Device for reflectometric examination and measurement of cavities

An apparatus and method for reflectometric examination and measurement of human or animal cavities such as air and food passages, the device having a flexible hose which is introduced into the cavity with the distal end of the hose placed past the zone of the passage to be examined. A transducer converts an activation signal from a signal generator to an excitation signal which is sent into the interior of the hose. A response signal which depends on the local deformation of the hose in the examined zone is picked up by a transducer and subjected to analysis in relation to the excitation signal. An analysis circuit and computer give an image on screen indicating the results of the examination.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a device for examination and measurement 
of constrictions or passages in cavities by means of acoustic 
reflectometry, the device comprising an electric signal source, a hose 
with a distal end to be introduced through an entrance to a cavity, a 
first transducer for transfer of an activation signal from the signal 
source to and through the hose, a second transducer for reception of 
response signals from the hose, the first and second transducers being 
connected with the hose close to its proximal end, and a computer adapted 
for analysis of the response signals in relation to the activation signal. 
2. Background Art 
For examination and measurement of blockings, deformations, movements etc. 
in various human and animal cavities, e.g. pharynx, larynx and other air 
and alimentary passages, arteries etc. various methods are known. 
In catheter examinations, balloon-angioplasty etc. it is known to use a 
probe in the shape of a hose of flexible material. 
Another method is based on measurement of reflection (reflectometry) using 
an acoustic, transient excitation signal which, through a hose and through 
the patient's mouth, is sent into the air passages of the patient, cf. 
e.g. U.S. Pat. No. 4,326,416. 
Another method based on the use of a non-transient excitation 
signal--random or pseudorandom signal--is used in an equipment 
manufactured by the applicant firm, under the commercial designation SRE 
2000 and SRE 2000 PC. 
Especially in connection with examination of movements in the air passages 
and examination of stertorous respiration mainly pressure transducers, 
placed in or on catheters to be introduced in nose or mouth, have so far 
been used. This allows for measurement of pressure variations, 
constrictions, etc. in nose and throat. 
A drawback in this technique is to be seen in that the measurement probe 
must include a relatively large number of closely located pressure 
transducers connected to a corresponding apparatus which offers the 
possibility, on a screen with a sufficient resolution, to determine the 
position of and pressure at each examined spot. 
Known techniques also include endoscopy by which optical examinations are 
made of nose, pharynx and other internal organs. However, these 
examinations have a certain number of limitations, including the clarity 
and size of the optical image, the size of the catheter and especially the 
lack of catheter flexibility which makes, the catheter unsuitable for 
examination of, e.g., stertorous respiration. 
CT and MRI scannings have been tried, but involve long periods of 
measurement which do not give useful measurements and no dynamic 
measurements at all. 
By using acoustic reflectometry of the above mentioned kind, it is known 
that it is possible to measure across-sectional areas in the air passages 
as a function of the distance from the transducer used for emission of the 
excitation signal, cf. the above patent U.S. Pat. No. 4,326,416 or an 
article: "Airway geometry by analysis of acoustic pulse response 
measurements" by Andrew C. Jackson et al. in J. Appl. Physiology, 43(3): 
525-536, 1977. 
Direct measurement limits measurements of cross modes, i.e. cross 
resonance, and of the adjacent cavities, which, to a large extent, limits 
the use of such direct measurements having large differences in the 
cross-sectional areas as a function of the distance from the signal 
source. 
Especially when examining stertorous respiration, the use of direct 
measurements is hampered by the transient or continuous sound influence, 
necessary for the measurements, which affects the sleep state or awakens 
the patient during the examination phase itself, and also causes 
measurement errors because of noise from the measurement microphone and a 
measurement error due to the very large cavity made up by the mouth and 
throat. 
SUMMARY OF THE INVENTION 
The invention aims at remedying the above mentioned disadvantages and in 
order to do so a device of the type mentioned in the introduction is 
according to the invention characterised in that the hose at least in a 
measuring zone is designed with a thin outer wall of a soft and/or 
flexible plastics or elastomeric material, and that the measuring zone is 
positioned at or near a distance from the distal end of the hose. 
By the hose at least in a measuring zone being designed with a thin outer 
wall of a soft and/or flexible plastics or elastomeric material, it is 
attained that the position or movement of the walls of the cavity is 
transferred to a corresponding position or movement of the thin outer wall 
of the hose through abutment of the wall of the hose against the walls of 
the cavity. 
