Abstract:
A drainage device useable for treating patients with a pulmonary air leak, the device comprising suction mode control means, where a pressure sensor is connected to the suction mode control means for supplying a pressure signal representative of the pressure in a collection chamber, and an air flow sensor is connected to the suction mode control means to supply a flow signal representative of the flow of air evacuated from the collection chamber, and in that the suction mode control means is arranged to switch between a first suction mode and a second suction mode based on an algorithm involving the flow signal and the pressure signal.

Description:
FIELD OF THE INVENTION  
       [0001]    The present invention relates to the field of medical technology. More particularly it relates to devices for pleural drainage used to aiding a collapsed lung after injury or surgery to recuperate by draining pleural cavity of excess fluid and air resulting from air leakage from injured lung and from fluid leaving the tissues in question. It also relates to a check valve for such a drainage device. 
       BACKGROUND OF THE INVENTION 
       [0002]    A device for draining fluid and air from a patient&#39;s pleural cavity is known from e.g. WO04110523. Such devices apply a suction pressure in the patients pleural cavity via a tube from the patient&#39;s pleural cavity to the draining device. By the draining fluid and applying a pressure healing is improved. An objective of the present invention is to further improve the healing when using a drainage device by modifying the device. 
       SUMMARY OF THE INVENTION 
       [0003]    The inventors have investigated the healing process and found that some patients at some point in time during their recovery may heal faster if active suction is replaced with what is referred to in the field as a “water seal”. The inventors have further investigated what the problem actually is and thereafter developed a solution. 
         [0004]    According to a first aspect the invention provides a drainage device useable for treating patients with a pulmonary air leak, said device comprising
       at least one airtight collection chamber having a first connection for a drainage tube, and a second connection for evacuation air from the airtight collection chamber;   a pressure control unit connected to the second connection of the collection chamber for controlling an air pressure in the chamber;   a pressure sensor capable of sensing the air pressure in the collection chamber;   an air flow sensor capable of sensing the flow of air evacuated from the collection chamber where the drainage device is provided with a three way valve means for connecting the collection chamber via the second connection to the atmosphere or, to a suction source, and in that said device further is provide with means for calculating, based on a pressure sensor signal from the pressure sensor, and a flow sensor signal from the flow sensor, when it is suitable to rotate the three way valve means to shift from connecting the collection chamber to the suction source to connecting the collection chamber to the atmosphere, or vice versa.       
 
         [0009]    According to a second aspect is provided a drainage device further provided with suction mode control means, where the pressure sensor is connected to the suction mode control means for supplying a pressure signal representative of the pressure in the collection chamber, and in that the air flow sensor is connected to the suction mode control means to supply a flow signal representative of the flow of air evacuated from the collection chamber, and in that the suction mode control means is arranged to switch between a first suction mode and a second suction mode based on an algorithm involving said flow signal and said pressure signal. 
         [0010]    The suction mode control means may comprise a processor and a motor for controlling a three way valve. 
         [0011]    The three way valve may be configured to switch between a position where the collection chamber is connected to atmospheric air, and a position where the collection chamber s connected to a suction pressure source. 
         [0012]    A special ball valve may be controlled by the suction pressure controlled by the three way valve. 
         [0013]    According to a further aspect is provided a method for a drainage device, the method comprising the following steps:
       reading a pressure signal from a pressure sensor arranged to sense pleural pressure;   reading a flow signal from a flow sensor arranged to sense flow of air from a pulmonary air leak;   creating a pressure difference value pD as difference between maximum of pressure signal and minimum of pressure signal during a certain period, suitably two minutes;   creating a mean flow value by averaging flow signal during a certain period;   deciding if pressure difference is less than a certain value, and at the same time the mean flow value is less than a certain value;   if so, indicating that it is so;   if not, indicating that it is not so.       
 
