ANTEROPOSTERIOR THORACIC RESTRICTION DEVICE

Abstract

The invention relates to an anteroposterior thoracic restriction device comprising holding means intended to surround a patient's chest, a compressible fluid bag, intended to be held against the patient's sternum by said holding means, and reversible bilateral tightening means, arranged on either side of the fluid bag and capable of reversibly tightening the holding means around the patient's chest.

Claims

1-12. (canceled)

13. An anteroposterior thoracic restriction device (10, 20, 40, 50, 70) comprising holding means for surrounding a patient's chest, a compressible fluid bag (11) intended to be held against the patient's sternum by said holding means, and reversible bilateral tightening means (16, 17; 25, 26; 43, 44), arranged on either side of the fluid bag and capable of reversibly tightening the holding means around the patient's chest.

14. The anteroposterior thoracic restriction device as claimed in claim 13, wherein the holding means comprise a rigid or semi-rigid anterior plate (21, 41) intended to be applied against the anterior part of the patient's chest, and optionally a rigid or semi-rigid posterior plate (22) intended to be applied against the posterior part of the patient's chest.

15. The anteroposterior thoracic restriction device as claimed in claim 13, wherein the holding means comprises a strap (14), preferentially a semi-rigid strap.

16. The anteroposterior thoracic restriction device as claimed in claim 13, wherein the tightening means are progressive tightening means.

17. The anteroposterior thoracic restriction device as claimed in claim 13, wherein the tightening means are anterolateral and/or wherein the tightening means are capable of applying a pressure of between 20 and 150 cm of water (cmH.sub.2O)20 in the fluid bag, when this is held between the strap and the patient's chest.

18. The anteroposterior thoracic restriction device as claimed in claim 17, wherein the tightening means are anterolateral and/or wherein the tightening means are capable of applying a pressure of 60 cm of water (cmH.sub.2O)20 in the fluid bag, when this is held between the strap and the patient's chest.

19. The anteroposterior thoracic restriction device as claimed in claim 13, said device further comprising a pressure sensor for measuring the pressure in the fluid bag and/or automatic release means.

20. The anteroposterior thoracic restriction device as claimed in claim 13, wherein the fluid bag contains a liquid.

21. The anteroposterior thoracic restriction device as claimed in claim 20, wherein the liquid is water.

22. The anteroposterior thoracic restriction device as claimed in claim 20, wherein the amount and/or volume of said fluid is constant in the compressible fluid bag.

23. The anteroposterior thoracic restriction device as claimed in claim 13, wherein the anterior strap or plate comprises a central housing (18, 69) for receiving the fluid bag.

24. The anteroposterior thoracic restriction device as claimed in claim 13, wherein the size of the bag is substantially equal to the dimensions of the patient's sternum.

25. An artificial ventilation system comprising a ventilator connected to a nasal and/or buccal and/or tracheal interface, for supplying air to the lungs of a patient, said system further comprising an anteroposterior thoracic restriction device as claimed in claim 13.

26. An artificial ventilation kit comprising an artificial ventilation system as claimed in claim 25, and means for depressing at least part of the patient's chest.

Description

[0029] The invention will be better understood upon reading the following description and examining the accompanying figures. These are presented by way of non-limiting illustration of the invention. The figures represent:

[0030] FIG. 1: a schematic cross-sectional representation of the chest of a patient with inhomogeneous lesions, with condensation of the posterior part of the right and left lungs;

[0031] FIG. 2: a schematic cross-sectional representation of the thoracic cage of a patient on which an anteroposterior thoracic restriction device is held according to a first example embodiment of the invention;

[0032] FIG. 3: a schematic cross-sectional representation of the thoracic cage of a patient on which an anteroposterior thoracic restriction device is held according to a second example embodiment of the invention;

[0033] FIG. 4: a schematic cross-sectional representation of the thoracic cage of a patient on which an anteroposterior thoracic restriction device is held according to a third example embodiment of the invention;

[0034] FIG. 5: a schematic representation of the essentially anterior distribution of positive-pressure artificial ventilation in a patient without the device according to the invention (A) and the posterior and inferior redistribution of positive-pressure artificial ventilation in a patient with the device according to the invention (B).

