Abstract:
A low cost suction regulator is disclosed in conjunction with a fluid drainage system that includes a suction chamber and a collection chamber. The suction regulator is comprised of an atmospheric chamber and a suction chamber separated by a divider. An opening in the divider has a variably biased closing member associated therewith for opening or closing the opening according to operator selected pressure differentials between the chambers. The closing member is movable along an axis that differs from the direction of airflow, thus eliminating the need for damping the forces applied to the closing member. The dividing means and its closing member will operate over the full range of angles from the vertical to horizontal axis. One embodiment of the drainage system further includes devices for measuring patient airflow, patient negativity and imposed suction. Measurement of these variables is effectively implemented with diaphragms or bellows having dials or other types of marker connected thereto such that movement of the diaphragm or bellows results in movement of the dial or marker to thereby indicate the value of the above noted variables.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application claims priority of U.S. Provisional Application No. 60/306,024, filed Jul. 17, 2001, under Title 35, United States Code, Section 119(e). 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to fluid pressure regulating systems, such as systems for regulating the pressure of gas. The invention further relates to controlling the pressure of suction flow lines and suction chambers, and in particular as applied to wound drainage systems, for draining fluids from medical patients, such as from the chest cavity, by means of gas pressure differentials using low pressure gas systems. 
   2. Description of the Prior Art 
   In many situations involving gases, it is important, and often mandatory, to measure and regulate the pressure of the gas. In one important example, there exists in hospitals a system for distributing vacuum or suction from a central vacuum supply system, which in many cases must be monitored and regulated when it is used. These systems are used, for example, in conjunction with wound drainage devices, where fluids, such as blood and water, and gas from a wound in a patient&#39;s pleural cavity are withdrawn using a pressure differential established between a controlled suction chamber and the internal pressure in the patient. Such suction pressure and pressure differentials must be closely controlled because of the dangerous conditions which could result if unduly high or low pressure differentials should occur. In this application, as in many other pressure measuring and regulating applications, it is desirable to incorporate a pressure regulating device which is compact, which makes the pressure measurement and regulation with accuracy, which is capable of functioning reliably for long periods of time, and which is economical to manufacture. 
   A particularly advantageous system is disclosed in U.S. Pat. Nos. 4,698,060, 4,715,855 and 4,889,531, which are incorporated herein by reference, as well as PCT publication number WO 00/78373 A2, each of which discloses a pressure regulator and a fluid drainage system. The pressure regulator includes high and low pressure chambers separated by a divider having an opening, a closing member biased to a closing position for closing the opening with a biasing force according to a desired pressure differential between the chambers, and a damping device for damping the resulting force, and movement, on the closing member. The fluid drainage system has a suction chamber with a suction regulator and various arrangements of diaphragms for measuring pressure differentials. As economical as these systems are, they do incorporate the relatively expensive damping device, such as a dashpot, for effectively damping the force applied by the closing member in order to prevent undesirable vibration at the transition point. 
   U.S. Pat. No. 3,830,238, illustrates movement of a bellows assembly to detect and display the value of negativity within the pleural cavity while U.S. Pat. No. 4,468,226 discloses a bellows device which contracts as suction increases in a collection chamber. An indicator vane, connected to the bellows, moves along a fixed scale to indicate the level of suction within the collection chamber. While both of these disclosures are directed to chest drainage devices, neither of them is used to control the level of suction or negativity in the system. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to provide an improved device for regulating the pressure of a gas in one space relative to the pressure of a gas in another space which is in communication with the first space. 
   Another objective is to accurately regulate a selectively variable pressure to a suction chamber relative to the atmosphere by means of an economical yet effective device. 
   A further object of the present invention is to provide an improved gas pressure regulating device including an opening through which high pressure air can flow from a first space to a second space having a lower pressure, and a means for selectively closing the opening in a smooth manner without the use of a damper for controlling the effect of force, and the tendency of surface contact vibration, on the device for closing the opening. 
   It is still another object of the present invention to provide an improved chest drainage system for regulating the suction pressure in an accurate and efficient way using economical components. 
