ackground : Acute respiartory failure is a condition in which an illness or impairment of the respiratory system results in inadequate oxygenation or ventilation, or both. It occurs in all age-group. The causes for acute resiratory failure are
varied
because it is a frequent complication of many diseases. Even though patients are managed intensively with mechanical
ventilation, the mortality rate has been 20-60% until today. Therefore, early prediction of
outcome in such patients should be considered a high priority so that corrective measures or
alternative support methods may be rapidly institued.
Methods : We did this study prospectively in patients who survived more than 8 days
after receiving mechasnical ventilation continuously in the Intensive Care Unit. Patients whose
initial arterial blood gas values before mechanical ventilation which showed PaO2 less than 50
mmHg or PaCO2 greater than 50 mmHg were included. We divided the patients into the
Survivor (n=66) and Non-survivor (n=74) group. During the first 7 days of mechanical
ventilation, we measured the FiO2, Pha, PaO2, PaCO2, Tidal volume, Respiratory rate, Peak
inspiratory pressure, Plateau pressure and End expiratory pressure daily. From the collected
data, the following variables were calculalted: Buffer base deviation (measured-predicted),
Minute ventilation (tidal volume×respiratory rate), Dynamic compliance [tidal volume/(peak
pressure-PEEP)], Static compliance [tidal volume/(plateau pressure-PEEP)], Pulmonary
insufficiency index, Physiologic shunt or Gas exchange indexes such as PaO2/FiO2 and
PaO2/PAO2, and our own variables such as D(A-a)O2/FiO2 and PAO2/FiO2. We compared
these variables daily between the survivor and non-survivor groups.
Results : Age didn't show a significant difference and ICU stays were longer in the
survivor group. We didn't find any significant difference in buffer base deviation, minute
ventilation, and dynamic compliance between the two groups. Static comliance showed higher
values in the survivor group and from the 4th day after mechanical ventilation, there was a
significant difference. Pulmonary insufficiency index and the ratio of D(A-a)O2/FiO2 and
PAO2/FiO2 showed significantly higher values in the nonsurvivor group throughout the first
seven days. There was a tendency of gradual decrease in the survivor group but almost no
change in the nonsurvivor group. The ratio of PaO2/FiO2 and PaO2/PAO2 showed
significantly higher values in the survivor group throughout the first seven days. There was
a tendency of gradual increase in the survivor group but almost no change in the nonsurvivor
group.
Conclusion : Static compliance, pulmonary insufficiency index, D(A-a)O2/FiO2, PAO2/FiO2,
PaO2/FiO2, and PaO2/PAO2 showed a significant difference between the survivor and
nonsurvivor groups, and each value showed the characteristic changing patterns throughout
the first 7 days after mechanical ventilation. With observation of each value and changing
patterns during the first 7 days after mechanical ventilation, these parameters were thought to
be helpful in the early prediction of outcome in mechanically ventilated patients dut to acute
respiratory failure.
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