Nasal continuous positive airway pressure with heliox in preterm infants with respiratory distress syndrome

Neonatal Applications of Heliox: A Practical Review

Heliox is a mixture of helium and oxygen that may be utilized as an alternative to air-oxygen during the ventilatory support in the neonate. Special physical properties of Heliox, particularly low density, allow for improved gas flow and diffusion. First reports of Heliox use in the pediatric population were published in 1930s; however, this therapy has never gained widespread popularity despite its described beneficial effects. Historically, this was largely due to technical challenges associated with Heliox ventilation that significantly limited its use and realization of large-scale clinical trials. However, nowadays several commercially available ventilators allow easy and safe ventilation with both conventional and non-invasive modes. In the era of minimally invasive respiratory interventions in the newborn Heliox could be seen as a therapy that may potentially decrease the risk of non-invasive ventilation failure. This review presents pathophysiologic rationale for the use of Heliox in the newborn, and summarizes available data regarding applications of Heliox in the setting of neonatal intensive care unit based on clinical studies and findings from animal models. Mechanisms of action and practical aspects of Heliox delivery are thoroughly discussed. Finally, future research directions for neonatal use of Heliox are proposed.

Effects of heliox and non-invasive neurally adjusted ventilatory assist (NIV-NAVA) in preterm infants

Due to its unique properties, helium–oxygen (heliox) mixtures may provide benefits during non-invasive ventilation, however, knowledge regarding the effects of such therapy in premature infants is limited. This is the first report of heliox non-invasive neurally adjusted ventilatory assist (NIV-NAVA) ventilation applied in neonates born ≤ 32 weeks gestational age. After baseline NIV-NAVA ventilation with a standard mixture of air and oxygen, heliox was introduced for 3 h, followed by 3 h of air-oxygen. Heart rate, peripheral capillary oxygen saturation, cerebral oxygenation, electrical activity of the diaphragm (Edi) and selected ventilatory parameters (e.g., respiratory rate, peak inspiratory pressure) were continuously monitored. We found that application of heliox NIV-NAVA in preterm infants was feasible and associated with a prompt and significant decrease of Edi suggesting reduced respiratory effort, while all other parameters were stable throughout the study, and had similar values during heliox and air-oxygen ventilation. This therapy may potentially enhance the efficacy of non-invasive respiratory support in preterm neonates and reduce the number of infants progressing to ventilatory failure.

Aerosol drug delivery to spontaneously-breathing preterm neonates: lessons learned

Delivery of medications to preterm neonates receiving non-invasive ventilation (NIV) represents one of the most challenging scenarios for aerosol medicine. This challenge is highlighted by the undersized anatomy and the complex (patho)physiological characteristics of the lungs in such infants. Key physiological restraints include low lung volumes, low compliance, and irregular respiratory rates, which significantly reduce lung deposition. Such factors are inherent to premature birth and thus can be regarded to as the intrinsic factors that affect lung deposition. However, there are a number of extrinsic factors that also impact lung deposition: such factors include the choice of aerosol generator and its configuration within the ventilation circuit, the drug formulation, the aerosol particle size distribution, the choice of NIV type, and the patient interface between the delivery system and the patient. Together, these extrinsic factors provide an opportunity to optimize the lung deposition of therapeutic aerosols and, ultimately, the efficacy of the therapy.

In this review, we first provide a comprehensive characterization of both the intrinsic and extrinsic factors affecting lung deposition in premature infants, followed by a revision of the clinical attempts to deliver therapeutic aerosols to premature neonates during NIV, which are almost exclusively related to the non-invasive delivery of surfactant aerosols. In this review, we provide clues to the interpretation of existing experimental and clinical data on neonatal aerosol delivery and we also describe a frame of measurable variables and available tools, including in vitro and in vivo models, that should be considered when developing a drug for inhalation in this important but under-served patient population.

