Method and system for the administration of a pulmonary surfactant by atomization

Abstract

A method and system according to preferred embodiments of the present invention allows optimizing the dispensing of aerosol medicaments. In particular the system according to a preferred embodiment of the present invention allows the administration of an exogenous pulmonary surfactant to very young patients (e.g. preterm neonates). A catheter 101 conveys atomized surfactant directly to the retro-pharyngeal region in order to increase efficiency of the medicament administration without being invasive: this is particularly important for very young patients, such as pre-term born neonates suffering from neonatal Respiratory Distress Syndrome (nRDS). According to a preferred embodiment of the present invention the catheter is made of biocompatible flexible material (e.g. plastic material). It is possible to couple the catheter with a rigid scaffolding (e.g. metallic) to increase stiffness of the device and to improve easiness of positioning operations. In a preferred embodiment of the present invention the delivery of the atomized medicament is done by means of an air blasting technique.

Claims

1. A system configured to deliver an atomized medicament to a spontaneously breathing pre-term neonate, the system comprising: a flexible catheter sized such that a distal end portion thereof is provided in the retro-pharyngeal region of the spontaneously breathing pre-term neonate, the flexible catheter including at least a first channel that outputs into the spontaneously breathing pre-term neonate's pharyngeal cavity a flow of liquid medicament, and at least one second channel that outputs into the spontaneously breathing pre-term neonate's pharyngeal cavity a pressurized flow of gas; a first pump connected to a first end of the first channel, that creates a low pressure which pushes a column of liquid medicament toward a second end of the first channel; a second pump connected to a first end of each said at least one second channel, that creates the pressurized flow of gas; so that when the column of liquid medicament and the pressurized flow of gas meet in the pharyngeal cavity, the column of liquid medicament is broken into a plurality of particles by the pressurized flow of gas, causing atomization of the liquid medicament and the atomized medicament to be delivered into the spontaneously breathing pre-term neonate's lungs; a controller that controls at least the first pump; and a pressure sensor, connected to the first channel, that measures a value indicative of pressure in the pharyngeal cavity of the spontaneously breathing pre-term neonate, such value being used by the controller to determine whether the spontaneously breathing pre-term neonate is in an inspiration or in an expiration phase, wherein the first pump is selectively activated by the controller only during the inspiration phase.

2. A system according to claim 1, wherein said at least one second channel includes a plurality of second channels arranged around the first channel.

3. A system according to claim 1, wherein said flexible catheter is made of flexible plastic material.

4. A system according to claim 3, wherein said flexible catheter includes a partially rigid scaffolding.

5. A system according to claim 1 wherein said flexible catheter includes a plurality of spacers arranged on an external surface thereof so that, when the flexible catheter is in place for delivering the atomized medicament, the second end of the first channel and the at least one second channel are kept separated from the wall of the pharyngeal cavity of the spontaneously breathing pre-term neonate.

6. A system according to claim 1, wherein the at least one second channel conveys pressurized air as the pressurized flow of gas.

7. A kit comprising: a medicament; the system according to claim 1; a device that positions and/or facilitates the introduction of the flexible catheter into the retro-pharyngeal region of the spontaneously breathing pre-term neonate; and a container the contains the liquid medicament, the system, and the device that positions and/or facilitates the introduction of the flexible catheter.

8. A system according to claim 1, wherein droplet size of the atomized medicament is from 80 to 200 microns in diameter.

9. A system according to claim 1, wherein the controller controls output of from 1.5 ml to 5.0 ml of liquid medicament in the column of liquid medicament per treatment session.

10. A system according to claim 1, wherein the pressure sensor is connected to the first channel, wherein the pressure sensor is external to the distal end portion of the flexible catheter that is to be provided in the retro-pharyngeal region of the spontaneously breathing pre-term neonate, and wherein the pressure sensor is arranged to indirectly measure pharyngeal pressure swings.

11. A system according to claim 1, wherein a diameter of the first channel is greater than a diameter of each said at least one second channel.

