WO2009105597A1

WO2009105597A1 - Pulsed oxygen concentrator bolus generation

Info

Publication number: WO2009105597A1
Application number: PCT/US2009/034610
Authority: WO
Inventors: Andrew M. Voto; Michael P. Chekal; Michael S. Mcclain; Dana G. Pelletier
Original assignee: Delphi Technologies, Inc.
Priority date: 2008-02-22
Filing date: 2009-02-20
Publication date: 2009-08-27

Abstract

A pulsed oxygen concentrator is provided. It comprises a selector for determining the desired mass of a gas bolus delivered to a user and at least one sieve bed having an internal gas and an internal gas pressure within a volume defined by the at least one sieve bed. At least one pressure sensor is operatively connected to the at least one sieve bed to measure the internal gas pressure of the sieve bed. At least one sensor operatively connected to the oxygen concentrator to measure at least one ambient atmospheric parameter is also provided and at least one temperature sensor is connected to the at least one sieve bed. At least one valve is in selective fluid communication with the at least one sieve bed and configured to regulate delivery of said internal gas to a user. A feed- forward control system is provided and has input parameters of the at least one pressure sensor, the at least one ambient atmospheric sensor or the at least one temperature sensor and the selector. At least one controlled output parameter is configured to control the at least one valve for delivering a bolus mass to the user.

Description

PULSED OXYGEN CONCENTRATOR BOLUS GENERATION

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to United States Provisional Application, Serial No. 61/066,665, filed February 22, 2008, the disclosure of which is incorporated by reference herein, in its entirety.

BACKGROUND OF THE INVENTION

[0002] A portable oxygen concentrating or generating system presents unique problems. It is intended to be easily moveable so that it can be easily carried about by a user, since the portability aspect of the invention improves the lifestyle of a person who requires oxygen. However, if the device is to be portable, it must be able to successfully function in significantly diverse environments, including temperature extremes and differing altitudes. This is significantly different than typical non-portable oxygen concentrating systems, such as those used to fill oxygen tanks - where the only portable aspect is the tank itself. As such, a portable oxygen generating device must be capable of function in diverse environments and be relatively lightweight. A portable oxygen generating device must also be in a small package suitable for portability and it should control noise, since it will be contiguous with the patient or user of the device.

[0003] A pulsed oxygen concentrator provides a specific bolus mass of gas once every time the patient breathes. It is desirable for the bolus to be tightly controlled regardless of environmental and system conditions. Typical pulsed oxygen concentrators use a valve to control the amount of gas that flows for each bolus, and a flow meter to provide feedback to control the duration that the valve is open, thereby delivering the desired bolus.

SUMMARY OF THE INVENTION

[0004] A pulsed oxygen concentrator is provided. It comprises a selector for determining the desired (or predetermined) mass of a gas bolus delivered to a user and at least one sieve bed having an internal gas and an internal gas pressure within a volume defined by the at least one sieve bed. At least one pressure sensor is operatively connected to the at least one sieve bed to measure the internal gas pressure of the sieve bed. At least one sensor operatively connected to the oxygen concentrator to measure at least one ambient atmospheric parameter is also provided and at least one temperature sensor is connected to the at least one sieve bed. At least one valve is in selective fluid communication with the at least one sieve bed and configured to regulate delivery of said internal gas to a user. A feedforward control system is provided and has input parameters of the at least one pressure sensor, the at least one ambient atmospheric sensor or the at least one temperature sensor and the selector. At least one controlled output parameter is configured to control the at least one valve for delivering a bolus mass to the user.

[0005] A method of providing a predetermined gas bolus mass to a user is provided. The method comprises sensing a gas pressure within at least one sieve bed operatively disposed in a pulsed oxygen concentrator, sensing at least one ambient atmospheric parameter and sensing at least one temperature adjacent the at least one sieve bed. The gas pressure, the at least one ambient atmospheric parameter and the at least one temperature are input into a feed forward controller. With the inputs, a gas bolus mass is released to substantially equal the predetermined gas bolus mass by feed-forward control.

[0006] The invention accurately estimates bolus flow using input from sensors that monitor both the environmental conditions and oxygen concentrator system conditions. As such, the invention eliminates the need for a flow sensor and/or flow meter.

