Inhaled helium-oxygen revisited: effect of inhaled helium-oxygen during the treatment of status asthmaticus in children

Heliox for Pediatric Critical Asthma: A Multicenter, Retrospective, Registry-Based Descriptive Study

BACKGROUND

In cases of critical asthma (CA), heliox may be applied as an adjunctive rescue therapy to avoid invasive mechanical ventilation (MV), improve deposition of aerosolized medications, and enhance laminar airflow through obstructed airways. Using the Pediatric Health Information System (PHIS) registry, we evaluate heliox prescribing and explored for differences in MV rates and hospital length of stay (LOS) among children with and without heliox exposure.

METHODS

We performed a retrospective cohort study using PHIS data from 42 pediatric intensive care units among children 5-17 years of age admitted for CA from 2010 through 2019. Primary outcomes were heliox prescribing rates and trends. Secondary outcomes were invasive MV rates and LOS assessed in a subgroup of children receiving ≥ 1 adjunctive intervention(s).

RESULTS

Of the 19,780 studied, heliox was prescribed in 12.5% and linearly declined from 16.1% in 2010 to 5.6% in 2019. The overall MV rate was 12.8% and was lower in subjects receiving heliox alone (4.9%) compared to heliox plus alternative adjunctive therapies [31.2%] or children receiving non-heliox adjunctive therapies [22.1%], P < .01). Accounting for MV, no difference in LOS was observed. In exploratory adjusted models, MV free hospitalization was associated with heliox-only exposure (OR: 0.33, 95% CI: 0.17-0.63, P < .01) and exposure to multiple adjunctive therapies was associated with MV (OR: 2.48, 95% CI: 1.56-3.94, P < .01).

CONCLUSIONS

In this multicenter retrospective study from 42 children's hospitals, heliox prescribing for CA declined over the last decade. Subjects receiving multiple adjunctive therapies more commonly required invasive MV perhaps indicating a greater severity of illness. At this time, prospective trials needed to identify the role of heliox for pediatric CA.

Paediatrics: how to manage acute asthma exacerbations

Background

Asthma is the most common chronic disease of childhood and a major source of childhood health burden worldwide. These burdens are particularly marked when children experience characteristic ‘symptom flare-ups’ or acute asthma exacerbations (AAEs). AAE are associated with significant health and economic impacts, including acute Emergency Department visits, occasional hospitalizations, and rarely, death. To treat children with AAE, several medications have been studied and used.

Methods

We conducted a narrative review of the literature with the primary objective of understanding the evidence of their efficacy. We present this efficacy evidence in the context of a general stepwise management pathway for paediatric AAEs. This framework is developed from the combined recommendations of eight established (inter)national paediatric guidelines.

Discussion

Management of paediatric AAE centres around four major care goals: (1) immediate and objective assessment of AAE severity; (2) prompt and effective medical interventions to decrease respiratory distress and improve oxygenation; (3) appropriate disposition of patient; and (4) safe discharge plans. Several medications are currently recommended with varying efficacies, including heliox, systemic corticosteroids, first-line bronchodilators (salbutamol/albuterol), adjunctive bronchodilators (ipratropium bromide, magnesium sulfate) and second-line bronchodilators (aminophylline, i.v. salbutamol, i.v. terbutaline, epinephrine, ketamine). Care of children with AAE is further enhanced using clinical severity scoring, pathway-driven care and after-event discharge planning.

Conclusions

AAEs in children are primarily managed by medications supported by a growing body of literature. Continued efforts to study the efficacy of second-line bronchodilators, integrate AAE management with long-term asthma control and provide fair/equitable care are required.

Ventilated Patients With COVID-19 Show Airflow Obstruction

Objective:

Many patients with coronavirus disease 2019 (COVID-19) need mechanical ventilation secondary to acute respiratory distress syndrome. Information on the respiratory system mechanical characteristics of this disease is limited. The aim of this study is to describe the respiratory system mechanical properties of ventilated COVID-19 patients.

Design, Setting, and Patients:

Patients consecutively admitted to the medical intensive care unit at the University of Iowa Hospitals and Clinics in Iowa City, USA, from April 19 to May 1, 2020, were prospectively studied; final date of follow-up was May 1, 2020.

Measurements:

At the time of first patient contact, ventilator information was collected including mode, settings, peak airway pressure, plateau pressure, and total positive end expiratory pressure. Indices of airflow resistance and respiratory system compliance were calculated and analyzed.

Main Results:

The mean age of the patients was 58 years. 6 out of 12 (50%) patients were female. Of the 21 laboratory-confirmed COVID-19 patients on invasive mechanical ventilation, 9 patients who were actively breathing on the ventilator were excluded. All the patients included were on volume-control mode. Mean [±standard deviation] ventilator indices were: resistive pressure 19 [±4] cmH₂O, airway resistance 20 [±4] cmH₂O/L/s, and respiratory system static compliance 39 [±16] ml/cmH₂O. These values are consistent with abnormally elevated resistance to airflow and reduced respiratory system compliance. Analysis of flow waveform graphics revealed a pattern consistent with airflow obstruction in all patients.

Conclusions:

Severe respiratory failure due to COVID-19 is regularly associated with airflow obstruction.

Standardized Protocol Is Associated With a Decrease in Continuous Albuterol Use and Length of Stay in Critical Status Asthmaticus

OBJECTIVES

The primary aim of this study was to reduce duration of continuous albuterol and hospital length of stay in critically ill children with severe status asthmaticus.

DESIGN

Observational prospective study from September 2012 to May 2016.

SETTING

Medicine ICU and intermediate care unit.

PATIENTS

Children greater than 2 years old with admission diagnosis of status asthmaticus admitted on continuous albuterol and managed via a standardized protocol.

INTERVENTIONS

The protocol was an iterative algorithm for escalation and weaning of therapy. The algorithm underwent three revisions. Iteration 1 concentrated on reducing duration on continuous albuterol; iteration 2 concentrated on reducing hospital length of stay; and iteration 3 concentrated on reducing helium-oxygen delivered continuous albuterol. Balancing measures included adverse events and readmissions.

MEASUREMENTS AND RESULTS

Three-hundred eighty-five patients were treated as follows: 123, 138, and 124 in iterations 1, 2, and 3, respectively. Baseline data was gathered from an additional 150 patients prior to protocol implementation. There was no difference in median age (6 vs 8 vs 7 vs 7 yr; p = 0.130), asthma severity score (9 vs 9 vs 9 vs 9; p = 0.073), or female gender (42% vs 41% vs 43% vs 48%; p = 0.757). Using statistical process control charts, the mean duration on continuous albuterol decreased from 24.9 to 17.5 hours and the mean hospital length of stay decreased from 76 to 49 hours. There was no difference in adverse events (0% vs 1% vs 4% vs 0%; p = 0.054) nor in readmissions (0% vs 0% vs 1% vs 2%; p = 0.254).

