The present disclosure relates generally to a bag valve mask (BVM) to deliver positive pressure ventilation to a patient having trouble breathing and, more particularly, to automate control of a BVM.
Artificial ventilation has been a medical practice for a long time, with some of the earliest reports in the mid-18th century. The earliest bag valve mask (BVM) was introduced in 1956 and nicknamed the “Ambu” (Artificial Manual Breathing Unit). A BVM is a medical device used to provide positive pressure ventilation to patients who are unable to breathe unassisted or need an influx of oxygen. The bag valve mask comprises a flexible air chamber or bag attached to a face mask via a shutter valve. When the BVM is properly applied to a patient's face and the bag is squeezed, air is forced through the valve and into the patient's lung. When the bag is released, air with depleted oxygen levels is drawn while also allowing the patient's lungs to deflate to the ambient environment, especially in single user scenarios.
Due to its popular usage in emergency settings, many innovations have been attempted and some have become a part of the BVM, such as antiviral filters and one-way exhalation valves. This has become increasingly prevalent with the arrival and subsequent effects of COVID-19. However, problems, complications, and shortcomings remain in traditional BVM designs that need to be addressed BVM users within emergency medical services (EMS) and clinical emergency medicine (EM) need a way to gauge tidal volume and internal lung pressure delivered in order to prevent patient injury. Additionally, BVM users within EMS and clinical EM need a way to reduce operator fatigue during extended operation.
The present disclosure provides a patient ventilation system comprising a BVM that is operable in both a manual operating mode and an autonomous operating mode. In the manual operating mode the user operates the BVM manually. Sensors collect data from which performance metrics are calculated and displayed to the user. The displayed metrics (e.g., airway pressure, tidal volume delivered, ventilation rate, and gas concentrations) provide responders with performance feedback allowing them to correct inadequate ventilation. Once the user is satisfied with their performance, they can then enable automated ventilation to provide consistent ventilation to the patient. The controller recognizes the user's technique and with the press of a button, the control system of the DIVA mirrors the performance of the user.
Automated ventilation fulfills the role of one responder (squeezing the bag at an adequate respiratory rate) allowing a single provider to focus on ensuring leak-proof mask seal around the patient's nose and mouth. This, in combination with sensor feedback to ensure adequate ventilation, minimizes the physical and mental strain on responders and improves patient outcomes.
A common problem encountered by users of traditional BVMs is that traditional BVMs can often exceed the upper threshold of the appropriate volume of air delivery, which could easily put a patient in a critical condition by causing lung injuries or other related conditions. One reason why traditional BVMs fail to deliver an appropriate amount of air is because, although the simplicity of BVMs allows for rapid deployment and use, lack of tidal volume delivery measurements often forces the operator to rely on ambiguous metrics such as chest rise. Such metrics can be quite difficult to rely upon depending on the body mass index of the patient. Thus, one advantage of certain embodiments discussed herein is a BVM design that will protect patients from erroneous use of the BVM that may end up in critical injuries.
In traditional BVMs, mask seal around a patient's face is achieved using two hands gripping around the mask and pulling up the patient's chin. However, in an emergency setting, it is common for only one medical provider to operate a BVM. This can make achieving appropriate mask-seal difficult. Further, the operation of squeezing a BVM over long durations of time can cause operator physical and emotional strain. Thus, another advantage of one or more embodiments discussed herein is a BVM design that facilitates ease of operation, particularly over protracted periods of time.
In general, a BVM is used for 15-45 minutes in one setting until they can switch to another provider or connect to hospital-use ventilation systems. In such a scenario, the provider is not only using the BVM by squeezing the bag every 6 to 8 seconds while keeping a good airway and mask seal, but is also monitoring other vitals and maneuvering calls to hospitals and other tasks, possibly in a moving, noisy, and bumpy ambulance ride. The mental and physical task load of an Emergency Medical Technician (EMT) or Paramedic is greatly challenged, given that they may be the only hope to keep a patient alive. Thus, mask seal leakage, the inability to gauge tidal volume delivery, and user physical and emotional strain became a significant priority in the development of compatible solutions. Embodiments of the present disclosure address at least some of these problems while also mitigating the frequency and/or extent of lung injuries caused by misuse of BVM.
In particular, embodiments of the present disclosure include a BVM comprising a sensor-based patient feedback system to provide operators with performance metrics as well as semi- or fully automatic assistance in operating the BVM. One or more such embodiments advantageously solve the pain points described above by freeing at least one hand from constantly squeezing the bag of a traditional BVM. Consequently, a BVM user can use a freed hand to ensure better mask seal, and/or use other equipment to ensure safe delivery of oxygenated air.
