Heliox Redux
2003; Elsevier BV; Volume: 123; Issue: 3 Linguagem: Inglês
10.1378/chest.123.3.673
ISSN1931-3543
Autores Tópico(s)High Altitude and Hypoxia
ResumoHelium is an inert, colorless gas. It was discovered by spectroscopic methods during an eclipse of the sun in India in 1868 and, thus, was named from the Greek word helios, which means sun. It was not isolated until 1895 by Sir William Ramsey, and by Nils Langlet and P.T. Cleve. Its first major uses in the first third of the 20th century were for filling airships and balloons during World War I and for divers in a mixture with oxygen. Alvan Barach1Barach AL Use of helium as a new therapeutic gas.Proc Soc Exp Biol Med. 1934; 32: 462-464Crossref Scopus (74) Google Scholar first used it for medical purposes in 1934 and confirmed the biological inertness of helium by exposing mice to 79% helium and 21% oxygen for 2 months without deleterious effects.2Barach AL Rare gases not essential to life.Science. 1934; 80: 593Crossref PubMed Scopus (5) Google Scholar He reported the successful usage of helium-oxygen mixtures in four cases of asthma in adults and two cases of upper airway obstruction in infants.3Barach AL The use of helium in the treatment of asthma and obstructive lesions of the larynx and trachea.Ann Intern Med. 1935; 9: 739-765Crossref Google Scholar Of interest, the patients were relieved of their dyspnea in 6 to 10 breaths, and when the helium was removed the dyspnea came back in 3 or 4 breaths. After the explosion of the dirigible Hindenburg in 1937, Congress regulated the sale of helium, and its availability was further reduced during World War II. After the war, with the advent of pharmacologic bronchodilators with improving side-effect profiles, helium was cast aside as a treatment for asthma. It was relegated back to filling balloons at parties, where its effect on the voice, making one sound like “Donald Duck,” was its main notoriety. There were a few reports of its respiratory usage showing the lack of significant improvement in asthmatic patients4Schiller IW Lowell FC Lynch MY et al.The effect of helium oxygen mixtures on pulmonary function in asthmatic patients.J Allergy. 1955; : 11-14Abstract Full Text PDF Scopus (6) Google Scholar and in patients with emphysema.5Grape B Channin E Tyler JM The effect of helium and oxygen mixtures on pulmonary resistance in emphysema.Am Rev Respir Dis. 1960; 81: 823-829PubMed Google Scholar Helium-oxygen was shown to be an effective treatment of upper airway obstruction in 1976,6Lu TS Ohmura A Wong KC et al.Helium-oxygen in the treatment of upper airway obstruction.Anesthesiology. 1976; 45: 678-680Crossref PubMed Scopus (49) Google Scholar and there were scattered reports for this usage until 1986.7Skrinskas GJ Hyland RH Hutcheon MA Using helium-oxygen mixtures in the management of acute upper airway obstruction.Can Med Assoc J. 1983; 128: 555-558PubMed Google Scholar8TenEyck LG Colgan FJ Methods and guidelines for mechanical ventilation with helium-oxygen for severe upper-airway obstruction.Respir Care. 1984; 29: 155-159Google Scholar9Curtis JL Mahlmeister M Stulberg MS et al.Helium-oxygen gas therapy: use and availability for the emergency treatment of the inoperable airway obstruction.Chest. 1986; 90: 455-457Crossref PubMed Scopus (48) Google Scholar In 1987, the use of helium-oxygen in the treatment of patients with asthma resurfaced in Hartford, CT, and in France, and it became known as heliox. Within a few years, its use spread to Camden, NJ, Chicago, IL, Houston, TX and then to many other sites. Despite anecdotal reports of its efficacy,10Martin-Barbaz F Barnoud D Carpenter F et al.The use of helium and oxygen mixtures in status asthmaticus.Rev Pneumol Clin. 1987; 43: 186-189PubMed Google Scholar11Shiue S-T Gluck EH The use of helium-oxygen mixtures in the support of patients with status asthmaticus and respiratory acidosis.J Asthma. 