Determining the size of the air fistula in the thoracic drainage therapy

Abstract

Devices and to methods for thoracic drainage for a patient having an air fistula. A vacuum is produced in the pleural cavity of the patient by means of a suction device. In order to adjust the vacuum on the basis of objective criteria, a suitable size measure for the air fistula is determined and the vacuum produced by the suction device is controlled according to said size measure. An adaptive algorithm includes: (a) determining a first value of a size measure for the air fistula; (b) changing the vacuum by a first difference value; (c) determining a second value of the size measure after a first waiting period; (d) changing the vacuum by a second difference value having the opposite sign if the second measure is greater than the first measure; (e) repeating steps (a) to (d) after a second waiting period.

What is claimed is: 
     
         1 - 9 . (canceled) 
     
     
         10 . An appliance for thoracic drainage in patients with an air fistula comprising:
 a suction device for generating a vacuum in a pleural space;   a control device for controlling the suction device;   a pressure gauge for measuring the generated vacuum; and   a flow meter for measuring a volumetric flow,   wherein the control device is configured to determine a size parameter for the air fistula by carrying out the following steps:   using the pressure gauge to determine a measured value for the vacuum generated in the pleural space;   using the flow meter to determine a measured value for the volumetric flow through the air fistula; and   calculating the size parameter from the measured values for the volumetric flow and the vacuum.   
     
     
         11 . The appliance according to  claim 10 , wherein the control device is configured to calculate the size parameter for the air fistula by forming a variable which is a function of the quotient from the measured value for the volumetric flow and the square root of the measured value for the vacuum. 
     
     
         12 . The appliance according to  claim 11 , wherein the control device is configured to calculate the size parameter for the air fistula as follows: 
       
         
           
             
               
                 F 
                 = 
                 
                   
                     
                       c 
                        
                       log 
                     
                     n 
                   
                    
                   
                     ( 
                     
                       Q 
                       
                         p 
                       
                     
                     ) 
                   
                 
               
               , 
             
           
         
         where 
         F is the size parameter for the air fistula, 
         Q is the measured value for the volumetric flow, 
         p is the measured value for the vacuum, 
         c is a constant, and 
         n is a positive real number. 
       
     
     
         13 - 14 . (canceled) 
     
     
         15 . A computer program for controlling an appliance for thoracic drainage in patients with an air fistula, said appliance comprising a suction device for generating a vacuum and also a digital control device for controlling the suction device, the computer program, when executed in the digital control device, causing the control device to determine a size parameter for the air fistula by carrying out the following steps:
 determining a measured value for the vacuum generated;   determining a measured value for the volumetric flow through the air fistula; and   calculating the size parameter for the air fistula from the measured values for the volumetric flow and the vacuum.   
     
     
         16 . The computer program according to  claim 15 , wherein the computer program, when executed in the digital control device, causes the control device to calculate the size parameter for the air fistula by forming a variable which is a function of the quotient from the measured value for the volumetric flow and the square root of the measured value for the vacuum. 
     
     
         17 . The computer program according to  claim 17 , wherein the computer program, when executed in the digital control device, causes the control device to calculate the size parameter for the air fistula as follows: 
       
         
           
             
               
                 F 
                 = 
                 
                   
                     
                       c 
                        
                       log 
                     
                     n 
                   
                    
                   
                     ( 
                     
                       Q 
                       
                         p 
                       
                     
                     ) 
                   
                 
               
               , 
             
           
         
         where 
         F is the size parameter for the air fistula, 
         Q is the measured value for the volumetric flow, 
         p is the measured value for the vacuum, 
         c is a constant, and 
         n is a positive real number. 
       
     
     
         18 - 20 . (canceled) 
     
     
         21 . A method for thoracic drainage in a patient with an air fistula, in which method a vacuum is generated in the pleural space of the patient, said method comprising the following steps for determining a size parameter for the air fistula:
 determining a measured value for the vacuum generated in the pleural space;   determining a measured value for the volumetric flow through the air fistula; and   calculating the size parameter for the air fistula from the measured values for the volumetric flow and the vacuum.   
     
     
         22 . The method according to  claim 21 , wherein the size parameter for the air fistula is calculated by forming a variable which is substantially a function of the quotient from the measured value for the volumetric flow and the square root of the measured value for the vacuum. 
     
     
         23 . The method according to  claim 22 , wherein the size parameter for the air fistula is calculated as follows: 
       
         
           
             
               
                 F 
                 = 
                 
                   
                     
                       c 
                        
                       log 
                     
                     n 
                   
                    
                   
                     ( 
                     
                       Q 
                       
                         p 
                       
                     
                     ) 
                   
                 
               
               , 
             
           
         
         where 
         F is the size parameter for the air fistula, 
         Q is the measured value for the volumetric flow, 
         p is the measured value for the vacuum, 
         c is a constant, and 
         n is a positive real number. 
       
     
     
         24 - 29 . (canceled) 
     
     
         30 . The appliance according to  claim 10 , wherein the control device is configured to regulate the level of the vacuum as a function of said size parameter. 
     
     
         31 . The computer program of  claim 15 , the computer program, when executed in the digital control device, causing the control device to regulate the level of the vacuum generated by the suction device as a function of said size parameter. 
     
     
         32 . The method of  claim 21 , comprising automatically regulating the vacuum generated by the suction device as a function of said size parameter. 
     
     
         33 . The method of  claim 23 , wherein in calculating the size parameter for the air fistula, the constant c=1. 
     
     
         34 . The method of  claim 23 , wherein in calculating the size parameter for the air fistula, the positive real number n=5. 
     
     
         35 . The appliance according to  claim 35 , wherein the control device is configured to calculate the size parameter for the air fistula by mathematically linking the measured values of the volumetric flow and of the vacuum to each other, in order thereby to allow a conclusion regarding the size parameter. 
     
     
         36 . The computer program according to  claim 15 , wherein the computer program, when executed in the digital control device, causes the control device to calculate the size parameter for the air fistula by mathematically linking the measured values of the volumetric flow and of the vacuum to each other, in order thereby to allow a conclusion regarding the size parameter. 
     
     
         37 . The method according to  claim 21 , wherein the size parameter for the air fistula is calculated by mathematically linking the measured values of the volumetric flow and of the vacuum to each other, in order thereby to allow a conclusion regarding the size parameter.