Abstract:
The invention concerns a method of storing a NO/N2 mixture in a packaging container, in particular a gas bottle, having an internal volume less than or equal to 12 liters, characterized in that a NO/N2 gaseous mixture containing between 400 ppm and 1000 ppm by volume of NO and nitrogen for the remainder is held at a pressure of at least 250 bar in the internal volume of said container. Preferably, the NO/N2 gaseous mixture is held at a pressure of 280 to 450 bar, and preferably between 300 and 420 bar.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a 371 of International Application PCT/FR2013/050818 filed Apr. 15, 2013, which claims priority to French Application No. 1254766 filed May 24, 2012, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    The invention relates to the use of an NO cylinder having an internal volume of 12 liters or less, which is suitable for and designed for containing a mixture of NO and nitrogen (NO content&gt;400 ppmv) packaged at a pressure of at least 250 bar, preferably between 300 and 500 bar. 
         [0003]    Gaseous NO is conventionally used at various concentrations ranging from 100 to 800 ppm by volume (hereinafter “ppmv”), the remainder of the gas mixture being nitrogen, for treating pulmonary vasoconstrictions, especially pulmonary hypertension in patients undergoing a cardiac surgery operation or in hypoxic newborns. In this regard, mention may be made of documents EP-A-786264 and EP-1516639. 
         [0004]    Cylinders of NO/N 2  that contain NO at the initial concentration typically between 100 and 800 ppmv may adopt various sizes ranging from 2 to 40 liters (equivalent water capacity). 
         [0005]    However, the doses of NO administered to patients range from 1 to 40 ppmv and the administration times vary from a few hours to a few days, for example up to 4 days on average, depending on the patient in question and his clinical condition. 
         [0006]    The NO must therefore be diluted, typically with air, O 2 -enriched air or N 2 /O 2  mixtures, prior to being administered to patients in order to decrease the concentration thereof to less than 40 ppmv, that is to say to the desired dosage for the patient in question. This dilution is generally carried out in the patient circuit of a ventilator. 
         [0007]    Yet the crowded state of resuscitation rooms and operating blocks, and the use of compact NO administration and monitoring systems intended to enable easier transport of patients, make it difficult to use NO/N 2  cylinders of large size, that is to say of more than 12 liters (water capacity), typically those of 20 liters. 
         [0008]    Specifically, such cylinders lead to significant overcrowding in hospital treatment rooms, are difficult to handle for the care staff, pose problems of storage and transport in buildings, etc. 
         [0009]    However, reducing the size of the gas cylinders is not sufficient as this leads to a significant loss of autonomy, that is to say that they do not contain a sufficient amount of gas in order to be able to ensure that NO is dispensed for the required treatment time that may extend over several hours, or even several days. 
         [0010]    The problem is consequently to be able to provide NO/N 2  mixtures in a small-sized storage container, that is to say having a capacity (water equivalent) of less than 12 liters, without encountering or while minimizing the aforementioned autonomy problems, that is to say small cylinders containing a sufficient amount of gas to enable the treatment of a patient over a treatment time of at least 12 to 24 hours without requiring the cylinder to be changed, preferably at least 1 to 4 days, or even longer. 
       SUMMARY 
       [0011]    The solution is a process for storing an NO/N 2  mixture in a packaging container having an internal volume of less than or equal to 12 liters, characterized in that an NO/N 2  gas mixture containing from 400 ppm to 1000 ppm by volume of NO and nitrogen for the remainder is kept, i.e stored, at a pressure of at least 250 bar, in the internal volume of said container. 
