APRV-TCAV: Time Low
When managing APRV-TCAV, the most challenging and time-consuming aspect is calculating T Low. Here's how I approach it:
Initial Calculation of T Low: We begin by calculating the T Low termination point, which is 75% of the peak expiratory flow (PEFR). In this example, multiplying the PEFR by 75% gives us a value of -22.5. Based on this, we set T Low to 0.3 seconds so that the expiration terminates close to this value (this requires some estimation).
Reassessment of T Low: Over time, we need to reassess this setting frequently. For example, after 4 hours, the patient's compliance worsens, the T Low termination point shifts to 25% of PEFR. To maintain termination at 75%, we need to shorten the T Low duration accordingly.
Ongoing Adjustments: As compliance improves or worsens, T Low must be adjusted to maintain the termination point at 75% of PEFR. The slope of the expiratory flow curve is directly related to lung compliance, which is why these adjustments are necessary.
If you have any questions, feel free to reach out. Hope this helps!