tailieunhanh - Ebook Care of the newborn - A handbook for primary care: Part 2

(BQ) Part 1 book “Care of the newborn - A handbook for primary care” has contents: Infectious diseases, neonatal neurology, necrotizing enterocolitis, abdominal surgical emergencies, hematologic disorders, stabilization and preparation of the infant for transport, . and other contents. | 2/25/04 8:50 PM Page 108 11 I. II. Oxygen: Use and Monitoring Matthew E. Abrams and Neal Simon Description of the issue . Oxygen is an important and frequently used therapy in the care of ill newborns. This chapter addresses oxygen physiology, the risks and benefits of oxygen therapy, blood gas analysis, oxygen delivery systems, blood sampling techniques, and noninvasive blood gas monitoring. Oxygen physiology. The amount of oxygen available to body tissues depends, in part, on the environmental oxygen concentration, the amount of oxygen in the airways, and, ultimately, the amount of oxygen in the blood. FIO2 refers to the fraction of oxygen in inspired air and is expressed as a percentage, for example, 21%, or in decimal form, for example, . PAO2, measured in mm Hg, is the partial pressure of oxygen in the gas mixture delivered to the alveoli, whereas PaO2, also measured in mm Hg, is the partial pressure of oxygen in the arterial blood. Oxygen is transported in blood either freely dissolved or bound to hemoglobin (Hb) within the red blood cell. The oxyhemoglobin saturation (SaO2) is the percentage of Hb that is carrying oxygen. The amount of oxygen available to the tissues is determined not only by the amount of oxygen in the blood, that is, oxygen content, but also by how effectively the oxygen is supplied to the tissues, that is, oxygen delivery. Both oxygen content and oxygen delivery and the factors that influence them are defined in the following paragraphs. The total oxygen content of the blood is the sum of the oxygen bound to Hb plus the dissolved oxygen. Because the amount of dissolved oxygen contributes little to the total oxygen content, the simplified equation for oxygen content of the blood is: O2 content Hb SaO2 By increasing the oxygen saturation, for example, from 80% to 100% at a constant Hb level, the oxygen content will increase by approximately 25%. In most instances, the oxygen saturation can be elevated by .