12. A system according to claim 1, wherein the distal end portion of the flexible catheter is free of a nozzle.

13. A system according to claim 1, wherein the inspiration phase is defined as starting before the beginning of inspiration and stopping before the beginning of expiration.

14. A system according to claim 1, wherein the controller predicts a future breathing pattern of the spontaneously breathing pre-term neonate for use as the inspiration phase.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

(2) FIG. 1 is a schematic diagram of the system implementing a preferred embodiment of the present invention.

(3) FIGS. 2A and 2B show an example of multi channel catheter according to an embodiment of the present invention.

(4) FIG. 3 shows as example the particles dimension of surfactant (Curosurf) atomized according to the preferred embodiment of the present invention.

(5) FIGS. 4A and 4B represent respectively a pressure sensor according to an embodiment of the present invention and the circuit controlling the pressure sensor;

(6) FIGS. 5A and 5B show an exemplificative retropharyngeal pressure signal acquired on a preterm neonate.

(7) FIG. 6 shows the steps of the method according to a preferred embodiment of the present invention.

(8) FIG. 7 shows a diagram of tidal volume related to fetuses being treated with the method and system according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(9) With the term pulmonary surfactant it is meant an exogenous pulmonary surfactant administered to the lungs that could belong to one of the following classes: (i) modified natural pulmonary surfactants which are lipid extracts of minced mammalian lung or lung lavage. These preparations have variable amounts of SP-B and SP-C proteins and, depending on the method of extraction, may contain non-pulmonary surfactant lipids, proteins or other components. Some of the modified natural pulmonary surfactants present on the market, like Survanta are spiked with synthetic components such as tripalmitin, dipalmitoylphosphatidylcholine and palmitic acid. (ii) artificial pulmonary surfactants which are simply mixtures of synthetic compounds, primarily phospholipids and other lipids that are formulated to mimic the lipid composition and behavior of natural pulmonary surfactant. They are devoid of pulmonary surfactant proteins; (iii) reconstituted pulmonary surfactants which are artificial pulmonary surfactants to which have been added pulmonary surfactant proteins/peptides isolated from animals or proteins/peptides manufactured through recombinant technology such as those described in WO 95/32992, which is incorporated herein by reference in its entirety, or synthetic pulmonary surfactant protein analogues such as those described in WO 89/06657, WO 92/22315, and WO 00/47623, all of which are incorporated herein by reference in their entireties.

(10) The term non-invasive ventilation (NIV) procedure defines a ventilation modality that supports breathing without the need for intubation.

(11) With reference to FIG. 1 an implementation of the method and system according to a preferred embodiment of the present invention is illustrated. In the example here discussed the problem of delivering the right amount of atomized medicament to a patient is addressed: in particular a pulmonary surfactant (e.g. poractant alfa, commercially available as Curosurf from Chiesi Farmaceutici SpA) is administered to e.g. a preterm neonate.

(12) However, any pulmonary surfactant currently in use, or hereafter developed for use in respiratory distress system and other pulmonary conditions could be suitable for use in the present invention. These include modified natural, artificial and reconstituted pulmonary surfactants (PS).

(13) Current modified natural pulmonary surfactants include, but are not limited to, bovine lipid pulmonary surfactant (BLES, BLES Biochemicals, Inc. London, Ont), calfactant (Infasurf, Forest Pharmaceuticals, St. Louis, Mo.), bovactant (Alveofact, Thomae, Germany), bovine pulmonary surfactant (Pulmonary surfactant TA, Tokyo Tanabe, Japan), poractant alfa (Curosurf, Chiesi Farmaceutici SpA, Parma, Italy), and beractant (Survanta, Abbott Laboratories, Inc., Abbott Park, Ill.)

(14) Examples of artificial surfactants include, but are not limited to, pumactant (Alec, Britannia Pharmaceuticals, UK), and colfosceril palmitate (Exosurf, GlaxoSmithKline, plc, Middlesex).

(15) Examples of reconstituted surfactants include, but are not limited to, lucinactant (Surfaxin, Discovery Laboratories, Inc., Warrington, Pa.) and the product having the composition disclosed in Table 2 of Example 2 of WO 2010/139442, whose teaching is incorporated herein by reference in its entirety.

