Inhalation of gaseous hydrogen sulfide can reduce or prevent lung injury associated with mechanical ventilation

A study appearing in the July 2010 issue of Anesthesiology is the first to show that inhalation of gaseous hydrogen sulfide can reduce or even prevent lung injury in critical care situations that require mechanical ventilation.

Mechanical ventilators are indispensible life-saving tools for treating critically ill patients, but they can also injure healthy lungs, or make already injured lungs worse, by disrupting lung tissue, which can make patient care more difficult.

"Invasive mechanical ventilation leads to inflammation not only in the lung but in many organs, possibly resulting in multiple organ failure," said study author Alexander Hoetzel, M.D., of the University Hospital Freiburg in Germany. "These problems are still not resolved, and we urgently need new strategies to limit side effects associated with mechanical ventilation."

In the study, Dr. Hoetzel and his team from the Department of Anesthesiology and Critical Care Medicine at the University Hospital Freiburg and at Brigham and Women's Hospital in Boston treated mechanically ventilated mice with low concentrations of inhaled hydrogen sulfide.

Hydrogen sulfide has long been regarded as a highly toxic gas, notorious for giving off an odor comparable to rotten eggs. In low doses, though, the gas has been shown to elicit a suspended animation-like state that offers protective effects to the body's organs.

"Recently, the dogma of hydrogen sulfide only being a toxic waste product has changed," said Dr. Hoetzel. "It has been identified as being produced in the human body, mediating dilatation of vessels or limiting inflammatory responses. Together with other potentially toxic gases (nitric oxide and carbon monoxide), hydrogen sulfide has been classified as a 'gasotransmitter,' which are vitally important in the body's metabolic functions."

One method recognized in helping to protect the lungs in mechanically ventilated patients is to induce hypothermia (lowering the body's temperature). Since hydrogen sulfide was found to induce hypothermia in Dr. Hoetzel's study, the researchers needed to know whether the protective properties of the gas came solely from its ability to lower body temperature.

"We found that even if hydrogen sulfide leads to reduced body temperature as one sign of suspended animation, our results clearly demonstrate that the application of the gas during mechanical ventilation reduces inflammation independently of its effects on body temperature," said Dr. Hoetzel.

Based on the overwhelmingly positive initial results of the study, Dr. Hoetzel and his research group see enormous potential for therapeutic use of hydrogen sulfide.

"We demonstrated that application of this gas can prevent organ injury," he said. "And clinical trials could resolve the question as to whether hydrogen sulfide might exert beneficial effects in patients who depend on ventilator support."