1989; 26: 177-180Crossref PubMed Scopus (92) Google Scholar12Gluck EH Onorato DJ Castriotta R Helium-oxygen mixtures in intubated patients with status asthmaticus and respiratory acidosis.Chest. 1990; 98: 693-698Abstract Full Text Full Text PDF PubMed Scopus (201) Google Scholar13Kass JE Castriotta RJ Heliox therapy in acute severe asthma.Chest. 1995; 107: 757-760Abstract Full Text Full Text PDF PubMed Scopus (136) Google Scholar14Manthous CA Hall JB Melmed A et al.Heliox improves pulsus paradoxus and peak expiratory flow in nonintubated patients with severe asthma.Am J Respir Crit Care Med. 1995; 151: 310-314Crossref PubMed Scopus (166) Google Scholar heliox therapy for asthma patients continued to be viewed as experimental because of the lack of randomized controlled trials.15Madison JM Irwin RS Heliox for asthma: a trial balloon.Chest. 1995; 107: 597-598Abstract Full Text Full Text PDF PubMed Scopus (18) Google Scholar16Corbridge TC Hall JB The assessment and management of adults with status asthmaticus.Am J Respir Crit Care Med. 1995; 151: 1296-1316Crossref PubMed Scopus (189) Google Scholar The theoretical basis behind the use of helium in asthma patients mainly relates to its low density. It has the lowest density of any gas except hydrogen. Asthma is a disorder of airways obstruction, and the pathophysiology includes an increased turbulent flow in the airways. Since airway resistance in turbulent flow is directly related to the density of a gas, helium with its lower density results in a lower airway resistance. It also reduces the Reynolds number, converting turbulent flow to laminar flow and further decreasing airway resistance. These effects result in a decreased work of breathing. Helium also increases the diffusion of carbon dioxide and may improve alveolar ventilation, resulting in improved gas exchange. Helium is an inert element and does not interact with any biochemical process. It is noncombustible, nonexplosive, and nondetectable by taste and smell. Its effect on the airways occurs and goes away within a few breaths. In summary, it is an extremely safe and rapid-acting therapeutic agent that reduces airway resistance, decreases the work of breathing, and may improve gas exchange. So what is its downside? The cost for heliox is in the range of $30 to $70 for 8 h of usage, making it a rather low-cost medical modality.17Manthous CA Morgan SM Hall JB et al.Heliox in the treatment of airflow obstruction: a critical review of the literature.Respir Care. 1997; 42: 1034-1042Google Scholar However, its usage takes a little knowledge and work. Heliox needs to be dispensed via a nonrebreathing mask, so it is not diluted with room air. The heliox tanks have to be obtained and, despite their large size, have to be easily accessible to the emergency department and/or ICU. Educational sessions have to be set up with respiratory therapists and with the staffs of the emergency department and ICU. There are few guidelines in the medical literature on optimal patient selection and usage. In cases in which it has been beneficial, the rapidity and power of the therapeutic effect can be truly amazing. Two cases that I was involved with come to mind. In 1987, a young asthmatic patient went into respiratory failure and, despite all known treatments including halothane general anesthesia, was unable to be adequately ventilated. With heliox, the peak airway pressure and the Paco2 markedly dropped in only a few minutes. Another young asthmatic patient, who had a pH of 6.95, refused endotracheal intubation. As with the prior patient, only a few minutes after initiating heliox, the patient had dramatic relief of dyspnea and the Paco2 markedly diminished toward the normal range. However, not all asthmatic patients have such profound response to heliox. This anecdotal use of heliox in asthma patients led to three clinical studies11Shiue S-T Gluck EH The use of helium-oxygen mixtures in the support of patients with status asthmaticus and respiratory acidosis.J Asthma. 