CONCLUSIONS

Implementation of a quality improvement protocol in critically ill patients with status asthmaticus was associated with a decrease in continuous albuterol duration and hospital length of stay.

Management of severe asthma exacerbation: guidelines from the Société Française de Médecine d'Urgence, the Société de Réanimation de Langue Française and the French Group for Pediatric Intensive Care and Emergencies

BACKGROUND

The French Emergency Medicine Society, the French Intensive Care Society and the Pediatric Intensive Care and Emergency Medicine French-Speaking Group edited guidelines on severe asthma exacerbation (SAE) in adult and pediatric patients.

RESULTS

The guidelines were related to 5 areas: diagnosis, pharmacological treatment, oxygen therapy and ventilation, patients triage, specific considerations regarding pregnant women. The literature analysis and formulation of the guidelines were conducted according to the Grade of Recommendation Assessment, Development and Evaluation methodology. An extensive literature research was conducted based on publications indexed in PubMed™ and Cochrane™ databases. Of the 21 formalized guidelines, 4 had a high level of evidence (GRADE 1+/-) and 7 a low level of evidence (GRADE 2+/-). The GRADE method was inapplicable to 10 guidelines, which resulted in expert opinions. A strong agreement was reached for all guidelines.

CONCLUSION

The conjunct work of 36 experts from 3 scientific societies resulted in 21 formalized recommendations to help improving the emergency and intensive care management of adult and pediatric patients with SAE.

Management of Hospitalized Asthmatic Children Before Transport

Asthmatic children are at risk for respiratory failure and should be appropriately treated before transport. The objectives were to find out if the Pediatric Advanced Life Support guidelines for asthma treatment were followed in the emergency department (ED); to determine if additional treatment during transport or within the first 2 hours of admission was needed; and to compare the management of intubated asthmatics by the ED, transport team, and the intensive care unit (ICU) physician. The records for children diagnosed with acute asthma over 7 years who were transported by the intensive care transport team were reviewed. The use of albuterol, steroids, oxygen, heliox, continuous positive airway pressure or bilevel positive airway pressure, and ventilator settings was recorded. Two hundred seventy-nine children were 7 years (age, 5 mo-17 y), and 62% were male. Eighty percent received oxygen, albuterol, and steroids in the ED. Heliox was initiated more often by the transport team when compared with the ED or hospital physician (77% vs. 7.7% vs. 15.3%, P < .0001). Forty-five were mechanically ventilated and were more likely to receive volume control (P < .0001) and higher rates (P = .007) in the ED than the ICU. We conclude that most children with acute asthma were treated with oxygen, albuterol, and steroids in the ED. If used, heliox was most likely started during transport. Intubated children were more likely to receive volume control with higher rates compared with lower rates and pressure control in the ICU.

A Critical Asthma Standardized Clinical and Management Plan Reduces Duration of Critical Asthma Therapy

BACKGROUND AND OBJECTIVE

Reduction of critical asthma management time can reduce intensive care utilization. The goal of this study was to determine whether a Critical Asthma Standardized Clinical Assessment and Management Plan (SCAMP) can decrease length of critical asthma management time.

METHODS

This retrospective study compared critical asthma management times in children managed before and after implementation of a Critical Asthma SCAMP. The SCAMP used an asthma severity score management scheme to guide stepwise escalation and weaning of therapies. The SCAMP guided therapy until continuous albuterol nebulization (CAN) was weaned to intermittent albuterol every 2 hours (q2h). Because the SCAMP was part of a quality improvement initiative in which all patients received a standardized therapy, informed consent was waived. The study was conducted in Medicine ICU and Intermediate Care Units in a tertiary care freestanding children's hospital. Children ≥2 years of age who had CAN initiated in the emergency department and were admitted to the Division of Medicine Critical Care with status asthmaticus were included. The time to q2h dosing from initiation of CAN was compared between the baseline and SCAMP cohorts. Adverse events were compared. The Mann-Whitney test was used for analysis; P values <.05 were considered statistically significant.

RESULTS

There were 150 baseline and 123 SCAMP patients eligible for analysis. There was a decrease in median time to q2h dosing after the SCAMP (baseline, 21.6 hours [interquartile range, 3.2-32.3 hours]; SCAMP, 14.2 hours [interquartile range, 9.0-23.1 hours]; P < .01). There were no differences in adverse events or readmissions.

CONCLUSIONS

A Critical Asthma SCAMP was effective in decreasing time on continuous albuterol.

Effects of a helium/oxygen mixture on individuals' lung function and metabolic cost during submaximal exercise for participants with obstructive lung diseases

BACKGROUND

Helium/oxygen therapies have been studied as a means to reduce the symptoms of obstructive lung diseases with inconclusive results in clinical trials. To better understand this variability in results, an exploratory physiological study was performed comparing the effects of helium/oxygen mixture (78%/22%) to that of medical air.

METHODS

The gas mixtures were administered to healthy, asthmatic, and chronic obstructive pulmonary disease (COPD) participants, both moderate and severe (6 participants in each disease group, a total of 30); at rest and during submaximal cycling exercise with equivalent work rates. Measurements of ventilatory parameters, forced spirometry, and ergospirometry were obtained.

RESULTS

There was no statistical difference in ventilatory and cardiac responses to breathing helium/oxygen during submaximal exercise. For asthmatics, but not for the COPD participants, there was a statistically significant benefit in reduced metabolic cost, determined through measurement of oxygen uptake, for the same exercise work rate. However, the individual data show that there were a mixture of responders and nonresponders to helium/oxygen in all of the groups.

CONCLUSION

The inconsistent response to helium/oxygen between individuals is perhaps the key drawback to the more effective and widespread use of helium/oxygen to increase exercise capacity and for other therapeutic applications.

Heliox inhalation therapy for bronchiolitis in infants

BACKGROUND

Bronchiolitis is the leading cause of hospitalisation among infants in high-income countries. Acute viral bronchiolitis is associated with airway obstruction and turbulent gas flow. Heliox, a mixture of oxygen and the inert gas helium, may improve gas flow through high-resistance airways and decrease the work of breathing. In this review, we selected trials that objectively assessed the effect of the addition of heliox to standard medical care for acute bronchiolitis.

OBJECTIVES

To assess heliox inhalation therapy in addition to standard medical care for acute bronchiolitis in infants with respiratory distress, as measured by clinical endpoints (in particular the rate of endotracheal intubation, the rate of emergency department discharge, the length of treatment for respiratory distress) and pulmonary function testing (mainly clinical respiratory scores).

SEARCH METHODS

We searched CENTRAL (2015, Issue 2), MEDLINE (1966 to March week 3, 2015), EMBASE (1974 to March 2015), LILACS (1982 to March 2015) and the National Institutes of Health (NIH) website (May 2009).

