How to set TI max in NIV mode

NIV mode is a pressure‑support mode adapted to NIV conditions. One additional setting is the TI max ( On some devices, TI max is only available for adult/pediatric patients if it is enabled in Configuration. It is always available for neonatesA​) (see Figure 1).

In the absence of leaks, cycling occurs according to the expiratory trigger sensitivity (ETS) setting. This means that the inspiratory flow decreases to the percentage of peak inspiratory flow set by the user for cycling. Therefore, the actual inspiratory time varies from breath to breath according to the patient’s effort, which promotes patient‑ventilator synchrony and patient comfort.

In the case of unintentional leaks that are common in NIV, the inspiratory flow is distorted because part of the flow goes to the leak. This can be seen from the plateau‑like shape of the inspiratory flow at the end of inspiration, which matches the unintentional leak rate. The consequence is that the flow does not reach the ETS threshold and the inspiration time is prolonged. This results in delayed cycling that causes the patient discomfort. The flow of the leak corresponds to the plateau at the end of the inspiratory flow (blue arrow in Figure 2), while the volume of the leak is visible on the volume waveform as the difference between the inspiratory and expiratory volume (white arrow in Figure 2).

TI max is used to prevent delayed cycling in the case of unintentional leaks. It is usually set at 0.2 s above the actual TI without leaks, in order to preserve the normal TI variability while still preventing delayed cycling.

When TI max is set properly, the plateau in inspiratory flow is shorter (blue arrow in Figure 3) and delayed cycling thus prevented.

Another option to avoid delayed cycling is to activate IntelliSync+ ( IntelliSync+ is available as an optional feature on the HAMILTON‑C6 and HAMILTON‑G5 mechanical ventilators, and is standard on the HAMILTON‑S1.B​). By design, IntelliSync+ automatically recognizes a plateau on the inspiratory flow and cycles the breath (Figure 4).