Mean Airway Pressure (Paw) Calculator

Determines the mean airway pressure applied during positive-pressure mechanical ventilation.

Refer to the text below the tool for more information about Paw and the parameters from its formula.


Mean Airway Pressure (Paw) defines the mean pressure applied during positive-pressure mechanical ventilation and correlates with alveolar ventilation, arterial oxygenation and hemodynamic performance.


Mean airway pressure (Paw) is determined by PIP, the fraction of time devoted to the inspiratory phase (Ti/Ttot, where Ttot is total respiratory cycle time), and PEEP:

Paw = ((Inspiratory Time x Frequency) / 60) x (PIP – PEEP) + PEEP


Inspiratory Time (Ti)
Respiratory frequency (f)
Peak Inspiratory Pressure (PIP)
Positive End-Expiratory Pressure (PEEP)
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Mean Airway Pressure Explained

Mean Airway Pressure (Paw) defines the mean pressure applied during positive-pressure mechanical ventilation and correlates with alveolar ventilation, arterial oxygenation and hemodynamic performance.

Paw is determined by PIP, the fraction of time devoted to the inspiratory phase (Ti/Ttot, where Ttot is total respiratory cycle time), and PEEP.

Paw = ((Inspiratory Time x Frequency) / 60) x (PIP – PEEP) + PEEP

Peak inspiratory pressure (PIP) is the pressure applied to the lungs during inhalation and increases with any airway resistance (due to increased secretions, bronchospasm or decreased lung compliance. PIP values should not increase to more than 40 cmH2O (such as in acute respiratory distress syndrome) but normal increases can help increase tidal volume and CO2 elimination and decrease PaCO2, hence improve oxygenation.

Positive end-expiratory pressure (PEEP) is the pressure in the lungs (alveolar pressure) that exists at the end of expiration and can be of two types: extrinsic (applied by a ventilator) or intrinsic (caused by an incomplete exhalation).

 

References

Prince R, Ballantine TVN. Formula for calculating mean airway pressure. The Journal of Paediatrics. 1983; 102 (1): 164.

Stewart AR, Finer NN, Peters KL. Effects of alterations of inspiratory and expiratory pressures and inspiratory/expiratory ratios on mean airway pressure, blood gases, and intracranial pressure. Pediatrics. 1981; 67 (4): 474–81.

Marini JJ, Ravenscraft SA. Mean airway pressure: physiologic determinants and clinical importance--Part 2: Clinical implications. Crit Care Med. 1992; 20 (11): 1604–16.


Specialty: Pulmonology

System: Respiratory

Abbreviation: Paw

Article By: Denise Nedea

Published On: June 8, 2020

Last Checked: June 8, 2020

Next Review: June 8, 2025