Patent Publication Number: US-2021187213-A1

Title: Devices and methods to create a protective gas cushion

Description:
FIELD OF THE INVENTION 
     The present invention relates to gas insufflators, also known as gas diffusers. In particular, this invention relates to a gas insufflator that is used to create a protective gas cushion in a volume. The invention also relates to methods for creating a protective gas cushion in a volume. 
     BACKGROUND OF THE INVENTION 
     During operations which are performed in an open manner, i.e. when an inner portion of the body is uncovered for the performance of the surgical operation, it may be important to prevent air from the environment from reaching the open portion of the body. A gas insufflator (or gas diffuser) can be used to modify the local atmosphere around the operation. In cardiac surgery, CO 2  is used to modify the local atmosphere in the chest cavity so that it is as near to 100 percent CO 2  as possible. This modification of the local atmosphere has been shown to reduce the number of air emboli and therefore there is a reduction in the potential for a patient to suffer a stroke or organ damage from emboli. 
     Gas insufflators can be used to create a local CO 2  atmosphere when other surgical procedures are being carried out. This will not only reduce the potential of air emboli to form but also has the potential to reduce infections. 
     When CO 2  is being used, the open end of the tube of the gas insufflator is connected to a regulated CO 2  source. The diffusing end of the gas insufflator is then placed in the area where the local CO 2  atmosphere is required. The CO 2  is then turned on and gas flows down the tube and can be diffused to create a local CO 2  atmosphere with varying degrees of turbulence, based on the design of the gas insufflator. Minimizing turbulence (i.e., maintaining substantially laminar flow) is desirable to avoid formation of turbulence which would mix of air from the environment with the local CO 2  atmosphere. 
     Gas insufflators are known, but improved gas insufflators that provide a more stable local atmosphere with less turbulence are needed. 
     SUMMARY OF THE INVENTION 
     This invention provides a device arranged to create a protective gas cushion in an outwardly open volume, the device being connectable to a gas source, the device comprising: (i) a flexible hose portion having an intake end and a discharge end and (ii) a distal tip portion connected to the discharge end of the flexible hose portion, and the distal tip portion comprising a rigid, porous polymer body having a pore size of 7 to 45 μm. The distal tip portion is adapted to be positioned in the volume and the device is arranged to supply the gas to the volume through the rigid, porous polymer body, the rigid, porous polymer body being arranged to supply the volume with the gas in a substantially laminar, continuous flow in order to enable the formation of the protective gas cushion intended to fill the volume and thereby prevent air from the environment from reaching the volume. The invention also provides a system comprising a gas source and such a device. The intake end of the flexible hose portion being connected to the gas source. 
     The invention provides a method for creating a protective gas cushion in an outwardly open volume comprising providing such a device; attaching the intake end of the flexible hose portion to a gas source; positioning the distal tip portion in the volume; and supplying the gas to the volume through the device in such a way that a substantially laminar, continuous flow of the gas is formed. The positioning of the distal tip portion in the volume and the supplying of the gas to the volume are performed so that the controlled gas flow forms the gas cushion which substantially fills the volume and thereby prevents air from the environment from reaching the volume. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred forms of the present invention will now be described by way of examples with reference to the accompanying drawings. 
         FIG. 1  shows a device of the invention attached to a gas source. 
         FIG. 2  shows a cross-sectional view of the distal tip portion of the device. 
         FIG. 3  shows a cross-sectional view of a portion of the flexible hose portion of the device. 
         FIG. 4  shows a diagram of the device of the invention in use. 
         FIG. 5  shows a graph of cumulative volume v. pressure, which is used in the calculation of pore size. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In one embodiment the invention is a device arranged to create a protective gas cushion in an outwardly open volume, the device being connectable to a gas source, the device comprising: (i) a flexible hose portion having an intake end and a discharge end and (ii) a distal tip portion connected to the discharge end of the flexible hose portion, and the distal tip portion comprising a rigid, porous polymer body having a pore size of 7 to 45 μm. The distal tip portion is adapted to be positioned in the volume and the device is arranged to supply the gas to the volume through the rigid, porous polymer body, the rigid, porous polymer body being arranged to supply the volume with the gas in a substantially laminar, continuous flow in order to enable the formation of the protective gas cushion intended to fill the volume and thereby prevent air from the environment from reaching the volume. 
