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OPC AUTO-COMPENSATE
Breathing Sensor and Altitude Compensation
As absolute atmospheric pressure decreases with altitude, breathing efforts consequently assert less
pressure on breathing sensors to the point where inhalation may not be properly detected at higher
altitudes. Additionally, breathing effort tends to diminish as the partial pressure of CO
with altitude. The OPC must compensate for these physical and physiological effects when ascending
to higher altitudes.
The OPC employs an active algorithm that constantly and automatically adjusts the sensitivity of the
breathing sensors based on pressure altitude and detected breathing effort. It also filters out false-
triggers due to pneumatic artifacts. This helps ensure that all breaths are correctly detected so that the
OPC can respond reliably and deliver the proper amount of oxygen. This function is entirely automatic
and involves no user settings.
Automatic Respire-Metric Compensation
An average size adult, with no compromising pulmonary conditions or illnesses, will have an average
respiration rate of 12 to 18 breaths per minute. The respiration effort at rest generally becomes less
as the rate increases. Shallow breathing with an elevated respiration rate is typical with exposure to
altitude and/or anxiety.
Respiration is primarily controlled by chemoreceptors that detect dissolved CO
levels (e.g., from physical work) trigger higher respiration until CO
consequently increases oxygen levels. As the amount of dissolved CO
the urge to respirate. Therefore, as the partial pressure of CO
breathing effort will generally decrease, as the body is not compelled to respirate to expel any more CO
Unfortunately, this exacerbates hypoxia as less oxygen is inhaled and admitted into the blood.
One way to encourage respiration at higher altitudes would be to actually deliver a small amount of CO
with each inhalation. The OPC instead augments the amount of oxygen delivered to help ensure that
each individual receives the full amount of oxygen that they require in spite of reduced respiration. The
OPC uses a poly-metric method of dynamically adjusting the amount of oxygen delivered on a breath-
by-breath basis as a function of pressure altitude, respiration rate and (in some cases) breathing effort.
If the OPC is unable to establish meaningful respire-metrics for the current user (due to pneumatic
artifacts or an improperly worn cannula or facemask), it will revert to default parameters to cover a
known mean pulmonary profile.
Facemask Plenum Volume Compensation
A facemask, unavoidably, has a volume of space (plenum) that does not directly contribute to the
admission of oxygen. This plenum volume can compromise the initial admission of oxygen by allowing
the user to rebreathe CO
a portion of the delivered pulse of oxygen. While a small amount of re-inhaled CO
beneficial at higher altitudes as it encourages respiration, missing the full complement of the prescribed
amount of oxygen is not.
The F20 Mode setting of the OPC helps mitigate this effect by providing an additional bolus of oxygen with
each breath to compensate for the plenum volume associated with the facemask. The F20 Mode setting
can also be used if the user determines that they may need more oxygen than is automatically prescribed.
at the most important point of the inhalation phase and consequently displace
2
in the blood. Higher CO
2
is re-normalized. Higher respiration
2
in the blood decreases, so does
2
drops during excursions to higher altitudes,
2
27
also decreases
2
2
.
2
2
can actually be
2
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