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 Top curve generated by: –Subjects were told to inhale to some percentage of their VC and then to relax –Intraoral pressure was measured (estimating both alveolar & subglottal pressure) –Repeated at various %ages of VC –This was done for the top portion of the curve –Positive because the tissue is attempting to return to rest

Relaxation Pressure Curve Bottom curve generated by: –Subjects were asked to exhale down and hold their breath and relax –Relaxation point is where no pressure is generated (alveolar pressure equals atmospheric pressure) –Pressures generated are not as great & negative –negative pressures are predominately the result of recoil of the chest wall attempting to return to rest

Relaxation Pressure Curve Resting Lung Volume Relaxation % VC Alveolar Pressure (cm H 2 O) *Recoil forces only; no muscular activity

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 P s

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 % VC PiPr Pe Residual Air Pulmonary Pressure (mm Hg)

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