   Yet another important objective of the present invention is to provide a suction chamber that will preferentially draw air from a patient air leak in the chest cavity before drawing additional air from the atmosphere in order to satisfy the total volume of air needed to maintain the selected value of pressure in the suction chamber. 
   Still yet another object of the present invention is to provide an improved gas pressure regulating device and chest drainage system in a more economical manner. 
   These and other objects will occur to those skilled in the art from the description to follow. 
   The foregoing objects are achieved according to a preferred embodiment of the invention by means of a system having a first chamber or atmospheric chamber with access to the atmosphere and a second chamber or suction chamber in communication with a suction line, the system having two active members. The first chamber is under atmospheric pressure and the second chamber communicates with the airflow and pressure associated with a patient. The device controls access of the second chamber to the atmosphere to thereby regulate the pressure in the second chamber which is communicating with the suction line. The first of the active members for controlling access to the atmosphere is a movable member or closure, preferably a sliding door structure, which is captured by a capturing, guiding or holding device such as rails or brackets, and is movable to open or close an air or other gas path between the second chamber and the first chamber (“the thru-put path”). Movement of the sliding door is provoked with the deflection of the second of the active members which is a pressure sensitive device or pressure sensor, such as a pressure sensitive diaphragm, bellows, balloon, or the like. The sliding door is preferably very light in weight in order to reduce its drag while moving under the influence of changes in suction. The diaphragm is under the influence of a biasing force, and can be biased by means of a spring, which can be either a tension spring or a compression spring, whose setting is preferably adjusted by a pressure regulating apparatus according to the desired pressure applied to the patient. The pressure regulating apparatus advantageously has a setting member, such as a threaded shaft, for cooperating with the pressure sensitive device (or pressure sensor) for controlling the biasing force, and for assisting in indicating the desired suction pressure as well as the actual suction pressure. The sliding door, or other movable member used for sealing or otherwise controlling the opening, is advantageously mounted for low friction movement in response to diaphragm, bellows, balloon or other movement under the influence of the pressure differential between the first and second chambers. While the preferred embodiments illustrate the axis for door movement being perpendicular to the axis of atmospheric airflow through the divider, any angle will be free of surface contact vibration so long as the opening at the transition point is a captured sliding movement as opposed to the method for opening and closing the thru-put path disclosed in the prior art. Finally, the description of the invention has been described with the closing member being movable in an axis parallel with the dividing member; however, the control surfaces need not be flat, but could also be non-flat surfaces such as cylindrical or spherical members that rotate with respect to each other to open and close the thru-put path. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic front view of the suction regulator according to the prior art system included herein by reference. 
       FIG. 2  is a schematic front view of the suction regulator according to a preferred embodiment of the present invention showing a convoluted diaphragm and movable door for controlling suction, a calibrated scale for setting the suction, and a second calibrated scale showing the imposed, or actual value of suction, all of which are incorporated in a fluid drainage system according to the invention. 
       FIG. 3  illustrates an embodiment of the invention in schematic form for controlling suction with a pressure sensitive convoluted diaphragm and movable door in an axis perpendicular to that of  FIG. 2  as well as a bellows activated reading of imposed suction. 
       FIG. 4  illustrates an embodiment of the invention also in schematic form for controlling suction with a pressure sensitive convoluted diaphragm and movable door on the same axis as well as a bellows activated reading of imposed suction in an axis perpendicular to that of  FIG. 3 . 
       FIG. 5  is an end view cross section somewhere along the opening for admitting atmospheric air in the embodiments of  FIGS. 2  thru  4  and illustrates three possible structures for capturing the sliding door in order to prevent its movement away from the dividing member, shown as  FIGS. 5A ,  5 B and  5 C. 
       FIG. 6  is a schematic front view of an embodiment for controlling suction using a compression spring and a rotating cam for exerting the variable control force on the spring and sliding member. 