[0035] FIG. 6: a schematic cross-sectional representation of the thoracic cage of a patient on which an anteroposterior thoracic restriction device is held according to a fourth example embodiment of the invention;

[0036] FIG. 7: a schematic representation of a thoracic restriction device according to an example embodiment of the invention.

[0037] FIG. 8: a screenshot of a thoracic electrical impedance tomography (EIT) device of a mechanically ventilated cadaver (Thiel model) including the device according to FIG. 4. Box 1 describes dynamic EIT records of the Thiel model. Box 2 describes the overall impedance changes and impedance changes by region of interest, from the most anterior region (ROI 1) to the most posterior region (ROI 4) as a function of time. Box 3 describes the percentage of the total ventilation that reaches a region of interest.

[0038] As described above, some patients with respiratory failure have inhomogeneous lung lesions 1, 3. FIG. 1 shows a cross-section of a human patient's chest with the classic inhomogeneous distribution of lung lesions, lying supine (in the dorsal decubitus position), vertebrae 8 down in the figure. The distribution of global ventilation under positive-pressure leads to overdistension of the anterior areas 4 of the lungs 1, 2 and a lack of ventilation or poor ventilation of the posterior condensed areas 5 of the lungs, exposed to opening-closing lesions.

[0039] The device according to the invention makes it possible to alleviate this problem by limiting ventilation in the aerated anterior part of the lungs and by promoting the mobilization of the posterior part of the lungs. More precisely, the device according to the invention makes it possible to apply a positive extrathoracic pressure to the anterior part of the thoracic cage where said device is applied, resulting in a regional decrease in transpulmonary pressure. This regional decrease in the highest point in the lung pressure actually tends to homogenize the lung pressure throughout the lungs. When positive-pressure artificial ventilation is administered simultaneously to the patient, the anterior aerated lung areas are protected from overdistension injury by the regional decrease in transpulmonary pressure, and ventilation tends to redistribute to the posterior regions due to the homogenization of the transpulmonary pressure, all the more so as the ventilation mode is volume-controlled (i.e. insufflation of a preset tidal volume at a prescribed frequency until the set volume is reached, without the patient's participation and without taking into account his or her respiratory activity). FIGS. 2 to 4 and 6 schematically represent cross sections of a thoracic cage of a human patient, in dorsal decubitus position, provided with different embodiments of the anteroposterior thoracic restriction device according to the invention, suitable for limiting the overdistension of the anterior areas and for promoting the posterior mobilization of the lungs during positive-pressure artificial ventilation.

[0040] In FIG. 2, the anteroposterior thoracic restriction device 10 comprises a fluid bag 11 held against the patient's sternum 6 by means of a strap 12, forming holding means, which surrounds the patient's chest 7. The strap 12 is made of rigid or semi-rigid material, so that the low compliance of these holding means allows sufficient pressure to be applied by the bag 11 against the patient's sternum 6. In an embodiment, the strap 12 is made of a biocompatible material, such as polyurethane. Biocompatible material means a material suitable for use in or on biological tissues, without degrading the biological tissues involved or triggering allergic reactions during or after contact. In the context of the invention, the biocompatible material used must in particular take into account the properties of the patient's skin. In another embodiment, the strap 12 is made of leather. It is possible to use a strap of varying thickness, in particular a strap with a greater thickness in the area of contact 13 with the fluid bag 11 than in the anterolateral 14 and posterior 15 areas.

[0041] Independent bilateral tightening means 16, 17, arranged at the anterolateral levels of the chest 7, allow the strap 12 to be tightened around the patient's chest 7 to increase the positive extrathoracic pressure on the sternum 6 through the fluid bag 11.

[0042] Advantageously, the fluid bag 11 is held in position on the strap 12 so that it is not moved during use. For example, as shown in FIG. 2, the strap 12 has a housing 18 into which the fluid bag 11 can be inserted and held.

[0043] In the example embodiment shown in FIG. 3, the anteroposterior thoracic restriction device 20 comprises two semi-rigid plastrons made of preferentially biocompatible material, anterior 21 and posterior 22 respectively, forming the holding means. The anterior plastron 21 is applied against the anterior portion of the patient's chest, while the posterior plastron 22 is applied against the posterior portion of the patient's chest. Tightening means are used to hold the holding means in position on the patient's chest. More specifically, the tightening means comprise two tightening straps 23, 24, each associated with independent tightening systems 25, 26. The tightening straps 23, 24 each connect a lateral end 27, 28, of a first plastron 21 to a lateral end 29, 30, of the second plastron 22.

