Low profile heat and moisture exchanger device for tracheotomy and speaking valve

Abstract

A heat moisture exchange device received on a speaking tube mounted on an end of a tracheotomy tube. The heat moisture exchange device has a housing in which the air moves in a turbulent manner and passes through a heat moisture exchange filter.

Description

R_os,crit=710√ω′ 4.0≤√ω′≤40.0
R_os,crit=400√ω′ 42.0≤√ω′≤71.0

Thus, the above expressions may be used to ensure that the HME filter includes one or more channels whose dimensions result in supercritical Reynolds number. In one embodiment of this invention, the HME filter is thus designed to operate in a regime where the flow has a supercritical Reynolds number.

In other embodiment of this invention, the critical Reynolds number for a specific design of the HME filter is determined experimentally. For instance, it is well known that when transition to turbulence occurs, the cycle averaged friction factor C_f changes from having an essentially inverse dependence on the Reynolds number, to being essentially Reynolds-number independent. The cycled averaged friction factor may be readily obtained from the instantaneous pressure drop, which may be measured using mechanical or piezoelectric pressure gauges.

Thus, in one embodiment of this invention, a family of prototypes is evaluated. For each prototype the cycle-averaged friction factor is measured, and the measured values are plotted against R_os (FIG. 29). When a logarithmic scale is used, the cycle-averaged friction factor would exhibit a branch with a −1 slope at low Reynolds number, and a second branch that is essentially flat at high Reynolds number. The critical Reynolds number, R_os,crit, may then simply be determined as the intersection of these two branches.

Thus, in one embodiment of this invention, the HME filter is designed to operate in a flow regime where the Reynolds number is above the critical value determined experimentally above.

An effective approach to control the Reynolds number is to consider the effect of the hydraulic diameter, D, on R_os. Specifically, R_os may be related to the flow rate amplitude, Q, the diameter, D, and the kinematic viscosity, ν, by:

$R_{\mathrm{os}}=\frac{Q}{4\pi \mathrm{Dv}}$

Thus, for fixed flow rate amplitude, Q, the Reynolds number increases as D decreases. In other words, the Reynolds number, R_os may be increased by reducing the size of contractions or throats in the HME filter. It should be clear for someone skilled in the art how to extend this approach to achieve similar effects, namely by altering sizes or shapes of HME filters disclosed herein. In testing where Q is a fixed flow amplitude of 0.51/s, D is 4.2 mm and ν is 16 E −06 m²/sec, the device operates at R_os greater than approximately 600. One or more of the flow cross sections has a hydraulic diameter that is less than 5 mm.

This unique dimpled design was evaluated using HME performance tests according to ISO 9360-2: 2009 standard with 3 h runtime and test condition 8 (Vt=500 mL, rate=15/min). The test equipment used was certified and maintained in accordance with industry standards according to ISO 13485.

The design was tested according to these conditions and the results noted. The volume of media contained in this HME was measured. The same volume of media was tested according to the ISO 9360-2:2009 standard, using the same calibrated and certified test equipment, but in a “straight through” configuration per FIG. 22. The same volume of identical foam material was used in the tests.

Percent HME water loss (turbulent flow design):

• • A.1 15 mm Half 16.6 mg/L moisture LOSS=27.4 mg/L moisture RETURNED.
  • A.2 15 mm Half 17.0 mg/L moisture LOSS=27.0 mg/L moisture RETURNED.

Comparison HME media (linear flow design)

• • Linear Sample #1 21.0 mg/L moisture LOSS=23.0 mg/L moisture RETURNED.
  • Linear Sample #2 18.7 mg/L moisture LOSS=25.3 mg/L moisture RETURNED.

Comparing the 23.0 mg/l return of the linear design to the 27.4 mg/l return of the dimple design, the dimpled housing design showed an increase of 19% in efficiency for moisture output to the patient, as compared to the straight through design using identical media volume and test conditions. The only variable in the comparison tests were the shape of the housing. All other conditions were held identical.

This would indicate that the unique shape, with its increased contact time, increased in friction and more complex air currents and eddies resulted in an increase in moisture output. This translates to increased effectiveness and physiological benefit for the patient.

The domed frontal wall 46 provides additional dead space/volume 52 within the small profile of this HME. The dead space affects the cross section of the area through which air flows, and further slows down airflow, hence resulting in enhancement of humidification and heat transfer (FIG. 30).

Air flow is affected by different factors including: 1. the cross-sectional area of the airway (which determines resistance); 2. nature of airflow (turbulent vs. laminar); 3. Reynolds' number (which depends on the density of the media through which air flows); 4. presence of dead space, and 5. the breathing effort by the patient (see below).