By the measuring zone being positioned at or near a distance from the 
distal end of the hose, it is attained that the measuring zone may be 
positioned in constrictions or passages to be examined or measured by 
advancing the distal end of the hose through the cavity and past the 
constructions or passages, respectively. 
The invention is based on the recognition that humans have many spots where 
a contracted or pathological change or obstruction in the air passages, 
urinary system, etc. can be difficult to determine, locate and measure 
with the above mentioned known technique, among other things because of 
the common cross resonance in the large or small surrounding cavities at 
the spot which is to be examined and that it is particularly suitable to 
use a very flexible hose, whose wall can be made to abut the side wall in 
question of the passage or can be deformed by some change, e.g. a 
constriction at the spot in question. By this, the measurement equipment 
can only "see," so to speak, the interior of the hose and clearly measure 
the least deformation in the inner cross-sectional area of the hose as a 
function of the distance from the spot in the hose where the excitation 
signal is emitted on to the spot or spots where a deformation or 
deformations appear and where the response signal originates. 
According to a particular appropriate embodiment of the invention the 
device can be characterised in that the hose has a longitudinal, axially 
centered lumen surrounded by a ring-shaped wall, and around the 
ring-shaped wall a number of spaced, longitudinal canals separated from 
each other by means of essentially radial partitions. 
By combining reflectometric measurements made inside the lumen of the hose 
and the peripheral canals or chambers it is possible with much greater 
sensitivity to determine the position or measure the areas in the hose 
which due to some local change or obstruction in the passage in question 
(air passage, urinary system etc.) are compressed, as well as the degree 
of compression. 
Upon insertion of the hose it is possible, with or without action of 
positive or negative pressure in the lumen of the hose and/or the canals, 
by measuring the inner cross-sectional areas of the hose as a function of 
the distance, to determine the areas which are the most narrow or compress 
the hose locally. 
In this way it is possible, in balloon examinations and freeing of arteries 
in case of arteriosclerosis, to check the distension (cross-sectional area 
per longitudinal distance) of the balloon at the end of a catheter 
concurrently with the inflation of the balloon. 
The invention further provides a method for arranging a hose in a 
constriction or passage in a cavity, said hose being adapted for 
examination and measurement of such constrictions or passages by means of 
acoustic reflectometry, whereby an activation signal is transferred from a 
signal source via a first transducer to the hose and forwarded through the 
hose, and response signals from the hose are transferred via a transducer 
second to a computer adapted to analyze the response signals in relation 
to the activation signal, the hose over at least part of its longitudinal 
extension having at least one measuring zone of increased outer wall 
flexibility, by which method a distal end of the hose is introduced 
through an entrance into the cavity. 
According to the invention, the hose is being placed with the measuring 
zone in the constrictions or passages to be examined or measured, by the 
distal end of the hose being advanced through the cavity and past the 
constrictions or passages, respectively, whereby the measuring zone is 
located in the constrictions or passages. 
By advancing the distal end of the hose past the constriction or passage in 
the cavity, it is attained that the measuring zone, being placed behind 
the distal end of the hose, near this end or at a distance from it, will 
be kept straight during the introduction to the cavity. The measuring zone 
has a reduced ability to keep itself straight during the introduction into 
the cavity, due to the increased flexibility of the outer wall of the hose 
in this zone, and by advancing the distal end of the hose past the 
constriction or passage, the measuring zone is in fact "pulled" through 
the constriction or passage by a pull from the distal end of the hose. 
This pull may, e.g., be exerted on the measuring zone by inserting a 
springy steel wire into the hose during its introduction into the cavity. 
The distal end of the hose is closed, so the wire will be able to push the 
distal end forward trough the cavity. 
In preferred embodiments of the method, the cavity is an organic cavity, 
e.g. the respiratory passages, the blood or lymph tracts, the alimentary 
canal, or the urinary system or sections thereof of an animal or a human 
body. 
Other features and advantages of the present invention will become apparent 
from the following description of embodiments of the invention which 
refers to the accompanying drawings.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
FIG. 1 shows the basic lay-out of the device according to the invention. 
As seen in FIG. 1, there is shown a hose 1, the design of which will be 
explained below. At its proximal end A, the hose 1 of a manner known per 
se, not illustrated, is connected to auxiliary equipment used for 
inserting the hose in, e.g., the air passages of a patient, through the 
mouth or the nostrils, or in the urinary system or an artery. The distal 
end of the hose B, which after insertion, will be present in the cavity of 
the patient who undergoes an examination. 
