U.S. patent application number 11/920100 was filed with the patent office on 2009-01-29 for nasal cannula.
Invention is credited to Martin Baecke, Silvio Kilz, Heiko Krause, Ingo Muller, Ulla Schobel.
Application Number | 20090025723 11/920100 |
Document ID | / |
Family ID | 36127291 |
Filed Date | 2009-01-29 |
United States Patent
Application |
20090025723 |
Kind Code |
A1 |
Schobel; Ulla ; et
al. |
January 29, 2009 |
Nasal cannula
Abstract
The invention relates to a nasal cannula for an anti-snoring
apparatus, comprising a forked tube pneumatically connected to
apertures, which are embodied and positioned in such a way that air
can be administered into the nose of a user via these apertures.
The nasal cannula further comprises a heating wire extending in the
interior of forked tube in such a way that the heating wire can
heat the air supplied through the forked tube. The invention
moreover relates to a nosepiece and to a Y-shaped element for nasal
cannula including internal radius steps at tube connection points.
The invention further relates to a nosepiece and to a Y-shaped
element having rounded off transition regions. The invention
finally relates to a method for avoiding condensation in nasal
cannulas. To this end, the gas is heated as it flows through the
tubes of a nasal cannula.
Inventors: |
Schobel; Ulla; (Koethen,
DE) ; Kilz; Silvio; (Graefenhainichen, DE) ;
Muller; Ingo; (Dessau, DE) ; Baecke; Martin;
(Dessau, DE) ; Krause; Heiko; (Dessau,
DE) |
Correspondence
Address: |
LAW OFFICES OF CLEMENT CHENG
17220 NEWHOPE STREET #127
FOUNTAIN VALLEY
CA
92708
US
|
Family ID: |
36127291 |
Appl. No.: |
11/920100 |
Filed: |
December 30, 2005 |
PCT Filed: |
December 30, 2005 |
PCT NO: |
PCT/DE2005/002335 |
371 Date: |
April 11, 2008 |
Current U.S.
Class: |
128/204.17 ;
128/207.18 |
Current CPC
Class: |
A61M 2205/3653 20130101;
A61M 2205/42 20130101; A61M 16/0808 20130101; A61M 2205/3372
20130101; A61M 16/0833 20140204; A61M 16/0666 20130101; A61M
16/1095 20140204 |
Class at
Publication: |
128/204.17 ;
128/207.18 |
International
Class: |
A61M 16/06 20060101
A61M016/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 7, 2005 |
DE |
102005000922.0 |
Claims
1. A nasal cannula for an anti-snoring or PAP apparatus,
comprising: a forked tube (3) pneumatically connected to apertures
(12; 52), which are embodied and positioned in such a way that air
can be administered into the nose of a user via these apertures
(12; 52), characterized by: a heating wire (8, 31, 33) extending in
the forked tube (3) in such a way that the heating wire (8) can
heat the air supplied through the forked tube (3).
2. The nasal cannula according to claim 1, wherein a temperature
sensor (7) is mounted in the proximity of the apertures (12; 52) so
that the temperature sensor (7) can measure the temperature of the
air administered via the apertures (12; 52).
3. The nasal cannula according to claim 2, wherein the temperature
sensor (7) is connected to the heating wire (8) in such a way that
it can be supplied with electric energy via the heating wire (8)
and that the temperature signal of the temperature sensor (7) can
also be read out via the heating wire (8).
4. The nasal cannula according to claim 3, wherein the temperature
sensor (7) is a digital temperature sensor modulating its
temperature signal onto the voltage supplied to the temperature
sensor (7) via the heating wire (8).
5. The nasal cannula according to claim 1, wherein the heating wire
(8) has a wire-shaped metal core (21) surrounded by an insulation
(22), the external shell of which comprises elevations and
recesses.
6. The nasal cannula according to claim 1, wherein the heating wire
(8) has a wire-shaped metal core (21) surrounded by an insulation
(22), the external shell of which comprises elevations and
recesses, wherein a temperature sensor (7) is mounted in the
proximity of the apertures (12; 52) so that the temperature sensor
(7) can measure the temperature of the air administered via the
apertures (12; 52).
7. The nasal cannula according to claim 1, wherein the heating wire
(8) has a wire-shaped metal core (21) surrounded by an insulation
(22), the external shell of which comprises elevations and
recesses, wherein the temperature sensor (7) is a digital
temperature sensor modulating its temperature signal onto the
voltage supplied to the temperature sensor (7) via the heating wire
(8).
8. The nasal cannula according to claim 1, wherein the heating wire
(8) has a wire-shaped metal core (21) surrounded by an insulation
(22), the external shell of which comprises elevations and
recesses, wherein the shell of the insulation (22) includes
elevations with triangular cross-sections which extend
approximately in the longitudinal direction of the heating wire
(8), so that the insulation (22) has altogether a star-shaped
cross-section.
