Heliox for asthma in the emergency department: a review of the literature

Therapeutic Gases and Inhaled Anesthetics as Adjunctive Therapies in Critically Ill Patients

The administration of exogenous oxygen to support adequate gas exchange is the cornerstone of respiratory care. In the past few years, other gaseous molecules have been introduced in clinical practice to treat the wide variety of physiological derangement seen in critical care patients.Inhaled nitric oxide (NO) is used for its unique selective pulmonary vasodilator effect. Recent studies showed that NO plays a pivotal role in regulating ischemia-reperfusion injury and it has antibacterial and antiviral activity.Helium, due to its low density, is used in patients with upper airway obstruction and lower airway obstruction to facilitate gas flow and to reduce work of breathing.Carbon monoxide (CO) is a poisonous gas that acts as a signaling molecule involved in many biologic pathways. CO's anti-inflammatory and antiproliferative effects are under investigation in the setting of acute respiratory distress and idiopathic pulmonary fibrosis.Inhaled anesthetics are widely used in the operative room setting and, with the development of anesthetic reflectors, are now a valid option for sedation management in the intensive care unit.Many other gases such as xenon, argon, and hydrogen sulfide are under investigation for their neuroprotective and cardioprotective effects in post-cardiac arrest syndrome.With all these therapeutic options available, the clinician must have a clear understanding of the physiologic basis, therapeutic potential, and possible adverse events of these therapeutic gases. In this review, we will present the therapeutic gases other than oxygen used in clinical practice and we will describe other promising therapeutic gases that are in the early phases of investigation.

Pulmonary surfactant and COVID-19: A new synthesis

Chapter 1

COVID-19 pathogenesis poses paradoxes difficult to explain with traditional physiology. For instance, since type II pneumocytes are considered the primary cellular target of SARS-CoV-2; as these produce pulmonary surfactant (PS), the possibility that insufficient PS plays a role in COVID-19 pathogenesis has been raised. However, the opposite of predicted high alveolar surface tension is found in many early COVID-19 patients: paradoxically normal lung volumes and high compliance occur, with profound hypoxemia. That 'COVID anomaly' was quickly rationalised by invoking traditional vascular mechanisms-mainly because of surprisingly preserved alveolar surface in early hypoxemic cases. However, that quick rejection of alveolar damage only occurred because the actual mechanism of gas exchange has long been presumed to be non-problematic, due to diffusion through the alveolar surface. On the contrary, we provide physical chemical evidence that gas exchange occurs by an process of expansion and contraction of the three-dimensional structures of PS and its associated proteins. This view explains anomalous observations from the level of cryo-TEM to whole individuals. It encompasses results from premature infants to the deepest diving seals. Once understood, the COVID anomaly dissolves and is straightforwardly explained as covert viral damage to the 3D structure of PS, with direct treatment implications. As a natural experiment, the SARS-CoV-2 virus itself has helped us to simplify and clarify not only the nature of dyspnea and its relationship to pulmonary compliance, but also the fine detail of the PS including such features as water channels which had heretofore been entirely unexpected.

Chapter 2

For a long time, physical, colloid and surface chemistry have not intersected with physiology and cell biology as much as we might have hoped. The reasons are starting to become clear. The discipline of physical chemistry suffered from serious unrecognised omissions that rendered it ineffective. These foundational defects included omission of specific ion molecular forces and hydration effects. The discipline lacked a predictive theory of self-assembly of lipids and proteins. Worse, theory omitted any role for dissolved gases, O2, N2, CO2, and their existence as stable nanobubbles above physiological salt concentration. Recent developments have gone some way to explaining the foam-like lung surfactant structures and function. It delivers O2/N2 as nanobubbles, and efflux of CO2, and H2O nanobubbles at the alveolar surface. Knowledge of pulmonary surfactant structure allows an explanation of the mechanism of corona virus entry, and differences in infectivity of different variants. CO2 nanobubbles, resulting from metabolism passing through the molecular frit provided by the glycocalyx of venous tissue, forms the previously unexplained foam which is the endothelial surface layer. CO2 nanobubbles turn out to be lethal to viruses, providing a plausible explanation for the origin of 'Long COVID'. Circulating nanobubbles, stable above physiological 0.17 M salt drive various enzyme-like activities and chemical reactions. Awareness of the microstructure of Pulmonary Surfactant and that nanobubbles of (O2/N2) and CO2 are integral to respiratory and circulatory physiology provides new insights to the COVID-19 and other pathogen activity.

