IT201700011204A1 - DEVICE FOR THE MEASUREMENT OF SATURATION OF OXYGEN IN THE BLOOD DURING DIVING DIVING IN APNEA - Google Patents

Description

"Device for measuring oxygen saturation in the blood during <apnea> scuba diving.

The present invention relates to a device for measuring oxygen saturation in the blood during apnea scuba diving.

In the context of scuba diving in apnea, various breathing and relaxation techniques are widespread, aimed at maximizing the inhaled air and at the same time minimizing the consumption of oxygen. In particular, the respiratory act that precedes the dive, also called ventilation, has the purpose of allowing maximum oxygenation of the blood vessels as well as introducing the maximum possible amount of air into the lungs.

During the apnea phase, the level of oxygen in the blood decreases continuously and the level of carbon dioxide increases instead, with a speed depending on various factors such as the frequency of the heartbeat, the temperature of the water, muscular effort, psychophysical conditions , etc. The human body is not able to evaluate the quantity of oxygen in the blood, but it is able to provide some signals, such as the contractions of the diaphragm, which are triggered exclusively by the increase in carbon dioxide. However, these signals are not easily interpretable and even the expert freediver could erroneously assess his oxygen availability during the dive.

Should the oxygen level drop below a certain threshold, the freediver would experience a temporary loss of psycho-motor control, characterized by feelings of weakness, tremor, distorted vision and poor motor coordination. If in this phase, the freediver does not resume breathing, for example following a timely rescue, then he could be seized by the much more serious phenomenon of syncope, also called "black-out", which causes loss of consciousness and total inability to act. However, the human body reacts to a syncope with an extraordinarily fortunate response, that is through a laryngospasm which, by contracting the glottis, occludes the throat. This involuntary mechanism prevents water from invading the lungs and, in fact, drowning is prevented. In this situation the freediver can still be saved, for a few minutes, before the lack of oxygen leads to the deterioration of the main organs of the body with consequent and inevitable death.

It is clear how desirable it is to be able to measure the level of oxygen in the freediver's blood, both during the training phase to become aware of one's physical conditions and increasingly improve sports performance, and during deep dives in a natural environment to increase safety. .

Devices suitable for measuring the level of oxygen saturation in the blood are known, also called oximeters or pulse oximeters, or pulse oximeters when they also measure the heart rate. More precisely, these devices allow to measure the concentration of hemoglobin linked, in this specific case, to oxygen. It is known that oxygen-bound hemoglobin (Hb02) has a light absorption spectrum quite different from that of unbound hemoglobin (Hb), in particular in the wavelength range of light between 650nm and 700nm (red) and between 900nm and 950nm (infrared).

It is known that, through measurements of the plethysmographic signal, i.e. measurements of light absorption during the changes in blood volume between the systolic phase, in which the heart compresses the blood in the arteries, and the diastolic phase, during which the heart relaxes , it is possible to calculate the oxygen saturation in the blood as:

sp02 (%) = 110 - 25 * [AC (R) / DC (R)] / [AC (IR) / DC (IR)]

where AC (R) and DC (R) are respectively the variable and continuous part of the light signal measured when the red source is active, and AC (1R) and DC (1R) the same quantities relating to infrared light.

The most commonly used oximetry probes are applied to the index finger or earlobe for adults, and to the foot for newborns, and less commonly used probes that are applied to the wrist or abdomen using elastic bands, or to the forehead by means of elastic bands. suitable adhesives. Despite the multiplicity of known types of oximeters, none are suitable for use for free diving. In fact, it is known that due to the vasoconstriction caused by the low temperature of the water, but also due to the effect of the so-called "blood shift", a mechanism that in deep diving causes an increase in the flow of blood into the pulmonary circulation to the detriment of circulation in the limbs, avoiding in this way the crushing of the lungs, the plethysmographic signal measured on the limbs during diving is difficult to measure.

For the above reasons, the limitations of traditional oximetry probes in use during a dive, on the abdomen, due to movement, on the limbs and earlobes, due to vasoconstriction and blood shift, are clear. On the contrary, there are some parts of the head, such as in particular the temporal artery and the facial artery that in the aforementioned conditions are not deprived of the correct blood supply during a dive, under penalty of loss of consciousness.

For explanatory purposes only, figure 2 shows the plethysmographic signals measured with an oximetry probe placed in correspondence with the facial artery (A) and the temporal artery (D), the forehead (C) and the eyebrow (B), for the same subject under the same conditions, from which measurements show that the signal relating to the facial artery (A) is the largest.

Therefore, of all the areas of the human body, the region of the facial artery (A), i.e. on the cheek, between the cheekbone and the nose, and vertically under the eye, is the one that is most suitable for measuring the saturation of blood oxygen during apnea scuba diving.

