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Intermittent Positive Pressure Breathing (IPPB) |   |
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Physiologic Principles If IPPB is to be successful, it must increase alveolar distending pressure. This is accomplished by increasing alveolar pressure so that the difference between alveolar and pleural pressure also is increased. |
IPPB reverses the normal spontaneous pressure gradients. Instead of negative alveolar pressure causing gas flow into the lungs, positive pressure at the airway opening creates the needed gradient. The rise in alveolar pressure increases PL and expands the alveoli. When alveolar distending pressures are increased, a large volume of gas exists within the airway. Gas flows from the airway into the lungs, and alveolar pressures rise during the inspiratory phase of IPPB. As a result of these pressure changes, four physiologic effects can be attributed to IPPB:
- An increase in mean airway pressure
- A decrease in the work of breathing (WOB)
- Manipulation of the inspiratory-expiratory ratio
- Increase in tidal volume (VT)
Appropriate application of IPPB may result in a stressed patient accepting and being comfortable with ventilatory patterns they could not tolerate during spontaneous breathing. When an increased WOB exists, intermittent positive pressure may allow the same degree of physiologic ventilation with far less expenditure of muscular energy.