     The advantage of letting the gas passing through a rigid, porous polymer body having a pore size of 7 to 45 μm is that the pores which are great in number and positioned very closely to each other function as a multiplicity of supply nozzles, and distribute the gas in thin layers lying close to each other and forming, when the gas leaves the rigid, porous polymer body, a substantially laminar continuous gas flow, which enables the formation of the protective gas cushion. The rigid, porous polymer body also causes the gas to exit through pores over the majority of the body thereby preventing a singular jetting action. The rigid, porous polymer body ensures that the gas within the tip and the delivery tube is at a higher velocity than the gas external to the tip, whereby a slow, substantially laminar, continuous gas flow is obtained. The protective gas cushion, which hereby is formed, prevents the surrounding air from reaching the volume filled by the gas cushion and thus also bacteria and other particles which may be present in the surrounding air. When CO 2  is the gas, air emboli are reduced. In addition, because the protective gas cushion is formed from a substantially laminar continuous flow of gas, turbulence is minimized and the protective gas cushion maintains separation from the surrounding air. 
     In an embodiment of the device, the rigid, porous polymer body is hydrophobic. In an embodiment, the rigid, porous polymer body is made of high density polyethylene. In another embodiment, the rigid, porous polymer body comprises a hollow interior portion. In an embodiment, the distal tip portion comprises a rigid, non-porous polymer body proximal of the rigid, porous polymer body. In one embodiment, the flexible hose portion comprises a filter to remove impurities from the gas. In an embodiment, the flexible hose portion has a length and comprises a malleable wire for at least a portion of its length. In one embodiment, the rigid, porous polymer body is arranged to supply the gas in several directions from the rigid, porous polymer body. In an embodiment, the rigid, porous polymer body has a pore size of 25 to 45 μm. 
     The invention also provides a system comprising a gas source and such a device. The intake end of the flexible hose portion of the device being connected to the gas source. In an embodiment, the gas comprises a majority of carbon dioxide. 
     The invention provides a method for creating a protective gas cushion in an outwardly open volume comprising providing such a device; attaching the intake end of the flexible hose portion to a gas source; positioning the distal tip portion in the volume; and supplying the gas to the volume through the device in such a way that a substantially laminar, continuous flow of the gas is formed. The positioning of the distal tip portion in the volume and the supplying of the gas to the volume are performed so that the controlled gas flow forms the gas cushion which substantially fills the volume and thereby prevents air from the environment from reaching the volume. In an embodiment, the outwardly open volume adjoins a portion of the body of a living organism, the portion of the body being a portion that is normally not exposed to the atmosphere. In one embodiment, the living organism is a human. In an embodiment, the gas comprises a majority of carbon dioxide. 
     The invention provides a device for creating a protective gas cushion in an open volume that adjoins a temporarily open, inner portion of a human being in order to prevent air from the environment from reaching the volume. Such an open portion is formed during operations performed openly, i.e., when an inner portion of the body is uncovered for performing a surgical operation. For instance, during heart operations a substantial part of the interior of the thorax is uncovered so that this interior portion in normal cases has direct contact with the surrounding air. 
       FIG. 1  shows a gas insufflator device  10  of the invention connected to a gas source  20 . The gas insufflator device has a flexible hose portion  30  and a distal tip portion  40 . Distal tip portion  40  includes a rigid, porous polymer body  50  at its end. The rigid, porous polymer body  50  has a pore size of 7 to 45 μm, is made of high density polyethylene, and is hydrophobic. 
     The high density polyethylene that rigid, porous polymer body  50  is made of was obtained from Porex Corporation, Fairburn, Ga., USA and is designated XM-1264. A single pore size measurement on the XM-1264 used in rigid, porous polymer body  50  yielded the following value: Pore size 29.51 μm. Pore size was measured using the Mercury Intrusion Method. In a vacuum, a mercury drop will not enter a pore due to its very high surface tension, but will if pressure is applied. It is known that, for a given pore size, a certain pressure is required to force the mercury into the pore. For each incremental increase in pressure, the change in intrusion volume is equal to the volume of the pores whose diameters fall within an interval that corresponds to the particular pressure interval. The amount of displaced mercury can therefore be used to calculate the pore size using a graphical representation. The pore size will be the average size of the pore distribution obtained (i.e. the peak value). 
