Abstract:
A barrier system, device, and method protects medical professionals and patients from exposure to contaminants and bodily fluids. The system includes a head unit (e.g.,  708 ) shaped to be worn over the head of the wearer; a hood (e.g.,  704 ) positioned over the head unit; one or more sensors (e.g.,  1902 ) configured to produce one or more sensor-output signals; and a controller (e.g.,  1904 ) connected to the one or more sensors and configured to produce one or more controller-output signals based on the one or more sensor-output signals. Further, a device inside a barrier system is controlled by (a) sensing one or more characteristics; (b) producing one or more sensor signals based on the sensed one or more characteristics; (c) converting and/or processing the one or more sensor signals to produce one or more controller-output signals; and (d) controlling the device based on the one or more controller-output signals.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 62/275,995 filed Jan. 7, 2016, the content of which is hereby incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    Embodiments of the invention relate generally to barrier devices, filtration devices, and personal protection systems for use in hazardous environments, including medical, surgical, and field environments. Certain embodiments protect medical professionals from exposure to airborne contaminants and bodily fluids and also protect patients, medical professionals, and observers from cross-contamination during surgical procedures. Certain embodiments relate more particularly to helmets, hoods, masks, face shields, togas, or other wearable apparatuses for protecting a healthcare professional, patient, or observer from exposure to biohazardous materials during surgery, other medical procedures, emergency medicine, treatment of victims in the field, and the like. 
       BACKGROUND OF THE INVENTION 
       [0003]    Barrier devices and personal protection systems are used in medical and surgical procedures to provide a sterile barrier between the surgical personnel and the patient. During such procedures (and especially during orthopedic operations), a drill or powered saw often generates spray, splash, and aerosol from a patient&#39;s surgical wound to the surgeon. This exposes the surgeon to a risk of infection. Traditional surgical masks and cups are not capable of completely keeping the sterility of the surgical wound. In some cases, bodily materials from a surgical team (e.g., sweat, hair, dandruff, or even saliva) may infect the patient. For these reasons, especially in orthopedic surgery, a surgical helmet has been used for many years. A conventional surgical helmet may include a battery-powered fan for air circulation and a sterile hood that covers the helmet and has a transparent visor, lens, or other vision element. 
         [0004]    One such system is disclosed in U.S. Pat. No. 5,054,480, the contents of which are incorporated herein by reference discloses that basic structure of such a system. Specifically, the traditional system includes a helmet that supports a toga, also known as a drape or hood. (The terms “toga”, “drape”, and “hood” are used interchangeably herein and are intended to have the same meaning.) This assemblage is worn by medical personnel who want to establish the sterile barrier. The hood includes a transparent face shield. The helmet includes a ventilation unit that includes a fan. The ventilation unit draws air through the hood so the air is circulated around the wearer. This reduces both the amount of heat that is trapped within the toga/hood and the carbon dioxide (CO 2 ) that builds up in this space. It is further known to mount a light to the helmet. The light, which is directed through face shield illuminates the surgical site. 
         [0005]    Donning a hood creates a closed chamber around the operator&#39;s head, which represents both a heating element (by means of radiation and/or convection) and a source of hot and humid respiratory air with significant CO 2  concentrations up to 40,000 ppm. Without air exchange between the chamber and the ambient environment, a so called “sauna effect” is created, leading to temperatures of up to 32° C., humidity levels of up to 85% (relative humidity) and CO 2  concentrations of up to 40,000 ppm inside the chamber. To avoid this effect, state of the art surgical protection systems include hoods with a filter element, which supports air exchange and provides breathability as well. This is typically accomplished using fans that move air into the chamber and circulate air within the chamber. 
         [0006]    Other personal protection systems are disclosed in U.S. Pat. No. 6,481,019 to Diaz et al., in U.S. Pat. No. 9,173,437 to VanDerWoude et al., and in U.S. patent application Ser. No. 13/984,908 filed by Giorgio Rosati et al., the contents of each of which is incorporated by reference in its entirety. VanDerWoude et al., for example, describes a system having a hood, a fan, a light, and a helmet with control switches that a user actuates by hand. 
