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Respiratory support of the critically ill neonate has steadily shifted from invasive to noninvasive forms of support. There have recently been a number of important advances in our understanding of the changes to neonatal resuscitation practices as they pertain to clinically important outcomes, mechanisms of gas exchange for high-flow nasal cannula, and best use of noninvasive ventilation and predicting response. Although the proportion of infants requiring intubation and mechanical ventilation has decreased, the most severely ill often still require intubation and ventilation. Recently, volume-targeted ventilation, high-frequency ventilation, and different methods of assessing weaning and extubation have been investigated. This review summarizes a number of important advances that have been made in the management of prematurity and neonatal respiratory distress syndrome.

Purpose In Low and Middle-Income Countries mechanical ventilators or commercially available devices used to offer continuous positive airway pressure (CPAP) are not readily affordable and available. In Ghana, nearly 10% of critically ill patients presenting to the emergency department require ventilator support. Description We designed, built and tested a simple expiratory positive airway pressure (EPAP) device to provide adult respiratory support in low resource environments with or without supplemental oxygen and without the need for electricity. Evaluation Laboratory tests demonstrated that the device is capable of delivering EPAP at levels expected to provide significant assistance to some patients. We present the first two cases where the use of this simple EPAP device provided critical respiratory support during weaning of patients from mechanical ventilation. Conclusions A low cost 3D printable adult respiratory support device could provide substantial benefit to patients suffering from respiratory distress through the delivery of appropriate levels of EPAP in a low resource setting with limited infrastructure. Further clinical validation is needed for broader application in low resource settings.

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.

BACKGROUND: Bedside monitors in the ICU routinely measure and collect patients9 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 patients9 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 Children9s 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 subjects9 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.)

BACKGROUND: High-frequency jet ventilation (HFJV) has been used in conjunction with conventional ventilation for premature infants with respiratory failure. We sought to identify parameters that were associated with mortality in subjects who underwent HFJV. METHODS: Subjects were enrolled if birthweight was ≤ 2,000 g and they were ≤ 34 weeks gestational age. Subjects were excluded if they received HFJV at the time of admission because we aimed to study subjects who failed conventional ventilation. Subject demographics, ventilator parameters, and laboratory data were extracted and analyzed. The Mann-Whitney U-test was used to assess differences in continuous variables, and the chi-square and Fisher exact tests were used for categorical variables between the groups. To assess variables that were predictive of mortality, we used both univariate and multivariate logistic regression analysis. Independent predictors of mortality were identified and used to create a multivariate risk score. Receiver operating characteristic curves were constructed to evaluate the predictive accuracy of the multivariate risk score. RESULTS: A total of 53 premature subjects (n = 37 male) were studied, of whom 39 (74%) survived to discharge or transfer back to referring hospital. In the univariate model, female sex, older gestational age, higher birthweight, HFJV peak inspiratory pressure at 1 h, and oxygen saturation index at 4 h were associated with mortality. In the final multivariate logistic regression model, female sex (odds ratio 4.1, 95% CI 1.2–19.8, P = .044), closed ductus arteriosus (odds ratio 7.7, 95% CI 1.3–39.5, P = .016), and oxygen saturation index > 5.5 (odds ratio 6.0, 95% CI 1.5–28.3, P = .02) were independent predictors of mortality. CONCLUSIONS: We identified that oxygen saturation index > 5.5 after 4 h of HFJV, female sex, and closed ductus arteriosus were independent predictors of mortality.

BACKGROUND: Intravenous formulations of epoprostenol are frequently delivered via nebulizer to treat pulmonary hypertension in acutely ill patients. Although their efficacy as pulmonary vasodilators has been shown to be comparable to inhaled nitric oxide, the local effects of these formulations within the airways have not been determined. We hypothesized that the alkaline diluents of these compounds would lead to increased airway epithelial cell death and ciliary cessation. METHODS: Human bronchial epithelial cells were exposed to epoprostenol in glycine and arginine diluents or control fluid. Ciliary beat frequency, lactate dehydrogenase, and total RNA levels were measured before and after exposure. Results were compared between exposure and control groups. RESULTS: Ciliary beat frequency ceased immediately after exposure to epoprostenol with both diluents. Lactate dehydrogenase levels increased by 200% after exposure to epoprostenol and glycine diluent (P = .002). Total RNA levels were undetectable after exposure to epoprostenol and arginine, indicating complete cell death and lysis (P = .015). Ciliary beat frequency ceased after 30 s of exposure to epoprostenol and glycine (P = .008). There was no difference between cells exposed to epoprostenol and those exposed only to diluent. CONCLUSIONS: Exposure to intravenous formulations of epoprostenol in glycine and arginine caused increased cell death and ciliary cessation in bronchial epithelial cells. These findings suggest that undesired local effects may occur when these compounds are delivered as inhaled aerosols to patients.

The electronic health record allows the assimilation of large amounts of clinical and laboratory data. Big data describes the analysis of large data sets using computational modeling to reveal patterns, trends, and associations. How can big data be used to predict ventilator discontinuation or impending compromise, and how can it be incorporated into the clinical workflow? This article will serve 2 purposes. First, a general overview is provided for the layperson and introduces key concepts, definitions, best practices, and things to watch out for when reading a paper that incorporates machine learning. Second, recent publications at the intersection of big data, machine learning, and mechanical ventilation are presented.

Asthma is an obstructive airway disease affecting children and adults throughout the world. It is a heterogeneous disease with a variety of causes and treatments. Research in the diagnosis, treatment, and management of asthma is ongoing, and there were > 8,000 publications on asthma in 2019. This paper reviews several research articles about asthma from 2019 that are most relevant for practicing respiratory therapists caring for patients with asthma.

