The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies greatly

88. Lung compliance…
• Lung compliance=200 mL/cm of H2O
• Thoracic compliance= 200 mL/cm of H2O
• Total compliance=…….

89. Static vs dynamic compliance
• Depending on how it is recorded….

106. Rahn diagram…
• Distending pressures required to maintain the
lung-thorax combine at any volume is the
algebraic sum of distending pressures required
to maintain the lung and thorax separately at
the same volume
• Point C0 in graph:
• At lung volume 2 L….
• Distending pressure=
• This volume is called………

107. Rahn diagram……
• Point T0 in graph: The resting volume of
thorax if unattached to the lungs = 4 L
• Point L0 in graph: Resting volume of lung
• So, Lung is continuously trying to collapse and
thorax is continuously trying to expand

108. Rahn diagram…
• When a negative suction pressure is applied to
suck air out of lings and thorax….
• Very high negative pressure decreases the
thoracic volume to a minimum of 1 L
• At very high distending pressures….

141. Significance of FRC
• Prevents excessive fluctuation of alveolar PO2
and PCO2
• Dilutes the effect of toxic gases that might
have been inhaled in small amounts
• Prevents total collapse of the lungs at each
expiration
• Collapsed lung would have increased the
pulmonary vascular resistance

142. Measurement of FRC
• Helium dilution method
• Nitrogen wash out technique
• Plethysmography