       PROBLEMS TO BE SOLVED 
       [0007]    The present inventors have recognized and identified a number of drawbacks of conventional filtration apparel systems for health care professionals. 
         [0008]    Some systems establish a bypass between the operator&#39;s head chamber and the intake air funnel of the main fan, which allows waste air from inside the operator&#39;s head chamber to be drawn back into the chamber, thereby reducing the fresh air exchange rate, especially with filters having low breathability (i.e., high bacterial filtration efficiency). A significant portion of air delivered by the main intake fan is therefore waste air instead of fresh ambient air. This effect increases with decreasing breathability of filter materials. 
         [0009]    Another drawback relates to difficulty in donning. After putting on the helmet, adjusting it, and connecting the power line of the helmet to the battery pack, a user of a conventional hood dons the device in three steps, by: (1) unfolding the hood, (2) attaching the vision element to the helmet, and (3) pulling the fabric over the helmet. 
         [0010]    Known donning concepts require assistance by at minimum one sterile or non-sterile supporting individual in the operating theatre to avoid breaching sterility (of all outer surfaces of the gown) during donning. Conventional hoods use fixed-position vision element frames on the helmet. During attachment of the hood or toga to the front of the face, visibility is greatly reduced because of the opaque nature of the fabric. This prohibits the user from performing the next step—pulling the fabric over the helmet—by himself or herself, since the likelihood of contacting the outside of the fabric with a non-sterile body part is too high. Therefore, a sterile-dressed supporting individual is required to perform fabric-pulling step (3). Alternatively, a non-sterile dressed supporting individual might also perform step (3), with the limitation to touch only the inside of the fabric or only portions of the fabric that are subsequently covered by sterile surgical gowns. 
         [0011]    Another drawback relates to difficulty in fan-speed control. Required air exchange rates depend, among other factors, on ambient air temperature and humidity, physical activity during a surgical procedure, specific heat output of the human body, and mental stress level, as well as personal preferences for air conditions and air quality. Some conventional surgical protection systems offer user-adjustability of fan speeds to increase or reduce the air input. A higher or lower air input causes a higher or lower air circulation that may improve the comfort of the surgeon. The quantity of air circulation needed may vary according to personal preferences of the surgeon or his or her physical activity during the different phases of an operation, which may be lighter or heavier at various moments. 
         [0012]    Conventional surgical helmets regulate the fan speed by a button or switch placed somewhere on the helmet. To adjust fan speed, a surgeon must press a mechanical button or activate a touch switch located below the sterile barrier (hood or toga) and therefore must touch the barrier. This is neither safe nor convenient. During operation, the helmet is often covered by a sterile drape, and the surgeon must wear surgical gloves. Activating the switch is often difficult and inconvenient, because the surgeon can neither see nor easily feel where the switch is. It is unsafe, because the button or switch might become contaminated in certain circumstances, e.g., by unnoticed contact with a lamp, a colleague, or an unsterile part. By touching the switch, which is no longer sterile, the surgeon may contaminate his hands, other people, and other surfaces. 
       SUMMARY OF THE INVENTION 
       [0013]    Embodiments of the disclosure solve these problems and provide other benefits through a personal protection system and device employing one or more of the following features: an intake air duct with enhanced fresh air circulation; an easy-donning hood-helmet interface; a free-flow main air duct; automatic airflow control; and a touchless user interface. 
         [0014]    In one embodiment, the invention is a barrier system. The system comprises a head unit (e.g.,  708 ) shaped to be worn over the head of the wearer; a hood (e.g.,  704 ) positioned over the head unit and forming a chamber (e.g.,  212 ); one or more sensors (e.g.,  1902 ) located within the chamber and configured to produce one or more sensor-output signals; and a controller (e.g.,  1904 ) connected to the one or more sensors and configured to produce one or more controller-output signals based on the one or more sensor-output signals. 
