USOO7008380B1
`
`(12) United States Patent
`Us 7,008,380 B1
`Rees et al.
`(45) Date of Patent:
`Mar. 7, 2006
`
`(10) Patent N0.:
`
`(54) AUTOMATIC LUNG PARAMETER
`ESTIMATOR
`
`(76)
`
`Inventors: Stephen Edward Rees,
`Forchhammersvej 40, DK-9000 Aalborg
`(DK); Egon Steen Toft, Blegdalsparken
`102, DK-9000 Aalborg (DK); Per
`Thorgaard, Leonorevej 6, DK-9000
`Aalborg (DK); Soren Christensen
`Kjaergaard, Nordvestvej 11, DK-9000
`Aalborg (DK); Steen Andreassen,
`Kong Georgs Vej 7, DK-9000 Aalborg
`(DK)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.:
`
`09/890,801
`
`(22) PCT Filed:
`
`Feb. 1, 2000
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`4,354,488 A
`
`10/1982 Bartos
`
`(Continued)
`FOREIGN PATENT DOCUMENTS
`
`DE
`
`251706
`
`11/1987
`
`(Continued)
`OTHER PUBLICATIONS
`
`Andreassen, S., Egeberg, J ., Schroter, M.P., Andersen, PT.
`(1996). Estimation of pulmonary diffusion resistance and
`shunt in an oxygen status model. Comput Methods Pro-
`grams Biomed, vol. 51, pp. 95-105.
`
`(Continued)
`
`Primary Examiner—Robert L. Nasser
`(74) Attorney, Agent, or Firm—Birch, Stewart, Kolasch &
`Birch, LLP
`
`(86) PCT No.:
`
`PCT/DK00/00040
`
`(57)
`
`ABSTRACT
`
`§ 371 (C)(1),
`(2), (4) Date: Oct. 30, 2001
`
`(87) PCT Pub. No.: W000/45702
`
`PCT Pub. Date: Aug. 10, 2000
`
`(30)
`
`Foreign Application Priority Data
`
`Feb. 3, 1999
`May 12, 1999
`Jun. 17, 1999
`
`(DK)
`(DK)
`(DK)
`
`............................... 1999 00129
`
`1999 00649
`............................... 1999 00859
`
`(51)
`
`Int. Cl.
`(2006.01)
`A613 5/00
`(52) U.S. Cl.
`.................................. 600/532; 128/204.23
`(58) Field of Classification Search ................ 600/322,
`600/323, 529—538; 128/204.23
`See application file for complete search history.
`
`AdeVice for determining one or more respiratory parameters
`relating to an individual is disclosed, as well as a method for
`determining one or more respiratory parameters by means of
`the device, wherein the individual is suffering from hypox-
`emia or is at risk of hypoxemia. However, the method and
`the device may also be applied to healthy individual e.g. for
`testing of medicaments. The device is controlled by a
`computer equipped with suitable software and includes
`functionality for on-line continuous data collection, auto-
`matic assessment of the timing of measurements, automatic
`assessment of the next target (oxygen saturation of arterial
`blood (SpO2)), automatic assessment of the appropriate
`fraction of oxygen in inspired gas (FIO2) settings to achieve
`the target SpO2, automatic control of the F102, on-line
`parameter estimation, and automatic assessment of the num-
`ber of measurememts requied.
`
`58 Claims, 10 Drawing Sheets
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`APPLE 1012
`
`APPLE 1012
`
`1
`
`

`

`US 7,008,380 B1
`Page 2
`
`U.S. PATENT DOCUMENTS
`
`4/1992 Maher
`5,103,814 A
`8/1993 Psaros et 211.
`5,237,990 A
`5,251,632 A * 10/1993 Delpy ........................ 600/323
`5,282,464 A
`2/1994 Brain
`
`128/204.23
`5,353,788 A * 10/1994 Miles ......