         [0012]    In other words, according to the present invention, in order to compensate for the reduction in the size of the packaging container, typically a gas cylinder, while retaining a sufficient autonomy of the container that makes it suitable for being used to treat patients suffering from pulmonary vasoconstrictions, the pressure of the NO/nitrogen mixture packaged in the container is increased. 
         [0013]    Indeed, an increase in the pressure of the gas packaged in the cylinder (at constant volume) increases the amount of NO available but without necessarily increasing its concentration, which avoids the aforementioned problems. 
         [0014]    Furthermore, this also makes it possible to avoid any excessive dose or any excessively large administration of NO due to a poor dilution or to an uncontrolled administration. 
         [0015]    Moreover, this also makes it possible to reduce the size and space requirement of the cylinders by making them easier to transport and handle in an intrahospital and extrahospital environment. 
         [0016]    However, the increase in pressure necessitates being able to provide cylinders capable of withstanding such pressures, or even significantly higher pressures. Indeed, for obvious safety reasons, the cylinders must be capable of withstanding pressures much higher than their normal operating pressure, typically a pressure 1.5 times higher than its normal operating pressure. Thus, a cylinder intended to contain an NO/nitrogen mixture at 300 bar must be able to withstand a maximum pressure of 450 bar, also referred to as test pressure. 
         [0017]    Depending on the case, the process of the invention may comprise one or more of the following technical features: 
         [0018]    the container is formed from a composite, such as fiberglass or carbon fibers, or the like, or from an aluminum alloy comprising aluminum (Al), from 1.8% to 2.6% of copper (Cu), from 1.3% to 2.1% of magnesium (Mg) and from 6.1% to 7.5% of zinc (Zn), preferably an aluminum alloy is used that additionally comprises (% by weight) from 0 to 0.15% of silicon (Si). 
         [0019]    an aluminum alloy is used that comprises (% by weight) from 86.7% to 90.7% of aluminum. 
         [0020]    a container formed from an aluminum alloy having a density of between 2 and 3.5 g/cm 3 , preferably between 2.5 and 3 g/cm 3 , typically of the order of 2.85 g/cm 3  is used. p a container of cylindrical shape having a diameter between 5 and 40 cm and a height between 10 and 80 cm is used. 
         [0021]    a container is used that has a peripheral wall having a thickness E of less than 30 mm. 
         [0022]    the container is a gas cylinder. 
         [0023]    the container of cylindrical shape comprises, at one end, a base and, at the other end, a neck with an outlet orifice, attached to which is a device for controlling the gas flow and/or for reducing the pressure. 
         [0024]    the NO/N 2  gas mixture at least 450 ppm by volume of NO, preferably up to 900 ppmv of NO, and nitrogen for the remainder. 
         [0025]    the NO/N 2  gas mixture is stored at a pressure of from 280 to 450 bar, preferably between 300 and 420 bar. 
         [0026]    the packaging container has an internal volume of less than or equal to 11 liters. 
         [0027]    the container ( 6 ) contains the NO/N 2  gas mixture at a pressure between 300 and 500 bar. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0028]    The present invention will now be better understood owing to the description given below with reference to the appended figure. 
           [0029]      FIG. 1  represents one embodiment of an installation for dispensing NO supplied by a gas packaging system according to the present invention. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0030]    Several cylinders  6  of different sizes, made of an aluminum alloy of metallurgical composition given in the table below are used for storing, at high pressure, a gas mixture formed of nitrogen monoxide (NO) and nitrogen (N 2 ). 
         [0000]    
       
