Patent Description:
The measurement of oxygen delivery to the body and the corresponding oxygen consumption by its organs and tissues is vitally important to medical practitioners in the diagnosis and treatment of various medical conditions. Oxygen delivery is useful, for example, during certain medical procedures, where artificially providing additional oxygen to the patient's blood stream may become necessary. For example, during an intubation procedure, the patient will stop breathing while the procedure is performed. The patient is typically provided with oxygen before the intubation procedure. Because the patient stops breathing during an intubation procedure, the patient's blood oxygen saturation level will fall. In that situation, the medical practitioner must ensure that the patient has sufficient reserves of oxygen in their system before intubation so that during the intubation procedure suffocation is avoided. At the same time, providing oxygen at a high pressure to a patient can cause damage to the alveoli of an adult patient. On the other hand, even normal oxygen levels can or cause blindness in neonatal patients.

The current standard of care is to measure oxygen delivery through the use of a pulse oximeter. Pulse oximeters measure oxygen saturation (SpO<NUM>). SpO<NUM> represents the percent of available hemoglobin that can chemically bind with oxygen molecules.

Another indicator of oxygen delivery is the partial pressure of oxygen (PaO<NUM>), However, there are currently no reliable ways to measure PaO<NUM> noninvasively. Invasive PaO<NUM> measurements require expensive sensors and are known to carry serious side effects that can harm the health of a patient.

<CIT> describes an apparatus for determining a risk of retinopathy of prematurity in a patient that may include a processing unit. The processing unit is configured to determine whether an oxygen saturation level of the patient extends beyond an oxygen saturation threshold, determine an extent that the oxygen saturation level of the patient extends beyond the oxygen saturation threshold, and trigger an alarm when the extent that the oxygen saturation level of the patient extends beyond the oxygen saturation threshold exceeds a threshold at which the patient may be at risk of developing retinopathy of prematurity.

<CIT> describes a physiological monitoring system which can include a physiological monitor having one or more processors that can derive oxygen saturation values from a patient. The oxygen saturation values can correspond to values of oxygen saturation in blood at a tissue site of the patient. The physiological monitor can output an indication of amplitude of the differences per respiratory cycle in the oxygen saturation values.

<CIT> describes an alarm system for pulse oximeters, based on fuzzy logic, which differentiates false alarms, caused by artifact, from true alarms. Numeric input variables and corresponding fuzzy sets (oxygen saturation HIGH (high O2), NO (normal O2) and YES (desaturation) and rate of change of oxygen saturation (HIGH, MEDIUM and LOW) and their membership functions.

Embodiments of the present disclosure provide a hypersaturation index for measuring a patient's absorption of oxygen in the blood stream after a patient has reached <NUM>% oxygen saturation. This hypersaturation index provides an indication of an increased level of dissolved oxygen in the plasma. This is useful, for example, for patients that are on supplemental oxygen therapy or are on a ventilator or closed-loop positive pressure delivery device. An excessively high level of PaO<NUM> can be dangerous for most patients. In some patients, for example neonates, a high level of PaO<NUM> can cause loss of eyesight. Significant damage can occur to the lungs, and in particular, to the alveoli structures in the lungs, if the PaO<NUM> level is too high.

In another embodiment, a timer is provided that indicates when a hypersaturated patient is likely to return to a baseline saturation level after oxygen administration is stopped. This is useful, for example, during an intubation procedure.

Pulse oximetry is a noninvasive technique which allows the continuous in vivo measurement of arterial oxygen saturation and pulse rate in conjunction with generation of a photoplethsymograph waveform. Measurements rely on sensors which are typically placed on the fingertip of an adult or the foot of an infant. As explained in detail below, the ratio of red and infrared light signals absorbed at the measuring site is calculated (R/IR ratio). Oxygen saturation level is determined using a lookup table that is based on empirical formulas that convert the ratio of red and infrared absorption rates to a SpO<NUM> value.