9. The nasal cannula according to claim 1, wherein the heating wire
(8) has a wire-shaped metal core (21) surrounded by an insulation
(22), the external shell of which comprises elevations and
recesses, wherein the metal core (21) includes elevations and
recesses on its shell.
10. The nasal cannula according to claim 1, wherein the forked tube
(3) comprises stabilizing filaments (31, 33).
11. The nasal cannula according to claim 1, characterized in that
two elements of the forked tube (3) are mechanically connected to a
double-lumen tube (13) at a connector-sided end.
12. The nasal cannula according to claim 1, wherein the forked tube
(3) is pneumatically connected to a pneumatic connector part (10)
of a connector (6) and wherein the heating wire (8) is electrically
connected to an electrical connector part (9) of the connector
(6).
13. The nasal cannula according to claim 1, wherein the apertures
are formed by prongs (12, 52) approximately in the center of a
nosepiece (2, 42), wherein a left element of the forked tube (3) is
pneumatically connected to the left side of the nosepiece (2, 42)
and a right element of the forked tube (3) is pneumatically
connected to the right side of the nosepiece (2, 42) and the
heating wire (8, 31, 33) extends from the left element of the
forked tube (3) through the interior of the nosepiece (2, 42) to
the right element of the forked tube (3).
14. The nasal cannula according to claim 1, characterized in that
two elements of the forked tube (3) are mechanically connected to a
double-lumen tube (13) at a connector-sided end, wherein the forked
tube (3) is pneumatically connected to a pneumatic connector part
(10) of a connector (6) and wherein the heating wire (8) is
electrically connected to an electrical connector part (9) of the
connector (6), wherein the apertures are formed by prongs (12, 52)
approximately in the center of a nosepiece (2, 42), wherein a left
element of the forked tube (3) is pneumatically connected to the
left side of the nosepiece (2, 42) and a right element of the
forked tube (3) is pneumatically connected to the right side of the
nosepiece (2, 42) and the heating wire (8, 31, 33) extends from the
left element of the forked tube (3) through the interior of the
nosepiece (2, 42) to the right element of the forked tube (3).
15. The nasal cannula according to claim 1, wherein the forked tube
(3) comprises stabilizing filaments (31, 33), wherein two elements
of the forked tube (3) are mechanically connected to a double-lumen
tube (13) at a connector-sided end.
16. The nasal cannula according to claim 1, wherein the heating
wire (8) has a wire-shaped metal core (21) surrounded by an
insulation (22), the external shell of which comprises elevations
and recesses, wherein the metal core (21) includes elevations and
recesses on its shell, wherein the forked tube (3) comprises
stabilizing filaments (31, 33).
17. The nasal cannula according to claim 1, wherein a temperature
sensor (7) is mounted in the proximity of the apertures (12; 52) so
that the temperature sensor (7) can measure the temperature of the
air administered via the apertures (12; 52), wherein the
temperature sensor (7) is connected to the heating wire (8) in such
a way that it can be supplied with electric energy via the heating
wire (8) and that the temperature signal of the temperature sensor
(7) can also be read out via the heating wire (8), wherein the
temperature sensor (7) is a digital temperature sensor modulating
its temperature signal onto the voltage supplied to the temperature
sensor (7) via the heating wire (8).
18. A nasal cannula having a nosepiece for an anti-snoring or PAP
apparatus, comprising: a forked tube (3) pneumatically connected to
apertures (12; 52), which are embodied and positioned in such a way
that air can be administered into the nose of a user via these
apertures (12; 52), characterized by: a heating wire (8, 31, 33)
extending in the forked tube (3) in such a way that the heating
wire (8) can heat the air supplied through the forked tube (3)
further comprising a nosepiece for a nasal cannula comprising: a
connection point (44) for mounting a forked tube (3); wherein the
connection point includes an internal radius step (46) at one end
of the connection point (44) the height of which just about
corresponds to half the difference between the inner and outer
diameter of the forked tube (3) so as to obtain an even transition
between the interior of the forked tube (3) and the interior of the
nosepiece upon mounting a forked tube (3) at the connection point
(44).
19. The nasal cannula having a nosepiece of claim 18, for nasal
cannulas, further comprising: a prong (12; 52) for administrating
air into a nostril of a user; a connection point (44) for mounting
a forked tube (3); and a connection piece (47) which mechanically
and pneumatically connects the prong (12; 52) to the connection
point (44), characterized in that the transition region (54)
between the prong (12; 52) and the connection piece (47) has a
radius in a plane which is defined by the prong and the connection
piece (47), the radius being larger than the radius of the prong
(12; 52).
20. The nasal cannula having a nosepiece of claim 19, further
comprising: two prongs (12; 52) for administrating air into each
nostril of a user; a central connection piece (48) which
mechanically and pneumatically connects the two prongs (12; 52);
two tube connections (44); and two connection pieces (47), wherein
each connection piece mechanically and pneumatically connects one
prong (12; 52) to one tube connection (44); characterized in that;
the central connection piece (48) includes an indentation (43) so
that the area of the clear cross-section of the central connection
piece (48) is smaller than the area of the clear cross-sections of
the two connection pieces (47).