     The Washburn Equation was used to convert pressure to pore diameter: 
         D=− 4 y (cos θ)/ P  
 
     where D=Diameter of pore being intruded 
     y=Surface tension of mercury 
     P=Intrusion pressure 
     θ=contact angle between mercury &amp; material 
     For example, to arrive at a pore size of 29.51 μm for combined bodies  50  and  60 , y is 480 N/m, θ is 133.4°, and P is 44.702 kPa. The intrusion pressure is the pressure at which 50% of the volume of mercury intrudes into the pores. From the graph for XM-1264 material shown in  FIG. 5 , the total volume is 634 mm 3 /g, and so 50% is 317 mm 3 /g. This pressure cuts the curve at 44.702 kPa. 
     So, we have D=−4×480×(cos 133.4°)/44.702=29.51 μm. This is the “50% value”. It means that 50% of the pores lie above this diameter and 50% lie below it. Pore size in this application, including the claims, means this 50% value, with 50% of the pores being above this diameter and 50% being below it. 
     High density polyethylene is a thermoplastic polymer having at least partially crystalline properties and a low degree of branching. The pore size of the rigid, porous polymer body  50  means that the gas, preferably CO 2 , is diffused over its full surface. The small pore size means that even at flows as low at 2.5 liters per minute (LPM) it will still act as a very efficient gas diffuser. The smaller pore size means in effect that the gas has to make more effort to exit the rigid, porous polymer body  50  and flows through more pores. So rather than having individual jets of gas exiting various points on the diffusing material, an instantaneous atmosphere is formed around the rigid, porous polymer body  50  once the gas source is turned on. The device  10  creates an instantaneous local atmosphere at the majority of points perpendicular to the surface of the rigid, porous polymer body  50  to a distance of 5 mm at a flow of 2 LPM or above. The rigid, porous polymer body  50  will only absorb blood and cause a subsequent restriction of gas flow if a negative pressure has been applied to the open end of the tube, which would draw blood into the tube. With larger pore sizes, jets of gas are produced and cause more turbulence, which increases the chance that the surrounding air could be drawn into the surgical field. Pore sizes larger than 45 micron also lead to the possibility of air being entrained into the filter material from the atmosphere when the delivery gas is being used. This air can potentially merge with the delivery gas. This occurs as a negative pressure area is created in the pores where gas is not exiting as the delivery gas passes out through the pores of least resistance. 
     The distal tip portion includes a rigid, non-porous polymer body  60  proximal of the rigid, porous polymer body  50 . As shown in  FIG. 2 , a portion of rigid, non-porous polymer body  60  has a smaller exterior diameter than rigid, porous polymer body  50 . Flexible hose  35  extends over the smaller exterior diameter portion of rigid, non-porous polymer body  60 . The rigid, porous polymer body  50  has a hollow interior portion  51  and rigid, non-porous polymer body  60  has a hollow interior portion  61 . The rigid, non-porous polymer body  60  is made of high density polyethylene. 
     The hollow interior portion  51  of rigid, porous polymer body  50  has a transverse diameter  54  of 3.6 mm and the exterior diameter  53  is 7.0 mm. The rigid, porous polymer body  50  has a length  55  of 12.5 mm. For the majority of its length, the hollow interior portion  61  of rigid, non-porous polymer body  60  has a transverse diameter  64  of 2.55 mm and the exterior diameter  63  is 3.95 mm. The rigid, non-porous polymer body  60  has a length  65  of 19.5 mm. 
     Gas flows from gas source  20  through flexible hose  33 , filter  70 , flexible hose  34 , connector  90 , the portion of flexible hose  35  that does not contain the smaller exterior diameter portion of rigid, non-porous polymer body  60 , hollow interior portion  61  of rigid, non-porous polymer body  60 , hollow interior portion  51  of rigid, porous polymer body  50  and through the multiplicity of pores  52  of rigid, porous polymer body  50  (pores  52  are indicated in  FIG. 2  but are too small to actually be seen). 
     Flexible hose portion  30  includes flexible hose  33 , filter  70 , flexible hose  34 , connector  34 , and that portion of flexible hose  35  that does not contain the smaller exterior diameter portion of rigid, non-porous polymer body  60 . Distal tip portion  40  includes rigid, non-porous polymer body  60 , rigid, porous polymer body, and the portion of flexible hose  35  that does contain the smaller exterior diameter portion of rigid, non-porous polymer body  60 . 