A correlation exists between the R/IR ratio and the level of PaO<NUM>. This relationship between R/IR ratio and PaO<NUM> levels, however, varies from patient to patient. For example, at the same PaO<NUM> level, one patient may have a R/IR ratio of <NUM> and another patient may have a reading of <NUM>. Therefore, once the absorption level reaches <NUM>%, it becomes difficult for the medical practitioner to assess the patient's condition with respect to PaO<NUM> and the potential dangers of a high level of PaO<NUM>. Without the ability to accurately measure the PaO<NUM> level, medical practitioners are in need of a noninvasive way to monitor a patient's hypersaturation status.

In an embodiment, a hypersaturation index is calculated based on the reading of the R/IR ratio at the measurement site. In an embodiment, a maximum hypersaturation index threshold is determined such that an alarm is triggered when the hypersaturation index reaches or exceeds the threshold. In another embodiment, an alarm is triggered when the hypersaturation index reaches or falls below its starting point when it was first calculated.

In particular, the disclosure provides a method of measuring a patient's rising oxygen saturation levels during a treatment using a pulse oximeter device, the method comprising:.

According to a preferred implementation, the indication of rising oxygen saturation is a hypersaturation index.

According to another preferred implementation, the hypersaturation index is an indication of the partial pressure of oxygen.

According to another preferred implementation, the displaying of the indication of rising oxygen levels comprises displaying a graph of an oxygen hypersaturation index.

According to another preferred implementation, the displaying of the indication of rising oxygen levels comprises generating an alarm in response to the indication of rising oxygen levels being above or below a certain threshold.

In particular, the disclosure further provides a method for alerting a caregiver of a patient's oxygen saturation level during a treatment using a pulse oximeter device, the method comprising:.

According to a preferred implementation, the method further comprises:.

According to another preferred implementation, the activated alarm is an auditory alarm.

According to another preferred implementation, the activated alarm is a visual alarm.

In particular, the disclosure further provides a method of measuring a patient's rising oxygen saturation levels during a treatment using a pulse oximeter device, the method comprising:.

According to a preferred implementation, the time includes a range of times.

According to a preferred implementation, the method further comprises determining an inflection point in measured ratio values indicating that the patient is no longer receiving oxygen.

According to a preferred implementation, a baseline saturation is initially determined before that patient is hypersaturated with oxygen.

In particular, the disclosure further provides a timer display, the display comprising:.

The drawings and following associated descriptions are provided to illustrate embodiments of the present disclosure and do not limit the scope of the claims. Corresponding numerals indicate corresponding parts, and the leading digit of each numbered item indicates the first figure in which an item is found.

Aspects of the disclosure will now be set forth in detail with respect to the figures and various embodiments. One of skill in the art will appreciate, however, that other embodiments and configurations of the devices and methods disclosed herein will still fall within the scope of this disclosure even if not described in the same detail as some other embodiments. Aspects of various embodiments discussed do not limit the scope of the disclosure herein, which is instead defined by the claims following this description.

Turning to <FIG>, a patient monitoring system <NUM> is illustrated. The patient monitoring system <NUM> includes a patient monitor <NUM> attached to a sensor <NUM> by a cable <NUM>. The sensor monitors various physiological data of a patient and sends signals indicative of the parameters to the patient monitor <NUM> for processing. The patient monitor <NUM> generally includes a display <NUM>, control buttons <NUM>, and a speaker <NUM> for audible alerts. The display <NUM> is capable of displaying readings of various monitored patient parameters, which may include numerical readouts, graphical readouts, and the like. Display <NUM> may be a liquid crystal display (LCD), a cathode ray tube (CRT), a plasma screen, a Light Emitting Diode (LED) screen, Organic Light Emitting Diode (OLED) screen, or any other suitable display. A patient monitoring system <NUM> may monitor oxygen saturation (SpO2), hypersaturation, perfusion index (PI), pulse rate (PR), hemoglobin count, and/or other parameters.

<FIG> illustrates details of a patient monitoring system <NUM> in a schematic form. Typically a sensor <NUM> includes energy emitters <NUM> located on one side of a patient monitoring site <NUM> and one or more detectors <NUM> located generally opposite. The patient monitoring site <NUM> is usually a patient's finger (as pictured), toe, ear lobe, or the like. Energy emitters <NUM>, such as LEDs, emit particular wavelengths of energy, typically red and infrared light signals, through the flesh of a patient at the monitoring site <NUM>, which attenuates the energy. The detector(s) <NUM> then detect the attenuated energy and send representative signals to the patient monitor <NUM> for processing. The patient monitor <NUM> includes processing board <NUM> and a host instrument <NUM>. The processing board <NUM> includes a sensor interface <NUM>, signal processor(s) <NUM>, and an instrument manager <NUM>.