In one embodiment of this invention, the HME filter comprises passageways where the cross-sectional area changes rapidly. It is well known that when a stream is forced over such step or expansion, the flow separates which results in the generation of a recirculating region in the wake of the step or expansion region. Recirculating flow regions serve as effective reservoirs of heat and humidity, which benefits the operation of the device and ultimately the patient.

The heat and exchange moisture media preferably consists of reticulated ester-type polyurethane foam with a nominal porosity of 65 ppi (pores per inch). The material is die-cut into a hollow cylinder and subsequently treated with an aqueous solution of pharmaceutical grade calcium chloride. Other hygroscopic materials may be used. The foam is disposed internally in the housing such that air entering or leaving the spaced-apart openings in the housing must pass through the foam.

Having exhaled air from the patient make contact with the HME media is essential to the function of an HME. Because HME filters function only when air from the patient is exhaled across the media, and then returned to the patient, use of an HME is not possible with any of the other unidirectional speaking valves currently on the market, as they do not allow two-way air flow. Prior to this valve design, patients had to choose either to wear a speaking valve for communication and forgo the benefit of an HME filter, or alternatively to wear an HME filter and forgo the benefits of wearing a speaking valve. The novel ball valve's guiding design is unique in a sense that when the housing is in the “notch up” position, the ball sits back toward the retention tabs greatly facilitating air flow inhalation (ball is in “biased-open” position). This position accommodates the use of an HME as follows. Upon exhalation, air is allowed to flow back out through the valve, and through the HME when attached. In this way the patient receives the benefit of the HME filtered air upon inspiration. However, with the valve in this same position, the patient can also choose to have the ball seat and seal, allowing redirection of the exhaled air over the vocal cords, in order to produce speech. This is accomplished simply by providing increased expiratory volume in order to drive the ball forward and vertically up the frontal wall, and into the frontal opening to seat and seal off air flow. When the patient decides to give preferential priority to speech, rather than humidification, all that needs to be done is to rotate the valve 180 degrees and the ball moves forward towards the frontal opening (ball is in “biased-closed” position). This allows the patient to realize the benefits of either speech or humidification (FIG. 8).

Claims

1. A heat moisture exchange device comprising a housing adapted to be received on an end of a tracheotomy tube, wherein exhaled and inhaled air may move into and out of the housing, the housing having a domed frontal wall and circumferential walls depending from the domed frontal wall, a bottom circular panel joined to the circumferential walls, a circular opening formed in the bottom panel, the domed frontal wall having a dimple extending toward the circular opening, a plurality of spaced-apart legs connected to the bottom panel and extending upwardly within the housing toward the domed frontal wall, the legs being substantially parallel to the circumferential walls,

a plurality of spaced-apart openings formed in the circumferential walls, and

a heat and moisture exchange filter mounted within the housing through which air flows, wherein moisture and heat from the exhaled air is transferred to the filter and inhaled air is heated and moisturized by the filter and wherein particulates in the inhaled air are collected by the filter.

2. The heat and moisture exchange device of claim 1,

wherein a speaking valve is mounted on the end of the tracheotomy tube and

the heat moisture exchange device is mounted on the speaking valve

wherein a patient fitted with the tracheotomy tube, the speaking valve and the heat and moisture exchange device may breathe and speak.

3. The heat moisture exchange device of claim 2, wherein the speaking valve comprises:

a plurality of ramps extending upward at an acute angle towards a first end of the speaking valve;

an opening at a second end of the speaking valve, wherein the opening is offset from a central axis extending from the first end to the second end of the valve; and

a ball disposed between the opening and the plurality of ramps, wherein a diameter of the ball is greater than a diameter of the opening.

4. The heat moisture exchange filter of claim 1, wherein the filter is a filter material impregnated with a hygroscopic material.

5. The heat moisture exchange device of claim 1, wherein the filter material is a porous foam having multiple pores, each pore having a nominal pore size of approximately 65 ppi.

6. The heat moisture exchange device of claim 5, wherein the porous foam comprises ester-type polyurethane.

7. The heat moisture exchange device of claim 1, wherein

a the dimple is formed centrally on the domed frontal wall, the dimple being arranged to produce turbulence in movement of air moving within the housing.

8. A method of using the heat moisture exchange device of claim 1 comprising:

with a tracheotomy tube wherein mounting the heat moisture exchange device is mounted on the end of the tracheotomy tube and

controls controlling the temperature and moisture content of the air being inhaled and exhaled through the mounted heat moisture exchange device and the tracheotomy tube.

