Relationship between f/VT ratio and acute respiratory acidosis in patients submitted to noninvasive mechanical ventilation (NPPV)

Background: it was been found a significant relationship between the Tobin index (f/VT ratio) and impending ventilatory failure in patients submitted to NPPV because of acute respiratory acidosis. Aim of the study: to investigate the relationship between f/VT ratio and arterial blood gases in acute patients submitted to NPPV. Methods: we measured changes in f/VT ratio (Δ f/VT ratio), PaCO2 (Δ PaCO2) and pH (Δ pH) in 14 patients submitted to NPPV because of acute respiratory acidosis (pH: 7.22 ± 0.07), immediately before (T0) and after the withdrawal of ventilation (TW). Data: mean ± SD. Statistics: nonparametrics analysis of variance, Student's paired t test, Spearman correlation. Results: four patients failed NPPV and were intubated (Group A), whereas 10 patients were successfully weaned (Group B). A significant difference was observed in f/VT ratio between the two groups at TW ([Table 1][1]). At the same time there was a highly significant relationship between Δf/VT ratio with both ΔPaCO2 (Rho ,951, p < 0.005), and ΔpH (Rho ,875, p < 0.005). View this table: Table 1 ![Figure][2] Conclusions: 1) rapid shallow breathing suggests patient's need for supported breathing; b) as well as for patients submitted to invasive mechanical ventilation, f/VT ratio could discriminate patients weanable from NPPV. [1]: #T1 [2]: pending:yes