Aging: Pulmonary physiology
Advanced, Physiology - Respiratory
- Elasticity is decreased in lung tissues causing
- Over distention of alveoli- Decreases alveolar surface area and decreases gas exchange efficiency.
- Collapse of smaller airways resulting in increased residual volume and closing capacity.
- Increase anatomical dead space
- Increased physiological dead space
- Increased chest wall rigidity
- Decreased cough response
- Decreased maximal breathing capacity
- Blunted response to hypercapnia/ hypoxia
- Decreased arterial oxygen tension by 0.35 mm Hg per year- As closing capacity increases small airways start closing at normal tidal breathing causing ventilation perfusion mismatch and decreases PaO2.
- Difficult mask ventilation secondary to poor seal(edentulous)
- Difficult intubation secondary to arthritis of TM joint/Cervical spine
- Improved visualization of vocal cords during intubation secondary to missing upper teeth.
- Aspiration pneumonia common- decreased airway protective reflexes and inadequ clearing of secretions.
- Consider pain control through epidurals/local anesthesia/intercostals blocks etc.
- MAC decreased by 4% per decade over 40 yrs., e.g., Halothane MAC- 0.77, age of 80 MAC would be 0.77 – [0.77 * 4% * 4]
- Decreased cardiac output – onset of action is faster.
- Myocardial depressant effects of anesthetic gases is exaggerated in the elderly
- Recovery from anesthesia is prolonged
- Increased volume of distribution
- Decreased hepatic function ( significant with halothane use
- Decreased pulmonary gas exchange
- Tachycardia tendencies of desflurane and isoflurane decreased in the elderly.