In acute respiratory failure, an immediate restoration of respiratory functions is imperative. Depending upon the available equipment and the qualifications of the physician and nursing staff, the most suitable ventilation procedure should be selected. In every case, accurate ventilation is accomplished by Intermittent Positive Pressure Ventilation (IPPV). If emergency equipment is not available, the simplest method of achieving this is mouth-to-mouth or mouth-to-nose breathing. The efficacy of this method is limited by the low FiO2 (about 17%) and by the physical condition of the first aider; after 30 minutes of resuscitation, even an experienced and well conditioned emergency rescuer will be exhausted.