Oscillatory pressure device for removing the mucus

[0002] The present invention relates to a device for extracting mucus from the bronchial and pulmonary walls of people suffering in particular from cystic fibrosis for the purpose of improving their condition significantly by reducing the limitations of medical care.

[0003] The lungs are covered by a liquid film a few micrometers thick that is normally very fluid and serves to protect pulmonary cells by insulating them from direct contact with air in the lungs. Cilia oscillate freely in this normally highly fluid liquid.

[0004] Recall that the fundamental problem associated with this fatal genetic disease is that all exocrine secretions from different bodily organs are abnormally viscous, the origin of this hyperviscosity among individuals suffering from cystic fibrosis being genetic. For this reason patients afflicted with cystic fibrosis have serious digestive and, especially, respiratory problems. Consequently, the mucus that bathes the lungs, and which is very difficult to remove, gradually obstructs the pulmonary alveoli, making breathing difficult, if not impossible. This mucus, in addition to the mechanical obstruction of the alveoli and interference of the natural oscillation of the cilia, is a significant focus of microbial contamination.

[0005] The objective of the present invention is the deliberate, controlled evacuation of all this additional mucus by modification of its rheological properties. Until now medical treatment involving mucus expectoration consisted principally in a form of respiratory kinesitherapy intended to promote the evacuation of mucus by controlled pressure on the patient's thorax. This method is known as clapping. The patient may then evacuate a small part of this mucus by spitting it out. However, the vibrations of the thorax initiated by the doctor doing the clapping are quickly damped in the lungs and elsewhere. Because of the viscosity of the mucus the effectiveness of such a method is also limited to pulmonary regions where the bronchi are sufficiently large in diameters

[0006] The invention is based on the property, not previously employed, of the thixotropy that is characteristic of pulmonary mucus. Thixotropy refers to the “phenomenon by which certain mixtures pass from a gel to a liquid state through mild agitation” (Larousse-Grande Dictionnaire Encyclopedique). In this case pulmonary mucus is thixotropic to the extent that it undergoes a transition from a viscous to a liquid state when it is agitated by the vibration of the air contained in the lungs and bronchi. This thixotropy is produced at frequencies of a few hertz, depending on the condition of the patient. The process thus involves generating, throughout the entire volume of the lungs, oscillatory changes in pressure, frequency, and amplitude are appropriate to the specific state of the patient's mucus in order to obtain the minimum viscosity of this mucus.

[0007] For these vibrations to affect the entire lung, the air inhaled by the patient must vibrate. Additionally, in order to expulse this mucus, it is preferable that the phenomenon of thixotropy occur during exhalation. Exhalation must thus be controlled and result in expectoration.

[0008] It is simple enough to cause the patient to cough—as described below-by superimposing on the oscillatory pressure variations of the volume of air within the lungs a slight negative pressure compared to the atmospheric pressure of this same volume of air. The extent of this negative pressure must be small enough and its duration sufficiently short that it does not lead to the collapse of the bronchial walls. These oscillatory pressure variations are obviously arrested during inhalation so as not to produce any reciprocal movement of the mucus, which would quickly become viscous again.

[0009] The device according to the invention described below facilitates dislodgment through fluidification and evacuation of the mucus of the bronchial walls by means of controlled, periodic oscillatory variations in negative pressure compared to atmospheric pressure and increasing variations in amplitude, which are, however, adjustable so that they may be adapted to the specific viscosity of bronchial mucus, which is not provided for in patents DE-A-4029680 and U.S. Pat. No. 5,116,088.

[0010] The device referred to in DE-A-4029680 is characterized by the periodic interruption of the air flow exhaled into an adjustable oral nozzle, implying that the magnitude of the vibrations of air pressure is neither adjustable nor increasing. According to patent U.S. Pat. No. 5,116,088, volumes of air pulsed at frequencies that are adjustable but slightly higher in pressure than the pressure of the air inhaled, are delivered throughout the inhalation phase of respiration.

[0011] The simple device of the invention represents the fundamental basis of a technology capable of being optimized in its implementations, including features synergistically associated that we choose not to develop here.

[0012] This device must respond to the following constraints: 1) it must produce throughout the bronchi and lungs oscillatory variations of negative pressure in the air of the lungs during exhalation, sudden periodic variations of increasing amplitude and frequency that are designed to provoke thixotropy of the pulmonary mucus, 2) it must take advantage of the fluidity of the mucus, causing it to travel to the exterior of the lungs, and evacuate it through the expectoration caused by the predefined negative pressure

[0013] The single drawing of FIG. 1 illustrates the fundamental principle of the device according to the invention. This principle makes possible the construction of an inexpensive and compact apparatus no more than ten cubic decimeters in size.

[0014] A respiratory mask (1) is applied to the mouth of the patient. This mask is connected by a flexible tube (2) to a recipient (3) in which a pump (4) creates a pressure drop of approximately 100 mbar, adjustable by means of an electrovalve (5) whose discharge into the atmosphere is variable Two other small conduits (6) balance the pressure around the tympanum to avoid any painful resonance effect.

[0015] A tube (7) of length (l) communicates with the ambient air by means of an orifice (13) whose diameter (d) is variable and controlled by a flow control device (14), and which, forming part of the recipient (3), is hermetically and cyclically sealed by means of a metal check valve (8) containing an elastic covering, such as, for example, rubber (9).

[0016] This alternating seal is obtained by means of a coil (10), which attracts the metal check valve (8) by a simple electromagnetic effect. When no electrical current flows in the coil (10), powered by the low-frequency generator (11), the check valve (8) is automatically pushed back by springs (12).

[0017] Pressure oscillations ΔP obtained in the recipient and thus in the lungs of the patient obey the following law: $\Delta P=\frac{\pi ·d^4·\mathrm{Pa}·\left(\mathrm{Pa}-P\right)}{128·\eta ·\mathrm{VO}·f·l}$

[0018] where

[0019] D=diameter of the orifice (13) of tube (7)

[0020] 1=length of tube (7)=viscosity of air

[0021] VO=volume of recipient (3) and lungs

[0022] Pa=atmospheric pressure

[0023] P=(static) pressure in recipient (3) and lungs

[0024] f=frequency of closure of orifice (13)

[0025] Adjustment of the diameter of this orifice (13), which modifies the amplitude of the oscillatory variations in negative pressure ΔP, can be simply obtained by restricting the entry of ambient air by modifying the position of the flow modulator (14).

[0026] These oscillatory variations of negative pressure ΔP can also be obtained by modifying the length (l) of the tube (7).

[0027] The pressure curve for the recipient (3) and the lungs is thus that shown in the single drawing of FIG. 2:

[0028] The duration of forced exhalation Te and the gradual drop P in pressure must be less than the time constant associated with the collapse of the bronchial walls.

[0029] The gradual pressure drop P causes forced expectoration.

[0030] Oscillatory pressure changes ΔP of increasing amplitude dislodge mucus in the bronchial walls and, when the frequency is brought to an optimal value, provoke thixotropy of the mucus by making it more fluid. This mucus is then evacuated to the exterior by forced expectoration of the air in the lungs generated by the pressure drop.

[0031] Inhalation takes place without pressure vibration to prevent any possible return of mucus, which would become more viscous in the bronchi and lungs.