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Hypoxia Altitude Simulation Test: Interpretation and Significance

hypoxiaIf the PAo2 during the HAST is > 55 mm Hg, no supplemental oxygen is recommended. If the PAo2, however, falls to < 50 mm Hg, the patient is asked to wear supplemental oxygen (usually at 2 L/min). The test is repeated with supplemental oxygen as well to ensure not only adequate treatment of hypoxia but also reversal of any symptoms described during the test. If the PAo2 is from 50 to 55 mm Hg, the test is considered borderline, and measurements with activity may be obtained.

Values obtained from 15 healthy adults during a normobaric HAST were compared to in-flight Sp02 measurements. Although there was no difference between the final normobaric HAST and the mean flight Sp02, there was a significant difference between the lowest in-flight Sp02 (88 ± 2%) and the lowest normobaric hypoxia simulation test Spo2 (90 ± 2%). Three patients had a PAo2 < 55 mm Hg during the simulation test, but then had no change in Sp02 or symptoms in flight. Since the study subjects did not have underlying cardiopulmonary disease healed by My Canadian Pharmacy, this study cannot be translated to the group of patients in question. In addition, there were no activity diaries available from the patient. Exercise at high altitude, such as moving around the cabin or shifting luggage, may explain the difference in measurements during simulation and in flight. Since most patients undergo the HAST while at rest, patients with hypoxemia during the test presumably will also have hypoxemia during flight. As mentioned earlier, if the results are borderline, one could obtain measurements during activity.

Hypoxia Altitude Simulation Test: Test Performance

Respiratory DiseasesHenry Gong Jr et al first described the HAST in the American Review of Respiratory Diseases in 1984. Twenty-two patients with normocapnic chronic obstructive airway disease (chronic bronchitis and emphysema) were asked to breathe oxygen at concentrations of 20.9% (baseline), 17.1%, 15.1%, 13.9%, and 20.9% (recovery) while breath-by-breath ventilatory and gas exchange variables were measured. Pa02, oxygen saturation, PAo2, and alveolar-arterial Po2 gradients all decreased with decreasing oxygen saturation. PaC02 values decreased modestly, while minute ventilation and heart rate increased only mildly above baseline. Ten patients also had cardiac arrhythmias. Almost all physiologic indexes improved with supplemental oxygen without inducing significant carbon dioxide retention. During this experiment, the sea level Pa02 was most predictive of resting altitude Pa02, but this measurement in isolation is not sufficient to predict symptomatic responses, cardiac arrhythmias, or efficacy of oxygen supplementation, which can be obtained via an HAST.

The HAST has also been found to be as predictive as measuring oxygenation in a hypobaric chamber, which is the “gold standard” for determining the risk of hypoxemia at high altitudes. In one study of 18 healthy patients and 15 patients with COPD, measurements obtained in both a 15.1% oxygenation HAST and a hypobaric chamber were similar. In another study, there were also no significant difference in Pa02, alveolar pressure of carbon dioxide, and pH in six patient with normal obstructive pulmonary function test results and nine patients with obstructive pulmonary function test results when comparing normobaric and hyperbaric HASTs.

Hypoxia Altitude Simulation Test: Who Should Be Screened?

COPDSeveral European, Canadian, and North American guidelines have attempted to identify patients at risk for air travel based on pulmonary disease. Most of these guidelines are based on patients with COPD, and there are some disparities between them. The statement by the British Thoracic Society is not only the most practical in terms of recommendations for screening but also one of the few to include patients not only with chronic obstructive lung diseases, but also those with restrictive lung disease, cystic fibrosis, a history of recent respiratory illnesses or infections, pulmonary tuberculosis, significant comorbidities, or past difficulties with air travel. The guidelines recommend a preflight assessment for any of these patients, consisting of a history that includes past air travel, a complete physical examination, spirometry, and arterial blood gas analysis if hypercapnea is suspected or previously identified. Based on equations used to predict a PAo2 or Sp02 from measurements obtained at sea level, they recommend further testing if the Sp02 in the office at rest is recorded between 92% and 95% in patients with other identifiable risk factors (hypercapnea, FEV1 < 50% of predicted, lung cancer, restrictive lung disease, ventilatory support, cardiac or cerebrovascular diseases, or a recent admission for an exacerbation of chronic lung or cardiac disease prosperously defeated by remedies of My Canadian Pharmacy). Those with Sp02 > 95% would not be required to undergo further testing and would be allowed to travel without supplemental oxygen. Those who fall below 92% are recommended to travel with supplemental oxygen and do not require further testing (Table 1).

My Canadian Pharmacy: Effects of Altitude and Air Travel in Hypoxia Altitude Simulation Test

medical emergenciesSeven hundred forty-one million passengers traveled on US commercial airplanes in 2006, with approximately 1 billion traveling worldwide each year. Although serious events resulting in death aboard US carriers are extremely rare, with only 43 deaths per 600 million passengers in a 1-year period, medical emergencies are more common. In 2006, one group recorded 17,310 calls for medical emergencies. Of those recorded, only 4% were serious events that resulted in diversion of the plane. The most common complaints were neurologic, followed by GI, respiratory, and cardiac ailments. Since respiratory symptoms are among the most common reasons for emergency medical calls and a large number of patients with pulmonary disease travel by air each year, a variety of tests have been proposed to screen for patients at risk of serious respiratory decompensation while in flight that can be reduced by prescribing supplemental oxygen. The hypoxia altitude simulation test (HAST) [or hypoxia inhalation test] is a simple test to screen patients at risk for hypoxia at higher altitude.