       FIG. 7  is a schematic front view of a portion of  FIG. 3  illustrating the suction regulator performing as a stand-alone device according to the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The figures and description to follow are primarily intended to illustrate the concept for a new, simplified, and more economical suction regulator, and in particular, for its use as a source of dry suction in a chest drainage device.  FIG. 1  is a drawing taken from the prior art patents discussed above and included herein for reference, and provides a view of the earlier dry regulator for easy comparison to the present disclosure herein. It is noted that  FIG. 1 , and all the figures to follow, show a single chamber for the collection of fluids; however, the collection chamber is typically divided into smaller sections for better resolution when reading the value of fluid collected, wherein each of the collection chamber sections can be provided with anti-spill over capability between compartments as the volume collected increases. One such anti-spill over device is that disclosed in U.S. Pat. No. 4,902,284, included herein by reference. Further, the drawings are not shown in the correct perspective so far as the calibrated scale and pointer movement are concerned, for example, threaded rod  157  (discussed in detail below) in  FIG. 2  has a very narrow waist  101  at the point where a tension spring  102  is connected so that rotation of adjustment knob  158  will only increase spring tension by a small amount, while at the same time, moving pointer  108  a large distance on a wider diameter portion of shaft or rod  157  as pointer  108  traverses calibrated scale  110 , therein providing a display for the selected value of suction. That is, large movements on pointer  108  will only cause small movement on a tension spring  102 . In addition, these figures do not include a detailed description of the usual components for patient air leak, patient negativity, anti-spill device and protection against reverse pressure to the patient; these components could advantageously be included in the system and are shown, for example, in U.S. Pat. Nos. 4,698,060, 4,715,855 and 4,889,531, which, as indicated above, are incorporated herein by reference. 
   Referring to  FIG. 1 , a wound drainage system  10  according to the prior art is disclosed comprising a suction compartment or chamber  3  from which air can be evacuated by an external vacuum source such as a centrally located vacuum pump in a hospital, a suction port  4  for interconnecting chamber  3  with the external vacuum source, a suction regulator  5  for controlling the pressure in chamber  3 , a suction measuring device  6 , a collection chamber  7  for collecting fluids withdrawn from a patient, and an inlet port  9  for connecting compartment or chamber  7  to the patient. A one-way patient airflow flap valve  11  mounted on a hinge  13  separates suction chamber  3  and collection chamber  7 . Air evacuated from a patient through inlet port  9  passes through port  15  whenever the pressure in chamber  7  exceeds that in chamber  3 , and the extent of that airflow is reflected by the amount flap valve  11  opens. Valve  11  is configured to close and seal port  15  when the pressure in suction chamber  3  exceeds that in collection chamber  7 . A dial  17  mounted on a pivot  19  and movable by a push rod  18  attached to flap valve  11  cooperates with a calibrated scale  21  to indicate the patient airflow rate (generally in liters per minute) through port  15  according to the extent valve  11  opens. When it is a pleural chest cavity being drained, the patient airflow is usually the result of air flowing through a hole in the patient&#39;s lung into chamber  7 . Suction chamber  3  communicates with suction regulator  5  via a passage  77 . 
   Occasionally, as when a hole in the patient&#39;s lung closes during the drainage process, chamber  7  develops a pressure even more negative than the control suction of suction chamber  3 , and flap valve  11  locks shut to isolate the two chambers from each other, to therein prevent the dangerous possibility of reverse air flow into the patient. A patient negativity measuring device  23  is provided to indicate the extent of the negativity. Device  23  includes a patient negativity diaphragm  25  extending over an opening in the outer wall of chamber  7 , a push rod  26  attached to diaphragm  25  and a dial  27  mounted on a pivot  29  movable by push rod  26  for cooperating with an appropriately calibrated scale  31 . When the atmospheric pressure outside of chamber  7  exceeds the air pressure in chamber  7 , diaphragm  25  flexes inwardly rotating dial  27  clockwise according to the amount the diaphragm flexes to therein measure and indicate the extent of patient negativity. The pivot point  29  of dial  27 , or the connection point to push rod  26 , can be equipped with a spring to urge the dial back to its zero position when the pressure differential gets smaller. 