[0007] These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

[0009] FIG. 1 is a schematic diagram of an oxygen generating system in accordance with the invention;

[0010] FIG. 2 is a functional schematic diagram of the invention;

[0011] FIG. 3 is a block diagram showing one aspect of the invention; and

[0012] FIG. 4 is a graph showing another aspect of the invention.

[0013] DETAILED DESCRIPTION OF THE INVENTION

[0014] The invention uses the fact that bolus flow can be considered in three segments that can be mathematically modeled. The three segments are increasing flow, steady flow, and decreasing flow. The increasing flow segment is associated with the opening of the valve. The steady state segment occurs if the valve is open long enough for flow to reach steady state. The decreasing flow segment is associated with closing the valve.

[0015] Referring now to the drawings, where the invention will be described with reference to specific embodiments, without limiting same, and where like numerals, are use for like elements, an oxygen generating system or device 10, suitable for use with embodiments of the invention, is shown in FIG. 1. It is to be understood that any oxygen generating system may be suitable for use with the invention exemplified in FIGS. 2-4, various examples of which (not shown) are oxygen generating system(s) having fill valves (any suitable combination of 2-way, 3-way, 4-way valves, etc.), vent valves (any suitable combination of 2-way, 3-way, 4-way valves, etc.), a product tank(s), bleed orifice(s) and patient valving. Generally a nitrogen-adsorption process employed by the oxygen generating system may be a pressure swing adsorption (PSA) process or a vacuum pressure swing adsorption (VPSA) process, and such processes operate in repeating adsorption/desorption cycles. [0016] The oxygen generating device of the present invention includes a housing 11 having an inlet 13 formed therein. The oxygen generating device 10 is portable so that it can be easily carried about by a user. However, it will be appreciated that the present invention is suitable for any oxygen generating device, regardless of portability, where the features of the present invention are useful or desired.

[0017] The inlet is configured to receive a feed gas from the ambient atmosphere, the feed gas including at least oxygen and nitrogen. The oxygen generating device also includes at least one sieve bed. In the example shown in FIG. 1, the oxygen generating device 10 includes a first sieve bed 12 and a second sieve bed 14, each in selective fluid communication with the feed gas. In an embodiment, each of the first and second sieve beds 12, 14 are configured to selectively receive the feed gas during a predetermined supply period. The first and second sieve beds 12, 14 receives the feed gas via first and second supply conduits 16, 18, respectively.

[0018] The first and second supply conduits 16, 18 are generally operatively connected to respective first and second supply valves (or inlet valves) 20, 22. In a non- limiting example, the first and second supply valves 20, 22 are two-way valves. As provided above, the nitrogen-adsorption process employed by the oxygen generating device 10 operates via cycles, where one of the first or second sieve beds 12, 14 vents purge gas (i.e. nitrogen-enriched gas), while the other of the first or second sieve beds 12, 14 delivers oxygen-enriched gas to the user. During the next cycle, the functions of the respective sieve beds 12, 14 switch so that venting occurs from the sieve bed that previously was delivering oxygen-enriched gas, while oxygen enriched gas is delivered from the sieve bed that in the prior cycle was venting. Switching is accomplished by opening the respective feed gas supply valve 20, 22 while the other of the feed gas supply valves 20, 22 is closed. More specifically, when one of the first or second sieve beds 12, 14 is receiving the feed gas, the respective one of the first or second supply valves 20, 22 is in an open position. In this case, the feed gas is prevented from flowing to the other of the first or second sieve beds 12, 14. In an embodiment, the opening and/or closing of the first and second supply valves 20, 22 may be controlled with respect to timing of opening and/or closing and/or with respect to the sequence in which the first and second supply valves 20, 22 are opened and/or closed.

[0019] The feed gas is compressed via a compressor 24 prior to entering the first or second supply conduits 16, 18. In a non-limiting example, the compressor 24 is a scroll compressor. As shown in FIGS. 1 and 2, the compressor 24 includes a suction port 52 configured to draw in a stream of the feed gas from the inlet 13.

