TOTAL PULMONARY VENTILATION Total pulmonary ventilation or Minute

TOTAL PULMONARY VENTILATION Total pulmonary ventilation or Minute respiratory volume = Ventilation rate x Total volume =12 breaths/ mt x 500 ml/ breath =6000 ml / mt

Dead Spaces Anatomic dead Space + Alveolar dead space Physiological dead space

Rate of Alveolar Ventilation =Ventilation rate x ( Tidal volume – dead space volume) = 12 x 500 – 150 = 12 x 350 = 4200 ml / mt

Effects of Breathing Pattern on Alveolar Ventilation Respiratory Rate Tidal Volume (ml) (Breaths / min ) Total Pulmonary Ventilation ( m. L / min) Fresh Air to Alveoli (tidal volume – dead space volume* Alveolar Ventilation ( m. L / min) 500 (Normal) 12 (Normal) 6000 350 4200 300(Shallow) 20 ( rapid) 6000 150 3000 750 (Deep) 8( Slow) 6000 600 4800

Types and Patterns of Ventilation Eupnea Normal quiet breathing Hyperpnea Increased respiratory rate and / or volume in response to increased metabolism Exercise Hyperventilation increased respiratory rate and / or volume without increased metabolism Emotional hyperventilation; blowing up a balloon Hypoventilation Decreased alveolar ventilation Shallow breathing / asthma/ restrictive lung disease Tachypnea Rapid breathing; usually increased respiratory rate with decreased depth Panting Dyspnea Difficulty in breathing (a subjective feeling sometimes described as “ air hunger”) Various pathologies or hard exercise Apnea Cessation of breathing Voluntary breath-holding; depression of CNS control centers

Ventilation-perfusion ratio

Respiratory Unit

Respiratory membrane

Physics of Diffusion

Concept of Partial Pressure

Gas Exchange at alveoli & Cell

Partial pressure of O 2 (Po 2) at various sites. Site Po 2 (mm Hg) Atmospheric air (dry) 159 Inspired air ( partially wet) 158 Air entering lungs 149. 3 Alveolar air 100 Arterialized blood in pulmonary veins entering left atrium Arterial blood ( in aorta, arteries, arterioles ) Tissue cells 97 40 or less Mixed venous blood 40 95

Partial pressure of CO 2 (PCo 2) at various sites. Site PCo 2 (mm Hg) Tissue cells 50 – 70 Venous Blood 46 Alveolar Air 40 Arterial Blood 40 Expired air 32