`5,365,922 A * 11/1994 Raemer
`................. 128/204.23
`5,388,575 A
`2/1995 Taube
`5,429,123 A *
`7/1995 Shaffer et al.
`5,596,986 A
`1/1997 Goldfarb
`5,682,877 A * 11/1997 Mondry ................. 128/204.23
`FOREIGN PATENT DOCUMENTS
`
`......... 128/204.23
`
`EP
`EP
`EP
`EP
`EP
`FR
`GB
`
`0342443
`0502270
`A1502270
`0753320
`A1753320
`2599977
`209321 B
`
`11/1989
`9/1992
`9/1992
`1/1997
`1/1997
`12/1987
`8/1982
`
`OTHER PUBLICATIONS
`
`Andreassen, S., Rees, S.E., Kjaeraard, S., Thorgaard, P.,
`Winter, S.M., Morgan, C.J., Alstrup, P., and Toft, E. (1999).
`Hypoxemia after coronary bypass surgery modeled by resis-
`tance to oxygen diffusion. Critical Care Medicine, vol. 27,
`pp. 2445-2453.
`De Gray, L., Rush, E.M., Jones, JG. (1997). Anon-invasive
`method for evaluating the effect of thoracotomy on shunt
`and ventilation perfusion inequality. Anaesthesia, vol. 52,
`pp. 630-635.
`King, T.K.C., Weber, B. Okinaka, A., Friedman, S.A., Smith,
`J .P. Briscoe, WA. (1974). Oxygen transfer in catastrophic
`respiratory failure. Chest, vol. 65, pp. 40S-44S.
`
`Rees, S.E., Rutledge, G.W., Andersen, P.T., Andreassen, S.
`(1997). Are
`alveolar block and ventilation-perfusion
`mismatch distinguishable in routine clincal data.
`In:
`Proceedings of the European society of computers in
`anaesthesia
`and intensive
`care
`conference, Erlangen,
`Germany, Sep. 18-19, 1997.
`Riley, R.L., Counard, A. (1951a) Analysis of factors affect-
`ing partial pressure of oxygen and carbon dioxide in gas and
`blood of the lungs: Theory. J. Applied Physiol., vol. 4, pp.
`77-101.
`
`Riley, R.L., Counard, A., Donald, K.W. (1951b). Analysis of
`factors affecting partial pressure of oxygen and carbon
`dioxide in gas and blood of the lungs: Method. J. Applied
`Physiol., vol. 4, pp. 102-120.
`Roe, P.G., Galdelrab, R., Sapsford, D., Jones, JG. (1997).
`Intra-operative
`gas
`exchange
`and
`post-operative
`hypoxaemia. European Journal of Anaesthesiology, vol. 14,
`pp. 203-210.
`(1995). The PiO2 vs. SpO2
`Sapsford, D.J., Jones, JG.
`diagram: a non-invasive measure of pulmonary oxygen
`exchange. European Journal of Anaesthesiology, vol. 12, pp.
`369-374.
`
`(1995).
`Siggaard-Andersen, M., Siggaard-Andersen, O.
`Oxygen status algorithm, version 3, With some applications,
`Acta Anaesthesiol Scand. vol. 39, Supp. 107, pp. 13-20.
`Wagner, P.D., Saltzman, H.A., West, J .B. (1974). Measure-
`ment of continuous distributions of ventilation-perfusion
`ratios: theory. J. Appl. Physiol. vol. 36 (5) :588-599.
`Wagner, P.D., Hendenstierna, G., Bylin, G. (1987). Ventila-
`tion-perfusion inequality in chronic asthna. Am. Rev. Respir.
`Dis., vol. 136, pp. 605-612.
