Oxygen Use in Critical Illness.

Oxygen is the most commonly used drug in critical care. However, because it is a gas, most clinicians and most patients do not regard it as a drug. For this reason, the use of medical oxygen over the past century has been driven by custom, practice, and "precautionary principles" rather than by scientific principles. Oxygen is a life-saving drug for patients with severe hypoxemia, but, as with all other drugs, too much can be harmful. It has been known for many decades that the administration of supplemental oxygen is hazardous for some patients with COPD and other patients who are vulnerable to retention of carbon dioxide (ie, hypercapnia). It has been recognized more recently that excessive oxygen therapy is associated with significantly increased mortality in critically ill patients, even in the absence of risk factors for hypercapnia. This paper provides a critical overview of past and present oxygen use for critically ill patients and will provide guidance for safer oxygen use in the future.

100 years of the Royal Air Force's contribution to medicine: providing care in the air and delivering care by air.

The Royal Air Force (RAF) came into being during World War I as the world's first independent air force on the 1 April 1918, amalgamating elements of the Royal Flying Corps (RFC), itself established in 1912 and the Royal Naval Air Service which had formally separated from the Admiralty's administered Air Wing of the RFC in 1915. The RAF therefore celebrates its 100th anniversary in the same year that the Royal College of Physicians of London celebrates its 500th. This article will cover the contribution that military aviation has made to medicine since 1913 with the emphasis of three examples focusing on delivering care by air, providing care in the air and in developing systems for supporting aircrew or patients at the extremes of physiological stress.

The story of oxygen.

The history of oxygen from discovery to clinical application for patients with chronic lung disease represents a long and storied journey. Within a relatively short period, early investigators not only discovered oxygen but also recognized its importance to life and its role in respiration. The application of oxygen to chronic lung disease, however, took several centuries. In the modern era, physiologists pursued the chemical nature of oxygen and its physiologic interaction with cellular metabolism and gas transport. It took brazen clinicians, however, to pursue oxygen as a therapeutic resource for patients with chronic lung disease because of the concern in the 20th century of the risks of oxygen toxicity. Application of ambulatory oxygen devices allowed landmark investigations of the long-term effects of continuous oxygen that established its safety and efficacy. Although now well established for hypoxic patients, many questions remain regarding the benefits of oxygen for varying severity and types of chronic lung disease.

Oxygen in respiratory care: a personal perspective from 40 years in the field.

Oxygen is necessary for all aerobic life, and nothing is more important in respiratory care than its proper understanding, assessment, and administration. By the early 1970s P(aO(2)) had become the gold standard for clinically assessing oxygenation in the body. Since the 1980s the measurement of arterial oxygen saturation by pulse oximetry has also been increasingly used as an adjunct to (but not a replacement for) P(aO(2)). Despite the desirability of measuring tissue oxygenation directly, no reliable and clinically relevant such measure has emerged. The 2 areas in which oxygen has proven most important in respiratory care are long-term oxygen therapy (LTOT) and the management of potentially life-threatening hypoxemia in acute respiratory failure. That LTOT improves survival in appropriately selected patients with COPD was demonstrated by multicenter studies published more than 30 years ago, and their original selection criteria have so far not been improved upon. Severe hypoxemia in acute lung injury and ARDS can be improved by ventilation with PEEP, and also in many patients by various adjunctive techniques and alternative support strategies. However, the latter measures have not brought clear improvements in survival or other patient-relevant outcomes. In addition, the original goals of "normalizing" arterial oxygenation with high tidal volumes and lung-distending pressures have required modification as appreciation for ventilator-related lung injury has emerged. High concentrations of inspired oxygen may play a role in such injury, but aggressive measures to reduce them in order to avoid oxygen toxicity-which dominated ventilator management in previous decades-have been tempered in the present era of lung-protective ventilation. Although some additions and modifications have emerged, much of what we understand today about oxygen in respiratory care is owed to the pioneering work of Thomas L Petty more than 40 years ago.