[0044] A fluid bag 31 is compressed between the anterior plastron 21 and the sternum 6 of the patient's chest 7. Of course, it is possible to use a thoracic restriction device that comprises only the anterior plastron. In this case, the tightening means comprises a tightening strap that completely surrounds the posterior and lateral parts of the patient's chest.

[0045] In the example embodiment shown in FIG. 4, the anteroposterior thoracic restriction device 40 comprises a rigid anterior plate 41 made of preferentially biocompatible material. The tightening means include a tightening strap 42 completely surrounding the anterolateral and posterior parts of the patient's chest 7. The tightening means also comprise independent bilateral tightening systems 43, 44. A fluid bag 45 is compressed between the anterior plate 41 and the sternum 6 of the patient's chest 7.

[0046] In an embodiment, the holding means include shoulder straps, preferentially adjustable in height. The shoulder straps are, for example, fixed at the top of the strap 12, the plastron(s) 21, 22 or the anterior plate 41. The shoulder straps prevent the support means and fluid bag from sliding down the patient's body, thus helping to keep the fluid bag in position on the sternum. The shoulder straps can consist of, or include, hook-and-loop textile strips (such as Velcro strips), which can be easily adjusted in length and repositioned.

[0047] In the example embodiment shown in FIG. 6, the anteroposterior thoracic restriction device 50 comprises a rigid or semi-rigid anterior plate 51 made of a preferentially biocompatible material, for example a biocompatible plastic. A fluid bag 52 is compressed between the anterior plate 51 and the sternum 6 of the patient's chest 7. The anterior plate 51 is connected to the tightening means by lateral holding means 53, 54.

[0048] The lateral holding means 53, 54 can be made of semi-rigid or rigid material, such as plastic or metal such as aluminum. If they are made of semi-rigid material, it is possible to provide reinforcements to further stiffen them.

[0049] The tightening means comprise tightening straps 57, 58 connecting the lateral holding means to a posterior anchoring point without coming into contact with the patient's chest 7. The tightening means also comprise independent bilateral tightening systems 55, 56.

[0050] In the example shown in FIG. 6, the tightening means are connected to a rigid or semi-rigid posterior plate 60 held against the dorsal part of the patient's chest. This posterior plate 60 is advantageously covered on its side intended to be in contact with the patient's skin with a material designed to optimize skin tolerance and limit the risk of pressure ulcers, for example a viscoelastic gel. Preferably, the posterior plate 60 is multi-perforated in order to adapt the anchoring point of the tightening straps 57,58 to the dimensions of the patient's dorsal thorax. According to another embodiment, the posterior plate forms a posterior shell that follows part of the posterolateral chest wall. Advantageously the tightening means are fixed on both sides of the posterior shell, for example by rings. Of course, it is possible to use this thoracic restriction device without a posterior plate. In this case, a single tightening strap advantageously surrounds the anterolateral and dorsal parts of the patient's chest, as shown in FIGS. 3 and 4.

[0051] In the example embodiment shown in FIG. 7, the anteroposterior thoracic restriction device 70 comprises a rigid or semi-rigid anterior plate 67 made of preferentially biocompatible material. A fluid bag 68 for application to the sternum of the patient's rib cage is attached to the inner wall (71) of the anterior plate 67. This attachment can be reversible or irreversible. The anterior plate 67 can integrate a pressure sensor 69 in direct communication with the bag 68. This pressure sensor 69 allows the pressure inside the fluid bag 68 to be displayed directly.

[0052] The anterior plate comprises lateral holding means 63, 64, 65, 66, attached to said plate. Preferably, these lateral holding means include reinforcements to stiffen them. According to an embodiment, the lateral holding means 63, 64 comprise attachment means 61, 62 intended to attach straps or shoulder straps to hold the device in the cranio-caudal direction.

[0053] In the example shown in FIG. 7, the reinforcements of the lateral holding means 63, 64, intended to be closest to the patient's shoulders, are L-shaped to provide means of attachment to the shoulder straps.

