Abstract:
A compact, portable transport system enables the application of high-frequency ventilation and inhaled nitric oxide therapy while providing real-time monitoring of the physiological state of the patient. The system includes a patient transport carrier having a patient chamber and an oxygen supply unit, as well as a high-frequency ventilator and a physiologic monitor. An inhaled nitric oxide delivery unit can also be included in the transport system. The nitric oxide system permits the reduction of pulmonary arterial blood pressure, with consequent improvement of patient oxygenation and reduced mortality and morbidity.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to patient transport and mechanical ventilation systems, and especially to a portable, high-frequency ventilation system.  
           [0003]    2. Description of the Related Art  
           [0004]    Patients, especially neonates born prematurely, may experience respiratory failure as a result of a number of conditions. These include, among others, respiratory distress syndrome (RDS) due to fetal lung immaturity and consequent lack of surfactant; persistent pulmonary hypertension of the newborn; meconium aspiration syndrome; pulmonary interstitial emphysema; pneumothorax, including tension pneumothorax; pulmonary hypoplasia; congenital diaphragmatic hernia; bronchopulmonary or tracheo-esophageal fistulas; severe pneumonia; and septic shock. Such patients commonly experience severe hypoxemia, which may be caused by such physiologic factors as arteriovenous shunting or ventilation/perfusion (V/Q) mismatching. Such conditions are frequently acute and, unless the patient receives effective treatment within a short period of time, are likely to rapidly worsen, frequently resulting in the death of the patient.  
           [0005]    Various strategies have been employed for the treatment of these conditions. These include, among others, conventional mechanical ventilation or intermittent mandatory ventilation, extracorporeal membrane oxygenation, high-frequency ventilation, and the inhalation of pulmonary vasodilators, such as nitric oxide (NO).  
           [0006]    Conventional mechanical ventilation has proven to be a less than satisfactory treatment for these illnesses for a number of reasons. Because of the large intra-airway pressures required to oxygenate the patient adequately, there is a great risk of lung damage as a result of barotrauma when conventional ventilation is employed for pediatric patients. Additionally, when infants are maintained at a fraction of inspired O 2  (FIO 2 ) of 100% at typical high ventilation airway pressures for longer than 24 hours, blindness may result due to retrolental fibroplasia (RLF). Furthermore, the conventional ventilation of such patients is associated with a high rate of granulocyte-related lung injury, as well as the development of air leak syndrome, hyaline membrane disease, and alveolar proteinaceous edema.  
           [0007]    Extracorporeal membrane oxygenation has also been employed in treating instances of neonatal respiratory failure. This method requires the presence of an external membrane oxygenator, and its use is generally restricted to well-equipped intensive care units. Although effective, it is often difficult to wean patients from this type of ventilation even after the time for pulmonary recovery has elapsed. It is not a therapy that is well suited to the emergency treatment of pediatric patients experiencing respiratory failure who are located in a facility lacking an intensive care unit.  
           [0008]    A third ventilation option is provided by high-frequency ventilation, which is a type of mechanical ventilation. High-frequency ventilation typically employs much lower tidal volumes and a much higher rate of respiration; typically, frequencies of greater than 10 breaths per second are used. High-frequency ventilation represents an improvement over conventional mechanical ventilation in cases of respiratory failure for a number of reasons. Among these are a reduced risk of barotrauma (i.e., pneumothorax, pneumoperitoneum, pneumomediastinum, and subcutaneous emphysema), improved ventilation/perfusion (V/Q) matching, and a lower rate of systemic hypotension. However, the equipment necessary to carry out high-frequency ventilation has hitherto been available only in well-equipped intensive care units. As a result, high-frequency ventilation techniques could not be utilized in patients at remote locations, nor during the transport from such locations to a hospital facility having an intensive care unit equipped to perform high-frequency ventilation.  
           [0009]    A fourth method of treatment for these respiratory conditions employs pulmonary arterial vasodilators, such as inhaled nitric oxide (NO). Extensive investigations of the use of nitric oxide as a method of treatment for hypoxemia have been performed. The administration of inhaled nitric oxide induces, in many patients, an improvement in V/Q matching, and it has been postulated that nitric oxide may have benefits unrelated to improved V/Q matching, including anti-inflammatory properties, anti-platelet activity, and effects which diminish vascular permeability. Nitric oxide may be used with conventional mechanical ventilation, but its use has been shown to be particularly effective when combined with high-frequency ventilation; for example, such results were reported by Kinsella, et al., in  J. Pediatrics  1995; 126:853-864. As is the case with high-frequency ventilation, however, inhaled nitric oxide therapy is generally available only at hospitals that offer specialized care for critically ill infants. Thus, for children, the most effective therapies for acute respiratory failure have been available almost exclusively in pediatric intensive care units.  
           [0010]    However, by their very nature these ailments are often acute and may strike when a child is many miles from a suitably equipped intensive care unit. In addition, the most effective therapies, such as high-frequency ventilation and nitric oxide therapy, are of relatively recent origin. Although they are well-known in academic teaching hospitals, these therapies frequently are not available in the clinics and regional hospitals to which such pediatric patients are often first brought. Typically, the staff of such local facilities is not trained in the use of these techniques, and even if the equipment becomes available, the technological learning curve thereof is quite steep. Therefore, it is desirable, and often mandatory, to transfer such patients to a facility in which these therapies are available and to provide these patients with the optimal therapy as soon as possible.  