   Suction regulator  5  for performing the functions of regulation and measurement of the suction in chamber  3  is shown in  FIG. 1 . Suction regular  5  includes a wall  41 ; a partition  43  dividing regulator  5  into an upper chamber  45  and a lower chamber  47 ; an opening  49  in partition  43 ; a light ball  53  whose diameter is slightly more than the diameter of the opening  49 ; a cantilever support arm  55  having a threaded bore through which extends a threaded bolt  57  with an adjustment knob  58  (which could have detents to avoid accidental changes) and disposed on a support shelf  59 ; a spring  61  attached at one end to ball  53  and at its other end to support arm  55  for biasing ball  53  upwardly; and a dashpot  65  composed of a piston  67  attached to ball  53  and a cylinder  69  receiving the piston in sliding engagement and mounted on a support block  71 . A piston chamber (not shown) is defined between the head of piston  67  and the closed bore of cylinder  69 . Atmospheric airflow at pressure P A  enters chamber  45  through an entrance port  75 . Lower chamber  47  communicates with suction chamber  3  through a passage  77  placing both  47  and  3  at subatmospheric pressure by virtue of the connection to a hospital suction source P S  at access port  4 . In normal operation, the pressure in collection chamber  7  is quite close to the value of subatmospheric pressure in suction chamber  3 , differing only by the pressure drop caused by the flow of air coming from the patient. As explained above, chamber  7  will only be at a lower pressure than chamber  3  if patient negativity is greater than the suction found in chamber  3 . 
   Herein, a fluid drainage system  100  according to an embodiment of the invention is shown in  FIG. 2  and represents a modified version of  FIG. 1  showing the improved suction regulator controlling the input flow of atmospheric air without any type of damping device as disclosed in the prior art systems. 
   Referring to  FIG. 2 , fluid drainage system  100  includes a suction compartment or chamber  103 , a suction regulator  105  and a fluid collection compartment or chamber  107 . Suction regulator  105  has a port  175  open to the atmosphere at atmospheric pressure P A . Suction chamber  103  has a port or opening  104  for connection to a suction source at a pressure P S , a suction measuring device  106 , and a patient airflow rate gauge composed of pointer  117  pivotal on a hinge  119  from a push rod  118  for movement across a calibrated scale  121 . Collection chamber  107  includes a patient negativity device  123  for measuring the pressure in a patient and will only measure a value of suction or negativity greater than that found in suction chamber  103  if the hole in the patient&#39;s lung has closed. The components of fluid drainage system  100  in  FIG. 2  have components identical or similar to the same numbered components in the prior art system  10  of  FIG. 1 , and in most cases, bearing the same numerical identifiers as those of  FIG. 1  but in the 100&#39;s scale in  FIG. 2 . 
   Thus, suction chamber  103 , with its suction measuring device having a dial scale and pointer  106 , patient airflow flap valve  111  mounted on hinge  114  across airflow port  115  between collection chamber  107  and suction chamber  103  are all like the corresponding parts of  FIG. 1 . Suction port  104  is like port  4  in  FIG. 1 . Collection chamber  107  with patient negativity device  123  having a push rod  126  extending from a patient negativity diaphragm  125  for moving dial  127  across scale  131  are also like the corresponding parts in  FIG. 1 . With reference to suction regulator  105 , wall  141 , cantilever support arm or pointer  108  with threaded bolt  157  and adjustment knob  158  disposed on support shelf  159  are all similar to corresponding parts of  FIG. 1 , namely to wall  41 , support arm  55  with bolt  57 , and knob  58  on shelf  59  as is atmospheric air entrance port  175 . However, there are significant improvements in the suction regulator  105  in the present invention as discussed below. 
   Suction regulator  105  has threaded bolt  157  with waist  101  as described above, which has pointer  108  operatively arranged relative to a scale  110  for indicating suction settings in terms minus centimeters of water (−cmH 2 O). A generally horizontal wall or dividing member  143  (although it need not be horizontal as discussed below) extends across suction regulator  105  between wall  141  and a wall  116 . An opening or air flow port  113 , defined by surfaces having a contour (which can be flat or not flat), extends through wall  143 , and a slide or thru-put door  120  connected to spring  102  moves over opening  113 . A convoluted diaphragm  122  extends across an opening  137  in wall  116 , and a connecting member  132  interconnects diaphragm  122  and door  120 . Another opening  136  through wall  116  provides a path for any atmospheric air that comes through opening  113 , and after which it flows into the suction source P S  through opening  104  in suction chamber  103 , all of which serve to provide the desired control of suction in chamber  103 . 
