Fig. 1
From: A novel method to calculate compliance and airway resistance in ventilated patients
Schematic of the numerical method used to solve the respiratory system equation of motion for static compliance (Crs) and airway resistance (Rrs). In this example, the solution matrix was developed for ΔV(tk) = 300 mL, Faw(tk) = 32 L·min−1, and PEEPa = 5 cmH2O and shown graphically as a three-dimensional surface bounded by Crs values ranging from 10 to 50 mL·cmH2O−1 and Rrs from 0 to 20 cmH2O·s·L−1. This surface encompasses all possible combinations of Paw, Crs and Rrs capable of satisfying Eq. 2 for a given set of ΔV, Faw, and PEEPa measurements made at time tk during insufflation. Paw, also measured at tk and equal in this example to 27 cmH2O, further restricts the solution of Eq. 2 to lie along path (A). This path is defined by surface values coinciding with the measured Paw, with point ‘a’ referring to the still unknown solution of Eq. 2. Projecting path A onto the Crs – Rrs plane results in a two-dimensional function (B) relating Crs to Rrs. Here ‘b’ represents the unique solution of Eq. 2 defining the values for Crs and Rrs for the breath under consideration