Airway opening pressure (Pawo), or Mouth pressure(PM) is often called airway pressure (P aw ). Unless pressure is applied to mouth or nose, Paw is Zero (atmospheric).

 

Body surface pressure (P bs ) is the pressure at body surface. This is equal to Zero unless the person is using a pressurized chamber (e.g., hyperbaric chamber) or a negative pressure ventilator (e.g., iron lung).

 

Intrapleural pressure (P pl ) is the pressure in the potential space between the parietal and visceral pleurae. Normal Ppl is about -5cm H2O at the end of exhalation during spontaneous breathing and -10 cm H2O at the end of inspiration.

 

Alveolar pressure(P A or P alv ): This pressure is also called intra-pulmonary pressure or lung pressure. Alveolar pressure normally changes as the intra-pleural pressure changes. During inspiration alveolar pressure is about -1cm H2O and during exhalation it is about +1cm H2O.