JAMA - Journal of the American Medical Association

The Journal of the American Medical Association

Reprinted from The Journal of the American Medical Association October 28, 1992

Standards and Guidelines for Cardiopulmonary Resuscitation (CPR) and Emergency Cardiac Care (ECC)  Basic Life Support (BLS)

Oxygenation Devices
Supplemental oxygen should be used during cardiopulmonary emergencies as soon as available. Rescue breathing (ventilation using exhaled air) will delivery about 16% to 17% oxygen to the patient, ideally producing an alveolar oxygen tension of 80 mm Hg.

Hypoxemia occurs because of underlying respiratory disease or low cardiac output (and resultant wide arteriovenous oxygen difference) and the presence of intrapulmonary shunting and ventilation perfusion abnormalities.

In turn, hypoxemia leads to anaerobic metabolism and metabolic acidosis, which can frequently blunt the beneficial effects of chemical and electric therapy. Thus, it is recommended that 100% inspired oxygen (FiO2-1.0) be used during BLS and ACLS.

Supplemental oxygen reduces both the magnitude and the extent of ST-segment changes on the EGG in patients with acute ML2. For patients with chronic obstructive lung disease and carbon dioxide retention, lower inspired oxygen flow rates may be necessary (eg. 1 to 2 L/min).

However, oxygen should not be withheld for fear of suppressing respiration if hypoxemia is suspected or if significant respiratory distress is present.

Corrections of Hypoxemia with Oxygen Therapy 

The highest possible oxygen concentration (preferably 100%) should be administered as soon as possible to all patients with cardiac or pulmonary arrest or other patients with suspected hypoxemia regardless of cause (class I). 

Oxygen will increase arterial oxygen tension and hemoglobin saturation if ventilation is supported and will improve tissue oxygenation when circulation also is maintained. 

Masks 

A well fitting mask can be an effective, simple adjunct for use in artificial ventilation by appropriately trained rescuers. Masks should be made of transparent material to allow detection of regurgitation; capable of a tight fit on the face with an oxygen (insufflation) inlet of a standard 15-mm/22 mm coupling size; and available in one average size for adults with additional sizes for infants and children. 

Masks equipped with a one-way valve that diverts the victim’s exhaled gas are recommended for mouth-to-mask ventilation. Mouth-to-mask has been shown to be superior to bag-valve-mask devices in delivering tidal volumes on manikins.

**Unfortunately studies in humans are lacking. These devices are not to be confused with face shield devices, which do not have an exhalation port. The efficacy of face shields has not been compared with that of other devices and at this time face shields should be considered Class IIB (acceptable, possibly helpful). Such devices are for BLS only.

An adequate seal is best achieved with mouth-to-mask device when the rescuer is positioned at the top of the patient’s head. The rescuer ventilates the victim by sealing his or her lips around the coupling adapter of the mask. Both hands should be used to maintain airway patency and a secure mask fit.