     Flexible hose  33  connects gas source  20  to filter  70 . Flexible hose  33  is made of ¼ inch (internal diameter) PVC tubing. The filter  70  has a housing made of polypropylene and glass fibers as a filter material. Filter  70  is used to remove impurities from the gas. Filter  70  preferably has a pore size between 0.1 to 0.4 μm. Flexible hose  34  connects gas source filter  70  to connector  90 . Flexible hose  34  is made of ¼ inch PVC tubing. Connector  90  is used to reduce the diameter of the gas flow path. Flexible hose  35  connects connector  90  to rigid, non-porous polymer body  60 . Although the portion of polymer body  60  in contact with flexible hose  35  is smooth as shown in  FIG. 2 , the portion of polymer body  60  in contact with flexible hose  35  can include one or more barbs, preferably formed into the polymer body  60 , to secure flexible hose  35  to polymer body  60 . Flexible hose  35  has a smaller diameter than flexible hose  34  and is made of PVC. The interior diameter of flexible hose  35  is 3.9 mm. Flexible hose  35  has two lumens, a first lumen  36  allowing the passage of gas and second lumen  37 , which contains malleable wire  80 . See  FIG. 3 . Malleable wire  80  is made of stainless steel and has a diameter of 0.97 mm. Malleable wire  80  allows flexible hose  35  to be shapeable to be best positioned in use. In an alternative embodiment, the device  10  does not include the malleable wire  80 . As shown in  FIG. 2 , rigid, non-porous polymer body  60  is attached to rigid, porous polymer body  50 . As shown in  FIGS. 1 and 2  the end of the rigid, porous polymer body  50  is hemispherical. The attachment of the various components can be made by methods known in the art, such as adhesives, friction fits, etc. 
       FIG. 4  shows device  10  in use. Rigid, porous polymer body  50  has placed in outwardly open volume V and adjacent to a portion P of a human body that is normally not exposed to the atmosphere, as in a surgery. Gas source  20  has been turned on and protective gas cushion GC has been formed, which fills the volume V and prevents air A from the environment from reaching the volume. As CO 2 , the preferred gas, is heavier than air, the CO 2  will accumulate in the volume V as long as the gas flow into the volume V is not turbulent. 
     In order to prevent air embolism, i.e., a blocking of the capillaries and small vessels, which may be caused by an air bubble, the protective gas cushion in a volume adjoining a temporarily, outwardly open portion of a human being, ought to include a gas, the majority of the gas is carbon dioxide. In the applications where a protective gas cushion is to be created in a volume adjoining an outwardly open inner portion of the body of a human being or an animal, it is advantageous that the gas includes carbon dioxide due to the fact that carbon dioxide has a high solubility in the tissue of the body relative to oxygen and nitrogen. In addition, carbon dioxide has at least a bacteriostatic function, which reduces the growth of bacteria and/or other microorganisms, which possibly may be present in the open portion. Furthermore, carbon dioxide is heavier than air so that a protective gas cushion in a volume adjoining an outwardly open, inner portion of a human being may be created in an easy manner. It is to be noted that the gas may be supplied to the volume in a continuous flow, wherein it is possible to ensure that the surrounding air is prevented from reaching the volume even if a part of the supplied gas leaves the area. Another possibility is, at least initially, to supply gas continuously in order to create the protective gas cushion, and then supply gas periodically to maintain the gas cushion. The device may be combined by a gas sensing member, which is arranged to sense the concentration of the supplied gas or air in the volume. By means of such a sensing, the gas supply to the actual volume may be controlled in such a way that if an increased air concentration is noted, the gas supply is also increased, or if the air concentration in the actual volume exceeds a predetermined level the gas supply is increased. It should also be noted that the gas may include oxygen, for instance in the cases when said tissue of said open body portion is strongly oxygen dependent. Oxygen, as well as carbon dioxide, is heavier than air so that the protecting atmosphere in the volume may be created in an easy manner since the heavier gas will pass downwardly in the open body portion and force away the non-sterile air present in the lower part of this open portion. 
     In an embodiment of the invention, the gas includes air. In certain applications a protecting atmosphere including sterile air may be satisfactory. The main thing is that air from the environment, i.e., non-sterile air, is prevented from reaching the volume. 
     Although particular embodiments have been disclosed herein in detail, this has been done for purposes of illustration only, and is not intended to be limiting with respect to the scope of the following appended claims. In particular, it is contemplated by the inventors that various substitutions, alterations, and modifications may be made to the invention without departing from the spirit and scope of the invention as defined by the claims.