Table 1 ESM. Summary of the 10 main respiratory pressures.

Abbreviation / Definition / Location / Difference across structures / Timepoint for measure / Reference for the value / Calculated or measured
Pao or Paw / Pressure at the airway opening
or Airway pressure / At the mouth or at the proximal tip of an endotracheal tube / Sum of elastic and resistive pressures pertaining to lung and chest wall / At any time during inspiration and expiration / Referred to atmospheric pressure / Measured
Ppl / Pleural pressure / Surface pleural pressure / Absolute pressure within the pleural cavity / At any time during inspiration and expiration / Referred to atmospheric pressure / Cannot be measured in routine
Pes / Esophageal pressure / Inside an air-filled balloon inserted into the lumen of the mid-lower third of the oesophagus / Estimate of Ppl / At any time during inspiration and expiration / Referred to atmospheric pressure / Measured
PEEP / Positive end-expiratory pressure / At the mouth or at the proximal tip of an endotracheal tube / Pressure across the respiratory system at end-expiration / At the end of expiration, before opening of the inspiratory valve / Referred to atmospheric pressure / Measured
Pplat / Plateau pressure / At the mouth or at the proximal tip of an endotracheal tube / Pressure across the respiratory system at end-inspiration / At the end of insufflation at zero flow / Referred to atmospheric pressure / Measured
P0.1 / Airway pressure change at 0.1 sec against occluded airway / At the mouth or at the proximal tip of an endotracheal tube / Change over time ofairway pressure at constant lung volume / 100 msec after onset of inspiratory effort done against closed airways. Reflects intensity of central respiratory drive / Referred to atmospheric pressure / Measured
Palv / Alveolar pressure / From Paoand flow tracingsand knowing respiratory system resistance / Absolute pressure within the alveolar space / At any time during inspiration or expiration / Difference between Pao and the multiplication of flow and respiratory system resistance / Calculated
PL / Trans-pulmonary pressure / From PaoandPes tracings / Pressure across the lung / At any time during inspiration or expiration / Difference between Pao and Pes / Calculated
P / Driving pressure / From PaoandPes tracing / Pressure across the respiratory system or across the lung / At given time points is the difference between end-expiratory and end-inspiratory Pao and PL / Between airway and transpulmonary pressure at specific time points / Calculated
Pmus / Muscular pressure / From Pes and volume tracings and knowing chest wall compliance / Pressure across the respiratory system / At any time during inspiration or expiration / Difference between the pressure of the relaxed chest wall and the pleural pressure change at a given volume / Calculated

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