Respiratory care clinics of North America
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The evaluation and management of oxygen delivery (Do2) and consumption (Vo2) of patients with acute medical and surgical illnesses have been subject to controversy and reevaluation. It has been established that a relationship between oxygen delivery and oxygen consumption exists, and is very complex, particularly in diseases in which various factors individually or collectively affect it. The care of critically ill patients routinely involves the manipulation of the Vo2-Do2 relationship, and extensive research, both experimental and clinical, has been done to improve our understanding of this relationship in health and disease with the hope for improved outcomes. ⋯ New noninvasive technologies to measure the adequacy of regional measures of oxygenation are being developed, with gastrointestinal tonometry getting much clinical attention. The exact role of these technologies in the management of critically ill patients, and whether they will improve survival, has not yet been determined. It is likely that the ability to care successfully for critically ill patients will come from a better understanding of not only global, but also regional, cellular, and subcellular metabolism.
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The definitions of hypoxemia and hypoxia, and basic pulmonary anatomy and oxygen delivery are reviewed. Low ambient oxygen, hypoventilation, ventilation-perfusion mismatch, and right-to-left shunt, the four basic mechanisms of hypoxemia are described in detail with patient examples. ⋯ Because getting oxygen into the blood stream is only half the story, mechanisms of tissue hypoxia in the setting of adequate oxygen exchange from the lungs to the blood are discussed. An algorithm is proposed for diagnosing patients who present with hypoxia.
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The ability to accurately assess respiratory function is essential in the management of critically sick patients. Such measurements help in the diagnosis, management, and outcome of the patients. Proper understanding and interpretation of these parameters is of paramount importance. Clinicians should appreciate the benefits and the limitations of these techniques.
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The rationale for using the most appropriate equipment to administer oxygen and medical gas mixtures is presented. The emphasis is placed on delivering an appropriate FiO2 for the patient's pathophysiology. ⋯ The research that supports the use of one device over another is discussed when available. The advantages of high-flow fixed performance equipment are contrasted with low-flow variable performance devices.
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Respir Care Clin N Am · Dec 2000
ReviewOther modalities of oxygen therapy: hyperbaric oxygen, nitric oxide, and ECMO.
Novel therapies for the next decade include hyperbaric oxygen, nitric oxide, and extracorporeal membrane oxygenation. Hyperbaric oxygen delivers oxygen at a pressure greater than one atmosphere and has been used in diseases ranging from decompression sickness to carbon monoxide poisoning. Inhaled nitric oxide, a potent vasodilator, has been used in the acute respiratory distress syndrome and for the diagnosis and treatment of pulmonary hypertension. Extracorporeal membrane oxygenation (ECMO) has been used to provide cardiopulmonary bypass support, particularly in the pediatric and neonatal population.