الفهرس 
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Abstract
COPD patients account for a large proportion of mechanically ventilated cases in the respiratory intensive care unit. The main objective of mechanical ventilation is to maintain both adequate oxygenation and ventilation, reduce the work of breathing (WOB) and improve the comfort of the patient until the condition that forced the need for this technique has been reversed or alleviated. As the weaning process represents 40–50% of the total duration of mechanical ventilation, so choosing the method of weaning procedure is important to shorten the weaning process and minimize the mechanical ventilation time. It involves a two-step strategy, begins with an assessment regarding readiness for weaning which is then followed by SBT as a diagnostic test to determine the likelihood of successful extubation. Until now the best weaning procedure has not yet been established. Pressure support ventilation (PSV) is commonly utilized and is the sole mode of mechanical ventilation used during the weaning process in about 21% of patients. In recent years, development of new dual controlled closed-loop ventilatory modes, which could support spontaneous breathing, has made it possible to gradually decrease the mechanical ventilatory support. Volume support ventilation (VSV) is one of the new modes. The aim of this study was to investigate the superiority of pressure support ventilation (PSV) versus volume support ventilation (VSV) in weaning of mechanically ventilated COPD patients that could help improving their general management and reducing the mechanical ventilation time. In order to attain these objectives 500 COPD patients were admitted to Assuit RICU during the period from October 2017 to January 2020 and needed ventilatory support. Out of 150 COPD patients fulfilled the inclusion criteria and were intubated, Only 50 COPD (33.3%) patients met the criteria of weaning and started weaning process, the remaining 100 patients (66.6%) did not start weaning either because of death in 85 patients (56.6%), or unplanned extubation in 15patients (10%).All included patients were subjected to clinical evaluation including medical history, physical examination and ideal body weight (IBW), laboratory investigations including biochemical investigations and ABG. They were also subjected to imaging assessment including chest x-ray, chest ultrasound and Echocardiography. Additionally the severity of illness was assessed within the first 24 hours after ICU admission using APACHE II score. The whole study group were assigned to synchronized intermittent mandatory ventilation, volume controlled mode (SIMV, VC) for at least 48 hours then patients who fulfilled criteria for weaning readiness were randomized in a ratio of 1:1 using either PSV including 25 patients (first group) or VSV including 25 patients (second group).Then, we assessed extubation outcome and weaning duration after a SBT with VSV and compared it with PSV. The following results were observed: As regards baseline and start of weaning data; no significant difference was found between VSV and PSV groups. So, both modes of weaning can be conveniently compared with each other in term of weaning course and outcome, length of stay and the occurrence of complications and mortality. The results demonstrated the effect of VSV on physiological parameters (variations in respiratory rate, spontaneous tidal volume, minute ventilation, pressure support and oxygenation parameters). Respiratory rate values, Minute ventilation and pressure support values were significantly higher for VSV than PSV after 1st minute and after 30 minutes of SBT with significant lower peak pressure. Also oxygen saturation values were significantly higher for the VSV group than PSV group after 1st minute and remains equal at the end of SBT. The weaning duration was significantly shorter in VSV than PSV (12.76 ± 8.02 vs. 18.56 ± 5.97 (h); P= 0.04). Also, VSV had higher successful extubation than PSV (80% versus 76%) with fewer incidence of complications. As regard weaning course VSV group showed shorter ICU length of stay and mechanical ventilation duration with less ICU mortality when compared to PSV. During evaluation of all these variables collectively, the observed differences were efficient and worthy and this study can state that VSV might improve weaning process in COPD patients. Conclusion: VSV was safe, reliable method and can be reasonably used for weaning trials in COPD patients. VSV confers a potential benefit in decreasing weaning duration, enhancing success rate of first SBT, shorter ICU length of stay, less incidence of complications and lower mortality rate.