The Hypoxic Training index (HTi) provides an objective measure of the hypoxic stress delivered during the

Intermittent Hypoxic Training Intermittent hypoxic training (IHT), also known as intermittent hypoxic therapy, is a technique aimed at improving human performance by way of adaptation to reduced oxygen. * Procedure An IHT session consists of an interval of several minutes br ...

(IHT) session, compared to simple recording the inhaled fraction of oxygen (FiO2). HTi provides a figure (index) of dosage received by the individual at the end of the session. Knowledge of HTi can therefore be used to alter the training regime for different individuals, compensating for individual variability, and can be used in scientific studies to ensure that subject exposure was correctly controlled. Tissue hypoxia develops only when arterial oxygen saturation (

SpO2 Oxygen saturation is the fraction of oxygen-saturated hemoglobin relative to total hemoglobin (unsaturated + saturated) in the blood. The human body requires and regulates a very precise and specific balance of oxygen in the blood. Normal arter ...

) drops to 90% or below. This is due to the oxyhaemoglobin dissociation curve. Saturations above 90% produce very little effect or decrease of arterial oxygen partial pressure (PaO2). In order to obtain consistent and comparable values of HTi for different individuals the following conditions should be stipulated: * The values of SpO2 above 89% are not considered in the calculation of HTi, as such saturation levels do not contribute to the treatment.

values below 75% count as 75%. * HTi is calculated as an integral value of

readings made with 1 s sampling frequency and divided by 60 in order to produce a “per minute” value. * During the treatment target

values are in the range of 75% - 89%.

Calculation

The resulting formula for calculating HTi is:

HTi = \frac  \int\limits_^t 0-SpO_2(t) dt

where:
HTi : Hypoxic Training index,
t : period of time, and
SpO2 (t) : SpO2 (%), arterial oxygen saturation value measured at one-second intervals. HTi Graph

This image shows a typical

curve during a full biofeedback-controlled IHT session. (FiO2 is altered automatically using biofeedback controlled

hypoxicator A hypoxicator is a medical device intended to provide a stimulus for the adaptation of an individual's cardiovascular system by means of breathing reduced oxygen hypoxic air and triggering mechanisms of compensation. The aim of intermittent hypo ...

to attain and sustain the desired SpO2 target value.)

Software

Advanced biofeedback controlled hypoxicators are capable of adjusting the oxygen concentration in the inhaled hypoxic air automatically. This automatic biofeedback control allows targeting of the desired

, compensating for individual variability. Software is also availablehttp://fellrnr.com/wiki/Hypoxic_Timer Software to calculate HTi from a pulse oximeter to calculate HTi based on readings from a USB connected Pulse Oximeter.

References

{{Reflist Respiratory therapy