assessment of tidal volume. Although modern ventilators compensate for ventilator tubing compliance, tidal volume measured at the ventilator may not be accurate, particularly in small children. Although ventilator-specific proximal flow sensors that measure tidal volume at the endotracheal tube have been developed, there is little information regarding their accuracy. We sought to test the accuracy of ventilator measured tidal volume with and without proximal flow sensors against a calibrated pneumotachometer in children. DESIGN: Prospective, observational. SETTING: Tertiary care PICU. PATIENTS: Fifty-one endotracheally intubated and mechanically ventilated children younger than 18 years. INTERVENTIONS: Tidal volumes were measured at the ventilator, using a ventilator-specific flow sensor, and a calibrated pneumotachometer connected to the SensorMedics 2600A Pediatric Pulmonary Function Cart. MEASUREMENTS AND MAIN RESULTS: In a pressure control mode of ventilation: median tidal volume measured with the pneumotachometer (9.5 mL/kg [interquartile range, 8.2-11.7 mL/kg]) was significantly higher than tidal volume measured either at the ventilator (8.2 mL/kg [7.1-9.6 mL/kg]) or at the proximal flow sensor (8.1 mL/kg [7.2-10.0 mL/kg]) (p < 0.001). In pressure regulated volume control mode of ventilation: median tidal volume measured with the pneumotachometer (10.2 mL/kg [8.8-12.4 mL/kg]) was significantly higher than tidal volume measured either at the ventilator (8.0 mL/kg [7.1-9.7 mL/kg]) or at the proximal flow sensor (8.5 mL/kg [7.3-10.4 mL/kg]) (p < 0.001). These findings were consistent when subgrouped by ventilator type and circuit size. CONCLUSIONS: Tidal volume measured either at the endotracheal tube with a proximal flow sensor or at the ventilator with compensation for tubing compliance are both significantly lower than tidal volume measured with a calibrated pneumotachometer. This underestimation of delivered tidal volume may be particularly important when managing children with acute respiratory distress syndrome.