NetWorks: Uranium mining, hyperoxia, palliative care education, OSA impact

Occupational and Environmental Health Respiratory Care Palliative and End-of-Life Care Sleep Medicine

Publish date: April 6, 2017

 

Health effects of uranium mining

Decay series of U 238

Prior to 1900, uranium was used only for coloring glass. After discovery of radium by Madame Curie in 1898, uranium was widely mined to obtain radium (a decay product of uranium).

While uranium was not directly mined until 1900, uranium contaminates were in the ore in silver and cobalt mines in Czechoslovakia, which were heavily mined in the 18th and 19th centuries.

With permission from the Canadian Nuclear Safety Commission.

Increased mortality was described in these miners in 1770. In 1878, Harting and Hesse (a public health officer and a local mine physician) described 23% mortality from lung cancer in 650 Schneeberg cobalt miners over 10 years. By the 1920s, 50% of exposed miners were dying of lung cancer.

There were no reports (written in English) of lung cancer associated with radiation until 1942; but in 1944, these results were called into question in a monograph from the National Cancer Institute. The carcinogenicity of radon was confirmed in 1951; however, this remained an internal government document until 1980. By 1967, the increased prevalence of lung cancer in uranium miners was widely known. By 1970, new ventilation standards for uranium mines were established.

Lung cancer risk associated with uranium mining is the result of exposure to radon gas and specifically radon progeny of Polonium 218 and 210. These radon progeny remain suspended in air, attached to ambient particles (diesel exhaust, silica) and are then inhaled into the lung, where they tend to precipitate on the major airways. Polonium 218 and 210 are alpha emitters, which have a 20-fold increase in energy compared with gamma rays (the primary radiation source in radiation therapy). Given the mass of alpha particles (two protons and two neutrons), they interact with superficial tissues; thus, once deposited in the large airways, a large radiation dose is directed to the respiratory epithelium of these airways.

Occupational control of exposure to radon and radon progeny is accomplished primarily by ventilation. In high-grade deposits of uranium, such as the 20% ore grades in the Athabasca Basin of Saskatchewan, remote control mining is performed.

Smoking, in combination with occupational exposure to radon progeny, carries a greater than additive but less than multiplicative risk of lung cancer.

In addition to the lung cancer risk associated with radon progeny exposure, uranium miners share the occupational risks of other miners: exposure to silica and diesel exhaust. Miners are also at risk for traumatic injuries, including electrocution.

Health effects associated with uranium milling, enrichment, and tailings will be discussed in a subsequent CHEST Physician article.

Richard B. Evans, MD, MPH, FCCP

Steering Committee Chair

Hyperoxia in critically ill patients: What’s the verdict?

Oxygen saturation is considered to be the “fifth vital sign,” and current guidelines recommend target oxygen saturation (SpO2) between 94% and 98%, with lower targets for patients at risk for hypercapnic respiratory failure (O’Driscoll BR et al. Thorax. 2008;63(suppl):vi1). Oxygen toxicity is well-demonstrated in experimental animal studies. While its incidence and impact on outcomes is difficult to determine in the clinical setting, increases in-hospital mortality have been associated with hyperoxia in patients with cardiac arrest, acute myocardial infarction, and stroke (Kligannon et al. JAMA. 2010;303[21]:2165; Stub et al. Circulation. 2015;131[24]:2143; Rincon et al. Crit Care Med. 2014;42[2]:387).

Dr. Amanpreet Kaur

Girardis and colleagues examined the impact of conservative oxygen administration (PaO2 maintained between 70-100 mm Hg or SpO2 between 94-98%) vs standard care group (permitting PaO2 values up to 150 mm Hg or SpO2 values between 97-100%) in ICU patients admitted for at least 72 hours (Girardis et al. JAMA. 2016;316 [15]:1583). There were striking differences in ICU mortality between the two groups with absolute risk reduction of 8.6% (P = .01) favoring the conservative oxygen therapy group, as well as significant reductions in episodes of shock, liver failure, and bacteremia. However, there were baseline differences in the severity of illness between the two groups: the use of a modified intention to treat analysis and the early termination of the trial mitigate the robustness of these findings.

Complementing the findings of Girardis and colleagues, a recent analysis of more than 14,000 critically ill patients, found that time spent at PaO2 > 200 mm Hg was associated with excess mortality and fewer ventilator-free days (Helmerhorst et al. Crit Care Med. 2017;45[2]:187).

