throughout this description , the preferred embodiment and examples shown should be considered as exemplars , rather than limitations on the apparatus and methods of the present invention . referring now to the drawings , there is shown an incentive spirometer 100 , having a handle portion 20 , a base portion 30 , a volume chamber portion 50 , and a monitoring portion 80 . the handle portion 20 provides a convenient manner for holding and carrying the device , and for attaching the device to a bed , for example , where it can be readily accessible . the base portion 30 provides a platform upon which the device rests , and an integral information display receptacle for containing information such as the written instructions for use of the device which can be conveniently observed by a patient from the top or the bottom of the device when the device is in use . the volume chamber portion 50 provides a predetermined volume against which a patient &# 39 ; s respiratory system is exercised for a determinable volumetric capacity to obtain the benefits of this therapy . the monitoring portion 80 provides a visual display for a patient to determine the correct flow of inspiratory air to be applied by the patient &# 39 ; s respiratory system during therapy , and in cooperation with the volume chamber portion 50 , permits the patient to determine the quantity of inspiratory air which has been drawn into the patient &# 39 ; s lungs at the correct flow rate . as best illustrated in fig1 , 3 and 8 , the monitoring portion 80 includes an inlet port 81 formed as an opening in a front wall 83 of the monitoring portion through which a patient draws inspiratory air by means of a mouthpiece 91 connected to a flexible popple tube 93 . the tube 93 is sized to be securely positioned over the connecting port in which is carried a one - way valve 82 to permit a patient to draw inspiratory air through the mouthpiece 91 , but which blocks the passage of expiratory air from passing back into the device . the monitoring portion 80 permits the patient to monitor the inspiratory air flow rate being applied by the patient &# 39 ; s respiratory system during therapy , and in cooperation with the volume chamber portion 50 , to monitor the volume or quantity of air being inhaled . to this end , the monitoring portion 80 includes an indicator 85 of a predetermined weight , preferably approximately 0 . 5 grams , which is vertically moveable between two parallel guide rails 86 ( best shown in fig3 ) which are formed between the front wall 83 and a back wall 84 of the monitoring portion 80 defining an indicator channel 75 . the channel 75 in which the indicator 85 is vertically moveable , formed between the front and back walls 83 , 84 and the guide rails 86 , is in fluid communication with the inspiratory air inlet port 81 so that as a patient draws inspiratory air from the mouthpiece 91 , the flow of air will cause the indicator 85 to rise in the channel so formed . a pair of air channels 72 and 78 are formed in the monitoring portion 80 to provide fluid communication , respectively , between the inlet port 81 and the indicator channel 75 , and the inlet port 81 and the volume chamber portion 50 , for a purpose to be hereinafter described in detail . a pair of indicator stops 85a are positioned to extend across the channel 75 to define the upper and lower limits of travel of the indicator 85 within the channel . in the preferred embodiment , a window 88 or other suitable indicia such as target or demarcation lines are formed on the front wall 83 to delineate a positional range within which a patient is to keep the indicator 85 when inhaling . in this manner , a patient can monitor the proper rate of flow of the inspiratory air which is to be drawn into the respiratory system , by keeping the indicator 85 within the target area 88 of the indicator . on the back wall 84 , a connecting oxygen inlet port 94 is formed to receive a connection from a source of oxygen . the oxygen inlet port 94 extends from the rear of the back wall 84 , through the back and front walls 84 and 83 of the monitoring portion 80 , and terminates at an oxygen discharge outlet 97 positioned adjacent to the inlet 81 through which a patient draws inspiratory air . the oxygen discharge outlet 97 is positioned such that the flow of oxygen is directed across an inlet 87 through which air is drawn into the device when the patient inhales through the mouthpiece 91 , and not directed into the inlet 87 . in this manner , the oxygen being supplied will not effect the patient created air flow applied to the device when in use . a cowling 98 partially surrounds the air inlet 87 to facilitate oxygen being drawn into the inlet 87 during use by a patient , without the flow of oxygen effecting a patient &# 39 ; s use of the device or the monitoring of the rate of inspiratory air flow applied by a patient when using the device . the volume chamber portion 50 includes a chamber 51 of a predetermined volume carrying a piston 53 therewithin . the air channel 78 forms a fluid connection between the inspiratory air inlet port 81 and the top 52 of the volume chamber 51 . in this manner , when inspiratory air is drawn through the mouthpiece 91 , the piston 53 will be drawn upwardly . if a patient is