21. For nasal cannula having a nosepiece of claim 18, further
comprising: two prongs (12; 52) for administrating air into each
nostril of a user; a central connection piece (48) which
mechanically and pneumatically connects the two prongs (12; 52);
two tube connections (44); and two connection pieces (47), wherein
each connection piece mechanically and pneumatically connects one
prong (12; 52) to one tube connection (44); characterized in that
the central connection piece (48) includes an indentation (43) so
that the area of the clear cross-section of the central connection
piece (48) is smaller than the area of the clear cross-sections of
the two connection pieces (47).
22. The nasal cannula having a nosepiece according to claim 21, for
nasal cannulas, comprising: two prongs (12; 52) for administrating
air into each nostril of a user; a central connection piece (48)
which mechanically and pneumatically connects the two prongs (12;
52); characterized in that the transition region between the
central connection piece (48) is rounded off in a plane which is
defined by the two prongs (12; 52), wherein the radius of this
transition region is larger than the radius of the prongs.
23. A nasal cannula having a nosepiece according to claim 18, for
nasal cannulas, further comprising: two prongs (12; 52) for
administrating air into each nostril of a user; a central
connection piece (48) which mechanically and pneumatically connects
the two prongs (12; 52); characterized in that the transition
region between the central connection piece (48) is rounded off in
a plane which is defined by the two prongs (12; 52), wherein the
radius of this transition region is larger than the radius of the
prongs.
24. A nasal cannula having a Y-shaped element for an anti-snoring
or PAP apparatus, comprising: a forked tube (3) pneumatically
connected to apertures (12; 52), which are embodied and positioned
in such a way that air can be administered into the nose of a user
via these apertures (12; 52), characterized by: a heating wire (8,
31, 33) extending in the forked tube (3) in such a way that the
heating wire (8) can heat the air supplied through the forked tube
(3) further comprising a Y-shaped element for nasal cannulas
comprising: two forked tube connections (91); and a supply tube
connection (93), the Y-shaped element mechanically and
pneumatically connecting all three tube connections, characterized
in that each of the two forked tube connections (91) includes an
internal radius step (92) at one end of the forked tube connection
(91) the height of which just about corresponds to half the
difference between the inner and outer diameter of the forked tube
(3) so as to obtain an even transition between the interior of the
forked tube (3) and the interior of the Y-shaped element (4) upon
mounting a forked tube (3) at a forked tube connection (91).
25. A nasal cannula having a Y-shaped element according to claim
24, characterized in that the supply tube connection (93) includes
an internal radius step (94) at one end of the supply tube
connection (93) the height of which just about corresponds to half
the difference between the inner and outer diameter of the supply
tube (5) so as to obtain an even transition between the interior of
the supply tube (5) and the interior of the Y-shaped element (4)
upon mounting a supply tube (5) at the supply tube connection
(93).
26. A nasal cannula having a Y-shaped element according to claim
25, characterized in that the transition region (95) is rounded off
between the two forked tube connections (91) in the interior of the
Y-shaped element (4), wherein the radius in this transition region
(95) in a plane which is defined by the two forked tube connections
(91) is larger than a tenth of the clear cross-section of a forked
tube connection (91).
27. A nasal cannula having a Y-shaped element according to claim
24, characterized in that the transition region (95) is rounded off
between the two forked tube connections (91) in the interior of the
Y-shaped element (4), wherein the radius in this transition region
(95) in a plane which is defined by the two forked tube connections
(91) is larger than a tenth of the clear cross-section of a forked
tube connection (91).
28. A method for avoiding condensation in nasal cannulas,
comprising the steps of: supplying (6) a gas to the nasal cannula;
administrating the gas through apertures (12; 52) in the nasal
cannula; and heating (8) the gas as it flows through the tubes of
the nasal cannula.
29. The method according to claim 28, further comprising the steps
of: measuring (7) the temperature in the proximity of the apertures
(12; 52) for administrating the gas; and controlling the heating
power so as to avoid a condensation in the nasal cannula.
30. The method according to claim 28, further comprising the steps
of: incorporating a temperature sensor (7), which measures the
temperature in the proximity of the apertures (12; 52), is supplied
via heating wires (8) with electric energy for heating the gas and
that the heating wires (8) are used to transmit the sensor
signal.
31. The method according to claim 28, further comprising the step
of: measuring (7) the temperature in the proximity of the apertures
(12; 52) for administrating the gas; and controlling the heating
power so as to avoid a condensation in the nasal cannula.
