Respiratory contribution to exercise intolerance in COPD

Respiratory contribution to exercise intolerance in COPD
03/03/2018 Comments Off on Respiratory contribution to exercise intolerance in COPD Academic Papers on Health and Medicine,Sample Academic Papers admin

Respiratory function is of course altered in COPD as detailed previously, and this has repercussions on ventilatory as well as gas exchange adaptations to acute dynamic exercise. These alterations account for a significant portion of the exercise intolerance but do not completely explain the limitation in patients with COPD. This section will review the pattern of respiratory response and the repercussions of gas exchange during exercise in COPD.

The Treatment: Long-Term Oxygen Therapy (LTOT)

Besides smoking cessation, long-term oxygen therapy (LTOT) is the only treatment that improves the life expectancy for patients with oxygen desaturation due to cardiopulmonary disease. Two prospective controlled, randomized studies have shown that LTOT improves survival in hypoxemic patients: The British Medical Research Council (MRC) trial (Report of the Medical Research Council Working Party, 1981) and the North American Nocturnal Oxygen Therapy Trial (NOTT).

The MRC study clearly indicated a significant improvement in the survival rate of 66 male hypoxemic patients receiving LTOT > 15 hours per day, including sleep, when compared to similar patients not receiving LTOT. The survival difference appeared after 500 days and was statistically significant after 3,4, and 5 years. The NOTT study showed that the mortality rate for 102 patients assigned LTOT for > 18 hours per day (continuous group) was half of 101 patients assigned LTOT for 10-12 hours per day (nocturnal group). The survival difference was apparent at the onset of LTOT and was statistically significant at 1, 2, and 3 years. From the both of these seminal studies, it can be concluded that some oxygen is better than none, but nearly continuous oxygen (> 18 h/day) is better than oxygen used 12-15 h/ day.

In addition to improving survival, LTOT has also been shown to improve self-reported sleep quality, increase exercise tolerance reduce pulmonary hypertension, improve neuropsychological status, and reduce hospitalization rates. The treatment of LTOT is simple: the patient is administered supplemental oxygen at a prescribed constant flow through a nasal cannula from an oxygen source. The source of oxygen comes packaged in three types of systems: oxygen concentrator, compressed gas, and liquid oxygen. The oxygen concentrator is the most common, convenient, and inexpensive form of oxygen. The concentrator works by pressurizing and extracting oxygen from room air for unlimited delivery to the patient at a constant flow. Oxygen concentrations are typical> 90% of flows up to 3-4 L/min, and the flow rates can be set as high as 5 L/min. The typical concentrator weighs approximately 35 lbs. and must be plugged in for power; therefore, this form of oxygen system is a stationary source used in the home. The remaining two systems are typically used as portable oxygen sources, although they can be used as stationary sources as well. Compressed oxygen is provided in high-pressure portable cylinders in standard sizes of 16, 9 and 3 lbs. At a flow of 2 L/min, these cylinders can provide oxygen for 5.2 hours, 2 hours, and 1.2 hours, respectively.

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