   Scale  110  is an indicator for setting the selected value of suction in suction chamber  103 , and dial scale and pointer  106  will show the actual, measured value for the imposed suction and may or may not be used in a typical chest drainage system. System  100  thus includes suction regulator  105 , wall  116  separating the system into an atmospheric chamber  112  and low-pressure or suction chamber  103 , and air pressure controlling apparatus, such as a convoluted diaphragm  122 , and three airflow ports  175 ,  104  and a port  109 . It is of course appreciated that convoluted diaphragm  122  can be replaced with a standard diaphragm, a bellows or any other type of comparable regulating apparatus conventional in the art that is able to move with a change in fluid pressure. Port  175  provides chamber  112  of suction regulator  105  with access to air at atmospheric pressure P A  or P atm , second port  104  provides access to a suction line (as is common in hospitals) having a pressure P S  or P suction , and third port  109  connected to fluid collection chamber  107  provides access to a patient&#39;s chest cavity P patient  and any airflow or fluids that must be extracted by virtue of the suction pressure provided by suction chamber  103 . As explained above, thru-put door  120  is connected to convoluted diaphragm  122  by means of a connecting member  132 , which can be any such member that is conventional in the art, such as a very thin lightweight rod or even a section of string. Door  120  regulates the flow of atmospheric air according to its position covering opening or flow port  113 . 
   As noted earlier, door  120  is under the bias of tension spring  102 , which is connected to a regulating apparatus, such as a spring regulator  125 , and which in turn is adjustable so that the tension of spring  102  can be varied. Spring regulator  133  can be a calibrated, detented dial, or smoothly varying dial setting, or adjustment knob  158  (mentioned above) for varying the tension of spring  102 . Support pads  130  forming part of wall  143  provide the supporting surface for the movement of door  120 . The engaging surfaces of support pads  130  and door  120  can be provided with a coating for reducing friction, such as Teflon or any other comparable friction reducing material. Ball or other bearings can support door  120  on pads  130 . The variable opening of door  120  as described will control the flow of atmospheric air as needed to maintain a selected level of pressure, i.e., suction, in the control space or suction chamber  103 . 
   The setting on spring regulator  133  is accomplished by instruction to the user in accordance with calibrated scale  110  shown on the face in  FIG. 2 . The tension on spring  102 , and therefore the suction setting, is accomplished through connecting member  132  connected to the door on one side and on the other side, to a secure surface on the center of diaphragm  122 . The other side of the door is connected to spring  102 , the other side of which is connected to threaded shaft  157  which rotates with the rotation of adjustment knob  158 . The value of the desired suction is indicated by the position of threaded pointer  108  as it moves up and down on threaded shaft  157 . Pointer  108  in this figure, and other members connected to rotating shafts throughout, will all be held from rotation themselves by having one end ride in a slot  128  such as that provided by a guide member  129 . The value of the suction pressure in chamber  103  provides one force on diaphragm  122 , and the force of spring  102  puts an opposing force on diaphragm  122 . The greater the force applied by spring  102  on diaphragm  122 , the greater the amount of suction required to move diaphragm  122  to the right in  FIG. 2 , and therefore, to increase the opening of door  120 . The opening and closing movement of door  120  is shown schematically by arrow A. 