`
`* cited by examiner
`
`2
`
`

`

`US. Patent
`
`Mar. 7, 2006
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`Sheet 1 0f 10
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`US 7,008,380 B1
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`100
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`99
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`98
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`
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`
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`
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`
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`
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`
`0.6
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`
`0.8
`
`1
`
`Fig. 1
`
`3
`
`

`

`US. Patent
`
`Mar. 7, 2006
`
`Sheet 2 0f 10
`
`US 7,008,380 B1
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`
`Fig. 2
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`4
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`

`

`US. Patent
`
`Mar. 7, 2006
`
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`US 7,008,380 B1
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`US. Patent
`
`Mar. 7, 2006
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`US. Patent
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`Mar. 7, 2006
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`US. Patent
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`Mar. 7, 2006
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`US. Patent
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`Mar. 7, 2006
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`US. Patent
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`Mar. 7, 2006
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`US. Patent
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`Mar. 7, 2006
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`Sheet 9 0f 10
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`US 7,008,380 B1
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`US. Patent
`
`Mar. 7, 2006
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`Sheet 10 0f 10
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`US 7,008,380 B1
`
`saturation
`
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`
`D
`
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`
`Fig. 10
`
`12
`
`12
`
`

`

`US 7,008,380 B1
`
`1
`AUTOMATIC LUNG PARAMETER
`ESTIMATOR
`
`This application is the national phase under 35 U.S.C. §
`371 of PCT International Application No. PCT/DK00/00040
`which has an International filing date of Feb. 1, 2000, which
`designated the United States of America and was published
`in English.
`The present invention relates to a device for determining
`one or more respiratory parameters relating to an individual.
`The device may include functionality for on-line continuous
`data collection, automatic assessment of the timing of mea-
`surements, automatic assessment of the next target (oxygen
`saturation of arterial blood (Sp02)), automatic assessment of
`the appropriate fraction of oxygen in inspired gas (FIOZ)
`settings to achieve the target SpOz, automatic control of the
`F102, on-line parameter estimation, and automatic assess-
`ment of the number of measurements required. This func-
`tionality is achieved through a novel device including ven-
`tilatory equipment, blood gas analysis equipment and
`computer hardware and software.
`Furthermore, the present invention relates to a method for
`determining one or more respiratory parameters by means of
`the above-mentioned device, wherein the individual is suf-
`fering from hypoxemia or is at risk of hypoxemia. The
`individual may also be a healthy individual.
`The use of the device for examination and monitoring
`respiratory parameters relating to humans are of particular
`interest, but the device may also be applied to farm animals
`such as pigs, or to domestic animals such as dogs.
`
`BACKGROUND
`
`Oxygen enters the body with inspiration and diffuses from
`the lungs into the blood. Subsequently the blood circulation
`transports oxygen to the tissues. Disorders of oxygen trans-
`port from the inspired air into the blood can result in a low
`oxygen saturation of the blood. These disorders in oxygen
`uptake include abnormal ventilation of the lung, seen in for
`example chronic obstructive pulmonary disease; abnormal
`oxygen diffusion in the lung, seen in for example pulmonary
`fibrosis; and abnormal perfusion (i.e. blood flow) through
`the lung. Estimation of parameters describing these oxygen-
`ation problems is important for diagnosis, monitoring and
`assessing appropriate therapeutic intervention. This is true in
`a wide variety of patients, from those who are automatically
`ventilated and who often require continuous supplement of
`oxygen, to out-patients who only suffer from dyspnoe during
`exercise.
`
`In clinical practice the clinician usually relies upon simple
`measurements or variable estimates to assess the patients
`oxygenation problems. These include qualitative estimates
`obtained from stethoscopy or chest X-ray. They also include
`more quantitative estimates such as arterial oxygen satura-
`tion, the alveolar-arterial oxygen pressure gradient, or esti-
`mates of the “effective shunt”, a parameter which describes
`all oxygenation problems in terms of a fraction of blood
`which does not flow through the lungs (Siggaard-Andersen
`and Siggaard-Andersen, 1985).
`Whilst the “effective shunt” is a parameter which has been
`used widely in the clinical literature it cannot adequately
`describe the ‘clinical’ picture seen in patients when the
`inspired oxygen fraction is varied. This observation is illus-
`trated in FIG. 1 where the “effective shunt” has been
`
`estimated for a single patient at four different
`oxygen fractions, and varies from 15—25%.
