This disclosure describes systems and methods for monitoring and evaluating data associated with ventilatory parameters to detect expiratory airflow limitation in a ventilated patient. For example, a ventilator may monitor flow and/or pressure during ventilation of the patient. Based on the flow and/or pressure measurements, or ventilatory data derived therefrom, the ventilator may calculate expiratory resistance. Moreover, the ventilator may trend expiratory resistance over time to produce an expiratory resistance waveform. In embodiments, the ventilator may calculate the slope of the expiratory resistance waveform during an initial part of exhalation. If the slope of the expiratory resistance waveform during the initial part of exhalation breaches a defined slope threshold, the ventilator may determine that the patient exhibits expiratory airflow limitation.