Figure 4From: A feasibility study on bedside upper airway ultrasonography compared to waveform capnography for verifying endotracheal tube location after intubation Quantitative waveform capnography (ETCO2). The picture on the left shows a positive quantitative waveform capnography (ETCO2), which means ETT is in the trachea (correct placement). The picture on the right shows a negative ETCO2, which means ETT is not inside the trachea.Back to article page