FiO2 Before Surfactant, but Not Time to Surfactant, Affects Outcomes in Infants With Respiratory Distress Syndrome

Aim: To establish the impact of oxygen requirement before surfactant (SF) and time from birth to SF administration on treatment outcomes in neonatal respiratory distress syndrome (RDS). Methods: We conducted a post-hoc analysis of data from a prospective cohort study of 500 premature infants treated with less invasive surfactant administration (LISA). LISA failure was defined as the need for early (<72 h of life) mechanical ventilation (MV). Baseline clinical characteristic parameters, time to SF, and fraction of inspired oxygen (FiO₂) prior to SF were all included in the multifactorial logistic regression model that explained LISA failure. Results: LISA failed in 114 of 500 infants (22.8%). The median time to SF was 2.1 h (IQR: 0.8-6.7), and the median FiO₂ prior to SF was 0.40 (IQR: 0.35-0.50). Factors significantly associated with LISA failure were FiO₂ prior to SF (OR 1.03, 95% CI 1.01-1.04) and gestational age (OR 0.82, 95 CI 0.75-0.89); both p <0.001. Time to SF was not an independent risk factor for therapy failure (p = 0.528) or the need for MV at any time during hospitalization (p = 0.933). Conclusions: The FiO₂ before SF, but not time to SF, influences the need for MV in infants with RDS. While our findings support the relevance of FiO₂ in SF prescription, better adherence to the recommended FiO₂ threshold for SF (0.30) is required in daily practice.

Respiratory Support of Neonate Affected by Bronchiolitis in Neonatal Intensive Care Unit

Acute respiratory infections are very common medical emergency in early infancy, often requiring hospitalization. The most frequent respiratory infection at this stage of life is bronchiolitis, with a benign course in the majority of cases. However, especially during neonatal period, infants are at higher risk for developing complications, and ventilatory support of various degrees is needed. The two most widespread methods to provide noninvasive respiratory support are heated humidified high-flow nasal cannula and nasal continuous positive airway pressure. They are both used in neonatal intensive care unit to treat respiratory distress syndrome of the premature infants, and the main concept of recruiting and distending alveoli is valid also for respiratory failure occurring during bronchiolitis. However, there is still ongoing debate about the superiority of one method, and their real efficacy still need to be confirmed. Once respiratory failure does not respond to noninvasive ventilation, more intensive care must be provided in the form of conventional mechanical ventilation or high-frequency ventilation. There is currently no evidence of the optimal ventilation strategy to use, and a deeper comprehension of the pulmonary mechanics during bronchiolitis would be desirable to tailor ventilation according to the degree of severity. Further research is then urgently needed to better clarify these aspects. KEY POINTS: · Guidelines on the management of bronchiolitis in neonatal population are lacking.. · Noninvasive respiratory support is mostly delivered with HHHFNC and nCPAP.. · A deeper comprehension of the pulmonary mechanics during bronchiolitis is crucial to tailor invasive ventilation..

Noninvasive Ventilation with Heliox for Respiratory Distress Syndrome in Preterm Infant: A Systematic Review and Meta-Analysis

Objectives. To assess whether noninvasive ventilation with Heliox reduces the need for endotracheal ventilation and subsequent complications in preterm infants with respiratory distress syndrome (RDS). Methods. A search of major electronic databases, including MEDLINE and the Cochrane Central Register of Controlled Trials, for randomized or quasi-randomized controlled trials that compared noninvasive ventilation with Heliox versus noninvasive ventilation with standard gas for preterm infants with RDS was performed. The primary outcome was the incidence of intubation. The secondary outcomes were the level of PaCO₂, the use of surfactant, and other complications. Results. Two randomized and one quasi-randomized controlled trials including 123 preterm infants were assessed. Heliox was found to significantly decrease the incidence of intubation (RR: 0.42; 95% CI: 0.23 to 0.78), the level of PaCO₂ (MD: −9.61; 95% CI: −15.76 to −03.45), and the use of surfactant (RR: 0.25; 95% CI: 0.10 to 0.61) as compared with standard gas. No significant differences were found in other secondary outcomes. Conclusions. Noninvasive ventilation with Heliox decreases the incidence of intubation in preterm infants suffering from RDS. However, data on clinical outcomes are limited. Larger trials are needed to verify the beneficial effects.

Nasal intermittent positive pressure ventilation with heliox in premature infants with respiratory distress syndrome: a randomized controlled trial

OBJECTIVE

To assess the efficacy of nasal intermittent positive pressure ventilation with heliox in preterm infants with respiratory distress syndrome.

