physioex 7

• Ventilation refers to the movement of air in and out of the lungs during breathing.
• inspiration: the process of breathing in air into the lungs, causing the lungs to expand
• expiration: the process of exhaling air from the lungs, causing the volume of the lungs to decrease
• inspiration occurs when external intercostal and diaphragm contract
• quiet expiration, diaphragm rise up and chest walls move in; passive process
• forced expiration, contraction of abdominal muscles and internal intercostals push down on the diaphragm and increase pressure inside the thorax
• tidal volume: the volume of air that is inhaled or exhaled in a single breath (500ml)
• inspiratory reserve volume: the amount of air that can be forcefully inspired after the normal tidal volume (m: 3100ml, w: 1900ml)
• expiratory reserve volume: the additional volume of air that can be forcefully exhaled beyond the normal tidal volume (m: 1200ml, w: 700ml)
• residual volume: the remaining volume of gas left in the lung at the end of an exhalation (m: 1200ml, w: 1100ml)
• total lung capacity: maximum amount of air contained in lungs after maximum inspiratory effort [TLC= TV+ IRV+ ERV+RV] (m:6000ml, w:4200ml)
• vital capacity: maximum volume of air that can be exhaled after a maximal inspiratory effort [VC=TV+IRV+ERV] (m: 4800ml, w: 3100ml)
• forced vital capacity: amount of air expelled when subject takes deepest possible inspiration and forcefully exhales as completely and rapidly as possible
• forced expiratory volume: measures percentage of vital capacity expired in 1 second of FVC test (~75%-85% of vital capacity)
• airway radius affects the resistance of airflow
• emphysema: destruction of alveolar walls, decreased diffusion, decreased oxygenation

  • elastic recoil is lost and expiration is difficult, causing increased airway resistance
• acute asthma: bronchiole smooth muscle spasms and airway is constricted, thick mucus also produced; airway collapse before expiration complete

  • triggered by allergens, extreme temp changes and exercise
  • beta2 agonsit or acetylcholine antagonist relax smooth muscle
• moderate aerobic exercise, rate of breathing and tidal volume increase but tidal volume increase is greater
• surface tension: at gas liquid boundary, liquid more attracted to each other in comparison to gas
• surface tension resists any force that increases surface area of gas-liquid boundary, decreases size of hollow space (alveoli, air spaces in lungs)
• surfactant: a substance that reduces surface tension and increases the rate of diffusion
• pull lungs away from thoracic wall

  1. tendency of lungs to recoil and surface tension
  2. tendency of compressed chest walls to recoil and expand out
• pneumothorax: air in pleural space, usually due to ruptured lung
• atelectasis: collapse of the lung tissue, leading to a decrease in lung volume
• increase in surfactant leads to increased respiration
• negative pleural pressure prevent lung collapse
• minute ventilation: TV x BPM [(ml/breath)x(breath/min)]
• FEV%= FEV1/FVC x 100
• contracting external intercostals will increase thoracic volume
• obstructive diseases affect airflow, restrictive diseases affect volume and capacity; forced expiratory volume tests help to determine which is which
• respiratory volumes

  A) TV

  B) IRV

  C) ERV

  D) RV

  E) VC

  F) TLC

  
• lung capacities and volumes

  A) IRV

  B) TV

  C) ERV

  D) RV

  E) inspiratory capacity

  F) functional residual capacity

  G) vital capacity

  H) RV

  I) TLC

  
• before inspiration, pleural cavity pressure is less than alveolar pressure