BACKGROUND: There is limited evidence supporting an optimum method for removing mucus from the airways of hospitalized infants with bronchiolitis. This study was designed to evaluate short-term physiologic effects between nasal aspiration and nasopharyngeal suctioning in infants. METHODS: Sixteen infants requiring hospitalization for supportive management of bronchiolitis were instrumented with transcutaneously measured partial pressure of carbon dioxide (PtcCO2) and SpO2 monitoring. Electrical impedance tomography (EIT) was used to estimate changes in inspiratory and end-expiratory lung volume loss and recovery. Subjects were suctioned with both nasal aspiration and nasopharyngeal suctioning methods in a randomized order (8 received nasal aspiration followed by nasopharyngeal suctioning, and 8 received nasophayrgeal suctioning followed by nasal aspiration). Noninvasive gas exchange and EIT measurements were obtained at baseline (pre-suction) and at 10, 20, and 30 min following each suctioning intervention. Sputum mass was obtained following suctioning, and clinical respiratory severity scores, before and after suctioning, were computed. RESULTS: There were no differences in inspiratory EIT (P = .93), change in end-expiratory lung impedance (ΔEELI; P = .53), PtcCO2 (P = .41), SpO2 (P = .88), heart rate (P = .31), or breathing frequency (P = .15) over the course of suctioning between nasal aspiration and nasopharyngeal suctioning. Sputum mass (P = .14) and clinical respiratory score differences before and after suctioning (P = .59) were not different between the 2 suctioning interventions. Sputum mass was not associated with ΔEELI at 30 min for nasal aspiration (ρ = 0.11, P = .69), but there was a moderate positive association for nasopharyngeal suctioning (ρ = 0.50, P = .048). CONCLUSIONS: Infants with viral bronchiolitis appeared to tolerate both suctioning techniques without adverse short-term physiologic effects, as indicated by the unchanged gas exchange and estimated lung volumes (EIT). Nasopharyngeal suctioning recovered 36% more sputum than did nasal aspiration and there was moderate correlation between sputum mass and end-expiratory lung impedance change at 30 minutes post-suction with nasopharyngeal that was not present with nasal aspiration. It is possible that a subset of patients may benefit from one type of suctioning over another. Future research focusing on important outcomes for suctioning patients with bronchiolitis with varying degrees of lung disease severity is needed.

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 S pO 2 / F IO 2 . 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.

Background Positive end-expiratory pressure (PEEP) is often increased to improve ventilation efficiency and gas exchange during pediatric mechanical ventilation. Although it is clinically important to optimize PEEP in this population, there is a paucity of literature to guide the clinician at the bedside. Increasingly, time-series physiologic data are available for mechanically ventilated subjects in the intensive care unit. However, these data have not been adequately explored in the literature. Therefore, we sought to apply time-series computable phenotyping on time-series physiologic data and develop a model to predict PEEP response in mechanically ventilated children. Methods We conducted a retrospective analysis of continuous data in a academic hospital multidisciplinary intensive care unit. Patients were elgible for inclusion in the study if they received mechanically ventilation for > 25 hours and were < 18 years of age. Time-series data from the patient monitor and mechanical ventilator were abstracted 1-hour preceding and 1-hour following a PEEP change. PEEP increase (PEEPincrease), a responderwas defined as anyone who exhibited an improved dead-space fraction (Vd/Vt); non-respondersdemonstrated a worsening Vd/Vtin the hour following the PEEP change. Features from continuous mechanical ventilation variables were extracted and used to train a support vector machine model in order to predict Vd/Vt response to changes in PEEP. The performance of the model was assessed by calculating the area under the receiver operator characteristic curve (AUROC) and computing measures of diagnostic accuracy. Results In all, 393 PEEP change cases were included in the analysis in 83 subjects. A total of 27 computable phenotypes were identified and incorporated into the model. The AUROC was 0.82 and 0.90 for classifying response to PEEP increases and decreases respectively. The overall diagnostic accuracy was 0.75 for PEEP increases and 0.84 for PEEP decreases. Conclusions The model classified responders to increases and decreases in PEEP with reasonable accuracy. The model performed better for those cases when PEEP was decreases. In the future, these methods may play an important role in optimizing care of the mechanically ventilated pediatric patients, especially if they can be tailored to individual institutions.

BACKGROUND: A universal method for determining ideal body weight (IBW) for the application of appropriate tidal volumes in children on mechanical ventilation is elusive. We sought to compare 3 commonly used IBW methods for subjects between ages 2 and 20 y. METHODS: Demographic data were recorded, and the IBW was calculated based on the McLaren-Read, Moore, and body mass index methods by using growth chart data from the Centers for Disease Control and Prevention. The percentage error between each IBW method and the actual body weight were calculated and reported as median (interquartile range). We decided a priori that a ≥10% difference between the actual body weight and IBW would be clinically important. The Wilcoxon signed-rank test was used to compare the actual body weight with the IBW. Bland-Altman analysis was used to assess the individual agreement of each IBW method with the actual body weight. The Kruskal-Wallis test was used to detect differences among the IBW methods. RESULTS: A total of 58 subjects (36% female) were analyzed. The median (interquartile range) percent weight error between the actual body weight and calculated the IBW was 14.8% (1.9–22.1%, P = .038), 13.8% (4.6–23.4%, P = .008), and 12.0% (3.9–20.5%, P = .037); the mean biases were 2.7 (95% CI −13.4 to 18.9) kg, 3.9 (95% CI −15.1 to 22.9) kg, 3.2 (95% CI −16.7 to 23.1) kg; and the numbers of subjects who would have a clinically important error were 29 (55.7%), 29 (56.9%), and 30 (51.7%) for the McLaren-Read, Moore, and body mass index methods, respectively. CONCLUSIONS: The majority of the subjects demonstrated a clinically important error between the actual body weight and the IBW. The percent error increased in subjects > 25 kg actual body weight. These data underline the importance of obtaining height measurements and calculated IBW in pediatric patients who are mechanically ventilated.