[Chronic respiratory failure correction in cicatricial laryngeal and tracheal stenosis using helium-oxygen mixture]

The article provides a review of the literature on the development of chronic respiratory failure in patients with chronic cicatricial stenosis of the larynx and cervical trachea. The authors provide data on the etiology, pathogenetic features of the course of cicatricial stenosis of the larynx and trachea, the reasons for the development of chronic respiratory failure, the effect of hypoxemia on general metabolic processes in the body and on regeneration processes, as well as on methods of their correction and improvement of the postoperative period. The methods of respiratory impact on chronic respiratory failure in these patients are considered, based on the experience of a number of researchers and technical advances in recent years.

Heliox for inducible laryngeal obstruction (vocal cord dysfunction): A systematic literature review

OBJECTIVES

To perform a systematic literature review on the use of Heliox with patients with inducible laryngeal obstruction/vocal cord dysfunction to: i) identify current evidence base; and ii) establish the methodological quality of published research.

METHODS

Articles published up to March 2018 were searched for key words and terms using Cochrane Library, MEDLINE, PubMed, CINAHL, EMBASE and Dynamed. Studies were included if they presented original research into the use of Heliox for vocal cord dysfunction.

RESULTS

Only three studies met the inclusion criteria for review. All reported favorable results for the use of Heliox as an adjunctive therapy for vocal cord dysfunction but none had sufficient methodological quality to support their conclusions.

CONCLUSION

Despite review articles recommending the use of Heliox in vocal cord dysfunction, there is a lack of good quality research to support this conclusion. There is a need for further research to investigate the effectiveness of Heliox as an adjunctive therapy for vocal cord dysfunction.

LEVEL OF EVIDENCE

4.

Mechanically Ventilating the Severe Asthmatic

The management of the critically ill patients with asthma can be rather challenging. Potentially devastating complications relating to this presentation include hypoxemia, worsening bronchospasm, pulmonary aspiration, tension pneumothorax, dynamic hyperinflation, hypotension, dysrhythmias, and seizures. In contrast to various other pathologies requiring mechanical ventilation, acute asthma is generally associated with better outcomes. This review serves as a practical guide to the physician managing patients with severe acute asthma requiring mechanical ventilation. In addition to specifics relating to endotracheal intubation, we also discuss the interpretation of ventilator graphics, the recommended mode of ventilation, dynamic hyperinflation, permissive hypercapnia, as well as the role of extracorporeal membrane oxygenation and noninvasive mechanical ventilation.

Successful Extubation Using Heliox BiPAP in Two Patients with Postextubation Stridor

Postextubation stridor is associated with significant morbidity. It commonly results in extubation failure after established medical treatment fails, such as nebulized epinephrine and/or intravenous steroids. The role of heliox (i.e., combination of helium and oxygen) in managing patients with postextubation stridor has not been fully established. We report two cases of postextubation stridor successfully treated with heliox delivered with bilevel positive airway pressure (BiPAP) after failure of standard medical therapy.

Heliox in the treatment of status asthmaticus: case reports

Helium was discovered in 1868 by the French astronomer Pierre-Jules-César Janssen and was first used as a therapeutic treatment for airway obstruction by Barach almost 70 years later, in 1934. Heliox is characterized by its low density, which makes it more fluid under conditions of turbulence, thus minimizing airway pressure and facilitating the occurrence of laminar flow. The present article describes two clinical cases of patients with status asthmaticus subjected to mechanical ventilation and refractory to treatment in whom heliox was used, which allowed optimization of the efficacy of conventional pharmacological treatments. Although heliox is still used sporadically and its true efficacy has not been well demonstrated, the unique physical properties of helium and the theoretical improvement of the airflow in obstructed airways have produced scientific interest and stimulated research. Heliox can be used simultaneously with conventional therapies in cases of serious and refractory exacerbations of severe obstructive disease.