9. A heat moisture exchange device comprising

a housing adapted to be received on a speaking valve which is mounted on an end of a tracheotomy tube in a patient fitted with the tracheotomy tube, wherein air may move into and out of the housing, the housing having

a domed frontal wall and

circumferential walls depending from the domed frontal wall,

a bottom circular panel joined to the circumferential walls,

a circular opening formed in the bottom panel,

a plurality of spaced-apart legs connected to the bottom panel and extending upwardly within the housing toward the domed frontal wall,

the legs being substantially parallel to the circumferential walls,

a plurality of spaced-apart openings formed in the circumferential walls,

means for modifying air flow disposed within the housing to produce nonlinear turbulent air flow within the housing,

a heat and moisture exchange filter mounted within the housing between the legs and the openings in the circumferentially circumferential walls through which air flows,

wherein moisture and heat from the exhaled air is transferred to the filter and inhaled air is heated and moisturized by the filter and

wherein particulates in the inhaled air are collected by the filter, and

wherein the means disposed within the housing to produce nonlinear turbulent airflow within the housing for modifying air flow is a dimple formed on the domed frontal wall extending towards the circular opening.

10. The heat moisture exchange filter of claim 9, wherein the filter is a filter material impregnated with a hygroscopic material.

11. The heat moisture exchange device of claim 9, wherein

the means to produce nonlinear turbulent air flow within the housing is the dimple is formed centrally on the domed frontal wall.

12. The heat moisture exchange device of claim 9, wherein the turbulence is expressed as

13. The heat moisture exchange device of claim 12, wherein one or more flow cross sections have a hydraulic diameter that is less than 5 mm.

14. A method of using the heat moisture exchange device of claim 9 comprising

with mounting the heat moisture exchange device on the speaking valve, and

tracheotomy tube wherein the heat moisture exchange device controls controlling the temperature and moisture content of the air being inhaled and exhaled through the mounted heat moisture exchange device and the tracheotomy tube and wherein as the patient may breathe and speak breathes and speaks.

15. A heat moisture exchange device comprising:

a housing configured to be received on an end of a tracheotomy tube,

the housing having

a domed frontal wall,

wherein the domed frontal wall has a dimple;

sidewalls extending downward from the domed frontal wall,

wherein the sidewalls are perforated;

a panel connected to a distal portion of the sidewalls;

a plurality of legs extending from the panel toward the domed frontal wall; and

a filter within the sidewalls of the housing;

wherein the dimple is extending extends in the same direction as the sidewalls.

16. The heat moisture exchange device of claim 15, wherein the filter is a porous foam having a plurality of pores, wherein each of the plurality of pores range from 40 ppi to 90 ppi.

17. The heat moisture exchange device of claim 16, wherein the porous foam comprises ester-type polyurethane.

18. The heat moisture exchange device of claim 15, wherein the filter comprises a hygroscopic material.

19. The heat moisture exchange device of claim 15, wherein the filter comprises calcium chloride.

20. The heat moisture exchange device of claim 15, wherein the housing has a diameter of 1 inch.

21. The heat moisture exchange device of claim 2, wherein the speaking valve further comprises:

a body configured for being attached to and rotatable relative to the tracheotomy tube between a biased-closed position and a biased-open position, the biased-open position being 180° offset from the biased-closed position, the body having

a first end configured for communicating with the tracheotomy tube,

a second end distal from the tracheotomy tube configured for communicating with the heat and moisture exchange device,

a cylindrical chamber extending from the second end, and

an opening formed in the second end offset from a central axis of the chamber;

a ball disposed within the chamber, the ball having a diameter greater than the opening; and

a plurality of guides disposed within the cylindrical chamber and arranged for guiding movement of the ball within the chamber between a first position and a second position;

wherein, when the body is rotated to the biased-closed position, the guides have a first region configured and positioned to urge the ball toward and substantially close the opening, and

wherein, in response to a sufficient inhalation flow, the guides have a second region configured and positioned to urge the ball toward a substantially central position within the chamber and thereby define a generally annular flow passage.

22. The heat moisture exchange device of claim 21, wherein,

when the body is rotated to the biased-open position, the guides guide the ball to an offset position within the chamber whereby the opening remains substantially unobstructed, and

wherein, in response to a sufficient inhalation flow, the guides urge the ball toward a substantially rearward position within the chamber.

23. A speaking valve comprising:

a body having

a first end configured for being removably attached to a tracheotomy tube;

a second end configured for receiving a removably attached heat and moisture exchange device,

the body further being rotatable relative to the tracheotomy tube between a biased-closed position and a biased-open position, the biased-open position being 180° offset from the biased-closed position, the body having

a cylindrical chamber extending from the second end, and

an opening formed in the second end offset from a central axis of the chamber;

a ball disposed within the chamber; and

a plurality of guides disposed within the cylindrical chamber and arranged for guiding movement of the ball within the chamber

between a first position and a second position;

wherein, when the body is rotated to the biased-closed position, the guides have a first region configured and positioned to urge the ball toward and substantially close the opening, and

wherein, in response to a sufficient inhalation flow, the guides have a second region configured and positioned to urge the ball toward a substantially central position within the chamber and thereby define a generally annular flow passage.