Mechanical ventilation (MV) is a supportive and life-saving therapy, however, it can cause ventilator-induced lung injury as a common complication. Thus, recruitment manoeuvres (RM) are applied to open the collapsed alveoli to ensure sufficient alveolar surface area for gas exchange. In the light of the fact that positive pressure ventilation is currently the standard treat- ment for improving pulmonary function, extrathoracic negative pressure is considered as an alter- native form of respiratory support. The aim of this study was to estimate the proinflammatory and oxidative response during MV and lung injury as well as the response after RM. All studied parameters were assessed at the following time points: T1-spontaneous breathing, T2- MV, T3- lung injury, T4 –RM. During MV (T2) elastase, MPO, ALP release, nitrite and superoxide generation significantly increased, whereas in later measurements a decrease in these values was noted. The MDA plasma concentration significantly (p<0.05) increased at T2, reaching a level of 13.30±0.87 nmol/ml; at other time points the values obtained were similar to the baseline value of 9.94±0.94 nmol/ml, whereas a gradual decrease in SOD activity at time T2-T4 points in comparison with the baseline value was found. During the study both neutrophil activity and oxi- dative stress indicate exacerbated response after MV and lung injury by bronchoalveolar lavage; however, extrathoracic negative pressure system as the MR ameliorates damaging changes which could further lead to serious lung injury.
The paper shows the usefulness of the lung mechanical model for time and frequency characteristics reconstruction proper for the mechanics of an adult human respiratory system in its various regimes of work. The complex set-up for measurements of human respiratory system mechanics is presented. Two separate scenarios were created, firstly, the mechanical model was examined using standard mechanical ventilation routine with embedded Interrupter Technique and then the Optimized Ventilator Waveform technique was tested. An analysis of experimental results is presented, as well as an outline of the issues and problems revealed during investigations.