The host instrument typically includes one or more displays <NUM>, control buttons <NUM>, a speaker <NUM> for audio messages, and a wireless signal broadcaster <NUM>. Control buttons <NUM> may comprise a keypad, a full keyboard, a track wheel, and the like. A patient monitor <NUM> can include buttons, switches, toggles, check boxes, and the like implemented in software and actuated by a mouse, trackball, touch screen, or other input device.

The sensor interface <NUM> receives the signals from the sensor <NUM> detector(s) <NUM> and passes the signals to the processor(s) <NUM> for processing into representations of physiological parameters. These are then passed to the instrument manager <NUM>, which may further process the parameters for display by the host instrument <NUM>. The processor(s) <NUM> may also communicate with a memory <NUM> located on the sensor <NUM>; such memory typically contains information related to the properties of the sensor that may be useful in processing the signals, such as, for example, emitter <NUM> energy wavelengths. The elements of processing board <NUM> provide processing of the sensor <NUM> signals. Tracking medical signals is difficult because the signals may include various anomalies that do not reflect an actual changing patient parameter. Strictly displaying raw signals or even translations of raw signals could lead to inaccurate readings or unwarranted alarm states. The processing board <NUM> processing generally helps to detect truly changing conditions from limited duration anomalies. The host instrument <NUM> then is able to display one or more physiological parameters according to instructions from the instrument manager <NUM>, and caregivers can be more confident in the reliability of the readings.

When oxygen molecules come into contact with blood, the majority of the oxygen molecules are bound to the hemoglobin in red-blood cells and a small portion is dissolved directly in the blood plasma. Both of these processes are driven by the partial pressure of oxygen. In the lung, oxygen diffuses across the alveolar membrane, and then the red cell membrane in lung capillaries. When an oxygen molecule encounters a molecule of hemoglobin, it wedges itself between the iron atom and a nitrogen atom attached to the globin chain. This helps to hold the heme group in place in the protein. One molecule of hemoglobin with its four heme groups is capable of binding four molecules of diatomic oxygen, O<NUM>. The pigment of the oxygen loaded heme group, which is called oxyhemoglobin, is a brilliant red color. This is typically the color of arterial blood. Pressure from dissolved oxygen in plasma and in the surroundings in the red cell helps to keep the oxygen on its binding site.

As the blood circulates to the periphery, the small amount of plasma dissolved oxygen is consumed first by cells in organs and tissues, which causes a drop in the partial pressure of oxygen. This release in pressure makes available the much larger reservoir of heme-bound oxygen which begins a sequential unloading of its four oxygen molecules. At the most, under normal circumstances only <NUM> molecules of oxygen are unloaded. Partially or fully unloaded hemoglobin is called deoxyhemoglobin. It is a dark blue to purplish color. This is also the typical color of venous blood.

There is a general relationship between the oxygen saturation in blood and the partial pressure of oxygen. This nonlinear relation is described by the oxygen dissociation curve as shown in <FIG> illustrates a graph of SaO<NUM> versus the partial pressure of oxygen dissolved in the arterial blood, PaO<NUM>. As the partial pressure of oxygen in the arterial blood increases, the percentage of oxygen saturation of the hemoglobin will increase. After the SaO<NUM> level reaches <NUM>%, the PaO<NUM> level continues to rise, but the SaO<NUM> level will not rise further. Thus, although it is possible to estimate PaO2 levels when SaO2 is below <NUM>%, as illustrated in <FIG>, after a certain point, very large changes in the PaO<NUM> will produce little change in the SaO<NUM>. A patient whose physiology falls on the first part of the curve is commonly referred to as the Hypoxic. As can be seen from <FIG>, there is a high sensitivity around PaO<NUM> = <NUM> mmHg, i.e. the slope is large. A patient whose physiology falls on the second part of the curve where SaO<NUM> begins to level off is Normoxic. In the last portion of the curve, where SaO<NUM> has reached <NUM>%, a patient is considered Hyperoxic.

