Patent Publication Number: US-2021178198-A1

Title: Headgear tensioning for respiratory mask

Description:
CROSS REFERENCE TO APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 15/648,580, filed Jul. 13, 2017, now allowed, which is a continuation of U.S. application Ser. No. 11/902,509, filed Sep. 21, 2007, now U.S. Pat. No. 9.744,385, which claims the benefit of Australian Provisional Application No. AU 2006905236, filed Sep. 21, 2006, each of which is incorporated herein by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a headgear assembly for use in holding a patient interface such as a respiratory mask in position on a patient&#39;s face, the patient interface being used in the treatment, e.g., of Sleep Disordered Breathing (SDB) with Non-Invasive Positive Pressure Ventilation (NIPPV). 
     2. Description of Related Art 
     Respiratory mask assemblies for treatment of SDB such as Obstructive Sleep Apnea (OSA) are typically secured to the patient&#39;s head by means of a headgear assembly. 
     Headgear assemblies are structured to position and stabilize a patient interface, such as a nasal mask, on a patient&#39;s face so that a good seal can be maintained. A headgear assembly typically includes a pair of side portions, and a rear portion. The side portions are adapted to engage with the patient&#39;s mask, and the rear portion is adapted to engage the back of the patient&#39;s head. 
     Prior art headgear arrangements typically have side straps typically held in position using hook and loop material, for example VELCRO®, by passing an end of the strap through a loop on the mask—or on a connector which connects to the mask—and then folding it back onto itself. In this way, the strap can be adjusted to adjust the headgear tension and thus the force which the headgear applies to hold the mask against the patient&#39;s face, to suit the particular needs of the patient in order that a comfortable effective mask seal be effected. 
     Correct adjustment of the headgear tension is important to the success of the therapies and to achieving patient compliance with the therapy regime. 
     Currently, patients generally use mask comfort to determine the headgear tension adjustment. However, the time period over which the patient is adjusting the tension is short in comparison with the length of each therapy session, and what feels comfortable over a 5 or 10 minute adjustment period will often be too tight to maintain comfort over an 8 hour therapy session. Also, changes in treatment pressure at the mask may require different headgear tension settings for optimal performance. 
     The ideal headgear tension is the loosest possible to maintain a seal between the mask cushion and the patient&#39;s face. However, it is intuitive for the patient to continue to tighten the headgear straps to seek to eliminate mask leak completely. In some instances, overtightening of the headgear may crush the sealing cushion of the mask and in fact increase the leak. 
     Furthermore, overtightening may cause patient discomfort, marking or creasing of the patient&#39;s face and neck which is visible the next day, and may lead to sores and tissue necrosis. Other possible effects of overtightening include dental and gum impairment, and pressure on the temporomandibular joints causing headaches, increased occurrence of apnea, or a reduction of nasal passage area leading to increased breathing resistance. All of these may make the therapy unpleasant for the patient and may lead to non-compliance with the therapy by the patient. 
     Alternatively, insufficient headgear tension may lead to mask leak by failure to maintain a seal between the mask and the patient&#39;s face, or movement of the mask while the patient sleeps, which may limit the success of the therapy or may wake the patient and lead to the patient discontinuing the therapy. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention relates to a headgear assembly for attachment to a patient interface that delivers breathable gas to a patient such as a respiratory mask to a patient&#39;s face, including 
     a headgear body adapted to fit to the patient&#39;s head and has connection portions adapted for connection to the patient interface, 
     adjustment means for adjusting said headgear, and 
     indicating means responsive to an adjustment parameter of the headgear for indicating attainment of a desired adjustment setting of the headgear. 
     Another aspect of the invention relates to a patient interface adapted to deliver breathable gas to a patient and adapted for attachment to the patient by means of adjustable headgear, including indicating means responsive to an adjustment parameter of the headgear for indicating attainment of a desired adjustment setting of the headgear. 
     Another aspect of the invention relates to a headgear assembly for attachment to a patient interface that delivers breathable gas to a patient, including: 
     a headgear body adapted to fit to the patient&#39;s head and having connection portions adapted for connection to the patient interface; 
     an adjustment mechanism to adjust the headgear body, and 
     a limiter to limit tightening adjustment of the headgear body. 
     Another aspect of the invention relates to a headgear assembly for attachment to a patient interface that delivers breathable gas to a patient, including: 
     a headgear body adapted to fit to the patient&#39;s head and having connection portions adapted for connection to the patient interface, 
     an adjustment mechanism to adjust the headgear body, and 
     a control mechanism to control adjustment of headgear tension. 
