الفهرس 
ACUTE RESPIRATORY FAILUREOnly 14 pages are availabe for public view
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Abstract
This study was conducted in the Respiratory Intensive Care Unit of Thoracic Medicine Department, Mansoura University Hospital, during the period from July 2011 to August 2013 after fulfilling departmental ethical committee requirements and having oral consent of the patients or their surrogate.
The study aimed at comparing pressure- versus flow- triggering in ventilating patients with acute respiratory failure.
In this clinical trial one hundred patients with acute respiratory failure of pulmonary origin were randomly assigned into two groups; 50 patients ventilated with pressure triggering and 50 patients with flow triggering. The primary end points were weaning duration, evaluating patient/machine synchronization, total duration of ventilation and ICU stay as well, time under sedation and occurrence of complications. Mortality was considered as secondary end point.
Exclusion criteria included:
a) Extra pulmonary causes of acute respiratory failure.
b) Non medical causes of acute respiratory failure e.g. trauma.
c) Patients aged above 70 year ,or below 18 year .
d) Post cardiac arrest.
e) Advanced malignancy with or without metastasis.
• Patients were assorted into obstructive, restrictive and combined pulmonary disease according to their past medical history, and clinical and radiological assessment.
• All selected patients were intubated and connected to the ventilator using; Inspiration Events ventilator. Settings were tailored according to the clinical condition indicating mechanical ventilation and the monitoring of clinical, laboratory and lung mechanics data along the course of ventilation. The medical therapy and nursing care were individualized according to the original problem indicating mechanical ventilation. Analgo/sedation was achieved with Midazolam (bolus and/or infusion) and/or fentanyl (bolus and/or infusion) with dose adjustment according to clinical indication and response considering morning sedation vacation for reassessment.
• The following were done for every patient:
- Clinical evaluation including history and examination.
- Admission and follow up chest X ray.
- Laboratory data admission and follow up including electrolytes, arterial blood gases and complete metabolic profile. Thyroid profile was done for indicated patients.
- Admission severity scoring through APACHE II score.
- Patient/machine synchronization using Riker sedation/ agitation scale .we categorized our patients into comfortable (scale number 4) i.e having synchronization and non comfortable (scale 5,6,7,1,2,3) having less synchronization.
- Recording duration of need to sedation, total duration of ventilation, waning duration and total ICU stay.
- Recording complications and mortality.
- Monitoring patients according to ICU guidelines.
• Mechanical ventilation for both pressure and flow groups was started by using conventional pressure- or volume- control mode or dual mode [pressure regulating volume control (PRVC) or alternating between both. When the patients were turned to spontaneous-breath mode the pressure trigger was set at -2 cmH2O and the flow trigger was set at 2 L/min. Nursing care and pharmacological management were dynamically tailored according to every patients scenario.
• Weaning was done by using either pressure support and or T piece trials after completing daily weaning checklist according to Corrado et al., 2004 .
• The data were recorded on a report form, tabulated and analyzed using the computer program SPSS (Statistical package for social science) version 16 .
This study showed:
In all studied patients (n: 100)
There was statistically significant shorter duration of weaning in flow triggering group (2.76 days) than pressure triggering group (5.48 days) with p<0.001.
Total duration of ventilation was shorter in flow triggering group (4.72 days) compared with (8.18 days) in pressure triggering group which was statistically significant (p<0.001).
The pre extubation oxygenation index was statistically significant better in flow triggering group than pressure triggering group (266.72 and 196.10 ;p<0.001.
Most of self extubation occurred in pressure triggering group (20%) compared to 14 % of flow triggering group had , without significant difference p=0.425.
Total duration of ICU stay was statistically shorter in flow triggering group than pressure triggering group (5.80 days versus 9.86 days) respectively with P<0.001.
No significant differences was detected between pressure triggering group and flow triggering group as regard the occurrence of complications (P=0.677) , 38 % and 34% respectively.
There was no statistically significant difference in mortality in both groups despite being more in pressure 44.0% compared to 36 % in flow (P= 0.414).
Pneumothorax was the most frequent complication in flow triggering group (10%), while hemoptysis was the most frequent complication among pressure triggering group (8%).
- In obstructive pulmonary disease group (n: 23):
There was no significant difference between both pressure triggering and flow triggering groups as regard; weaning duration (2.78 days versus 2.64 days with p=0.867) duration of ventilation (4.67 days and 4.07 days ,p=0.547 ) and total duration of ICU stay (6.56 days versus 4.93 days, p=0.181).
- In restrictive pulmonary disease group (n: 56):
Weaning duration, duration of ventilation , total duration of ICU stay and duration of using sedation were significantly shorter in flow triggering group than pressure triggering group (2.52 versus 6.5 days, 4.6 versus 9.7 days, 5.68 versus 11.4 days and 2.24 versus 6.52 days respectively, with p<0.001 for all.
Oxygenation index (Pre extubation PaO2/FIO2) was significantly higher in flow triggering group than pressure triggering ( 307.64 versus 181.35, p <0.001).
Ventillation (Pre extubation PaCO2) was 34.2 mmHg in flow triggering group and 42.2 mmHg in pressure triggering group , p=0.41.
Patients were more comfortable in flow triggering group than pressure triggering group (64.0% versus 61.3%) with no significant differences.
In combined pulmonary disease group (n: 21) :
Weaning duration, duration of ventilation, total duration in ICU stay and duration of using sedation were insignificantly shorter in flow triggering group than pressure triggering group (3.45 versus 4.60; p=0.197, 5.73 versus 6.40 days; p=0.649, 7.18 versus 8.00 days; p=0.626, 2.82 versus 4.50 days; p=0.12) respectively.
There was non significant increase in self extubation among pressure triggering group (20.0%)compared with flow triggering group (18.2%). Rreventilation was non significantly more in flow triggering group (36.3%) compared with (10.0%)in pressure triggering group (p=0.311).
Patients with APACHEII score ≥ 32.5 (n: 74) :
Weaning duration, duration of ventilation, total duration of ICU stay, and duration of using sedation were statistically shorter in flow triggering group than pressure triggering group (2.64 versus 5.60 days, 4.64 versus 7.94 days, 5.69 versus 9.49 days, 2.33 versus 5.26 days respectively) with p<0.001 for all.
Pre extubation oxygenation index was significantly higher in flow triggering group than pressure triggering group ;275.95 versus189.06 with p<0.001. Ventilation( Pre extubation PaCO2) was better also in flow triggering group (35.67 mmHg) than pressure triggering group (48.67 mmHg), but it was non statistically significant p=0.411
Flow triggering is more suitable in those need complete or near complete ventilator support due to high severity scoring (frist hours on ventilation)
Patients with APACHEII less than 32.5 (n: 26):
- Weaning duration ,duration of ventilation, total duration of ICU stay and duration of using sedation were non significantly shorter in flow triggering group compared with pressure triggering group (3.18 versus 5.20 days, p=0.148, 5.00 versus 8.73 days; p=0.222, 6.18 versus 10.73 days; p=0.129, 2.64 versus 5.40 days; p=0.098) respectively.
Flow or pressure triggering can be used near weaning or when partial ventilator support is needed (last hours of ventilation )