[0020] After receiving the compressed feed gas, the first and second sieve beds 12, 14 are each configured to separate at least most of the oxygen from the feed gas to produce the oxygen-enriched gas. In an embodiment, the first and second sieve beds 12, 14 each include the nitrogen-adsorption material (e.g., zeolite, other similar suitable materials, and/or the like) configured to adsorb at least nitrogen from the feed gas. As schematically shown in phantom in FIG. 1, the sieve beds 12, 14 are operatively disposed in a housing 11 that includes sieve module 26.

[0021] In a non- limiting example, the oxygen-enriched gas generated via either the PSA or VPSA processes includes a gas product having an oxygen content ranging from about 70 vo 1% to about 100 vol% of the total gas product. In another non-limiting example, the oxygen-enriched gas has an oxygen content of at least 87 vol% of the total gas product.

[0022] A user conduit 28 having a user outlet 30 is an alternate selective fluid communication with the first and second sieve beds 12, 14. The user conduit 28 may be formed from any suitable material, e.g., at least partially from flexible plastic tubing. In an embodiment, the user conduit 28 is configured substantially in a "Y" shape. As such, the user conduit 28 may have a first conduit portion 28a and a second conduit portion 28b, which are in communication with the first sieve bed 12 and the second sieve bed 14, respectively, and merge together before reaching the user outlet 30. The user outlet 30 is an opening in the user conduit 28 configured to output the substantially oxygen-enriched gas for use by the patient. The user outlet 30 may additionally be configured with a nasal cannula, a respiratory mask, or any other suitable device (not shown), as desired. [0023] In the embodiment shown in FIGS. 1 and 2, the oxygen delivery device 10 also includes a sieve bed pressure sensor 37, 39 for the sieve beds 12, 14, respectively, and a sieve bed temperature sensor 44 configured to measure the pressure and temperature, respectively, of the first and second sieve beds 12, 14 during the PSA process. It will be appreciated that a single pressure sensor may also be used to measure the pressure of each of the sieve beds 12, 14. The device 10 further includes an ambient pressure sensor 45 and an ambient temperature sensor 47 to measure the pressure and temperature, respectively, of the ambient environment.

[0024] At least the compressor 24, the first and second supply valves 20, 22, and the first and second patient (or user) delivery valves 32, 34 are controlled by a controller 54. The sieve bed pressure sensors 37, 39, the sieve bed temperature sensor 44, the ambient pressure sensor 45, and the ambient temperature sensor 47 measure parameters that are inputs to the controller 54. In a non-limiting example, the controller 54 is a microprocessor including a memory.

[0025] A motor 56 drives the components of the oxygen generating system 10 including the compressor 24, the sieve beds 12, 14, the controller 54, the valves 20, 22, 32, 34, 40, 42, and the sensors 37, 39, 44, 45, 47. The motor 56 is powered by a battery (not shown) located on the exterior of the housing 11. In a non-limiting example, motor 56 is a DC brushless, three-phase motor. Further, the system 10 includes a fan 58 configured to cool the compressor 24 and the motor 56.

[0026] The first conduit portion 28a and the second conduit portion 28b may be configured with a first patient (or user) delivery valve 32 and a second patient (or user) delivery valve 34, respectively. In the embodiment shown, the first and the second user valves 32, 34 are configured as two-way valves. Thus, it is contemplated that when the oxygen-enriched gas is delivered from one of the first and second sieve beds 12, 14, to the user conduit 28, the respective one of the first or second user valves 32, 34 is open. When the respective one of the first or second user valves 32, 34 is open, the respective one of the first or second feed gas supply valves 20, 22 is closed. [0027] The nitrogen-adsorption process selectively adsorbs at least nitrogen from the feed gas. Generally, the compressed feed gas is introduced into one of the first or the second sieve beds 12, 14, thereby pressurizing the respective first or second sieve bed 12, 14. Nitrogen and possibly other components present in the feed gas are adsorbed by the nitrogen-adsorption material disposed in the respective first or second sieve bed 12, 14 during an appropriate PSA/VPSA cycle. The pressure of respective first or second sieve beds 12, 14 is released based by opening one of valve 32 or 34 for a time to deliver a bolus mass of oxygen enriched gas to a patient or user, upon a suitable trigger. The trigger may simply be a predetermined amount of time, or detection upon reaching a predetermined target pressure, or detection of an inhalation, and/or another suitable trigger. At this point, the nitrogen-enriched gas (including any other adsorbed components) is also released from the respective first or second sieve bed 12, 14 and is vented out of the system 10 through a vent conduit for the respective first or second sieve bed 12, 14.

