Respiratory Physiology Maintaining Alveolar pressure for Speech • Reduction in relaxation pressure occurs as air is expended – Air flow continues – Lung volume & elastic recoil decrease – Decrease in the need to counteract relaxation pressure with inspiratory muscles – Muscular checking force for relaxation varies from moment to moment Maintaining Alveolar pressure for Speech • For any given alveolar pressure needed for speech: –A different balance of active & passive muscular forces will be required to maintain pressure at each lung-volume level Relaxation Pressure Curve % VC *Recoil forces only; no muscular activity Resting Lung Volume Alveolar Pressure (cm H2O) Relaxation Relaxation Pressure Curve • Below 55% VC the elasticity of the lungs contribute little to the curve • Lungs compress the air nicely above resting lung volume • Chest works very hard below resting lung volume to pull air into system • Below 55% you begin to use expiratory muscles to maintain Ps Pressure-Volume Relationship • Right side: Expiratory Pressure: greater your lung volume the more force you can generate for exhalation • Left side: Inspiratory pressure: Less air in your lungs the greater force you can generate for inspiration Pressure-Volume Relationship Pr % VC Pi Pe Residual Air Pulmonary Pressure (mm Hg) Study Hard!!!!