Helium-oxygen reduces work of breathing in mechanically ventilated patients with chronic obstructive pulmonary disease

The effect of helium-oxygen-assisted mechanical ventilation on chronic obstructive pulmonary disease exacerbation: A systemic review and meta-analysis

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is often accompanied by acute exacerbations. Patients of COPD exacerbation suffering from respiratory failure often need the support of mechanical ventilation. Helium-oxygen can be used to reduce airway resistance during mechanical ventilation. The aim of this study is to evaluate the effect of helium-oxygen-assisted mechanical ventilation on COPD exacerbation through a meta-analysis.

METHODS

A comprehensive literature search through databases of Pub Med (1966∼2016), Ovid MEDLINE (1965∼2016), Cochrane EBM (1991∼2016), EMBASE (1974∼2016) and Ovid MEDLINE was performed to identify associated studies. Randomized clinical trials met our inclusion criteria that focus on helium-oxygen-assisted mechanical ventilation on COPD exacerbation were included. The quality of the papers was evaluated after inclusion and information was extracted for meta-analysis.

RESULTS

Six articles and 392 patients were included in total. Meta-analysis revealed that helium-oxygen-assisted mechanical ventilation reduced Borg dyspnea scale and increased arterial PH compared with air-oxygen. No statistically significant difference was observed between helium-oxygen and air-oxygen as regards to WOB, PaCO2 , OI, tracheal intubation rates and mortality within hospital.

CONCLUSIONS

Our study suggests helium-oxygen-assisted mechanical ventilation can help to reduce Borg dyspnea scale. In terms of the tiny change of PH, its clinical benefit is negligible. There is no conclusive evidence indicating the beneficial effect of helium-oxygen-assisted mechanical ventilation on clinical outcomes or prognosis of COPD exacerbation.

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.

Spontaneous Breathing of Heliox Using a Semi-Closed Circuit: A Bench Study

Introduction:

The use of helium-oxygen mixture (heliox) for ventilation has an advantage in patients with obstruction of the airways. The physical properties of helium enable an easier gas flow through the airways; this enables easier breathing for the patient when compared to standard ventilation of air. A high cost of heliox falls within the factors that limit the use of heliox in clinical practice. At present, heliox is administered by use of an open circuit. The aim of this study is to propose a way of heliox administration that reduces heliox consumption but does not affect the positive heliox effects upon the airway resistance.

Methods:

To minimize consumption of heliox, a semi-closed circuit has been designed. The circuit is a modification of an anesthetic circuit composed of parts with the lowest possible resistances. As any circuit has its own resistance, the evaluation of its possible negative effect upon the work of breathing of patients with exacerbation of chronic obstructive pulmonary disease (COPD) has been conducted.

Results:

A semi-closed circuit for heliox administration has been constructed and evaluated. The intrinsic resistance of both the inspiratory and expiratory limbs of the circuit is less than 140 Pa·s/l. This resistance does not represent a significant workload for a patient with COPD exacerbation whose airway resistance is 10 to 20 fold higher.

Conclusions:

The designed semi-closed circuit offers a potential benefit of heliox in patients with COPD exacerbation.

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

OBJECTIVE

To assess the therapeutic effects of breathing a low-density helium and oxygen mixture (heliox, 80% helium and 20% oxygen) in premature infants with respiratory distress syndrome (RDS) treated with nasal continuous positive airway pressure (NCPAP).

METHODS

Infants born between 28 and 32 weeks of gestational age with radiologic findings and clinical symptoms of RDS and requiring respiratory support with NCPAP within the first hour of life were included. These infants were randomly assigned to receive either standard medical air (control group) or a 4:1 helium and oxygen mixture (heliox group) during the first 12 hours of enrollment, followed by medical air until NCPAP was no longer needed.

RESULTS

From February 2008 to September 2010, 51 newborn infants were randomly assigned to two groups, 24 in the control group and 27 in the heliox group. NCPAP with heliox significantly decreased the risk of mechanical ventilation in comparison with NCPAP with medical air (14.8% vs 45.8%).

CONCLUSIONS

Heliox increases the effectiveness of NCPAP in the treatment of RDS in premature infants.