32. The method according to claim 28, further comprising the steps
of: incorporating a temperature sensor (7), which measures the
temperature in the proximity of the apertures (12; 52), is supplied
via heating wires (8) with electric energy for heating the gas and
that the heating wires (8) are used to transmit the sensor signal;
measuring (7) the temperature in the proximity of the apertures
(12; 52) for administrating the gas; and controlling the heating
power so as to avoid a condensation in the nasal cannula.
Description
[0001] This application claims priority from PCT application
PCT/DE2005/002335 having publication number WO 2006/072231 entitled
Air Glasses, Nosepiece, Y-Shaped Element And Corresponding Method
by inventors BAUER, KILZ, and MULLER. This application is a
national phase application of international application number
PCT/DE2005/002335 (publication number: WO 2006/072231 A2) filed on
Dec. 30, 2005 and entitled AIR GLASSES, NOSEPIECE, Y-SHAPED ELEMENT
AND CORRESPONDING METHOD and claims the benefit of the
above-mentioned international application and the corresponding
German national patent application number 10 2005 000 922.0 filed
on Jan. 7, 2005 and entitled LUFTBRILLE, NASENSTUCK, Y-STUCK SOWIE
VERFAHREN the contents of which are expressly incorporated herein
by reference.
FIELD OF THE INVENTION
[0002] The invention relates to wearable respiration devices, more
specifically to air glasses apparatus, nasal cannula, nosepiece,
Y-shaped element and corresponding method. Specifically, the
invention relates to constructive modifications to facilitate the
use of nasal cannulas for pneumatically splinting the upper
respiratory tract.
DISCUSSION OF RELATED ART
[0003] Obstructive respiratory disorders lead to apneas
(respiratory arrest) making the sleeping person wake up. Frequent
apneas prevent the sleeping person from falling into the restful
deep sleep. Persons suffering from apneas during sleep are,
therefore, tired in the daytime, which may result in social
problems at the workplace and, in the worst case, in fatal
accidents, e.g. of professional drivers.
[0004] Apparatus for performing the CPAP (continuous positive
airway pressure) therapy are known from the prior art. The CPAP
therapy is described in more detail in Chest. Vol. 110, pages 1077
to 1088, October 1996 and in Sleep, Vol. No. 19, pages 184 to
188.
[0005] In the CPAP therapy the patient is supplied with a constant
positive pressure via a nose mask so as to splint the upper
respiratory tract. The correct choice of the positive airway
pressure ensures that the upper respiratory tract remains fully
opened during the whole night, so that no obstructive respiratory
disorders will occur. Bi-level apparatus were developed, inter
alia, to increase the comfort, which reduce the pressure during the
respiratory break. The term PAP apparatus is here used as generic
term for apparatus that pneumatically splint the upper respiratory
tract.
[0006] Snoring and apneas may have one and the same cause, that is,
too slack a palatal and tongue tissue.
[0007] Moreover, oxygen cannulas for the oxygen treatment are known
from the prior art. The oxygen cannulas are used to provide the
patient with air having an increased partial pressure of oxygen
(>210 mbar) or pure oxygen through the nose. An oxygen treatment
takes place, for example, in the case of acute or chronic hypoxemia
as a result of respiratory or cardiac/circulatory disorders
(myocardial infarction, shock) or certain poisonings, e.g. through
carbon monoxide, carbon dioxide, illuminating gas or smoke.
[0008] The use of oxygen cannulas in an anti-snoring apparatus is
known from WO 02/062413 A2 (HEW01). In this connection, oxygen
cannulas are designated as nasal cannulas.
[0009] Vapotherm 2000i is a humidifying system, which delivers
airflows in the range of 8 to 40 l/min via a nasal cannula to
patients. The delivered air is humidified and heated. Air may be
accumulated with oxygen.
[0010] It is the object of the invention to provide a nasal
cannula, a nosepiece, a Y-shaped element as well as a method, which
are specifically well suited to pneumatically splint the upper
respiratory tract.
SUMMARY OF THE INVENTION
[0011] The heating of a forked tube by means of a heating wire can
prevent the condensation of humidity in the forked tube. A laying
of the heating wire in the interior of the forked tube is simple
under the aspect of production engineering. Because of the heat
release to the ambiance of the forked tube the temperature in the
forked tube drops approximately linearly with the distance from the
compressor. This temperature drop may be compensated by a constant
heating power per unit of length, such as one generated by the
heating wire. In dependence on the construction of the tube the
necessary heating power can be kept under 15 watt for the entire
nasal cannula. In other cases, legal provisions would demand the
use of fire-retarding plastics, which are generally not
biocompatible and the use of which in medical engineering products
is therefore problematical.
[0012] A temperature measurement of the administered air allows to
control the heating power of a heating wire or a heater in a
compressor casing in such a way that the temperature is comfortable
for the user. Without a compensation of the temperature drop in the
forked tube the application apertures in the prongs would be the
coldest spots. Consequently, this is where humidity is condensed
most. For this reason, a control of the heating power based on a
temperature measurement in the proximity of the application
apertures is suited best to prevent a condensation in the entire
nasal cannula.