The effects of fluid administration during acute asthma exacerbation are likely unique in this patient population: highly negative inspiratory intrapleural pressure resulting from increased airway resistance may interact with excess fluid administration to favor the accumulation of extravascular lung water, leading to worse clinical outcomes.Investigate how fluid balance influences clinical outcomes in children hospitalized for asthma exacerbation.We analyzed the association between fluid overload and clinical outcomes in a retrospective cohort of children admitted to an urban children's hospital with acute asthma exacerbation. These findings were validated in two cohorts: a matched retrospective and a prospective observational cohort. Finally, ultrasound imaging was used to identify extravascular lung water and investigate the physiological basis for the inferential findings.In the retrospective cohort, peak fluid overload [(fluid input - output)/weight] is associated with longer hospital length of stay, longer treatment duration, and increased risk of supplemental oxygen use (P values 0.001). Similar results were obtained in the validation cohorts. There was a strong interaction between fluid balance and intrapleural pressure: the combination of positive fluid balance and highly negative inspiratory intrapleural pressures is associated with signs of increased extravascular lung water (P 0.001), longer length of stay (P = 0.01), longer treatment duration (P = 0.03), and increased risk of supplemental oxygen use (P = 0.02).Excess volume administration leading to fluid overload in children with acute asthma exacerbation is associated with increased extravascular lung water and worse clinical outcomes.

Ideally, care of the neonatal or the pediatric patient who is critically ill with respiratory failure would include a treatment strategy that minimizes lung injury, preserves respiratory muscle function, and provides adequate patient comfort. The physiologic rational for high-frequency, low-volume

Mechanical ventilation is frequently used in pediatric patients to ensure adequate gas exchange, ameliorate respiratory distress, and enable resolution of pulmonary or other disorders. However, a number of important challenges remain in the pediatric population because there is a paucity of large-scale randomized controlled trials to generate data and inform clinical practice. This review summarizes a number of discoveries and advances that have been made in pediatric mechanical ventilation from June 2017 to December 2018.

BACKGROUND: PEEP is titrated to improve oxygenation during mechanical ventilation. It is clinically desirable to identify factors that are associated with a clinical improvement or deterioration following a PEEP change. However, these factors have not been adequately described in the literature. Therefore, we aimed to quantify the empirical probability of PEEP changes having a positive effect upon oxygenation, compliance of the respiratory system (CRS), and the ratio of dead space to tidal volume (VD/VT). Further, clinical factors associated with positive response during pediatric mechanical ventilation are described. METHODS: Mechanically ventilated pediatric subjects in the ICU were eligible for inclusion in the study. During PEEP increases (PEEPincrease), a responder was defined as having an improved SpO2/FIO2 ratio; non-responders demonstrated a worsening SpO2/FIO2 ratio in the following hour. When PEEP was decreased (PEEPdecrease), a responder was anyone who maintained or increased the SpO2/FIO2 ratio; non-responders demonstrated a worsening SpO2/FIO2 ratio. Features from continuous mechanical ventilation variables were extracted, and differences between responders and non-responders were identified. RESULTS: 286 PEEP change cases were eligible for analysis in 76 subjects. For PEEPincrease cases, the empirical probability of positive response was 56%, 67%, and 54% for oxygenation, CRS, and VD/VT, respectively. The median SpO2/FIO2 increase was 13. For PEEPdecrease, the empirical probability of response was 46%, 53%, and 46% for oxygenation, CRS, and VD/VT, respectively. PEEPincrease responders had higher FIO2 requirements (70.8 vs 52.5%, P CONCLUSIONS: In children requiring mechanical ventilation, the responder rate was modest for both PEEPincrease and PEEPdecrease cases. These data suggest that PEEP titration often does not have the desired clinical effect, and predicting which patients will manifest a positive response is complex, requiring more sophisticated means of assessing individual subjects.

The use of invasive mechanical ventilation is a life-saving and essential component of pediatric intensive care. However, prolonged intubation can be associated with an increased risk of ventilator-induced lung injury, nosocomial infections, airway irritation or trauma, and sedative dependence.[1][1

Electrical impedance tomography (EIT) is a noninvasive, non-radiologic imaging modality that may be useful for the quantification of lung disorders and titration of mechanical ventilation. The principle of operation is based on changes in electrical conductivity that occur as a function of changes in lung volume during ventilation. EIT offers potentially important benefits over standard imaging modalities because the system is portable and non-radiologic and can be applied to patients for long periods of time. Rather than providing a technical dissection of the methods utilized to gather, compile, reconstruct, and display EIT images, the present article seeks to provide an overview of the clinical application of this technology as it relates to monitoring mechanical ventilation and providing decision support at the bedside. EIT has been shown to be useful in the detection of pneumothoraces, quantification of pulmonary edema and comparison of distribution of ventilation between different modes of ventilation and may offer superior individual titration of PEEP and other ventilator parameters compared with existing approaches. Although application of EIT is still primarily done within a research context, it may prove to be a useful bedside tool in the future. However, head-to-head comparisons with existing methods of mechanical ventilation titration in humans need to be conducted before its application in general ICUs can be recommended.

