الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Non-invasive ventilation (NIV) is now considered the gold standard ventilator management for patients suffering from an acute exacerbation of COPD with respiratory acidosis[3]. However, it has a high failure rate of 25%[6–9]. Patient intolerance to this techniques is one of the causes of this failure rate[10].One of the key factors determining tolerance to NIV is the optimal synchrony between the patient‘s spontaneous breathing activity and the ventilator‘s set parameters, known as ‗‗patient–ventilator interaction‘‘[11,12]. Optimal patient–ventilator synchrony can be very difficult to achieve, especially during NIV, due to the presence of leaks at the patient-mask interface which can interfere with the various aspects of ventilator function [13–15]. In addition, the presence of altered respiratory mechanics, dynamic hyperinflation and intrinsic positive end-expiratory pressure (PEEP) in COPD patients may impose higher risk for patient-ventilation asynchrony (PVA)[16]. One of the tools to detect gross PVA is the bedside monitoring and analysis of ventilator waveforms (mainly pressure and flow)[17]. Detection of PVA is the first step in its management. The effects of ventilator waveforms analysis on ventilator management has been studied only in one trial by Di Marco et al [18], and the study showed a significant positive effect on physiological and patient-centered outcomes during acute exacerbation of COPD.
The aim of our randomized controlled trial was to test and compare the efficacy of waveform analysis on ventilator settings (optimized ventilation) versus standard ventilation in patients under NIV for acute exacerbation of COPD to increase the rate of pH normalization as a primary outcome. In addition, we aimed to assess the effect of this technique on patient physiological response (respiratory rate, tidal volume, PaCO2, P/F ratio), ventilator settings changes (PEEPext, pressure support, rise time, inspiratory trigger), patient-ventilator interaction (tolerance, asynchrony index) and the major endpoints (NIV success rate, on-ventilator days, ICU length of stay, mortality rate). Our trial has been carried out in Critical Care Medicine Unit at Menoufia University Hospitals, Menoufia, Egypt. It included any patient more than 18 years old of both genders affected by acute COPD exacerbation, respiratory acidosis and hypoxemia who required NIV. The study was carried out from May 2014 to August 2016, and enrolled fifty patients. At the beginning of the trial, the patients were randomized using a computer-generated sequence into two groups; group 1 “Optimized ventilation” (screen analysis-driven ventilation): the operator assessed the flow and pressure waveforms on the screen in real time, and all changes in the ventilator settings have been performed accordingly as specified in details below. group 2 “Standard ventilation”: all changes in the ventilator settings have been performed according to the numerical data only. Waveforms were used only to identify asynchrony and to calculate Asynchrony Index (AI).
For each For each patient, the following data were recorded;
1) general demographic information,
2) clinical data at baseline, 0.5, 2, 6 and 24 hours after the beginning of NIV. Clinical data included: respiratory rate, tidal volume (expressed per Kg of ideal body weight), patients tolerance to ventilation, AI, and ventilator settings (PEEPext, level of pressure support, inspiratory triggering and the speed of pressurization).
3) blood gas analysis at baseline, 2, 6 and 24 hours after the beginning of NIV,
4) the final outcome of the treatment assessed by NIV failure rate, days of MV, ICU length stay and death.
Our trial showed that ―Optimized Ventilation‖ group was associated with higher rate of pH normalization at six hours compared to the ―standard ventilation‖ (36% vs. 12%; P value = 0.047). On-ventilator days were significantly decreased in the ―optimized ventilation‖ group compared to the standard group (3.68 days vs. 7.20 days; P value = 0.012). PaCO2 was significantly decreased in a higher rate in the ―optimized ventilation‖ group at 2, 6, and 24 hours (P values were 0.032, 0.008, and 0.001 respectively). At the all points of time, patients treated with the ―optimized ventilation‖ were ventilated with a higher level of PEEPext (P values < 0.05), a faster speed of pressurization and more sensitive inspiratory trigger (P value = 0.001) without any difference in the level of pressure support. Also, there was a significant improvement in the asynchrony index after 2 hours (P value = 0.002)