METHODS

Premature infants with mild respiratory distress syndrome requiring non-invasive respiratory support were eligible. Infants were randomly assigned to heliox or air-oxygen group. The main outcome was the length of ventilation.

RESULTS

Heliox significantly decreased the length of ventilation. The length of ventilation was positively correlated with interleukin-6 at baseline. Carbon dioxide elimination was better in the heliox group.

CONCLUSION

Heliox delivered with nasal intermittent positive pressure ventilation may be effective in reducing length of ventilation and increasing carbon dioxide elimination.

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.

High flow nasal heliox improves work of breathing and attenuates lung injury in a newborn porcine lung injury model

BACKGROUND

High flow nasal cannula (HFNC) has been shown to improve ventilation and oxygenation and reduce work of breathing in newborns with respiratory distress. Heliox, decreases resistance to airflow, reduces the work of breathing, facilitates the distribution of inspired gas, and has been shown to attenuate lung inflammation during the treatment of acute lung injury.

HYPOTHESIS

Heliox delivered by HFNC will decrease resistive load, decrease work of breathing, improve ventilation and attenuate lung inflammation during spontaneous breathing following acute lung injury in the newborn pig.

METHODS

Spontaneously breathing neonatal pigs received Nitrox or Heliox by HFNC and studied over 4 hrs following oleic acid injury. Gas exchange, pulmonary mechanics and systemic inflammation were measured serially. Lung inflammation biomarkers were assessed at termination.

RESULTS

Heliox breathing animals demonstrated lower work of breathing reflected by lower tracheal pressure, phase angle and phase relationship. Ventilation efficiency index was greater compared to Nitrox. Heliox group showed less lung inflammation reflected by lower tissue interleukin-6 and 8.

CONCLUSION

High flow nasal Heliox decreased respiratory load, reduced resistive work of breathing indices and attenuated lung inflammatory profile while ventilation was supported at less pressure effort in the presence of acute lung injury.

High flow nasal cannula (HFNC) with Heliox decreases diaphragmatic injury in a newborn porcine lung injury model

BACKGROUND

High flow nasal cannula (HFNC) improves ventilation by washing out nasopharyngeal dead space while delivering oxygen. Heliox (helium-oxygen gas mixture), a low-density gas mixture, decreases resistance to airflow, reduces the work of breathing, and facilitates distribution of inspired gas. Excessive lung work and potential injury increases the workload on the immature diaphragm predisposing the muscle to fatigue, and can lead to inflammatory and oxidative stress, thereby contributing to impaired diaphragmatic function. We tested the hypothesis that HFNC with Heliox will decrease the work of breathing thereby unloading the neonatal diaphragm, and potentially reducing diaphragmatic injury.

METHODS

Spontaneously breathing neonatal pigs were randomized to Nitrox (nitrogen-oxygen gas mixture) or Heliox, and studied over 4 hr following oleic acid injury. Gas exchange, pulmonary mechanics indices, and systemic markers of inflammation were measured serially. Diaphragm inflammation biomarkers and histology for muscle injury were assessed at termination.

RESULTS

Heliox breathing animals demonstrated decreased respiratory load and work of breathing with lower pressure-rate product, lower labored breathing index, and lower levels of diaphragmatic inflammatory markers, and muscle injury score as compared to Nitrox.

CONCLUSION

These results suggest that HFNC with Heliox is a useful adjunct to attenuate diaphragmatic fatigue in the presence of lung injury by unloading the diaphragm, resulting in a more efficient breathing pattern, and decreased diaphragm injury.

Heliox for mechanically ventilated newborns with bronchopulmonary dysplasia

OBJECTIVE

We assessed the safety and studied the influence of short-term helium-oxygen (heliox) mechanical ventilation (MV) on respiratory function, gas exchange and oxygenation in infants with bronchopulmonary dysplasia (BPD) or at high risk for BPD.

DESIGN

A pilot, time-series study.

SETTING

Neonatal intensive care unit.

PATIENTS

Infants with severe BPD who required MV.