`
`inspired
`
`2
`In contrast to the poor clinical description of oxygenation
`problems, detailed experimental
`techniques such as the
`Multiple Inert Gas Elimination Technique (MIGET) (Wag-
`ner et al., 1974) have been developed which describe the
`parameters of models with as many as fifty lung compart-
`ments. The parameters of these models give an accurate
`physiological picture of the patient. Whilst the MIGET has
`found widespread application as an experimental tool its use
`as a routine clinical tool has been somewhat limited (Wagner
`et al., 1987). This is largely due to the cost and complexity
`of the technique.
`As stated previously, “effective shunt” is insufficient to
`describe oxygenation problems. Further parameters describ-
`ing the patient’s oxygenation problem can be obtained from
`data where inspired oxygen is varied, i.e. data similar to that
`presented in FIG. 1. This was first recognised by Riley et al.
`(1951a, 1951b) and later by King et al. (1974). These authors
`used mathematical models to divide the oxygenation prob-
`lem into that due to an alveolar-lung capillary drop in the
`partial pressure of oxygen, and that due to a shunt problem.
`To estimate two parameters describing the oxygenation
`problem requires taking measurements of blood samples and
`of ventilatory variables at each inspired oxygen fraction.
`Estimating lung parameters using the data from four inspired
`oxygen fractions required four blood samples, a procedure
`which is still rather time consuming and in some environ-
`ments impractical.
`More recently, development of non-invasive methods for
`measuring the oxygen saturation of the blood have lead to
`renewed interest
`in estimation of parameters describing
`oxygen transport obtained by varying FIOZ. Andreassen et
`al. (1996, 1999), Sapsford et al. (1995), de Gray et al. (1997)
`and Roe et al. (1997), have presented the use of two
`parameter mathematical models of oxygen transport, the
`oxygenation problem being described as shunt combined
`with either a diffusion abnormality (Andreassen et al. (1996,
`
`1999)) or due to a ventilation/perfusion (V/Q) mismatch
`(Sapsford et al. (1995), de Gray et al (1997), Roe et al.,
`(1997)). These model representations have been shown to
`provide identical fits to routine blood gas and ventilatory
`data obtained by varying FIO2 (Rees et al. 1997).
`The clinical relevance of the two parameter models is
`illustrated in FIG. 2, where increases in the pulmonary shunt
`parameter results in a vertical depression of the FIOz/SaO2
`curve, (V—shift) and abnormalities in the second parameter
`
`(ventilation/perfusion (V/Q) mismatch or oxygen diffusion
`resistance (Rdiff)) results in a lateral displacement of the
`FIOZ/SaO2 curve. Clearly, the lateral displacement of the
`FIOz/SaO2 curve (H-shift) is clinically a more significant
`problem as it describes a situation where large changes in
`oxygen saturation can occur for only small changes in F102.
`In this situation the patient
`is at
`increased risk of an
`oxygenation problem.
`The two parameter model of Sapsford et al. (1995), has
`been shown to fit data from normal subjects; patients before
`and after thoracotomy (Sapsford et al. 1995, de Gray et al.,
`1997); and patients during (Sapsford et al. 1995, Roe et al.,
`1997), and after (Roe et al., 1997) abdominal surgery.
`Similarly, the two-parameter model described by Andreas-
`sen et. al. has been shown to fit data from normal subject and
`postoperative cardiac patients (Andreassen, 1999) and a
`wide range of as yet un-published results. Examples of these
`results are shown in FIG. 3.
`
`In contrary to detailed experimental approaches (e.g. the
`MIGET), these two parameter models can be used routinely
`in clinical practice. In particular, these techniques may find
`
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`

`US 7,008,380 B1
`
`3
`application in the monitoring and choice of therapeutic
`treatment for patients with left-sided heart failure, or to
`assess patients risk of post-operative hypoxaemia.