BACKGROUND: Thousands of children require mechanical ventilation each year. Although mechanical ventilation is lifesaving, it is also associated with adverse events if not properly managed. The systematic implementation of evidence-based practice through the use of guidelines and protocols has been shown to mitigate risk, yet variation in care remains prevalent. Advances in health-care technology provided the ability to stream data about mechanical ventilation and therapeutic response. Through these advances, a computer system was developed to enable the coupling of physiologic and ventilation data for real-time interpretation. Our aim was to assess the feasibility and utility of a newly developed patient categorization and scoring system to objectively measure compliance with standards of care. METHODS: We retrospectively categorized the ventilation and oxygenation statuses of subjects within our pediatric ICU utilizing 15 rules-based algorithms. Targets were predetermined based on generally accepted practices. All patient categories were calculated and presented as a percent score (0–100%) of acceptable ventilation, acceptable oxygenation, barotrauma-free, and volutrauma-free states. RESULTS: Two hundred twenty-two subjects were identified and analyzed encompassing 1,578 d of mechanical ventilation. Median age was 3 y, median ideal body weight was 14.7 kg, and 63% were male. The median acceptable ventilation score was 84.6%, and the median acceptable oxygenation score was 70.1% (100% being maximally acceptable). Potential for ventilator-induced lung injury was broken into 2 components: barotrauma and volutrauma. There was very little potential for barotrauma, with a median barotrauma-free state of 100%. Median potential for a volutrauma-free state was 56.1%. CONCLUSIONS: We demonstrate the first patient categorization system utilizing a coordinated data-banking system and analytics to determine patient status and a surveillance of mechanical ventilation quality. Further research is needed to determine whether interventions such as visual display of variance from goal and patient categorization summaries can improve outcomes. (ClinicalTrials.gov registration NCT02184208.)

BACKGROUND: Gas exchange measurements for carbon dioxide elimination (VCO2) and oxygen consumption (VO2) have been used to derive resting energy expenditure and guide energy prescription. Volumetric capnography is used in intensive care units and provides VCO2 measurements that could be used for titrating respiratory and nutritional support. We have recently suggested that measuring VCO2 may be sufficient to obtain a reasonable estimate of energy expenditure. However, data describing the accuracy of gas exchange measurement devices are limited. METHODS: We used an in vitro simulation model to test the accuracy of gas exchange measurements by 2 devices: the CCM Express indirect calorimeter and the NM3, a volumetric capnography monitor. A Huszczuk gas injection system combined with a high-fidelity lung simulator was used to simulate VO2 and VCO2 values in the pediatric and adult range. Bland-Altman analysis was used to examine the agreement between the measured and simulated values across a range of tidal volumes and gas exchange values. Additionally, agreement between the 2 devices was examined. RESULTS: During the adult simulation with the CCM Express, the mean bias (95% CI) for VCO2 values was −12.6% (−16.4 to −8.8%) and −17.5% (−19.9 to −15.1%) for VO2 values. For the pediatric simulation with the CCM Express, mean bias for VO2 was −14.7% (−16.4 to −13.0%) and VCO2 was −10.9% (−13.5 to −8.3%). For the adult and pediatric simulations with the NM3, the bias for VCO2 was −8.2% (−15.7 to −0.7%) and −8.3% (−19.4 to −2.8%), respectively. Between the 2 devices, the mean bias was −4.4% (−10.2 to 1.3%) and −2.3% (−11.4 to 6.8%) for the adult and pediatric VCO2 simulations, respectively. CONCLUSIONS: Currently available portable gas exchange monitors demonstrated acceptable agreement with reference VO2 and VCO2 values in an in vitro simulation. The devices demonstrated good agreement with each other.

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.

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.

Objectives Diet modification may improve body composition and respiratory variables in children with respiratory insufficiency. Our objective was to examine the effect of an individualized diet intervention on changes in weight, lean body mass, minute ventilation, and volumetric CO2 production in children dependent on long-term mechanical ventilatory support. Design Prospective, open-labeled interventional study. Setting Study subjects' homes. Patients Children, 1 month to 17 years old, dependent on at least 12 hr/d of transtracheal mechanical ventilatory support. Interventions Twelve weeks of an individualized diet modified to deliver energy at 90-110% of measured energy expenditure and protein intake per age-based guidelines. Measurements and main results During a multidisciplinary home visit, we obtained baseline values of height and weight, lean body mass percent by bioelectrical impedance analysis, actual energy and protein intake by food record, and measured energy expenditure by indirect calorimetry. An individualized diet was then prescribed to optimize energy and protein intake. After 12 weeks on this interventional diet, we evaluated changes in weight, height, lean body mass percent, minute ventilation, and volumetric CO2 production. Sixteen subjects, mean age 9.3 years (SD, 4.9), eight male, completed the study. For the diet intervention, a majority of subjects required a change in energy and protein prescription. The mean percentage of energy delivered as carbohydrate was significantly decreased, 51.7% at baseline versus 48.2% at follow-up, p = 0.009. Mean height and weight increased on the modified diet. Mean lean body mass percent increased from 58.3% to 61.8%. Minute ventilation was significantly lower (0.18 L/min/kg vs 0.15 L/min/kg; p = 0.04), and we observed a trend toward lower volumetric CO2 production (5.4 mL/min/kg vs 5.3 mL/min/kg; p = 0.06) after 12 weeks on the interventional diet. Conclusions Individualized diet modification is feasible and associated with a significant decrease in minute ventilation, a trend toward significant reduction in CO2 production, and improved body composition in children on long-term mechanical ventilation. Optimization of respiratory variables and lean body mass by diet modification may benefit children with respiratory insufficiency in the ICU.