         [0021]    According to still a further aspect is provided a method for a drainage device, the method comprising the following steps:
       reading a pressure signal from a pressure sensor arranged to sense pleural pressure;   reading a flow signal from a flow sensor arranged to sense flow of air from a pulmonary air leak;   creating a pressure difference value pD as difference between maximum of pressure signal and minimum of pressure signal during a certain period, suitably two minutes;   creating a mean flow value by averaging flow signal during a certain period;   deciding if pressure difference is less than a certain value, and at the same time the mean flow value is less than a certain value;   if so applying a passive mode by rotating a three way valve to a passive suction position;       
 
         [0028]    if not so, applying active suction by rotating the three way valve to an active suction position. 
         [0029]    According to a last aspect of the invention is provided a special ball valve comprising a ball located and moveable between a first tube end and a second tube end, the tube ends are arranged to debouch in a common cavity, and also being arranged substantially opposite each other, and being provided with seats such that when a suction pressure is applied to one of the tubes the ball make contact to a seat and seals off that tube and leaves the other tube open to the cavity. The cavity may be provided with a further opening. 
         [0030]    It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, elements, integers, steps, components or groups thereof. 
         [0031]    Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]    The invention is described below with the aid of the following drawings in which: 
           [0033]      FIG. 1   a  shows a front cross sectional view of a check valve mechanism for switching between applying a suction pressure and applying a no pressure at all. The mechanism is in a mode of applying suction pressure. 
           [0034]      FIG. 1   b  shows the check valve mechanism of  FIG. 1   a  in a mode of applying no pressure at all. 
           [0035]      FIG. 1   c  shows in a side view the mechanism of  FIG. 1  were a motor drive unit is clearly visible. 
           [0036]      FIG. 2   a  shows a schematic diagram of a pleural drainage device making use of the mechanism of  FIG. 1   a - c.    
           [0037]      FIGS. 2   b  and  2   c  shows a detail of a special ball valve. 
           [0038]      FIG. 2   d  shows a drainage device similar to the one of  FIG. 2   a.    
           [0039]      FIG. 3  is a block diagram showing main units for controlling a drainage device in accordance with an embodiment of the invention. 
           [0040]      FIG. 4  is a flowchart showing a method of controlling the suction mode of a drainage device 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0041]      FIG. 1   a  shows a front cross sectional view of a check valve mechanism  100  for switching between applying a suction pressure and applying a no pressure at all. The mechanism is shown in a mode of applying suction pressure. The mechanism  100  comprises a first connection  105  for connection the mechanism  100  to a suction pressure source. Suction pressure is conveyed via channel opening  143  to a three way valve  125 . Direction of low of air is indicated by arrow  130 . Three way valve  125  connects suction pressure to opening  128  or to ball valve upper opening  115  which is provided with a seat  120  being able cooperate with a ball  101  to seal off the ball valve upper opening  115  and, when doing this, open a ball valve lower opening  110  by sucking the ball towards the upper opening  115 , as can be seen in  FIG. 1   b.  The upper opening  115  and the lower opening  110  is preferably arranged opposite each other on a common axis. A common cavity  107  is in this way connected to either suction pressure from a suction pressure source or to a ball valve cavity  109 , which in turn is connected to open air. The ball is preferably manufactured in a material having suitable density for being able to be manoeuvred by suction pressure in spite of simultaneously being affected by gravity. This material could be massive or hollow plastic. 
         [0042]      FIG. 1   b  shows the check valve mechanism of  FIG. 1   a  in a mode of applying no pressure at all, the three way valve is set in a position to connect suction pressure to the ball valve upper opening thereby manoeuvring the ball to open the common cavity  107  towards open air. 
         [0043]      FIG. 1   c  shows in a side view the mechanism of  FIG. 1  were a motor drive unit  150 ,  152 ,  155  is clearly visible. The motor drive unit comprises a frame  152  for holding an electric motor  150  and a gearbox  155  in a position for being able to actuate the three way valve  125 . 