(16) Preferably, the pulmonary surfactant is a modified natural surfactant or a reconstituted surfactant. More preferably the pulmonary surfactant is poractant alfa (Curosurf).

(17) The dose of the pulmonary surfactant to be administered varies with the size and age of the patient, as well as with the severity of the patient's condition. Those of skill in the relevant art will be readily able to determine these factors and to adjust the dosage accordingly.

(18) A catheter 101 conveys atomized medicament (e.g. surfactant) directly to the retro-pharyngeal region in order to increase efficiency of the medicament administration without being invasive: this is particularly important for very young patients, such as pre-term born neonate suffering from neonatal Respiratory Distress Syndrome (nRDS). According to a preferred embodiment of the present invention the catheter is made of biocompatible flexible material (e.g. plastic material). It is possible to couple the catheter with a rigid scaffolding (e.g. metallic) to increase stiffness of the device and to improve easiness of positioning operations. In a preferred embodiment of the present invention the delivery of the atomized medicament is done by means of an air blasting technique. Using air to assist atomization is a well known technique that grants a fully developed atomization also when low pressure and low flow conditions are required (see e.g. Arthur Lefebvre, Atomization and spray, Taylor and Francis, 1989, which is incorporated herein by reference in its entirety). Such technique is based on a relatively small amount of gas (e.g. air, but it could be other compressed gas, e.g. oxygen, nitrogen, or helium) which flows in one or more separate channels than the medicament which is delivered in a liquid form; the air flow accelerates and breaks the liquid column, inducing the atomization of the medicament. Therefore the catheter 101 includes a plurality of channels (at least two, one for the medicament and one for the air) for conveying contemporarily the medicament and the air flow. The liquid medicament column is broken up in droplets by the turbulence due to the air flowing next or around when the two flows (air and liquid medicament) exit the catheter channels and meet in the retro-pharyngeal region. The atomized droplets have a mean diameter of at least 80 microns, preferably higher than 100 microns, more preferably of 80 to 150 microns. It is believed that this effect is caused by the air flow which accelerates the fluid sheet instability. The air also helps in dispersing the droplets, preventing collision among them and facilitating the diffusion of the medicament in the lungs by reducing the likelihood of contact between the particles and the wall of the retropharyngeal cavity.

(19) In a preferred embodiment of the present invention the medicament (e.g. the surfactant) is supplied by means of a pump 103 connected to one end of the catheter, which forces the liquid medicament out of the opposite end of the catheter where it meets the air flow (conveyed by a different channel of the catheter) and is atomized, i.e. broken into a plurality of small particles (droplets) by the pressurized air. Pump 103 may be realized by a device able to generate a flow, such as an infusion pump: in a preferred embodiment of the present invention the pump 103 is made of a mechanical frame comprising a structure that holds a syringe containing the liquid medicament and a stepper motor that pushes the syringe piston. In an embodiment of the present invention, pump 103 can be controlled by a control unit 109; such control unit can be embodied in a computer, a microprocessor or, more generally any device capable of data processing activity. A pump device 105 (possibly including a pressurized source and pressure regulator and filter) is connected to the one or more channel conveying the air flow. Those skilled in the art will appreciate that the term pump includes any device capable of providing a pressure to either a liquid flow or a flow of gas. Pump 105 can be controlled by a control unit, as described for the pump 103. The flow of the pump 103 should be in the range of 9 to 18 ml/H while the pressure of the pump 105 should be comprised between 0.4 and 0.8 Atm (1 Atm=1.01325 Bar).

