Heliox in respiratory failure secondary to bronchiolitis: a new therapy

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.

The potential of heliox as a therapy for acute respiratory distress syndrome in adults and children: a descriptive review

BACKGROUND

In neonatal respiratory distress syndrome (RDS) and acute RDS (ARDS) mechanical ventilation is often necessary to manage hypoxia, whilst protecting the lungs through lower volume ventilation and permissive hypercapnia. Mechanical ventilation can, however, induce or aggravate the lung injury caused by the respiratory distress. Helium, in a gas mixture with oxygen (heliox), has a low density and can reduce the flow in narrow airways and allow for lower driving pressures.

OBJECTIVES

The aim of this study was to review preclinical and clinical studies of the use of heliox ventilation in acute lung injury associated with respiratory failure.

METHODS

A systematic search was executed in the PubMed and EMBASE databases, with search terms referring to ARDS or an acute lung injury condition associated with respiratory failure and the corresponding intervention.

RESULTS

A total of 576 papers were retrieved. After the majority had been excluded 20 papers remained, of which 6 articles described animal models (3 paediatric; 3 adult animal models) and 14 were clinical studies, of which 12 described paediatric patient populations and 2 adult patient populations. In both paediatric and adult animal models, heliox improved gas exchange while allowing for less invasive ventilation in a wide variety of models using different ventilation modes. Clinical studies show a reduction in the work of breathing during heliox ventilation, with a concomitant increase in pH and decrease in PaCO2 levels compared to oxygen ventilation.

CONCLUSIONS

Although evidence so far is limited, there may be a rationale for heliox ventilation in ARDS as an intervention to improve ventilation and reduce the work of breathing.

Heliox therapy in bronchiolitis: phase III multicenter double-blind randomized controlled trial

BACKGROUND AND OBJECTIVE

Supportive care remains the mainstay of therapy in bronchiolitis. Earlier studies suggest that helium-oxygen therapy may be beneficial, but evidence is limited. We aimed to compare efficacy of 2 treatment gases, Heliox and Airox (21% oxygen + 79% helium or nitrogen, respectively), on length of hospital treatment for bronchiolitis.

METHODS

This was a multicenter randomized blinded controlled trial of 319 bronchiolitic infant subjects randomly assigned to either gas; 281 subjects completed the study (140 Heliox, 141 Airox), whose data was analyzed. Treatment was delivered via facemask (nasal cannula, if the facemask intolerant) ± continuous positive airway pressure (CPAP). Severe bronchiolitics received CPAP from the start. Primary end point was length of treatment (LoT) required to alleviate hypoxia and respiratory distress. Secondary end-points were proportion of subjects needing CPAP; CPAP (LoT); and change in respiratory distress score.

RESULTS

Analysis by intention to treat (all subjects); median LoT (inter-quartile range, days): Heliox 1.90 (1.08-3.17), Airox 1.87 (1.11-3.34), P = .41. Facemask tolerant subgroup: Heliox 1.46 (0.85-1.95), Airox 2.01 (0.93-2.86), P = .03. Nasal cannula subgroup: Heliox 2.51 (1.21-4.32), Airox 2.81 (1.45-4.78), P = .53. Subgroup started on CPAP: Heliox 1.55 (1.38-2.01), Airox 2.26 (1.84-2.73), P = .02. Proportion of subjects needing CPAP: Heliox 17%, Airox 19%, O.R. 0.87 (0.47-1.60), P = .76. Heliox reduced respiratory distress score after 8 hours (mixed models estimate, -0.1298; P < .001). The effect was greater for facemask compared with nasal cannula (mixed models estimate, 0.093; P = .04).

CONCLUSIONS

Heliox therapy does not reduce LoT unless given via a tight-fitting facemask or CPAP. Nasal cannula heliox therapy is ineffective.

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.

