Abstract:
Isolation devices and methods of controlling a partition are disclosed. Devices according to the invention have a housing disposed about a movable partition. The housing has respirator and patient sides on respective first and second sides of the partition. The housing also has: (a) a respirator orifice on the respirator side, adaptable to be in pneumatic communication with a respirator; (b) a patient inspiration orifice on the patient side, adaptable to be in pneumatic communication with a patient; (c) a bias inflow orifice on the patient side, adaptable to be in pneumatic communication with a source of inspiratory gas; and, (d) an expiration return orifice on the patient side. The devices may further include a partition position sensor, a CO2 scrubber, and a controller operable to regulate gas flow to the bias inflow orifice based on partition position.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 60/821,840 filed on Aug. 9, 2006, which is incorporated by reference herein. 
     
     FIELD OF THE INVENTION 
       [0002]    The invention relates generally to respirators, ventilators and oscillators used to deliver inspiratory gas to a patient. The term “respirator” is used herein to refer to respirators, ventilators and oscillators collectively. 
       BACKGROUND 
       [0003]    Rebreathing circuits, such as so called “circle circuits”, are used in operating rooms to conserve volatile anesthetics. There has been a move in the anesthesia field to devices that have low fresh gas flow (“LFGF”) as a cost saving measure designed to reduce the amount of anesthesia used. While beneficial from an efficiency standpoint, some LFGF devices are tedious for the clinician to use because they require frequent attention to the fresh gas flow and manual adjustments of the fresh gas flow to achieve a desired amount of gas in the circuit. 
         [0004]    Some newer anesthesia machines facilitate very low fresh gas flows, and provide nearly closed circuit anesthesia. Examples of these LFGF anesthesia machines are the Physioflex machine offered by Physio, Inc. and the machine described in U.S. Pat. No. 5,094,235. With these LFGF anesthesia machines, the clinician sets the desired oxygen concentration and either the desired inspired or expired anesthetic agent concentration. These LFGF anesthesia machines are not designed to allow precise control of the patient&#39;s ventilation or to facilitate spontaneous breathing, which might be needed in the Intensive Care Unit (“ICU”) setting, since they are not intended to work with the ventilators in common use in the ICU. 
         [0005]    U.S. Pat. No. 6,675,799 (the “&#39;799 Patent”) describes an isolation device having a movable partition and a housing disposed about the movable partition. The isolation device has a movable partition that divides the housing into a patient side and a respirator side. This isolation rebreather uses a partition biaser to help restore the partition that separates patient and ventilator sides of the device toward an equilibrium position. In doing so, the biaser may create a pressure difference between the patient side and the respirator side. This pressure difference may be used to control the flow of bias gas. However, that pressure difference may also distort the pressures applied by the ventilator to the patient, thereby making the device of the &#39;799 Patent unsuitable for all situations. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The nature and objects of the invention will be made clearer with reference to the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0007]      FIG. 1  is a schematic of a device according to the invention; 
           [0008]      FIG. 2  is a top view of an isolation device according to the invention; 
           [0009]      FIG. 3  is a cross-sectional view of the isolation device shown in  FIG. 2  taken along the line  3 - 3 ; 
           [0010]      FIG. 4  is a schematic drawing of an isolation device having a controller according to the invention; 
           [0011]      FIGS. 5A-1 ,  5 A- 2  and  5 A- 3  are each a cross sectional view of an isolation device similar to that shown in  FIG. 3 , but having a partition biaser; 
           [0012]      FIG. 5B  is a cross sectional view similar to that shown in  FIG. 5A-1 , but having a different type of partition biaser; and 
           [0013]      FIG. 6  is a flow chart of a method according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]      FIGS. 1 ,  2 , and  3  illustrate aspects of an isolation device  10  according to the present invention. The isolation device  10  may have a housing  13  disposed about a movable partition  16 . The partition  16  may include an accordion sleeve  19  joined to the housing  13  to allow movement of the partition  16 . The partition  16  may be joined to the housing  13  to separate a patient side  22  of the housing  13  from a respirator side  25  of the housing. The housing  13  also may have a respirator orifice  28  on the respirator side  25  that is adaptable to be in pneumatic communication with a respirator  29 . The housing  13  may also have a patient inspiration orifice  31  on the patient side  22  that is adaptable to be in pneumatic communication with a patient. The housing  13  may have a bias inflow orifice  33  on the patient side  22  that is adaptable to be in pneumatic communication with a source  80  of inspiratory gas, and an expiration return orifice  36  on the patient side  22 . The housing  13  may be made of more than one piece, for example, the patient side  22  may be one piece and the respirator side  25  may be another piece. 