(20) In a preferred embodiment of the present disclosure the catheter 101 includes multiple channels, with a main (e.g. central) channel conveying the surfactant, being surrounded by a plurality of additional channels (e.g. lateral) which convey a pressurized air flow). The air blasting technique here described provides the advantage of a more gentle fragmentation of the surfactant. Current atomizers for drug delivery are normally based on plain orifices, while the method according to the present disclosure employs an atomizing catheter using the air blasting approach. The geometrical configuration of the plain orifice normally presents a narrowing at the tip of the catheter, the nozzle, which accelerates the liquid producing an high instability in presence of an high pressure drop (more than 1 Atm) and, as a consequence, the fragmentation of the liquid in particles. On the contrary, the air blasting catheter according to a preferred embodiment of the present disclosure is a multi-lumen catheter: the surfactant flows into the main lumen while pressurized air flows in the lateral ones. The turbulences generated by the small airflow fragment the surfactant in a very gentle way. Moreover, the use of plain orifices would require very high differential pressure across the nozzle to induce atomization, while the air blasting atomizer doesn't need high driving pressure to the surfactant, as the atomizing process is driven by the turbulence of the air around the surfactant.

(21) The pulmonary surfactant is preferably administered as a suspension in a sterile pharmaceutically acceptable aqueous medium, preferably in a buffered physiological saline (0.9% w/v sodium chloride) aqueous solution.

(22) Its concentration shall be properly adjusted by the skilled person in the art.

(23) Advantageously, the concentration of the surfactant is 2 to 160 mg/ml, preferably 10 to 100 mg/ml, more preferably 40 to 80 mg/ml.

(24) The applied volume should generally be not more than 5.0 ml, preferably not more than 3.0 ml. In some embodiments, it could be 1.5 ml or 3 ml.

(25) A possible additional feature of the method and system according to the present invention is that of synchronizing the pulmonary surfactant administration with the breathing phase of the patient. To implement this feature, a pressure sensor 107 is inserted along the surfactant catheter, but externally to the pharyngeal tube, and provides an indirect but accurate measurement of the pharyngeal pressure swings. This measurement is possible because of the relatively low pressure in the channel conveying the surfactant, allowing the use of the surfactant line for measuring the retro-pharyngeal pressure with the aim of both synchronizing the atomization with the breathing pattern of the patients and to help the attending medical staff to place the catheter in the proper place and monitoring the maintenance of the proper position during the treatment, allowing the identification of wrong positioning of the catheter tip (e.g. into the oesophagus).

(26) FIG. 2 shows a specific implementation of the multi-channel catheter according to a preferred embodiment of the present invention. The air blasting atomizer of the present embodiment is realized by means of a multi-lumen catheter with a central inner lumen 201 surrounded by several smaller lumens 203. The surfactant flows into the main central lumen, driven by the infusion pump, while the gas (e.g. air, oxygen-enriched air or pure oxygen), flows through the lateral lumens. The pressure drop in the central catheter depends on its length and internal diameter. In a preferred embodiment of the present disclosure the catheter could present a length of 7 to 15 cm and an internal diameter of 0.4 to 0.6 mm. In this case the pressure drop is in the range of 7.8 to 0.72 cmH.sub.2O, considering a flow of surfactant of 3 mL/20 min. In this way a nozzle is not required and the particles size dimension is determined mainly by the pressure of the air which flows in the lateral channel. To generate the gas flow into the lateral lumens a compressor or a pressurized gas source (e.g. a cylinder or a medical gas wall plug) can be used: the pressure is modulated by a pressure regulator with a mechanical filter to avoid dust flowing through the system.

(27) Such pressurized gas flow is not able to significantly alter the pressure in the pharynx, since the flow is rather limited and the anatomical structures are open to the atmosphere.

(28) The distribution of the particles size obtained by means of the preferred embodiment of the present invention has been characterized by a commercial laser diffractive size analyzer (Malvern, Insitec RT). The measurements have been carried out using exemplificative conditions of 0.5 bar of pressurized air and a surfactant flow rate of 3 mL/20 minutes.

(29) As a result, the most of the particles size is comprised between 100 to 200 microns. In particular the median value is 137.47 micron, the 10.sup.th percentile is 39.50 micron, the 90.sup.th percentile is 130.63 micron as reported in FIG. 3.

