Patent ID: 12186487

DETAILED DESCRIPTION

According to the disclosed embodiments, by sending a pressure pulse that contains multiple frequencies into the patients' lung, pressure and flow signals are collected, which represent the pressure drop across patient's respiratory system as well as the flow rate into and out from the patients' lung. The pressure pulse signal contains 5-25 Hz, which does not overlap with the patient's breathing frequency and is easily separated out using a Fast Fourier Transform (FFT). In addition, a 5-25 Hz pressure signal is spread out from the patient's upper airway down to the lower airway. By analyzing the pressure and flow relationship, the patient's lung impedance is derived, which includes both resistance and reactance information. This technique to derive the patient's airway impedance condition is employed to objectively assess an airway clearance device's therapy efficacy by analyzing an impedance curve change after stage 1 therapy (mucus is mobilized from lower airway to upper airway) and stage 2 therapy (mucus is facilitated to cough out). Data is sent to a remote computer for both patients and caregivers to assess. Based on the therapy efficacy assessment, clinicians decide whether a change in the therapy setting is needed or desired.

The disclosed embodiments also provide a three layer checking mechanism in the detection algorithm. In the first layer, deviation of the signal from the baseline is used as the main criteria to identify potential artifacts. The baseline is updated once a new baseline is found. In the second layer, the detected artifacts with continuous presence of less than two data points will be rejected as a false detection. In the third level, a breathing waveform is mapped onto the real time impedance curve to identify the intact breathing cycles. Breathing cycles contaminated by one or more artifacts will be rejected. The intact breathing cycles are connected to calculate the impedance, and a counter is set up to count the number of clean breathing cycles through detection of inhalation and exhalation based on detection of a slope change in the flow rate and pressure waveform. In some embodiments, a minimum number of breathing cycles of 8 may be used to ensure quality of the data.

The artifact detection/rejection mechanism is used to achieve accurate impedance measurement. Without this mechanism, the impedance measurement of the patient's lung will be contaminated by the artifacts and, therefore, lead to inaccurate results. If enough clean breathing cycles (flow rate, pressure) remain after the contaminated breathing cycles are rejected, accurate results are achieved.

A respiratory device10is provided inFIG.1. The details of the structure of a suitable respiratory device and related electrical components may be found in International Application No. PCT/SG2016/050166, filed Apr. 1, 2016, published as WO 2016/159889 A1 on Oct. 6, 2016, and titled “Manifold for Respiratory Device,” which is hereby incorporated herein in its entirety. See also U.S. patent application Ser. No. 15/901,114, filed Feb. 21, 2018, which is hereby incorporated herein in its entirety. Respiratory device10includes a housing12having a front wall14on which a display or graphical user interface16is accessible to enter user inputs into device10and to view displayed information regarding the operation of device10as shown inFIG.1. At a bottom region of front wall14of housing12, a hose is attached to a flow element24. Beneath the graphical user interface16there is an on/off button28that is pressed sequentially to turn device10on and off.

Device10is operable as an insufflation/exsufflation device or, as such devices are sometimes called, a cough assist device. Thus, device10is capable of applying positive pressure and negative pressure to a patient's airway, the positive pressure being applied during insufflation and the negative pressure being applied during exsufflation. The device10may be controlled to apply the positive insufflation pressure or the negative insufflation pressure to the patient through a patient interface (not shown) that is coupled to the flow element24. The user may select to switch between insufflation, exsufflation, and pause pressures in a manual mode of the device10or this is done automatically by device10in an automatic mode. In some embodiments, device10is operable to provide other modes of respiratory therapy such as continuous positive expiratory pressure (CPEP) and continuous high frequency oscillation (CHFO), just to name a couple. CPEP and CHFO are sometimes referred to herein, collectively, as Intrapulmonary Percussive Ventilation (IPV).

Referring toFIG.2, the flow element24includes an inlet segment52that is configured to couple to an outlet segment54. The inlet segment52includes a rounded body56and an inlet port58extending from the rounded body56. The rounded body56includes a retaining flange60that is configured to facilitate coupling the inlet segment52to the outlet segment54, as described below. A flange42extends around the rounded body56. The flange42steps down to an inner surface62. A plurality of notches64extend from the inner surface62into the flange42.