<FIG> illustrates a graph showing the potential shift in the disassociation curve based on an individual patients response. For example a left shift may occur with decreased temperature, decreased <NUM>,<NUM>-diphosphoglycerate (<NUM>,30DPG), increased pH, or higher CO in the blood. As another example, a right shift will occur with reduced affinity, increased temperature, increased <NUM>,<NUM> - DPG and decreased pH. Thus, there is some-uncertainty when determining PaO<NUM> based on the SaO<NUM> measurement. This uncertainty can be reduced if the pH and temperature are given as inputs to the device where an appropriate curve may be selected.

The following oxygen content equation relates the amount of oxygen present in the blood given certain hemoglobin concentration (tHb) and partial pressure of oxygen (PaO<NUM>) <MAT>.

Alternatively, the Oxygen Content can be measured directly using a Masimo Rainbow Pulse Oximeter available from Masimo Corporation of Irvine, Ca.

Tissues need a requisite amount of O2 molecules for metabolism. Under steady state conditions the O2 consumption is fairly constant. In order to quantify the relationship between oxygen transport and its consumption the Fick principle can be applied. The essence of the Fick principle is that blood flow to an organ can be calculated using a marker substance if the following information is known:.

In Fick's original method, the "organ" was the entire human body and the marker substance was oxygen.

This principle may be applied in different ways. For example, if the blood flow to an organ is known, together with the arterial and venous concentrations of the marker substance, the uptake of marker substance by the organ may then be calculated.

As discussed above, hemoglobin and plasma are the main oxygen vectors in the blood. The oxygen content equation can be combined with the Fick principle to describe oxygen consumption and its relationship to blood flow as shown below in Eq.<NUM>.

Where OC is Oxygen consumption (mL / min), Ca is Cardiac output (i.e.. local blood flow at the test site (dL / min)), tHb is the Total hemoglobin (gram / dL), SaO2 is Arterial saturation fraction (<NUM> - <NUM>), SvO2 is Venous saturation fraction (<NUM> - <NUM>), PaO<NUM> is the Partial pressure of oxygen in the arterial blood (mmHg), PvO2 is the Partial pressure of oxygen in the venous blood (mmHg), <NUM> represents the HbO2 carrying capacity (mL O2 / gram Hb), and <NUM> represents O2 solubility coefficient in blood (mL O2 / dL).

Pulse oximetry was invented by Dr. Ayogi in the <NUM> as a technique to measure arterial oxygen saturation noninvasively. Ayogi was able to isolate the arterial pulse absorption from tissue, bone and cartilage absorptions by looking at a signal synchronous with the heartbeat reflecting the local blood flow at the measurement site. This signal is called the photo-plethysmograph and it can be isolated by the use of a highpass filter. By exploiting the predictable relationship between arterial oxygen saturation and light absorption through a vascular bed, the arterial blood oxygen saturation (SpaO<NUM>) can be calculated noninvasively. Note that the addition of a small p to SaO<NUM> to denote calculation from an arterial pulse. It can be shown that the use of two distinct light sources, Red (R)=<NUM> and Infrared (IR) =<NUM>, a pulse oximeter can calculate the oxygen saturation noninvasively by relating a ratio = R (AC/DC) / IR (AC/DC) to the hemoglobin oxygen saturation through a typical pulse oximeter calibration curve shown in <FIG>. We will refer to this ratio as (R/IR) ratio.

Modifying Eq. <NUM>, if (SaO<NUM> - SvO<NUM>) is replaced with ΔSat, (PaO<NUM> - PvO<NUM>) replaced with ΔP, Ca replaced with the local blood flow (BF), the oxygen consumption is set to a constant and the equation is solved for BF, Eq. <NUM> results: <MAT>.