(30) In one embodiment, the catheter contains a single channel or lumen for the surfactant having an inner diameter of about 0.25 mm, surrounded by 12 channels or lumen for air each having an inner diameter of about 0.12 mm, which leads to a ratio of the area of the surfactant channel to the total area of the air channels of about 0.4. Of course, other diameters may be used. For example, in another embodiment, the surfactant channel may have an inner diameter of about 0.2 mm to about 0.6 mm and the air channels may have inner diameters of about 0.05 mm to about 0.15 mm. In particular, the surfactant channel may have an inner diameter of about 0.5 mm and the air channels may have inner diameters of about 0.12 mm, which leads to a ratio of the area of the surfactant channel to the total area of the air channels of about 1.4. Of course, the catheter itself will have an outer diameter large enough to accommodate the surfactant and air channels.

(31) As a possible additional feature, the catheter used in the method and system of the present invention could be provided with some spacers on the external surface which help in positioning it and keeping a minimum distance between the catheter itself and the wall of the retro-pharyngeal cavity. This separation ensures that the atomised surfactant is conveyed to the lung by inspiratory airflow and not projected on the walls of the pharyngeal cavity. An example is shown in FIG. 2b where some ribs are running along the external surface of the catheter; these ribs can also have a stiffening function adding some sort of rigidity to the catheter (as an alternative to the metal scaffolding mentioned above). Other shapes of the ribs are possible, e.g. they could be in the shape of one or more rings surrounding the catheter at predetermined distance one each other: those skilled in the art will appreciate that several equivalent alternatives can be implemented.

(32) Laryngoscope is another tool known to the skilled person, that could be suitably utilized for positioning the catheter in the retro-pharyngeal cavity.

(33) Moreover, Magill forceps, oro-pharyngeal cannulas such as cannula of Mayo, of Guedel, of Safar and of Bierman can facilitate the introduction of the catheter. In a preferred embodiment the cannula of Mayo is utilized for both facilitating the introduction and keeping the catheter tip in the proper position, i.e. not close to the pharyngeal wall and pointing toward the inlet of the trachea during the whole period of surfactant delivery.

(34) FIG. 4a shows a possible implementation of the pressure sensor 107 mentioned above, which is used in an embodiment of the present invention to detect the pressure of the air coming from or flowing into the pharyngeal cavity. Such measured pressure is used as an indication of the breathing rhythm of the patient and the system synchronizes the administration of the medicament accordingly. This synchronization brings big advantages both in term of efficacy of the treatment and in reducing the waste of medicament. The efficacy is due to the transportation of the atomized drug by the inspiratory flow; the saving is caused by the fact that the medicament is delivered only when needed, avoiding to waste it while the patient is exhaling. In an embodiment of the present disclosure the pressure sensor is inserted along the surfactant line and transduces the pressure from the tip of the catheter (i.e. the pressure in the neonate pharynx) to the sensing element which acts as a variable resistance. When the motor is activated the syringe gently pushes the surfactant into the atomizing catheter to allow an averaged flow of 3 ml/h (this parameter can be adjusted on the treatment program). As shown in FIG. 4b, the sensor exploits the piezoresistive phenomenon to convert the mechanical pressure into a voltage drop; it has an internal Wheatstone Bridge connection, which means that it is internally compensated for ambient temperature fluctuations.

(35) The sensor can be for example a disposable pressure sensor, similar to those used for the invasive measurement of blood pressure.

(36) The administration of surfactant only during the inspiration phase is a big advantage provided by the present invention: this results in a better control on the effective quantity which reaches alveoli and to avoid the waste of the supplied surfactant. This requires the measurement of a signal related to the breathing pattern in the ventilatory condition of the preterm neonate (spontaneously breathing and kept under nCPAP or other non-invasive ventilation procedure such as NIPPV) to detect the end-inspiration and end-expiration and to predict the future breathing pattern of the baby. According to an embodiment of the present invention, the administration of surfactant is started before the beginning of the inspiration and stopped before the beginning of the expiration in order to: 1) take into account the mechanical delays in the atomization; 2) prevent the loss of surfactant since the surfactant delivered at end inspiration will be still in the pharyngeal cavity and therefore exhaled during the beginning of the expiration.