Helium in the adult critical care setting

Helium is a low-density inert gas whose physical properties are very different from those of nitrogen and oxygen. Such properties could be clinically useful in the adult critical care setting, especially in patients with upper to more distal airway obstruction requiring moderate to intermediate levels of FiO₂. However, despite decades of utilization and reporting, it is still difficult to give any firm clinical recommendation in this setting. Numerous case reports are available in the context of upper airway obstruction of different origins, but there is a lack of controlled studies for this indication. One study reported a helium-induced beneficial effect on surrogates of work of breathing after extubation in non-COPD patients, possibly in relation to laryngeal consequences of tracheal intubation. Physiological benefits of helium-oxygen breathing have been demonstrated in the context of acute severe asthma, but there is a lack of large controlled studies demonstrating an effect on pertinent clinical endpoints, except for a study reported only as an abstract, which mentioned a reduction in the intubation rate in helium-treated patients. Finally, there are a number of physiological studies in the context of COLD-COPD patients demonstrating a beneficial effect, mainly by a reduction in the resistive inspiratory work of breathing but also by a reduction in hyperinflation. Reduction of hypercapnia was mainly observed in spontaneously breathing and noninvasively ventilated helium-treated patients but not in intubated patients during controlled ventilation, suggesting that the decrease in PaCO₂ was mainly in relation to a diminution in CO₂ production, related to the diminution in work of breathing and not an improved alveolar ventilation. Moreover, there is little evidence that helium-oxygen could improve parameters of heterogeneity in such patients. Two RCTs were unable to demonstrate a reduction in the intubation rate in such setting, but they were likely underpowered. An adequately powered international multicentric study is ongoing and will help to determinate the exact place of the helium-oxygen mixture in the future. The place of the mixture during the weaning period will deserve further evaluation.

A multicenter, randomized trial of noninvasive ventilation with helium-oxygen mixture in exacerbations of chronic obstructive lung disease

OBJECTIVE

To assess the effect of a helium-oxygen mixture on intubation rate and clinical outcomes during noninvasive ventilation in acute exacerbation of chronic obstructive pulmonary disease.

DESIGN

Multicenter, prospective, randomized, controlled trial.

SETTING

Seven intensive care units.

PATIENTS

A total of 204 patients with known or suspected chronic obstructive pulmonary disease and acute dyspnea, Paco2> 45 mm Hg and two among the following factors: pH <7.35, Paco2 <50 mm Hg, respiratory rate >25/min.

INTERVENTIONS

Noninvasive ventilation randomly applied with or without helium (inspired oxygen fraction 0.35) via a face mask.

MEASUREMENTS AND MAIN RESULTS

Duration and complications of NIV and mechanical ventilation, endotracheal intubation, discharge from intensive care unit and hospital, mortality at day 28, adverse and serious adverse events were recorded. Follow-up lasted until 28 days since enrollment. Intubation rate did not significantly differ between groups (24.5% vs. 30.4% with or without helium, p = .35). No difference was observed in terms of improvement of arterial blood gases, dyspnea, and respiratory rate between groups. Duration of noninvasive ventilation, length of stay, 28-day mortality, complications and adverse events were similar, although serious adverse events tended to be lower with helium (10.8% vs. 19.6%, p = .08).

CONCLUSIONS

Despite small trends favoring helium, this study did not show a statistical superiority of using helium during NIV to decrease the intubation rate in acute exacerbation of chronic obstructive pulmonary disease.

Helium–oxygen ventilation in the presence of expiratory flow-limitation: A model study

A comparison between air and heliox (80% helium-20% oxygen) ventilation was performed using a mathematical, non-linear dynamic, morphometric model of the respiratory system. Different obstructive conditions, all causing expiratory flow limitation (EFL), were simulated during mechanical ventilation to evaluate and interpret the effects of heliox on tidal EFL and dynamic hyperinflation. Relative to air ventilation, intrinsic positive end-expiratory pressure did not change with heliox if the obstruction was limited to the peripheral airways, i.e. beyond the seventh generation. When central airways were also involved, heliox reduced dynamic hyperinflation (DH) if the flow-limiting segment remained in the fourth to seventh airway generation during the whole expiration, but produced only minor effects if, depending on the contribution of peripheral to total apparent airway resistance, the flow-limiting segment moved eventually to the peripheral airways. In no case did heliox abolish EFL occurring with air ventilation, indicating that any increase in driving pressure would be without effect on DH. Hence, to the extent that chronic obstructive pulmonary disease (COPD) affects primarily the peripheral airways, and causes EFL through the same mechanisms operating in the model, heliox administration should not be expected to appreciably reduce DH in the majority of COPD patients who are flow-limited at rest.