[0054] The lateral holding means 63, 64, 65, 66 extend from the anterior plate 67 on either side of said plate so as to extend perpendicularly to the patient's chest. In the example shown in FIG. 7, the lateral holding means 63, 64, 65, 66 are raised from the anterior plate.

[0055] The holding means and/or reinforcements advantageously include openings, intended for the introduction of tightening means.

[0056] Generally, the device according to the invention, when used in conjunction with a positive-pressure artificial ventilation system (invasive or noninvasive), limits the compliance of the anterior thoracic wall and thus limit the risk of overdistension of the anterior areas and promote the redistribution of the air insufflated into the posterior and inferior areas of the lungs (FIG. 5B). Conversely, in the absence of such a device (FIG. 5A), the distribution is essentially anterior, with little or no ventilation in the posterior and inferior areas.

Proof of Concept

[0057] The proof of concept was performed on a Thiel cadaver model (Thiel cadaver) under invasive mechanical ventilation. Thiel cadavers have benefited from a special embalming method, allowing them to retain the natural elasticity of the tissue. Of particular interest, the lungs of mechanically ventilated Thiel cadavers behave in a manner similar to the lungs of an ARDS patient, with condensed posterior areas and aerated anterior areas. The respiratory mechanics parameters are thus comparable to those of an ARDS patient.

[0058] During the proof-of-concept stage, a thoracic electrical impedance tomography (EIT) device was applied to cadavers with or without an anteroposterior thoracic restriction device according to the invention as described in FIG. 4. EIT allows regional measurement of impedance changes, which correspond to changes in aeration during invasive mechanical ventilation. EIT therefore allows direct visualization of ventilated areas and regional quantification of the gain or loss of aeration after a procedure.

[0059] FIG. 8 describes a screenshot of the EIT of a mechanically ventilated corpse to which the device according to the invention has been applied.

[0060] Box 1 represents dynamic EIT recordings of the cadaver during the experimental design. The EIT reports regional changes in impedance on a cross-section of the thorax. For each section, the back is at the bottom and the anterior part of the chest is at the top. Section (C) shows, in white, the envelope of all the lung regions ventilated during insufflation of the ventilator without the device according to the invention. Section (A) shows, in white, the envelope of all ventilated lung regions appears during insufflation of the ventilator with the device according to the invention in place (pressure applied to the anterior chest wall: about 80 cm H.sub.2O). Section (B) represents the regional differences in aeration between the experimental step of section (C), i.e. without the device according to the invention, and the experimental step of section (A), i.e. with the device according to the invention. The dark gray areas correspond to decreases in aeration between step (C) and step (A). The areas in light gray correspond to aeration gains between step (C) and step (A). It can be observed that the application of the device according to the invention leads to a decrease in the aeration of the anterior areas (which nevertheless remain ventilated as shown by the envelope of the ventilated areas on section (A)) and an increase in the aeration of the posterior areas with a gain in the total volume of the ventilated lung, corresponding to a recruitment of the previously nonaerated posterior areas.

[0061] Box 2 represents the overall impedance changes (top curve) and the impedance changes per region of interest, from the most anterior region (ROI 1) to the most posterior region (ROI 4), as a function of time, during the application of the device according to the invention. The four regions of interest correspond to the four rectangles numbered 1 to 4 on the EIT sections in Box 1. These impedance changes taken in isolation are difficult to interpret and one must refer to Box 3 to understand their significance.

[0062] Box 3 describes the regional proportions of impedance changes relative to the overall impedance change. It is therefore the percentage of the total ventilation that reaches a region of interest. In each region of interest, the figure in large print reports the percentage of the total ventilation with the device according to the invention in place; the figure below, in small print, reports the percentage of the total ventilation without the device according to the invention.

[0063] Thus, in the absence of a device according to the invention, 85% of the total ventilation is distributed in the anterior half of the thorax (ROI 1 and 2) and only 15% in the posterior half. With the application of the device according to the invention, 62% of the total ventilation is distributed in the anterior half and 38% in the posterior half.

[0064] The results described above therefore show that the use of the device according to the invention allows a reduction in ventilation in the anterior areas limiting the risk of overdistension, to the benefit of a gain in aeration in the posterior areas.