[0013] For reasons of material saving it is desirable that the
temperature sensor be read out via the heating wire. Due to the
progress made in the integration of circuits it is possible to
produce digital temperature sensors of an acceptable size, which
modulate their sensor signal onto the heating wire.
[0014] The deviation of the outer shell of the insulation of the
heating wire from the usual cylindrical shape due to elevations and
recesses prevents too strong a reduction of the airflow through the
forked tube if the forked tube is kinked. In such a case there is
the danger that the heating wire is overheated at the kink site and
melts into the forked tube because of the insufficient cooling of
the heating wire at the kink site.
[0015] If the forked tube is kinked, elevations and recesses
extending along the heating wire are particularly suited to ensure
a sufficient airflow. A triangular cross-section of the elevations
advantageously provides that the contact surface between the
insulation of the heating wire and the inside of the forked tube is
kept small during both normal operation and kinking. The overall
star-shaped cross-section of the insulation advantageously enlarges
the surface of the insulation and thus provides for a reduction of
the thermal resistance between the insulation and the air flowing
past.
[0016] Also projections extending in the longitudinal direction of
the forked tube advantageously make sure that there is a sufficient
airflow, inter alia, for cooling the heating wire, even if the
forked tube is kinked.
[0017] Stabilizing wires serve to reduce a longitudinal expansion
of the tubes.
[0018] The mechanical connection of two elements of the forked tube
at their connector-sided end allows the saving of a Y-shaped
element or the integration of the same in the connector. This
advantageously results in a reduction of the sound emission because
the Y-shaped element integrated in the connector is farther away
from the application apertures.
[0019] Internal radius steps at different connection points can
just about compensate the thickness of the tube, so that the
transition between the tube and the corresponding component is even
upon fixing the tube. An even transition is subject to fewer whirls
and, thus, to less sound.
[0020] Also, the transition regions between a prong and the central
connection piece as well as between a prong and the connection
piece on the side of the prong are rounded off so as to
advantageously prevent the formation of whirls and, thus, an
emission of noise.
[0021] An indentation in the central connection piece allows the
adjustment of an optimum flow resistance of the connection
piece.
[0022] A preferred embodiment of the invention will be explained in
more detail below with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 shows a nasal cannula according to the invention,
comprising a first embodiment of a nosepiece.
[0024] FIG. 2 shows a Y-shaped element comprising a temperature
sensor.
[0025] FIG. 3 shows a nasal cannula according to the invention
comprising a double-lumen tube.
[0026] FIG. 4 shows a temperature measurement circuit.
[0027] FIG. 5 shows the cross-section of a heating wire.
[0028] FIG. 6 shows the cross-section of a tube comprising a
heating wire.
[0029] FIG. 7 shows a perspective view of a second embodiment of a
nosepiece from a first direction.
[0030] FIG. 8 shows a section through a prong along Z-Z.
[0031] FIG. 9 shows a perspective view of the second embodiment of
the nosepiece from a second direction.
[0032] FIG. 10 shows a section along M-M.
[0033] FIG. 11 shows a perspective view of the second embodiment of
the nosepiece from a third direction.
[0034] FIG. 12 shows a Y-shaped element for nasal cannulas
according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0035] FIG. 1 shows a nasal cannula 1 according to the invention,
comprising a first embodiment of a nosepiece 2. The nose piece 2 is
supplied with compressed air via a forked tube 3, a Y-shaped
element 4, a supply tube 5 and a connector 6. The nosepiece 2
includes two prongs 12 for administrating air into both nostrils of
a user. Internal radius steps 16 compensate the difference between
the internal and external radius of the forked tubes, thereby
preventing abrupt changes to the cross-section of the airways.
[0036] The connector 6 comprises a pneumatic connector part 10, an
electrical connector part 9 as well as a clamp 11. From the
electrical connector part 9 a heating wire 8 is passed through the
supply tube 5, the Y-shaped element 4, the right element of the
forked tube 3, the right part of the nosepiece 2 to a temperature
sensor 7, and from there through the left part of the nosepiece 2,
the left element of the forked tube 3, the Y-shaped element 4 and
the supply tube 5 back to the electrical connector part 9.
[0037] The clamp 11 engages a bushing provided for the connector 6
and secures the connector 6 against an unintended unplugging. A
possible cross-section of the forked tube 3 and the supply tube 5
is explained in connection with FIG. 6. The supply tube 5 has a
larger cross-section than the forked tube 3 because the supply tube
5 typically has to transport double the airflow, because the
distance to be covered is greater and because the losses of comfort
with a great tube thickness are smaller. The word forked tube has
merely been chosen because the supply tube 5 is "forked" at the
Y-shaped element 4.