         [0015]    A controller  78  may be provided that is operable to regulate a flow of gas from an inspiratory gas source  80  to the bias inflow orifice  33 . The controller  78  may be operable to achieve a desired flow rate for the flow of gas to the bias inflow orifice  33 .  FIG. 4  illustrates aspects of a controller according to the invention. The controller  78  may include a bias flow line  81  in pneumatic communication with the bias inflow orifice  33 , and a bias flow control valve  84  in the bias flow line  81 . The controller  78  may regulate the flow of gas to the bias inflow orifice  33  based on a position of the partition  16 . The controller  78  may include a position transducer  87  operable to provide a signal corresponding to a position of the partition  16 , and wherein the bias flow control valve  84  is positionable according to the signal. 
         [0016]    A position sensor  100  may be used to detect the position of the partition  16 . As an example, the position sensor  100  may be an ultrasound transducer, which is capable of indicating to the position transducer  87  the position of the partition  16 . As another example, the partition  16  may include a contact and the housing  13  may have a high-position contact and a low-position contact, and then when the partition contact touches the high-position contact, the position transducer  87  may be signaled that the partition  16  is at the high position, and when the partition contact touches the low-position contact, the position transducer  87  may be signaled that the partition  16  is at the low position. Other types of position sensors  100  are well known, and could easily be employed as a position sensor  100 . 
         [0017]    In an embodiment of an isolation device  10  according to the invention, the housing  13  may have a bias release orifice  69  on the patient side  22 , a release line  72  joined to the bias release orifice  69  and a release valve  75 . The release valve  75  may be operable to allow gas to flow from the bias release orifice  69  to the atmosphere via the release line  72 , for example by opening a gate in the release valve  75 . The release valve  75  may be operable by the controller  78  to allow gas to flow from the bias release orifice  69  to the atmosphere when the partition  16  is too far to the respirator side  25 . Furthermore, the release valve  75  may be operable to allow gas to flow from the bias release orifice  69  to the atmosphere during an expiration period. 
         [0018]      FIGS. 5A-1 ,  5 A- 2 ,  5 A- 3  and  5 B illustrate embodiments of the invention which include a partition biaser  39  joined to the partition  16 . The partition biaser  39  may be operable to bias the partition  16  to an undisplaced position during an expiration period. One such partition biaser  39  may have a movable rod  42  joined to the partition  16 , and a spring  48  joined to the rod  42  to provide a force that biases the partition  16  to the undisplaced position.  FIGS. 5A-1 ,  5 A- 2  and  5 A- 3  show such a partition biaser  39 .  FIG. 5B  shows an embodiment with a different type of partition biaser  39 , which has a solenoid  51  that may be used to provide the bias force. The solenoid  51  may be magnetically coupled to the rod  42 . An abutment  45  may be provided to limit the travel of the rod  42 , and therefore the partition  16 . 
         [0019]      FIGS. 5A-1 ,  5 A- 2  and  5 B show embodiments in which the release line  72  includes a conduit  106  joining the patient side  22  with the respirator side  25 . The conduit  106  may allow the patient side  22  to be at a pressure that is not significantly above the pressure on the respirator side  25 . For example, when the partition biaser  39  moves the partition  16  toward the patient side  22 , gas may be allowed to flow via the conduit  106  to the respirator side  25 . In this manner, the pressure on the patient side  22  will not change much as a result of the partition biaser  39  moving the partition  16 . A check valve  76  may be included to prevent gas flow from the respirator side  25  via the conduit  106 . 
