Automatic Control System For Radioactive Regional Ventilation Studies

Abstract

A system for obtaining a permanent visual record of the air passages of the lungs by the introduction of a measured quantity of air mixed with a radioactive gas such as Xenon (Xe.sup.133) into the lungs of the subject. A conventional scintillation camera or other radioactive recording device is operated to produce a permanent visual record. A separate air reservoir provides non-tagged air to fill the breathing passages and confine the radioactive tagged air to the lungs. The apparatus operates in sequence to supply the desired quantity of radioactive tagged air from a reservoir, followed by the measured quantity of ordinary air from a second reservoir, and then prevents exhalation during the time period necessary for the radioactive recording device to operate. The supply of premeasured quantities of tagged air and additional air insure that the subject will take only a normal size breath. Ganged stepping switches and a timing device provide automatic sequencing. A modified form of the apparatus utilizes a flexible wall radioactive gas reservoir and an associated pivoted lever which drops down to actuate a microswitch and open the valve to the additional air when the radioactive gas reservoir is depleted. A method is described in which measured quantities of tagged air and additional air are sequentially applied to the subject, exhalation is prevented during the period in which the radioactive recording is made, and exhalation is thereafter permitted.

Description

BACKGROUND OF THE INVENTION

This invention relates to an Automatic Control System For Radioactive Regional Ventilation Studies, and more particularly to a method and apparatus to facilitate the making of a permanent visual record of the air passages of the lungs with a scintillation camera or other radioactive recording device responsive to radioactive emissions from a quantity of radioactive tagged gas breathed into the lungs by the subject.

Radioactive ventilation studies have proven to be valuable as a diagnostic tool. However, a number of problems have been encountered in the techniques used heretofore. A major problem results from the necessity of performing a number of mechanical operations in the proper sequence in less than a minute.

The proper quantity of radioactive tagged gas must be supplied to the lungs of the subject, and an additional quantity of air representing the tidal capacity of the subject's breathing passages should be placed in such passages, the breath must be held during the period of time necessary for the radioactive recording device to operate, and the exhaled radioactive tagged gas must be removed. Provision must be made to seal the system against escape of the radioactive gas, and the study must be made as comfortable as possible for the subject, who may be in poor physical condition.

SUMMARY OF THE INVENTION

The automatic control system of the present invention includes provisions for overcoming the recited difficulties by automatic sequencing of the procedures in a manner providing consistent and reproducable results. In order to simplify the operation, the complete procedure is operated from a compact control box, and preferably can be automatically programmed to cycle through the desired sequence.

It is important that, during the radioactive regional ventilation study, the patient take only a truly normal breath. A larger than normal intake expands the lung passages and the resulting scintiphoto thus indicates a false lung condition. Likewise, a smaller than normal intake produces an inaccurate indication of the lung condition of the patient. It is also advantageous to maintain the lung area in the normal size because of the normally limited camera coverage area available.

It is also an advantage during the radioactive regional ventilation study to concentrate the radioactive gas and restrict it solely to the lungs. In the present invention, this is accomplished by limiting the measured radioactive gas volume to the volumetric capacity of the lungs during a normal breath, and thereafter adding a measured quantity of normal air equivalent to the volumetric capacity of the breathing passages leading from the mouth to the lungs.

The present apparatus is capable of sequential operation either manually or by automatic cycling. In either case, the controls are interlocked to assure the desired sequence of operation.

Accordingly, it is an object of the present invention to provide an apparatus for conducting radioactive regional ventilation studies in which a measured quantity of radioactive tagged gas is supplied to the lungs of the subject in a manner simulating normal breathing action.

Another object of the present invention is to provide an apparatus of the character described in which the radioactive tagged gas is confined to the lung area by filling the breathing passages from mouth to lung with a measured quantity of normal air.

A further object of the invention is to provide an apparatus of the character described in which exhalation is prevented during the time necessary to operate a radioactive recording device.

A still further object of the invention is to provide an apparatus of the character described which operates automatically in a desired timed sequence.

Yet another object of the present invention is to provide a method of conducting radioactive regional ventilation studies in which measured quantities of radioactive tagged air and normal air are sequentially supplied to the lungs and breathing passages of the subject at ambient pressures and in a manner closely approximating a normal breath, with exhalation of same being prevented during operation of a radioactive recording device.

