Aging: Pulmonary physiology

Advanced, Physiology - Respiratory

Age-Related Changes

  • 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.

Anesthesia Implications

  • 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.

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