(37) In FIG. 5 are reported retropharyngeal pressure tracings from a representative preterm baby with gestational age of 28 weeks and a body weight of 1650 g. Panel a shows the whole track characterized by a very high variability with several spikes and base line fluctuations; in panel b an enlargement of the same signal is reported. A statistical analysis on the data has been performed and a predictive algorithm has been designed. The main steps of which are reported in the flow chart of FIG. 6, with the relative functions. In particular, after the removal of trends and high frequency noise, the signal is integrated to obtain a new signal proportional to the lung volume, and by looking for maxima and minima it is possible to detect the end-inspiratory and end-expiratory points. Our statistical analysis includes also the measurement of the pressure involved, which is about 1 cmH.sub.2O in all the different conditions.

(38) By using this approach we have obtained in an exemplificative simulation, the administration of the 970.8% of surfactant in 6021 minutes in 7 preterm neonates with a gestational age of 29.53 weeks and a body weight of 1614 g (424 g).

(39) All operations of the system here described are controlled by a microprocessor (e.g. microcontroller of PIC18F family by Microchip Technology Inc.) running a software adapted to implement the method according to a preferred embodiment of the present invention.

(40) It will be appreciated that alterations and modifications may be made to the above without departing from the scope of the invention. Naturally, in order to satisfy local and specific requirements, a person skilled in the art may apply to the solution described above many modifications and alterations. Particularly, although the present invention has been described with a deep degree of particularity with reference to preferred embodiment(s) thereof, it should be understood that eventual omissions, substitutions and changes in the form and details as well as other embodiments are possible; moreover, it is expressly intended that specific elements and/or method steps described in connection with any disclosed embodiment of the disclosure may be incorporated in any other embodiment as a general matter of design choice.

(41) For example, similar considerations apply if the components (e.g. microprocessor or computers) have different structure or include equivalent units; in any case, it is possible to replace the computers with any code execution entity (such as a PDA, a mobile phone, and the like).

(42) Similar considerations apply if the program (which may be used to implement some embodiments of the disclosure) is structured in a different way, or if additional modules or functions are provided; likewise, the memory structures may be of other types, or may be replaced with equivalent entities (not necessarily consisting of physical storage media). Moreover, the proposed solution lends itself to be implemented with an equivalent method (having similar or additional steps, even in a different order). In any case, the program may take any form suitable to be used by or in connection with any data processing system, such as external or resident software, firmware, or microcode (either in object code or in source code). Moreover, the program may be provided on any computer-usable medium; the medium can be any element suitable to contain, store, communicate, propagate, or transfer the program. Examples of such medium are fixed disks (where the program can be pre-loaded), removable disks, tapes, cards, wires, fibres, wireless connections, networks, broadcast waves, and the like; for example, the medium may be of the electronic, magnetic, optical, electromagnetic, infrared, or semiconductor type.

(43) In any case, the solution according to the present invention lends itself to be carried out with a hardware structure (for example, integrated in a chip of semiconductor material), or with a combination of software and hardware. The system of the invention is particularly suitable for the prevention and/or treatment of the respiratory distress syndrome (RDS) of the neonate (nRDS). However, it could be advantageously utilized for the prevention and/or treatment of adult/acute RDS (ARDS) related to a surfactant-deficiency or dysfunction as well as of conditions in which respiratory distress may be present as a consequence of, for instance, meconium aspiration syndrome, pulmonary infection (e.g. pneumonia), direct lung injury and bronchopulmonary dysplasia.

(44) Advantageously, the system of the invention is applied to pre-term neonates who are spontaneously breathing, and preferably to extremely low birth weight (ELBW), very-low-birth-weight (VLBW), and low-birth weight (LBW) neonates of 24 to 35 weeks gestational age, showing early signs of respiratory distress syndrome as indicated either by clinical signs and/or supplemental oxygen demand (fraction of inspired oxygen (FiO.sub.2)>30%).