         [0015]    In another embodiment, the invention is a method of controlling a device inside a barrier system comprising a head unit (e.g.,  708 ), a hood (e.g.,  704 ), one or more sensors (e.g.,  1902 ), and a controller (e.g.,  1904 ). The method comprises: (a) sensing one or more characteristics; (b) producing one or more sensor signals based on the sensed one or more characteristics; (c) converting and/or processing the one or more sensor signals to produce one or more controller-output signals; and (d) controlling the device based on the one or more controller-output signals. 
         [0016]    In another embodiment, the invention is a barrier device. The barrier device comprises: a head unit (e.g.,  708 ) shaped to be worn over the head of the wearer; a hood (e.g.,  704 ) positioned over the head unit and forming a chamber (e.g.,  212 ); one or more sensors (e.g.,  1902 ) located within the chamber and configured to produce one or more sensor-output signals; and a controller (e.g.,  1904 ) connected to the one or more sensors and configured to produce one or more controller-output signals based on the one or more sensor-output signals. 
         [0017]    In another embodiment, the invention is an apparatus for controlling a device inside a barrier system comprising a head unit (e.g.,  708 ), a hood (e.g.,  704 ), one or more sensors (e.g.,  1902 ), and a controller (e.g.,  1904 ). The apparatus comprises: (a) means for sensing one or more characteristics; (b) means for producing one or more sensor signals based on the sensed one or more characteristics; (c) means for converting and/or processing the one or more sensor signals to produce one or more controller-output signals; and (d) means for controlling the device based on the one or more controller-output signals. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    Other advantages of the present invention will be readily appreciated and better understood by reference to the following detailed description, when considered in connection with the accompanying drawings wherein: 
           [0019]      FIG. 1  is a perspective view of an exemplary surgical helmet in an embodiment of the disclosure. 
           [0020]      FIG. 2  is a top view of the surgical helmet shown in  FIG. 1 . 
           [0021]      FIG. 3  is a cross-sectional view of a first exemplary head unit having a top-mounted fan in an embodiment of the disclosure. 
           [0022]      FIG. 4  is a cross-sectional, scaled view of a portion of the head unit shown in  FIG. 3 . 
           [0023]      FIGS. 5 and 6  show a second exemplary head unit having a bottom-mounted fan in an embodiment of the disclosure. 
           [0024]      FIGS. 7-15  show an exemplary easy-donning hood-helmet interface in an embodiment of the disclosure. 
           [0025]      FIG. 16  is a perspective view of an exemplary surgical helmet having two lights in an embodiment of the disclosure. 
           [0026]      FIGS. 17 and 18  show an exemplary air duct in an exemplary head unit in an embodiment of the disclosure. 
           [0027]      FIG. 19  shows a block diagram of an exemplary touchless control system in an embodiment of the disclosure. 
           [0028]      FIGS. 20-22  show exemplary touchless-control sequences and movements. 
           [0029]      FIG. 23  shows a graph of an exemplary user-adjustable fan speed based on temperature. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    Embodiments of the disclosure solve these problems and provide other benefits by employing one or more of the following features: an intake air duct with enhanced fresh air circulation; an easy-donning hood-helmet interface; a free-flow main air duct; automatic airflow control; and a touchless user interface. 
         [0031]    With reference to  FIG. 1 , an exemplary surgical helmet  100  in an embodiment of the invention comprises: a head unit  102 , a lensframe  104  mounted on the head unit  102 , and an adjustable head strap  106  for securing head unit  102  on a user&#39;s head. 
         [0032]    With reference to  FIG. 2 , the head unit  102  comprises a fan intake duct  202  (forming zone 1) configured to guide intake airflow  204 , a mounting plate  206 , an intake fan  208  mounted on the underside of mounting plate  206 , a fan outlet  210  directed into a main air duct  212  located within a portion of head unit  102 , and a sealing edge  214 . 
         [0000]    Intake Air Duct with Enhanced Fresh Air Circulation 
         [0033]    Embodiments of the disclosure may include an intake air duct that is adapted to provide enhanced fresh air circulation.  FIGS. 2 and 3  show an exemplary intake air duct  202  in one embodiment of the disclosure. 