     Another aspect of the invention relates to a method for controlling adjustment of headgear. The method includes adjusting the headgear and visually indicating attainment of a desired adjustment setting of the headgear. 
     Another aspect of the invention relates to a connector arrangement for a patient interface. The connector arrangement includes a connector provided to a mask and a clip provided to headgear. The clip is adapted to connect to the connector in a multiple stage arrangement such that release of the clip from one stage to an adjacent stage indicates attainment a desired headgear tension. 
     Another aspect of the invention relates to headgear for a patient interface. The headgear includes at least one headgear strap and an indicator provided to the at least one headgear strap structured to indicate attainment of a desired adjustment setting of the headgear in response to headgear tension applied to the at least one headgear strap. 
     Another aspect of the invention relates to a connector arrangement for a patient interface. The connector arrangement includes a connector provided to a mask and a clip provided to headgear. The clip is adapted to connect to the connector such that excessive tension applied to the clip allows the clip to completely release from the connector. 
     Another aspect of the invention relates to a method for controlling headgear tension. The method includes connecting headgear straps of headgear to a mask and releasing tension upon application of excessive tension force to the headgear straps. 
     Further aspects of the invention relate to a patient interface and headgear combination, and a method of controlling adjustment of a headgear for a patient interface. 
     Other aspects, features, and advantages of this invention will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, which are a part of this disclosure and which illustrate, by way of example, principles of this invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings facilitate an understanding of the various embodiments of this invention. In such drawings: 
         FIG. 1  is a front perspective view of a prior art MIRAGE® full face headgear and mask arrangement; 
         FIG. 2  is the MIRAGE® headgear arrangement of  FIG. 1  when laid flat; 
         FIG. 3  is a schematic view of a set of visible indicia for indicating the headgear tension according to one embodiment of the invention; 
         FIGS. 4A and 4B  are schematic views of visual indicia indicating attainment of the desired headgear tension according to another embodiment of the invention; 
         FIG. 5  shows a necking portion on the headgear according to another embodiment of the invention; 
         FIGS. 6A to 6C  show a further embodiment of the invention using relative movement between an underlying and overlying portion of the headgear to indicate adjustment; and 
         FIGS. 7A to 7D  show a clip and catch arrangement according to a further embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS 
       FIG. 1  shows the Applicant&#39;s prior art MIRAGE® full face mask  100  and headgear  102  according to the Applicant&#39;s PCT Application WO 02/47749, which is incorporated herein by reference in its entirety. 
     The mask  100  is connected to a positive airway pressure (PAP) device or flow generator device (not shown) which provides breathable gas to the mask for treatment of sleep apnea. 
     As shown in  FIG. 2 , the headgear  102  is constructed from a composite of polyurethane foam, loop material and hook material whose shape includes a pair of upper straps  20  and lower straps  30  and a generally triangular back portion  40 . A piece of hook material  22  (e.g., such as Velcro®) is attached to the end of each of the four straps so that the straps may be secured to attachment points on the mask  100 . 
     The hook material  22  may be ‘one way’ hook material so that it does not catch on itself in the process of overlaying the straps before they are brought into engagement. 
     In other, unillustrated, prior art arrangements, the straps  20 ,  30  may be adapted to fit to a male clip connector which clips into a female connector moulded into the mask frame of mask  100 . 
       FIG. 3  shows a set of visible indicia  40  which may be printed onto or otherwise formed on the headgear  102 , e.g., on the side straps  20 ,  30  or elsewhere on the headgear which is visible to the wearer in a mirror. 
     The indicia  40  comprise a set of ellipses of successively greater aspect ratios, having vertical major axes. The indicia  40  may be labelled with tension settings, e.g., 1, 2, 3, 4, etc. In an embodiment, the indicia may be labelled in mirror image so that they are readable by the wearer in the mirror. It should be appreciated that any suitable number of ellipses may be provided, and the ellipses may be spaced apart from one another in any suitable manner to indicate the setting. 
     In one alternative form of this embodiment, the setting labels may indicate treatment pressures for which the corresponding headgear adjustment setting is recommended. 
     As the headgear strap (e.g., strap  20  of headgear  102 ) is placed under tension by tightening of the headgear (tension indicated by arrows), the headgear material stretches in the direction normal to the ellipse axes and the ellipses become more circular. As the tension increases, first one then the next ellipse become approximately circular, with the most circular ellipse indicating the tension setting. The wearer adjusts the headgear until the desired tension setting is reached. That is, ellipse  1  will become circular as tension is initially applied, ellipse  2  will become circular as more tension is applied, etc., with ellipse  4  becoming circular at the highest tension setting. 
