PURPOSE: Measurement of spontaneous ventilatory parameters (SVP) is an integral part of assessment for successful weaning from mechanical ventilation. The purpose of this study is to assess patients’ breathing patterns during a 5-min trial of spontaneous ventilation and to compare different method of measuring SVP.
METHODS: We studied 29 ventilated pts (18 Male, mean age 49 yr) who met standard criteria for assessing SVP during 5-min periods of spontaneous ventilation on a non-rebreathing T-piece with anesthesia bag (AB) and while breathing through the ventilator circuit in CPAP mode, in random order. Tidal volume (VT), rate (f) and minute ventilation(VE) were recorded simultaneously from a ventilation monitor (ventrack:VEN), a Wright spirometer (WS) and the ventilator's digital display (DD).
RESULTS: 0n CPAP, VT, VE and f/VT were not different for all the paired data on VEN vs WS. f in 1,2,3 and 4th min were significantly higher on DD than on VEN/WS. VT in 5th min, VE in 1 and 3 min, and f/VT in 2,3,4 and 5th min, were significantly different as measured by DD compared to VEN/WS. On CPAP, VE increased significantly derived from VEN (mean 8.5L/min. in 1st min vs 11.6 l/min in 5th min). The percentage of cases with increase in VE was: VEN, 71%; WS, 82%; DD, 61%, while on AB, it was: VEN, 68%; WS, 75%. In highest correlation coefficient was found for VE in 5th min between VEN and WS. However, the correlation between VEN/WS and DD was loose.
CONCLUSION: The ventilatory response during the SVP trial was characterized by exercise-induced hyperpnea on both CPAP and AB. VEN and WS are clinically equivalent for assessing SVPs, but making measurements using DD may give some difference.
CLINICAL IMPLICATIONS: These results suggest that results in the 1st min of SVP are not representative and may be misleading in assessment of SVP. CPAP and ABAG may not give the same results for SVP.
DISCLOSURE: T. Izumi, No Financial Disclosure Information; No Product/Research Disclosure Information