         [0034]    With reference to  FIG. 2 , head unit  102  comprises the intake air duct  202  in combination with intake fan  208  and a filter material  302  (e.g., formed by the fabric of a hood) that creates a plenum  306  (Zone 1), which is shown in  FIG. 3 . During operation, fresh ambient air  304  is sucked by the fan  208  through the filter  302  into the plenum  306  (zone 1) (and further through the fan  208  into the operator&#39;s head chamber  306 . The fan intake duct  202  is sealed off against the filter material  302  and the fan  208 , creating a local area of low pressure, thereby forcing the air to be drawn in only through the filter material  302 . This arrangement ensures that no bypass between the operator&#39;s head chamber  306  and the fan intake duct  202  is created. 
         [0035]    The sealing between the fan intake duct  202  and the filter material  302  is promoted by hydrodynamic forces because of local low pressure in the intake air duct  202  (zone 1). This effect helps to create a seal, even in the event that the filter material  302  is placed loosely on the fan intake duct  202 , without additional fixation means, as shown in  FIG. 3 . The sealing edge  214  seals reliably, because it is dimensioned such that the filter is concave (angle x°&gt;0 relative to the general plane of the sealing edge  214 ) because of negative pressure. 
         [0036]    The sealing edge  214  further seals reliably through protrusion of the filter material  302  over the surrounding surfaces. Additionally, a reliable seal between the fan  208  and the fan intake duct  202  is provided. 
         [0037]      FIGS. 5 and 6  show another exemplary intake air duct  502  in another embodiment of the disclosure. Like the embodiment shown in  FIG. 3 , a fan assembly  500  comprises an intake air duct  504  having a sealing edge  502 , and a fan  506  having a fan intake  508  and a fan outlet  510 . Fan assembly  500 , however, is configured so that the fan is recessed below the upper surface of intake air duct  506 , and it is bottom-mounted within the fan outlet  510 , rather than top-mounted on elevated mounting plate  206 . In contrast, the embodiment shown in  FIG. 4  does not need an elevated mounting plate. 
         [0038]    The present inventors have determined through experimentation that, in one embodiment, the negative pressure created by fan  208  is within a predetermined negative-pressure range having a lower-boundary vacuum pressure and an upper-boundary vacuum pressure. The lower-boundary vacuum pressure is the pressure at which the filter material  302  is pulled down so far that it interferes with the intake airflow  202 . At the lower-boundary vacuum pressure, the filter material reduces the intake airflow so much that the airflow is insufficient for adequate ventilation, which renders the helmet unuseable. The upper-boundary vacuum pressure is the pressure at which the filter material  302  fails to provide an adequate seal at sealing edge  214 . The upper- and lower-boundary vacuum pressures depend upon the characteristics of the filter material  302 . 
         [0039]    The present inventors further determined through experimentation that the intake airflow is a nonlinear function having an inflection point at an optimal vacuum pressure that varies depending on the type of filter material. Assuming that a fan starts operation at an initial ambient pressure, the magnitude of the negative pressure initially increases as the fan speed increases. As the negative pressure increases, the intake airflow correspondingly increases as a positive function of the negative pressure, and eventually reaches a maximum amount of airflow at the optimal vacuum pressure. 
         [0040]    Surprisingly, the present inventors discovered that if the negative pressure continues to increase past the optimal pressure, then the airflow begins to decrease, rather than to increase as one would ordinarily expect. When the magnitude of the negative pressure is larger than the optimal vacuum pressure, the intake airflow is therefore a negative function of the negative pressure. These results were counterintuitive and unexpected. 
         [0041]    The inventors also found that, even for a given fan, the way in which the fan is mounted and the shape of the intake air duct  202  may result in more airflow or less airflow, depending on the magnitude of the negative pressure exerted upon the filter material  302  and on the optimal vacuum pressure for a given filter material. They further found that, when certain fans are top-mounted within head unit  102  as shown in  FIG. 3 , they exert a smaller vacuum pressure, whereas when those fans are bottom-mounted (as shown in  FIG. 4 , described below), they exert a greater vacuum pressure. The inventors further discovered that, in certain circumstances, the vacuum pressure created by such fans may exceed the optimal vacuum pressure (i.e., a pressure that is past the inflection point), such that reducing the vacuum pressure by top-mounting the fan yields a greater airflow, rather than a smaller airflow. 