`Until now, estimation of oxygenation parameters has
`involved manual titration of the FIOz/SaO2 curve and off-
`line estimation of the parameter values. This is time con-
`suming with experimental times of approximately 45 min-
`utes, not including the time required for off line parameter
`estimation. This limits the use of the method as a clinical
`tool.
`
`DESCRIPTION OF THE INVENTION
`
`It is an object of the present invention to provide a device
`for estimation of one or more respiratory parameters includ-
`ing oxygenation parameters and lung parameters relating to
`an individual in which the necessary quantities for enabling
`an estimation of respiratory parameters are collected auto-
`matically by a computer of the device so as to provide an
`automated estimation of said parameters.
`It is a further object to provide a device wherein the
`necessary measurements at varying oxygen levels are
`obtained in an at least semi-automated manner whereby the
`experimental time for said estimation may be reduced. By
`reducing the procedural time these techniques have potential
`for routine clinical use.
`
`It is a still further object to provide a device which is
`adapted for assessing a possible new target of the level of
`oxygen in the blood circulation based on the previously
`obtained measurement(s).
`It is a yet still further object to provide a device, which is
`adapted for assessing an appropriate change in the current
`level of oxygen in the inspired gas to obtain a given target
`of the level of oxygen in the blood circulation.
`The use of the device on humans is of particular interest,
`but the device may also be applied to farm animals such as
`pigs, or to domestic animals such as dogs.
`The device might be of value in all kind of patients in
`which hypoxemia occurs or may occur. These conditions
`may e.g. be selected from the group comprising left sided
`heart failure, adult respiratory distress syndrome, pneumo-
`nia, postoperative hypoxemia, pulmonary fibrosis,
`toxic
`pulmonary lymphoedema, pulmonary embolisms, chronic
`obstructive pulmonary disease and cardiac shunting.
`Thus, the present invention relates in a first aspect of the
`present invention to a device for determining one or more
`respiratory parameters relating to an individual, comprising
`a gas flow device having means for conducting a flow of
`inspiratory gas from an inlet opening to the respiratory
`system of the individual and a flow of expiratory gas
`from the respiratory system of the individual to an
`outlet opening,
`a gas-mixing unit for supplying a substantially homoge-
`neous gas to the inlet opening of the gas flow device,
`first supply means for supplying a first gas to an inlet of
`the gas mixing unit and having first control means for
`controlling the flow of the first gas,
`second supply means for supplying a second gas having
`an oxygen fraction different to the gas supplied from
`the first supply means to an inlet of the gas mixing unit
`and having second control means for controlling the
`flow of the second gas,
`a computer for determining said one or more respiratory
`parameters,
`
`4
`first detection means for detecting the level of oxygen
`(SaOz, SpOz, PaOz, PpOz) in the blood circulation of
`the individual and producing an output to the computer
`accordingly, and
`second detection means for detecting the level of oxygen
`(FIOZ, FE‘OZ, FEOZ, PIOZ, PE‘OZ, PEOZ) in the gas
`flow passing into or out of the respiratory system of the
`individual and producing an output to the computer
`accordingly, the computer being adapted for retrieving
`and storing at least two measurements being the con-
`current output produced by the first detection means
`and the second detection means within a data structure,
`in which the two stored outputs are mutually related, in
`data storage means associated with the computer, the at
`least two measurements being conducted at respective
`levels of oxygen in the gas flow passing into the
`respiratory system, the computer further being adapted
`for determining at
`least one respiratory parameter
`
`(Rdiff, shunt, V/Q, H-shift, V—shift) being descriptive
`of the condition of the individual, the determination
`being based on the at least two measurements.
`Hence, in its broadest aspect, the invention relates to a
`device for determining one or more respiratory parameters-
`relating to an individual. By the term “individual” is herein
`understood an individual selected from the group compris-
`ing humans as well as farm animals, domestic animals, pet
`animals and animals used for experiments such as monkeys,
`rats, rabbits, etc.