A double-blind, randomised, controlled Phase II trial of Heliox28 gas mixture in lung cancer patients with dyspnoea on exertion

Helium has a low density and the potential of reducing the work of breathing and improving alveolar ventilation when replacing nitrogen in air. A Phase II, double-blind, randomised, prospective, controlled trial was undertaken to assess whether Heliox28 (72% He/28% O₂) compared with oxygen-enriched air (72% N₂/28% O₂) or medical air (78.9% N₂/21.1% O₂) could reduce dyspnoea and improve the exercise capability of patients with primary lung cancer and dyspnoea on exertion (Borg >3). A total of 12 patients (seven male, five female patients, age 53–78) breathed the test gases in randomised order via a facemask and inspiratory demand valve at rest and while performing 6-min walk tests. Pulse oximetry (SaO₂) was recorded continuously. Respiratory rate and dyspnoea ratings (Borg and VAS) were taken before and immediately post-walk. Breathing Heliox28 at rest significantly increased SaO₂ compared to oxygen-enriched air (96±2 cf. 94±2, P<0.01). When compared to medical air, breathing Heliox28 but not oxygen-enriched air gave a significant improvement in the exercise capability (P<0.0001), SaO₂ (P<0.05) and dyspnoea scores (VAS, P<0.05) of lung cancer patients.

Current treatment for acute viral bronchiolitis in infants

This paper provides an update and critical review of available data on the treatment of acute viral bronchiolitis in previously healthy infants, with special focus on new or promising therapies. The main potential benefits of medical assistance in these patients reside in the careful monitoring of their clinical status, the maintenance of adequate hydration and oxygenation, the preservation of the airway opened and cleared of secretions and the option to perform parental education. There is no convincing evidence that any other form of therapy will reliably provide beneficial effects in infants with bronchiolitis and currently, any treatment beyond supportive care should be prescribed on a case-by-case basis with watchful appraisal of its effects. Therapies such as ribavirin, IFN, vitamin A, antibiotics, mist therapy or anticholinergics, have not demonstrated any measurable clinical effect. Several studies and meta-analyses with beta(2)-agonists and corticosteroids have failed to show any benefit of significant extent, however, physicians keep favouring their use. Presently, adrenaline has received rather consistent support from clinical trials but it is not yet widely prescribed. There are other therapeutic strategies, for instance, heliox, hypertonic saline, noninvasive ventilation, physical therapy techniques, thickened feeds or palivizumab that have shown promising potential benefits, but evidence supporting its use is still limited and further studies should be warranted. In the meantime, infants with acute viral bronchiolitis should be treated following evidence-based clinical practice guidelines, keeping the patient central in the process and being sensitive to social, cultural and familiar influences on their treatment strategy.

Helium-oxygen therapy for pediatric acute severe asthma requiring mechanical ventilation

OBJECTIVE

To illustrate the use of helium-oxygen gas mixtures as therapy for pediatric patients with acute severe asthma requiring conventional mechanical ventilation.

DESIGN

Retrospective review.

SETTING

Tertiary care children's teaching hospital.

PATIENTS

All mechanically ventilated patients with severe asthma admitted to the pediatric intensive care unit from August 1994 to October 2000.

INTERVENTIONS

Within 24 hrs of intubation or admission, patients were stabilized on volume ventilation, bronchodilator therapy, corticosteroids, and antibiotics when indicated. Hypercapnia was permitted while maintaining arterial blood gas pH > or =7.25. A helium-oxygen gas mixture then was begun with helium flow set at 5-7 L/min, and oxygen flow was titrated to maintain desired oxygen saturation. Only sedated, chemically paralyzed patients with adequate pre-helium-oxygen and post-helium-oxygen measurements were statistically analyzed.

MEASUREMENTS AND MAIN RESULTS

Twenty-eight mechanically ventilated patients with severe asthma placed on helium-oxygen gas mixtures were identified who met study entry criteria. Mean patient age was 8.8 yrs (range, 1.1-14.6). Before helium-oxygen therapy began, mean peak inspiratory pressure was 40.5 +/- 4.2 cm H(2)O, mean arterial blood gas pH was 7.26 +/- 0.05, and mean CO(2) partial pressure was 58.2 +/- 8.5 torr. After patients were placed on helium-oxygen therapy, there was a significant decrease in mean peak inspiratory pressure to 35.3 +/- 3.0 cm H(2)O. Mean pH increased significantly to 7.32 +/- 0.06, and mean partial pressure CO(2) decreased significantly to 50.5 +/- 7.4 torr. Initial mean inspired helium was 57 +/- 4% (range, 32-74). Mechanical ventilation days ranged from 1 to 23 days (mean, 5.0). Hospital stay ranged from 4 to 29 days (mean, 10.1), with an average pediatric intensive care unit stay of 6.9 days (range, 2-24). There were two incidences of pneumothorax.

CONCLUSIONS

In the pediatric patient with severe asthma requiring conventional mechanical ventilation, helium-oxygen administration appears to be a safe therapy and may assist in lowering peak inspiratory pressure and improving blood gas pH and partial pressure CO(2).

