referring now to fig1 there is shown a schematic view of a ventilator apparatus suitable for carrying out the present invention . in fig1 there is shown a typical system for carrying out the ventilation of a patient 10 including a ventilator 12 . the ventilator 12 may be of conventional construction or may be constructed as shown and described in u . s . pat . no . 5 , 315 , 989 of tobia , assigned to the present assignee and the disclosure of which is incorporated herein by reference . as is conventional , the ventilator 12 provides a breathing gas to the patient 10 by means of a patient breathing circuit 14 which comprises , preferably , an inhalation limb 16 and an exhalation limb 18 . appropriate check valves 20 and 22 are provided in the inhalation limb 16 and the exhalation limb 18 , respectively , to insure that the gas flows in the proper direction through the patient circuit . the patient 10 is connected to the patient breathing circuit 14 by means of a connector , such as a y piece . a flow sensor 24 is provided in the exhalation limb 18 of the patient breathing circuit 14 and its purpose will be later explained . it is also noted that while the present invention is described in terms of a single flow sensor located in the exhalation limb 18 , the invention may be used with two flow sensors , one located in the exhalation limb 18 and the other located in the inhalation limb 16 . ventilator 12 is controlled by a processor , shown as a central processor unit or cpu 26 and which provides the input to the ventilator 12 to carry out its various functions , again , in conventional manner . the ventilator 12 may be activated by the user by a switch 13 where the ventilator provides a breath automatically to the patient or inactivated when the clinician is manually bagging the patient and thus is providing the breath to the patient by squeezing a flexible bag to provide that breath . as typical controls that are inputted to the cpu 26 various alarm conditions are set by the clinician and which establish the alarm conditions for certain functions of the ventilator . as shown , one alarm is the minute volume alarm and the minute volume input 28 allows the user to determine the alarm limits for that parameter . for example , the minute volume is a measure of the amount of gas delivered to the patient in a minute and may range from about 0 . 1 to 30 liters per minute . therefore , the clinician may set a minimum value and a maximum value for that parameter and an alarm 30 is activated when the flow sensor 24 detects that parameter . for minute volume , the flow sensor 24 determines the flow in the exhalation limb 18 and that value is calculated with respect to a clock it the cpu 26 to provide a timed signal representative of the volume per minute seen by the sensor 24 . a further alarm that is normally available on medical ventilators is the volume alarm , that is based upon the volume that is exhaled by the patient . that volume must be a least a predetermined volume or an alarm will sound . in the case of the volume alarm , again the flow sensor 24 may be used and the signal from the flow sensor 24 is integrated with respect to time in the cpu 26 to obtain a signal representative of volume . this alarm , like the minute volume alarm is satiable by an input 32 that is determined by the user to be within , for example 20 to 1600 ml . generically , the minute volume and the volume parameters are considered as volume monitors and their control state may generally be selected by the clinician together as will later be explained . lastly , there is a standard monitor or alarm known as the apnea alarm and it again depends on signals from the flow sensor 24 to provide an input for the alarm function . with the apnea alarm , the flow sensor 24 must see a certain discernable flow which is integrated to volume . a certain volume must be seen during a predetermined time period to continually reset the alarm . as an example , the alarm may reset if the flow is seen by the flow sensor 24 every thirty seconds and , conversely , if the flow is not sensed by the flow sensor 24 during that period of time the alarm 30 will be activated to bring that condition to the attention of the clinician . the selection of what alarms are active or inactive is made by the clinician in accordance with personal preferences , the condition of the patient or the operation of the ventilator . therefore , depending on the particular situation , the apnea alarm may be on or off and the volume alarms may be on or off and thus their state is subject to the selection by the clinician with certain automatic operation as will be explained , as shown in fig1 the control panel 34 enables the clinician to select the desired state of the alarms and the signal from the control panel 34 is communicated to the cpu 26 . turning now to fig2 there is shown a schematic view of the states of the various alarms on control panel 34 that is utilized by the clinician to make a selection of the various states of the alarm systems . the control panel 34 is , of course , merely schematic to represent the various states of the alarm system and may be carried out in many ways . the states may actually be shown on a panel by a lighted portions of the panel or any other means may be employed to let the user know what state is current of the alarms . basically , however , there are four alarm states represented by the block 35 as state 1 , block 38 as state 2 , block 40 as state 3 and block 42 as state 4 . each of the states is unique . for example , state 1 , block 36 is the state where the apnea detector alarm is off and the volume monitor alarms are on standby , thereby not activated . in state 2 , block 38 both the apnea alarm and the volume alarms are active , state 3 , block 40 , the apnea alarm is on and the volume monitor in standby and finally in state 4 , block 42 , the apnea detection alarm is off and the volume alarm is active . the user can select any one of the states by , for example , depressing a button 50 to advance the state to the next succeeding state , that is , by depressing the button 50 , the state will advance from state 1 to state 2 and successively thereafter . therefore , the user can select whatever alarm the clinician desires to be operative and / or inoperative . obviously , the selection of the particular state is by conventional means and can be a selector switch or other device to advance the state to the next succeeding state . taking , therefore , the states in order , in state 1 , none of the alarms is in the active state . therefore state 1 is intended for use as the ventilator is started up since , at the start up , the mechanical ventilator is not activated until it is enabled by the clinician . therefore , the ventilator alarm system is initially in state 1 but will automatically change to state 2 if any breath is observed by the flow sensor , since patient breathing has commenced . in addition , the control panel will also immediately switch to state 2 upon the clinician activating the mechanical ventilation by ventilator 12 via switch 13 . accordingly while the clinician can always manually activate the control from state 1 to state 2 , it will , on its own , make the switch without the intervention of the clinician if a breath is detected or the ventilator 12 is activated to commence mechanical ventilation . in either condition , it is important at that time that the patient have full monitoring and all alarms are thus activated when the mechanical ventilator 12 is on and will remain in state 2 for so long as the ventilator is on . state 2 , therefore is the most vigilant state since all of the relevant alarms are active . at this point , the clinician may activate the button 50 to change the state to state 3 providing mechanical ventilation is again deactivated . in state 3 , the clinician may be bagging the patient or the patient may be carrying out spontaneous breathing during emergence from anesthesia . the clinician may want apnea detection , however , in this state , the volume monitors will be seeing erratic breathing and the clinician may not want to have constant alarms where that breathing is outside the limits set in the cpu 26 . in state 4 , therefore , again the mechanical ventilator 12 must be inactive and the apnea alarm is off and the volume alarms are activated . in this state , the clinician typically will set the alarm limits to their most remote settings , that is the highest alarm setting of the high setting and the lowest alarm setting of the low alarm setting such that the volume alarms are basically out of the system . here , the clinician may be bagging or intubating the patient . in effect , the alarm conditions are generally set by the clinician to be similar to the state 1 conditions and all of the alarms are inactivated , however , the control will stay in state 4 even if spontaneous breathing is detected , unlike state 1 where the detection of breaths would automatically cause the control scheme to advance to the state 2 position . it should be pointed out , however , whenever the ventilator 12 is put in the on position and activated , the control will automatically go to the state 2 condition such that all of the various alarms are activated no matter what state the control panel is in when that activation of the ventilator 12 takes place . accordingly the control system is activated by the user to choose the particular alarm desired for the volume and apnea alarms , however , it also overrides the clinician &# 39 ; s selection to activate all of the alarms when the ventilator 12 is activated for the safety of the patient and to insure that there is the maximum of alarm protection where the patient is undergoing mechanical ventilation . while the present invention has been set forth in terms of a specific embodiment , it will be understood that the alarm control system algorithm herein disclosed may be modified or altered by those skilled in the art to other configurations . accordingly , the invention is to be broadly construed and limited only by the scope and spirit of the claims appended hereto .
a control system where the clinician can have manual control of the state for various alarms , generally volume alarms and apnea alarms . the control is interactive , that is , while the clinician can manually set the state in a variety of settings , the control system automatically overrides the clinician &# 39 ; s selection to activate both the volume and apnea alarms wherever the mechanical ventilator is turned on . in addition , there is another override where a breath is detected by the ventilator to turn all of the alarm systems from both being inactive to both alarms being active .