         [0042]    The inventors accordingly have discovered and identified a problem in which certain bottom-mounted fans yielded inadequate ventilation, and solved the problem by providing the elevated mounting plate shown in  FIG. 3 , which allows a fan to be top-mounted, and thereby reduces the vacuum pressure and increases the airflow. Further, when such fans are top-mounted instead of bottom-mounted, the fan size may be reduced because of the greater airflow, thereby achieving an unexpected increase in efficiency and a cost savings that makes the helmet more competitive in the marketplace. 
       Easy-Donning Hood-Helmet Interface 
       [0043]    Embodiments of the disclosure may include an easy-donning hood-helmet interface.  FIGS. 7-16  show an exemplary easy-donning hood-helmet interface, in one embodiment of the disclosure. In this embodiment, a vision element frame  706  (hereinafter referred to as lensframe  706 ) is adapted to swivel around pivot points or along a slotted link on head unit  708 , thereby allowing the user full visibility during donning, which reduces the likelihood of unintentional contact with the gown. Color-coded ribbons  702  (colored grey ( 702   b ) and white ( 702   a ), in this example) allow the user to pull the hood  704  over his or her own head, maintaining a safe distance to the outer surface of the hood  704  itself. 
         [0044]    The following steps are performed in an exemplary donning sequence consistent with one embodiment of the disclosure: 
         [0045]    As  FIG. 7  shows, Step  1  involves unpacking and unfolding the outer protection garment of the hood  704 . The hood  704  is folded inside-out to reduce risk of contamination. Color-coded ribbons  702   a,    702   b  indicate where to grab the hood  704  to complete donning. These ribbons will rest underneath the surgical gown after donning. 
         [0046]    Turning now to  FIG. 8 , Step  2  involves attaching the folded hood  704  on the lensframe  706 , in an open position. Geometrical guidance is provided by a centering hook (shown in  FIG. 16 ), located at the lower center of the lensframe  706  (where it is easily visible the lensframe is folded into an open position) as well as several hook-and-loop fasteners or magnets along the lensframe  706 . 
         [0047]      FIGS. 9 through 11  show the substeps  3   a,    3   b,  and  3   c  of Step  3 , which involves pulling the hood front  704   a  (shown shaded in grey) and back  704   b  (shown colored white) over the helmet  710  (formed by lensframe  706  and head unit  708 ) and the user&#39;s head, using the color-coded ribbons  702 . The ribbons are easily visible because of the lensframe  706  being folded into the open position. The lengths of the ribbons  702  are selected so as to avoid unintentional contact with the outer surface of the hood  704 . In the process of pulling the front  704   a  (grey) towards the user&#39;s chest and the back  704   b  up and over the user&#39;s head, the lensframe will fold automatically into operational position, where a transparent window portion  1002  (hereinafter referred to as lens  1002 ) of the hood front  704   a  is positioned over lensframe  706 . 
         [0048]      FIG. 12  shows an exemplary pivot-point-type swivel mechanism, and  FIG. 13  shows an exemplary slotted-link-type swivel mechanism. One or both of these mechanisms may be employed in embodiments of the disclosure. The swiveling action of the lensframe  706  is a rotation around pivot points  1202  (shown in broken lines in  FIG. 12 ) or a sliding motion along a slotted link formed by slot  1302  (shown in broken lines in  FIG. 13 ) in head unit  708  and tab  1304  of lensframe  706 . 
         [0049]    With reference now to  FIG. 14 , relative to a vertical line, the lensframe  706  (and therefore also the lens  1002 ) is tilted towards the chin area (at an angle of x°). This angle promotes concentration of fresh air flow around the user&#39;s nose and mouth, maximizes field of vision towards the patient, and creates room inside the hood at the forehead for optimum aerodynamics and accessories such as an LED light (shown in  FIG. 16 ) and a camera (not shown). 
         [0050]      FIG. 15  shows that the lens  1002 , as a vision element, is designed as a curve around the user&#39;s face area, utilizing an upper radius R 1  around the head&#39;s vertical centerline and a lower radius R 2  around the same centerline. In some embodiments, both radii are the same. 
         [0051]      FIG. 16  shows an embodiment of a surgical helmet  1600  in one embodiment of the disclosure, comprising dual head-lamps  1602 ,  1604  and a lens-alignment clip  1606 . Conventional surgical helmets typically include only one head-lamp. Through user feedback, the inventors discovered that one head-lamp is unsatisfactory, because it provides a narrowly focused beam that is often too dim for surgical purposes. The inventors solved this problem by providing two head-lamps. 
       Free-Flow Main Air Duct 
       [0052]    Embodiments of the disclosure may include a free-flow main air duct.  FIGS. 17 and 18  show an exemplary free-flow main air duct, in one embodiment of the disclosure. 