     In a further embodiment shown in  FIGS. 4A and 4B , the indicia  140  are formed on the side straps  20 , 30  by printing on the underlying material of the headgear which is covered by a top layer. When the headgear is not tensioned, the indicia  140  are obscured by the top layer ( FIG. 4A ), but when the desired headgear tension is reached the material of the top layer becomes see-through and the indicia  140  become visible ( FIG. 4B ). 
     In an embodiment shown in  FIG. 5 , the headgear straps  20 , 30  may include a necked portion  240  which narrows as the headgear tension is increased, and markings  250  may be provided adjacent the necked portion  240  for assessing the headgear tension. For example, the markings  250  provide a reference for how narrow the necked portion  240  becomes upon tension. 
       FIGS. 6A to 6C  illustrate a further embodiment of indicia  260  on the headgear, in the form of a series of numerals or other symbols indicating adjustment settings. The headgear also has a cover flap  270  attached to the surface of the headgear strap (e.g., strap  20 ) along a fold line  280 . The flap obscures the indicia  260  when the headgear is untensioned ( FIG. 6A ). The headgear material stretches as tension is applied (tension indicated by arrows), with the relative movement between the indicia  260  and the cover flap  270  causing the indicia  260  (e.g., numerals such as 1, 2, 3, etc.) progressively being uncovered as the tension increases. The highest value uncovered numeral indicates the adjustment setting of the headgear. That is, the numeral  1  is uncovered as tension is initially applied ( FIG. 6B ), numeral  2  is uncovered as more tension is applied ( FIG. 6C ), etc., with the highest numeral becoming uncovered at the highest tension setting. 
     In a further unillustrated embodiment, the indicia may comprise an contact pressure film located between the rim and cushion of the mask, which changes colour with changes to the pressure on the seal as the headgear is tightened or otherwise adjusted. The film may provide an indication of excessive pressure between the mask rim and the seal, and the dispersion of that pressure. Examples of suitable contact pressure films include Pressurex tactile force indicating films from Sensor Products Inc of USA., and FilmLOC colour changing PET film from Austik Technologies of USA. 
     Further headgear tension sensing means may include electrical sensors such as strain gauges or capacitance sensors which vary capacitance depending on the distance between the capacitor plates. The sensor readings are fed back to the flow generator, the processor of which is programmed with an algorithm for converting the signal into a tension setting for display on the flow generator display, and/or to provide an audible or visible signal when the desired headgear tension is reached. 
     Further aspects of the invention relate to tightening mechanisms for adjustment of the headgear tension. 
     In one embodiment, the side straps  20 , 30  may be connected to the mask by means of connectors which clip onto the mask frame of mask  100 . The connection between the mask and the headgear connectors is adapted to provide a visual, tactile or audible signal on reaching the desired tension, and/or to release when the desired tension is exceeded. 
       FIGS. 7A to 7D  schematically illustrate the operation of a clip  300  provided to side straps  20 , 30  of the headgear and a connector  330  provided to the mask frame of mask  100 , according to one embodiment of the invention. 
     The connector  330  (in the form of a female connector or clip receptacle) on the mask frame has a pair of opposed sides  332  each with inward projections  334  having a sloping front surface  336  and a more upright rear surface  338 . 
     The clip  300  has a body  302  and a pair of spring arms  304  with outward projections, i.e., front projection  306  and centre projection  308  which form two recesses  310 ,  312  for receiving the projections  334  of the connector  330 . 
     The clip connection comprises a two stage latch arrangement in which the clip  300  clicks into the connector  330  on the mask in a first stage connection in which the clip travels from the position of  FIG. 7A  to that in  FIG. 7D . The clip will provide two audible and/or tactile clicks, i.e., one as it moves from the position of  FIG. 7B to 7C  and another when moving from the position of  FIG. 7C  to  FIG. 7D . 
     For example, the clip  300  is engaged with connector  330  so that the sloping front surface  336  of the inward projections  334  engage the front projections  306  to flex the spring arms  304  inwardly towards the body  302  until the front projections  306  move past the inward projections  334  and into the position of  FIG. 7C . As illustrated, the spring arms  304  resiliently return to its initial position so that the inward projections  334  extend into the recess  310  and the front projections  306  are retained by the rear surface  338 . Further movement of the clip  300  into the connector  330  causes the center projection  308  to ride over the inward projections  334  and into the position of  FIG. 7D , in which the inward projections  334  extend into the recess  312 . 