INTERVENTIONS

MV with helium-oxygen and air-oxygen mixtures.

MAIN OUTCOME MEASURES

Respiratory parameters, acid-base balance, oxygenation and vital signs were recorded at five time points: initially during MV with air-oxygen, after 15 and 60 min of helium-oxygen MV, and 15 and 60 min after return to air-oxygen MV.

RESULTS

15 infants with BPD were enrolled. Helium-oxygen MV was well tolerated and was associated with a statistically significant increase in tidal volume, dynamic compliance and peak expiratory flow rate. An improvement in oxygenation and a decrease in fraction of inspired oxygen was also observed. During helium-oxygen MV there was a significant decrease in the oxygenation index and alveolar-arterial oxygen tension difference. The PaO2/fraction of inspired oxygen (FiO2) ratio increased significantly during helium-oxygen ventilation. A decrease in PaCO2 and an increase in pH were also observed during helium-oxygen administration, however this was not statistically significant. After ventilation with helium-oxygen was discontinued, the infants' respiratory function and oxygenation deteriorated and supplemental oxygen requirements increased accordingly.

CONCLUSIONS

Helium-oxygen MV is safe and resulted in improvement of respiratory function and oxygenation in infants with severe BPD requiring MV.

Avoiding endotracheal ventilation to prevent bronchopulmonary dysplasia: a meta-analysis

BACKGROUND AND OBJECTIVE

Mechanical ventilation via an endotracheal tube is a risk factor for bronchopulmonary dysplasia (BPD), one of the most common morbidities of very preterm infants. Our objective was to investigate the effect that strategies to avoid endotracheal mechanical ventilation (eMV) have on the incidence of BPD in preterm infants <30 weeks' gestational age (GA).

METHODS

In February 2013, we searched the databases Medline, Embase, and the Cochrane Central Register of Controlled Trials. Study selection criteria included randomized controlled trials published in peer-reviewed journals since the year 2000 that compared preterm infants <30 weeks' GA treated by using a strategy aimed at avoiding eMV with a control group in which mechanical ventilation via an endotracheal tube was performed at an earlier stage. Data were extracted and analyzed by using the standard methods of the Cochrane Neonatal Review Group. The authors independently assessed study eligibility and risk of bias, extracted data and calculated odds ratios and 95% confidence intervals, employing RevMan version 5.1.6.

RESULTS

We identified 7 trials that included a total of 3289 infants. The combined odds ratio (95% confidence interval) of death or BPD was 0.83 (0.71-0.96). The number needed to treat was 35. The study results were remarkably homogeneous. Avoiding eMV had no influence on the incidence of severe intraventricular hemorrhage.

CONCLUSIONS

Strategies aimed at avoiding eMV in infants <30 weeks' GA have a small but significant beneficial impact on preventing BPD.

Heliox non-invasive ventilation for preventing extubation failure in preterm infants

OBJECTIVES

Our aim was to assess whether non-invasive ventilation with heliox may decrease the incidence of extubation failure in preterm infants with RDS.

METHODS

Infants <29 weeks of gestation were treated immediately after extubation with heliox combined with nasal continuous airway pressure (Hx-NCPAP) or bilevel NCPAP (Hx-BiPAP) for 24 h, while infants in the control groups were treated with conventional NCPAP or BiPAP. The primary endpoint was the comparison of the extubation failure rate in the two groups, where failure was defined as the need for MV during the 24 h following extubation.

RESULTS

Eighteen infants were assigned to the heliox group and 18 to the control group. The extubation failure rate was similar (p = 0.249) in the heliox (n = 6; 33%) and in the control group (n = 9; 50%), but required mean airway pressure (MAP: 4.0+1.0 vs. 4.8+1.2 cm H2O; p = 0.037) and PaCO2 (39+8 mmHg vs. 52+7 mmHg; p < 0.001) at 24 h of treatment were lower in the heliox group.

CONCLUSIONS

Non-invasive ventilation with heliox was not effective in decreasing extubation failure in preterm infants with RDS, but did improve their respiratory function. Our findings might support the planning of large randomized controlled studies to evaluate the effectiveness of heliox non-invasive ventilation for decreasing extubation failure in premature infants.