drawing inspiratory air at the desired target flow rate as shown by the indicator 85 , the volume of air drawn into the patient &# 39 ; s respiratory system can be determined by observing the calibrations 56 marked on the chamber 51 . a slidable indicator 57 is carried on the chamber 51 and may be movably positioned by the patient to a preselected volume calibration mark 56 to facilitate convenient use of the device . outlet ports 59 are formed in the bottom portion of the chamber 51 to facilitate the piston 53 returning to the bottom of the chamber 51 when the negative pressure from the patient &# 39 ; s inspiration of air is terminated . to adjust the time in which a desired quantity of inspiratory air has been ingested by a patient at the desired rate of flow , a venturi plate 79 is positioned across the air channel 78 to provide an orifice of a predetermined size . in this manner , a standard sized air channel 78 can be utilized in manufacturing the device , with adjustments in the calibration of the flow rate required to be applied in order to attain the target rate , being determined by the size of the orifice 79a in the venturi plate 79 , and one or more tuning openings 77 which may be formed in the front wall 83 . to use the same basic spirometer construction for both adult and child patient groupings , for example , a venturi plate 79 having a different sized air - flow - restricting orifice 79a can be utilized in the air channel 78 to accommodate different volumes of air being drawn at the desired flow rate , depending upon whether the spirometer is intended to be used by children or adults . for example an orifice 79a having an opening of approximately 0 . 1 by 0 . 05 inches has been found suitable for adults , while the same spirometer structure with a venturi plate 79 having an opening of approximately 0 . 1 by 0 . 07 inches has been found suitable for children . as best shown in fig1 the venturi plate 79 comprises two portions , one portion being attached to each of the front and back walls 83 and 84 , respectively , with a part of each portion being removed to form the orifice 79a . for manufacturing purposes , it has been found that one of the portions forming the venturi plate 79 is best formed with the size of the part removed to form the orifice 79a remaining constant , while the other portion forming the venturi plate 79 may be formed with the part removed varying to change the size of the orifice 79a in response to the desired volume of air to be withdrawn by the user of the device . in this manner manufacturing the dimensional changes in the opening is more easily facilitated . after the desired size of the orifice 79a has been determined , based upon the patients with whom the spirometer is to be used , the individual spirometers are then tested for correct calibration . the tuning openings or ports 77 are all initially open , and are selectively closed for any particular spirometer in order to more precisely control the rate of flow that must be inspired by the patient in order to attain the desired volumetric goals when in use . in order to permit the patient to conveniently observe the instructions for use of the device , and to maintain those instructions in an accessible fashion , the base portion 30 is formed of a transparent material with an opening 31 in a skirt portion 32 of the base , best illustrated in fig3 and 5 . the opening 31 is formed between the top of the base and base pads 35 upon which the device stands . in this manner documentary materials , such as the instructions 36 for the use of the device , can be inserted into the base through the opening 31 , and will be supported by the base pads 35 above the surface upon which the device is placed . because the base is preferably formed of a transparent material , the instructions may be folded in a manner so that they are observable through the top and the bottom of the base to facilitate a patient &# 39 ; s reference to them while the device is in use . the handle portion 20 is joined at its lowermost end to the base portion 30 , and at its uppermost end to the volume chamber portion 50 . a closed portion is formed between a handle 21 and the chamber 51 enabling a patient to grasp and carry the device . an open hook projection 23 is formed by the uppermost part of the handle 21 enabling the device to be conveniently hung over a rail or a portion of a bed for convenient access by patients that are so confined . while this invention has been described in the specification and illustrated in the drawings with reference to preferred embodiments , the structures of which have been disclosed herein , it will be understood by those skilled in the art to which this invention pertains that various changes may be made , and equivalents may be substituted for elements of the invention without departing from the scope of the claims . therefore , it is intended that the invention not be limited to the particular embodiment disclosed in the specification and shown in the drawings as the best mode presently known by the inventors for carrying out this invention , nor confined to the details set forth , but that the invention will include all embodiments , modifications and changes as may come within the scope of the following claims :