Endotracheal Tubes with Pulmonary Medicaments

Background of the Invention

This invention relates to the administration of medicaments to the lungs and, in particular, provides a device for administration of a pulmonary medicament, such as a lung surfactant.

Various systems exist for administration of medicaments to the lungs, for example, in the case of asthma conditions, it is conventional practice to administer the medicament in a nebuliser. However, in the case of patients who are unable to participate actively in the treatment, such as new born babies, the medicament may be given by means of a syringe through a catheter, directly into the respiratory tract. One difficulty with patients who are being ventilated is that in order to administer the medicament, the patient has to be disconnected from the ventilator while the medicament is administered, and this is a potentially dangerous step in the case of critically ill patients.

It has become the practice in the case of babies who experience breathing difficulties, to administer medicaments, commonly known as lung surfactants, to alleviate respiratory distress syndrome. One artificial surfactant which has been successfully used is sold under the trade name "ALEC" and is a dry protein-free powder which is a mixture of dipalmitoylphosphatidylcholine (DPPC) and phosphatidylglycerol (PG) in the molar ratio of 7:3 of DPPC to PG. This phospholipid mixture has a melting point in water in the region of body temperature. It acts by forming a mono layer on the surface ofthe alveolae and reducing the surface tension ofthe air/water interface by a factor of about two- thirds. This facilitates the extension of the baby's air-water interface, by

reducing the work required to extend the effective area of the lungs. At blood temperature and as a consequence of repeated compression and relaxation, the DPPC component in the mixture becomes progressively enriched to the point that it condenses out of the mixture as a solid phase which is rigid enough to help prevent the lung alveoli from collapsing (anti-oedema effect).

Although the above medicaments have proved to be exceptionally effective when properly placed, one difficulty has been in applying the medicament quickly enough and in minimising the time when the subject is not connected to the ventilator.

An object ofthe present invention is to overcome these difficulties and to provide more effective methods and apparatus for administering lung surfactants and other pulmonary medicaments.

Summary of the Invention

According to one aspect of the present invention, there is provided a device for administering a pulmonary medicament directly to the lungs which comprises an elongate flexible member adapted for introduction into the trachea, said member supporting a pulmonary medicament.

Detailed Description of the Invention

The elongate member may take the form of a tube, rod, wick or mop carrying or supporting the medicament. The elongate member should be sufficiently flexible to be capable of being introduced either directly into the trachea or through an endotracheal tube.

The pulmonary medicament is generally a solid material, preferably one which has been deposited from suspension or solution. For example, the elongate member may be dipped into a suspension or concentrated solution of

the medicament, removed from the solution or suspension and then dried to deposit the medicament on the surface or surfaces of the member, e.g. on the distal end.

In a preferred form of the mvention, the medicament is deposited on surfaces of an endotracheal tube which is connectable to a ventilator. Thus, in the case of a breathless infant, the attending physician can immediately intubate the patient with an endotracheal tube carrying lung surfactant. In this way, the lung surfactant is administered directly into the respiratory tract of the infant. The endotracheal tube is used for ventilating the infant.

The method and apparatus ofthe present mvention is particularly suitable for administration of a lung surfactant to both neonatal infants, children and adults experiencing respiratory distress. The preferred lung surfactant is available under the trade mark "ALEC" and its composition and use is described in the paper by Bangham et al in Colloids & Surfaces 10, (1984), pages 337 to 341, and in the paper entitled "Ten Centre Trial of Artificial Surfactant in Very Premature Babies", British Medical Journal, 18th April 1987, vol. 294, pages 991 to 996. 'ALEC lung surfactant is marketed by Britannia Pharmaceuticals Limited, Forum House, Brighton Road, Redhill, Surrey, England. Other commercially available lung surfactants may be administered in accordance with this invention. Examples are available under the trade names "Exosurf, "Curosurf', "Survanta", "Infasurf, "Bles", KL4", "Alveofact" and "Surfactant TA".

In the case of the lung surfactant described above and sold under the trade mark 'ALEC, an amount of approximately 2 mg is theoretically sufficient to facilitate the rapid extension of the child's lungs. However, there is no real

disadvantage in administering a large excess of the lung surfactant since it is an essentially natural product. In practice, therefore, a sufficient amount or excess may be applied to the surfaces of the endotracheal tube, depending upon whether infants, children or adults are to be treated. Typically, the amount may be from about 2 to 20 mg

Brief Description of the Drawings

Figure 1 is a side elevation of an endotracheal tube in accordance with the invention; and

Figure 2 is a diagrammatic view illustrating a method of employing the endotracheal tube.

Referring to the drawings, Figure 1 shows an endotracheal tube comprising a plastics tube (1), e.g. about 3.0—4.0 mms diameter, for introducing into the infants' nasal or oral passage. One end (2) ofthe plastic tube (the distal end) carries an external and/or internal coating (3) of a lung surfactant which has been deposited onto the surface(s) ofthe tube. The lung surfactant coating may conveniently extend over the distal 5 to 15 mms, e.g. 10 mms, of the tube. At the opposite end ofthe tube (1 ), a connector (4) is attached to the tube, e.g. by a frictional fit or by heat or solvent welding.

Figure 2 shows diagrammatically, the method of using the endotracheal tube. The distal end (2) of the tube is introduced through the nose or mouth and the connector (4) is attached to a resuscitation bag or ventilator (5). With the tube in place, the infant is intubated until he is able to breathe unaided. It will be appreciated that the endotracheal tube of the mvention enables the patient, e.g. a premature neonate, to be intubated while simultaneously adnrinistering a pulmonary surfactant.

The surfactant is conveniently deposited on the tube from a solvent solution and any medically acceptable solvent which can be easily volatilised may be used. In the case of the lung surfactant referred to above, chloroform or ethanol/ethyl ether mixtures (e.g. ethanol/ether in a 1 :1 mixture) are examples of suitable solvents. The resulting concentrated solution may be filtered through a bacterial filter prior to apphcation to the tube, e.g. by dipping. After dipping the tube in the concentrated solution ofthe medicament, the tube may be dried, e.g. in a stream of hot sterile air or vacuum dried, to remove the solvent at a temperature which does not harm the active material. In the case of lung surfactant containing protein, this should be at a temperature below about 45°C since protein tends to be degraded at higher temperatures.

In the case of lung surfactants of the kind referred to above, the material dries to form a smear having a consistency similar to that of dry, hard soap (a Coagel). This smear has the additional advantage of acting as a lubricant for the introduction ofthe tube into the respiratory passage ofthe patient.

Although not so convenient, it is possible to apply the pulmonary medicament to an impregnated mop, wick or rod which can then be passed through an endotracheal tube, thereby replenishing the inner surface of the endotracheal tube. Such a technique may require only a short period of interruption ofthe ventilation of the patient, particularly if the endotracheal tube is suitably adapted to receive a catheter, mop or other elongate member without disconnection ofthe ventilator.

While the invention has been described with particular reference to its use for administration of lung surfactants to infants, it would also be applicable

to cases of acute drowning, pneumonia, pulmonary oedema, and adult respiratory distress (ARDS).

It is possible to use the method and apparatus of this invention for veterinary purposes, for example, neonatal horses and pigs sometimes suffer from breathing difficulties due to deficiency of lung surfactant. The endotracheal tube or other elongate flexible applicator would, of course, need to be considerably longer and, in the case of an endotracheal tube of larger bore, but the technique is essentially similar.