The object of the present invention is to provide a device, which can be easily adapted to a diving mask, for measuring the level of oxygen saturation in the blood at the facial artery during apnea diving which allows to overcome the limitations described.

The aforementioned device allows to measure the oxygen saturation in the blood of a freediver during a dive, therefore it finds application both during the training of the freediver communicating the vital parameters to him thus allowing to improve sports performance, both during a deep immersion allowing to signal, in case of hypoxia of the freediver, the dangerous condition to other operators and freedivers in the vicinity through visual and sound signals allowing a timely rescue intervention. It is understood that the invention can be advantageously used also for applications and in fields other than what has just been indicated, in all cases in which it is necessary to measure an oximetry signal from the facial artery.

According to the present invention, a device is provided for measuring the oxygen saturation in the blood during apnea diving

as defined in claim 1.

For a better understanding of the invention, ne

the details of a form will be described

realization, purely by way of non-limiting example e

with reference to the attached drawings, in which:

- figure 1 shows by way of example, i

blood vessels of the head of a human subject;

- figure 2 shows, by way of example, various

plethysmographic signals;

- figure 3 shows an example of scheme a

operating blocks of the electronic device for

the measurement of oxygen saturation in the blood and of

heart rate;

- figure 4 is a perspective view of a

diving mask inside which the

device for measuring the saturation of

oxygen in the blood flowing through the facial artery;

figure 5 is a front view of the device

positioned within the same mask;

--Figure 6 is a side view of the face of a

freediver wearing the aforementioned mask seen in section

along the plane aa 'of Figure 5;

Figure 7 is a partially sectioned perspective view of the housing of the device for measuring the oxygen saturation in the blood;

figure 8 shows a front view and the relative section of the body of the device, when the same is not positioned on the diving mask;

- figure 9 shows a front view and the relative section of the body of the device, when it is positioned inside the diving mask.

Figure 1 shows, by way of example, the diagram of the arterial system of the head, consisting of the carotid artery 4 which branches off into the temporal artery 2 and the facial artery 3, symmetrically and mirrored both to the right and to the left. of the face. In particular, it is evident that the facial artery 3 crosses the cheek, spreading in a region of the face horizontally between the cheekbone and the nostril, and vertically in the direction of the eye.

Figure 2, for explanatory purposes only, shows the plethysmographic signals measured on head 1 in correspondence with the facial artery (A), the temporal artery (D), the forehead (C) and the eyebrow (B), in conditions resting, at room temperature, at atmospheric pressure and with the same instrument and subject.

Figure 3 shows, in an embodiment and in a non-exclusive way, the block diagram of the device 5 suitable for measuring the saturation of oxygen in the blood, comprising an oximetry sensor 6, a processing unit 7, a set of interfaces 8 and an energy accumulator 9. The oximetry sensor 6 comprises a plurality of light sources at different wavelengths, for example light emitting diodes, and a plurality of light sensors, for example photodiodes, a cancellation circuit ambient light and an analog-to-digital converter (ADC). The digital signal is processed by the processing unit 7 (CPU), which comprises numerical low-pass and high-pass filters, or equivalently band-pass, which allow to extract the direct (DC) and variable (AC) component of the plethysmographic signal. By measuring these values it is possible to calculate the heart rate (HR), such as the number of repetitions of the AC signal in the unit of time, and the oxygen saturation in the blood (Sp02). The aforementioned vital signs, heart rate and blood oxygen saturation, along with other parameters such as temperature, depth, etc. they are communicated by means of an interface system 8, comprising, for example and in a non-exclusive way, a plurality of light sources visible both from the inside and from the outside of the mask and a sound source. The aforesaid electronic devices are powered by an energy accumulator 9 so as to make the device 5 autonomous during the dive.

Figure 4 illustrates a perspective view of a diving mask 10, comprising a rigid structure or frame 11 adapted to support a pair of windows of transparent material 12, a soft structure 13 which adapts to the face of the diver, and a adjustable elastic strap 14 which secures the mask on the face of the freediver. In one embodiment, the body of the device 5 for measuring oxygen in the blood during a dive is equipped with elastic extensions 15 which, by expanding, keep it integral with the diving mask. The same figure shows the visual devices 16 and sound devices 17 for interfacing towards the outside, which will be described in detail later on.

Figure 5 shows an internal front view of the mask, in which the device 5 for measuring the saturation of oxygen in the blood is highlighted, the elastic extensions 15 which by expanding keep the same integral with the mask, the oximetry censor 6 contained in the ~ casing 19 and supported in correspondence with the facial artery of the freediver by means of the elastic support 20 and a plurality of light sources 18 arranged so as to be visible from the inside of the mask, allowing to communicate to the freediver the vital parameters measured by preset color codes or ignition sequence.