An electronic signal generator 2 is adapted to give an activation signal to 
a transducer 3 connected to the hose 1. The signal generator 2 delivers 
the same signal to a signal analysis processor 4. A transducer 5 is 
connected to the hose 1. When an excitation signal is transferred from the 
signal generator 2, via the transducer 3, to the interior of the hose 1, 
this signal will propagate in the hose, on to the distal end of the hose, 
from where a response signal is sent back and received by the transducer 5 
and from there led to the signal analysis processor 4. 
The signal analysis processor 4 is connected to a computer 6 by means of 
which it is possible on a screen 7 to present an image which illustrates 
the results of the examination and measurements made. 
The transducer 3 can be an arbitrary type known per se, e.g. an 
electromagnetic transducer, an electrostatic transducer, a piezo-electric 
transducer, etc. Its task is to transform the electronic signal from the 
signal generator 2 into an excitation signal in the interior of the hose 
1. 
The transducer 5 can also be of the above mentioned arbitrary type, e.g. a 
microphone, the purpose of which is to receive an acoustic response signal 
from the distal end of the hose and to transform this response signal into 
an electric signal which is led to the signal analysis processor 4. 
The excitation signal can be a transient signal in the low frequency band, 
as known from, e.g., the above U.S. Pat. No. 4,326,416 or from the Jackson 
article. It can also be a non-transient excitation signal--a random or 
pseudo-random signal, as used in the above mentioned equipment SRE 2000 
and SRE 2000 PC. 
The invention is a very important contribution to determination of the 
exact position of the obstruction and to measure when and for how long the 
obstruction will last. It is thus possible to connect an alarm system to 
the measuring equipment which gives an alarm when the probe has been 
compressed for a certain fixed period of time. 
The analysis itself of the response signal in relation to the excitation 
signal belongs to a technique known per se. 
FIG. 2 shows part of the hose 1 in the zone G of the hose. The 
characteristic of the hose according to the invention is that, at least in 
its zone G at the distal end it is thin-walled. The hose according to FIG. 
2 is a simple hose, e.g. a hose with only one lumen 19. 
If the hose 1, as will be explained later, locally, e.g. in the mentioned 
zone G, is exposed to an external mechanical influence (as indicated at 
the arrow F), due to a constriction in the air passage, the oesophagus or 
an artery of the patient, the reduction of the cross-section of the hose 
in said zone G will consequently bring about a modification of the 
response signal, a modification which can be seen in the picture analysis 
and on the screen. This modification expresses the change that might be 
present in the patient, e.g. a constriction. 
FIG. 3 shows a further embodiment of a hose according to the invention. The 
hose 10 has a central lumen 11 and three peripheral annular canals or 
chambers 12, 13, and 14. Such a hose can be made by extrusion of a soft 
plastics material or elastomer. The outer diameter of the hose can vary 
from, e.g., 1 mm to 3-4 mm, according to the intended use. The wall 15 
around the central lumen 11 is continuous in the longitudinal direction of 
the hose and it separates the lumen 11 from the three peripheral chambers 
12, 13, 14. The chambers themselves which are also continuous in the 
longitudinal direction of the hose are separated from each other by means 
of radial partitions 16, 17, and 18. 
FIG. 4 shows a cross-sectional view of the hose in a plane at right angles 
to the axis of the hose. 
A transducer 20 has been introduced from the outside through the outer 
chamber 12 and through the wall 15 so that the response signal receiving 
end 21 of the transducer 20 is located in the lumen 11. 
FIG. 4 also shows two transducers 22 and 23, which are introduced from the 
outside into the outer wall of the hose 15 and whose response signal 
receiving ends 24 and 25 respectively are located in a peripheral chamber, 
e.g. chamber 14. 
While the sectional view in FIG. 4 shows the two transducers 22 and 23 
placed in the sectional plane (the plane of the diagram) it should be 
understood that they do not need be it and that, e.g., transducers 23 can 
be placed axially displaced from the transducer 22. 
FIG. 5 illustrates the use of the hose in order to determine the position 
of and measure the so-called tongue fallback with a patient, e.g. the 
situation where the patient's tongue narrows the upper air passages. 
Here the hose has been introduced through the nostrils and into the air 
passage. Part of the hose is compressed by the rear end of the tongue in 
the zone D. 
FIG. 6 illustrates the use of the hose in order to determine the position 
of and measure the outbreak of vibrations in the soft palate (velum 
palatum). 