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs of heliox in infants with acute bronchiolitis.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed trial quality.

MAIN RESULTS

We included seven trials involving 447 infants younger than two years with respiratory distress secondary to viral bronchiolitis. All children were recruited from a paediatric intensive care unit (PICU; 378 infants), except in one trial (emergency department; 69 infants). All children were younger than two (under nine months in two trials and under three months in one trial). Positive tests for respiratory syncytial virus (RSV) were required for inclusion in five trials. The two other trials were carried out in the bronchiolitis seasons. Seven different protocols were used for inhalation therapy with heliox.When heliox was used in the PICU, we observed no significant reduction in the rate of intubation: risk ratio (RR) 2.73 (95% confidence interval (CI) 0.96 to 7.75, four trials, 408 infants, low quality evidence). When heliox inhalation was used in the emergency department, we observed no increase in the rate of discharge: RR 0.51 (95% CI 0.17 to 1.55, one trial, 69 infants, moderate quality evidence).There was no decrease in the length of treatment for respiratory distress: mean difference (MD) -0.19 days (95% CI -0.56 to 0.19, two trials, 320 infants, moderate quality evidence). However, in the subgroup of infants who were started on nasal continuous positive airway pressure (nCPAP) right from the start, because of severe respiratory distress, heliox therapy reduced the length of treatment: MD -0.76 days (95% CI -1.45 to -0.08, one trial, 21 infants, low quality evidence). No adverse events related to heliox inhalation were reported.We found that infants treated with heliox inhalation had a significantly lower mean clinical respiratory score in the first hour after starting treatment when compared to those treated with air or oxygen inhalation: MD -1.04 (95% CI -1.60 to -0.48, four trials, 138 infants, moderate quality evidence). This outcome had statistical heterogeneity, which remained even after removing the study using a standard high-concentration reservoir mask. Several factors may explain this heterogeneity, including first the limited number of patients in each trial, and the wide differences in the baseline severity of disease between studies, with the modified Wood Clinical Asthma Score (m-WCAS) in infants treated with heliox ranging from less than two to more than seven.

AUTHORS' CONCLUSIONS

Current evidence suggests that the addition of heliox therapy may significantly reduce a clinical score evaluating respiratory distress in the first hour after starting treatment in infants with acute RSV bronchiolitis. We noticed this beneficial effect regardless of which heliox inhalation protocol was used. Nevertheless, there was no reduction in the rate of intubation, in the rate of emergency department discharge, or in the length of treatment for respiratory distress. Heliox could reduce the length of treatment in infants requiring CPAP for severe respiratory distress. Further studies with homogeneous logistics in their heliox application are needed. Inclusion criteria must include a clinical severity score that reflects severe respiratory distress to avoid inclusion of children with mild bronchiolitis who may not benefit from heliox inhalation. Such studies would provide the necessary information as to the appropriate place for heliox in the therapeutic schedule for severe bronchiolitis.

Volatile anesthetics for status asthmaticus in pediatric patients: a comprehensive review and case series

Status asthmaticus is an acute, intractable asthma attack refractory to standard interventions that can lead to progressive respiratory failure. Successful management requires a fundamental understanding of the disease process, its clinical presentation, and proper evaluation. Treatment must be instituted early and is aimed at reversing the airway inflammation, bronchoconstriction, and hyper-reactivity that often lead to lower airway obstruction, impaired ventilation, and oxygenation. Most patients are effectively treated with standard therapy including beta2-adrenergic agonists and corticosteroids. Others necessitate adjunctive therapies and escalation to noninvasive ventilation or intubation. We will review the pathophysiology, evaluation, and treatment options for pediatric patients presenting with status asthmaticus with a particular focus on refractory status asthmaticus treated with volatile anesthetics. In addition, we include a proven approach to the management of these patients in the critical care setting, which requires close coordination between critical care and anesthesia providers. We present a case series of three patients, two of which have the longest reported cases of continuous isoflurane use in status asthmaticus. This series was obtained from a retrospective chart review and highlights the efficacy of the volatile anesthetic, isoflurane, in three pediatric patients with refractory life-threatening status asthmaticus.

The use of heliox in critical care

This paper reviews the medical use of helium oxygen mixture in obstructive airway disease in patients with croup, narrow endotracheal tubes (ETTs), respiratory distress syndrome, asthma, bronchiolitis, as well as patients with acute exacerbation of chronic obstructive pulmonary disease (COPD) and acute lung injury. In addition, some other indications of heliox use and some innovative methods of ventilation applied in pediatrics and adults are presented through review of the literature of current decade. Yet, to recommend heliox use seems to require more research based on clinical practice and observation through vaster and more robust investigations.

A review of the use of adjunctive therapies in severe acute asthma exacerbation in critically ill children

Asthma is a common and potentially life threatening childhood condition. Asthma involves not only chronic airway remodeling, but may also include frequent exacerbations resulting from bronchospasm, edema, and mucus production. In children with severe exacerbations, standard therapy with β2-agonists, anti-cholinergic agents, oxygen, and systemic steroids may fail to reverse the severe airflow obstruction and necessitate use of adjunctive therapies. These therapies include intravenous or inhaled magnesium, inhaled helium-oxygen mixtures, intravenous methylxanthines, intravenous β2-agonists, and intravenous ketamine. Rarely, these measures are not successful and following the initiation of invasive mechanical ventilation, inhaled anesthetics or extracorporeal life support may be required. In this review, we discuss the mechanisms and evidence for adjunctive therapies in the setting of severe acute asthma exacerbations in children.

Childhood asthma: a guide for pediatric emergency medicine providers

Pediatric asthma is a disease that is managed across outpatient physicians, hospitalists, critical care physicians, and emergency department (ED) physicians. Scoring systems may facilitate a rapid assessment of the child with asthma in the ED. Short-acting beta agonists are still the mainstay of therapy for acute exacerbations along with corticosteroids and ipratropium bromide. ED providers must also know the indications for noninvasive ventilation and intubation. Most patients can be treated and discharged from the ED after acute exacerbation, and should be given a plan for going home that provides educational material and emergency scenarios to help prevent future acute incidents.

The role of helium gas in medicine

The noble gas helium has many applications owing to its distinct physical and chemical characteristics, namely: its low density, low solubility, and high thermal conductivity. Chiefly, the abundance of studies in medicine relating to helium are concentrated in its possibility of being used as an adjunct therapy in a number of respiratory ailments such as asthma exacerbation, COPD, ARDS, croup, and bronchiolitis. Helium gas, once believed to be biologically inert, has been recently shown to be beneficial in protecting the myocardium from ischemia by various mechanisms. Though neuroprotection of brain tissue has been documented, the mechanism by which it does so has yet to be made clear. Surgeons are exploring using helium instead of carbon dioxide to insufflate the abdomen of patients undergoing laparoscopic abdominal procedures due to its superiority in preventing respiratory acidosis in patients with comorbid conditions that cause carbon dioxide retention. Newly discovered applications in Pulmonary MRI radiology and imaging of organs in very fine detail using Helium Ion Microscopy has opened exciting new possibilities for the use of helium gas in technologically advanced fields of medicine.

