Pulmonary Changes with Aging
Last updated: 02/08/2023
- The most important pulmonary physiologic changes associated with aging are decreased pulmonary elasticity, decreased chest wall compliance, and decreased respiratory muscle strength. All these changes predispose elderly patients to airway collapse, V/Q mismatch, and respiratory failure.
- Due to changes in airway physiology, aging patients will show an ↑RV, ↑FRC, ↑anatomic and physiologic dead space, and ↑closing capacity. However, if no lung pathology is present, gas exchange is unaffected by normal aging.
- Aging lungs develop decreased elastic recoil and increased compliance due to changes in the lung parenchyma. Loss of elastic recoil causes1:
- Small airway collapse: elasticity and natural recoil are needed to hold small airways open during changes in lung volumes during respiration. Airflow becomes limited during expiration due to the collapse of intrathoracic airways. Small airway collapse also is one of the causes of ↑ residual volume (RV).
- Decreased alveolar surface area: loss of alveolar walls results in small alveoli coalescing to form larger sacs.
- Closing capacity (CC) increases with age until it surpasses functional residual capacity (FRC), meaning that airway obstruction may occur during normal tidal breathing.2
- CC is the lung volume at which small airway closure begins
- CC = FRC in the supine position at ~44 years old.
- CC = FRC in the upright position at ~66 years old
- Mnemonic for factors that increase closing capacity – ACLS-S. Age, Chronic bronchitis, LV failure, Smoking, Surgery
- The overall effect of these changes in elasticity is increased ventilation-perfusion (V/Q) mismatching.2
- Consequently, PaO2 decreases with age.
Estimated PaO2 values for healthy adults is calculated with: PaO2 = 110-(Age*0.4)
- Memory aid: The pulmonary changes associated with aging are often described as “senile emphysema” due to its similarity with the pathologic condition.
Chest Wall Rigidity & Muscle Weakness
- Calcification and kyphosis of the thoracic spine, osteoporosis, arthritis of the costovertebral joints, and structural changes to the intercostal muscles all contribute to increased chest wall rigidity.1
- Loss of elastic recoil causes an enlargement (barrel shape) of the thorax, which pulls the diaphragm flatter. This change causes the diaphragm to be less efficient, requiring increased work of breathing and results in a decreased transdiaphragmatic pressure gradient.3
- Loss of muscle strength, particularly in accessory respiratory muscles, results in decreased maximal breathing capacity in response to stress and decreased cough, which may lead to diaphragm fatigue during higher ventilatory demand.3
- Total lung capacity (TLC) correlates with height, which decreases with age. However, the changes in other lung volumes that make up TLC balance so that there is no net change in TLC.2
- Residual volume (RV): decreased alveolar surface area and small airway collapse due to loss of elastic recoil results in increased RV.1,2
- Vital capacity (VC): the increase in RV causes a compensatory decrease in VC.1
- FRC: determined by the balance between the inward elastic recoil of the lungs and the outward recoil of the chest wall. Increases by 1-3% per decade due to a more rapid decrease in lung recoil than increase in chest wall rigidity.1
- Reves JG, Barnett SR, McSwain JR, Rooke GA. The Aging Respiratory System: Strategies to Minimize Postoperative Complications. In: Geriatric Anesthesiology. 3rd ed. Springer International Publishing; 2018:179-192.
- Barnett SR. Pulmonary Issues in the Elderly Patient. In: Manual of Geriatric Anesthesia. New York. Springer; 2013:217-20.
- Butterworth JF. Age-Related Anatomic & Physiologic Changes. In: Morgan and Mikhail's Clinical Anesthesiology. 6th ed. McGraw-Hill Education; 2018.
- Society for Advancement of Geriatric Anesthesia. Syllabus on Geriatric Anesthesiology. Published January 10, 2002. Accessed February, 2023.y 8 Link
- ASA Committee on Geriatric Anesthesia. Frequently Asked Questions About Anesthetic Considerations for Elderly Patients. Society for Advancement of Geriatric Anesthesia. Published 2009. Accessed February 8, 2023. Link
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