The outlet segment54includes a rounded body70and an outlet port72extending from the rounded body70. The outlet port72is configured to be coupled to a patient interface via a hose. The rounded body70includes an annular retaining flange74that is configured to facilitate coupling the inlet segment52to the outlet segment54. A pair of clamps76is configured to engage the retaining flanges60,74to secure the inlet segment52to the outlet segment54. A flange44extends around the rounded body70and steps down to an inner surface68. A plurality of tabs66extend from the flange44. When the outlet segment54is coupled to the inlet segment52, the flanges42and44are abutted against one another. The tabs66are secured within the notches66to align the inlet segment52and the outlet segment54. The inner surfaces62and68define a cavity within the flow element24.

Referring toFIG.3, the clamps76include a tongue and groove configuration to couple the outlet segment54to the inlet segment52. An end78of each clamp includes a groove92and a tongue94extending outward from the groove92. Likewise, as shown inFIG.5, the flange60also includes a tongue and groove configuration. Each end46includes a groove96and a tongue98extending from the groove96. The tongues94of each clamp76are configured to secured within the groove96of the flange60. Also, the tongues98of the flange60are configured to lock within the groove92of each clamp76.

A filter80is configured to position between the inlet segment52and the outlet segment54. The filter80positions between the rounded body56of the inlet segment52and the rounded body70of the outlet segment54when the inlet segment52is coupled to the outlet segment54. The filter80is retained in the cavity defined by the inner surfaces62and68. In some embodiments, the filter80includes a screen82surrounded by an outer rim84. The screen82and the outer rim84may be formed from metal or plastic. In some embodiments, the screen82may be a paper filter. A gasket86includes a groove88that is configured to receive the outer rim84of the filter80. The gasket86seals the filter within the flow element24so that any air passing through the flow element24passes through the screen82. Referring toFIG.4, the gasket86seals around the outer rim84and a portion of the screen82to seal the flow element24. Flow element24is sometimes referred to as a pneumotachometer or a pneumotach, for short.

Referring toFIG.6, when the inlet segment52is coupled to the outlet segment54, the inlet port58and the outlet port72form a flowpath90through the flow element24. In some embodiments, the flowpath90is a linear flowpath between the inlet port58and the outlet port72. The flowpath90passes through the filter80.

An inlet pressure port100extends from the rounded body56of the inlet segment52. The inlet pressure port100extends parallel to the inlet port58. An outlet pressure port102extends from the round body70of the outlet segment54. The outlet pressure port102extends parallel to the outlet port72. In the illustrative embodiment, the inlet pressure port100and the outlet pressure port102are aligned along an imaginary line104. The imaginary line104extends parallel to the flowpath90. That is, the inlet pressure port100and the outlet pressure port102extend parallel to the flowpath90. The inlet pressure port100and the outlet pressure port102are configured to couple to a differential pressure sensor (described below).

Referring toFIG.7, the flow element24is positioned within a housing120that is configured to be positioned within the respiratory device10. A printed circuit board128is positioned within the housing120and includes a pair of differential pressure sensors130,132. Referring toFIG.8a conduit134connects the outlet pressure port102to a first differential pressure sensor130of the circuit board128. A conduit136connects the inlet pressure port to the first differential pressure sensor130and the second differential pressure sensor132through a Y-splitter138. The first differential pressure sensor130is configured to output the pressure drop passing through the flow element24to derive a flow based on the resistance of the flow element24. The second differential pressure sensor132is configured to output a pressure drop across the patients' airway system. In one embodiment, the first differential pressure sensor130is a model number HSCMRRN016MD2A3 differential pressure sensor, and the second differential pressure sensor132is a model number HSCMRRN160MDSA3 differential pressure sensor, both available from Honeywell International Inc. of Morris Plains, N.J.

Based on the information derived from the differential pressure transducers132,130, an efficacy of the therapy administered to the patient from the respiratory device10is determined by passing pulses through the flow element24. Referring toFIG.9, three graphs are shown including a graph140of the patient's breathing waveform148in pressure144over time146and a graph of an external stimulus applied to the flow element24in the form of an impulse signal142containing multiple frequencies, as shown in the bottom right graph ofFIG.9. By combining the waveform142and the impulse signal148, a combined signal150is acquired, as show in the third graph ofFIG.9, which can be used in evaluating a patient's mechanical response to the impulse signal148.FIG.10illustrates the combined signal150converted by a Fast Fourier Transform, as shown in the left graph ofFIG.9. The Fast Fourier Transform graph152illustrates a power spectrum154as a function of frequency156. As illustrated inFIG.10, the patient's breathing cycle is represented by a peak158having frequency of approximately 0.5 Hz. The impulse signal148is represented by a peak160having a higher frequency of about 5 Hz.