         
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                 Proportion (%) by weight 
               
               
                   
                 Elements 
                 of the alloy 
               
               
                   
                   
               
             
             
               
                   
                 Pb 
                    0 to 0.003 
               
               
                   
                 Fe 
                     0 to 0.2 
               
               
                   
                 Si 
                   0 to 0.15 
               
               
                   
                 Cu 
                 1.8 to 2.6 
               
               
                   
                 Mn 
                     0 to 0.2 
               
               
                   
                 Mg 
                 1.3 to 2.1 
               
               
                   
                 Cr 
                 0.15 to 0.25 
               
               
                   
                 Zn 
                 6.1 to 7.5 
               
               
                   
                 Ti 
                   0 to 0.05 
               
               
                   
                 Zr 
                   0 to 0.05 
               
               
                   
                 Impurities 
                   0 to 0.15 
               
               
                   
                 Al 
                 remainder 
               
               
                   
                 Density of the alloy 
                 2.85 g/cm 3  approximately 
               
               
                   
                   
               
             
          
         
       
     
         [0031]    The cylinders are equipped with an integrated valve regulator  8 , also referred to as IVR, that makes it possible to control the output of gas from the container  6 . More specifically, the NO/N 2  gas mixture that is packaged therein comprises an NO content of between 400 and 1000 ppm, for example of the order of 800 ppmv, and was introduced under a high pressure into cylinders of B1, B2, B5 and B11 type, the equivalent water capacity of which is, respectively, 1, 2, 5 and 11 liters. 
         [0032]    According to the invention, the gas pressure in the cylinders  6  is at least 250 bar in the internal volume of each cylinder, preferably between 300 and 500 bar. The cylinders thus obtained contain in the end the NO/N 2  mixture at a pressure of the order of 300 bar and at a content of 800 ppmv. 
         [0033]    These cylinders were used for supplying an installation for dispensing NO to patients suffering from pulmonary vasoconstrictions, for example an installation for dispensing NO, one embodiment of which is shown schematically in the sole appended figure. 
         [0034]    This installation comprises a ventilator  1  comprising a respiratory circuit or patient circuit  2  with two branches, that is to say with an inhalation branch  3  and an exhalation branch  4 . The inhalation branch  3  is designed to convey respiratory gas from the ventilator  1  to the patient P, whereas the exhalation branch  4  is designed to convey the gas exhaled by the patient P to the ventilator  1 . At the patient P, the gas is administered by means of a patient interface  11 , for example a respiratory mask or a tracheal cannula or catheter. 
         [0035]    The ventilator  1  is supplied, via several delivery lines  10 ,  10 ′, with air (O 2  content of 21% by volume) originating from an air source  7  and with oxygen resulting from an oxygen source  7 ′, such as gas cylinders or lines transporting, respectively, medical air and oxygen originating from an oxygen production unit, such as a pressure swing (PSA) unit, or from an oxygen storage unit, such as a buffer or storage tank. The air is enriched in oxygen in the ventilator  1  and the oxygen-rich gas thus obtained is delivered by the ventilator  1  into the inhalation branch  3  of the patient circuit  2 . 
         [0036]    Furthermore, a device  5  for dispensing NO is fluidically connected to said inhalation branch  3  of the patient circuit  2  in order to deliver thereto, via a feed line  12 , an NO/N 2  mixture having a concentration of at least 400 ppm by volume. The device  5  for dispensing NO is itself supplied with an NO/N 2  mixture, via a gas feed line  9 , by an NO container  6  according to the invention, such as an aluminum gas cylinder (cf. Table 1) equipped with a valve or integrated valve regulator  8 , preferably protected by a cap for protection against impacts. 
         [0037]    The device  5  for dispensing NO makes it possible to control the amount of NO/N 2  released into the inhalation branch  3 , and also the method of releasing this mixture, that is to say continuously or in a pulsed manner, for example only during the inhalation phases of the patient P. Therefore, in the inhalation branch  3 , a dilution of the NO/N 2  mixture with the oxygen-rich gas distributed by the ventilator  1  takes place. The dilution depends on the content of the initial NO/N 2  mixture and also on the concentration of gas to be administered to the patient. 
         [0038]    Table 2 below gives the capacity (in liters of gas) of various packagings having capacities of 0.5 to 20 liters (i.e. B0.5 to B20) at various pressures (in bar). 
         [0000]    
       
         
               
               
             
               
               
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
             
             
               
                   
                   
               
               
                   
                 Filling pressure (bar) 
               
             
          
           
               
                   
                 150 bar 
                 200 
                 250 
                 300 
                 350 
                 400 
               
             
          
           
               
                 Type of cylinder 
                 vol L 
               
               
                   
               
             
          
           
               
                 B0.5 
                 75 
                 100 
                 125 
                 150 
                 175 
                 200 
               
               
                 B1 
                 150 
                 200 
                 250 
                 300 
                 350 
                 400 
               
               
                 B2 
                 300 
                 400 
                 500 
                 600 
                 700 
                 800 
               
               
                 B5 
                 750 
                 1000 
                 1250 
                 1500 
                 1750 
                 2000 
               
               
                 B10 
                 1500 
                 2000 
                 2500 
                 3000 
                 3500 
                 4000 
               
               
                 B20 
                 3000 
                 4000 
                 5000 
                 6000 
                 7000 
                 8000 
               
               
                   
               
             
          
         
       
     
         [0039]    In fact, the NO consumption will depend on the type of patient, that is to say adult, child or newborn, and also on the ventilation method and on the desired NO dosage. 
         [0040]    Table 3 below gives the volumes of NO necessary for the treatment of an adult patient ventilated with a minute volume of 10 l/min. 
         [0000]    
       
         
               
               
             
               
               
               
               
               
               
             
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 3 
               
             
             
               
                   