Eq. <NUM> shows an inverse relationship between blood flow and the arterio-venous saturation difference, ΔSat, as well as arterio-venous O<NUM> partial pressure difference (ΔP). At normal inspired oxygen levels, the majority of the oxygen is supplied by the hemoglobin. But when the concentration of inspired oxygen is raised, its partial pressure increases, hence ΔP, and more oxygen is delivered to the tissue through the O<NUM> dissolved in the plasma. Based on Eq. <NUM>, if we consider a digit where a pulse oximeter probe is placed, the increase of inspired oxygen partial pressure will lead to a decrease in the arterio-venous ΔSat. This is true whenever the oxygen consumption is relatively constant.

In a vascular bed the arterial vasculature is coupled mechanically to the venous vasculature through the tissues. Although this coupling is small, the optical arterial pulse, e.g. photo-plethysmograph, has invariably a small venous component. This component is not fixed across subjects but its average is indirectly calibrated for in the saturation calibration curve. Its effect on the arterial pulse is proportional to the coupling size as well as the difference between the arterial and venous saturations at the site. Let us consider a typical subject at room-air saturation of <NUM>%. Looking at the saturation calibration curve of <FIG>, a (R/IR) ratio of <NUM> corresponds to <NUM>% saturation. If the inspired oxygen concentration is increased beyond the normal O<NUM> = <NUM>%, the (R/IR) ratio continues to drop below <NUM>. An example is shown in <FIG> where the ratio starts at <NUM> and goes down to <NUM>. It can even reach a level as low as <NUM> on some subjects at an inspired O<NUM> = <NUM>%.

This behavior may be explained by the reduction in the optical effect of venous coupling as the delta saturation between the arterial and the venous is reduced due to the increase in availability of plasma oxygen. Under this condition, the venous blood will look, optically, a lot like the arterial blood. Hence, the size of the Red photo-plethysmograph signal will shrink with respect to the IR indicating a shrinking ΔSat, i.e. higher venous saturation. In <NUM>, Masimo Corporation (Masimo) introduced a new technique for calculation the venous oxygen saturation (SpvO<NUM>) by introducing an artificial pulse into the digit (see, e.g., <CIT>). By using a pulse oximeter with a probe and a subject's digit, a continuous measure of SpaO<NUM> and SpvO<NUM> can be calculated. The blood perfusion index (PI) is used as a proxy for the blood flow to the digit. <FIG> depicts such an inverse relationship between blood flow (BF) and arterio-venous saturation ΔSat.

<FIG> depicts the effect of increasing the inspired O<NUM> concentration on the calculated ΔSat. As expected there is a commensurate reduction in the ΔSat with the increase of oxygen concentration. The arterio-venous ΔSat will continue to decrease if the oxygen pressure is increased beyond atmospheric pressure. However, a point of diminishing return will be reached where no more change is possible. At that point the R/IR ratio will stop changing as shown in <FIG>. The increase in PaO<NUM> can be indirectly monitored beyond the normal <NUM> mmHg by looking at the effects of shrinking ΔSat. This cannot be done by looking at the SaO<NUM> as it will plateau at <NUM>%.

<FIG> illustrates a graph of SpO<NUM> saturation percentage <NUM> versus the R/IR ratio <NUM> according to an embodiment. In the illustrated example, the R/IR ratio is at <NUM> when the SpO<NUM> maxes out at <NUM>%. While the SpO<NUM> level will max out at <NUM>% saturation, the R/IR ratio continues to drop when more oxygen is dissolved in the blood. An embodiment calls for calculating a hypersaturation index <NUM> based on the R/IR ratio after the point <NUM> where the R/IR ratio translates to a SpO<NUM> level of <NUM>% saturation. This hypersaturation index <NUM> assists medical practitioners in exercising their judgment in ensuring that the patient's blood is not too oversaturated with oxygen. In another embodiment, the hypersaturation index is calculated in response to a user signal, i.e., not necessarily at the point where the SpO<NUM> level is at <NUM>% saturation.

Determining a level of hypersaturation is particularly important in a variety of patient types. For example, patients on supplemental O<NUM> titration are at risk of complications caused by hypersaturation. Patients on a ventilator or where FiO2 therapy is given to the patient are also at risk. Further, closed loop positive pressure O<NUM> delivery or FiO<NUM> delivery devices also place a patient at risk of hypersaturation. This may include, for example, CPAP machines or those suffering obstructive sleep apnea.