[0028] As used herein, a "masked" time or the like language may be defined as follows. Following a dynamically adjusted user oxygen delivery phase from the first or second sieve bed 12, 14, breath detection may be "masked" for a predetermined masking time, for example, during the dynamically adjusted oxygen delivery phase and during a predetermined amount of time following the delivery phase. It is understood that such predetermined masking time may be configured to prevent the triggering of another dynamically adjusted user oxygen delivery phase before sufficient substantially oxygen- enriched gas is available from the other of the second or first sieve bed 14, 12. As used herein, sufficient substantially oxygen-enriched gas may be a pulse having a desired oxygen content. In an embodiment, the predetermined masking time may be short in duration. As a non-limiting example, the predetermined masking time may be about 500 milliseconds in length. In an alternate embodiment, this masking time may also be dynamically adjusted, e.g., based on the average breath rate. Further, in order to accommodate a maximum breathing rate of 30 Breaths Per Minute (BPM), a maximum mask time of 2 seconds may be used, if desired. [0029] As shown in FIG. 1, the nitrogen-enriched gas in the first sieve bed 12 is vented through the vent port/conduit 36 when a first vent valve 40 is open, and the nitrogen- enriched gas in the second sieve bed 14 is vented through the vent conduit 38 when a second vent valve 42 is open. The vent conduits 36 and 38 merge into the main vent conduit 58. It is to be understood that venting occurs after each oxygen delivery phase and after counterfilling, each described further hereinbelow. The gas not adsorbed by the nitrogen- adsorption material (i.e., the oxygen-enriched gas) is delivered to the patient/user through the user outlet 30.

[0030] In one embodiment, delivery of the bolus mass of oxygen-enriched gas occurs during or within a predetermined amount of time (i.e., a masked time) after the oxygen delivery phase from the respective first or second sieve bed 12, 14. For example, the oxygen delivery system 10 may be configured to trigger an output of a predetermined volume of the oxygen-enriched gas from the sieve bed 12 upon detection of an inhalation by the user. Detection of an inhalation may be accomplished any number of ways. In the embodiment shown in FIG. 1, a breath detection device 46 is used. The predetermined bolus mass, which is at least a portion of the oxygen-enriched gas produced, is output through the user conduit 28 and to the user outlet 30 during an oxygen delivery phase.

[0031] Since a predetermined bolus mass of gas is delivered to the user, it is contemplated that at least a portion of the oxygen enriched gas will not be delivered to the user during or after the masked time to the user outlet 30. The first and second sieve beds 12, 14 are configured to transmit that "left-over" oxygen enriched gas, if any, to the other of the first or second sieve bed 12, 14. This also occurs after each respective oxygen delivery phase. The portion of the remaining oxygen-enriched gas is transmitted via a counterfill flow conduit 48. The transmission of the remaining portion of the oxygen-enriched gas from one of the first or second sieve beds 12, 14 to the other first or second sieve beds 12, 14 may be referred to as "counterfilling."

[0032] As shown in FIG. 1, the counterfill flow conduit 48 is configured with a counterfill flow valve 50. In a non- limiting example, the counterfill flow valve 50 is a two- way valve. The counterfϊll flow valve 50 is opened to allow the counterfϊlling of the respective first and second sieve beds 12, 14.

[0033] Referring now to FIGS. 2 and 3, the sieve bed pressure sensors 37, 39, and the sieve bed temperature sensor 44 measure internal system parameters of the sieve bed, and in the case of the sieve bed temperature sensor 44, measures temperature either in the sieve beds 12, 14 or adjacent thereto, giving a relatively accurate temperature in the temperatures in the sieve beds 12, 14. The ambient pressure sensor 45 and the ambient temperature pressure sensor 47 measure ambient atmospheric parameters, all of which are inputs to the controller 54. As will be described in more detail below, the controller 54 uses a feed forward control to affect output from the controller 54. The feed forward control receives, at least one of the sieve bed pressures, at least one of the sieve bed temperatures, and at least one atmospheric parameter to execute one or more algorithms for controlling a delivering a bolus mass to a user.

