Abstract: To discuss the reasons of respiratory function failure,the authors observed the spontaneous breath of 19 patients who received mechanical ventilation(Control Mode) due to acute respiratory functiron failure from chest operation and epigastrium operation,and analyzed the correlation of the oxygenation index (PaO₂/FiO₂) and the ratio of spontaneous breath surpassing control rate(PPsuper).The results showed the effect of oxygenation on the spontaneous breath rate in patients with respiratory function failure from chest operation and epigastrium operatior,the negative correlation between PaO₂ and PPsuper (r=－0.575),the negative correlation between PaO₂/FiO₂ and RRsuper(r=-0.571) and no correlation between PaCO₂ and RRsuper.

Key words: respiratory function failure, mechanical ventilation, respiratory rate, the oxygenation index