Arach in 1935 was the first to use helium to improve air flow in patients with airways obstruction, but it was soon cast aside for other treatment modalities. Since then, it has been relegated mainly to use in upper airway obstruction or to diagnostic studies. Safety and efficacy have been demonstrated for both spontaneously breathing patients and for intubated patients receiving mechanical ventilation, but its therapeutic potential has not been fully explored.
Helium has no bronchodilating or anti-inflammatory properties and in fact is quite inert. Since airway resistance in turbulent flow is directly related to the density of the gas, helium, with its lower density than nitrogen or oxygen, results in lower airway resistance. Helium further lowers airway resistance by reducing the Reynolds number, such that some areas of turbulent flow are converted to laminar flow. The reduction in airway resistance results in a decreased work of breathing.
Although the mortality from asthma is rising, there has been a paucity of new treatments for acute severe asthma. Previous reports have shown an almost universal response to heliox in acute severe asthma. We wish to report our experience with heliox and our attempt to better define its utility by discerning patterns of response.
www.canadianhealthnews.com – health blog in Canada.
Over a 2-year period (1988 to 1990) there were 312 patients, 179 women and 133 men, admitted to Mount Sinai Hospital in Hartford Conn, with acute asthma. Twelve (3.8%) of these patients had an acute respiratory acidosis as defined by a pH of 45 mm Hg. All were treated with a heliox mixture containing 60 to 70% helium and 30 to 40% oxygen. There were nine men and three women. The mean age was 33.8± 11.3 years. They had asthma for 23.4±9.6 years. Four of the patients had been intubated in the past. Eleven of the 12 patients were receiving maintenance agonist metered-dose inhaler therapy. Eight of the 12 were taking oral theophylline. One was using ipratroprium bromide by metered-dose inhaler. None of the patients was being treated with inhaled or oral corticosteroids.