ABSTRACT
Objective To investigate the feasibility and efficiency of monitoring noninvasive respiratory effort and respiratory load-capacity ratio in patients undergoing weaning from mechanical ventilation by mean inspiratory pressure(Pi) which were calculated on the basis of the formula, Pi = 5 × P 0.1 × Ti, as well as the noninvasire tension index calculated from Pi(TTIi). Method Totally 12 patients undergoing weaning from mechanical ventilation were enrolled in the study and their underlying diseases included COPD( n = 9), ARDS( n = 2) and status asthmaticus(n = 1) respectively. Esophageal pressure(PesoM) was monitored via the insertion of esophageal balloon and corrected esophageal pressure(Peso) was acquired by subtracting elastic pressure of chest wall from PesoM. P 0.1, Maximal inspiratory pressure on esophageal pressure curve(MIPeso) and on airway pressure curve(MIPaw) was measured with conventional technique. Pi was calculated on Pi = 5 × P 0.1 × Ti. Pi and MIPaw were used to calculate the noninvasive tension-time index TTIi, whereas Peso and MIPeso were used to calculate the invasive counterpart TTIeso. Comparisons, Correlation and Bland-Altman agreement analysis were made between P0.1 and Peso as well as between TIIi and TTIeso. Results There were no significant differences between Pi and Peso as well as between TTIi and TTIeso(P > 0.05) ,and the correlation coefficients were 0.974 and 0.957 respectively. In the agreement analysis, the mean difference between Pi and Peso, and between TTIi and TTIeso were lower than the minimal values of(Peso + PiSB )/2 and of(TIIi + TTIeso)/2, respectively. Conclusions There is a good correlation between Pi and Peso as well as between TTIi and TTIeso, in which Pi is calculated calculated from P 0.1 and in turn the TTIi is calculated from Pi. The noninvasive indices including Pi and TTIi can be used to monitor respiratory effort and respiratory load-capacity in patients undergoing weaning from mechanical ventilation.