The Effect Of Mechanical Ventilation Mode On The Diaphragm Apoptosis And Ultrastructure In Rabbits

Background:Mechanical ventilation (MV) is a clinical intervention for patients who are unable to maintain adequate alveolar ventilation.Recent evidence reveals that controlled MV results in a swift progression of diaphragmatic atrophy and weakness.It seems that this diaphragmatic atrophy and weakness contributes to difficulty in weaning patients from the ventilator. Although several factors may contribute to delay weaning, a major determinant appears to be respiratory muscle weakness.Historically, the term "disuse atrophy" has described a situation where in sustained inactivity of the respiratory muscles (ie, passive ventilation) results in deconditioning and weakness.More recently it has been referred to as "ventilator-induced diaphragmatic dysfunction, VIDD."In contrast,"use atrophy" describes a situation where chronic high-tension inspiratory work causes structural damage to the diaphragm and weakness.Both laboratory and clinical studies demonstrated that relatively brief periods of complete respiratory muscle inactivity, as well as intense muscle loading, result in acute inflammation, loss of muscle mass, and weakness.Recent years,studies have shown that PSV mode can reduce the process of VIDD and try to use PSV mode ventilation to reduce the occurrence of VIDD.But it is not confirmed that the effects of the VIDD are modes or the level of support. The aim of this study is to analyse the diaphragm EMGdi activity in the different mode under the same level of ventilation, and observe the impact of diaphragm apoptosis and ultrastructure on healthy rabbits. Methods:Sixteen New Zealand rabbits (conventional animal,2.0kg～2.1kg) were included in this prospective randomized animal study. After intraperitoneal anesthesia, animals were randomly assigned to the control group or to receive24hours of CMV or AJC or PSV mode. After intubated with tracheostomy, connection flow transducer, continuous observation of the diaphragmatic EMGdi (diaphragm electromyo-gram, EMGdi).CMV group:Rr45bpm, FiO21L/min, and the I:E1:3, VT8-10ml/kg);A/C group: PCVmode, Trigger O.1L/min, Rr45bpm,Pi10cmH2O, Ti0.5sec, FiO225%, to maintain VT8-10ml/kg; PSV group the (Spont mode, Trigger0.1L/min, PSV10cmH2O, Esense25%, FiO225%to maintain VT8-10ml/kg). According to ABG, adjust the FiO2, VT and RR. Control group:animals were sacrificed by air embolism after monitor the EMGdi for30min, no mechanical ventilation. Ventilator support for24hours, whichever is analysed of the diaphragm immune histochemistry and western blot expression of Caspase-3activity of diaphragm of each group,and observed the ultrastructural changes of the diaphragm by electron microscopy.Result:1.Three ventilation modes significantly reduce the diaphragm electrical activity under the same level of support.EMGDi spectrum analysis result:Compared with the control group, low frequency components (L) of three groups increased, high frequency components (H) decreased,H/L decresed of82.3%,81.8%,80.6%(p<0.01) in CMVgroup, A/C group and PSV group respectively. Center frequency (Fc) decreased by43%,37.1%and34.9%, respectively (P<0.01).Significant statistics difference of Fc was found in multiple comparisons (CMV vs A/C, P<0.05; CMV vs PSV, P0.05;A/C vs PSV, P0.05).2.Caspase-3activity induced significantly by three ventilation modes,PSV mode attenuated changes in Caspase-3.Compared with control animals, the expression of17kD Acti-Caspase3of diaphragm in three modes was increased. CMV group Active-caspase3expression was strongly positive,the same as A/C mode(6.40±0.57vs5.98±0.41,P>0.05).The gray value of Western blot are2.473±0.431(p<0.01);2.202±0.213(p<0.01);1.829±1.001(p<0.05),respectively.3.PSV mode inhibited the damage of diaphragm structure.Observed through the electron microscope:The ultrastructure of diaphragm was normaL in control group.Different among the three groups,abnormal uhrastructure was observed in CMV group,including disrupted myofibrils,swollen mitoehondria, structural disorder, irregular arrangement of myofibrillar swelling of mitochondria; A/C group shows Myofibrils arranged in neat rows (some loosely arranged), part of the z line is fuzzy, the structural disorder; myofibrillar vacuolization, mitochondrial swelling, cristae deformation, dissolution; PSV group muscle fibril arranged in neat, sarcomere integrity, clear, no significant swelling of the Z line neat and clear; formation of a large number of vacuoles and lipid vacuoles in the muscle fibers mitochondrial swelling, cristae dense and rich.Conclusion:The main effection of diaphragm electrical activity is the level of ventilation support. The three modes were significantly induced the expression of Caspase-3protein, but PSV mode can reduce the diaphragm of the level of caspase-3.CMV leads to structural injury, PSV can reduce the damage of the diaphragm.