[0038] With a view to approval requirements it may be necessary to
shield the insulation of the heating wire 8 in the area of the nose
piece 2 against the prongs 12 by an additional partition wall 18.
In the area of the nosepiece 2 the heating wire 8 then extends in
an additional lumen 17.
[0039] If nasal cannulas are to be used for pneumatically splinting
the upper respiratory tract, there is a problem with respect to the
noise development caused by the high airflows through the supply
tubes and forked tubes, which are thin as compared to respiratory
tubes. This results in a high flow velocity of the air, which
generates noise at the edges. Therefore, it has been provided in
the nasal cannula illustrated in FIG. 1 that the inner walls of the
supply tube 5, of the Y-shaped element 4, of the two elements of
the forked tube 3, of the nosepiece 2 and of the prongs 12 do not
include any sharp edges and that specifically the inside of the
transitions between these components do not form any steps or
edges.
[0040] In another embodiment, component 7 may be a temperature
switch 19, which one can regard as a temperature sensor having a
poor resolution of one bit. The temperature switch can be realized,
for example, by a bimetallic contact having a release temperature,
for example, in the range of 30.degree. C. to 50.degree. C.,
specifically of 40.degree. C. If the temperature of the temperature
switch exceeds the release temperature, the heating circuit is
interrupted.
[0041] Additionally or alternatively to component 7, a temperature
sensor or switch 19 may be accommodated in the Y-shaped element 4,
which is illustrated in FIG. 2. An additional temperature switch,
e.g. a bimetallic contact having a release temperature of
(50.+-.10).degree. C., may represent a further protection against
overheating, e.g. if the forked tube 3 and/or the supply tube 5
is/are kinked unintentionally. Above the release temperature the
heating circuit is interrupted. The temperature switch 19 shown in
FIG. 2 schematically represents a bimetallic contact.
[0042] If no temperature sensor 7 is provided in the nosepiece, a
temperature sensor or switch 19 can effectively prevent
condensation on its own because the supply tube 5 not heated by the
patient's body ends in the Y-shaped element. Thus, the coldest spot
and therefore the most susceptible point to condensation in the
supply tube 5 is located between the compressor and the nosepiece
2. If the temperature of the coldest spot is kept above the thawing
point, no condensation will take place. A shifting of the
temperature sensor or switch into the Y-shaped element 4 may
increase the wearing comfort of the nasal cannula 1, because the
nosepiece 2 can be constructed lighter and smaller.
[0043] As the temperature of the air in the prongs 12 can be
calculated by approximation from the temperature in the Y-shaped
element, from the heating power and from the adjusted flow, if the
geometry of the nasal cannula is predetermined, specifically if the
lengths of the tubes and the diameters are predetermined, a
shifting of the temperature sensor from the nosepiece 2 into the
Y-shaped element 4 does not entail any considerable losses of
comfort.
[0044] FIG. 3 shows a second embodiment of a nasal cannula, in
which the supply tube 5 and the Y-shaped element 4 have been
replaced by a double-lumen tube 13. The double-lumen tube consists
of two forked tube elements which are mechanically connected to
each other. In this embodiment, the Y-shaped element 4 is not
applicable or is integrated in the connector 6 according to another
perspective. At the point where the two forked tube elements
diverge, no sharp edges are provided, but only wide radii. At this
point a clip 14 may be provided, which prevents the double-lumen
tube from further splicing apart. The division of an airflow to two
forked tube elements may be realized in the connector 6 and is,
thus, farther away from the prongs 12 so that the noise emission is
lower.
[0045] FIG. 4 shows a possibility to read out a temperature sensor
via two heating wires only. In the equivalent circuit diagram shown
in FIG. 4, the two heating wires 8 are represented by the two
resistors R.sub.H. R.sub.T represents a two-terminal network with a
temperature-dependent clamping characteristic.
[0046] In the simplest case, the resistor R.sub.T is merely a
temperature-dependent resistor such as a Pt100 or a Pt1000. R.sub.T
is large with respect to R.sub.H. The heating wires typically have
a resistance of 15.OMEGA. with great tolerances. If a positive
heating voltage U.sub.H is administered to the three serially
connected resistors, the temperature sensor is short-circuited by
the parallel-connected diode D, so that substantially only the
heating wires are heated. If a negative or a small measuring
voltage U.sub.M is administered to the three serially connected
resistors, the major part of the measuring voltage falls on the
temperature sensor R.sub.T. From this the temperature of the
temperature sensor can be determined. The remaining voltage
differences over the heating resistors can be calculated and
allowed for.
[0047] However, it is also possible to use a temperature-dependent
power source, which is, for example, provided in the form of the
integrated circuit AD592, as a two-terminal network R.sub.T. In
this case, the diode D serves to bypass and, thus, protect the
integrated circuit for the heating current. For example, a Schottky
diode may be used for the diode D because of its small forward
voltage. The direction of the measuring current is inverse to the
heating current. Its amount depends on the temperature and on the
integrated circuit as used and amounts to a few 100 .mu.A. The
particular advantage of this solution is that the wire resistance
has practically no influence on the measuring result.