The history of oxygen inhalation as a treatment for cluster headache.

OVERVIEW: Oxygen has been a generally accepted treatment method for cluster headache attacks ever since Kudrow (1981) conducted a controlled trial showing that oxygen was equally or even more effective than ergotamine injections. PURPOSE: The aim of the present study was to provide a historical perspective of oxygen treatment in cluster headache and to find the origin of this treatment. Oxygen for cluster headache was first described by Horton in 1952 and for migraine patients in 1940 by Alvarez. At the time, neither of the authors provided any reason why they chose for this treatment method. The vasoconstrictive effect of oxygen was not described by Horton until 1961. CONCLUSION: We suggest that these authors originally adhered to the vasoconstrictive theory of vascular headache that was prevalent in the early 20th century until Wolff demonstrated the contrary in the late 1930s. The early literature describes an analogy between angina pectoris and migraine, as both being due to vasoconstriction. As oxygen was described as a treatment for angina pectoris, this may be the reason why oxygen was tried for migraine and cluster headache at a time when they were not recognized as separate entities. Later it turned out to be more effective for cluster headache.

A brief history of pulmonary rehabilitation.

Pulmonary rehabilitation is widely accepted as effective therapy for patients with chronic obstructive pulmonary disease (COPD). This paper presents a brief (and somewhat subjective) history of pulmonary rehabilitation, and stresses the development of the exercise component. Until the middle of the 20th century, patients with COPD were advised to avoid the dyspnea that activity brings. Barach can be credited with positing that patients with COPD should strive to be more active. In the 1960s Petty created the multi-disciplinary team that was found to be effective in delivering pulmonary rehabilitation. In the 1980s doubts surfaced as to the ability of rehabilitative exercise to improve muscle function in COPD, but in the 1990s studies showed that well-designed exercise programs caused beneficial physiologic adaptations. The current decade has yielded studies that exploited those insights to design interventions that boost the effectiveness of rehabilitative exercise.

Georges Dreyer (1873-1934) and a forgotten episode of respiratory physiology at Oxford.

Georges Dreyer was the first Professor of Pathology at Oxford University and he held this post from 1907 to 1934. Although his main research interests were in bacteriology and immunity, he made important contributions to respiratory physiology, but these have been almost completely forgotten. He developed a new apparatus for administering low oxygen mixtures to test the effects of hypoxia in airmen during World War I, developed a high successful oxygen delivery system, was responsible for the first low-pressure chamber in a UK academic institution, and carried out some physiological measurements in the chamber that were years ahead of their time. His chamber was also used by a group from Cambridge and Turin, Italy for a series of important physiological studies. In spite of these contributions, almost nobody who works in respiratory physiology today, even in Oxford, recognizes the name of Dreyer.

The Robinson-Hooper connection*.

The search for a connection between James Robinson, the dental surgeon who on 19 December 1846 administered the first general anaesthetic in England by the inhalation of the vapour of ether, and William Hooper, the pharmaceutical chemist who produced the best publicised and most widely used of the early commercial ether vaporisers, has revealed hitherto unrecognised aspects of the early history of general anaesthesia.

The history of COPD.

The evolution of knowledge concerning COPD and its components--emphysema, chronic bronchitis, and asthmatic bronchitis--covers 200 years. The stethoscope and spirometer became important early tools in diagnosis and assessment. Spirometry remains the most effective means of identification and assessment of the course of COPD and responses to therapy, and is grossly underused for this purpose. Knowledge of the pathogenesis, course and prognosis, and new approaches to therapy have dramatically improved our understanding of this important clinical entity. Smoking cessation improves the early course of disease. Long-term oxygen improves the length and quality of life in selected patients with hypoxemia. Surgery benefits a select few. Today, COPD is a steadily growing global healthcare problem, with increasing morbidity and mortality. Early identification and prevention, and treatment of emerging stages of disease through smoking cessation and a growing number of bronchoactive drugs promises to change the outcome.