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## Pressure Versus Time Scalar The pressure scalar provides a good information about airway compliance to the clinician. It represents the pressure in the airway as a function of time. This can be a fixed or variable amount depending on the mode of ventilation. During pressure control ventilation,...

## Pressure Versus Time Scalar The pressure scalar provides a good information about airway compliance to the clinician. It represents the pressure in the airway as a function of time. This can be a fixed or variable amount depending on the mode of ventilation. During pressure control ventilation, the pressure delivered is constant and the pressure scalar is square-shaped. In volume control ventilation, the pressure scalar is ascending due to the rise in pressure with a constant flow pattern [6, 7, 9] In the typical graphic displayed on the ventilator, the baseline pressure indicates the PEEP and the maximum pressure at the end of the curve indicates the PIP (Fig. 3a). In addition to the PIP and the PEEP, the pressure versus time scalar can show a few other pressure measurements when specific ventilator maneuvers are done. The first is the plateau pressure (Pplat) (Fig. 3b). This is the pressure in the airway under static conditions, or when there is no air flow. PIP is mathematically calculated by adding the pressure created by airway resistance, the pressure related to the lung's compliance, and the total PEEP. When there is no flow in the system, the pressure due to airway resistance drops to zero, and the resultant value is the Pplat. This value is thought to represent the pressures