[0034] The controller 54 receives a signal for a desired (or predetermined) bolus mass from bolus mass input selector 59. The bolus mass is selected from one of a number of settings on input selector 59, generally located on the exterior of the oxygen generating device 10. The bolus size, in one embodiment being in functional increments beginning at 8.5 ml per setting, is typically prescribed by the patient's health care provider. Thus, a setting of "2" would equate to a 17 ml bolus being the predetermined bolus size selected. A bolus generating system 70, shown in FIG. 2, will generate a bolus mass to be delivered to the user that varies in size from the predetermined gas bolus mass selected by 10% or less.

[0035] As will be described in detail below, controller 54 takes various inputs from bolus generating system 70, uses the flow equations below, and determines the mass of the bolus to be delivered by integrating the flow equations over time for each segment of flow, shown in FIG. 4. By evaluating the integrated flow equations with various valve timing scenarios, it is possible to determine the appropriate timing for valves 32 or 34 to deliver a desired bolus mass that is about the desired bolus mass or selected predetermined bolus mass. Details of the equations are as follows:

Beginning with the equation for the steady state segment:

ΔP represents the gauge sieve pressure

Pi is the absolute sieve pressure.

R is the universal gas constant

T is temperature in Kelvin

Ci and C₂ are calibration constants.

[0036] This equation represents the peak flow that would occur if the patient valve 32 or 34 were open long enough for peak flow to be reached, and assumes that the pressure from one or the other of sieve beds 12, 14 are held constant while flow continues. Since the patient valve 32, 34 is only open for a short period of time, a constant pressure assumption can be used to provide accurate valve timing.

[0037] In order that controller use the equations herein disclosed, calibration constants must be determined. A set of calibration tests are performed for a representative oxygen concentrator 10 in an environmental chamber, the calibration constants being selected to match the empirical data from the calibration tests. For example: in order to fit this equation to empirical data, a value of 0.2 was used for C₂, and then Ci was calculated in order to match the actual peak flow recorded on a representative oxygen concentrator at 2LPM flow setting and at 23°C and 900 Feet (altitude). Iterations of the equation with different values for C₂ can be done until the results from the equation acceptably match the empirical data.

[0038] In order to have empirical data at relevant and convenient conditions for evaluation of the constants, a series of tests were run. The series of tests were run using the representative oxygen concentrator 10 with a flow meter and oxygen sensor installed to determine the sieve pressure required to produce 90 percent purity oxygen over a range of altitudes (expressed as barometric pressures) and temperatures with the flow setting at 2LPM.

[0039] Relevant data is gathered and is used in equation [1] to create a matrix of estimated peak flow for 3 parameters (Sieve Pressure, Temperature, and Barometric Pressure). C₂ is chosen so that the peak flow is 23 SLPM at 900 feet and 23C (296K), and Ci is varied so that the other portions of the matrix fit empirical results. For the representative system, Equation [1] gives acceptable estimates of the empirical data. Once the constants Ci and C₂ are determined, they are hard coded into the equation residing in controller 54.

[0040] Referring now to FIG. 4, showing a plot of bolus flow over time in discrete curves, the curves are of a rising exponential form and a decaying exponential form, each having a respective time constant. In order to curve fit this waveform, the following definitions apply:

to = the time when the rising edge begins t_c = the time when the valve begins closing ti = the time when the flow falling edge begins t₂ = the time when the flow has come back to zero τ_r = the rising edge time constant i_f = the falling edge time constant

Q_mp = peak flow

Qmr = rising flow

Q_mf = decreasing flow

Cciose = the time it takes the valve to close (time between valve electrical signal and when flow starts decreasing)

The flow then can be described as:

xLmr xLmp V ) between to and ti and

(t-h )

Urnf ^~ xlmr V^l / ^e between ti and t₂ The bolus is the integration of flow:

BoIuS = (¹Q^ ₊ (² Q s_nmf

Solving the definite integrals with t₂ at infinity yields:

Bolus= (t_l -t₀) + Q (τ_f -τ_r) + P(τ_re ^Tr -τ_fe ^Tf ) _[2]

Defining:

(ti-to) = the time that the patient valve is open,

(t_c-t₀) = the Patient Time (PTT), and

(ti-tc) = Cdose, a calibration value representing the time for the valve to close.