During use, the self-inflating bag 22 is manually or automatically collapsed to force air through the patient valve 26 and into the face mask 28 to provide positive pressure ventilation. When the pressure on the self-inflating bag 22 is released, the self-inflating bag 22 re-expands to draw air in through the air intake 24. Gases exhaled by the patient exit through the exhalation port in the patient valve 26.
Automation of the BVM 20 can be achieved by having a mechanism, referred to herein as an actuator 40, to compress the self-inflating bag 22 of the BVM 20. The actuator 40 can be independent of the self-inflating bag 22, like an external air pump connected to the self-inflating bag 22, or a mechanism that integrates with the self-inflating bag 22. The actuator 40 can be driven by a servo motor and powered by an onboard rechargeable battery (not shown).
When the autonomous mode activated, the servomotor 56 turns in a first direction during an inhalation phase and reverses direction during an exhalation phase. In the inhalation phase, the servomotor 56 pulls the internal linkages 46, 48 inward, collapsing the self-inflating bag 22 and forcing air out through the face mask 28. In the exhalation phase, the servomotor 56 reverses direction allowing the self-inflating bag 22 to re-inflate. This process can be repeated, allowing for automated ventilation.
The actuator 40 fits within the dimensions of a typical BVM 20, enabling complex automation and sensor feedback within a form factor that is both portable and familiar to users.
The control system 60 provides feedback to the user via the user interface 80 and automates operation of the BVM 20 in the autonomous mode. The control system 60 comprises a flow rate sensor 62 and a pressure sensor 64 providing feedback to a controller 66, which generates control signals based on the feedback from the sensors 62, 64 to control the servomotor 58. The servomotor 56 and sensors 62, 64 can be coupled to the controller 66 via a wired or wireless interface (e.g., BLUETOOTH) 68. In some embodiments, the control system 60 may further include one or more gas concentration sensors located in the patient valve 26 to measure, for example, the oxygen concentration in the air provided to the patient and the carbon dioxide concentration in the exhaled air.
The flow rate sensor 62 and pressure sensor 64 are disposed in the air flow path between the self-inflating bag 22 and the face mask. For example, the flow rate sensor 46 and pressure sensor 64 can be disposed in the patient valve 26. As air flow through the patient valve 26 from the self-inflating bag into the face mask 28 during the inhalation phase, the flow rate sensor 62 and pressure sensor 64 measure the flow rate and pressure respectively. Exhaled air passes through the same flow rate sensor 62 and pressure sensor 64 in the exhalation phase. The measurements made by the flow rate sensor 62 and pressure sensor 64 are input to the controller 66 and used to make adjustments to the drive signals for the actuator 40.
The user interface 80 provides means to receive user input and to output information to the user for viewing. The user interface 80 can be coupled to the controller 66 via a wired or wireless interface (e.g., BLUETOOTH) 70. The user interface 80 comprises one or more input devices 82 to set and/or adjust the operating parameters of the controller 60, and a display 84 to display information for viewing by the user. The user interface could also provide audible or tactile feedback to the emergency responder in place of or in addition to visual feedback. The user interface 80 can be coupled to the controller 66 by a wired or wireless interface.
The user input devices 82 may comprise one or more push buttons, a keypad, pointing device (e.g., mouse or trackball), touch screen, voice control, or combination thereof. Display 84 may comprise an electronic display such as a light emitting diode (LED) display, liquid crystal display (LCD), or other common type of display. In some embodiments, the display may comprise a touch screen display that also serves as a user input device 82. The main purpose of the display 84 is to display operating parameters or metrics (e.g., airway pressure, tidal volume delivered, and gas concentrations) to provide responders with performance feedback, allowing them to correct inadequate ventilation.
In the manual operating mode, the user manually operates the BVM 22 and the sensors 62, 64 provide feedback to the controller 66 to generate performance metrics that can be displayed on the display 84. Based on the feedback, the user can make adjustments to achieve the desired ventilation for the patient. In one embodiment, the displayed information comprises the ventilation rate and tidal volume. The concentrations of oxygen in the inhaled air and the CO2 in the exhaled air could also be displayed. The control system 60 also performs one or more safety checks as hereinafter described and alerts the user if an unsafe condition is detected to prevent injury to the patient.
In the automated mode, the user may enter target ventilation parameters (e.g., ventilation rate and tidal volume) via the user interface 80 and the controller 66 generates drive signals to operate the BVM 20 based on the input parameters. Generally, the controller 66 determines the angular displacement of the servomotor 56 needed to achieve the target tidal volume. Once the target tidal volume is determined, the controller 66 determines the motor speed from the target ventilation rate and angular displacement. The controller then computes the drive signals based on the computed motor speed and angular displacement.