Other objects and features of advantage will become apparent from the following specification and the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred forms of the invention are illustrated in the accompanying drawings forming part of this specification, in which:

FIG. 1 is a schematic view of an automatic control system for radioactive regional ventilation studies constructed in accordance with the present invention;

FIG. 2 is a fragmentary enlarged plan view of a portion of the apparatus of FIG. 1;

FIG. 3 is an electrical circuit diagram illustrating a sequential stepping switch arrangement forming part of the present invention; and

FIG. 4 is a perspective view of a control device constructed in accordance with the present invention, said control device being responsive to depletion of a radioactive gas reservoir

While only the preferred forms of the invention have been illustrated in the drawings, it will be apparent that other modifications and changes could be made within the purview of the attached claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings in detail, it will be seen that the automatic control system of the present invention, basically includes a breathing device or mask 11 adapted for sealed communication with the breathing passages 12 of a living subject 13, control valve means 14 having inlet and outlet passages 16 and 17, the control valve means 14 being formed to permit inhalation by the subject 13 only from the inlet passage 16 and exhalation only through the outlet passage 17, a radioactive gas reservoir 18 capable of holding a measured volume of gas at ambient pressure, a gas supply valve 19 connecting said inlet passage 16 to the reservoir 18, an air supply reservoir 21 capable of holding a measured volume of air at ambient pressure, an air supply valve 22 connecting inlet passage 16 to reservoir 21, an ambient air supply valve 23 connecting inlet passage 16 to ambient air, an exhaust valve 26 connecting outlet passage 17 to conduit 24, and actuating means 27 operatively connected to the recited valves and formed for opening and closing these valves in a desired sequence.

The control valve means 14 is shown schematically in FIG. 2 as including check valves 28, 29 and 31 in the passages leading to the mask 11 from valves 19, 23 and 26, respectively. In FIG. 2, check valves 28 and 29 permit air from reservoirs 18 and 21, and ambient air to enter mask 11 through inlet passage 16, provided the associated valves 19, 22 or 23 are open, but prevent reverse flow of air or gas. Likewise, check valve 31 permits exhaled air to flow from mask 11 through outlet passage 17, provided valve 26 is open. Any suitable valve means which will permit inhalation from the inlet passage 16 and restrict exhalation to the outlet passage 17 could be used. A commercial valve of this nature is manufactured by W.E. Collins Co. and is identified by the part No. P-320.

Valve 19 is here connected through "Y" tubing to the reservoir 18 of radioactive tagged air through a check valve 32. The capacity of reservoir 18 is chosen to approximate the amount of air normally inhaled into the lungs of the subject during a normal breath (usually about 300cc). Valve 32 permits the radioactive tagged air to be removed from the reservoir 18, but prevents entry into reservoir 18 of the non-radioactive air from reservoir 23. Reservoir 21 contains an additional volume of non-radioactive air approximating the volume of the breathing passages of the subject between the mouth and the lungs (usually about 150cc).

Valves 19, 22, 23 and 26 are preferably provided with actuating devices which may be remotely controlled. Should manual operation be desired, it may be accomplished by solenoids or air actuators, controlled by a series of interlocking push-buttons, or individual switches, or air valves. A table listing the several switch positions and the resulting open or closed state of the valves, is as follows:

Xe Switch Ambient Gas In Air Air Scint. Position Air in (Valve exhaust reservoir Camera (Valve 19) (Valve (Valve 23) 26) 22) __________________________________________________________________________ 1 Open Closed Open Closed Off 2 Closed Open Open Closed Off 3 Closed Open Closed Open On 4 Closed Closed Closed Closed On 5 Open Closed Open Closed Off __________________________________________________________________________

The operator initiates the cycle by turning switch handle 41 on the control box 42 to position 1 which opens valves 23 and 26, allowing the subject to breath in ambient air through valve 23 and inlet passage 16, and to breath out through outlet passage 17 and exhaust valve 26, the exhaled air passing through a tube 43 to the exterior of the building.

During an exhalation, the operator moves switch handle 41 to position 2, closing ambient air supply valve 23 and opening radioactive gas supply valve 19 so that the next inhalation will draw the radioactive gas from reservoir 18.

At the instant the radioactive gas reservoir 18 is empty, the operator moves the switch handle 41 to position 3 which opens valve 22 to supply the additional volume of non-radioactive air from reservoir 21. Position 3 also closes the exhaust valve 26 and at the same instant supplies electrical energy to close a relay 43 which starts the scintillation camera or other radioactive recording device 44. The scintillation camera 44 requires approximately 5 seconds to register the 15,000 counts necessary for the print. The operator moves switch handle 41 to position 4 to close valve 19 and, inasmuch as the valves 23 and 26 are already closed, the subject is unable to exhale or inhale further.

At the expiration of the approximately 5 second time-count interval, the scintillation camera 44 automatically shuts off and the operator moves switch handle 41 to position 5, opening ambient air supply valve 23 and air exhaust valve 26 so the subject can resume normal breathing. Thus, switch settings 1 and 5 represent the same set of conditions.