1989; 26: 177-180Crossref PubMed Scopus (92) Google Scholar12Gluck EH Onorato DJ Castriotta R Helium-oxygen mixtures in intubated patients with status asthmaticus and respiratory acidosis.Chest. 1990; 98: 693-698Abstract Full Text Full Text PDF PubMed Scopus (201) Google Scholar13Kass JE Castriotta RJ Heliox therapy in acute severe asthma.Chest. 1995; 107: 757-760Abstract Full Text Full Text PDF PubMed Scopus (136) Google Scholar at Hartford and Mount Sinai hospitals (Hartford, CT), which were published between 1989 and 1995. These studies, in patients with acute ventilatory failure who were and were not receiving mechanical ventilation, demonstrated a dramatic decrease in Paco2 in a great majority of patients, but not all. Heliox was still not accepted as a therapeutic choice for the treatment of acute severe asthma and was relegated to a grab bag of unconventional treatments due to the lack of a randomized controlled study demonstrating its efficacy.15Madison JM Irwin RS Heliox for asthma: a trial balloon.Chest. 1995; 107: 597-598Abstract Full Text Full Text PDF PubMed Scopus (18) Google Scholar16Corbridge TC Hall JB The assessment and management of adults with status asthmaticus.Am J Respir Crit Care Med. 1995; 151: 1296-1316Crossref PubMed Scopus (189) Google Scholar However, this interest in heliox spawned other clinical trials across the country in patients with stridor,18Kemper KJ Ritz RH Benson MS et al.Helium-oxygen mixture in the treatment of postextubation stridor in pediatric trauma patients.Crit Care Med. 1991; 19: 356-359Crossref PubMed Scopus (90) Google Scholar19Rodelberg DA Easter AJ Washam MA et al.Use of a helium-oxygen mixture in the treatment of postextubation stridor in pediatric patients with burns.J Burn Care Rehabil. 1995; 16: 476-480Crossref Scopus (65) Google Scholar bronchiolitis,20Hollman G Shen G Strauss R et al.Helium-oxygen improves clinical asthma scores in children with acute bronchiolitis.Crit Care Med. 1998; 26: 1731-1736Crossref PubMed Scopus (98) Google Scholar croup,21Terregino CA Nairn SA Kass JE et al.The effect of heliox on croup: a pilot study.Acad Emerg Med. 1998; 5: 1130-1133Crossref PubMed Scopus (40) Google Scholar and COPD,22Jolliet P Tassaux D Chevrolet J-C et al.Beneficial effects of helium:oxygen versus air:oxygen noninvasive pressure support in patients with decompensated chronic obstructive pulmonary disease.Crit Care Med. 1999; 27: 2422-2429Crossref PubMed Scopus (100) Google Scholar23Jaber S Fodiol R Brochard L et al.Noninvasive ventilation with helium-oxygen in acute exacerbation of chronic obstructive pulmonary disease.Am J Respir Crit Care Med. 2000; 161: 1191-1200Crossref PubMed Scopus (139) Google Scholar as well as investigations of its effect on nebulizer and ventilator function.24Anderson M Svartengren M Bylin G et al.Deposition in asthmatics of particles inhaled in air or in helium-oxygen.Am Rev Respir Dis. 1993; 147: 524-528Crossref PubMed Scopus (125) Google Scholar25Hess DR Acosta FL Camargo CA et al.The effect of heliox on nebulizer function using a β-agonist bronchodilator.Chest. 1999; 115: 184-189Abstract Full Text Full Text PDF PubMed Scopus (114) Google Scholar26Goode ML Fink JB Tobin MJ et al.Improvement in aerosol delivery with helium-oxygen mixtures during mechanical ventilation.Am J Respir Crit Care Med. 2001; 163: 109-114Crossref PubMed Scopus (99) Google Scholar27Tassaux D Jolliet P Chevrolet J-C et al.Calibration of seven ICU ventilators for mechanical ventilation with helium-oxygen mixtures.Am J Respir Crit Care Med. 1999; 160: 22-32Crossref PubMed Scopus (86) Google Scholar28Oppenheim-Eden A Cohen Y Weissman C et al.The effect of helium on ventilator performance.Chest. 