In an embodiment, the patient's oxygen saturation level SpO<NUM> is determined and monitored. When the saturation level reaches <NUM>%, an indication of rising oxygen levels, such as a hypersaturation index, is calculated. The indication of rising oxygen levels may also be displayed on an output device such as the display <NUM> in <FIG>. <FIG> is a flowchart that illustrates this embodiment.

In this embodiment, the patient's blood oxygen saturation level SpO<NUM> is determined at step <NUM>. If the blood oxygen saturation level maxes out at <NUM>% at step <NUM>, an indication of hypersaturation is calculated at step <NUM> and displayed at step <NUM>.

In another embodiment, illustrated in <FIG>, the patient's oxygen saturation level SpO<NUM> is determined and stored at step <NUM> in response to a signal from the user at step <NUM>. The signal typically indicates that a medical procedure is about to begin. A base hypersaturation index value is then calculated at step <NUM> based on the stored oxygen saturation level and the R/IR ratio. The hypersaturation index is then monitored at step <NUM> as the patient's oxygen saturation level changes. Next, an alarm trigger is generated at step <NUM> when the hypersaturation index value is less than or equal to the base hypersaturation index value as determined in step <NUM>. Finally, an alarm is activated at step <NUM> in response to the alarm trigger.

In an alternative embodiment, the oximeter monitors a patient and automatically determines a baseline oxygen saturation level and/or baseline ratio from stable measurements taken when the oximeter first begins measurements. The oximeter can indicate that a baseline measurement has been determined or can indicate that it is unable to determine a baseline measurement if stable measurements cannot be obtained. Once a baseline measurement is obtained, the oximeter will monitor the patient for an inflection point in the saturation and ratio calculations. If the oximeter finds an inflection point where the patient's oxygen saturation begins to rise and/or ratios begin to fall, it will determine that oxygen is being administered to the patient. In this way, a caregiver is not required to push a button or otherwise indicate the start of a procedure or the start oxygen administration. Along the same lines, once a patient is hypersaturated, the oximeter will monitor the saturation level and/or ratio calculations of the patient for an inflection point indicating that oxygen is no longer being administered to the patient. Again the oximeter will alarm when the oxygen saturation values and/or ratios return to their normal baseline levels.

In yet another embodiment, a maximum hypersaturation index value is also calculated and stored in response to a user signal. In this embodiment, an alarm trigger is generated when the monitored hypersaturation index value is more than or equal to the maximum hypersaturation index value.

In an alternative embodiment, a visual oxygen hypersaturation alarm is activated. The oxygen hypersaturation alarm may include text that indicates that the oxygen hypersaturation index has dropped below the base hypersaturation index value. In another embodiment, the alarm may include text that indicates that the oxygen hypersaturation index has exceeded a threshold value. The visual oxygen hypersaturation alarm may be accompanied or replaced by an audio alarm in certain embodiments.

<FIG> illustrates an example of a visualization of an indication of hypersaturation according to an embodiment. This visualization can be displayed on a display, such as the display <NUM> in <FIG>. In the illustrated embodiment, the indicator is displayed as a speedometer-type visualization. The display includes a pointer <NUM> that points to the current value of the hypersaturation indicator. The value, for example, can be on a scale of <NUM>-<NUM> or <NUM>-<NUM> to differentiate from oxygen saturation. In one embodiment, the spectrum of possible levels may be indicated by various shades or colors. For example, the low range of values may be indicated by an area <NUM> that is green in color, the medium range in values may be indicated by an area <NUM> that is orange in color, and the high range in values may be indicated by an area <NUM> that is red in color.

<FIG> illustrates another example of a visualization of an indication of hypersaturation according to an embodiment.

This visualization can also be displayed on a display, such as the display <NUM> in <FIG>. In the illustrated embodiment, the hypersaturation indicator is displayed as a bar <NUM>. In one embodiment, the size of the area of the bar that is shaded or colored depends on the value of the hypersaturation indicator. For example, a low value may be represented by a small shaded area below the "L" level <NUM>. A medium value may be represented by a larger shaded area that remains below the "M" level <NUM>. Finally, a high value may be represented by an even larger shaded area that can cover the entirety of the bar up to the "H" level <NUM>.