(45) More advantageously, nasal Continuous Positive Airway Pressure (nCPAP) is applied to said neonates, according to procedures known to the person skilled in the art.

(46) Preferably a nasal mask or nasal prongs are utilized. Any nasal mask commercially available may be used, for example those provided by The CPAP Store LLC, and the CPAP Company.

(47) Nasal CPAP is typically applied at a pressure between 1 and 12 cm water, preferably 2 to 8 cm water, although the pressure can vary depending on the neonate age and the pulmonary condition.

(48) Other non-invasive ventilation procedures such as nasal intermittent positive-pressure ventilation (NIPPV), High Flow Nasal Cannula (HFNC), and bi-level positive airway pressure (BiPAP) can alternatively be applied to the neonates.

(49) Other features of the invention will become apparent in the course of the following descriptions of exemplary embodiments which are given for illustration of the invention and are not intended to be limiting thereof.

EXAMPLES

(50) In vivo efficacy of atomized surfactant (in this example poractant alfa, as defined above) was evaluated in preterm newborn rabbits at the 27th day of gestation (term=311 days). The model chosen closely resembles the conditions of premature babies affected by RDS in that the lungs of these animals are not yet able to produce their own surfactant, but can warrant gas exchange so that they can expand in response to exogenous surfactant administration.

(51) Treatments were intratracheally given at 2 ml/kg volume, corresponding to 160 mg/kg dose. Foetuses, paralyzed with pancuronium bromide (0.02 mg i.p.), were then placed in the plethysmograph system at 37 C. and ventilated with pure oxygen at constant pressure (frequency 40/minute, inspiration/expiration ratio 60/40). No positive end-expiratory pressure (PEEP) was applied. An opening pressure of 35 cmH.sub.2O was first applied for 1 minute to overcome initial resistance due to capillarity in finer conducting airways. It was then followed by 15 minutes at 25 cmH.sub.2O, 5 minutes at 20 cmH.sub.2O, 5 minutes at 15 cmH.sub.2O and again at 25 cmH.sub.2O for the final 5 minutes.

(52) Respiratory flow was measured every 5 minutes by a Fleish tube connected to each chamber of the plethysmograph system. Tidal volume (Vt) was automatically obtained by integration of the flow curve.

(53) Two sets of experiments were performed.

(54) In the first set, five samples (1 ml each) have been received. The pulmonary surfactant administered at each samples is respectively: not atomized poractant alfa, poractant alfa atomized at an air pressure of 0.0, 0.2, 0.5, and 0.8 bar. The pulmonary surfactant has been atomized using the preferred embodiment of the present invention.

(55) In this set of experiments a control group without any treatment was included.

(56) All the atomized samples, including that passed through without any pressure applied, resulted as effective as not atomized poractant alfa (P<0.05, one-way ANOVA followed by Tukey's test; Graphpad Prism). No statistically significant difference was found between the different conditions of atomization.

(57) In the second set, three samples (1 ml each) have been received. The pulmonary surfactant administered at each samples is respectively: non-atomized poractant alfa, poractant alfa atomized at an air pressure of 0.2, 0.5, and 0.8 bar.

(58) In this set of experiments two further groups were included, a control group without any treatment and a group treated with a batch of poractant alfa already released to the market.

(59) The same results were observed in the second set of experiments.

(60) As the results were consistent in the two sets, the data have been pooled (FIG. 7). Statistical analysis of these data confirmed the previous results.

(61) In conclusion the passage through the atomizer, using the preferred embodiment of this invention, does not affect poractant alfa efficacy in premature rabbit foetuses. In particular, atomization at pressures between 0.2 and 0.8 bar does not significantly affect poractant alfa efficacy and the application of 0.5 bar seems the most suitable although no statistically significant difference has been observed between different atomization conditions.

(62) Where a numerical limit or range is stated herein, the endpoints are included. Also, all values and subranges within a numerical limit or range are specifically included as if explicitly written out.

(63) As used herein the words a and an and the like carry the meaning of one or more.

(64) Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

(65) All patents and other references mentioned above are incorporated in full herein by this reference, the same as if set forth at length.