[Predictive value of a risk prediction model guided by the ratio of respiratory rate to diaphragmatic thickening fraction for the timing of noninvasive-invasive mechanical ventilation transition in patients with acute exacerbation of chronic obstructive pulmonary disease].

To evaluate the predictive value of a risk prediction model guided by the ratio of respiratory rate to diaphragm thickening fraction (RR/DTF) for noninvasive-invasive mechanical ventilation transition timing in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD), through ultrasound evaluation of diaphragm movement indicators.