Successful management of severe respiratory failure combining heliox with noninvasive high-frequency percussive ventilation

Heliox has been shown to be beneficial in the management of different obstructive pulmonary disorders. High-frequency percussive ventilation has recently been advocated to treat lung injury in children with reduced lung compliance. We report our experience of combining heliox with noninvasive high-frequency percussive ventilation in a 5-yr-old boy with severe acute respiratory failure resulting from advanced cystic fibrosis lung disease. The dramatic improvement allowed stabilization and withholding of endotracheal intubation. We hypothesize that this approach improved gas exchange by enhancing molecular diffusion and by favoring laminar flow throughout the upper and lower airways. Further investigations should study the mechanisms of this noninvasive bimodal therapy.

New approaches to respiratory infections in children. Bronchiolitis and croup

Croup is a disease that is commonly seen in children younger than the age of 6 years. The cause is viral, with parainfluenza viruses and RSV being the two most common pathogens. Treatment consists primarily of supportive care, and parents usually have tried humidification and cool air exposure before the child presents to the ED. Children with moderate to severe croup are usually seen in the ED. The use of steroids in an oral preparation results in a clinical improvement of outpatients with mild to moderate croup and reduces the need for hospitalization. The dosage range for oral dexamethasone is 0.15 mg/kg to 0.6 mg/kg. Nebulized budesonide may also be used. Racemic or L-epinephrine, both of which are equally effective, can be used for symptomatic treatment in severe croup. After administration of racemic or L-epinephrine, hospitalization is not automatic and patients can be discharged safely from the ED after a 3-hour of observation period. There should be no respiratory distress, and the patient should have access to follow-up and emergency care if needed.

Heliox therapy in infants with acute bronchiolitis

OBJECTIVE

To assess the therapeutic effects of breathing a low-density gas mixture (heliox: 70% helium and 30% oxygen) in infants with bronchiolitis.

DESIGN

Prospective, interventional, comparative study.

SETTING

A pediatric intensive care unit (PICU) in a tertiary care, teaching hospital.

PATIENTS

Thirty-eight infants, 1 month to 2 years old, consecutively admitted to the PICU for treatment of moderate-to-severe acute respiratory syncytial virus bronchiolitis.

INTERVENTIONS

The first 19 patients were enrolled as the control group and received supportive care and nebulized epinephrine. In the next 19 patients, heliox therapy was added through a nonrebreather reservoir face mask. Measurements and Outcomes. Respiratory distress score, respiratory rate, heart rate, end-tidal CO(2) (etCO(2)), and pulse oximetry oxygen saturation (satO(2)) values were recorded at baseline and at regular intervals. Data obtained during the first 4 hours were analyzed for comparison purposes. Demographic data, age, time elapsed from the start of the symptoms to the admission to PICU, length of stay in PICU (PICU-LOS), and duration of heliox therapy were also collected for each patient. Reductions in clinical scores and PICU-LOS were considered primary outcomes. Main Results. At baseline, the heliox and control groups had similar age (5.5 +/- 3.1 vs 5.9 +/- 3 months), previous length of course (47.3 +/- 19.3 vs 45.4 +/- 18.6 hours), clinical score (6.7 +/- 1.1 vs 6.6 +/- 1), heart rate (160 +/- 24 vs 165 +/- 20 beats per minute), respiratory rate (64 +/- 7 vs 61 +/- 7 respirations per minute), satO(2) (91 +/- 2.3 vs 91 +/- 2.5%), and etCO(2) (34 +/- 7 vs 33 +/- 6 mm Hg). Clinical score, heart rate, respiratory rate, and satO(2) improved during the study in both groups. After 1 hour, the improvement in clinical score was significantly higher in the heliox group than in the control group (3.6 +/- 1.16 vs 5.5 +/- 0.89), and these differences continued to be significant at the end of the observation period (2.39 +/- 0.69 and 4.07 +/- 0.96, respectively), with a total average decrease in the score of 4.2 points in the heliox group versus 2.5 points in the control group. Heart and respiratory rates were also significantly lower in the heliox group compared with the control group after 1 hour and stayed lower throughout the rest of the study period. No changes were noted either in satO(2) between groups or in etCO(2) within or between groups throughout the study. Mean duration of heliox administration was 53 +/- 24 hours (range: 24-112 hours) and no adverse effects were detected. PICU-LOS was significantly shorter in the heliox group (3.5 +/- 1.1 days) than in the control group (5.4 +/- 1.6 days).

