IL31003A - Therapeutic inhaler - Google Patents

Description

.

THERAPEUTIC INHALER THERAPEUTIC INHALER Abstract of the Disclosure: An inhaler for self-administration of a volatile drug for analgesic purposes and comprising a tubular body with a mouthpiece at one end for insertion into a patient's mouth, an absorbent material within the tubular body for holding the liquid agent and a cap on the end of the tubular body opposite the mouthpiece, the cap having openings therein arranged to provide evenly-distributed charging of liquid drug.

The present invention provides an inhaler for self-administration of analgesia by a patient which may be simply manipulated, is of light weight and of low cost so that it can be disposed of after a single use. Present types of inhalers for self-administration of analgesia by the patient are generall somewhat heavy, bulky, expensive pieces of equipment. In contrast, the inhaler of the present invention is small and of light weight, thereby greatly simplifying logistic problems of storage and availability. It can easily be stocked and used in delivery rooms, emergency rooms, wards, ambulances, rescue vehicles, and it may be carried by the physician and used in the office for painful procedures or minor surgery. Repeated inhalations through the inhaler relieve pain on demand without inducing unconsciousness. With the remission of pain, the patient loses the ability to concentrate on mouth breathing and to hold the inhaler to his mouth, thus avoiding excessive drowsiness.

Briefly described, the inhaler of the present invention basically comprises a tubular body section with a mouthpiece at one end. The tubular body contains an absorbent material, such as a rolled wick, to absorb the liquid agent. In the tubular body, between the wick and the mouthpiece, are located one or more openings for dilution of inhaled drug concentration. In the end of the tubular body opposite the mouthpiece is a cap cup having openings therein for convenient charging of t'fe : liquid drug into the inhaler, the openings being arranged, together with several small ribs, to produce uniform charging of the unit and minimize the possibility of droplets of liquid drug from escaping though the mouthpiece or dilution openings during the charging.

Drawings The invention will be better understood upon consideration of the following description with reference to the drawings, in which: Figure 1 is a top perspective view of one embodiment of the invention.

Figure 2 is a side elevation view, in cross-section.

Figure 3 is a cross-sectional view, taken along the line 3-3 of Figure 2 and showing the ribs and lips of the mouthpiece.

Figure 4 is a cross-sectional view, taken along the line 4-4 of Figure 3 and showing a rolled wick within the inhale , Figure 5 is a rear elevation view taken' along the line 5-5 of Figure 2 and showing the cap.

Figure 6 is a side elevation view, in section, of the cap of Figure 5 and taken along the line 6-6 of Figure 5.

Figure 7 is a rear elevation view of the cap of Figure 5, taken along the line 7-7 of Figure 6.

Figure 8 is a graph showing the vapor concentration of drug as a function of time as produced with a mechanical ventilator connected to the mouthpiece of the inhaler.

Detailed Description: Referring to Figures 1 and 2 of the illustrative draw-ings, there is shown an inhaler 10 made in accordance with one enbodiment of the present invention and comprising a tubular portion 13 for insertion into a patient's mouth.and having an inhalation orifice 14 and an enlarged portion 15. of substantially equal diameter or cross-section as the tubular body 11. In the embodiment illustrated, the enlarged portion 15 of the mouthpiece is a slightly small diameter than the bo'dy 11 in order to provide a shoulder 16. By making the shoulder 16 of approximately 7/8 inch diameter, the mouthpiece 12 of the inhaler 10 may be inserted into a standard anesthesia mask or other standard 7/8 inch inside diameter anesthesia fitting. The mouthpiece 12 may be a unitary part of the tubular body 11 or may be formed separately and then affixed to one end of the body 11. Projecting internally from the elongated oblong portion 13 of the mouthpiece into the chamber 16 defined by the enlarged portion 15 and shoulder 16 of the mouthpiece 12 is a short continuous peripheral lip 18. The lip 18 in effect serves as a baffle and prevents droplets of liquid anesthetic or drug from entering the mouthpiece 12. Positioned between the inhalation orifice 14 and the end of the wick 19 is a first opening 20 which may be left open to permit air to enter the mouthpiece 12 to thereby dilute the concentration of inhaled vapor, or may be covered by the patient' finger to thereby increase the concentration. By positioning the diluter opening 20 proximate the mouthpiece 12 and beyond the end of the wick 19, self-administration of drug vapor becomes self-limiting. It is apparent that inhalation through the mouthpiece 12 with the diluter opening 20 uncovered will result in the inhalation of air containing a very low concentration of drug vapor. Because the opening 20 is positioned beyond the end of the wick 19 and close to the mouthpiece 12, when it is uncovered, air will be drawn through the opening 20 and directly into the mouthpiece 12 without first passing through or over the surface of the absorbent material 19 and therefore will contain very little drug vapor. Thus the opening 20 must be covered in order J somnolence occurs, the patient ' s . hand will fall away uncoveri # the opening 20. Even if breathing through the inhaler 10 is continued thereafter, air will be passing directly into the mouthpiece 12 through the opening 20 and will contain very little drug vapor so that surgical anesthesia will be avoided.