While other trials demonstrated safety and feasibility of conservative oxygen therapy in critically ill patients (Panwar et al. Am J Respir Crit Care Med. 2016;193[1]:43; Helmerhorst et al. Crit Care Med. 2016; 44[3]:554; Suzuki et al. Crit Care Med. 2014;42[6]:1414), they did not find significant differences between conservative and liberal oxygen therapy with regards to new organ dysfunction or mortality. However, the degree of hyperoxia was usually more modest than in either the Girardis trial or the Helmerhorst (2017) analysis.

Dr. David L. Bowton

Based on current evidence, it seems appropriate to maintain physiologically normal levels of PaO2 without causing hyperoxia in critically ill patients. Oxygen saturation greater than 97% or 98% for prolonged periods should be avoided. Further randomized controlled trials are needed to more clearly elucidate appropriate targets for oxygenation and their impact on patient outcomes.

Amanpreet Kaur, MD

Steering Committee Fellow-in-Training

David L. Bowton, MD, FCCP

Steering Committee Chair

Education in palliative medicine

Prompted by concerns that the Affordable Care Act would be instituting “death panels” as part of cost-containment measures, “Dying in America” (a 2015 report of the Institute of Medicine [IOM]) identified compassionate, affordable, and effective care for patients at the end of their lives as a “national priority” in American health care. The IOM identified the education of all primary care providers in the delivery of basic palliative care, specifically commenting that all clinicians who manage patients with serious, life-threatening illnesses should be “competent in basic palliative care” (IOM, The National Academies Press 2015).

Dr. Laura Johnson

Considerable effort has been put into providing clinicians with tools to gain this competence. Resources exist from organizations, ranging from the American Academy of Hospice and Palliative Medicine to the American College of Surgeons. Numerous publications address everything from symptom management to teaching communication skills to medical students and residents. But the question remains – can physicians who have been trained to “tread with care in matters of life and death” balance comfort with cure (Lasagna 1964, Modern Hippocratic Oath)? We believe the answer ultimately is yes, and that this balance may prove to be the antidote to the pervasive issues of burnout that plague our profession.

Check out our NetWork Storify page later this year for links to the ongoing discussion surrounding palliative care in medicine and for useful tools in the effort to provide palliative care to all our patients.

Laura Johnson, MD, FCCP

Steering Committee Vice Chair

The impact of sleep apnea: Why should we care?

With recent large trials such as the SAVE and the SERVE-HF studies challenging the cardiovascular benefits of treating sleep-disordered breathing in specific patient subsets, many physicians may start to question, “Why all the fuss?” The Sleep NetWork is bringing the leaders in the field to CHEST 2017 to discuss their take on where we stand with the connection between sleep-disordered breathing and cardiovascular disease, so stay tuned!

Dr. Aneesa Das

Meanwhile, we might reflect on the safety, social, and economic impacts of OSA and its treatment. Sleepiness due to OSA significantly affects driving performance and has received significant attention from the Federal Motor Carrier Safety Administration (FMCSA). Patients with OSA are six times more likely to have a motor vehicle crash than those without OSA (Terán-Santos et al. N Engl J Med. 1999;340[11]:847). One transportation company, Schneider, has incorporated an OSA screening and treatment program and reported a 73% reduction in preventable driving accidents.

Our relationships, general health, and work productivity can be affected by untreated OSA. The effect on daily life may not be initially obvious. Patients often present only at the insistence of their partner or physician, only to be surprised at how much better they feel once treated. Symptoms of OSA are associated with a higher rate of impaired work performance, sick leave, and divorce (Grunstein et al. Sleep. 1995;18[8]:635). A recent survey estimates an $86.9 billion loss of workplace productivity due to sleep apnea in 2015 (Frost & Sullivan. Hidden health crisis costing America billions. AASM; 2016. http://www.aasmnet.org/Resources/pdf/sleep-apnea-economic-crisis.pdf. Accessed March 21, 2017.). The same survey found that among those who are employed, treating OSA was associated with a decline in absences by 1.8 days per year and an increase in productivity 17.3% on average. Considering that the majority of OSA remains undiagnosed, this could have tremendous economic impact.

OSA is an important public health burden. The Sleep NetWork is committed to increasing awareness among individuals (patients and clinicians) and institutions (transportation agencies, government) of the impact of sleep-disordered breathing on society.

Aneesa Das, MD, FCCP

Steering Committee Chair

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