CONCLUSIONS

In infants with moderate-to-severe respiratory syncytial virus bronchiolitis, heliox therapy enhanced their clinical respiratory status, according to the marked improvement in their clinical scores and the reduction of the accompanying tachycardia and tachypnea. This beneficial response occurred within the first hour of its administration and was maintained as long as heliox therapy continued. In addition, PICU-LOS was reduced in heliox-treated patients. Long-term prospective studies are required to corroborate these findings and to establish the proper place of heliox in the therapeutic schedule of bronchiolitis.

Avoiding intubation in the injured subglottis: the role of heliox therapy

Intubation in the child presenting with severe viral tracheobronchitis or prior subglottic injury can be detrimental to the child and the subglottis. Intubation may lead to further mucosal ischemia, scar, subglottic stenosis, or failed extubation requiring a tracheotomy. Heliox is a combination of helium and oxygen that produces less-dense gas exchange. Its use leads to a decrease in turbulent airflow, which may obviate the need for intubation. Here we report our experience using heliox as initial therapy in 14 consecutive children presenting with severe airway distress and the need for intubation. (Five had viral tracheobronchitis, 5 had inflammatory exacerbation of subglottic stenosis, and 4 had acute iatrogenic subglottic injury.) In 10 of the 14 children, intubation, which can lead to mucosal injury and scarring, was avoided by the use of heliox therapy. Of the 4 children in whom heliox therapy failed, 3 had a prior history of subglottic stenosis. Heliox is a relatively safe and reliable alternative to intubation of children with severe subglottic edema or injury. Heliox should be considered before intubation for selected children with subglottic inflammation and severe airway distress.

Mechanical ventilatory support in infants with respiratory syncytial virus infection

OBJECTIVE: To present a review of current knowledge of the use of mechanical ventilatory support in the management of infants with respiratory failure secondary to infection with respiratory syncytial virus (RSV). DATA SOURCES: MEDLINE and manual search for case reports and clinical trials that address management strategies for respiratory support of infants with RSV infection. Data Extraction and Synthesis: Critical appraisal of reported epidemiologic and clinical data regarding risk factors, pathophysiology, and efficacy of respiratory therapy. There is an increasing number of hospital admissions for RSV infection with a variable proportion of infants who need mechanical ventilatory support. The mortality rate is estimated to be <1% in infants without preexisting respiratory or cardiac disorders vs. <5% in those with preexisting respiratory or cardiac disorders. Optimal ventilator settings need to be refined according to the dominant obstructive or restrictive pattern with the aim to avoid barovolutrauma. The role of noninvasive ventilation and additional therapies (heliox, beta(2) agonists, surfactant) is not conclusively established. The indications for high-frequency oscillatory ventilation with the possible adjunction of inhaled nitric oxide deserve further study. Extracorporeal membrane oxygenation plays a minor role in severe cases that are refractory to conventional treatment. CONCLUSIONS: Conventional ventilation strategies are usually adequate for treating infants with severe RSV infection. Particular attention must be paid to the dominant pathophysiologic mechanism in a given condition. Prospective trials are needed to validate alternative therapeutic options and to improve the outcome of the rare but most severe cases that are difficult to control.

Techniques to avoid intubation: noninvasive positive pressure ventilation and heliox therapy

NPPV is useful in decreasing the intubation rate in carefully selected patients with acute respiratory failure--particularly in patients with COPD. The results of some studies also suggest a survival benefit for use of NPPV with acute respiratory failure associated with COPD. Heliox therapy may be beneficial for selected patients with large airway obstruction or asthma. The use of heliox for other indications is unclear. Heliox may adversely affect the function of respiratory care equipment such as flow meters, ventilators, nebulizers, and pulmonary function monitors.

[Severe community-acquired pneumonia in immunocompetent children]

Severe community-acquired pneumonia (CAP) is still a serious disease with a high mortality rate, especially in developing countries. Children under 5 years are more prone to severe CAP. In this article, the authors review the definition and clinical criteria used in the initial evaluation and decision to hospitalize patients. The diagnosis approach requires only a limited number of laboratory tests before initiating the supportive measures and wide spectrum antimicrobial therapy. If the patient fails to respond favorably 48-72 hours after initiating therapy, more invasive investigations are indicated. After resolution, an immunological evaluation is warranted.