2001; 120: 528-588Abstract Full Text Full Text PDF Scopus (25) Google Scholar In the article in this issue of CHEST (see page 882), Ho et al reviewed eight randomized controlled trials29Carter ER Webb CRT Moffit DR Evaluation of heliox in children hospitalized with acute severe asthma.Chest. 1996; 109: 1256-1261Abstract Full Text Full Text PDF PubMed Scopus (115) Google Scholar30Kudukis TM Manthous CA Schmidt GA et al.Inhaled helium–oxygen revisited: effect of inhaled helium-oxygen during the treatment of status asthmaticus in children.J Pediatr. 1997; 130: 217-224Abstract Full Text Full Text PDF PubMed Scopus (143) Google Scholar31Kass JE Terregino CA The effect of heliox in acute severe asthma: a randomized controlled trial.Chest. 1999; 116: 296-300Abstract Full Text Full Text PDF PubMed Scopus (111) Google Scholar32Henderson SO Acharya P Kilaghbian T et al.Use of heliox-driven nebulizer therapy in the treatment of acute asthma.Ann Emerg Med. 1999; 33: 141-146Abstract Full Text Full Text PDF PubMed Scopus (73) Google Scholar33Dorfman TA Shipley ER Burton JH et al.Inhaled heliox does not benefit ED patients with moderate to severe asthma [letter].Am J Emerg Med. 2000; 18: 495-497Abstract Full Text Full Text PDF PubMed Scopus (33) Google Scholar34L’Her E Monchi M Joly B et al.Helium-oxygen breathing in the early emergency care of acute severe asthma: a randomized pilot study.Eur J Emerg Med. 2000; 7: 271-275Crossref Scopus (6) Google Scholar35Kress JP Noth I Hall JB et al.The utility of albuterol nebulized with heliox during acute asthma exacerbations.Am J Respir Crit Care Med. 2002; 165: 1317-1321Crossref PubMed Scopus (89) Google Scholar36Rose JS Panacek EA Miller P Prospective randomized trial of heliox-driven continuous nebulizers in the treatment of asthma in the emergency department.J Emerg Med. 2002; 22: 133-137Abstract Full Text Full Text PDF PubMed Scopus (36) Google Scholar of heliox in acute severe asthma published between 1996 and 2002. Five of these studies used peak expiratory flow rate (PEFR) as the main variable.29Carter ER Webb CRT Moffit DR Evaluation of heliox in children hospitalized with acute severe asthma.Chest. 1996; 109: 1256-1261Abstract Full Text Full Text PDF PubMed Scopus (115) Google Scholar30Kudukis TM Manthous CA Schmidt GA et al.Inhaled helium–oxygen revisited: effect of inhaled helium-oxygen during the treatment of status asthmaticus in children.J Pediatr. 1997; 130: 217-224Abstract Full Text Full Text PDF PubMed Scopus (143) Google Scholar31Kass JE Terregino CA The effect of heliox in acute severe asthma: a randomized controlled trial.Chest. 1999; 116: 296-300Abstract Full Text Full Text PDF PubMed Scopus (111) Google Scholar32Henderson SO Acharya P Kilaghbian T et al.Use of heliox-driven nebulizer therapy in the treatment of acute asthma.Ann Emerg Med. 1999; 33: 141-146Abstract Full Text Full Text PDF PubMed Scopus (73) Google Scholar33Dorfman TA Shipley ER Burton JH et al.Inhaled heliox does not benefit ED patients with moderate to severe asthma [letter].Am J Emerg Med. 2000; 18: 495-497Abstract Full Text Full Text PDF PubMed Scopus (33) Google Scholar Two trials studied only children,29Carter ER Webb CRT Moffit DR Evaluation of heliox in children hospitalized with acute severe asthma.Chest. 1996; 109: 1256-1261Abstract Full Text Full Text PDF PubMed Scopus (115) Google Scholar30Kudukis TM Manthous CA Schmidt GA et al.Inhaled helium–oxygen revisited: effect of inhaled helium-oxygen during the treatment of status asthmaticus in children.J Pediatr. 1997; 130: 217-224Abstract Full Text Full Text PDF PubMed Scopus (143) Google Scholar two trials studied only adults,31Kass JE Terregino CA The effect of heliox in acute severe asthma: a randomized controlled trial.Chest. 