Accurate assessment of resting energy expenditure (REE) and metabolic state is essential to optimize nutrient intake in critically ill patients. We aimed to examine the accuracy of a simplified equation for predicting REE using carbon dioxide elimination (VCO2) values.We conducted a two-center study of metabolic data from mechanically ventilated children less than 18 years of age. Mean respiratory quotient (RQ) from the derivation set (n = 72 subjects) was used to modify the Weir equation to obtain a simplified equation based on VCO2 measurements alone. This equation was then applied to subjects at the second institution (validation dataset, n = 94) to predict resting energy expenditure. Bland-Altman analysis was used to assess the agreement between measured REE values, and REE estimated by the new equation as well as the Schofield equation. We also examined the accuracy of the new equation in classifying patients according to their metabolic state.Mean respiratory quotient (± SD) of 0.89 ± 0.09 in the derivation set was used to obtain a simplified equation, REE (kcal/day) = 5.534*VCO2 (L/min)*1440. In relation to the measured REE in the validation set, the mean bias (limits of agreement) for the REE predicted by this equation was -0.65% (-14.4-13.1%); and the overall diagnostic accuracy for classifying subjects as hypometabolic or hypermetabolic was 84%. Mean bias (limits) of agreement between measured and Schofield equation estimated REE was -0.1% (-40.5-40.7%).A simplified metabolic equation using VCO2 values was superior to the standard equation in estimating REE, and provided a reasonably accurate metabolic classification in mechanically ventilated children. In the absence of indirect calorimetry, bedside VCO2 monitoring could provide valuable continuous metabolic information to guide optimal nutrient intake.

To evaluate the nutritional and metabolic status and body composition of children on long-term mechanical ventilation using a home-based model.Children on home mechanical ventilation, for at least 12 hours a day, were eligible. We performed anthropometry, bioelectrical impedance analysis (BIA), actual energy intake (AEI), and indirect calorimetry in the subject's home. Agreement between measured energy expenditure (MEE) from indirect calorimetry, and estimated energy expenditure by the Schofield equation and a novel volumetric carbon dioxide production-based equation was examined. Agreement between fat mass estimates from anthropometry and BIA was examined and compared with population norms.We enrolled 20 children, 11 (55%) male; mean age 8.4 years (SD 4.8). Mean weight for age z-score was -0.26 (SD 1.48); 9/20 had z-scores-1 or+1. Thirteen were underfed (AEI:MEE90%) or overfed (AEI:MEE110%); 11 of 19 had protein intake that was less than recommended by guidelines. Fifteen subjects were hypo- or hypermetabolic. Mean (SD) fat mass % was 33.6% (8.6) by anthropometry, which was significantly greater than matched population norms (mean 23.0%, SD 6.1, P.001). The estimated energy expenditure by a volumetric carbon dioxide production-based equation was in stronger agreement with the MEE than the Schofield equation (mean bias 0.06%, limits -15.98% to 16.16% vs mean bias -1.31%, limits -74.3% to 72%, respectively). BIA and anthropometric fat mass values were not in agreement.A majority of children on home ventilation are characterized by malnutrition, altered metabolic status, and suboptimal macronutrient intake, in particular low protein intake. A multidisciplinary home-based model facilitates individualized energy and protein delivery and may improve outcomes in this cohort.

Background Macronutrient delivery during pediatric ECMO therapy can be challenging. We examined predictors of nutrient delivery in the first 2 weeks of extracorporeal membrane oxygenation (ECMO) therapy in the pediatric intensive care unit (ICU). Methods Details of macronutrient delivery were recorded in children (newborn-18 years of age) who survived 24 hours after cannulation to ECMO over a 3-year period (2012-2015). Results We analyzed data from 54 consecutive eligible patients, 43% female, with median (interquartile range) ECMO duration of 8.5 (6-24) days, age 0.1 (0, 16) months, ICU length of stay 32 (21, 60) days, and 28-day mortality 13%. Median weight for age z score declined from -0.1 at admission to -1.2 at 30 days (P = 0.013). At least 80% goal energy and protein was delivered in 35 (65%) and 33 (61%) patients, respectively, by day 7; 10% of energy and 11% protein goal was delivered enterally. Parenteral nutrition (PN) was utilized in 47 (87%) patients, initiated by day 1 (1, 3). Enteral nutrition (EN) was successfully delivered in 49 (94%) patients (35% postpyloric), initiated by day 6 (2, 16). Younger age (P = 0.01) and venoarterial mode of ECMO (P = 0.0014) were associated with lower EN delivery. Use of umbilical artery catheters or vasoactive infusions did not impede EN delivery. Late PN delivery was associated with cumulative protein deficits (P = 0.019) and failure to achieve nutrient delivery goals by day 7. Conclusions Optimal nutrient delivery was achieved in most patients by day 7, predominantly via PN. Early EN is feasible in low volumes, but PN may be essential to prevent cumulative energy and protein deficits during the first week of ECMO.