Pediatric status asthmaticus

Status asthmaticus is a frequent cause of admission to a pediatric intensive care unit. Prompt assessment and aggressive treatment are critical. First-line or conventional treatment includes supplemental oxygen, aerosolized albuterol, and corticosteroids. There are several second-line treatments available; however, few comparative studies have been performed and in the absence of good evidence-based treatments, the use of these therapies is highly variable and dependent on local practice and provider preference. In this article the pathophysiology and treatment of status asthmaticus is discussed, and the literature regarding second-line treatments is critically assessed to apply an evidence basis to the treatment of this severe disease.

Use of continuous positive airway pressure (CPAP) in acute viral bronchiolitis: a systematic review

INTRODUCTION

Continuous positive airway pressure (CPAP), used either alone or associated with heliox (CPAP-He), has become a popular therapeutic option for bronchiolitis. This systematic review assesses the impact of CPAP on endotracheal intubation, carbon dioxide pressure (PCO(2) ) and respiratory distress in patients with bronchiolitis.

METHODS

Systematic search including studies that used CPAP or CPAP-He in infants with bronchiolitis admitted to a PICU. Data analysis included descriptive statistics and the GRADE system.

RESULTS

Five CPAP (one crossover randomized controlled trial [RCT] and four before-after studies) and three CPAP-He (one quasi-RCT and two before-after) studies were included. CPAP was reported to reduce PCO(2) (-6.9 to -11.7 mmHg, respectively, P < 0.015), respiratory rate (-12 to -16 breaths/min after 2 hr, P < 0.01) and the modified Wood clinical asthma score (mWCAS, -2.2 points after 1 hr, P < 0.01). CPAP-He studies observed decreases in PCO(2) (-9.7 mmHg, P < 0.05), mWCAS (-2.12 points, P < 0.001), and respiratory rate (-8 to -13.7 breaths/min, P < 0.05) after 1 hr of treatment. Endotracheal intubation rates ranged from 0-12.5% (CPAP-He) to 17-27% (CPAP). After applying the GRADE system, the quality of evidence for a beneficial effect of CPAP and CPAP-He was classified as low.

CONCLUSIONS

The evidence supporting the use of CPAP to reduce PCO(2) and respiratory distress in bronchiolitis is of low methodological quality, and there is no conclusive evidence that CPAP reduces the need for intubation. No definitive conclusions could be drawn about the CPAP-He effect. Further research using higher quality methodology is needed to clarify the beneficial role of these interventions.

Application of medical gases in the field of neurobiology

Medical gases are pharmaceutical molecules which offer solutions to a wide array of medical needs. This can range from use in burn and stroke victims to hypoxia therapy in children. More specifically however, gases such as oxygen, helium, xenon, and hydrogen have recently come under increased exploration for their potential theraputic use with various brain disease states including hypoxia-ischemia, cerebral hemorrhages, and traumatic brain injuries. As a result, this article will review the various advances in medical gas research and discuss the potential therapeutic applications and mechanisms with regards to the field of neurobiology.

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

OBJECTIVES

To review articles relevant to the field of pediatric respiratory disease that were published after the 2008 Rogers' Textbook of Pediatric Intensive Care.

DATA SOURCES

The authors searched the PubMed database (http://www.ncbi.nlm.nih.gov/sites/entrez) from the National Library of Medicine for citations from the pediatric and adult literature relevant to pediatric status asthmaticus, bronchiolitis, pneumonia, acute lung injury, acute respiratory distress syndrome, and neonatal respiratory failure. The authors also searched the reference lists of key primary publications and recent review articles, and queried the National Institutes of Health's ClinicalTrials.gov Web site (www.clinicaltrials.gov) to obtain information about ongoing clinical trials for acute lung injury. The authors had knowledge of new publications in the field of respiratory monitoring, which were considered for inclusion in the review.

STUDY SELECTION AND DATA EXTRACTION

The authors reviewed the promising articles and the decision to include any article in the review was based on its potential to inform pediatric intensive care practice or future research.

DATA SYNTHESIS

Articles in six categories were selected for inclusion: status asthmaticus, bronchiolitis, pneumonia, acute lung injury/acute respiratory distress syndrome, respiratory monitoring, and neonatal respiratory failure.

CONCLUSIONS

There have been important new developments relevant to the pathogenesis and management of pediatric respiratory diseases. In particular, new insights into the causal pathways of respiratory syncytial virus-induced airways disease can potentially lead to novel therapies. Computed tomography imaging of the injured lung during mechanical ventilation has opened new avenues for future research directed at testing new treatments in acute lung injury subpopulations defined according to lung mechanics. Promising new monitoring techniques may play a supporting role in the conduct of these studies. Finally, evidence from the neonatal literature recently has shown how the course and future consequences of respiratory failure in this population may be modified through more widespread use of noninvasive support.

Use of heliox in the management of neonates with meconium aspiration syndrome

BACKGROUND

Helium-oxygen mixture (heliox) ventilation has been known as an alternative treatment in patients with airway obstruction. Because of the physical properties of heliox, mechanical ventilation with this gas mixture may offer advantages in the management of respiratory failure associated with meconium aspiration syndrome (MAS).

OBJECTIVES

The purpose of this pilot study was to assess the effect of short-term mechanical ventilation with heliox in newborns with MAS on vital signs, oxygenation, acid-base balance and respiratory function parameters.

METHODS

The study was carried out in newborns with respiratory failure requiring mechanical ventilation due to MAS. Eight patients were ventilated using pressure-controlled synchronized intermittent mandatory ventilation. Parameters of respiratory function, oxygenation, acid-base balance and vital signs were recorded at baseline, then twice during 1 h of heliox ventilation and finally twice during 1 h after switching back to air-oxygen ventilation.

RESULTS

Mechanical ventilation with heliox did not affect vital signs and the infants' clinical condition remained stable during the study. Heliox ventilation was associated with a nonsignificant increase in tidal volume, minute ventilation and peak expiratory flow rate values. Mechanical ventilation with heliox allowed the use of significantly lower FiO(2), with a significant decrease in alveolar-arterial oxygen tension difference and a decrease in the oxygenation index which was not statistically significant. There was also a significant increase in the PaO(2)/FiO(2) ratio during heliox ventilation.

CONCLUSIONS

Ventilation with a helium and oxygen mixture had a positive effect on the selected parameters of oxygenation, while its effects on other respiratory parameters were relatively small.