                   
               
               
                   
                 Concentration in 
               
               
                   
                 the cylinder (ppm) 
               
             
          
           
               
                   
                 225 
                 450 
                 900 
                 1500 
                 2250 
               
             
          
           
               
                   
                 NO dose (ppm) 
                 vol ml/min 
               
               
                   
                   
               
             
          
           
               
                 Daily 
                 5 
                 327 
                 160 
                 80 
                 48 
                 48 
               
               
                 volume 
                 10 
                 655 
                 320 
                 160 
                 96 
                 96 
               
               
                 (liters) 
                 20 
                 1309 
                 640 
                 320 
                 193 
                 193 
               
               
                 Volume for 
                 5 
                 1309 
                 640 
                 320 
                 193 
                 193 
               
               
                 4 days 
                 10 
                 2618 
                 1280 
                 640 
                 385 
                 385 
               
               
                 (liters) 
                 20 
                 5236 
                 2560 
                 1280 
                 771 
                 771 
               
               
                   
               
             
          
         
       
     
         [0041]    As can be seen in the above table, for a concentration of 450 ppm, a cylinder of B5 type (5 liter equivalent water capacity) containing NO/N 2  packaged at a pressure of 400 bar, therefore providing 2000 liters of gas, makes it possible to treat an adult patient at a dosage of 20 ppmv over a duration of around 3 days. 
         [0042]    Under these same concentration and filling pressure conditions, a daily treatment of this patient is possible with a cylinder of B2 type (25 liter equivalent water capacity). 
         [0043]    In all cases, the weight and space requirement of these cylinders at such a pressure are substantially reduced compared to those of the cylinders of the prior art. It follows therefrom that the combination of a high concentration of NO (i.e. more than 400 ppmv) and a high filling pressure (i.e. more than 250 bar) makes it possible to considerably reduce the size of the packagings and to facilitate the use thereof in a hospital environment. 
         [0044]    This characteristic is even more pronounced in newborns. Thus, table 4 below thus shows the volumes of NO necessary for the treatment of newborns ventilated with a minute volume of 2 l/min. 
         [0000]    
       
         
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 4 
               
             
             
               
                   
                   
               
               
                   
                 Concentration in 
               
               
                   
                 the cylinder (in ppmv) 
               
             
          
           
               
                   
                 225 
                 450 
                 800 
                 900 
                 1500 
                 2250 
               
               
                   
                   
               
             
          
           
               
                 Daily 
                 5 
                 65 
                 32 
                 18 
                 16 
                 10 
                 6 
               
               
                 volume 
                 10 
                 131 
                 65 
                 36 
                 32 
                 19 
                 13 
               
               
                 (liters) 
                 20 
                 262 
                 129 
                 72 
                 64 
                 39 
                 26 
               
               
                 Volume for 
                 5 
                 262 
                 129 
                 72 
                 64 
                 39 
                 26 
               
               
                 4 days 
                 10 
                 524 
                 259 
                 145 
                 129 
                 77 
                 51 
               
               
                 (liters) 
                 20 
                 1047 
                 518 
                 290 
                 257 
                 154 
                 103 
               
               
                   
               
             
          
         
       
     
         [0045]    It is seen that for a concentration of 450 ppm, a cylinder of B1 type (1 liter equivalent water capacity) at 400 bar providing 400 liters of gas makes it possible to treat a newborn at a dosage of 20 ppmv over a duration of 4 days. 
         [0046]    Under these same concentration and filling pressure conditions, a daily treatment of this patient is possible with a cylinder of barely around 250 cm 3 . 
         [0047]    In view of these tables, the advantage of using a cylinder having an internal volume of less than or equal to 12 liters for packaging a mixture of NO and nitrogen at a pressure of at least 250 bar, preferably between 300 and 500 bar, when the NO/N 2  gas mixture contains from 400 ppm to 1000 ppm by volume of NO, and nitrogen for the remainder, is immediately understood. 
         [0048]    Packaging the NO at high pressure, i.e. at least 450 bar, makes it possible to reduce the size of the packaging cylinders used (&lt;12 liters), and therefore to solve the aforementioned overcrowding problems and to make it possible furthermore to adapt the packaging to a daily treatment or treatment per patient in a manner similar to conventional treatments, therefore to enable better monitoring of the treatment received by the patient.