`By the term “respiratory parameters” is herein understood
`parameters relating to oxygen transport from the lungs to the
`blood, such as parameters related to abnormal ventilation,
`resistance to oxygen uptake from the lungs to the lung
`capillary blood, and parameters related to shunting of
`venous blood to the arterial blood stream. These respiratory
`parameters may be given as absolute values or relative
`values as compared to a set of standard values and the
`parameters may further be normalised or generalised to
`obtain parameters that are comparable to similar parameters
`measured for other individuals, at least for individuals of the
`same species.
`Thus, the computer may further be adapted for determin-
`
`ing at least two respiratory parameters (Rdiff, shunt, V/Q,
`H-shift, V—shift) being descriptive of the condition of the
`
`individual, and said parameter(s) (Rdiff, shunt, V/Q, H-shift,
`V—shift) may alternatively or additionally be generalised
`parameters being comparable to similar parameter(s) deter-
`mined for other individuals.
`
`In a preferred embodiment, the computer of the device is
`further adapted for performing a procedure at least once, the
`procedure comprising
`determining, based on at least two measurements, whether
`additional measurements are required,
`asserting a possible desired target defining a desired
`output of the first detection means,
`producing a possible control data item based on the target,
`and
`
`in the data structure, additional
`retrieving and storing,
`measurement results being the concurrent output pro-
`duced by the first detection means and the second
`detection means. The control data item produced
`thereby may be outputted to a human operator by
`means of an output device so that the operator can
`adjust the level of oxygen in the inspired gas flow.
`Alternatively, the control data item may be used by
`another part of or a computer program within the
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`US 7,008,380 B1
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`computer or by an external control device for automati-
`cally control of the means for controlling the flow to the
`gas-mixing unit of at least one gas.
`According to a preferred embodiment of the present
`invention,
`the second detection means are arranged for
`detecting the level (F102, P102) of oxygen in the gas flow
`passing into the respiratory system, and the device further
`comprises
`third detection means for detecting the level (FE'OZ, F
`E02, PE'OZ, PEOZ) of oxygen in the gas flow passing
`out of the respiratory system and producing an output
`to the computer accordingly, and fourth detection
`
`means for detecting variables (Vt, f, V) of the gas flow
`passing the respiratory system and producing an output
`to the computer accordingly, said output being suffi-
`cient for the computer to establish the volume flow of
`gas passing the respiratory system, the computer being
`adapted for retrieving and storing output from the third
`detection means and the fourth detection means within
`
`the data structure relating these stored output mutually
`as well as with the output from the first detection means
`and the second detection means retrieved simulta-
`
`neously. This/these measurement(s) enable(s) the com-
`puter to estimate or establish the oxygen consumption
`of the individual, either implicitly as part of the esti-
`mation of respiratory parameters, or the computer may
`further be adapted for explicitly establishing, based on
`said measurement(s), the oxygen consumption (V02)
`of the individual.
`
`It is advantageous for the device according to the present
`invention that
`the computer is adapted to determine a
`parameter relating to an equilibrium state of the overall
`oxygen uptake or consumption of the individual based on
`the output of at least one of the detection means, to compare
`said parameter with a predefined threshold value and to
`produce a control data item accordingly if said parameter
`exceeds said threshold value. By determining whether an
`equilibrium state of the individual is obtained the timing of
`the steps of the procedure can be controlled efficiently and
`the overall time for performing the procedure may be further
`reduced.
`
`It is also advantageous if the computer is adapted to asses
`the appropriate change in oxygen level in the inspired gas
`(F102) from the current oxygen level (F102) so as to achieve
`a given desired target oxygen level in the blood (SaOz,
`SpOz, PaOz, PpOz) and produce a control data item accord-
`ingly so that the oxygen level can be adjusted according to
`the data item. The actual adjustment may be performed by
`an operator of the device, in which case the data item is
`outputted to an output device. Alternatively and preferably
`the computer is adapted to operate the control means for
`controlling the flow to the gas mixing unit of at least one gas,
`in response to said control data item relating to the assessed
`change in oxygen level from the computer so as to change
`the oxygen level (F102) in the inspired gas flow accordingly.