FIG. 6 shows the situation illustrated in FIG. 5 as well as the situation 
where said soft parts of the palate compress the hose in the zone E. 
The mode of operation of the device according to the invention will be 
explained below. 
It should be recalled, as mentioned in the preamble of the specification, 
that it is possible with the measurement technique known from U.S. Pat. 
No. 4,326,416 and from the Jackson article and the one used in the known 
measurement equipment of the applicant firm, to determine the 
cross-sectional area of a cavity as a function of the distance from the 
excitation signal giving transducer to the measurement spot. 
While the known technique has the disadvantage that the measurements can be 
disturbed by crossmodes (e.g. cross resonances) which, e.g., is the case 
in examinations of the air passages and the lungs with a patient, the 
technique according to the invention has the essential advantage that it 
is the inner cavity of the hose which constitutes the measurement cavity 
proper, which on occasion will be modified by, e.g., a constriction in the 
passage in which the hose has been introduced. The construction of the 
hose excludes the outbreak of cross resonances as in the known technique. 
If the hose, which as mentioned has thin, flexible walls, is affected 
locally by a constriction, one or more of the outer chambers 12, 13, 14 
and/or the central canal (lumen 19, FIG. 2, or lumen 11, FIG. 3) is 
affected mechanically by this constriction, this situation being measured 
immediately by the measurement equipment. 
Supposing that the hose has the form shown in FIG. 3 and 4 and that it has 
been introduced in the patient's air passage as shown in FIG. 5. The 
mechanical compression force from, e.g., the rear end of the tongue on the 
hose can, e.g., influence one of the outer chambers, the outer chamber 14, 
which can be ascertained electronically in the measurement equipment, or 
perhaps also the second and third outer chamber. 
The invention therefore offers the possibility to get a "differentiated" 
determination of position, and measurement of the cross sectional area in 
the zone in question as a function of the distance from the excitation 
signal sending transducer in question to the zone in question. 
If it is only the outer chamber 14, as mentioned in the previous paragraph, 
which in a patient's air passage is influenced by, e.g., the rear end of 
the tongue, only the transducer(s) belonging to the chamber 14 will react. 
FIG. 6 illustrates as already mentioned the situation where a patient is to 
be examined for vibrations in the soft parts of the palate, e.g. typically 
stertorous respiration. The vibrations in the zone E will influence at 
least one of the outer chambers of the hose and the measurement equipment 
can carry out the positioning and measurement. 
Another field of particular medical or surgical interest for the invention 
is examinations of constrictions, e.g. calcification or other pathologic 
disorders in the arteries, e.g., at the heart. 
FIG. 7 shows another embodiment of the hose according to the invention, 
made for this kind of examination. 
The distal end of the hose 31 is in a manner known per se (normal catheter 
technique for widening blood vessels) formed as an inflatable balloon 32. 
It can be inflated by pressure feed through longitudinal canals (not 
shown) in the outer wall of the hose. Between the balloon 32 and the 
distal end B of the hose there is, in a manner known per se, a number of 
openings 33 which are to ensure blood passage and at some distance away 
from the balloon 32 in the direction towards the proximal end A of the 
hose there are outlets (not shown) for the circulating blood. 
In the case where it is medically or surgically advisable temporarily to 
disconnect the blood circulation through the hose in order to measure 
and/or widen, it is possible to use a hose which does not have a canal for 
circulating blood, e.g. having neither openings 33 nor matching outlets. 
Upon introduction of the hose it is possible, in the above mentioned way, 
to position and measure the constriction or the calcification and the 
widening, if any. 
Within the scope of the invention it is possible to make a hose without the 
above mentioned balloon 32 and manufacture the hose so that it has, at its 
distal end B, e.g. where the balloon otherwise would be placed, a 
considerably thinner and/or considerably more flexible outer wall. Within 
the scope of the invention, the hose can be formed near its proximal end A 
with means (not shown) so as to establish a negative or positive pressure, 
e.g. of fluid in the lumen and/or in each chamber. Such a positive 
pressure will bring about a dilation of said thinner and/or more flexible 
part of the hose at the distal end. Whether the hose has a balloon 32 or 
not, whether it is inflated or not and whether one or more chambers are 
compressed by the constriction in the vein, the measurement equipment will 
give a picture of the situation in the area in question. 
A description of a hose has been given above with one single lumen or with 
one central lumen and peripheral chambers, but it is within the scope of 
the invention to allow for a hose with two axial canals or a central lumen 
and, e.g., two, four or five peripheral chambers. 