Clinical review: use of helium-oxygen in critically ill patients

Use of helium-oxygen (He/O₂) mixtures in critically ill patients is supported by a reliable and well understood theoretical rationale and by numerous experimental observations. Breathing He/O₂ can benefit critically ill patients with severe respiratory compromise mainly by reducing airway resistance in obstructive syndromes such as acute asthma and decompensated chronic obstructive pulmonary disease. However, the benefit from He/O₂ in terms of respiratory mechanics diminishes rapidly with increasing oxygen concentration in the gaseous mixture. Safe use of He/O₂ in the intensive care unit requires specific equipment and supervision by adequately experienced personnel. The available clinical data on inhaled He/O₂ mixtures are insufficient to prove that this therapy has benefit with respect to outcome variables. For these reasons, He/O₂ is not currently a standard of care in critically ill patients with acute obstructive syndromes, apart from in some, well defined situations. Its role in critically ill patients must be more precisely defined if we are to identify those patients who could benefit from this therapeutic approach.

Use of helium-oxygen mixture in adult patients presenting with exacerbations of asthma and chronic obstructive pulmonary disease: a systematic review

We examined systematically all controlled and cross-over randomised trials in patients with acute exacerbations of asthma and chronic obstructive pulmonary disease comparing Heliox against air-oxygen mixtures. Fourteen studies were identified. In asthma studies, peak expiratory flow rate (PEFR) was increased by an average of 29.6% (95% CI 16.6-42.6) by Heliox-driven nebulisers, or by 13.3 l.min(-1) (95% CI 3.71-22.81) absolute. In studies of patients with chronic obstructive pulmonary disease receiving non-invasive ventilation the arterial carbon dioxide tension (P(a)co(2)) and respiratory rate were unchanged: weighted mean difference for P(a)co(2)-0.29kPa (95% CI - 0.64-0.07) favoured Heliox, and for respiratory rate 1.6 breaths.min(-1) (95% CI - 0.93, 4.14) favoured control. Heliox minimally reduced the work of breathing in intubated patients, and reduced intrinsic positive end expiratory pressure (iPEEP). The use of Heliox to drive nebulisers in patients with acute asthma slightly improves airflow measures. We were unable to determine whether this improved recovery.

Helium-oxygen decreases inspiratory effort and work of breathing during pressure support in intubated patients with chronic obstructive pulmonary disease

OBJECTIVE

To evaluate the impact of helium-oxygen (He/O2) on inspiratory effort and work of breathing (WOB) in intubated COPD patients ventilated with pressure support.

DESIGN AND SETTING

Prospective crossover interventional study in the medical ICU of a university hospital.

PATIENTS AND PARTICIPANTS

Ten patients.

INTERVENTIONS

Sequential inhalation (30 min each) of three gas mixtures: (a) air/O2, (b) He/O2 (c) air/O2, at constant FIO2 and level of pressure support.

MEASUREMENTS AND RESULTS

Inspiratory effort and WOB were determined by esophageal and gastric pressure. Throughout the study pressure support and FIO2 were 14+/-3 cmH2O and 0.33+/-0.07 respectively. Compared to Air/O2, He/O2 reduced the number of ineffective breaths (4+/-5 vs. 9+/-5 breaths/min), intrinsic PEEP (3.1+/-2 vs. 4.8+/-2 cmH2O), the magnitude of negative esophageal pressure swings (6.7+/-2 vs. 9.1+/-4.9 cmH2O), pressure-time product (42+/-37 vs. 67+/-65 cmH2O s(-1) min(-1)), and total WOB (11+/-3 vs. 18+/-10 J/min). Elastic (6+/-1 vs. 10+/-6 J/min) and resistive (5+/-1 vs. 9+/-4 J/min) components of the WOB were decreased by He/O2.

CONCLUSIONS

In intubated COPD patients ventilated with pressure support He/O2 reduces intrinsic PEEP, the number of ineffective breaths, and the magnitude of inspiratory effort and WOB. He/O2 could prove useful in patients with high levels of PEEPi and WOB ventilated in pressure support, for example, during weaning.

Development of Aerosol Drug Delivery with Helium Oxygen Gas Mixtures

Aerosol drug delivery using helium-oxygen gas mixtures (heliox) is considered in terms of flow physics, atomization, and aerosol mechanics. Theoretical considerations are then related to past studies of the physiological effects of the inhalation of heliox and its potential use as a drug delivery medium. Past clinical trials of heliox investigating this use are reviewed and technical recommendations made for its successful development. It is proposed that improved peripheral lung drug delivery with heliox is highly dependent on proper administration, especially the inclusion of proper reservoir system for the gas.