VSV Versus PSV as a Weaning Mode of Mechanically Ventilated Chronic Obstructive Pulmonary Disease Patients

VSV Versus PSV as a Weaning Mode of Mechanically Ventilated Chronic Obstructive Pulmonary Disease Patients

Volume Support Ventilation Versus Pressure Support Ventilation as a Weaning Mode of Mechanically Ventilated Chronic Obstructive Pulmonary Disease Patients

Chronic Obstructive Pulmonary Disease (COPD) is a common, preventable and treatable disease that is characterized by persistent respiratory symptoms and airflow limitation that is due to airway and/or alveolar abnormalities usually caused by significant exposure to noxious particles or gases. Acute exacerbations may occur during the management of stable COPD which can negatively impact health status, rates of hospitalization and re-admission. During exacerbation, some patients need immediate admission to the respiratory intensive care unit (RICU) for ventilatory support. As prolonged mechanical ventilation has unfavourable impacts, it is Important to minimize the duration of mechanical ventilation and perform extubation as soon as possible. In recent years, development of numerous models of artificial respiration, which could support spontaneous breathing, has made it possible to gradually decrease the mechanical ventilatory support. From these new modes, PSV which is a well known weaning mode will be compared in our study to a new weaning mode which is a volume support ventilation (VSV).

Acute exacerbations may occur during the management of stable COPD which can negatively impact health status, rates of hospitalization and re-admission. During exacerbation, some patients need immediate admission to the respiratory intensive care unit (RICU). Ventilatory support in an exacerbation can be provided by either noninvasive (nasal or facial mask) or invasive (oro-tracheal tube or tracheostomy) ventilation. Mechanical ventilation may be complicated by barotrauma, volutrauma, and also unfavourable impacts on cardiovascular system and organ perfusion. Moreover, prolonged mechanical ventilation enhances the risk of nosocomial pneumonia. So it is Important to minimize the duration of mechanical ventilation and perform extubation as soon as possible. In recent years, development of numerous models of artificial respiration, which could support spontaneous breathing, has made it possible to gradually decrease the mechanical ventilatory support. From these new modes, PSV (pressure-support ventilation) which is a well known weaning mode will be compared in our study to a new weaning mode which is a volume support ventilation (VSV). VSV could be viewed as "PRVC for spontaneous breathing" as it delivers a variable pressure to meet a target VT. The ventilator gives a test breath with an inspiratory pressure of 10 cmH2O above PEEP (5 cmH2O in earlier software versions) It measures the volume delivered and calculates system Compliance For each subsequent breath, the ventilator calculates compliance of the previous breath and adjusts the inspiratory pressure level (pressure level) to achieve the set VT on the next breath The ventilator will not change the inspiratory pressure by more than 3 cm H2O from one breath to the next Maximum available inspiratory pressure level is 5 cm H2O below the preset upper pressure limit (alarm will sound at this point and the breath will switch into exhalation) The minimum pressure limit is the baseline setting (PEEP) If apnea occurs, back up pressure control is activated and an alarm sounds If Auto mode is on and patient becomes apneic, the mode will automatically switch to PRVC(pressure regulated volume control). In PSV patients in whom a 8 cm H2O pressure support level could be achieved,a 2-h trial of spontaneous breathing with this pressure support level will performed before extubation . In the VSV group, VT(tidal volume) will be adjusted at 6 ml/ Kg and If the patients showed good tolerance with an acceptable ABG (arterial blood gas)analysis (pH o7.35, PaO2(partial pressure of arterial oxygen)/FIO2 .150 with an FIO2(fraction of inspired oxygen) f 40%, RR (respiratory rate) f 35 breaths/min), they will ventilated for 2-h trial of spontaneous breathing and then extubated

The study group will be assigned to SIMV-VC for at least 48 hours . Patients will be assessed daily for fulfillment of criteria of readiness to wean according to European Respiratory Society guidelines (ERS guidelines ). After fulfillment of ERS weaning criteria patients will be consequently divided into two equal groups: 1. 25 patients will be assigned to PSV weaning mode. 2. 25 patients will be assigned to VSV weaning mode. In PSV weaning group , PS will be adjusted 8 cm H2O. In VSV weaning group ,VT will be adjusted 6 ml/ Kg. Extubation will be done after successful spontaneous breathing trial according to ERS guidelines .

PSV is the sole mode of mechanical ventilation and will be used as a weaning mode in mechanically ventilated chronic obstructive pulmonary disease patients,In PSV weaning group , PS(pressure support) will be adjusted at 8 cmH2O until 2-h successful spontaneous breathing trial parameters according to ERS(European Respiratory Society) guidelines will be achieved and then patient will ex-tubated.

VSV mode could be viewed as "PRVC for spontaneous breathing" as it delivers a variable pressure to meet a target VT. VSV will be used as a weaning mode in mechanically ventilated chronic obstructive pulmonary disease patients,In VSV weaning group ,VT(tidal volume ) will be adjusted at 6 ml/ Kg until 2-h successful spontaneous breathing trial parameters according to ERS guidelines will be achieved and then patient will ex-tubated.

Assess success rate of PSV and VSV in weaning of COPD patients .Weaning success is defined as extubation and the absence of ventilatory support 48h following the extubation .

if there was a decrease in the total weaning time ,assisted ventilation time and total time of mechanical ventilation .

Inclusion Criteria: All mechanically ventilated COPD patients at RICU. Exclusion Criteria: COPD patients associated bronchiectasis , interstitial lung disease and pneumonia. Neurological and neuromuscular diseases hindering the respiratory drive.

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