`The data item may instead be outputted to an external
`device, which is suitable for performing an automated
`control of the control means so as to adjust the oxygen level
`accordingly.
`The assessment of change in oxygen level in the inspired
`gas may in an embodiment of the invention be based on a
`predefined set of data representing statistical distributions of
`variables stored within data storage means associated with
`the computer and on said measurements. Details of how this
`may be performed are disclosed in the detailed description
`of the invention. Alternatively, the assessment of change in
`
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`oxygen level in the inspired gas may be based on the rate of
`change of the output of at least one of the detection means
`in response to a change in oxygen level (F102) in the
`inspired gas flow. Typically, the oxygen level is changed
`stepwise or following a ramp function and the change over
`time of the oxygen level in the blood circulation or the level
`of oxygen in the expired gas is monitored. However, moni-
`toring of another gas, such as C02, or another variable of the
`patient may additionally or alternatively be employed.
`It is preferred that one gas is atmospheric air and that
`another of the gasses is more or less pure oxygen, i.e. has an
`oxygen fraction higher than that of atmospheric air, prefer-
`ably in the range 0.85 to 1.00. Alternatively or additionally,
`another gas may be supplied which has an oxygen fraction
`below that of atmospheric air, i.e. in the range of 0.00 to
`0.21, preferably of 0.00 to 0.05. Thereby the oxygen level of
`the inspired gas may be varied not only to level above that
`of atmospheric air but also below that level, thus providing
`a wide range of possible levels for performing measure-
`ments of the individual. The gas having a low oxygen
`fraction may be supplied from a source of more or less pure
`nitrogen N2 or another suitable physiologically neutral gas,
`such as helium H2, or it may be re-circulated expired gas
`from the individual, preferably after reduction of the level of
`CO2 in the expired gas.
`The device should ensure by means of a security arrange-
`ment that the oxygen saturation in the blood circulation of
`the individual is in the range of 65 to 100%, preferably for
`human beings in the range of 85 to 100% to avoid the risk
`of damage to organs. This condition varies for different
`species of animals.
`The first detection means is preferably arranged for
`detecting a variable relating to the saturation level of oxygen
`in the arterial blood stream by means of an invasive or a
`non-invasive technique, which latter is preferred. Thus, the
`first detection means is in an advantageous embodiment a
`pulse oximeter. Alternatively,
`the level of oxygen in the
`venous blood stream may be measured by means of an
`invasive or a non-invasive technique, the latter again being
`the preferred one.
`invention
`the present
`According to a second aspect,
`relates to a device for determining one or more respiratory
`parameters relating to an individual, comprising
`a gas flow device having means for conducting a flow of
`inspiratory gas from an inlet opening to the respiratory
`system of the individual and a flow of expiratory gas
`from the respiratory system of the individual to an
`outlet opening,
`a gas-mixing unit for supplying a substantially homoge-
`neous gas to the inlet opening of the gas flow device,
`first supply means for supplying a first gas to an inlet of
`the gas mixing unit and having first control means for
`controlling the flow of the first gas,
`second supply means for supplying a second gas having
`an oxygen fraction different to the gas supplied from
`the first supply means to an inlet of the gas mixing unit
`and having second control means for controlling the
`flow of the second gas,
`a computer for determining said one or more respiratory
`parameters,
`first detection means for detecting the level of oxygen
`(SaOz, Spoz, PaOz, PpOz) in the blood circulation of
`the individual and producing an output to the computer
`accordingly, and
`second detection means for detecting the level of oxygen
`(F102, FE‘OZ, FEOZ, P102, PE‘OZ, PEOZ) in the gas
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`US 7,008,380 B1
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`7
`flow passing into or out of the respiratory system of the
`individual and producing an output to the computer
`accordingly,
`the computer being adapted for retrieving and storing a
`first measurement being the concurrent output pro-
`duced by the first detection means and the second
`detection means within a data structure, in which the
`two stored outputs are mutually related, in data storage
`means associated with the computer,
`the computer
`being further adapted for performing a procedure at
`least once, the procedure comprising
`determining, based on data stored within the data struc-
`ture, whether additional measurements are required,
`asserting a possible desired target defining a desired
`output of the first detection means,
`producing a possible control data item based on the target,
`and
`
`retrieving and storing, in the data structure, additional
`measurement results being the concurrent output pro-
`duced by the first detection means and the second
`detection means.