         [0053]    Because of ergonomic reasons (weight balance), main intake air fans (e.g., fan  208 ) are commonly located at the back of the head. This requires fresh air to be channeled forward towards a nozzle located in the proximity of the forehead by means of an air duct. Additionally, the upper part of the head (above the hairline) should be flushed with fresh, cool air during use. Furthermore, for a positive ergonomic fit of the system, the helmet assembly should have a relatively low weight and low center of gravity. 
         [0054]    As shown in  FIGS. 17 and 18 , head unit  708  comprises an air duct assembly including one upper surface  1302 , two side bounding surfaces (e.g.,  1704 ), and at least one bottom opening (e.g.,  1802 ), arranged such that a fourth bounding surface (or barrier)  1706  is partially formed by the upper part of the skull itself. This configuration allows a reduction of weight, while keeping the head flush above the hairline. 
       Automatic Airflow Control 
       [0055]    Embodiments of the disclosure may include automatic airflow control. With reference now to  FIG. 19 , an exemplary automatic airflow control system  1900  in one embodiment of the disclosure is shown. 
         [0056]    Automatic airflow control automatically compensates for the microclimatic effects of varying factors, such as physical activity or mental stress levels during surgical procedures, thereby reducing the need for manual adjustment of fan speed during use. This leads to an increased focus on the surgical tasks at hand, as well as a reduced amount of intentional contact between hand and hood/toga, which are by nature potential sources of contamination. 
         [0057]    As shown in  FIG. 19 , one or more sensors  1902  measure direct or indirect microclimatic conditions inside the sterile hood. The sensors  1902  may be located anywhere within hood  702 . In one embodiment, the sensors  1902  are positioned on an electronic board (not shown) that is mounted on the head unit  408 . 
         [0058]    Sensors  1902  are connected to a controller  1904  that is configured to receive one or more sensor signals and generate a fan-speed-control output signal based thereon. In one embodiment, controller  1904  comprises a fan-speed-adjustment (FSA) algorithm that converts the one or more sensor signals into a rate-of-change signal and further translates it (e.g., via an amplifier, a level-shifter, an analog-to-digital converter, a digital-to-analog converter, or an algorithm corresponding to such devices) into an output signal that is sent to the fan-speed control unit  1906 . The controller&#39;s output signal includes, e.g., the specific information of desired rate of change to the fan speed (RPM) over time and the direction of change (increase or decrease). Finally, variable-speed fan  1908  operates at a speed that is determined by, and corresponds to, the fan-speed control unit&#39;s output signal. 
         [0059]    In one embodiment, the controller  1904  is a digital processor having software that is configured based on a user&#39;s specific personal need or an operating-room or field condition, including, e.g., ambient temperature and ambient sunlight. The digital processor may be a general microprocessor, a digital signal processor, or a digital microcontroller. 
         [0060]    Controller  1904  and fan-speed control unit  1906  each may comprise an analog control circuit, a digital processor, a signal processor, or any combination thereof, in accordance with techniques known to those of ordinary skill in the art of control circuitry. Controller  1904  and fan-speed control unit  1906  also may be connected to an audio or visual signaling device (not shown) to indicate the selected fan speed to the user. 
         [0061]    Embodiments of the disclosure may include one or more of the following sensor features: 
         [0062]    1. Absolute and/or differential temperature measurement, using two temperature sensors, measuring both intake air temperature and the air temperature inside the hood (exhaust air temperature); 
         [0063]    2. Humidity sensing, measuring relative humidity of air inside the hood, using a humidity sensor; 
         [0064]    3. CO 2  sensing, measuring absolute CO 2  levels, e.g., by using a non-dispersive infrared detector (NDIR); 
         [0065]    4. Motion sensing, measuring static and dynamic acceleration of the head as a representation of physical activity (and therefore heating performance), e.g., via one or more accelerometers; 
         [0066]    5. Position or inclination sensing, e.g., via a position sensor or an inclinometer. 
         [0067]    6. Voice sensing, e.g., via a microphone; 
         [0068]    7. Voice-recognition sensor, e.g., via a microprocessor-based portable computer or smartphone connected to controller  1904  by a wired or wireless interface; and 