During the autonomous operating mode, the control system 60 monitors the flow rate and pressure from the sensors 62 and 64 and computes the actual ventilation rate and tidal volume from the measured flow rate and timing of the inhalation/exhalation phases of the ventilation cycle. The controller 66 compares the computed values of the ventilation rate and tidal volume to the target values input by the user and computes error values based on the comparison. The control system 60 adjusts the drive signals sent to the actuator 40 based on the error values. For example, if the ventilation rate is low, drive signals are generated to increase the motor speed of the servomotor 56 and shorten the duration of the ventilation cycle. If the ventilation rate is high, drive signals are generated to decrease the speed of the servomotor 56 and increase the duration of the ventilation cycle. As another example, if the tidal volume is low, the control system 60 may adjust the angular displacement of the motor to increase the stroke length of the link mechanism 42, i.e., to increase the amount by which the self-inflating bag 22 is compressed. If the tidal volume is high, the control system 60 may adjust the angular displacement of the motor to decrease the stroke length of the link mechanism 42, i.e., to decrease the amount by which the self-inflating bag 22 is compressed. Note that changing the stroke length of the link mechanism may also require adjustment of the motor speed if the ventilation rate is unchanged.
Automated ventilation fulfills the role of one responder (squeezing the bag at an adequate respiratory rate), allowing a single provider to focus on ensuring leak-proof mask seal around the patient's nose and mouth. This, in combination with sensor feedback to ensure adequate ventilation, minimizes the physical and mental strain on responders and improves patient outcomes.
As shown in
The patient ventilation system 10 may transition directly from the autonomous operating mode to the manual operating mode. As noted above, the controller 66 performs a series of safety checks in the autonomous mode to avoid injury to the patient. If the controller 66 detects an unsafe condition, the controller 66 alerts the user and switches automatically to the manual operating mode.
Referring to
After the ventilation parameters are computed, the controller 66 performs a series of checks in order to ensure patient safety. In the first check, the controller 66 compares the computed ventilation rate to a threshold (block 235). Separate thresholds can be used to define a range. For example, an upper threshold and a lower threshold can be defined for the ventilation rate. If the moving average is outside the range defined by the thresholds, the controller alerts the user, e.g., by generating an alarm (block 255). In the second check, the controller 66 compares the tidal volume to a threshold and alerts the user if the threshold is exceeded (blocks 240, 255). In the third check, the controller 66 compares the measured pressure to a threshold and alerts the user if the threshold is exceeded (blocks 245, 255). After these safety checks are performed, the controller 66 determines whether the user has commanded a switch to the autonomous operating mode, for example, by pressing a button (block 250). If not the control loop 200 repeats until the autonomous mode is enabled or until the system is powered off. If the user switches to the autonomous mode, the manual control loop 200 terminates and control passes to the autonomous control loop 300.
While in the autonomous operating mode, the controller 66 also performs a series of safety checks to prevent injury to the patient. First, the controller 66 checks the motor position to make sure that it is within expected bounds (block 340). Second, the controller 66 checks the flow rate to make sure that it does not deviate from the expected flow rate by more than a predetermined threshold (block 345). In other embodiments, controller 66 may check whether the flow rate exceeds a predetermined threshold that might injure the patient. Third, the controller 66 checks the pressure to make sure that the pressure does not deviate from the expected pressure by more than a threshold (block 350). In other embodiments, controller 66 may check whether the pressure exceeds a predetermined threshold that might injure the patient. If any safety checks fails, the controller generates an alert and switches to the manual operating mode (block 365). If the performance is as expected, the controller 66 checks for a command to switch to a manual mode (block 355). If a command to switch is detected, controller 66 returns to autonomous mode. Otherwise, controller 66 pauses for an intercycle delay (block 360) and control returns to block 325.
Following each cycle, the controller 66 receives the flow rate and pressure from the sensors 62 and 64 and computes the actual ventilation rate and tidal volume from the measured flow rate and timing of the inhalation/exhalation phases of the ventilation cycle. The controller 66 compares the computed values of the ventilation rate and tidal volume to the target values input by the user and adjusts the drive signals sent to the actuator 40 based on the error values.
The patient ventilation system 10 allows a single emergency responder to operate the BVM 22 to provide respiratory aid to a patient. Displaying performance metrics enables the emergency responder to adjust their technique to provide adequate air flow to the patient while reducing the chance of patient injury and the emotional strain on the emergency responder. Once the user is satisfied with their performance, they can then enable automated ventilation to provide consistent ventilation to the patient. The controller recognizes the user's technique and with the press of a button, the control system of the DIVA mirrors the performance of the user. The autonomous mode fulfills the role of one responder (squeezing the bag at an adequate respiratory rate) allowing a single provider to focus operate the BVM 20 so that other responder can focus on other tasks.
This application claims the benefit of U.S. Provisional Application No. 63/420,351, filed Oct. 28, 2022, the entire disclosure of which being hereby incorporated by reference herein.
Number | Date | Country | |
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63420351 | Oct 2022 | US |