`
`According to a third aspect, the present invention relates
`to a device for determining one or more respiratory param-
`eters relating to an individual, comprising
`a gas flow device having means for conducting a flow of
`inspiratory gas from an inlet opening to the respiratory
`system of the individual and a flow of expiratory gas
`from the respiratory system of the individual to an
`outlet opening,
`a gas-mixing unit for supplying a substantially homoge-
`neous gas to the inlet opening of the gas flow device,
`first supply means for supplying a first gas to an inlet of
`the gas mixing unit and having first control means for
`controlling the flow of the first gas,
`second supply means for supplying a second gas having
`an oxygen fraction different to the gas supplied from
`the first supply means to an inlet of the gas mixing unit
`and having second control means for controlling the
`flow of the second gas,
`a computer for determining said one or more respiratory
`parameters,
`first detection means for detecting the level of oxygen
`(SaOz, SpOz, PaOz, PpOz) in the blood circulation of
`the individual and producing an output to the computer
`accordingly, and
`second detection means for detecting the level of oxygen
`(F102, FE‘OZ, FEOZ, PIOZ, PE‘OZ, FEOZ) in the gas
`flow passing into or out of the respiratory system of the
`individual and producing an output to the computer
`accordingly,
`the computer being adapted for retrieving and storing at
`least a first measurement being the concurrent output
`produced by the first detection means and the second
`detection means within a data structure, in which the
`two stored outputs are mutually related, in data storage
`means associated with the computer,
`the computer
`further being adapted to asses the appropriate change in
`oxygen level in the inspired gas (FIOZ) from the current
`oxygen level (F102) so as to achieve a given desired
`target oxygen level in the blood (SaOz, SpOz, PaOz,
`PpOz) and produce a control data item accordingly.
`The second aspect as well as the third aspect of the
`invention is disclosed above in the most
`fundamental
`
`embodiment which according to the present invention may
`be combined with the additional features disclosed above
`
`with relation to the first aspect of the invention.
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`The device may be used to obtain and/or compare one or
`more respiratory parameters relating to one or more indi-
`vidual(s). The individual may be a healthy individual, at risk
`of suffering from hypoxemia, or suffering from hypoxemia.
`By the term “the individual is at risk of suffering from
`hypoxemia” is herein understood that the individual has a
`higher/increased risk of suffering from hypoxemia com-
`pared to a healthy individual. The increased risk of suffering
`from hypoxemia may e.g. be due to a hereditary predispo-
`sition, a post-operative condition and/or various diseases.
`By the term “hypoxemia” is herein meant that the oxygen
`saturation in the blood from the individual is below 92%.
`Examples of diseases that can cause hypoxemia are left
`sided heart failure, adult respiratory distress syndrome,
`pneumonia, postoperative hypoxemia, pulmonary fibrosis,
`toxic pulmonary lymphoedema, pulmonary embolisms,
`chronic obstructive pulmonary disease and cardiac shunting.
`The present invention also relates to a computer system
`comprising at least one general purpose computer having
`one or more computer programs stored within data storage
`means associated therewith,
`the computer system being
`arranged for as well as being adapted for determining one or
`more respiratory parameters according to the devices and/or
`methods disclosed above.
`
`Furthermore, the presen