This aspect becomes particularly important when the inhaler 10 is used with a face mask (not shown). With some prior devices, which are set to deliver a specified and relatively constant drug vapor concentartion and which concentration cannot easily be reduced by the patient, unconsciousness may occur if the patient continues to inhale through the devide once drowsiness occurs. With the inhaler of the present invention, once drowsi ness occurs, the patient will lose his ability to hold the inhaler and even if it is retained in his mouth, drug vapor concen tration will decline to a relatively ineffective concentration with the opening 20 uncovered. Contained within the tubular body 11 is absorbent liquid retaining material, which in the illustrated embodiment is a rolled wick 19 of polypropylene felt which is charged with liquid drug immediately prior to use of the inhaler 10. To prevent the absorbent material from entering the mouthpiece 12 or impeding the flow of air through the dilute opening 20, one or more retaining means such as ribs 21 may be formed in the tubular body 11 extending inwardly away from the mouthpiece 12 to a point just beyond the opening 20. A second opening is positioned in the tubular body 11 to permit air to pass through or over substantially all of the absorbent liquid retaining means 19. When the first opening 20 is covered, inhaled air will pass only through the second opening and over the surface of the wick 19 thereby providing an effective con-centration of drug vapor. With the first opening 20 uncovered, most of the air will pass through the opening 20 and directly into the mouth iece 12 so that the atient will breath a rela the end of the tubular body 11 opposite from the mouthpiece 2 and having openings therein.. In addition to serving as a source of entry for air, the cap 22 serves as a retainer for the absorb ent material or wick 19 and may be used as a convenient means for charging the inhaler 10 with liquid drug. The cap 22 illustrated in Figures 5, 6, and 7 comprises a ring portion 23 having a peripheral ridge 24 extending therefrom. The outside diameter of the ring 23 of the cap 22 corresponds to the inside diameter of the tubular body 11 so that the cap 22 may be in-serted within the body 11, the ridge 24 acting as a stop to prevent the cap 22 from being inserted too far into the tubular body 11. Affixed by means of bridges 25 to the end of the ring 23 opposite the ridge 25 is a flat circular plate 26 of slightly lesser diameter than the ring 23 so that arcuate openings 27 re-suit through which the liquid drug may be charged. It can be seen that the ring 23 and plate 26 define a cap 22 which has the general configuration of a shallow cup having a small cavity 28. Extending from the bridge 25 and the plate 26 are several small ribs 29 which, when the cap is inserted into the tubular body 11, project inwardly toward the mouthpiece 12. A cap 22 having the illustrated configuration serves a number of purposes It serves as a retainer for the absorbent wick 19 and it facilitates convenient, evenly-distributed charging of the liquid drug. Thus, in charging the inhaler. 10, it is held vertically with the mouthpiece 12 down. The liquid drug is poured into the cavity 28 of the cap 22 where it flows through the arcuate openings 27 and around the small ribs 29 . Too rapid charging of the liquid drug, which might cause it to flow past the b^ sorbent wick 19 and into the mouthpiece 12 is thus minimized. If desired, instead of using a cap 22, the end of the tubular body 11 away from the mouthpiece 12 may be formed as a solid iece with an o enin therein or the end ma be solid and an may be fopned in the body 11 of the inhaler 10 through which' may be threaded a wrist tie 31 which is fastened to a patient's wrist to prevent dropping of the inhaler should the patient become drowsy or forgetful.

The tubular body 11, mouthpiece 12 and cap 22 may be injection molded in one piece or separately, from high-density polyethylene. Other suitable materials are nylon, polypropylene or acetal. The absorbent material 19 may be polypropylene felt, woven cotton, nylon felt or even absorbent paper.

