To determine if the work of breathing measurement is necessary for adjusting the level of pressure support ventilation (PSV). If the PSV level is too high, the respiratory muscle load is decreased and muscle atrophy may occur. If the PSV level is too low, the excessive respiratory muscle work may cause fatigue. In both cases, a delay in weaning may occur.
We studied 16 adult intubated (surgical, cardiac, medical) intensive care unit (ICU) patients with a variety of clinical conditions during the weaning process. We randomly called 10 ICU clinicians (6 attendings, 3 fellows, and 1 physician assistant) to perform 50 clinical evaluations (based on the available clinical / laboratory data, physical examination, and ventilator settings), and 50 PSV level decisions (increase, decrease, do not change), based on these evaluations. Of these 50 evaluations, 45 were performed by attendings, 4 by fellows, and 1 by a physician assistant. On 19 occasions, two different clinicians evaluated the same patient simultaneously (blinded to each other). We continuously recorded the work of breathing (WOB [J/L]), power of breathing (POB [J/min]), and pressure-time product (PTP [cm H2O . sec/min]), 30 min before and 30 min after each evaluation, and averaged the data over 1 hour. The clinicians were blinded to WOB data. According to the values of WOB, POB, and PTP, we made a theoretical PSV change for each patient, based on muscle load.
By comparing the clinical and theoretical decisions using a Stuart-Maxwell test, we found a statistical value of 34.31, which indicates a significant difference between the two groups (p<0.001). Also, during the 19 simultaneous evaluations, the clinicians had a 31.6% disagreement rate in their decisions.CONCLUSIONS: The measurement of the WOB must be added to the clinical data to appropriately adjust the levels of PSV for each patient.
A better adjustment of the PSV level in mechanically ventilated patients, based on direct measurement of the work of breathing can facilitate weaning.
E.J. Adhami, None.