Acute severe asthma: new approaches to assessment and treatment

The precise definition of a severe asthmatic exacerbation is an issue that presents difficulties. The term 'status asthmaticus' relates severity to outcome and has been used to define a severe asthmatic exacerbation that does not respond to and/or perilously delays the repetitive or continuous administration of short-acting inhaled beta(2)-adrenergic receptor agonists (SABA) in the emergency setting. However, a number of limitations exist concerning the quantification of unresponsiveness. Therefore, the term 'acute severe asthma' is widely used, relating severity mostly to a combination of the presenting signs and symptoms and the severity of the cardiorespiratory abnormalities observed, although it is well known that presentation does not foretell outcome. In an acute severe asthma episode, close observation plus aggressive administration of bronchodilators (SABAs plus ipratropium bromide via a nebulizer driven by oxygen) and oral or intravenous corticosteroids are necessary to arrest the progression to severe hypercapnic respiratory failure leading to a decrease in consciousness that requires intensive care unit (ICU) admission and, eventually, ventilatory support. Adjunctive therapies (intravenous magnesium sulfate and/or others) should be considered in order to avoid intubation. Management after admission to the hospital ward because of an incomplete response is similar. The decision to intubate is essentially based on clinical judgement. Although cardiac or respiratory arrest represents an absolute indication for intubation, the usual picture is that of a conscious patient struggling to breathe. Factors associated with the increased likelihood of intubation include exhaustion and fatigue despite maximal therapy, deteriorating mental status, refractory hypoxaemia, increasing hypercapnia, haemodynamic instability and impending coma or apnoea. To intubate, sedation is indicated in order to improve comfort, safety and patient-ventilator synchrony, while at the same time decrease oxygen consumption and carbon dioxide production. Benzodiazepines can be safely used for sedation of the asthmatic patient, but time to awakening after discontinuation is prolonged and difficult to predict. The most common alternative is propofol, which is attractive in patients with sudden-onset (near-fatal) asthma who may be eligible for extubation within a few hours, because it can be titrated rapidly to a deep sedation level and has rapid reversal after discontinuation; in addition, it possesses bronchodilatory properties. The addition of an opioid (fentanyl or remifentanil) administered by continuous infusion to benzodiazepines or propofol is often desirable in order to provide amnesia, sedation, analgesia and respiratory drive suppression. Acute severe asthma is characterized by severe pulmonary hyperinflation due to marked limitation of the expiratory flow. Therefore, the main objective of the initial ventilator management is 2-fold: to ensure adequate gas exchange and to prevent further hyperinflation and ventilator-associated lung injury. This may require hypoventilation of the patient and higher arterial carbon dioxide (PaCO(2)) levels and a more acidic pH. This does not apply to asthmatic patients intubated for cardiac or respiratory arrest. In this setting the post-anoxic brain oedema might demand more careful management of PaCO(2) levels to prevent further elevation of intracranial pressure and subsequent complications. Monitoring lung mechanics is of paramount importance for the safe ventilation of patients with status asthmaticus. The first line of specific pharmacological therapy in ventilated asthmatic patients remains bronchodilation with a SABA, typically salbutamol (albuterol). Administration techniques include nebulizers or metered-dose inhalers with spacers. Systemic corticosteroids are critical components of therapy and should be administered to all ventilated patients, although the dose of systemic corticosteroids in mechanically ventilated asthmatic patients remains controversial. Anticholinergics, inhaled corticosteroids, leukotriene receptor antagonists and methylxanthines offer little benefit, and clinical data favouring their use are lacking. In conclusion, expertise, perseverance, judicious decisions and practice of evidence-based medicine are of paramount importance for successful outcomes for patients with acute severe asthma.

Heliox inhalation therapy for bronchiolitis in infants

BACKGROUND

Acute viral bronchiolitis is associated with airway obstruction and turbulent gas flow. Heliox, a mixture of oxygen and the inert gas helium, may improve gas flow through high-resistance airways and decrease the work of breathing.

OBJECTIVES

To assess heliox in addition to standard medical care for acute bronchiolitis in infants.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2009, issue 2), which includes the Cochrane Acute Respiratory Infections (ARI) Group's Specialised Register, MEDLINE (1966 to June 2009), EMBASE (June 2009), LILACS (May 2009) and the NIH web site (May 2009).

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs of heliox in infants with acute bronchiolitis.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed trial quality. We pooled data from individual trials.

MAIN RESULTS

We included four trials involving 84 infants under two years of age with respiratory distress secondary to bronchiolitis caused by respiratory syncytial virus (RSV) and requiring paediatric intensive care unit (PICU) hospitalisation. We found that infants treated with heliox inhalation had a significantly lower mean clinical respiratory score in the first hour after starting treatment when compared to those treated with air or oxygen inhalation (mean difference (MD) -1.15, 95% confidence interval (CI) -1.98 to -0.33, P = 0.006, n = 69). There was no clinically significant reduction in the rate of intubation (risk ratio (RR) 1.38, 95% CI 0.41 to 4.56, P = 0.60, n = 58), in the need for mechanical ventilation (RR 1.11, 95% CI 0.36 to 3.38, P = 0.86, n = 58), or in the length of stay in a PICU (MD = -0.15 days, 95% CI -0.92 to 0.61, P = 0.69, n = 58). No adverse events related to heliox inhalation were reported.

AUTHORS' CONCLUSIONS

Current evidence suggests that the addition of heliox therapy may significantly reduce a clinical score evaluating respiratory distress in the first hour after starting treatment in infants with acute RSV bronchiolitis. Nevertheless, there was no reduction in the rate of intubation, in the need for mechanical ventilation, or in the length of PICU stay. Further studies with homogeneous logistics in their heliox application are needed. Such studies would provide necessary information as to the appropriate place for heliox in the therapeutic schedule for severe bronchiolitis.

The role of heliox in paediatric respiratory disease

Helium-oxygen (heliox) gas mixtures have been studied for over 70 years as an adjunctive therapy for airway obstruction in a variety of respiratory diseases. The medical use of heliox is based on the physical properties of helium as its low density makes it advantageous in promoting more efficient flow through narrowed passages. Clinical evidence of the efficacy of heliox in treating paediatric respiratory diseases is increasing in the medical literature. This article consists of a comprehensive review of the literature investigating the utility of heliox in the treatment of paediatric respiratory disorders, including upper and lower airway obstruction, mechanical ventilation, and aerosol delivery.