Use of the inhaler 10 will be described with reference to methoxyflurane as the volatile drug. With a charge of 15 milliliters (ml.) of methoxyflurane, the inhaler 10 will deliver 0.5 to 0.87o methoxyflurane vapor for up to two hours of intermittent use. To activate the inhaler 10 for use, it is held vertically with the mouthpiece 12 down and 15 ml. of methoxy-flurane is poured into the cup-shaped cap 21. The inhaler 10 is then attached to a patient's wrist by means of the tie 31 and the patient is instructed to inhale through the inhaler 10 by mouth and exhale through the nose. A number of inhalations can be taken by the patient with the diluter orifiae 20 open in order to become accustomed to the taste of vapor. Thereafter, the patient can close the orifice 20 with a finger in order to increase the concentration of drug and obtain analgesia.

Using a mechanical ventilator, to simulate human breath ing, variation in drug vapor concentration delivered by differen inhalers 10 was found to be minimal. For the first ten minutes of use, concentrations were found to fall slightly which may be caused by equalization of saturation of the absorbent material 19. Thereafter, the output is steady until the concentration begins an exponential decline as . the liquid drug is exhausted. This is illustrated by the curves of Figure 8 which were produced with a ventilator connected to the mouthpiece of an in Vapor concentrations of methoxyflurane adequate for analgesia were produced for an hour of continuous use. In clini cal practice, with the patient laying the inhaler 10 aside frcm time to time, much longer periods of effective concentrations can be expected.

The curves were drawn from gas chromatographic, analysi data plotted against time, when inhalers of the present invention were "breathed through" by a mechanical ventilator at diffe ent respiratory rates (F) tidal Volumes Vrj , and minute vol- o umes (V). Ventilator "breathing" was continuous over the whole time scale, not intermittent as in clinical practice. With intermittent use, one 15-ml. methoxyflurane charge may be expected to last for two or more hours.

The middle curve is best taken as the "usual" or "mean performance of the inhaler at a "normal" respiratory rate of 20 breaths/minute and with a 500-ml. volume at each breath. It will be seen that effective concentration of delivered vapor rises, and duration of effect is extended, when slower respiratory rates (upper curve) are in operation. Conversely, during "hyperventilation" with a respiratory rate of 27 and a larger tidal volume (lower curve) , concentrations fall slightly and dura tion of the charge is decreased.

All three of the curves were derived from the results of tests performed with the diluter hold 20 closed. When simi-lar testing was performed on inhalers 10 with the diluter opening 20 of each left open, the height of the curves was decreased by about 50% in every case; i.e., vapor concentration with the orifice 20 open was about half that with the opening 20 covered, and duration of vaporization was prolonged.

Claims (3)

31003/2) r-t* Claims;

1. An inhaler for the self-administration of a volatile drug for analgesic purposes by a patient, the inhaler comprising a substantially tubular body, a mouthpiece projecting from one end of the body, said mouthpiece having an elongated oblong portion with an inhalation orifice for insertion into a patient' s mouth, absorbent means within the tubular body for storing the volatile drug as a liquid, a first open ng positioned in the inhaler between the inhalation orifice of the mouthpiece and the end of the absorbent means proximate to the mouthpiece* retaining means positioned internally in the inhaler on the side of the first opening away from the mouthpiece to prevent the absorbent means from obstructing the first opening or entering the mouthpiece, and a second opening positioned in the inhaler to permit air inhaled through" the mouthpiece and the second opening to pass over the absorbent means, the first and second openings being so dimensioned that, with a volatile drug stored in the absorbent means, when the first opening is covered by the finger of a patient who is Inhaling through the mouthpiece, an effective analgesic vapor concentration is provided to the patient, and when the first opening is not covered by the firjjj¾P of the patient an ineffective analgesic vapor concentration is provided to the patient.

2. , An inhaler as claimed in claim 1 including a cap located in the tubular body at the opposite end to the mouthpiece, said cap having the general configuration of a cup providing the second opening, said cap comprising: a ring portion, the outside diameter of the ring corresponding to the inside diameter of the tubular body so that the cap may. be inserted ,· 4 ring affixed to the ring by a plurality of bridges* the ring, plate and bridges defining a plurality of arcuate openings through which liquid drug can be charged into the inhaler and through which air can be inhaled to pass over the absorbent means prior to reaching the mouthpiece.

3. An Inhaler as claimed in claim 1 or claim 2 which includes a continuous lip projecting internally from the oblong portion of the mouthpiece into the tubular body to prevent passage of liquid drug into the oblong portion. . An inhaler as claimed in any one of the preceding