By way of explanation, figure 6 indicates the positioning of the mask 10 on the face of the freediver 1, according to the section in the plane aa 'of figure 5, in particular <it is> highlighted how the device 5 <is> integral with the mask 10 and adhering to the transparent window 12, and at the same time the elastic support 20 keeps the casing 19 of the oximetry sensor 6 pressed against the face of the freediver, in correspondence with the facial artery, more precisely in a region located horizontally between the cheekbone and the nose and vertically under the eye, with adequate pressure. Excessive pressure would cause compression of the arterial vessels and, conversely, insufficient pressure would lead to the creation of empty spaces, in both cases causing spurious optical signals and therefore errors in the measurement.

In figure 7, the partially sectioned perspective view of the device 5 shows in particular the elastic extensions 15 and the elastic support 20 of the casing 19 of the sensor 6, the latter positioned, in one embodiment, on the board on which there is also the processing unit 7, both in electrical connection not shown in the figure, with one or more energy accumulators 9 and with a plurality of light sources <1 8> visible by the freediver, with a plurality of light sources 16 visible from the outside of the mask through the transparent window 12 of the same, and with a sound source <17> in mechanical contact with a rigid part of the mask, for example the window, so as to transmit the acoustic vibration to the surrounding water and be heard by the freediver. The same figure 7 shows how all the aforesaid electronic parts are housed inside the body of the device 5, and insulated in a watertight manner from the outside by means of the walls 21 and 22, the latter fixed to the body of the device 5 by means of fastening devices. 23.

Figure 8 again shows the body of the device 5 in a front and sectional view along the plane aar, when the device itself is at rest and not positioned inside the diving mask.

Figure 9 instead shows the body of the device 5 in a frontal and sectional view along the plane aar, when the device itself is compressed by applying a force 24 on the extensions 15 so as to be positioned inside the eye cavity of the mask while remaining there. integral thanks to the elastic force of the two extensions 15. Similarly, in section aa 'of the same figure 9, it is shown how the support 20 of the oximetry sensor is deformed under the thrust 25 that the face of the apenist opposes to the compression force of the mask. During the dive, due to the variation in water pressure but also due to the variations in pressure due to the voluntary compensation of the freediver, the mask can vary its distance from the face of the freediver. It is evident that thanks to the shaping and elasticity of the material of the support 20, the sensor 6 remains positioned in correspondence with the facial artery of the freediver with constant pressure, avoiding false signals in the plethysmographic reading.

Finally, it is evident that modifications and variations can be made to the device described for measuring the oxygen saturation in the blood and its body, to the sensor support and to the elastic extensions mentioned above, without departing from the scope of the present invention, as defined in the

Claims (1)

CLAIMS 1. A device suitable for measuring the level of oxygen saturation in the blood during scuba diving in characterized apnea and comprises: b-an oximetry sensor, a processing unit and an energy accumulator; an interface device adapted to communicate the level of oxygen saturation in the blood; <m> solid body capable of constituting envelope and support for the aforementioned parts. 2. solid body according to claim 1, of such dimensions as to be contained inside a diving mask and equipped with elastic extensions of such shape as to keep it integral with the mask itself; 3. solid body according to claim 1, suitably shaped with a hollow and elastic shape such as to contain the oximetry sensor of claim 1 and to position it with adequate pressure on the face of a freediver in correspondence with the facial artery, arranged vertically under the eye and horizontally between the cheekbone and the nostril; 4. Visual signal interface device of claim 1 comprising a plurality of light sources visible to the freediver inside the diving mask, which by means of color code and intermittence frequency communicates to the freediver the level of oxygen saturation in the blood. ; 5. The interface device of claim 1 comprising a plurality of light sources, which communicates when the level of oxygen saturation in the freediver's blood falls below a certain critical threshold for the health of the freediver; 6. Suitable shaping of the solid body according to claim 1 suitable for positioning the interface device according to claim 5 facing the transparent window of the diving mask so as to be visible from the outside by other operators allowing them to promptly help the freediver; 7. Interface device of claim 1 comprising one or more sound sources, which by means of a sound code or by means of a previously recorded human voice communicates to the same freediver the level of oxygen saturation in the blood; 8. Suitable shaping of the solid body according to claim 1 suitable for positioning the interface device according to claim 7 in contact with the window of the diving mask so as to transfer the acoustic vibration to it and use the same as a solid means of propagation of the waves sound to the water with which it is in contact during the dive.