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Considerations in Evaluating Pulmonary Disease Among the Elderly

Posted on 08 October 2012.

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Aging Respiratory SystemThomas A. Kruzel, ND

The process of aging has essentially 4 characteristics: it is universal, intrinsic, progressive, and decremental. Few of thestructural changes observed with aging are specifically characteristic of it because they are the result of accumulations

and alterations that occur throughout life.1,2 Therefore, the question arises how much of the loss of respiratory functionis due to wear and tear and how much is due to the normal aging process? Neither process is well demarcated, andthey are often indistinguishable from one another. However, it is generally recognized that the accumulated effects ofdisease have a greater influence on the respiratory system than do age-related changes.

The respiratory system is not an isolated entity but interacts with other organs of elimination to remove toxic elementsfrom the body and to maintain homeostasis. In particular, the lungs interact closely with the kidneys to maintain the bloodpH within the narrow range of 7.34 to 7.45 needed to sustain life. Therefore, a change in one of these organ systems willaffect the other as the emunctories work to maintain homeostasis.

Beginning at about age 50 years, a decline in muscle mass and the effects of repeated immune responses toenvironmental perturbations begin to influence respiratory function, provided there is not a preexisting genetic deficit orprevious lung disease. Age-related changes affect not only ventilation and gas exchange but also the ability of the lungsto defend against toxins and invaders. Changes in lung elasticity, chest configuration, and motion gradually influencecompliance and respiratory function as measured on lung function investigations. Variables such as focused expiratory

volume, forced expiratory flow, functional residual capacity, and residual volume begin to show changes.2,3 Thesealterations progress at about a 5% to 20% decline per decade in persons who do not exercise, while decrementalchanges occur at a slower rate in those who exercise. In addition, the heightened rigidity of thoracic walls and adiminished expiratory force will decrease the usefulness of cough and increase the risk for respiratory infection.

As already mentioned, it is unclear whether the increasing rate of decline in ventilatory function is a result of the normalaging process or is from the effects of prior diseases, exposure to pollutants and toxins, or an abrupt and severe insult to

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the respiratory system. All of these lead to increasing symptoms of airway obstruction. The gradual decline in lungfunction that occurs from its peak at age 20 to 25 years until age 40 years is mainly due to changes in body weight and

muscle strength. After this period, the rates of changes in forced vital capacity and focused expiratory volume tend to

follow a somewhat linear decline but vary among individuals.2,3 Because of this variation, the rate of decline cannot be

predicted based on age alone. The effects of smoking on lung function decline are well documented and will not bediscussed herein.

As we age, chest anterior to posterior diameter increases, and kyphosis of the spine occurs, which leads to a decreasedcompliance of the thorax and expiratory force. Because chest wall compliance gradually becomes stiffer, the increasedouter chest wall rigidity makes it more difficult for the diaphragm and muscles involved with respiration to counter theeffects. Therefore, this results in a slight increase in total lung capacity, as well as larger increases in functional residual

capacity and residual volume, or what remains in the lungs at rest.4 In an elderly patient, the consequence is adecreased flow of inspired and expired air, making it more difficult to assess airflow on auscultation.

The Aging Respiratory System and Emphysema Have Much in Common

In the aging respiratory system, some decrease in the number of alveoli occurs, with hypertrophy of others. This isespecially seen in smokers or in those with a history of smoking or exposure to polluted air. Because of age-related lossof elasticity, early collapse of peripheral airways occurs, leading to decreased lung volumes and less perfusion. Aginglungs and emphysema have much in common: both are characterized by less than maximum breathing capacity andforced expiratory volume, while residual volume and functional residual capacity are increased, with the lungs becomingmore rigid and distended. This change in compliance is regional rather than being evenly distributed across the lungs.The effect is to slow passive exhalation in some lung areas, while others empty normally. During quiet breathing,inspired gases will preferentially go to the more distensible upper lung areas, leading to an uneven distribution of gas

exchange. Therefore, certain areas on auscultation may sound as if there is condensation, while other areas do not.1-4