         [0020]    The release valve  75  may be operable to open when the pressure on the patient side  22  is higher than the pressure on the respirator side  25 .  FIGS. 5A-1 ,  5 A- 3  and  5 B show embodiments of such a device. One means of making this occur would use a pressure transducer  103  that is in communication with the release valve  75  for purposes of signaling to the release valve  75  when the release valve  75  should be open in order to reduce the pressure on the patient side  22 . This operability may be in addition to that described above for controlling the position of the partition  16 . As such, it may be beneficial for the signal from the position sensor  100  and the signal from the pressure transducer  103  to be sent to a microprocessor  109 , which would then determine whether the release valve  75  should be open or closed.  FIGS. 5A-1 ,  5 A- 3  and  5 B show embodiments having a microprocessor  109 . It should be noted that the embodiments depicted in  5 A- 2  and  5 A- 3  may use the partition biaser  39  shown in FIG.  5 B—for brevity, figures corresponding to such embodiments have not been included in this application. 
         [0021]    An isolation device  10  according to the invention may have a CO 2  scrubber  54  having an inlet  57  in pneumatic communication with the patient and an outlet  60  in pneumatic communication with the expiration return orifice  36 . A check valve  63  may be provided in pneumatic communication with the scrubber  54  to prevent gas from traveling from the scrubber  54  toward the patient and to permit exhaled gas from the patient to flow through the scrubber  54 . A check valve  66  may be provided in pneumatic communication with the patient inspiration orifice  31  to encourage exhaled gas from the patient to flow through the scrubber  54  and to permit gas from the patient inspiration orifice  31  to flow to the patient. 
         [0022]    The bias inflow orifice  33  may be used to supply inspiratory gas from the inspiratory gas source  80  to the patient side  22  of the housing  13 . A vaporizer, blender, mixer and/or nebulizer (shown as  99  in  FIG. 1 ) may be placed in pneumatic communication with the bias inflow orifice  33 , and these may be used to provide a therapeutic agent in the inspiratory gas. 
         [0023]      FIG. 6  shows a method according to the invention. A method according to the invention may include providing  200  an isolation device having a partition, and having a bias inflow orifice on a patient side of the partition. Inspiratory gas may be provided  203  to the bias inflow orifice, and a position of the partition may be monitored  206 . When the partition is not in a desired position, the partition may be moved  209  to a desired position by increasing or decreasing the flow of inspiratory gas into the patient side of the housing and/or by increasing or decreasing the flow of gas leaving the patient side of the housing. The inspiratory gas may include a therapeutic agent. 
         [0024]    The partition may be used to deliver the inspiratory gas to a patient. To do so, the partition may be moved in order to cause the inspiratory gas to leave the patient side via a patient inspiration orifice. Moving the partition in order to deliver gas to a patient may be accomplished by increasing a pressure in the respirator side. A respirator may be provided in pneumatic communication with a respirator orifice of the housing, and the respirator may be used to increase the pressure in the respirator side during inspiration. 
         [0025]    The partition may also be moved, for example, by a partition biaser. In one method according to the invention, the partition is moved by the partition biaser prior to increasing the pressure with the respirator, so that the partition seeks an undisplaced position during expiration. This may cause gas to move from the patient side to the respirator side via a release line, or it may create a pressure difference between the respirator side and the patient side that may result in an increase in bias inflow to the patient side. 
         [0026]    A method according to the invention may include moving the partition to allow expired gas from the patient to flow through the scrubber toward the expiration return orifice. This may be accomplished by decreasing a pressure on the respirator side. A respirator may be provided in pneumatic communication with the respirator orifice to decrease the pressure in the respirator side during expiration. 
         [0027]    A method according to the invention may include providing a release line joined to the bias release orifice, and a release valve operable to allow gas to flow from the bias release orifice to the atmosphere via the release line, and the method may further include opening the release valve to move the partition toward the patient side. 
         [0028]    Thus, it is seen that the objects of the present invention are efficiently obtained, although modifications and changes to the invention should be readily apparent to those having ordinary skill in the art, which modifications are intended to be within the spirit and scope of the invention as claimed. It also is understood that the foregoing description is illustrative of the present invention and should not be considered as limiting. Therefore, other embodiments of the present invention are possible without departing from the spirit and scope of the present invention.