A self-inflating resuscitation system formed from a self-inflating resuscitation bag and an exhalation indicator. In particular, the self-inflating resuscitation bag provides an exhalation indicator, which may be an audio or visual indicator, or both. The exhalation indicator enables a caregiver to more accurately determine whether a patient is being ventilated, unlike prior art self-inflating resuscitation bags, and helps to detect esophageal intubation in intubated patients or gastric trapping of gas in non-intubated patients undergoing positive pressure ventilation. In general, the device may be interposed between any source of positive pressure ventilation and any airway device to monitor exhalation as an indicator of adequacy of ventilation.