Fig. 2

Waveform detection of patient respiratory activity and major asynchronies. Airway (Paw, gray line) and esophageal (Pes, black line) pressures are displayed on the top and flow at the bottom. Gray-colored areas refer to the subject’s neural inspiratory time according to Pes tracing. The breath in A is an autotriggered mechanical breath favored by heart noises that are evident both in airway and esophageal pressure tracings (p1). Conversely, no clear sign of patient’s inspiratory effort can be detected on flow, airway and esophageal pressure right before the mechanical breath; inspiratory flow shows exponential decay from its peak value, suggesting passive inflation (f1). In B, gray-colored area marks a patient’s inspiratory effort that is not recognized nor assisted by the ventilator. The start of patient’s inspiration can be detected as a negative deflection on Paw and Pes (p2) and a positive deflection of flow (f2) that interrupts the normal exponential decay of passive expiratory flow. The end of patient’s inspiration is located at mid-relaxation of inspiratory muscles (p3) and can be detected as the re-start of the normal exponential decay of expiratory flow (f3) and the end of a negative deflection of Paw (p4). In C, gray-colored area marks a single patient’s inspiratory effort that triggers two distinct mechanical breaths, separated by a brief expiratory phase (double trigger). The start of patient’s inspiration can be detected as a negative deflection on Paw and Pes (p5) and a positive deflection of flow (f4). The end of patient’s effort is located at mid-relaxation of inspiratory muscles (p6), occurs well after the cycling of the second mechanical breath and corresponds to the start of a normal, exponentially decaying expiratory flow (f5)