Heliox for croup in children

BACKGROUND

Croup, a common acute clinical syndrome in children up to the age of six, is thought to be triggered by a viral infection, and is characterised by a varying degree of respiratory distress due to upper airway inflammation and oedema of the subglottic mucosa. Corticosteroids, now part of the standard treatment for croup, improve symptoms but it takes time for their full effect to be achieved. Meanwhile, the child remains at risk of deterioration and developing respiratory failure necessitating emergency intubation and ventilation. Helium-oxygen (heliox) inhalation has been successful in the treatment of upper airway obstruction. Anecdotal evidence suggests that heliox relieves respiratory distress in children, but it remains unclear whether there is robust evidence to support the implementation of heliox for croup into clinical practice.

OBJECTIVES

To examine the effect of heliox on relieving symptoms and distress, determined by a croup score (a tool for measuring the severity of croup) or clinical assessment variables, through comparisons with placebo or active treatment(s) in children with croup.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2009, issue 2) which contains the Acute Respiratory Infections (ARI) Group's Specialised Register; MEDLINE (1950 to June week 3 2009); EMBASE (1974 to 2009 week 25) and CINAHL (1982 to June 2009).

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs comparing the effect of helium-oxygen mixtures with placebo or any active treatment in children with croup.

DATA COLLECTION AND ANALYSIS

Both authors independently identified and assessed citations for relevance. We assessed included trials for risk of bias using allocation concealment, blinding of intervention, completeness of outcome data, selective outcome reporting and other potential source of bias. We calculated mean differences for continuous data. We presented data not suitable for statistical analysis as descriptive data.

MAIN RESULTS

Two eligible RCTs were included (22 intervention, 22 controls). Neither trial compared heliox inhalation with placebo. One study compared heliox with 30% humidified oxygen whilst the other compared it to 100% oxygen with additional racaemic epinephrine nebulisation. There was no significant difference in change of croup score between intervention and control groups.

AUTHORS' CONCLUSIONS

At present there is a lack of evidence to establish the effect of heliox inhalation in the treatment of croup in children. A methodologically well-designed and adequately powered RCT is needed to assess whether there is a role for heliox therapy in the management of children with croup.

Heliox in airway management

Helium-oxygen ("heliox") mixtures have been used for decades in the treatment of various respiratory problems ranging from acute upper airway obstructions to lower airway derangements, such as asthma and exacerbations of chronic bronchitis. This review presents a brief history of helium and helium-oxygen mixtures and their potential clinical uses, summarizes the results of past research into heliox in respiratory applications, explains the physiology of heliox, and presents more recent literature relating to heliox in the clinical setting.

[Heliox-driven bronchodilator nebulization in the treatment of infants with bronchiolitis]

INTRODUCTION

Heliox is a helium-oxygen mixture which improves laminar flow and decreases airway resistance and the work of breathing. The aim of this study was to assess the effects of salbutamol or epinephrine nebulization driven by heliox in infants with moderate-to-severe bronchiolitis.

MATERIALS AND METHODS

This prospective, observational, interventional, controlled and randomized study included ninety-six children who came to our pediatric emergency department with first episode of moderate-to-severe bronchiolitis. The patients were randomized to receive salbutamol or epinephrine nebulized with either oxygen (control group) or heliox (70% helium and 30% oxygen) as the driving gas. Heart rate, respiratory rate, pulse oximetry oxygen saturation and clinical score were measured before and after the treatment period. We also reported hospitalization rates and the number of patients who returned to the emergency department in the following seventy two hours.

RESULTS

There were no significant differences between both groups. The only statistically significant difference was that, in the heliox group, patients with severe bronchiolitis needed a lower number of nebulizations than infants in the control group.

CONCLUSIONS

According to our study, heliox-driven salbutamol or epinephrine is not an effective therapy in patients with acute bronchiolitis.

Novel therapies for children with severe asthma

PURPOSE OF REVIEW

Novel therapies, such as a heliox gaseous mixture and noninvasive bilevel positive pressure ventilation, are being utilized in the treatment of the patient with severe asthma who is unresponsive to conventional medical management. Aggressive treatment may prevent intubation and its untoward complications.

RECENT FINDINGS

Both heliox and bilevel positive pressure ventilation have demonstrated clinical improvement in studies of patients refractory to standard care, both in adults and children.

SUMMARY

The studies in children are limited but show promise, especially when these therapies are used early in the treatment course and in certain subsets of patients.

The uses of helium and xenon in current clinical practice

The noble gases have always been an enigma. Discovered late in the history of chemistry and in seemingly small quantities in our atmosphere, they are some of the most unreactive elements known. However, despite being extremely inert, the noble gases (helium, neon, argon, krypton, xenon and radon) have found diverse and ever expanding applications in medicine. Of all of them, the gases that have found the greatest number of uses in the field of anaesthesia and related specialties are helium and xenon. This review focuses on the history of the discovery of both gases, their unique physicochemical properties and describes their uses in clinical practice with particular emphasis on those applicable to anaesthesia.

Pediatric anesthesia and recent developments in asthma in children

Asthma is a chronic inflammatory disease and the physiological consequence is bronchial hyperresponsiveness to different stimuli. With the worldwide increase in the prevalence of asthma, an increased number of asthmatics are likely to require anesthesia for surgical procedures. Recent investigations described the role played by different environmental agents in asthma, and clarified assessment and management strategies which can be applied to anesthesia in order to decrease the morbidity related to perioperative bronchospasm in children with asthma.

Ventilatory management in patients with chronic airflow obstruction

Mechanical ventilatory support allows patients who have CAO to gain time for pharmacologic treatment to work and to avoid and/or recover from respiratory muscle fatigue. The cornerstone to avoiding associated morbidity with mechanical ventilation in these patients is to prevent dynamic hyperinflation of the lung by limiting minute ventilation and maximizing time for expiration and by inducing synchronization between the patient and mechanical ventilator. When mechanical ventilation is necessary, NPPV should be considered first, whenever possible, in these patients. Patients who have CAO requiring mechanical ventilatory support have an increased risk of death following such an event. Therefore, careful followup is needed after hospital discharge.

Eficacia del tratamiento con heliox en niños con insuficiencia respiratoria

OBJECTIVE

To analyze response to heliox therapy in critically ill infants and children with upper and/or lower airway respiratory insufficiency.

PATIENTS AND METHODS

Sixty-five patients, aged between 12 days and 8 years old, treated with heliox through facial mask, nasal prongs or non-invasive ventilation were studied. Diagnoses were bronchiolitis (25), upper postextubation respiratory insufficiency (19), respiratory insufficiency after airway surgery (14), and croup-laryngotracheomalacia (7). Response to heliox treatment was measured by the change in clinical scores, respiratory rate, heart rate, pulse oximetry, blood gas analysis, and the need for non-invasive and invasive mechanical ventilation.