Substituting and rearranging in [2] :

(PTT+C_dose) (PTT+C_dose)

Bolus = Q_mp(PTT ₊ C_close) ₊ Q_mp(τ_f - τ_r) ₊ Q_mp (τ_re ^τ' - τ_fe ^τ? ) [3]

[0041] It will be appreciated that Patient Time (PTT) is that time between when one of patient valves 32, 34 is opened and when that same patient valve 32, 34 begins closing. Equation [3] cannot be easily inverted into the form PTT=/(Bolus). It must be calculated through iteration, or a sweep of Patient Time (PTT) values. Since the range of possible PTT values is limited, this is practical.

[0042] Before Equation [3] can be used, however, the constants τ_r, Tf and C_ci_ose are determined. One method for determining the constants is by curve fitting a test flow curve recorded at a known temperature and altitude as in FIG. 4. For example, if FIG. 4 was taken at T= 23C and 900 feet (14.198 psi), Q_mp (peak flow) is known, and the constants τ_r, if and can be determined by fitting the flow equations to the curve in FIG. 4. A reasonably accurate approximation of the time constants can be scaled from a plot of a representative flow curve, and C_ci_osecan be determined by superimposing a plot of valve control timing over the flow curve. [0043] It has been determined that the constants τ_r, if and C_ci_ose may be determined at a single set of conditions yet remain applicable to the range of conditions. To verify the applicability over the range of conditions, Patient Time (PTT) is iterative Iy determined using a known bolus value and Q_mp (peak flow). The determined PTT time can be compared to empirical data. A second verification method is to use empirical PTT times and Qmp (peak flow). The calculated bolus values can then be compared to empirical bolus values.

[0044] In the example, the bolus determined by using the method above and delivered to the user is within about 10% of the predetermined bolus initially selected from bolus mass input selector 59. Thus, by using the methods above, a substantially accurate bolus can be delivered to the user utilizing inputs including sieve pressure, temperature and barometric pressure as inputs to the equations provided with calibration constants determined at a single temperature and barometric pressure.

[0045] Thus, as shown in FIGS 2-4, controller 54 receives a signal from sieve bed pressure sensors 37, 39, temperature sensor 44 located within housing 11 and adjacent to sieve beds 12, 14 and an ambient atmospheric parameter sensor, which is one of ambient pressure sensor 45 or an ambient temperature sensor 47. Controller also receives a signal indicating the desired (or predetermined) gas bolus mass from bolus mass input selector 59. With these inputs, controller, using the above equations, determines when to open and close patient valves 32 or 34 to release the desired gas bolus mass to the user.

[0046] While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description.

Claims

What is claimed is:

1. A pulsed oxygen concentrator, comprising:

a selector for determining a desired mass of a gas bolus to be delivered to a user;

at least one sieve bed having an internal gas and an internal gas pressure within a volume defined by the at least one sieve bed;

at least one pressure sensor operatively connected to said at least one sieve bed to measure the internal gas pressure of said sieve bed;

at least one sensor operatively connected to the oxygen concentrator to measure at least one ambient atmospheric parameter;

at least one temperature sensor connected to said at least one sieve bed;

at least one valve in selective fluid communication with said at least one sieve bed and configured to regulate delivery of said internal gas to a user; and

a feed- forward control system having input parameters of said at least one pressure sensor, said at least one ambient atmospheric sensor or said at least one temperature sensor and said selector and at least one controlled output parameter configured to control the at least one valve for delivering said bolus mass delivered to said user.

2. The pulsed oxygen concentrator of claim 1, wherein said at least one sensor is configured to measure at least one of ambient atmospheric pressure or ambient atmospheric temperature.