Based on the graph152, a respiratory system impedance can be derived which gives the information on the patients' lung resistance and compliance using the below equations:

Zrs⁡(ω)=P⁡(ω)/V′(ω)=Rrs+iXrs=Rrs+i⁡(ω⁢I-1/ω⁢C)

Zrs(ω) represents an impedance of the patient's breathing cycle, Rrs represents the patient's lung resistance in cmH2Os/L, which is a measure of pressure divided by flowrate, and Xrs represents the patient's lung reactance in cmH2Os/L. Additionally, I represents a patient's lung inertia and C represents the patient's lung compliance. Notably, low frequency oscillations (f<20 Hz) are spread in a lower depth of the airway, and higher frequency oscillations (f>20 Hz) are spread in an upper portion of the airway. Accordingly, the patient's lung resistance and lung reactance before treatment are compared to the patient's lung resistance and lung reactance after therapy using the method shown inFIG.11.

At block170ofFIG.11, the impulse signal148is introduced to the patient's airway. The patient's lung impedance is calculated using the equation set forth above, at block172. Based on the patient's lung impedance an assessment of the patient's lung condition is evaluated, as indicated at block174. The therapy is then delivered to the patient, at block176. After therapy, another impulse signal148is introduced into the patient's airway to derive a new patient lung impedance, at block178. At block180, the new lung impedance is compared to the lung impedance prior to the therapy to assess the efficacy of the therapy.

For example,FIG.12illustrates a lung resistance curve190and lung reactance curve192at stage 1 of therapy during mucus mobilization when mucus in moved from the lower airway to the upper airway. The lung resistance curve190and the lung reactance curve192are shown in units of centimeters of water seconds per liter (cmH2Os/L) along the y-axis, and are illustrated over frequency in Hz along the x-axis. In the lung resistance curve190, the point200represents an overall resistance of the respiratory system at a frequency of 5 Hz. The point202represents the resistance of the conducting airways at 20 Hz. The line from point200to point202represents changes in the shape of resistance that are typically associated with heterogeneous obstruction and small airway disease. In the lung reactance curve192, the point210represents overall stiffening (i.e. loss of compliance) of the lungs and obstruction of small airways at a frequency of 5 Hz. The point212represents the frequency (10 Hz) at which the reactance is zero, which is indicative of an overall stiffening of the lungs and obstruction of small airways. The area214is indicative of overall stiffening of the lungs and obstruction of small airways. Lastly, a change in the point210represents the difference between low frequency inspiratory and expiratory resistance.

FIG.13illustrates a lung resistance curve220and a lung reactance curve222at stage 2 of therapy, when mucus is facilitated to cough out of the patient's airway. If the therapy is effective, the following trends should be observed. The resistance at 20 Hz should increase as shown by point224indicating an increase in upper airway resistance. Likewise, the resistance at 5 Hz should increase as illustrated by point226. The line228between 5 Hz and 20 Hz should decrease indicating that the lower airway resistance has decreased relative to the initial curve190. Further, in the lung reactance curve222, the new curve230should shift upward, relative to the initial curve192, indicating improved lung compliance.

FIG.14illustrates a lung resistance curve240and a lung reactance curve242at stage 3 after the therapy has ended. After therapy, the following trends should occur if the therapy is effective. The resistance at 20 Hz should decrease as represented by point250. The resistance at 5 Hz should decrease as represent by point252. Also, the new curve254from 5 Hz to 20 Hz should decrease, relative to the curve220. Each of these decreases is indicative of a decrease in both the upper airway and lower airway resistance. Further, the new reactance curve260will shift upward, relative to the curve230, indicating improved lung compliance.