         [0044]      FIG. 2   a  shows a schematic diagram of a pleural drainage device making use of the mechanism of  FIG. 1   a - c.  The drainage device comprises a suction tube  256  for connecting to a patient&#39;s pleural cavity, the tube is connected to a first opening of a collection chamber  250 . A second opening of the collection chamber  250  is in turn arranged to be connected to a suction pressure source, not shown, or to the atmosphere via a three way valve  202 . Preferably a one way valve  251 , a flow sensor  252 , and a pressure regulator  254  are arranged in conduits connecting the collection chamber  250  with the suction source or the atmosphere. The collection chamber  250  is provided with a pressure sensor  257  for sensing the pressure in the collection chamber  250 . The drainage device is further provided with control means, e.g a processor  281  and a motor  282  for processing of the pressure and flow signals sensed by the pressure sensor  257  and the flow sensor  252 . Based on the signals said control means  281 ,  282  would control the position of the three way valve based on pressure sensor signals and flow sensor signals as will be explained below. In another preferred embodiment the device is provided with an indicator for indicating when the position of the three way valve should be changed, i.e., when drainage suction mode should be shifted from “active suction mode” to “passive suction mode”. 
         [0045]    The drainage device is preferably provided with a special ball valve  270 . An advantage of providing a special ball valve is that the pressure a patients breathing musculature has to create to overcome flow resistance of the drainage device when the drainage device is in a “passive mode”, i.e., the collection chamber is connected to the atmosphere, becomes lower than otherwise. 
         [0046]    Referring to  FIGS. 2   b  and  2   c , the function of the special ball valve is that in a first position of the ball  230 , as seen in  FIG. 2   b , seat  232  together with the ball  230  seals off the tube  241  such that there is no connection to the atmosphere as long as there is negative pressure, i.e., suction pressure in tube  241  that is connected to the collection chamber. In case of positive pressure in tube  241  the ball and seat functions as an overpressure valve and let positive pressure out. In  FIG. 2   c  the ball  230  is in a second position because suction pressure of tube  215  lifts the ball  230  to seal off tube  215 . The passage of tube  241  becomes free to the atmosphere. 
         [0047]      FIG. 2   d  shows a drainage device very similar to the one of  FIG. 2   a . The processor, motor and indicator have been omitted for clarity. A three way valve  207  is arranged to connect the collection chamber  250  to a suction source when in a first position, or to the atmosphere when rotated to a second position. 
         [0048]    In still a further embodiment (not shown) the motor may be omitted for reducing production costs. Medical staff can rotate three-way valve manually if it is provided with suitable handle, instructed so by the indicator. Such omitting can be applied both to the devices of  FIG. 2   a  and  FIG. 2   d.    
         [0049]    However, it is foreseen to be more advantageous if switching is performed automatically as described above, without delay. 
         [0050]      FIG. 3  is a block diagram showing main units for controlling a drainage device in accordance with an embodiment of the invention. A pressure sensor  310  and a flow sensor  320  are connected to a processor  330 . The processor  330  processes signals from the sensors and outputs control signals to a motor  340  connected to the processor  330  to rotate a three way valve  350  mechanically connected to the motor. 
         [0051]      FIG. 4  is a flowchart showing a method of controlling the suction mode of a drainage device. The method comprising the following steps
       reading  410  pressure signal from pressure sensor  310 ;   reading  420  flow signal from flow sensor  320 ;   creating pressure difference value pD as a difference between maximum of pressure signal and minimum of pressure signal during a certain period, suitably two minutes;   creating mean flow value by averaging flow signal during a certain period, suitably two minutes;   deciding  450  if pressure difference is less than a certain value, suitably 5 cm water column and at the same time the mean flow value is less than a certain value, suitably 200 ml per minute;   if so applying  460  passive mode by rotating three way valve to passive suction position;   if not so, applying  470  active suction by rotating three way valve to active suction position.         
         [0059]    In another embodiment is provided a method for indication on an indicator that it is a suitable point in time to manually switch suction mode on a drainage device with a manually operated three way valve, the method comprising the following steps:
       reading pressure signal from pressure sensor  310 ;   reading flow signal from flow sensor  320 ;   creating pressure difference value pD as a difference between maximum of pressure signal and minimum of pressure signal during a certain period, suitably two minutes;   creating mean flow value by averaging flow signal during a certain period, suitably two minutes;   deciding if pressure difference is less than a certain value, suitably 5 cm water column and at the same time the mean flow value is less than a certain value, suitably 200 ml per minute;   if so indicating, e.g., by means of a coloured first light emitting diode, that it is a suitable point in time to apply passive mode;   if not so, indicating e.g., by means of a second light emitting diode that suction should be kept in active mode.       
 
         [0067]    It should be understood that indication of if it is suitable to switch from active to passive suction mode, or vice versa, could be achieved by any suitable device connectable to a processor, e.g., a display or a buzzer or other light or sound generating organ.