Obviously medical or surgical considerations decide the choice of the inner 
and outer dimensions of the hose which is the reason why the hose is 
manufactured in different sizes (and lengths too), while the measurement 
equipment decides the upper frequency limit, if a transient signal is 
used, as well as the other physical parameters. 
If the hose according to the invention is to be used for examination of the 
breathing organs, the needed supply of air or gas to the patient can take 
place through the inlet of the hose (A in FIG. 1) and through a canal to 
the openings 33 (FIG. 7) at the distal end of the hose. In that case the 
response signal which comes from, e.g. one or several of the peripheral 
chambers, can be separated electronically in the measuring equipment from 
the response signal coming from the lungs, due to the difference in the 
signal transit time. 
A particular example of the use of the invention has already been 
mentioned. 
Exact examinations of persons, whose air passages are blocked during their 
sleep and who can be described as having stertorous respiration, are 
naturally very difficult and through the ages many failed corrective 
operations have been made on these patients. 
The invention is a very important contribution to determine the exact 
position of the blocking and to measure when and for how long the blocking 
will last. It will therefore be possible to connect an alarm system to the 
measuring equipment which gives an alarm when the probe has been 
compressed for a certain fixed period of time. 
Today a pulsoxymeter (instrument measuring the concentration of oxygen in 
blood) is connected during these examinations. An alarm is therefore 
activated when the concentration reaches certain predetermined limits. 
It is not the stertorous respiration itself which is a risk, but the period 
during which the patient does not breathe because of a blocking. 
This is the reason why equipment which acoustically registers the 
stertorous respiration does not activate an alarm with sufficient 
security, as the non-occurrence of a "snoring sound" is either due to a 
quiet, steady respiration with a low regular flow, which is all right, or 
the air passages being blocked for a long time. This is where the risk 
lies. 
In order to stress the importance of the invention it should be mentioned 
that the under-supply of oxygen to the lungs for such a long time 
considerably increases the risk of brain damages and thrombosis, 
especially for older overweight persons. 
An internal measurement has the advantage that the patient is not awakened 
during the measurements by the excitation signal and at the same time the 
measurements are not influenced to a large extent by the high tone sound 
spectrum of the snoring sounds. 
The measurement probe itself is very easy to introduce ambulatory into the 
patient's nose before the night, in cooperation with a doctor or a nurse. 
A correct "tightening" through the nose happens automatically due to the 
reflectory swallowing, and a connection (transducer/microphone part) at 
the end which projects out of the nose can be made without problems. 
A synchronization of the area measurements with the snoring sound is easy 
to make either by means of an external microphone, e.g. one of the 
transducers 22 and 23, (FIG. 4) or by using the low frequency signal 
received through the measurement microphone. 
It should also be noted that the measurement equipment (hardware/software) 
which adequately makes the measurements in each chamber and during the 
measurements changes the static pressure in each chamber can also 
concurrently give information about the elasticity of the tissue giving 
counter-pressure to the surface of the chambers. 
By establishing a pressure in the hose and a concurrent supply of acoustic 
energy in the infrasound band up to 200 Hz in the lumen and the chambers 
and a synchronization of this infrasound signal with the acoustic 
rhinometry (reflectometric) measurements, it is possible to obtain 
valuable information about the elasticity in the walls to which the 
hosewall establishes a contact during the various pressure conditions. 
Considering that these kinds of transducers, e.g. a piezoelectric 
transducer function in both directions, e.g. being applied an electric 
voltage in order to give a pressure signal, or receiving a pressure signal 
and give an electric signal, it is obvious that instead of two transducers 
3 and 5 in FIG. 1 it is in principle possible to use one single 
transducer, in which case the signal generator 2 should be electronically 
designed in such a way that, when operated from the analysis unit 4 and 
the computer 6, it firstly gives a transient signal and then transfers the 
response signal to the analysis unit. If a random or a pseudo-random 
signal is used as excitation signal, emitted continuously in the 
measurement period, two separate transducers will be used, as shown in 
FIG. 1. 
It should also be added that the invention also offers the possibility of 
making prostate or uterus examinations etc. 
Finally, it should be mentioned that the invention also offers a 
possibility to make reflectometric examinations of other cavities, e.g. 
current control of the cavity in an item manufactured by extrusion, as the 
technique according to the invention makes it possible to closely monitor 
the extrusion parameters in order, e.g., to obtain a constant thickness of 
walls in the item, which could, e.g., be a hose.