     FIG. 3  is a variation of  FIG. 2  with the opening and movable door  220  oriented in the vertical axis. The fluid drainage system is shown as item  200 . Many components are essentially the same, and are shown with the same numerals as those in  FIG. 2 , but in most instances under the  200  series (member  157  of  FIG. 2  becomes  257  in  FIG. 3 ) where the components are identical or similar to those of  FIG. 2 . Reference can be made to the earlier discussion with respect to those components. However, two differences are noted. First, a bellows  250 , with a pointer  252 , will move pointer  252  across a calibrated scale  254  as an indicator of the actual suction in chamber  203 , bellows  250  being connected across an opening  237  in wall  216 . Bellows  250  will ride on a set of rollers or a lubricious surface  256  on a platform  258  as it moves with changes in suction. Platform  258  is needed because bellows  250  is generally pliable for easy movement, and will sag if used in the horizontal axis without support. (It should be appreciated that bellows  250  and scale  254  can easily be oriented in the vertical axis as shown in  FIG. 4  as items  350  and  352 , in which case a platform is not needed since the light weight needle will be located at the bottom of the hanging bellows.). The second significant difference shows shaft  257  with two movable members  243  and  245  rather than just pointer  108  as in  FIG. 2 . Pointer  243  is located on a part of shaft  257  with coarse threads  281  so that small amounts of rotation on shaft  257  will cause large distances of travel for pointer  243 . By the same token, member  245  to which spring  277  is attached, is located on a part of shaft  257  with very fine threads  282  to therefore cause small changes in spring tension as shaft  257  is rotated. This represents a variation of the two diameters on shaft  157  as shown in  FIG. 2 . 
     FIG. 4  is a variation of  FIGS. 2 and 3 , and like parts are in most cases given the same numbers as those in  FIG. 3  but under the  300  series. In  FIG. 4 , a door  320  moves across an opening  313 . Door  320  and opening  313  have parallel axes, which in  FIG. 4 , as in  FIG. 3 , are vertical. While shown on the vertical axis, the same could be accomplished on any axis of choice. All components are essentially the same. However, in the case of  FIG. 4 , a member  379 , which in the embodiment shown is flexible, connects a convoluted diaphragm  317  to door  320 , and in so doing, passes over a roller  387 , which translates the left right movement of diaphragm  317  to a corresponding vertical movement on door  320 , therein controlling the opening and closing of thru-put path  313  between the atmosphere and suction chamber  303 . As in  FIG. 3 , a bellows  350  will move its pointer  352  across calibrated scale  335  as an indicator of the actual suction in chamber  303 ; however, in this case, bellows  350  is hanging in the vertical axis thus avoiding the use of a supporting platform. Also as in  FIG. 3 , shaft  357  has two movable members  343 ,  345  rather than just one, but in this case, the coarse and fine threads  381 ,  382  are reversed because the functions of the respective arms  343 ,  345  are reversed. Having both active members  320 ,  317  on the same plane will serve to reduce the overall size of the unit. 
   Although the apparatus for moving door  120 ,  220 , or  320  have been described as a convoluted or standard diaphragm in  FIGS. 2 ,  3  and  4 , it could also be a bellows or some other comparable device that is able to move with the change of fluid pressure, the amounts being commensurate with the pressures involved for any particular situation. 
     FIG. 5  illustrates several methods for capturing a movable door  420 , i.e. one corresponding in purpose to doors  120 ,  220  or  320 .  FIG. 5A  shows an assembly provided with guide rails  483  extending from a pair of support pieces  484  (which surfaces define the opening for path  413 ) to prevent the movement of door  420  away from thru-put path  413 , while still being able to slide back and forth to facilitate a change in thru-put path  413  as the demand on suction changes. 
   Rails  483  are shown as dove tail rails, and correspondingly shaped grooves  485  in door  420  enabling the sliding motion without the separation of door  420  from support pieces  484 . 
     FIG. 5B  provides brackets  487  extending from support pieces  488  for capturing door  420 ′. Brackets  487  each are attached to support piece  488  by an appropriate connector of a foot portion  489  to support piece  488 , and a flange  490  extends from a leg  491  to overlap door  420 ′. 
   Referring to  FIG. 5C , this figure, shows a door  420 ″ with slots  492  running along each of the opposite edges of door  420 ″, into which extend the bent-over longitudinal rims  493  of guide members  495 . Members  495  have legs  496  extending from foot portions  497 . 
