Η δραστηριότητα των εισπνευστικών μυών κατά την εκπνοή σε ασθενείς μετά από αορτοστεφανιαία παράκαμψη (bypass)

Abstract

In twelve anesthetized -paralyzed patients after coronary artery bypass graft surgery , flow(V̇ ), volume (V) and airway pressure (Paw) were measured. With airway occluded at endinspiration,Paw was measured when the patients relaxed their respiratory muscles. Dividingrelaxed Paw by tidal volume (VT), total respiratory system elastance (Ers) was obtained. Whilethe patients were still relaxed , the occlusion was released to obtain the V̇ -V relationship duringthe ensuing relaxed expiration. Under these conditions, the expiratory driving pressure is V×Ers,and thus the pressure-flow relationship of the system can be obtained. Similar measurementswere repeated during anesthesia without paralysis.Ers averaged 23,4±4,9 cmH2O×L-1 during anesthesia-paralysis and 19,8±4,9 cmH2O×L-1during anesthesia (p =0,002). The corresponding values of total Rrs were 10,09±3,90 and8,29±2,73 cm H2O×L-1×sec, respectively (p=0,08). These results indicate that Ers decreasessubstantially during anesthesia compared to anesthesia-paralysis in patients after coronary arterybypass graft surgery, whereas Rrs remains virtually unchanged. Changes in impedance due topliometric work done by the inspiratory muscles during relaxation were neglected.The first measurements of inspiratory muscle activity and related negative work duringspontaneous expiration in anesthetized patients after coronary artery bypass graft surgery is alsoprovided. Patients under investigation showed marked braking of expiratory flow by Pmusi.Themean time for Pmusi to decrease to 50 and 0 % amounted to 48,8± 27,0 msec and 1.968± 989msec, respectively. Average value for flow-resistive work amounted to 84,4±8,7 % of theelastic energy stored during inspiration.The remaining portion, used as negative inspiratorymuscle work, amounted to 15,6 ± 8,7 %.