RESULTS

Fifty-four patients (83.1 %) improved after heliox therapy, with statistically significant differences in clinical score (from 8.7 to 5.5), respiratory rate (from 51.4 to 38.8 rpm), and heart rate (from 161.6 to 145.6 bpm). No changes were observed in saturation or blood gas analysis. After heliox therapy, 29.8 % of patients required non-invasive ventilation and 26.5 % required intubation. Patients with bronchiolitis and those aged less than 1 year had a lesser response to heliox therapy and more frequently required non-invasive ventilation. No significant differences were found in intubation requirements. No adverse effects were observed.

CONCLUSIONS

Heliox therapy improved clinical scores in infants and children with upper and lower airway respiratory insufficiency, but a significant percentage of patients needed non-invasive or invasive mechanical ventilation.

Room air entrainment during beta-agonist delivery with heliox

Studies of the efficacy of heliox in patients with severe asthma have shown mixed results. Among the factors that are responsible for variable outcomes, the failure of heliox delivery systems to prevent room air entrainment (RAE) during beta-agonist delivery is probably the most critical. While keeping the rotameter flow rate (FR) of heliox mixed 70:30 to a nebulizer at 10 L/min, the FR of heliox from a second gas source to a T-connector (TC) was increased during the delivery of the beta-agonist with a conventional T-nebulizer delivery system (TNDS). A negative peak inspiratory flow (pneumotachometer reading) or a helium concentration of < 70% (quadralizer reading) were indicators of RAE. RAE was tested during spontaneous tidal breathing and acute asthma. A rotameter FR of 10 L/m to the nebulizer with no flow from a second gas source to a TC (conventional TNDS) resulted in a significant drop in helium concentration during tidal breathing (46.2%) and acute asthma (27.5%) due to RAE. This degree of helium dilution can negate the beneficial effects of heliox to lung mechanics almost completely. A rotameter FR of 10 L/m each to a nebulizer and a TC resulted in a helium concentration 69.8% during tidal breathing (no RAE), but 49% (significant RAE) during asthma events. A rotameter FR of 15 L/m (pressure regulator setting, 100 lbs per square inch) to a TC, while maintaining a rotameter FR of 10 L/m to a nebulizer prevented RAE during asthma (helium concentration, 69.9%). Conventional TNDS may be used to deliver the beta-agonist with heliox during asthma without RAE.

Heliox for nonintubated acute asthma patients

BACKGROUND

Helium and oxygen mixtures (heliox), have been used sporadically in respiratory medicine for decades. Their use in acute respiratory emergencies such as asthma has been the subject of considerable debate. Despite the lapse of more than 60 years since it was first proposed, the role of heliox in treating patients with severe acute asthma remains unclear.

OBJECTIVES

To determine the effect of the addition of heliox to standard medical care on the course of acute asthma, as measured by pulmonary function testing and clinical endpoints.

SEARCH STRATEGY

Randomised controlled trials were identified from the Cochrane Airways Group Specialised Register. In addition, we contacted primary authors and experts and searched reference lists of articles. Searches are current to August 2005.

SELECTION CRITERIA

1) randomised, single or double blind, controlled trials; 2) children or adults with a clinical diagnosis of acute asthma seen in emergency departments or equivalent acute care settings; and 3) compared treatment with inhaled heliox to placebo (oxygen or air).

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the studies for inclusion and quality assessment; disagreement was resolved by a third review author and consensus.

MAIN RESULTS

This review has been updated in 2006 to include four new trials giving atotal of ten trials involving 544 acute asthma patients. Seven studies involved adults and three studies dealt solely with children. Three were assessed as high quality (Jadad score > 3). Pulmonary function tests were recorded during heliox administration (15 to 60 min). Pooling of the eight trials contributing data to this review showed no significant group differences (standardised mean differences -0.28; 95% confidence interval (CI) -0.56 to 0.01). There was significant heterogeneity among the studies. Heliox use did improve pulmonary function only in the subgroup of patients with the most severe baseline pulmonary function impairment; however, this conclusion is based on a small number of studies. There were no significant differences between groups when adults versus children, and high versus low heliox dose studies were compared. Finally, at the end of treatment, participants treated with heliox showed no significant different risk of admission to hospital (RR 0.83 (95%CI 0.66 to 1.08, P = 0.17, I(2) = 0%).

AUTHORS' CONCLUSIONS

The existing evidence does not provide support for the administration of helium-oxygen mixtures to all ED patients with acute asthma. At this time, heliox treatment does not have a role to play in the initial treatment of patients with acute asthma. Nevertheless, new evidence suggests certain beneficial effects in patients with more severe obstruction. Since these conclusions are based upon between-group comparisons and small studies, they should be interpreted with caution.

Effect of Heliox on Albuterol Delivery by Metered-Dose Inhaler in Pediatric In Vitro Models of Mechanical Ventilation

STUDY OBJECTIVE

To determine the effect of varying concentrations of heliox, a mixture of helium and oxygen, on albuterol delivery administered by metered-dose inhaler (MDI) in pediatric mechanically ventilated models.

DESIGN

Prospective in vitro laboratory study.

SETTING

University-affiliated research laboratory.

MODELS

The lungs of a 10-kg infant and 30-kg child receiving humidified pressure-regulated volume-controlled ventilation were simulated. The infant settings were an endotracheal tube (ETT) of 4.0 mm, tidal volume of 150 ml, positive end-expiratory pressure of 2 cm H(2)O, rate of 20 breaths/minute, inspiratory time of 0.7 second; the child settings were an ETT of 6.0 mm, tidal volume of 450 ml, positive end-expiratory pressure of 2 cm H(2)O, rate of 16 breaths/minute, and inspiratory time of 0.8 second.

MEASUREMENTS AND MAIN RESULTS

Ten albuterol MDI canisters with chlorofluorocarbon propellants were each actuated once sequentially (total dose 1000 mug) with a commercially available aerosol holding chamber. Albuterol was collected onto a filter proximal to a lung simulator. The filter was rinsed, and concentrations were determined by high-performance liquid chromatography. In the infant model, heliox mixtures of 70:30, 60:40, and 50:50 were compared with nitrogen:oxygen (N(2):O(2)) mixtures in the same ratios. The effect of the 70:30 mixtures was also explored in a child model. Each gas mixture was tested 5 times. At all three ratios, albuterol delivery to the end of the ETT was improved with heliox compared with N(2):O(2) (approximately 7% vs 3-4%, p<0.0001, one-way analysis of variance [ANOVA] with a Bonferroni correction for multiple comparisons). No significant difference was noted in mean percentage albuterol delivery among the varying ratios of heliox studied. By two-way ANOVA, significantly greater albuterol delivery was noted with 70:30 heliox compared with 70:30 N(2):O(2) (7-8% vs 3%, p<0.0001), with no significant difference between the infant and child model (p=0.21). The gas mixture, model, and interaction of the two explained 88% of the variability in mean percentage albuterol delivery.