   As described above, doors  420 ,  420 ′ and  420 ″ can ride on a coating of lubricious material such as Teflon. Alternatively, but not shown, the door can advantageously ride on ball bearings to further decrease the effect of frictional drag when the members are pressed together as a function of the differential pressure. A layer of felt, or the like, can be placed between the surfaces to further assist the seal so as to restrict the flow of air to the designated opening. 
   A variation of  FIGS. 2 ,  3  and  4  is shown in  FIG. 6 ; however, it will work in the same manner. All components are also essentially the same, and those with the same general structure are shown with numerals in most cases increased by 200 from those of  FIG. 4 . 
   In  FIG. 6 , a suction chamber  503 , suction regulator  505  and collection chamber  507  are present as in the other embodiments, connected respectfully to a suction source through port  504 , the atmosphere through port  575  and the patient&#39;s chest cavity through port  509 . Suction chamber  503  has a patient air-flow rate indicator having dial  517  movable across scale  521 , and a one-way valve  511  pivotal on a hinge  514  for closing port  515  to collection chamber  507  when the pressure in suction chamber  503  exceeds that of collection chamber  507 . A patient negativity measuring device  523  with dial  527  movable across scale  531  by means of the movement of a patient negativity diaphragm  525  extending across an opening in a wall of collection chamber  507  on the other side of which is the atmosphere. Tension springs  102 ,  277  and  377  of  FIGS. 2–4  are replaced by a compression spring  577  in  FIG. 6 . A support tube  580  prevents spring  577  from sagging and spring  577  is variably compressed with a cam  598  as a shaft  557  rotates with the turning of an adjustment knob  558 . As the diameter of cam  598  changes, so will the compression on spring  577 . The greater the compression force of spring  577 , the more suction required to enable the flexing of a convoluted diaphragm  518 . Adjustment knob  558  advantageously has a sealing member to prevent atmospheric air from leaking into suction chamber  503 . Sealing adjustment member  558  will serve to maintain the preferential flow feature. (Preferential flow means that the suction chamber first draws whatever air is necessary to achieve a desired suction pressure from the patient through the collection chamber, and only if that air does not provide the necessary suction pressure, is atmospheric air drawn from the suction regulator.). The preferential feature is also found in U.S. Pat. No. 4,889,531. As with  FIGS. 2–4 , the movement of adjustment shaft  557  must provide greater movement to pointer  543  than it does to the changes on spring  577 . In this case, reduced spring movement is provided by a gear reduction coupling  599  located along shaft  557 , wherein, several rotations of the adjustment rod  557  will only produce a single rotation of cam  598  as it varies system suction from its minimum to maximum values. The system of  FIG. 6  will also allow for a smaller overall device because of the spring being located in the suction chamber. 
   Referring to the other aspects of the embodiment shown in  FIG. 6 , a bellows  550  moves, according to the suction imposed, through an opening in a wall  516  between suction chamber  503  and suction regulator  505  to move a pointer  552  across calibrated scale  554 . Scale  554  is calibrated as minus centimeter water (−cmH 2 O) to show the amount of imposed suction. Air enters suction regulator  505  through a port  575 . A door  520  is attached to a convoluted diaphragm  518  for movement across opening  513  defined by platforms  530 . 
   An important aspect in this type of system is that the opening member, while not mandatory, provides the most convenient structure when perpendicular to the flow of atmospheric air. However, any angle with respect to airflow will prevent the surface contact vibration which occurs with the “poppet” or “ball and socket” system for opening and closing of the thru-put path of the prior art (i.e., which are oriented in the line of fluid flow), so long as the door is free to slide along the surface containing the opening. This invention meets this objective because the force vector from atmospheric pressure and the resulting airflow will serve to force door ( 120 ,  220 ,  320 ) ( FIGS. 2–4 ) or ( 520 ) ( FIG. 6 ) more or less firmly against support ( 130 ,  230 ,  330 ) ( FIGS. 2–4 ) or  530  ( FIG. 6 ). However, since door ( 120 ,  220 ,  320 ,  520 ) cannot move up and down in the vertical axis as shown in greater detail in the  FIG. 5  ( 420 ,  420 ′,  420 ″), it will not experience surface contact vibration even though a damping device is not involved. 