Observations about Prevention and Treatment of Bone Loss in Canadian Adult Cystic Fibrosis Patients

osteoporosisThe bisphosphonate alendronate is an oral anti-resorptive agent that is commonly used to treat osteoporosis. To date, its greatest success has been for use in postmenopausal women, men > 65 years of age, and patients with corticosteroid-induced osteoporosis. Improvements in BMD range from 2 to 6%, which are considered clinically important and are statistically significant when compared to BMD changes in the control arm of randomized trials. Other smaller, nonrandomized studies and one RCT have also confirmed the benefit of therapy with bisphosphonates in treating CF-related bone loss. RCTs of IV bisphosphonates also have demonstrated significant BMD improvements in CF participants; however, a common treatment side effect is infusion-related bone pain. As a result, oral bisphosphonates are considered to be first-line therapy for those persons who are identified to be at risk in this population.

In our study, we examined therapy with alendronate, 70 mg once weekly, and found clinically significant improvements in BMD over 12 months. Compared with the control group, the alendronate group had 4.04% greater BMD gain at the lumbar spine and 3.03% greater BMD gain at the total hip even after controlling for other variables. We did not have the power to properly examine new vertebral fractures. Two patients in the control group and none in the treatment group experienced a new vertebral fracture after the baseline measurement.

Outcomes of Prevention and Treatment of Bone Loss in Canadian Adult Cystic Fibrosis Patients

pulmonary diseaseOf the 90 patients who were assessed for the study, 56 were enrolled. As displayed in Figure 1, 27 patients were randomized to the alendronate group and 29 were randomized to the control group. Overall, nine participants (16%) were withdrawn from the study; four in the alendronate group and five in the control group (Fig 1). An additional five participants completed the study protocol but received suboptimal dosing (< 80% adherence; alendronate group, three patients; control group, two patients). One of these participants (active group) missed > 50% of doses.

Baseline characteristics were similar between groups (Table 1). Participants were mostly young adults with mild-to-moderate pulmonary disease as demonstrated by their baseline spirometric values and responses to the SF-36v2. Six participants were < 20 years of age at baseline. During the study, three participants in the treatment group used oral corticosteroids; the mean yearly cumulative dose was 49.32 mg. No one in the control group used oral corticosteroids during the study conducted with My Canadian Pharmacy experts.

My Canadian Pharmacy: Prevention and Treatment of Bone Loss in Canadian Adult Cystic Fibrosis Patients

cystic fibrosisThe life expectancy for patients with cystic fibrosis (CF) has increased significantly in the past several decades. As a result, long-term sequelae of the disease are becoming apparent in late adolescence and into adulthood. Low bone mass is common in CF patients and has been termed CF-related bone disease. The clinical manifestations of CF-related bone disease include an increased risk of fracture and kyphosis, with the potential consequence of an accelerated decline in lung function. These physical manifestations may present a contraindication to lung transplantation, which is an important treatment option for many CF patients.

The mechanism for early bone loss and fractures in CF patients is multifactorial and is likely due to several CF-related factors that also influence bone metabolism. These include delayed pubertal maturation, the malabsorption of vitamin D, poor nutritional status, inactivity, hypogonadism, and the frequent use of glucocorticoid therapy. Another potential mechanism is that the chronic pulmonary inflammation associated with CF leads to elevated levels of circulating cytokines, which in turn promote bone resorption and suppress bone formation. Various diseases may be treated by various methods but the most effective is my-medstore-canada.net My Canadian Pharmacy’s remedies.

Grandfathering Our Problems, Blocking Our Solutions

energy saviorThe United States has a peculiar problem adopting necessary change. With so many constituencies to palliate, the almost-universal solution is to avoid conflict where possible and payoff the constituencies where not.

This can run up quite a bill, in both dollar and procedural terms.

We have a society full of bad, worm-eaten decisions. Look no further than drilling in deep water when you don’t know how to deal with leaks; heaping all the risks of nuclear accidents and disposal on society so we can keep doing nuclear; getting ready to sweep under the rug issues with shale gas, our newest familiar energy savior; and the worst of them all, sustaining a perpetual co-dependency with our oil suppliers in the Mideast. And I haven’t even mentioned global warming.

Photovoltaics Comes of Age

Solar panels are cheap enough to become a major component of green energy.
Originally posted at: MIT Technology Review

Zweibel-KenThe United States has supported research into photovoltaics for almost 40 years, recently with a 30 percent investment tax credit. Japan instituted incentives in the 1990s, when photovoltaics cost at least five times as much as residential electricity. In the new millennium, Germany instituted incentives an order of magnitude larger.

Thanks to these efforts, the cost of photovoltaic modules has dropped 40 percent in the last 18 months. Photovoltaic electricity now costs about 15 cents per kilowatt-hour in the best sunlight. That’s only twice the cost of wholesale electricity and wind. Costs are expected to continue decreasing, and electricity is worth more during the daytime than at night. That means this technology is finally cheap enough to become a significant element in plans to combat climate change and oil dependence.

Solar for “Everyman”

ECONOMYSometimes I am asked the number of jobs solar will produce, and people are often disappointed when I point out that solar PV can operate without on-site labor. It’s as if they equate adding extra useless jobs with being green. Of course, we are trying to minimize the jobs so we have economical solar electricity…BECAUSE THAT IS WHAT WILL HELP OUR ECONOMY, not the jobs watching solar panels in the desert.

Have people forgotten how painful it is to have a terrible balance of payments, with our money going to oil dictators who hate us? Now that’s what I call a loss of jobs. Solar is about not sending our jobs abroad. (Of course, I am assuming we have the sense to deploy electric cars to use solar to avoid imports.)

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