CONCLUSION

Heliox increased albuterol delivery administered by MDI to the end of the ETT in these in vitro pediatric models of mechanical ventilation. Further studies are needed to determine if the improved albuterol delivery with heliox enhances clinical response in infants and children needing mechanical ventilation.

Clinical effects of heliox administration for acute bronchiolitis in young infants

OBJECTIVE

To assess the effect of heliox, a helium-oxygen mixture, on respiratory distress symptoms in young infants.

DESIGN

Prospective, randomized, double-blind study.

SETTING

Pediatric ICU (PICU) of a university hospital.

PATIENTS

Twenty infants, all < 3 months old, admitted to the PICU with moderate-to-severe acute respiratory syncytial virus bronchiolitis.

INTERVENTIONS

All infants were randomly and blindly assigned to inhale either heliox or an air-oxygen mixture (airox) for 1 h under an oxyhood.

MEASUREMENTS AND RESULTS

After 1 h, the respiratory distress score was significantly lower in the heliox group compared with the airox group (3.05 vs 5.5, p < 0.01), with a significant reduction in accessory muscles use (p < 0.05) and expiratory wheezing (p < 0.01). In contrast, inspiratory breath sounds and cyanosis did not significantly differ between groups. The ex-premature infants of the heliox group had a higher respiratory distress score at baseline compared with the term infants of this group (5.8 vs 5.2, p < 0.05) and a comparable decrease in the score at 60 min.

CONCLUSIONS

In young infants, even those born prematurely, heliox breathing induced a rapid reduction in accessory muscles use and expiratory wheezing. Further studies are needed to confirm the decreased respiratory muscle work of breathing during heliox inhalation in this population.

Current management of status asthmaticus in the pediatric ICU

Status asthmaticus (SA) in the pediatric ICU (PICU) can progress to a life-threatening emergency. The goal of management is to improve hypoxemia, improve bronchoconstriction, and decrease airway edema through the administration of continuous nebulized beta2 adrenergic agonist with intermittent anticholinergics, corticosteroids, and oxygen. Adjunctive therapies, such as magnesium, methylxanthines, intravenous beta-agonists, heliox, and noninvasive ventilation should be considered in the child who fails to respond to initial therapies. The restoration of adequate pulmonary functions, resolution of airway obstruction, and avoidance of mechanical ventilation should guide management. This article reviews the pathophysiology, assessment, and management of the child who has SA in the PICU to provide the critical care nurse with current information to facilitate optimal care.

A prototype infant incubator for heliox therapy

Heliox (Hx) gas has been shown to improve pulmonary function in infants, but methods for its delivery are invasive and problematic. To this end, we modified an Isolette (Hill-Rom Air-Shields) infant incubator (Hxl) to deliver Hx respiratory gas mixtures noninvasively while providing thermal stability for neonatal care in the Neonatal Intensive Care Unit (NICU). In vitro tests and in vivo animal studies were performed to compare the original design specifications and established baseline performance criteria for the Hxl design. The experimental environments at 50% and 80% relative humidity (RH) consisted of helium (He) with 21% and 50% O2 and control (C) of 21% and 50% O2 with the balance nitrogen (N). Elapsed times to steady state (SS) and recovery time back to SS (OCDss) due to opening and closing the door were recorded for each variable. All rabbits survived and appeared comfortable during all experimental conditions. These data show that the newly designed Isolette provides similar thermal, O2, CO2, and RH responses as the control incubator. Based on these positive safety/efficacy studies, study of the therapeutic impact of Hxl care on neonatal growth and development is in progress.

Albuterol nebulized in heliox in the initial ED treatment of pediatric asthma: a blinded, randomized controlled trial

OBJECTIVE

A prospective blinded, randomized controlled trial was undertaken to compare the initial response of albuterol nebulized in heliox or control in the treatment of moderately severe asthma in children presenting to a pediatric ED.

METHODS

Patients were randomized to receive heliox (n = 20) or control (n = 21). The primary outcome was to compare a modified dyspnea index score at 10 and 20 minutes after randomization. Secondary outcomes were to determine if heliox decreased admission rates or endotracheal intubation.

RESULTS

There was no statistically significant difference found at 10 or 20 minutes after randomization with heliox (P = .169 and P = .062, respectively). No statistical difference in admission rate was found, and no patients required endotracheal intubation in either group.

CONCLUSIONS

Our results demonstrate that albuterol nebulized with heliox offered no clinical benefit over standard therapy in the initial treatment of moderately severe asthma in the ED.

Heliox administration in the pediatric intensive care unit: an evidence-based review

OBJECTIVE

To provide a comprehensive, evidence-based review of helium-oxygen gas mixtures (heliox) in the management of pediatric respiratory diseases.

DATA SOURCE

A thorough, computerized bibliographic search of the preclinical and clinical literature regarding the properties of helium and its application in pediatric respiratory disease states.

DATA SYNTHESIS

After an overview of the potential benefits and technical aspects of helium-oxygen gas mixtures, the role of heliox is addressed for asthma, aerosolized medication delivery, upper airway obstruction, postextubation stridor, croup, bronchiolitis, and high-frequency ventilation. The available data are objectively classified based on the value of the therapy or intervention as determined by the study design from which the data are obtained.

CONCLUSIONS

Heliox administration is most effective during conditions involving density-dependent increases in airway resistance, especially when used early in an acute disease process. Any beneficial effect of heliox should become evident in a relatively short period of time. The medical literature supports the use of heliox to relieve respiratory distress, decrease the work of breathing, and improve gas exchange. No adverse effects of heliox have been reported. However, heliox must be administered with vigilance and continuous monitoring to avoid technical complications.

Patterns of helium-oxygen (heliox) usage in the critical care environment

The objective of this study was to describe the patterns of heliox use in critical care units of an academic medical center. The design was a prospective case series involving 7 critical care units of an academic medical center. All patients receiving heliox therapy over a 4-year period were studied, with prospective recording of patient demographics and the location, mode, indication for, and duration of heliox use. Use pattern comparisons based on anatomic location (upper vs lower airway) and age group (pediatric vs adult) were performed by alpha(2) analysis and unpaired Student t test. Eighty-nine patients, aged 17.4 +/- 20.9 years, received heliox for 30.5 +/- 44.6 hours on 92 occasions. Pediatric (</= 18 years) applications accounted for 72.8% of heliox use. Use was greater in frequency and scope during the final 2 study years, particularly in adults. Applications were split between upper airway (47%) and lower airway (53%) disorders. Airway manipulation was required in more adults (7/16) than in children (3/27) with upper airway obstruction (P < .05). The use patterns mirrored current literature emphases on postextubation stridor and asthma. This is the first description of heliox use patterns in the tertiary care critical care environment. Heliox use may be as dependent on practitioner experience as on published data. As a benign and relatively inexpensive therapy, heliox use should continue to be attractive, although ongoing study regarding efficacy in a number of settings is indicated.