   In operation, a patient is hooked up to air and fluid input port ( 109 ,  209 ,  309 ,  509 ) ( FIGS. 2–4 ,  6 ). Port ( 104 ,  204 ,  304 ,  504 ) ( FIGS. 2–4 ,  6 ) is connected to a suction line, and port ( 175 ,  275 ,  375 ,  575 ) ( FIGS. 2–4 ,  6 ) is open to the external atmosphere. Spring ( 102 ,  277 .  377 ,  577 ) ( FIGS. 2–4 ,  6 ) is set by spring regulator ( 101 ,  245 ,  343 ,  598 ) (FIGS.  2 – 4 , 6 ) to establish the desired pressure differential. As the pressure across diaphragm ( 122 ,  218 ,  317 ,  518 ) ( FIGS. 2–4 ,  6 ) varies because of pressure differential by the air in chambers ( 103 ,  203 ,  303 ,  503 ) ( FIGS. 2–4 ,  6 ), and that of spring ( 102 ,  277 ,  377 ,  577 ) ( FIGS. 2–4 ,  6 ), diaphragm ( 122 ,  218 ,  317  or  518 ) ( FIGS. 2–4 ,  6 ) moves to a dotted line position as shown in  FIG. 2  to move door ( 120 ,  220 ,  320 ,  520 ) ( FIGS. 2–4 ,  6 ). This regulates the flow of atmospheric air from chamber ( 112 ,  205 ,  305 ,  505 ) ( FIGS. 2–4 ,  6 ) to chamber ( 103 ,  203 ,  303 ,  503 ) ( FIGS. 2–4 ,  6 ) and thus controls the pressure on the chest cavity and the resulting flow of air from the patient if an air leak is present. This suction pressure will also serve to drain fluids from the patient&#39;s chest cavity, or to re-inflate a collapsed lung, even in the absence of an air leak of any kind. 
     FIG. 7  illustrates the suction regulator as a stand-alone device. While the stand-alone regulator could have been taken from any of the figures describing the suction regulator,  FIG. 7  is generally the format shown in  FIG. 3 , and uses the same numbers therein to describe its operation, but only with a prime (′) sign. The stand-alone embodiment has particular utility in hospitals with committed thoracic and/or cardiac units where virtually all patients will require a chest drainage device following their surgical procedures. In such cases, an inexpensive, permanently installed, stand-alone regulator  200 ′ is attached to the suction source of every bed with an appropriate plumbing connection  600 . The health care workers can then use a far less expensive drainage device by using port  602  to connect a unit having the collection chamber and one-way valve for patient airflow, but which does not require the function normally included for suction control. This procedure provides greater economy to the healthcare facility. 
   While the doors described above have been found most useful for covering the opening between the suction regulator and the suction chamber, there are many other devices available. These include a pair of movable members defining a variable opening between them, devices on the order of diaphragm leaves such as those found in certain camera systems and slidable over each other to vary the size of the opening and the like. 
   Finally, while all of the atmospheric air thru-put openings ( 113 ,  213 ,  313 ,  413 ,  513  and  213 ′) in  FIGS. 2–7  are rectangular in shape, it is appreciated that any thru-put geometry may be used, and in some cases quite advantageously. For example, circular, oval, triangular or other forms of thru-put opening are applicable, and decisions about which to use will often depend on other device parameters such as the spring constant, which is sometimes dictated by space constraints. External conditions may also play a part, one example being suction systems that are subject to wide ranges of demand on source suction. Characteristics of this type may be more effectively dealt with if the atmospheric air thru-put path is selected accordingly. Device requirements and/or conditions of use other than those mentioned, may dictate the design parameters and techniques selected. 
   This is an extremely simple device, and the fact that a dashpot or other damper is not required makes this an extremely efficient yet economical apparatus. It can be produced in large quantities for commercial use, yet is surprisingly inexpensive. 
   The invention has been described in detail with particular emphasis on the preferred embodiments, but variations and modifications within the spirit and scope of the invention may occur to those skilled in the art to which the invention pertains.