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George W Rodway

Publications and source records attributed to George W Rodway.

10 recordsLinked to original sources
PubMed2006

Supplemental oxygen and sleep at altitude.

Windsor, Jeremy S., and George W. Rodway. Supplemental oxygen and sleep at altitude. High Alt. Med. Biol. 7:307-311, 2006.--The purpose of this study was to examine the effect supplemental oxygen has on the respiratory and cardiovascular system of a mountaineer during sleep at high altitude by using a novel ambulatory, multisensor, continuous monitoring device. Supplemental oxygen was administered to a healthy subject via a nasal demand system (0, 16.7, 33.3, or 50 mL/sec per pulse dose delivered over 1 sec) during the first three nights of sleep at 4900 and 5700 m. Increases in pulse dose resulted in a consistent rise in Sa(O(2)) and a fall in minute ventilation (p < 0.05). The 50-mL pulse dose resulted in the greatest changes, with an increase in Sa(O(2)) from 68.5% to 81% (p < 0.05) and a fall in minute ventilation from 13.1 to 10.9 L/min (p < 0.05) being noted. Changes in Sa(O(2)) and minute ventilation also coincided with a fall in apnea/hypopnea index (AHI). At 4900 m the AHI fell from 12.5-52.3 (breathing air) to 0-7.5 (50-mL oxygen pulse), whereas at 5700 m a decrease from 49.1-80.4 to 3.5-10.0 was observed. No changes in respiratory rate or heart rate were identified when different pulse doses were compared (p < 0.05). The multisensor monitoring device proved to be a highly effective system, demonstrating marked improvements in Sa(O(2)), tidal volume, and AHI in our participant when supplemental oxygen was administered via a nasal demand system.

Administration, Intranasal↗
PubMed2006

Markers of lung disease in exhaled breath: nitric oxide.

Management of airway inflammation requires proper monitoring and treatment to improve long-term outcomes. However, achieving this goal is difficult, as current methods have limitations. Although nitric oxide (NO) was first identified 200 years ago, its physiological importance was not recognized until the early 1980s. Many studies have established the role of NO as an essential messenger molecule in body systems. In addition, studies have demonstrated a significant relationship between changes in exhaled NO levels and other markers of airway inflammation. The technique used to measure NO in exhaled breath is noninvasive, reproducible, sensitive, and easy to perform. Consequently, there is growing interest in the use of exhaled NO in the management of asthma and other pulmonary conditions. The purpose of this review is to promote a basic understanding of the physiologic actions of NO, measurement techniques, and ways that research findings might translate to future application in clinical practice. Specifically, the article will review the role of exhaled NO in regard to its historical background, mechanisms of action, measurement techniques, and implications for clinical practice and research.

Asthma↗
PubMed2006

Airway mucociliary function at high altitude.

Despite the presence of a number of anecdotal reports in the mountaineering literature, mucociliary dysfunction at high altitude has received little scientific attention. However, the dry, cold, thin air at high altitude has the potential to undermine normal mucociliary function. This seems increasingly likely in mountaineers who also experience dehydration, nasal obstruction, and extremes of aerobic respiration when climbing in such environments. These factors may result in a number of clinical conditions that range from sore throats and coughs commonly seen at altitude to rarer cases of bronchiolar collapse and lung atelectasis. The purpose of this review is to discuss the etiology of mucociliary dysfunction at altitude and outline a number of potential solutions to the problems this phenomenon presents.

Altitude↗
PubMed2005

The use of closed-circuit oxygen in the Himalayas.

Two days before the first ascent of Mt. Everest in 1953, Tom Bourdillon and Charles Evans climbed to within 90 m of the summit at unprecedented speeds. By breathing pure oxygen from a closed circuit, the pair were able to obtain an enormous physiological advantage. Unfortunately, due to a malfunction in Evans's circuit, the pair abandoned their attempt on the South Summit. For many who used the circuit in the 1930s and 1950s, the device proved too heavy, uncomfortable, and tiring for mountaineering. These factors, together with the wider ethical concerns of using supplemental oxygen at altitude, have meant that closed-circuit oxygen has been ignored for more than 50 years. In this article the authors will attempt to describe the history of this discarded circuit and the experience of those who utilized it.

Altitude Sickness↗
PubMed2005

Mt. Kellas.

Explore the source record for details and available documents.

Expeditions↗
PubMed2004

Prelude to Everest: Alexander M. Kellas and the 1920 high altitude scientific expedition to Kamet.