Additional scintiphotos can be obtained at various time intervals following the initial tests, and under various conditions as selected by the operator, if so desired. Such additional tests can be automatically timed and programmed into stepping switch 38.

Where a completely automatic sequence is desired, stepping switch 38 is driven by timer 39, and the entire cycle is initiated by closing switch 46. Obviously, the timer 39 should be adjusted to permit sufficient time at each of the switch positions for the intended function to take place.

A modified form of the invention is illustrated in FIG. 4 wherein valve 22 is opened automatically as soon as the contents of the radioactive gas reservoir are exhausted. The reservoirs 18a and 21a, corresponding to reservoirs 18 and 21 in FIG. 1, are provided in the form of inflatable, flexible walled bags, such as rubber bags. Reservoir 18a is supported on a platform 51, to which a swingable arm 52 is pivoted to overlie and rest upon reservoir 18a so that arm 52 swings upwardly as bag 18a is inflated and swings downwardly as bag 18a is deflated. Arm 52 is in the position shown in solid lines at the beginning of the cycle when reservoir 18a is inflated. As the subject exhausts the contents of reservoir 18a, the arm 52 drops under its own weight to the position shown in dotted lines where the distal end of arm 52 actuates a microswitch 53 to supply electrical current to open solenoid valve 22 and allow the normal air contents of reservoir 21a to be supplied to the subject.

From the foregoing it will be apparent that the automatic control system for radioactive regional ventilation studies of the present invention provides a novel method of conducting such studies and a novel apparatus capable of manual or automatic use.

Claims

We claim:

1. An automatic control system for radioactive regional ventilation studies, comprising

a breathing device adapted for sealed communication with the breathing passages of a living subject,

a control valve means for said breathing device having inlet and outlet passages and being responsive to the breathing of the subject to permit inhalation by the subject only from said inlet passage and exhalation only through said outlet passage,

a radioactive gas reservoir capable of holding a measured volume of gas at ambient pressure,

a gas supply valve connecting said inlet passage of said control valve means to said radioactive gas reservoir,

an air supply reservoir capable of holding a measured volume of air at ambient pressure,

an air supply valve connecting said inlet passage of said control valve means to said air supply reservoir,

an ambient air supply valve connecting said inlet passage of said control valve means to ambient air,

an exhaust conduit,

an exhaust valve connecting said outlet passage of said control valve means to said exhaust conduit,

and actuating means operatively connected to said valves and formed for opening and closing said valves in a desired sequence.

2. An automatic control system as described in claim 1, and wherein said actuating means further comprises an actuating mechanism for a radioactive recording device, with said actuating mechanism being operated at desired places in said sequence.

3. An automatic control system as described in claim 1, and wherein said actuating means is formed to cycle automatically through said sequence.

4. An automatic control system as described in claim 1, and wherein said actuating means further comprises solenoid actuators for each of said valves, and switch means formed to provide electrical current to said solenoid actuators in said desired sequence.

5. An automatic control system as described in claim 4, and wherein said switch means includes a stepping switch, and a timing device for cycling said stepping switch through said desired sequence in desired increments of time.

6. An automatic control system as described in claim 1, and wherein said air supply valve is responsive to depletion of said radioactive gas reservoir.

7. An automatic control system as described in claim 6, and wherein said radioactive gas reservoir comprises a flexible wall bag, a pivoted arm rests on said bag and is formed to drop through an arc as radioactive gas is removed from said bag, said air supply valve is electrically operated, and a switch device is positioned to intercept said arm and supply electrical current to said air supply valve so as to open the latter when said arm drops a desired distance.

8. A method of conducting radioactive regional ventilation studies, comprising the steps of

excluding ambient air from the breathing passages of a subject,

supplying a measured quantity of radioactive tagged air equivalent to the increase in normal volumetric capacity of the subject's lungs during normal breath of the subject, said radioactive tagged air being delivered at ambient air pressure to the breathing passages of the subject for inhalation into the lungs,

supplying an measured quantity of additional air to said breathing passages equivalent to the tidal volume thereof so as to concentrate said radioactive tagged air in the lungs,

preventing exhalation of said measured quantities of radioactive tagged air and additional air for a period of timed duration,

making a visual record of the lungs by radioactive recording during said period of timed duration,

and permitting exhalation of said measured quantities of radioactive tagged air and additional air at the end of said period.

9. A method of conducting radioactive regional ventilation studies as described in claim 8, and which comprises the additional steps of venting the exhaled radioactive tagged air to the outside.