Tpeak/Ti Ratio
The time to peak inspiratory flow as a fraction of total inspiratory time. A low ratio may indicate early peaking and progressive airway narrowing.
What Is Tpeak/Ti Ratio?
The Tpeak/Ti ratio measures where in the inspiratory cycle peak flow occurs, expressed as a fraction of total inspiratory time (Ti). In normal breathing, peak flow typically occurs around 30-40% of the way through inspiration. Values significantly below or above this range can indicate abnormal breathing patterns.
A very low Tpeak/Ti (early peaking) followed by declining flow suggests the airway opens briefly at the start of inspiration but progressively narrows as effort increases. A very high Tpeak/Ti (late peaking) may indicate delayed airway opening or unusual respiratory muscle activation patterns.
Important caveat: on BiPAP therapy, Tpeak/Ti can be unreliable because the machine-delivered pressure support affects when peak flow occurs. The timing of the pressure transition from EPAP to IPAP interacts with the natural flow pattern, making it difficult to separate airway behaviour from machine behaviour. AirwayLab reports this metric but clinical interpretation should focus primarily on NED and Flatness Index for BiPAP users.
Normal Ranges
How AirwayLab Measures This
The NED engine computes Tpeak/Ti for every breath by finding the time of peak inspiratory flow and dividing by total inspiratory time. The per-breath values are averaged for the night summary. Note: this metric is less reliable on BiPAP therapy due to pressure support interference.
Try it with your dataFrequently Asked Questions
What does Tpeak/Ti tell me about my breathing?
Tpeak/Ti shows where in each breath your peak airflow occurs. Normal breathing peaks around 30-40% through inspiration. Early peaking followed by declining flow suggests progressive airway narrowing during the breath.
Why is Tpeak/Ti unreliable on BiPAP?
On BiPAP, the machine delivers higher pressure during inspiration (IPAP) and lower pressure during expiration (EPAP). The timing of this pressure transition affects when peak flow occurs, making it hard to separate airway behaviour from machine-driven flow patterns. NED and Flatness Index are more reliable for BiPAP users.
Related Terms
Medical Disclaimer
AirwayLab is not a medical device and is not FDA-cleared or CE-marked. It is provided for educational and informational purposes only. The analysis results should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always consult qualified healthcare providers regarding your sleep therapy and any changes to PAP settings.