BACKGROUND: Although effective in the neonatal population, exogenous pulmonary surfactant has not demonstrated a benefit in pediatric and adult subjects with hypoxic lung injury despite a sound physiologic rationale. Importantly, neonatal surfactant replacement therapy is administered in conjunction with low fractional FIO2 while pediatric/adult therapy is administered with high FIO2. We suspected a connection between FIO2 and surfactant performance. Therefore, we sought to assess a possible mechanism by which the activity of pulmonary surfactant is adversely affected by direct oxygen exposure in in vitro experiments. METHODS: The mechanical performance of pulmonary surfactant was evaluated using 2 methods. First, Langmuir-Wilhelmy balance was utilized to study the reduction in surface area (δA) of surfactant to achieve a low bound value of surface tension after repeated compression and expansion cycles. Second, dynamic light scattering was utilized to measure the size of pulmonary surfactant particles in aqueous suspension. For both experiments, comparisons were made between surfactant exposed to 21% and 100% oxygen. RESULTS: The δA of surfactant was 21.1 ± 2.0% and 35.8 ± 2.0% during exposure to 21% and 100% oxygen, respectively (P = .02). Furthermore, dynamic light-scattering experiments revealed a micelle diameter of 336.0 ± 12.5 μm and 280.2 ± 11.0 μm in 21% and 100% oxygen, respectively (P CONCLUSIONS: The characteristics of pulmonary surfactant were adversely affected by short-term exposure to oxygen. Specifically, surface tension studies revealed that short-term exposure of surfactant film to high concentrations of oxygen expedited the frangibility of pulmonary surfactant, as shown with the δA. This suggests that reductions in pulmonary compliance and associated adverse effects could begin to take effect in a very short period of time. If these findings can be demonstrated in vivo, a role for reduced FIO2 during exogenous surfactant delivery may have a clinical benefit.

Oxygen is a colorless, odorless, tasteless gas that is utilized by the body for respiration. Oxygen has played a major role in respiratory care. Oxygen therapy is useful in treating hypoxemia but is often thought of as a benign therapy. After many years of study, we have learned a great deal of the benefits and potential risk of this powerful drug. Today oxygen gas is cheap, widely available, and easy to administer. Oxygen delivery devices vary in cost from a few cents for a simple nasal cannula to $25-$50 for some humidified systems. Undoubtedly, oxygen therapy is an important tool and has saved many lives and improved others. However, oxygen therapy risk, cost, and benefits should be considered in the same way as other drugs and titrated to a measured end point to avoid excessive or inadequate dosing. Withholding oxygen can have a detrimental effect, yet continuing to provide oxygen therapy when it is no longer indicated can prolong hospitalization and increase the cost of care. This comprehensive review begins with an assessment of need and a review of physiologic effects, potential toxicities, and common delivery devices, and it ends with advances in oxygen therapy with a focus on the pediatric patient.

Objective To evaluate the accuracy of estimated fat mass and fat-free mass from bedside methods compared with reference methods in children with chronic illnesses. Study design Fat mass and fat-free mass values were obtained by skinfold, bioelectrical impedance analysis (BIA), dual-energy x-ray absorptiometry (DXA), and deuterium dilution method in children with spinal muscular atrophy, intestinal failure, and post hematopoietic stem cell transplantation (HSCT). Spearman's correlation and agreement analyses were performed between (1) fat mass values estimated by skinfold equations and by DXA and (2) fat-free mass values estimated by BIA equations and by DXA and deuterium dilution methods. Limits of agreement between estimating and reference methods within ±20% were deemed clinically acceptable. Results Fat mass and fat-free mass values from 90 measurements in 56 patients, 55% male, and median age of 11.6 years were analyzed. Correlation coefficients between the skinfold-estimated fat mass values and DXA were 0.93-0.94 and between BIA-estimated fat-free mass values and DXA were 0.92-0.97. Limits of agreement between estimated and DXA values of fat mass and fat-free mass were greater than ±20% for all equations. Correlation coefficients between estimated fat-free mass values and deuterium dilution method in 35 encounters were 0.87-0.91, and limits of agreement were greater than ±20%. Conclusion Estimated body composition values derived from skinfold and BIA may not be reliable in children with chronic illnesses. An accurate noninvasive method to estimate body composition in this cohort is desirable.

BACKGROUND: High-frequency jet ventilation (HFJV) has been used in conjunction with conventional ventilation for infants with respiratory failure. We sought to identify parameters that were associated with successful application of HFJV in patients with hypercapnic respiratory failure. METHODS: A single-center, retrospective review of infants who received HFJV was conducted. Subjects were enrolled if birthweight was ≤2,000 g and capillary PCO2 was ≥55 mm Hg. Ventilator parameters and physiologic data were recorded at 1 h before HFJV initiation and at hours 1, 4, and 6 following conversion. Subjects were classified as responders if capillary PCO2 was reduced by ≥10% after 1 h of HFJV. Data included peak inspiratory pressure, PEEP, capillary PCO2, and oxygen saturation index (equal to mean airway pressure × FIO2 × 100/SpO2). Because the data were not normally distributed, they are reported as median (interquartile range), and the Mann-Whitney test was used to assess differences in continuous data between groups. Categorical data were analyzed using a chi-square and Fisher exact test. RESULTS: Thirty-four premature infants (n = 24 male) were studied. Twenty-five subjects were classified as responders and demonstrated a significant reduction of capillary PCO2 and FIO2 and increased pH within the first hour. The non-responders demonstrated a higher conventional ventilation peak inspiratory pressure (25 cm H2O vs 19 cm H2O, P = .005) and had a greater postmenstrual age (30 weeks vs 26.5 weeks, P = .01). This group had a higher oxygen saturation index (7.25 vs 3.36, P = .03) and FIO2 requirements (0.6 vs 0.35, P = .038) at 4 h. CONCLUSIONS: We identified that lower postmenstrual age, improvements in capillary PCO2 and pH at 1 h, and a reduction of FIO2 were associated with good response to HFJV. These data may help to identify patients who are likely to benefit from HFJV in the neonatal intensive care unit.