[0048] Beside the directly analogously transmitting sensors it is
also possible to convert the temperature signal by modulating it
onto the heating current. This can be accomplished both analogously
and digitally and can be realized in custom-specific circuits. Such
circuits are known, for example, in connection with telephones or
baby phones for the modulation of audio-frequency signals to the
operating voltage.
[0049] The polarity or level of the administered voltage may be
switched over far more quickly than the thermal inertia of the
system, so that the switching over between heating voltage U.sub.H
and measuring voltage U.sub.M entails practically no change in
temperature.
[0050] FIG. 5 shows a section through the embodiment of a heating
wire 8. A metal wire 21 is embedded in an insulation 22. The
insulation has a star-shaped cross-section with five triangular
radials and is thus invariant with respect to rotations by
72.degree.. The metal wire 21, too, may have a star-shaped
cross-section. Each radial forms an elevation extending lengthwise
of the wire. The elevations may also extend about the shell in a
helical manner, with the length of one revolution being typically a
multiple of the circumference of the insulation. It is the purpose
of the star-shaped insulation to increase the surface of the wire
so as to reduce the thermal resistance with respect to the ambient
air. Moreover, even if the tube is kinked, air should flow around
the heating wire, if possible, on all sides so as to prevent it
from overheating and melting into the surrounding tube. The
triangular radials of the cross-section thereby expand the kink
site of a tube, with the contact surface between the tube and the
insulation being small and the thermal resistance thus remaining
large. The metal wire 21 may have a diameter of approximately 0.3
mm and a circle just about enclosing the apexes of the
cross-section may have a diameter of 1 mm.
[0051] FIG. 6 shows a section through a tube, which may be a forked
tube 3 or a supply tube 5. Typically, both types of tubes mainly
differ from one another by their diameter. The inner shell of the
tube includes projections 32, which serve to expand the jacket of
the tube also at kink sites so that the airflow is not fully
constricted despite the kink. On the outer circumference of the
tube and/or in the tube material itself, specifically in
projections 32, stabilizing filaments 31 and 33, respectively, are
mounted or incorporated to reduce a linear expansion of the tube.
The stabilizing filaments 31 and 33 may be incorporated into the
tube material, specifically into the projections 32 during the
production process. The stabilizing filaments 31 and 33 may be made
of an artificial or natural fibrous material, a synthetic material
or metal. The reason for the provision of the stabilizing filaments
is that heat-resistant PVC is too rigid, so that therefore, for
example, TPE or silicone have to be used. The latter materials are
strongly expandable, which may be undesired in the longitudinal
direction because tensile forces occurring in this case have to be
absorbed by the heating wire, thereby subjecting it and terminals
thereof to mechanical stress. As the tubes are operated at maximum
pressures of a few 100 millibar, a stabilization in a radial
direction does not seem to be necessary.
[0052] If the stabilizing filaments, specifically those in
projections 32, are made of an electrically conductive material,
specifically of metal, possibly surrounded by a thermally
resistant, not necessarily biocompatible, electrical insulation,
they can be employed for heating and replace the heating wire 8.
Thus, problems with non-biocompatible insulating materials may be
bypassed.
[0053] Finally, the forked tube 3 and/or the supply tube 5 may be
surrounded by a thermal insulation 34. This insulation 34 should
not be too thick because specifically a thin forked tube means
comfort and a thick insulation means a loss of comfort. On the
other hand, an insulation may render the surface of the tubes soft
and thus more comfortable. From a technical point of view the
insulation has the advantage that it reduces the heating power,
which has to remain under 15 W even in the case of a defect, if the
power control fails, or if the entire supply voltage is
administered. A reduction of the heating power therefore makes the
use of less exactly tolerated and, thus, more inexpensive heating
wires or longer tubes possible. The nasal cannulas currently
projected require, in fact, a maximum heating power of nearly 15
W.
[0054] FIGS. 7, 9 and 11 show three perspective views of a second
embodiment of a nosepiece 42. FIGS. 8 and 10 show sections along
lines Z-Z and M-M, respectively. The second embodiment of the
nosepiece 42 differs from the embodiment of nosepiece of 2 merely
with respect to the quality. To reduce the noise emission,
nosepiece 2 is more bulged, i.e. the clear cross-sectional area
increases more strongly from the tube connections to the prongs.
This reduces the flow velocity of the air so as to keep the noise
emission low. The reduction of the flow resistance by increasing
the cross-sectional area in the nosepiece is negligent, because the
flow resistance is mainly defined by the thickness of the forked
tube 3. At present, three prototypes each showing a different
increase of the cross-sectional area are in preparation.
Measurement results are not yet available.
