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 + Physiological dead space Alveolar 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 Fresh Air to Alveoli Respiratory Rate Total Pulmonary (tidal volume – dead Alveolar Ventilation Tidal Volume (ml) (Breaths / min ) Ventilation ( mL / min) space volume* ( mL / 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 Exercise in response to increased metabolism Hyperventilation increased respiratory rate and / or volume Emotional hyperventilation;blowing up a without increased metabolism balloon Hypoventilation Decreased alveolar ventilation Shallow breathing / asthma/ restrictive lung disease Tachypnea Rapid breathing; usually increased Panting respiratory rate with decreased depth Dyspnea Difficulty in breathing (a subjective Various pathologies or hard exercise feeling sometimes described as “ air hunger”) 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 O2 (Po2) at various sites. Po2 (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 97 Arterial blood ( in aorta, arteries, arterioles ) 95 Tissue cells 40 or less Mixed venous blood 40
Partial pressure of CO2 (PCo2) at various sites. PCo2 (mm Hg) Tissue cells 50 – 70 Venous Blood 46 Alveolar Air 40 Arterial Blood Expired air 32