BACKGROUND: The systematic implementation of evidence-based practice through the use of guidelines, checklists, and protocols mitigates the risks associated with mechanical ventilation, yet variation in practice remains prevalent. Recent advances in software and hardware have allowed for the development and deployment of an enhanced visualization tool that identifies mechanical ventilation goal variance. Our aim was to assess the utility of daily goal establishment and a computer-aided visualization of variance. METHODS: This study was composed of 3 phases: a retrospective observational phase (baseline) followed by 2 prospective sequential interventions. Phase I intervention comprised daily goal establishment of mechanical ventilation. Phase II intervention was the setting and monitoring of daily goals of mechanical ventilation with a web-based data visualization system (T3). A single score of mechanical ventilation was developed to evaluate the outcome. RESULTS: The baseline phase evaluated 130 subjects, phase I enrolled 31 subjects, and phase II enrolled 36 subjects. There were no differences in demographic characteristics between cohorts. A total of 171 verbalizations of goals of mechanical ventilation were completed in phase I. The use of T3 increased by 87% from phase I. Mechanical ventilation score improved by 8.4% in phase I and 11.3% in phase II from baseline ( P = .032). The largest effect was in the low risk V T category, with a 40.3% improvement from baseline in phase I, which was maintained at 39% improvement from baseline in phase II ( P = .01). mechanical ventilation score was 9% higher on average in those who survived. CONCLUSIONS: Daily goal formation and computer-enhanced visualization of mechanical ventilation variance were associated with an improvement in goal attainment by evidence of an improved mechanical ventilation score. Further research is needed to determine whether improvements in mechanical ventilation score through a targeted, process-oriented intervention will lead to improved patient outcomes. (ClinicalTrials.gov registration NCT02184208.)

Summary Background & aims A variety of indirect calorimetry (IC) devices are used for gas exchange measurement and calculation of resting energy expenditure (REE) in the pediatric intensive care unit. The aim of this investigation was to compare oxygen consumption (VO 2 ), carbon dioxide elimination (VCO 2 ), REE and respiratory quotient (RQ) in mechanically ventilated children, obtained by 2 devices using distinct gas sampling methods. Methods Mechanically ventilated children were targeted for IC and gas exchange measurements were recorded for a 30 min period, simultaneously using the E-COVX ® (gas sampling at the airway) and the Vmax ® (gas sampling at the humidifier and ventilator exhaust). Steady state gas exchange measurements by the 2 devices were tested for agreement using Spearman correlation and Bland–Altman analysis. Results Steady state data from both devices were available in 19 tests and were included in the analysis. The correlations coefficients for measurements by the 2 devices were r = 0.903( P P P P 2 , VCO 2 , REE and RQ, respectively. The mean percentage bias (limits of agreement) for VO 2 , VCO 2 , REE and RQ values between the two methods (Vmax–E-COVX) was 0.2 (−41.8–42.3), −0.8 (−21.8–20.1), −2.2 (−33.9–29.6) and 1.9 (−21–24.9) respectively. Conclusions Despite strong correlations and small mean biases for VO 2 , VCO 2 and REE obtained by the Vmax ® and E-COVX ® , the limits of agreement were beyond the clinically acceptable range. These devices should not be used interchangeably for gas exchange measurements in mechanically ventilated children.

To utilize real-time electrical impedance tomography to guide lung protective ventilation in an animal model of acute respiratory distress syndrome.Prospective animal study.Animal research center.Twelve Yorkshire swine (15 kg).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.Positive end-expiratory pressure levels were higher in the electrical impedance tomography-guided group (14.3 cm H₂O vs. 8.6 cm H₂O; p0.0001), 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, p0.0001; 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, p0.01; AFEIT 75% samples vs. AFCONTROL 100% samples, p0.01). 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%.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.

The benefit of treating acute lung injury with recruitment manoeuvres is controversial. An impediment to settling this debate is the difficulty in visualizing how distinct lung regions respond to the manoeuvre. Here, regional lung mechanics were studied by electrical impedance tomography (EIT) during a stepwise recruitment manoeuvre in a porcine model with acute lung injury. The following interaction between dependent and non-dependent regions consistently occurred: atelectasis in the most dependent region was reversed only after the non-dependent region became overdistended. EIT estimates of overdistension and atelectasis were validated by histological examination of lung tissue, confirming that the dependent region was primarily atelectatic and the non-dependent region was primarily overdistended. The pulmonary pressure?volume equation, originally designed for modelling measurements at the airway opening, was adapted for EIT-based regional estimates of overdistension and atelectasis. The adaptation accurately modelled the regional EIT data from dependent and non-dependent regions (R2?> 0.93, P < 0.0001) and predicted their interaction during recruitment. In conclusion, EIT imaging of regional lung mechanics reveals that overdistension in the non-dependent region precedes atelectasis reversal in the dependent region during a stepwise recruitment manoeuvre.