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.

Effects of Heliox in Stable COPD Patients at Rest and during Exercise

Heliox has been administered to stable chronic obstructive pulmonary disease (COPD) patients at rest and during exercise on the assumption that this low density mixture would have reduced work of breathing, dynamic hyperinflation, and, consequently, dyspnea sensation. Contrary to these expectations, beneficial effects of heliox in these patients at rest have been reported only sporadically, and the majority of the studies performed until now suggests that heliox is not a therapeutic option in spontaneously breathing resting COPD patients. On the other hand, when it is administered to COPD patients exercising at a constant work rate, heliox systematically decreases dyspnea sensation, and, often but not always, increases exercise tolerance. For these reasons, heliox has been evaluated as a non pharmacological tool to power rehabilitation programs. The conflicting results provided by the published trials probably point at a substantial heterogeneity of the COPD patients population in terms of respiratory mechanics and gas exchange. Therefore, further studies, aimed to the identification of mechanisms conditioning the response of exercising COPD patients to heliox, are warranted, before heliox administration, which is costly and cumbersome, can be routinely used in rehabilitation programs.

Airway management in post anaesthetic care

Some patients recovered in the post anaesthetic care unit (PACU) will require airway management and close monitoring to prevent any post operative complications. Ineffective airway management will lead rapidly to hypoxaemia, and will ultimately compromise patient care. This article discusses physiological principles and monitoring of airway management in the PACU, an understanding of which is essential when providing appropriate care for patients emerging from anaesthesia.

Update on management of bronchiolitis

PURPOSE OF REVIEW

Bronchiolitis impacts millions of infants worldwide. Although several therapeutic options stem from highly plausible theoretical rationales for success and some may even offer modest short-term symptom relief, none has been conclusively shown to alter the course of the disease or its major outcomes. However, several recent papers shed light on which treatments show promising preliminary evidence and offer insight into future research endeavors on this topic. This review will summarize bronchiolitis therapy in view of this recent evidence.

RECENT FINDINGS

The agents in which theory promises but treatment does not deliver include systemic corticosteroids alone, inhaled bronchodilators alone and antileukotrienes. The most promising combination to date appears to be that of oral dexamethasone and inhaled epinephrine but numerous related issues need to be clarified further. Caretakers need to be counselled about the usual protracted clinical course of bronchiolitis.

SUMMARY

Because bronchiolitis is a highly heterogeneous entity, future research challenges should include detailed characterization of infants most likely to benefit from given interventions. In the meantime, stick with the good old time-honored supportive route!

Current therapies in bronchiolitis

Viral bronchiolitis is the most common cause of hospitalization among infants. Despite its prevalence, no consistently effective therapy has been found to date, providing the driving force behind much of the ongoing research into this illness. In this review, we present a summary of the most recent published trials of interventions for bronchiolitis. Included are studies evaluating bronchodilators, corticosteroids, positive pressure ventilation, as well as 3 newer therapies for bronchiolitis: heliox, mucolytics, and leukotriene receptor antagonists.

Treatment strategies for reducing asthma-related emergency department visits

Acute asthma exacerbations reflect inadequate long-term disease control. Treatment to control acute asthma exacerbations includes: 1) rapid reversal of airflow obstruction with bronchodilators and systemic corticosteroids and reversing hypoxemia with oxygen in the emergency department (ED); 2) preventing early relapse by prescribing beta(2) agonists and oral corticosteroids at discharge and ensuring patients have an adequate supply of their other asthma medications; and 3) preventing future asthma exacerbations and ED visits through effective treatment in primary care. This article discusses each treatment and reviews the role of emergency physicians in treating patients to reverse airflow obstruction and prevent early relapse, future exacerbations, and ED visits by communicating the need for additional asthma control to patients' primary care physicians.