Following his untimely death due to illness during the early stages of the first Mount Everest Reconnaissance Expedition in 1921, Alexander M. Kellas has received relatively little attention in either mountaineering or scientific literature. He remains an obscure figure despite his noteworthy contributions to high altitude physiology and exploration. He can be considered not only one of the finest exploratory Himalayan mountaineers in history, but also the first person to apply state-of-the-art knowledge of high altitude physiology to field investigations at altitudes over 6000 m. By the time of his death, it is extremely likely that Kellas had spent more time above 6000 m than anyone on Earth, undertaking no fewer than eight Himalayan expeditions between 1907 and 1921. This article revisits and examines in some detail the most ambitious high altitude physiological field study undertaken through the second decade of the 20th century, A. M. Kellas and Henry T. Morshead's 1920 Kamet Expedition. This undertaking by Kellas and Morshead was unique because it specifically emphasized investigation of the practical difficulties inherent in climbing at very high altitudes. During this endeavor, Kellas carried out the first rigorous tests of the value of supplementary oxygen for climbing at high altitude. The results of the field studies conducted during the 1920 Kamet Expedition provided strong support for the use of supplementary oxygen at high altitude. However, after Kellas died on the approach march to Everest the following year, the British mountaineering establishment did not again have a similar proponent or exponent of extreme altitude field research until physiologist Griffith Pugh once again took up the challenge in the early 1950s.

Altitude Sickness↗
PubMed2003

The efficacy of split-night sleep studies.

Positive airway pressure (PAP) therapy is the most commonly used medical modality to reverse the apneas, hypopneas and inspiratory flow-limited breaths which result in the oxyhemoglobin desaturation, altered sleep architecture, and daytime sleepiness representing the cardinal features of obstructive sleep apnea/hypopnea (OSA/H). Identifying optimal strategies to develop the initial positive airway prescription is of paramount importance to clinicians who evaluate patients with suspected OSA/H. In addition, with the growing appreciation of the clinical and physiologic importance of sleep-disordered breathing, there have been increasing demands on clinical resources to diagnose and treat these patients. The time, hardware, and personnel-intensive nature of in-laboratory polysomnography (PSG) are significant in light of the traditional paradigm that utilizes a full night PSG for a diagnostic evaluation and when indicated, another full night for PAP titration. Efforts to identify time and resource-conserving alternatives to this paradigm have focused on in-laboratory split-night studies, in which the diagnosis of OSA/H can be made, and a positive pressure prescription defined during a single overnight PSG. Case-control studies indicate that, when certain guidelines are applied, split-night PSGs result in prescription efficacy and patient adherence, which are comparable to the traditional two-night strategy. However, prospective, randomized trials designed with adequate power are required to further define the impact of a split-night strategy on clinical outcome. As more information becomes available regarding the factors that determine long-term adherence to positive pressure therapy, the potential for efficient, expeditious treatment, and cost savings with split-night sleep studies will likely receive greater attention.

Disorders of Excessive Somnolence↗
PubMedDate not supplied

High-altitude-related disorders--Part I: Pathophysiology, differential diagnosis, and treatment.

As increasing numbers of people choose to sojourn or retire to the mountains, high-altitude illness is becoming a pathological phenomenon about which healthcare providers should have greater awareness. Hypoxia is the primary cause of high-altitude illness, but other stressors on the sympathetic nervous system, such as cold and exertion, also contribute to disease development and progression. Although variable across persons, symptoms of high-altitude disorders usually occur at altitudes over 7000 feet, and typically in 1 of 3 forms: acute mountain sickness (AMS), high-altitude cerebral edema (HACE), or high-altitude pulmonary edema (HAPE). Major symptoms include nausea, poor sleep, headache, lassitude, cough, dyspnea on exertion and at rest, ataxia, and mental status changes. As a rule, illness occurring at high altitude should be attributed to the altitude until proven otherwise. Treatment is best accomplished by descent and by oxygen or pharmacologic intervention if necessary. Under no circumstances should a person with worsening symptoms of high-altitude illness delay descent. As will be discussed in part II of this article, gradual ascent and subsequent acclimatization to altitude is the most effective prevention, though acetazolamide (Diamox) may be a useful prophylactic measure in some.

Acetazolamide↗
PubMedDate not supplied

High-altitude-related disorders--Part II: prevention, special populations, and chronic medical conditions.

This second section of a 2-part review on high-altitude-related disorders focuses on strategies for prevention of high-altitude illness, identification of populations at increased risk for high-altitude illness, and effects of high altitude on selected chronic medical conditions. Practical aspects of advising and educating patients traveling to high altitude will be discussed, with special reference to pregnant women, infants and young children, healthy elders, and chronic medical conditions that may place persons at greater risk for high-altitude illness. The special concerns of pre-verbal children will be covered relative to the risks of high altitude for those too young to voice symptoms of illness and, thus, at-risk for potential serious consequences caused by delay in diagnosis and treatment.

Age Factors↗