Accurate measurement of resting energy expenditure (REE) using indirect calorimetry (IC) facilitates optimal energy prescription. Steady-state (SS) REE obtained using a 5-minute protocol (SS5) has been used as a surrogate for 24-hour REE measurement. However, SS5 conditions are difficult to achieve in critically ill children on mechanical ventilatory support.The authors prospectively examined factors associated with successful IC testing using the standard SS5 protocol in mechanically ventilated children. They examined the agreement of REE between SS5 and 2 abbreviated SS protocols: 4-minute (SS4) and 3-minute (SS3) protocols as well as the Schofield prediction equation, using Bland-Altman analysis.IC testing (n = 45) was completed in 34 children. SS was achieved during 25 (56%), 31 (69%), and 42 (93%) tests, using the SS5, SS4, and SS3 protocols, respectively. Intratest variability in respiratory rate, endotracheal tube leak, and inspiratory time was associated with failed IC by the SS5 protocol. The mean bias (limits of agreement) for REE was 2.8 (-47 to 65), 5.8 (-71 to 72), and -127 (-418 to 1176) kcal/d using SS4, SS3, and Schofield, respectively. A stronger agreement was observed when means of all abbreviated SS REE values during a 30-minute test were used.In mechanically ventilated children, 4-minute and 3-minute SS protocols allowed REE measurements to be obtained in most patients with reasonable accuracy. Abbreviated protocols may decrease the need to rely on inaccurate equations when assessing energy expenditure in children who fail IC testing by standard SS criteria.

Purpose High-frequency airway clearance therapy is a positive pressure secretion clearance modality used in pediatric and adult applications. However, pressure attenuation across different size endotracheal tubes (ETT) has not been adequately described. This study quantifies attenuation in an in vitro model. Materials and methods The MetaNeb® System was used to deliver high-frequency pressure pulses to 3.0, 4.0, 6.0 and 8.0 mm ID ETTs connected to a test lung during mechanical ventilation. The experimental setup included a 3D-printed trachea model and imbedded pressure sensors. The pressure attenuation (P att %) was calculated: P att % = [(P proximal –P distal )/P proximal ]x100. The effect of pulse frequency on P distal and P proximal was quantified. Results P att % was inversely and linearly related to ETT ID and (y = − 7.924x + 74.36; R 2 = 0.9917, P = .0042 for 4.0 Hz pulse frequency and y = − 7.382 + 9.445, R 2 = 0.9964, P = .0018 for 3.0 Hz pulse frequency). P att % across the 3.0, 4.0, 6.0 and 8.0 mm I.D. ETTs was 48.88 ± 10.25%, 40.87 ± 5.22%, 27.97 ± 5.29%, and 9.90 ± 1.9% respectively. Selecting the 4.0 Hz frequency mode demonstrated higher P proximal and P distal compared to the 3.0 Hz frequency mode (P = .0049 and P = .0065). Observed P distal was 2 O for all experiments. Conclusions In an in vitro model, pressure attenuation was linearly related to the inner diameter of the endotracheal tube; with decreasing attenuation as the ETT size increased.

In reply: Mr Chatburn's letter to the Editor highlights some important points about our paper.[1][1] Let's first start with barotrauma. Barotrauma is used to describe the manifestations of extra-alveolar air during mechanical ventilation often associated with high airway pressures.[2][2] Mr

BACKGROUND: Accurate measurement of carbon dioxide elimination (VCO2) and oxygen consumption (VO2) at the bedside may help titrate nutritional and respiratory support in mechanically ventilated patients. Continuous VCO2 monitoring is now available with many ventilators. However, because normative data are sparsely available in the literature, we aimed to describe the range of VCO2 and VO2 values observed in mechanically ventilated children. We also aimed to examine the characteristics of VCO2 values that are associated with standard steady state (5-min period when VCO2 and VO2 variability are < 10%). METHODS: Mechanically ventilated patients who underwent indirect calorimetry testing were eligible for inclusion, and subjects who achieved standard steady state were included. Normalized VCO2 and VO2 values (mL/kg/min) were modeled against subject height, and correlation coefficients were computed to quantify the goodness of fit. A steady-state definition using only VCO2 was developed (VCO2 variability of < 5% for a 5-min period) and tested against standard steady state using sensitivity and specificity. RESULTS: Steady-state data from 87 indirect calorimetry tests (in 70 subjects) were included. For age groups 8 y, the mean VCO2 values were 7.6, 5.8, and 3.5 mL/kg/min. Normalized VCO2 and VO2 values were inversely related to subject height and age. The relationships between normalized gas exchange values and height were demonstrated by the models: VCO2 = 115 × (height in cm)−0.71 (R = 0.61, P < .001) and VO2 = 130 × (height in cm)−0.72 (R = 0.61, P < .001). Steady-state VCO2 predicted standard steady state (sensitivity of 0.84, specificity of 1.0, P < .01). CONCLUSIONS: VCO2 and VO2 measurements correlated with subject height and age. Smaller and younger subjects produced larger amounts of CO2 and consumed more O2 per unit of body weight. The use of a 5-min period when VCO2 varied by < 5% predicted standard steady state. Our observations may facilitate greater utility of VCO2 at the bedside in the pediatric ICU and thereby extend the benefits of metabolic monitoring to a larger group of patients.

Respiratory care practice includes neonatal respiratory care, pulmonary function testing, and pulmonary rehabilitation. The purpose of this paper is to review the recent literature related to these topics in a manner that is most likely to have interest to the readers of Respiratory Care.

Delivery of adequate nutrients during illness to counteract the metabolic stress response and facilitate healing and tissue repair is an important goal in the care of critically ill children. With recent advances in technology, accurate minute-to-minute gas exchange and energy expenditure measurements are now available in intensive care units. The bedside availability of these devices may allow a titrated approach to energy delivery for patients, ushering in a new era of individualized nutrition therapy. Basic concepts, available monitoring devices, indications, pitfalls, and bedside application of metabolic monitoring are discussed in this article.