1999; 116: 296-300Abstract Full Text Full Text PDF PubMed Scopus (111) Google Scholar32Henderson SO Acharya P Kilaghbian T et al.Use of heliox-driven nebulizer therapy in the treatment of acute asthma.Ann Emerg Med. 1999; 33: 141-146Abstract Full Text Full Text PDF PubMed Scopus (73) Google Scholar and one trial included both children and adults.33Dorfman TA Shipley ER Burton JH et al.Inhaled heliox does not benefit ED patients with moderate to severe asthma [letter].Am J Emerg Med. 2000; 18: 495-497Abstract Full Text Full Text PDF PubMed Scopus (33) Google Scholar One trial30Kudukis TM Manthous CA Schmidt GA et al.Inhaled helium–oxygen revisited: effect of inhaled helium-oxygen during the treatment of status asthmaticus in children.J Pediatr. 1997; 130: 217-224Abstract Full Text Full Text PDF PubMed Scopus (143) Google Scholar with children was excluded because it did not include percent predicted PEFR values. The data from the remaining four studies were pooled and evaluated with a meta-analysis. The authors found a small benefit in PEFR and dyspnea index with heliox and commented that the difference may have been even greater if the fifth study had been included. They also suggested that patients with more severe asthma might benefit more from heliox. Markedly successful anecdotal reports of heliox treatment in asthma patients have been both a blessing and a curse for heliox. They have led to a wider but indiscriminate usage of heliox. In both of the hospitals where I have conducted clinical trials with heliox in asthma patients, its use in treating a small number of patients who had rapid and marked improvement with heliox has led to its regular use in patients with severe asthma. In reviewing the medical literature on heliox in asthma, Ho et al found that of the 13 randomized and nonrandomized clinical trials, 10 showed a benefit with heliox and 3 did not. However, even after the publication of randomized controlled trials of heliox in asthmatic patients, there was no widespread acceptance of heliox therapy. Despite the fact that heliox does not lead to improvement in every patient, it still has clinical value when used with the appropriate patients. So who should receive heliox? Presently, it should be reserved for the “brittle” asthmatic patient who does not quickly respond to inhaled β-agonist therapy and who has any of the following characteristics: 1.Severe airflow obstruction (ie, PEFR, < 30% predicted) and a rapid onset of exacerbation of symptoms preferably over < 24 h but no > 72 h;2.A history of labile asthma and/or previous tracheal intubation for asthma; and3.The inability to be adequately ventilated on mechanical ventilation. How should heliox be used? 1.It should be started as soon as possible.2.If there is no subjective or objective improvement within a few minutes, alternative therapies should sought out. The main danger of heliox is continuing it too long when there is no benefit.3.It should be used for at least 1 h but usually is not needed beyond 8 h. Every hour or two, the heliox can be removed and the patient can be assessed for deterioration over a few minutes.4.The more severe the patient's condition is, the higher the percentage of helium should be, with a maximum of 80% and a minimum of 60%. As stated by Ho et al, further studies are needed, specifically to ascertain whether heliox reduces the incidence of endotracheal intubation. Since it is but a therapeutic bridge until the effect of corticosteroids occurs, it is unlikely that it will reduce hospital admissions, hospital or ICU length of stay, or hospital mortality. It will provide rapid and marked relief of dyspnea to many patients without any detrimental effects. Since its therapeutic index is so high and its onset and offset of action are so rapid, it may find a useful niche in the prehospital setting when used by emergency medical technicians and possibly by an occasional labile asthmatic patient at home.
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