Three Breaths, Three Stories

In cases where a patient exerts minimal inspiratory effort, the flow-time scalar usually displays an exponential decay, while the pressure remains constant throughout the inspiratory phase in pressure support mode. A similar appearance can also be observed during false triggering when the patient is in a passive state. 

In the second breath, the waveform exhibits typical characteristics of pressure support waveforms, indicating the possibility of either a patient-triggered breath with minimal inspiratory effort or false triggering. false trigger/ auto trigger was identified because of the absence of inspiratory effort on clinical examination and the presence of airleak.

The third breath is initiated by the patient, and this can be determined by analyzing the morphology of the scalars. When there is a significant inspiratory effort, the inspiratory flow-time scalar may exhibit a rounded appearance. Additionally, the pressure-time scalar will show certain changes. At the beginning of the breath, the pressure will be below the target pressure due to the negative pressure generated by the inspiratory muscles. Towards the end of the breath, there will be a pressure spike indicating the relaxation of the inspiratory muscles.

Upon examining the first breath, it is evident that the morphology of the initial half of the inspiratory phase resembles that of a passive breath or false triggering. However, in the latter part, the waveform indicates the presence of inspiratory muscle activity identified by the pressure drop in the pressure-time scalar and increased inspiratory flow. Initially, the breath is triggered by an air leak, giving the appearance of a passive breath. Subsequently, neural inspiration occurs, leading to noticeable changes in the waveform morphology. This can be identified as early trigger, as ventilator initiates mechanical inflation before the onset of neural inspiration, resembling a reverse trigger.