[0055] The nosepiece 42 comprises tube connections 44, tube
transition regions 45, connection pieces 47, prongs 52 having
annular knobs 53 as well as a central connection piece 48. As can
be seen in FIG. 11, an internal radius step 46 is respectively
located between the tube transition regions 45 and the tube
connections 44, which just about compensates the difference between
the internal and the external radius of the forked tube 3 so as to
obtain a transition as even as possible between the inner surface
of the forked tube 3 and the nosepiece 42. For this purpose, the
projections 32 at the ends of the forked tube 3 may be removed, or
corresponding projections may be formed on the inner surface of the
nosepiece 42.
[0056] As can also be seen in FIG. 11, the clear cross-sectional
area in the tube transition region 45 is expanded.
[0057] As can readily be seen in FIG. 9, the transition regions 54
between the prongs 52 and the connection pieces 47 are generously
radiused so as to reduce the noise emission. In the prototype this
radius is, for example, externally 4.3 mm. The outer diameter of
the prongs in the proximity of the connection piece is 5.5 mm and
in the proximity of the aperture 5 mm. The wall thickness is
approximately 0.5 mm.
[0058] The transition region between the central connection piece
48 and the prongs 52 is likewise rounded off, wherein the external
radius is also in the range between 4 and 5 mm.
[0059] A sectional view of the indentation 43 in the central
connection piece 48 is illustrated in FIGS. 8 and 10 while a top
view is shown in FIG. 9. It serves the adjustment of a defined flow
resistance between the left and the right side of the nose glasses.
As is shown in FIG. 1, the nasal cannula is mirror-symmetrical.
This also applies in most cases to the user. As long as there is a
mirror symmetry, no air flows through the central connection piece
48. The symmetry can be interrupted, for example, by a kink in the
left or right forked tube 3 or by the user having a cold so that
one nostril is blocked. In the former case it is desirable, on the
one hand, that both prongs are supplied by the tube that is still
open. On the other hand, the kinked forked tube is, of course, not
entirely closed. The higher the pressure drop at the kinked forked
tube, the greater is the cooling airflow for the heating wire 8. To
slightly increase the pressure drop at the kinked forked tube, a
pressure drop at the central connection piece 48 may be desirable.
If one nostril is blocked, it is desirable to apply more air via
the other prong. In this case, too, an airflow through the central
connection piece 48 is desirable.
[0060] FIGS. 9, 10 and 11 also illustrate the temperature sensor
7.
[0061] In FIG. 12 the Y-shaped element 4 is shown in an enlarged
manner. One recognizes the two forked tube connections 91 at the
top and the connection 93 for the supply tube at the bottom. The
transition region 95 between the two forked tube connections is
rounded off and has in one embodiment a radius of 1 mm. In this
embodiment the forked tubes and the supply tube have, for the
purpose of comparison, an internal radius (without projections 32)
of 3 and 5 mm, respectively. The rounding of the transition region
95 is specifically important if asymmetric flow ratios exist, for
example, because of a kinked forked tube. All connections have
internal radius steps 92 and 94 so as to compensate the difference
between the internal radius and the external radius of the
connected tubes. The internal radius steps may either have
projections corresponding to the projections 32 in the connected
tubes and/or the projections 32 may be removed at the ends of the
tubes.
[0062] Although the invention was explained above in connection
with the gas air, of course, any other breathable gas mixture may
be used. Apart from this, the composition of air, for example, in
respect of its water and oxygen content is not exactly defined.
[0063] The invention was explained in more detail by means of
preferred embodiments above. A person skilled in the art will
appreciate, however, that various alterations and modifications may
be made without departing from the gist of the invention.
Therefore, the scope of protection will be defined by the
accompanying claims and their equivalents.
[0064] The following list of reference numerals may assist in
identifying the elements shown in the drawings. [0065] 1 nasal
cannula [0066] 2 nosepiece [0067] 3 forked tube [0068] 4 Y-shaped
element [0069] 5 supply tube [0070] 6 connector [0071] 7
temperature sensor [0072] 8 heating wire [0073] 9 electrical
connector part [0074] 10 pneumatic connector part [0075] 11 clamp
[0076] 12 prong [0077] 13 double-lumen tube [0078] 14 clip [0079]
16 internal radius step [0080] 17 additional lumen [0081] 18
partition wall [0082] 19 temperature switch [0083] 21 metal wire
[0084] 22 insulation [0085] 31 stabilizing filament [0086] 32
projection [0087] 33 stabilizing filament [0088] 34 thermal
insulation [0089] 42 nosepiece [0090] 43 indentation [0091] 44 tube
connection [0092] 45 tube transition region [0093] 46 internal
radius step [0094] 47 connection piece [0095] 48 central connection
piece [0096] 52 prong [0097] 53 knob [0098] 54 prong transition
region [0099] 91 forked tube connection [0100] 92 internal radius
step [0101] 93 supply tube connection [0102] 94 internal radius
step [0103] 95 transition region
* * * * *