         [0069]    8. Proximity sensing, e.g., by a capacitive, infrared, or photoelectric sensor. 
         [0070]      FIG. 20  shows an embodiment in which the sensors  1902  comprise a motion sensor mounted on head unit  708 . In block  2002 , the motion sensor detects one or more head movements. In block  2004 , the FSA algorithm in controller  1904  determines the quality and quantity of the user&#39;s activity based on the detected one or more head movements. In block  2006 , the fan-speed control unit automatically adjusts the fan speed based on the determined user activity. For example, during periods of high activity, the controller  1904  produces an output signal that causes the fan-speed control unit  1906  to increase the fan speed. Conversely, during periods of low activity, the controller  1904  produces an output signal that causes the fan-speed control unit  1906  to decrease the fan speed. 
         [0071]    At any time during the use of the system, the user can increase or decrease the fan speed manually to adjust the microclimate to his or her actual personal preferences. Such manual adjustment is desirably performed using the touchless user interface, which is described below. 
       Touchless User Interface 
       [0072]    Embodiments of the disclosure may include a touchless user interface.  FIG. 21  shows an exemplary method for a user to employ a touchless user interface, in one embodiment of the disclosure. As shown, the user&#39;s forearm, wrist, and/or hand approaches his or her chin area up to a distance between 3 cm and 10 cm, and more preferably between 4 cm and 7 cm, and most preferably 5 cm, from the lens frame, always controlling his or her arm position and distance to the sterile hood  702  through visual contact with his or her hand. A proximity sensor (e.g.,  1902  in  FIG. 19 ) detects the approach and transmits a control signal to a signal processor (e.g., controller  1904  in  FIG. 19 ). The system acknowledges the signal input with audible and/or visual feedback to the user. 
         [0073]    In this embodiment, a capacitive or photoelectric sensor is used as a proximity sensor. State-of-the-art photoelectric sensors are advantageous because of their capability of measuring distance between the sensor and the sensor target. This allows the sensor to discriminate between hand gestures and reduce the risk of unintended inputs by the user. 
         [0074]    Furthermore, photoelectric sensors can compensate for transparent materials masking the sensor area. In this embodiment, such compensation is relevant because the sensor is located behind the transparent, sterile lens of the hood  704 . Once the sensor input is in line with predefined parameters (e.g., the distance between the user&#39;s hand and the sensor), the sensor transmits a signal to a signal-processing unit (e.g., controller  1904 ). Further processing is described above under the heading “Automatic Airflow Control.” 
         [0075]      FIG. 22  shows another exemplary method for a user to employ a touchless user interface, in an embodiment of the disclosure. In this embodiment, a motion sensor is mounted on head unit  708 . Controller  1904  is configured to monitor the movements of the user&#39;s head and to interpret one or more predetermined movements of the user&#39;s head (e.g., an unnatural backward head tilt as shown in image  2202 ) as a specific user input or command. Controller  1904  is further configured to control the fan or other accessories (such as a light or other device) and/or to switch between a manual fan-control mode to an automatic fan-control mode, based on the user&#39;s command. In one embodiment, controller  1904  is also configured to respond to a command by generating an audible sound or a visual signal. 
         [0076]    Thus, in block  2204 , controller  1904  determines that a user&#39;s motion corresponds to a predetermined user input. In block  2206 , in response to the user input, controller  1904  produces a confirmation sound. And in block  2208 , controller  1904  produces a corresponding output signal, e.g., corresponding to an automatic fan-speed mode-control setting, a specific manual fan speed, and/or a light-control setting. 
         [0077]    In one embodiment, controller  1904  is configured to provide a user-adjustable, automatic fan-control mode that combines both automatic fan-speed control and manual fan-speed control. The FSA algorithm in controller  1904  automatically selects a fan-speed setpoint that is a function of a temperature gradient, but it also allows the user to adjust the automatically selected setpoint to a higher or lower point, according to the user&#39;s needs. 
         [0078]      FIG. 23  is a plot showing fan speeds automatically selected by the FSA algorithm at different temperature gradients. In one embodiment, the FSA algorithm employs five levels of user adjustability (levels 1 through 5), as shown in the following table: 
         [0000]    
       