While the above method may be utilized to determine the efficacy of a therapy treatment, there may be several factors that may affect the data. For example, a nose clip, a cheek support, sitting posture of the patient, or motion of the patient may create artifacts in the impedance data. Also, additional tubing, bending in the tubing, or an exhalation port may create artifacts. Artifacts may also be created by glottis closure, coughs, swallowing, or other breathing artifacts. For example,FIG.15illustrates a breathing pressure waveform300and a resistance curve302at 20 Hz as a function of pressure304(y-axis) over time306(x-axis). Artifacts are indicated by the line308. As can be seen, an artifact320occurs between 0.5 seconds and 1.5 seconds that may be indicative of leakage in the system. Another artifact322occurs between 2.5 seconds and 4 seconds that may be indicative of blockage in the system. In another example,FIG.16illustrates a breathing pressure waveform330and a resistance curve332at 5 Hz as a function of pressure334(y-axis) over time336(x-axis). An artifact340is present at 0.5 seconds, which may be indicative of coughing. Another artifact342is present between 1 second and 2 seconds, which may be indicative of burping. An artifact344is present at 2.5 seconds, which may be indicative of swallowing. Lastly, an artifact346is present at 3.5 seconds, which may be indicative of hemming.

FIG.17illustrates a method400for removing artifacts that occurs in three stages. In the first stage, at block402a mean value is calculated for 10 milliseconds of data. At block404, a deviation in the data is calculated by subtracting the original mean value from a newly acquired mean value and dividing by the original mean value to determine a percentage of deviation. It is then determined whether the deviation is greater than 13%, at block406. It should be noted that other percentages may be utilized to assess the data. At block408, a deviation greater than 13% is flagged, and the original mean value is updated with the new mean value, at block410. If at block406the deviation is not greater than 13%, the method proceeds to block420.

In the second stage, at block420, further deviation values are detected until all of the artifact points are detected. At block422, the data is assessed to determine whether any consecutive artifact points exist. If so, these points are flagged as real artifacts. At block424, artifact points that are not consecutive are flagged as false alarms. At block426, the breathing cycle is detected in the pressure flowrate waveform like those inFIGS.9-11. Inhaling and exhaling is flagged by adding the zero crossing point to the positive slope to acquire a sum, and dividing the sum by the negative slope.

In the third stage, the artifacts are mapped onto the breathing curve, and if an artifact is embedded in the breathing cycle, the breathing cycle is rejected, at block430. At block432, the impedance is calculated only for valid breathing cycles and the results are connected together to determine a curve without artifacts.FIGS.15and16illustrate resistance and reactance curves, respectfully, both with and without the artifacts.

Referring toFIG.18, a patient's lung resistance is illustrated as resistance450as a function of frequency452. A first line454illustrates the lung resistance with an artifact. A second line456illustrates the lung resistance without the artifact. At 5 Hz, frequency the lung resistance is higher in line454than in line456. Accordingly, by using the method set forth above to remove artifacts, the patient shows lower and improved lung resistance without the artifact, when compared to the lung resistance with the artifact.

Referring toFIG.19, a patient's lung reactance is illustrated as pressure460as a function of frequency462. A first line464illustrates the lung reactance with an artifact. A second line466illustrates the lung reactance without the artifact. At 20 Hz. and 25 Hz., the lung reactance is lower and improved without the artifact, when compared to the lung reactance with the artifact. Accordingly, by using the method set forth above to remove artifacts, the patient shows lower and improved lung reactance without the artifact, when compared to the lung reactance with the artifact.

FIG.20is another embodiment of a flow element500having a central body502and an inlet504and outlet506extending from the central body502. The inlet504has an end508with a diameter510that is less than a diameter512of the inlet504at the central body502. The outlet506has a diameter514that is equal to or greater than the diameter512. This trumpet shape or dialation of inlet port to a much bigger diameter facilitates achieving laminar flow so that the effective flow area is equivalent to the inlet port size. The central body502is sized to retain a filter530as illustrated inFIG.21.

Referring toFIGS.22and23, the filter530includes a gasket532that seals a honeycomb534within the central body502. The honeycomb534includes a plurality of holes536having a diameter of approximately 0.9 mm. The larger diameter reduces the chance of dust and/or moisture becoming stuck in the holes536when compared to a mesh or screen design. Accordingly, the user does not have to regularly clean the flow element500. The honeycomb534has a thickness538of approximately 1 cm. The thickness facilitates creating a desired pressure drop for sensing flow through the flow element500.

Although this disclosure refers to multiple embodiments, it will be appreciated that aspects of each embodiment may be utilized with other embodiments described herein.

Although this disclosure refers to specific embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the subject matter set forth in the accompanying claims.