Helium-oxygen decreases inspiratory effort and work of breathing during pressure support in intubated 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.

A Multicenter Randomized Trial Assessing the Efficacy of Helium/Oxygen in Severe Exacerbations of Chronic Obstructive Pulmonary Disease

RATIONALE

During noninvasive ventilation (NIV) for chronic obstructive pulmonary disease (COPD) exacerbations, helium/oxygen (heliox) reduces the work of breathing and hypercapnia more than air/O₂, but its impact on clinical outcomes remains unknown.

OBJECTIVES

To determine whether continuous administration of heliox for 72 hours, during and in-between NIV sessions, was superior to air/O₂ in reducing NIV failure (25-15%) in severe hypercapnic COPD exacerbations.

METHODS

This was a prospective, randomized, open-label trial in 16 intensive care units (ICUs) and 6 countries. Inclusion criteria were COPD exacerbations with Pa_CO2 ≥ 45 mm Hg, pH ≤ 7.35, and at least one of the following: respiratory rate ≥ 25/min, Pa_O2 ≤ 50 mm Hg, and oxygen saturation (arterial [Sa_O2] or measured by pulse oximetry [Sp_O2]) ≤ 90%. A 6-month follow-up was performed.

MEASUREMENTS AND MAIN RESULTS

The primary endpoint was NIV failure (intubation or death without intubation in the ICU). The secondary endpoints were physiological parameters, duration of ventilation, duration of ICU and hospital stay, 6-month recurrence, and rehospitalization rates. The trial was stopped prematurely (445 randomized patients) because of a low global failure rate (NIV failure: air/O₂ 14.5% [n = 32]; heliox 14.7% [n = 33]; P = 0.97, and time to NIV failure: heliox group 93 hours [n = 33], air/O₂ group 52 hours [n = 32]; P = 0.12). Respiratory rate, pH, Pa_CO2, and encephalopathy score improved significantly faster with heliox. ICU stay was comparable between the groups. In patients intubated after NIV failed, patients on heliox had a shorter ventilation duration (7.4 ± 7.6 d vs. 13.6 ± 12.6 d; P = 0.02) and a shorter ICU stay (15.8 ± 10.9 d vs. 26.7 ± 21.0 d; P = 0.01). No difference was observed in ICU and 6-month mortality.

CONCLUSIONS

Heliox improves respiratory acidosis, encephalopathy, and the respiratory rate more quickly than air/O₂ but does not prevent NIV failure. Overall, the rate of NIV failure was low. Clinical trial registered with www.clinicaltrials.gov (NCT 01155310).

Noninvasive ventilation with helium-oxygen mixture in hypercapnic COPD exacerbation: aggregate meta-analysis of randomized controlled trials

When used as a driving gas during NIV in hypercapnic COPD exacerbation, a helium–oxygen (He/O₂) mixture reduces the work of breathing and gas trapping. The potential for He/O₂ to reduce the rate of NIV failure leading to intubation and invasive mechanical ventilation has been evaluated in several RCTs. The goal of this meta-analysis is to assess the effect of NIV driven by He/O₂ compared to air/O₂ on patient-centered outcomes in hypercapnic COPD exacerbation. Relevant RCTs were searched using standard procedures. The main endpoint was the rate of NIV failure. The effect size was computed by a fixed-effect model, and estimated as odds ratio (OR) with 95% confidence interval (CI). Additional endpoints were ICU mortality, NIV-related side effects, and the length and costs of ICU stay. Three RCTs fulfilled the selection criteria and enrolled a total of 772 patients (386 patients received He/O₂ and 386 received air/O₂). Pooled analysis showed no difference in the rate of NIV failure when using He/O₂ mixture compared to air/O₂: 17 vs 19.7%, respectively; OR 0.84, 95% CI 0.58–1.22; p = 0.36; I² for heterogeneity = 0%, and no publication bias. ICU mortality was also not different: OR 0.8, 95% CI 0.45–1.4; p = 0.43; I² = 5%. However, He/O₂ was associated with less NIV-related adverse events (OR 0.56, 95% CI 0.4–0.8, p = 0.001), and a shorter length of ICU stay (difference in means = −1.07 day, 95% CI −2.14 to −0.004, p = 0.049). Total hospital costs entailed by hospital stay and NIV gas were not different: difference in means = −279$, 95% CI −2052–1493, p = 0.76. Compared to air/O₂, He/O₂ does not reduce the rate of NIV failure in hypercapnic COPD exacerbation. It is, however, associated with a lower incidence of NIV-related adverse events and a shortening of ICU length of stay with no increase in hospital costs.

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.

The Effects of helium/oxygen mixture (heliox) before and after extubation in long-term mechanically ventilated very low birth weight infants

OBJECTIVES

Our goal was to evaluate the effects of a helium/oxygen mixture (heliox) on pulmonary mechanics and gas exchange in preterm infants during both conventional and noninvasive ventilation.

PATIENTS AND METHODS

Ten preterm infants, ventilated from birth, were enrolled. Resistive work of breathing, pulmonary compliance, static compliance, respiratory rate, minute ventilation, ventilatory support, and gas exchange were measured before and during treatment. One hour after heliox therapy, subjects who showed a decrease of peak inspiratory pressure of >20% of the initial value were extubated and shifted to nasal bilevel positive airway pressure with heliox for the following 3 hours. Pulmonary mechanics and ventilatory parameters were measured during air/oxygen ventilation and again 10 minutes and 1 hour after starting heliox. Transcutaneous pressure of O(2) and CO(2), oxygen saturation, and respiratory rate were recorded continuously. Arterial blood gases were measured immediately before and 1 hour after initiating bilevel positive airway pressure. To maintain oxygen saturation at >92% during the bilevel positive airway pressure phase, the mean fraction of inspired oxygen was increased from 0.34 to 0.36.

RESULTS

Mean peak inspiratory pressure decreased from 21.4 to 17.4 cmH(2)O, work of breathing decreased from 0.46 to 0.22 joule/L, and transcutaneous pressure of CO(2) decreased from 52.3 to 49.1 mmHg. Mean transcutaneous pressure of O(2) improved from 42.8 to 46.7 mmHg, and minute ventilation improved from 332 to 478 mL/kg per minute. No significant differences were observed in mean airway pressure, respiratory rate, oxygen saturation, pulmonary compliance, and static compliance. Eight infants were extubated. One of them needed to be reintubated after 5 hours.

CONCLUSIONS

Our data show that mechanical ventilation with heliox reduces resistive work of breathing and ventilatory support requirements and improves gas exchange in preterm infants.

Clinical review: liberation from mechanical ventilation

Mechanical ventilation is the defining event of intensive care unit (ICU) management. Although it is a life saving intervention in patients with acute respiratory failure and other disease entities, a major goal of critical care clinicians should be to liberate patients from mechanical ventilation as early as possible to avoid the multitude of complications and risks associated with prolonged unnecessary mechanical ventilation, including ventilator induced lung injury, ventilator associated pneumonia, increased length of ICU and hospital stay, and increased cost of care delivery. This review highlights the recent developments in assessing and testing for readiness of liberation from mechanical ventilation, the etiology of weaning failure, the value of weaning protocols, and a simple practical approach for liberation from mechanical ventilation.

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.