<FIG> illustrates yet another example of a visualization of an indication of hypersaturation. The displayed graph <NUM> illustrates hypersaturation on a scale of <NUM>-<NUM>%. The line <NUM> illustrates an estimated hypersaturation value. The shaded area <NUM> illustrates the variability of the hypersaturation index. In other words, each patient's physiology is different and depending patient, their hypersaturation my not exactly follow the population average. This is explained in more detail, for example, with respect to <FIG>. Thus, the shaded area <NUM> provides an indication of the uncertainty in the estimate <NUM>. This provides a care provider with a better indication of the actual hypersaturation that the patient is experiencing. In the embodiment of <FIG>, <NUM>% represents no detectable oxygen reserve, or no indication of hypersaturation. <NUM>% indicates a maximum detectable reserve or a maximum hypersaturation.

<FIG> illustrates an embodiment of a hypersaturation timer <NUM>. A hypersaturation timer <NUM> is useful, for example, during procedures such as a patient intubation when the patient is forced to stop breathing. The timer provides an indication of the amount of time a care giver has before the patient returns from a hypersaturated state to a baseline saturation state. The timer includes a countdown indications <NUM>-<NUM>. In the embodiment of <FIG>, the countdown begins at about <NUM> seconds and counts down to zero. When the counter is initially started, the amount of time a patient will take to return to a baseline saturation state is relatively difficult to determine. Thus, the timer <NUM> provides a range of time left which is illustrated by shaded area <NUM>. The shaded area moves clockwise around the timer indicating a range of time left before the patient reaches a baseline state. As time goes by, the amount of time a patient will take to return to a baseline saturation state becomes more predictable based on how quickly the ratios change. Thus, as illustrated in <FIG>, the range indicated by the shaded area <NUM> becomes smaller.

<FIG> illustrates another embodiment of a timer <NUM>. Similar to <FIG>, timer <NUM> has a count-down range <NUM> that decreases as time expires and the time in which a patient returns to their base line saturation becomes more certain.

In another embodiment not shown, a simple digital count-down clock could also be used to indicate the amount of time left for a hypersaturation patient to return to their baseline saturation level. The count-down clock can indicate a range or it can simple indicate a number and speed up or slow down based on the rate of return experienced by the patient.

<FIG> illustrates an embodiment count down display of an oxygen reserve, or the time left for a hypersaturation patient to return to baseline saturation. Put in other terms, the time in seconds starts increasing from zero as a subject transitions from normoxia to hyperoxia. The disply then decreases when the subject transitions from the Hyperoxic state to the Normoxic state. The display of <FIG> includes an arc indicator, for example, arc indicators <NUM>, <NUM>, and <NUM>. The indicators are arced in order to show the uncertainty range in the time left in the display. Although the arcs <NUM>, <NUM>, and <NUM> are all illustrated on the display for illustration and explanation purposes, it is to be understood that during measurement, only a single arc is displayed which according to the relative time.

Claim 1:
A patient monitoring system (<NUM>), the system (<NUM>) comprising:
a sensor (<NUM>) comprising energy emitters (<NUM>) and one or more detectors (<NUM>), the energy emitters (<NUM>) configured to be located on one side of a patient monitoring site (<NUM>) and the one or more detectors (<NUM>) configured to be located on an opposite side of the patient monitoring site (<NUM>), the energy emitters (<NUM>) configured to emit light signals of at least two different wavelengths including a red wavelength and an infrared wavelength, the one or more detectors (<NUM>) configured to detect attenuated energy and output signals representative of the attenuated energy to a patient monitor (<NUM>) for processing;
the patient monitor (<NUM>) comprising a processor (<NUM>) configured to:
determine the patient's oxygen saturation level;
in response to the patient's oxygen saturation level maxing out at <NUM>%, calculate a hypersaturation index, indicating an increased level of dissolved oxygen in the plasma or indicating the partial pressure of oxygen in the blood, based on a ratio of the attenuated energy of the at least two different wavelengths; and
a display (<NUM>) configured to display the hypersaturation index.