The Science Journal of the American Association for Respiratory Care

1996 OPEN FORUM Abstracts

Sleep, Nutrition and Air Travel

Brian L. Tiep, MD Sunday, November 3, 1996

Sleep

COPD patients suffer from a higher than usual prevalence of insomnia, daytime sleepiness and nightmares. They have the usual causes of poor sleep efficiency complicated by dyspnea, orthopnea, anxiety and depression. Commonly prescribed medications have been implicated but theophylline, beta agonists and steroids have failed to demonstrate consistent alteration in sleep architecture. In fact, these medications may relieve symptomatic causes of sleep deprivation. There is a relationship between sleep architecture, nocturnal saturation and ventilatory muscle function. Some patients have overlap syndrome of coincidental sleep apnea. These patients are more likely to have respiratory failure with hypoxemia, hypercarbia and pulmonary hypertension. Patients unable to sleep due to dyspnea at night may seek relief from sedatives or alcohol. This is thought to be a dangerous situation as it runs the risk of respiratory depression and hypercarbia and respiratory acidosis. Nocturnal oxygen desaturation (NOD) is very common in patients with daytime hypoxemia. Resting and exercise SaO_{2}s do not accurately predict NOD. Some patients with normal daytime saturations may have NOD due to reduced ventilation during sleep (particularly REM), widening ventilation/perfusion mismatching, blunted chemosensitivity, and dysfunctional lung mechanics. Since NOD is frequently associated with pulmonary hypertension, cor pulmonale may be an indicator that the patient desaturates at night. In this case nocturnal oxygen therapy is recommended. Nocturnal oxygen therapy tends to reduce daytime pulmonary artery pressures and ventricular ectopy at night but it is unknown whether nocturnal oxygen improves survival.

Nutrition

Adequate nutrition is a problem for many COPD patients. Oxygen and substrates are critical components in energy utilization. About 25% of COPD patients are unable to maintain their nutritional status as evidenced by weight loss; this increases to 50% in hospitalized COPD patients. Poor nutritional status is more common with greater mechanical and gas exchange impairment and adds to the systemic problems including loss of immune competence. Muscle strength testing including PiMax lend supporting evidence of malnutrition. In performing a nutritional assessment, weight loss > 10% of ideal body weight suggests malnutrition. Hepatic markers including albumin, transferrin, and retinal binding protein are indicators but they are not unique. Anthropromorphic measurement to determine fat, muscle and skeletal mass also suffer from problems of interpretation. Nutritional support can be given orally and improves ventilatory muscle strength but it is not easily maintained by the patient. Optimal caloric support has not been determined. The respiratory quotient (RQ) is affected by the relative contributions of the substrates fat, carbohydrate and protein. The net result of metabolism is production of CO_{2}. The CO_{2} is excreted by increasing ventilation. Some food supplements are based on fats over carbohydrates to reduce ventilatory workload. When eating becomes difficult due to dyspnea, one remedy for the patient to eat several meals throughout the day. Food supplements have been tried with varying degrees of success. Forced nutrition and special diets are not recommended. Being overweight presents its own problems by placing an extra workload on the chest as well as the cardiorespiratory system.

Air Travel

Pulmonary rehabilitation programs have encouraged patients to travel by air. Air travel is generally safe but the cabin environment and preparations for air travel presents some challenges for COPD patients. Patients must meet schedules, endure long concourse walks, sit in confining seats, breathe dry and oxygen poor air. Commercial aircraft cabins are pressured to 5 to 8000 ft equivalent altitude and may rise to 10,000 feet for short periods. Oxygen patients require oxygen both in the air and on the ground. Some patients adequately oxygenated at sea level require oxygen during the flight. There are a number of tests and charts to help determine the patient's oxygen requirement. Some stable patients can tolerate PO_{2}'s below 50 mmHg for brief periods without serious consequences. Advanced planning is the key to successful travel. All travel must be planned ahead of time, reservations and oxygen must be made at least one week in advance. Arrangements should also be made for any other needs in advance. Patients must arrive well ahead of the flight time.

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