3. The pulsed oxygen concentrator of claim 1, wherein said at least one controlled output parameter is a Patient Time.

4. The pulsed oxygen concentrator of claim 1, wherein said feed- forward control system includes at least one predetermined calibration constant.

5. The pulsed oxygen concentrator of claim 4, wherein said at least one predetermined calibration constant is an increasing flow time constant, a decreasing flow time constant, a valve closing constant, a first calibration constant, a second calibration constant, or combinations thereof.

6. The pulsed oxygen concentrator of claim 5 wherein said feed- forward control system is configured to determine said Patient Time by iterative evaluation of said bolus mass as a predetermined function of Patient Time within bounds of a Maximum Patient Time and a Minimum Patient Time.

7. The pulsed oxygen concentrator of claim 5, wherein said feed- forward control system is configured to determine said Patient Time by evaluation of bolus mass as a predetermined function of said Patient Time using interval halving, or other successive approximation techniques.

8. The pulsed oxygen concentrator of claim 1, wherein said feed- forward control system is configured to determine said Patient Time by iterative evaluation of said bolus mass as a predetermined function of Patient Time within bounds of a Maximum Patient Time and a Minimum Patient Time.

9. The pulsed oxygen concentrator as defined in claim 1, wherein said feedforward control system is configured to determine said Patient Time by evaluation of bolus mass as a predetermined function of Patient Time using interval halving, or other successive approximation techniques.

10. A method of providing a predetermined gas bolus mass to a user, the method comprising:

sensing a gas pressure within at least one sieve bed operatively disposed in a pulsed oxygen concentrator; sensing at least one ambient atmospheric parameter;

sensing at least one temperature adjacent said at least one sieve bed;

inputting said gas pressure, said at least one ambient atmospheric parameter and said at least one temperature to a feed forward controller; and

controlling a gas bolus mass to substantially equal said predetermined gas bolus mass by feed-forward control.

11. The method of claim 10, further comprising determining calibration constants by evaluating a flow curve of said pulsed oxygen concentrator at a predetermined ambient atmospheric temperature and a predetermined ambient atmospheric pressure.

12. The method of claim 10, further comprising determining a Patient Time required to release said predetermined gas bolus mass by iterative Iy evaluating bolus mass as a function of said Patient Time until said Patient Time associated with said predetermined gas bolus mass is realized.

13. The method of claim 10,, further comprising determining a Patient Time required to release said predetermined gas bolus mass by using interval halving or other successive approximation techniques to evaluate bolus mass as a function of Patient Time until said Patient Time associated with said predetermined gas bolus mass is realized.

14. The method of claim 10, further comprising determining a Patient Time required to release said predetermined gas bolus mass and closing at least one valve in selective fluid communication with said at least one sieve bed when said Patient Time is reached.

15. The method of claim 14, wherein a calculation time for determining the Patient Time associated with said predetermined gas bolus mass is less than said Patient Time associated with a smallest desirable predetermined gas bolus mass.

16. The method of claim 10, further comprising determining a Target Patient Time prior to an initiation of release of said predetermined gas bolus mass, and determining a Patient Time associated with said predetermined gas bolus mass by multiplying said Target Patient Time by a ratio of a sieve pressure used in determining said Target Patient Time to a sieve pressure substantially at the time of said initiation of release of said predetermined gas bolus mass.

17. The method of claim 16, wherein a calculation time for determining said Patient Time associated with said predetermined gas bolus mass is less than said Patient Time associated with a smallest desirable predetermined gas bolus mass.

18. A method of providing a predetermined gas bolus mass to a user, the method comprising:

sensing a gas pressure within at least one sieve bed operatively disposed in a pulsed oxygen concentrator;

sensing at least one ambient atmospheric parameter;

sensing at least one temperature adjacent said at least one sieve bed;

inputting said gas pressure, said at least one ambient atmospheric parameter and said at least one temperature to a feed forward controller;

controlling a delivered gas bolus mass to substantially equal said predetermined gas bolus mass by feed-forward control; and

delivering said delivered gas bolus mass to said user.

19. The method of claim 18, wherein said delivered gas bolus mass varies in size from said predetermined gas bolus mass by 10% or less.