Blood volume does not change with age, but the quantity of blood present in the pulmonary circulation at any giveninstant decreases as we age. No change occurs in arterial partial pressure of carbon dioxide, but a 10% to 15%decrease in partial pressure of oxygen occurs, while the percentage saturation decreases about 5%. This, along with anuneven distribution of airflow, may account for the increase in partial pressure of carbon dioxide and the decrease inpartial pressure of oxygen. In the elderly, maximum oxygen used under stress can decrease to 50%. This is probably

due to a perfusion failure and impaired oxygen use in the tissues.1,3

There is also a change with age in the epithelial lining fluid, which is abundant in antioxidant defenses that minimizeoxidative injury to the respiratory epithelium following toxic exposure. Epithelial lining fluid is high in superoxidedismutase, catalase, metal-binding proteins, glutathione, and vitamins C and E. These antioxidant levels are reduced onexposure to ozone, nitrous oxide, and particulate matter regardless of age, but the ability to recharge the epithelial liningfluid changes, with production decreasing as we age. This increases the susceptibility of older individuals toenvironmental toxic exposure and risk for infection. Some evidence indicates an increased ability of alveolar

macrophages to release superoxide anion in response to stimuli in the elderly.4 These changes likely represent thecombined effect of repetitive stimuli from environmental exposure but could also be an adaptation to loss of function inan aging lung.

Notably, intravenous administration of small amounts of ozone and hydrogen peroxide seems clinically to provide somerelief in patients with chronic obstructive pulmonary disease or emphysema. This is possibly due to a stimulation of thevital force similar to that experienced with homeopathic medicines, but other unexplained mechanisms may have a role.

Despite these changes, the respiratory system is capable of maintaining adequate oxygenation and ventilation duringthe entire life span, provided the perturbation or insult does not force the system outside of its set point margins.Because the respiratory system reserve becomes limited with age, diminished ventilatory response to hypoxia andhypercapnia renders it more vulnerable to respiratory failure during high-demand states such as with pneumonia orheart or renal failure, leading to increased risk for morbidity and poor outcomes. While this mechanism has not beenfully elucidated, it is thought to be due to diminished sensitivity of peripheral chemoreceptors or decreased integration ofcentral nervous system pathways.

Dementia May Be an Indicator of Compromised Respiratory Function

Elderly patients who are seen with an acute-onset dementia or a sudden change in their normal activities of daily living

should undergo a workup for various possible etiologies, including acute pulmonary disease.1 While a change in aperson’s respiratory rate is a homeostatic response to hypoxia or hypercapnia and is a useful clinical sign, these

responses are muted or often absent in older patients, meaning that acute pulmonary disease may be missed. Inaddition, the effects of prescription medication use may influence a patient’s respiratory function and should be part ofthe differential diagnosis.

Because of a narrowing of the set point margins that accompanies aging and the increased difficulty of the aging personto adapt to changes in the environment, it becomes all the more important for the physician to be aware of thesevariations from the norm and to be more proactive when treating older patients. Naturopathic medicine has longsubscribed to the importance of antioxidants and metabolic and immune system enhancement to accomplish this goal.However, while these factors are important, recent work suggests that what may be key is how much fluctuation andvariation from the set point margins, as well as the organism’s ability to return to homeostasis, will affect its longevity the

most.5 Regardless of the disease process, addressing the determinants of health and the hierarchy of diseaseprogression will help elderly patients in their later years, along with an appreciation of the aging process.

Thomas A. Kruzel, ND is a naturopathic physician who is in private practice at the

Rockwood Natural Medicine Clinic in Scottsdale, Arizona. He received a BA in biology from the California State Universityat Northridge and his doctorate of naturopathic medicine degree from the National College of Naturopathic Medicine,Portland, Oregon. Dr Kruzel is also a board-certified medical technologist. As an associate professor of medicine atNational College of Naturopathic Medicine, he has taught clinical laboratory medicine, geriatric medicine, and clinicalurology. He is the author of The Homeopathic Emergency Guide and Natural Medicine Pediatric Home Health Advisor.Dr Kruzel is past president of the American Association of Naturopathic Physicians and was selected as Physician of theYear by that organization in 2000 and by the Arizona Naturopathic Medical Association in 2003.

References

Abrams WB, Berkow R, Fletcher A, eds. The Merck Manual of Geriatrics. Rahway, NJ: Merck Sharp & Dohme ResearchLaboratories; 1990.

Hazzard WR, Blass JP, Ettinger WH, Halter JB, Ouslander JG, eds. Principles of Geriatric Medicine and Gerontology. 4thed. New York, NY: McGraw Hill; 1999.

Ross BK. Aging and the respiratory system. In: Syllabus on Geriatric Anesthesiology. Seattle: University of Washington;2012.

Sharma G, Goodwin J. Effect of aging on respiratory system physiology and immunology. Clin Interv Aging.2006;1(3):253-260.

Olshansky SJ, Rattan SI. What determines longevity: metabolic rate or stability? Discov Med. 2005;5(28):359-362.

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