     The user then starts to tighten the headgear using the hook and loop tabs on the side straps  20 , 30 . As the user continues to tighten the headgear, the desired tension is reached and the spring arms  304  flex inwards so that the centre projections  308  ride past the projections  334  of the connector and the clip releases to the position of  FIG. 7C , emitting an audible ‘click’ or other cue for the user to stop tightening the headgear. The user therefore knows that the appropriate headgear tension has been reached and may then fasten the hook material tabs to fix the headgear in this adjustment setting. 
     The release tension for which the clip is designed may be controlled by varying the stiffness of the spring arms  304  and the face angle and height of the centre projections  308 . 
     Optionally, the clip connectors may be interchangeable for similar clips having different release tensions, so that the headgear tension, may be varied according to the treatment pressure and the patient&#39;s requirements or preferences. 
     In an embodiment, the clip and connector may be structured such that excessive tension applied to clip allows the clip to completely release from the connector. This quick release arrangement allows the patient to quickly remove the mask without manually flexing the spring arms, e.g., for emergency situation, panic situation, claustrophobia, to prevent excessive tension applied to the straps, which could be uncomfortable or even be harmful to the patient, etc. The release force may be controlled, e.g., by varying the stiffness of the spring arms, the face angle of the rear surface  338  of the inward projections  334 , and/or the face angle of the rear surface of the front projections  306  (i.e., the surface of the front projection  306  adapted to face and/or engage the rear surface  338  when the clip is coupled to the connector). This quick release arrangement may be used with the multiple stage arrangement discussed above, or this quick release arrangement may be used independently. 
     Further tightening mechanisms according to embodiments of the invention include the use of piezo materials or artificial muscles (e.g., devices which contract lengthwise upon activation, for example of the types used in robotic control systems) incorporated into the rear or side portions of the headgear. 
     One example of a suitable artificial muscle apparatus is one or more pneumatic muscles incorporated into the headgear, i.e., tubular portions which contract lengthwise upon inflation, which may be inflated by air pressure from the flow generator. Examples of suitable air muscles include the Shadow Air Muscles available from Shadow Robot Company Ltd of UK and described at the website http://www.shadowrobot.com/airmuscles. 
     Alternative artificial muscle apparatus which may be employed include electro-active polymers (EAPs) which contract upon application of electrical energy. Suitable electro-active polymers may include electronic or ionic, with electronic EAPs being preferred due to ability to hold strain with DC activation and their relatively high actuation forces. Examples of electronic EAPs include ferroelectric polymers such as poly(vinylidene fluoride), dielectric EAPs having low elastic stiffness and high dielectric constants (also known as electrostatically stricted polymers or ESSPs), electrostrictive graft elastomers, electrostrictive papers, electro-viscous elastomers or liquid crystal elastomer (LCE) materials. Examples of ionic EAPs include ionic polymer gels, ionomeric polymer-metal composites, conductive polymers or carbon nanotubes. Further discussion of each of these types of EAPs may be found in the article “ElectroActive Polymers—EAPs” at the website “The A to Z of Materials”, by Dr. Yoseph Bar-Cohen, at www.azom.com/details.asp?ArticleID=885, the contents of which article are incorporated herein by reference. 
     A yet further automated headgear adjustment mechanism includes a magnetic adjustment mechanism, for example by varying the distance between magnets of constant field strength, such as permanent magnets, or by varying the field strength of electromagnetic apparatus. 
     A further headgear adjustment mechanism includes a bladder mounted on or incorporated in the headgear, or a plurality of such bladders at different locations on the headgear, inflatable to increase the headgear tension. In one exemplary form, the bladder or bladders are inflated by air delivered by the flow generator. In one embodiment, the bladder or bladders are formed by comoulding with the material of the headgear. 
     In this specification, the word “comprising” is to be understood in its “open” sense, that is, in the sense of “including”, and thus not limited to its “closed” sense, that is the sense of “consisting only of”. A corresponding meaning is to be attributed to the corresponding words “comprise, comprised and comprises where they appear. 
     While the invention has been described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention. Also, the various embodiments described above may be implemented in conjunction with other embodiments, e.g., aspects of one embodiment may be combined with aspects of another embodiment to realize yet other embodiments. Further, each independent feature or component of any given assembly may constitute an additional embodiment. In addition, while the invention has particular application to patients who suffer from OSA, it is to be appreciated that patients who suffer from other illnesses (e.g., congestive heart failure, diabetes, morbid obesity, stroke, bariatric surgery, etc.) can derive benefit from the above teachings. Moreover, the above teachings have applicability with patients and non-patients alike in non-medical applications.