         
               
               
             
           
               
                   
               
             
             
               
                 Signal &lt;2 sec 
                 Shift fan speed algorithm up by equivalent of one level 
               
               
                   
                 and produce a single audio signal. 
               
               
                   
                 If already at level 5, shift FSA down to level 1 and 
               
               
                   
                 produce a double audio signal. 
               
               
                   
                 Each FSA level has his specific audio signal frequency 
               
               
                 Signal &gt;2 sec 
                 Switch Light on/off 
               
               
                 Without Signal 
                 FSA does adjust fan speed dynamically, based on dT, 
               
               
                   
                 dRH, dCO2 level or head motion input 
               
               
                   
                 Autonomous FSA adjustment without audio signal and 
               
               
                   
                 not recognizable by user due to stepless adjustment 
               
               
                 Repower the 
                 Shift fan speed algorithm to equivalent of fan Level 3 
               
               
                 system after 
               
               
                 disruption 
               
               
                 (battery 
               
               
                 disconnection) 
               
               
                   
               
             
          
         
       
     
         [0079]    Reference herein to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the disclosure. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiments. 
         [0080]    Although the disclosure has been set forth in terms of the exemplary embodiments described herein and illustrated in the attached drawings, it is to be understood that such disclosure is purely illustrative and is not to be interpreted as limiting. Consequently, various alterations, modifications, and/or alternative embodiments and applications may be suggested to those skilled in the art after having read this disclosure. Accordingly, it is intended that the disclosure be interpreted as encompassing all alterations, modifications, or alternative embodiments and applications as fall within the true spirit and scope of this disclosure.