Every day, thousands of calls are generated to emergency medical systems seeking help for many reasons. One of the scariest calls a dispatcher can receive is one involving a patient who is not breathing or having difficulty breathing. A very common problem, invisible due to its colorless, odorless and tasteless properties, and which constitutes a major public health problem globally, is carbon monoxide poisoning (Graber et al 2007). According to the Journal of the American Medical Association, 2,000 Americans die each year from accidental exposure to carbon monoxide and another 2,300 from intentional exposure (suicide). Carbon monoxide is naturally produced in our bodies in small amounts and released as a byproduct through cellular metabolism (Thompson, 1997). Additionally, we are exposed to relatively low concentrations of carbon monoxide from burning fuel from the motor vehicles we drive daily and from the portable gas heaters we may use in winter to stay warm. Carbon monoxide poisoning can occur anywhere carbon-containing fuels are burned and the supply of oxygen is limited. This may be acute poisoning from exposure to high levels such as fire or low-level poisoning over a longer period. Inhaled through the lungs, carbon monoxide interferes with the blood's ability to carry oxygen to tissues. In the blood, there are millions of red blood cells that contain an intracellular protein called hemoglobin. Each hemoglobin molecule can carry four oxygen molecules. Hemoglobin is the primary means of oxygen transport, carrying approximately 98% of the oxygen in the blood, with the remaining 2% transported in a dissolved state (Porth 2011). If the four subunits... middle of paper ......conditions. It is very important to understand the relationship between oxygen saturation and oxygen partial pressure. Total oxygen content and factors that affect hemoglobin oxygen affinity curves will help to better understand and explain clinical problems when presented with the possibility of carbon monoxide poisoning. References: Graber JM, Macdonald SC, Kass BE, Smith AE, Anderson HA (2007 Carbon monoxide: the case for environmental public health monitoring. Public Health Reports. 122,2,138-144. Hardy KR, Thom SR (1994) Pathophysiology and treatment of carbon monoxide poisoning. Journal of Toxicology – Clinical Toxicology 32, 6, 613-629. Porth Carol Mattson (2011) Essentials of Pathophysiology 3rd ed. et al. Mosby's Clinical Nursing 4th ed.., 1997.