           [0011]    As noted above, the use of such therapies while transporting a patient to a suitably equipped intensive care unit has hitherto been impossible. The necessary equipment is in the form of separate units, such as a stand-alone high-frequency ventilator, separate inhaled nitric oxide system, and the like, and is extremely bulky. Such equipment would be used in addition to the standard equipment necessary for monitoring and maintaining care to a patient during transport. Therefore, not only would it be quite burdensome to move each piece of equipment along with the patient during transport, due to the limited amount of space in a helicopter or ambulance for transporting the patient, the many pieces of equipment are not likely to fit into the transport vehicle.  
         SUMMARY OF THE INVENTION  
         [0012]    The inventors recognized the need for a way to, in effect, bring the intensive care unit to the patient in the field. Rather than waiting for the arrival of the patient at a well-equipped intensive care unit to begin optimal therapy, it is much more desirable that the patient begin physiological monitoring, high-frequency ventilation, and, in some cases, inhaled nitric oxide therapy immediately and continue this therapy while en route to an intensive care unit. This therapy provides better oxygenation for the critically ill patient, thereby reducing morbidity and improving survival.  
           [0013]    An integrated transport unit in accordance with the present invention permits this type of therapy for children during transport. A compact, portable transport system enables the application of high-frequency ventilation and inhaled nitric oxide therapy, while providing sophisticated monitoring of the physiological state of the patient, such as the assessment of blood oxygen saturation. In one embodiment of the present invention, the transport system incorporates commercially available component units, which are assembled to produce an infant or pediatric transport system equipped with a monitoring system and a high-frequency ventilator. Additionally, the system may incorporate an inhaled nitric oxide system.  
           [0014]    Further features and advantages of the present invention will become apparent to one of skill in the art in view of the Detailed Description that follows, when considered together with the attached drawings and claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is an oblique front view of a ventilation transport system in accordance with the invention.  
         [0016]    [0016]FIG. 2 is an exploded front view of the ventilation transport system shown in FIG. 1.  
         [0017]    [0017]FIG. 3 is an exploded side view of the ventilation transport system shown in FIG. 1.  
         [0018]    [0018]FIG. 4 is a side cross-sectional view of a ventilation Y tube in an open state.  
         [0019]    [0019]FIG. 5 is a side cross-sectional view of the ventilation Y tube in a closed state.  
         [0020]    [0020]FIG. 6 is a front view of a portable pediatric ventilation transport system in accordance with another embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0021]    While the ventilation transport system of the present invention is described herein primarily with respect to pediatric patients, the system can be equally well-suited for use in the adult population. Currently, however, children constitute the most studied group that has been shown to benefit from nitric oxide administration during mechanical ventilation for respiratory failure.  
         [0022]    [0022]FIGS. 1 through 3 illustrate a ventilation transport system  100  of the present invention adapted for the transport of infants or small children. FIG. 1 shows an oblique schematic view of the portable ventilation transport system of the present embodiment. FIG. 2 is an exploded frontal view of the ventilation transport system and FIG. 3 is an exploded side view of the portable ventilation transport system of the present embodiment. The ventilation transport system  100  includes a mechanical or high-frequency ventilator  200  installed in a main body  130 , a physiological monitor  400  attached to the main body  130 , and an inhaled nitric oxide delivery system  300 , also attached to the main body  130 . The physiological monitor  400  and the inhaled nitric oxide delivery system  300  are attached to the main body  130  by brackets. The transport main body  130  includes a respiratory alcove  135  and a ventilator alcove  137 . The respiratory alcove  135  serves to store supplies used in treating patients during transport. The ventilator alcove  137  houses the ventilator  200 . Commercially available unit components are assembled to form the remainder of the transport system of the first embodiment. In the illustrated infant ventilation transport system  100 , these are an oxygen supply chamber  110 , an accessory module  120 , a transport main body  130 , and a patient chamber  140 . The accessory module  120  is used with other modifications such as further monitors, sensors, intensive care devices, and the like. These component units will be described in greater detail hereinbelow.  
         [0023]    In the case of treating babies with respiratory failure, the mechanical ventilator  200  is preferably a high-frequency ventilator, and more preferably a high-frequency ventilator which is capable of conducting at least one of the following ventilatory modes: positive pressure high-frequency ventilation, high-frequency jet ventilation, and high-frequency oscillatory ventilation. As shown in FIG. 2, the ventilator  200  is located within the ventilator alcove  137  of the transport main body  130 . In one embodiment, the ventilator  200  is a “PERCUSSION AIR DUOTRON” high-frequency ventilator. Alternatively, a “VDR®-3C Universal Logistical Percussionator®” produced by the Percussionaire® Corporation (Sandpoint, Ind.) can be used as the high frequency ventilator  200 . These are, however, simply examples, and the skilled artisan will readily appreciate that other ventilation devices may be employed without thereby departing from the spirit and scope of the present invention.  
         [0024]    In order to provide the benefits of inhaled nitric oxide therapy, the pediatric ventilation transport system  100  further includes a nitric oxide delivery system  300 . This nitric oxide delivery system  300  is secured to the transport main body  130  by a bracket  132 , which may be provided on the transport main body  130 . This nitric oxide delivery system  300  is preferably capable of delivering therapeutic doses of inhaled nitric oxide, and advantageously permits monitoring of NO and NO 2  levels in the patient. This monitoring may advantageously employ a mass flow meter. The “AeroNOx Portable System” produced by Pulmonox Medical Corporation (Alberta, Canada) is one example of a nitric oxide delivery system  300  which may be used in the ventilation transport system  100 . This is only an example, however, and the skilled artisan will readily appreciate that other nitric oxide systems may be employed without thereby departing from the spirit and scope of the present invention.  
         [0025]    In the illustrated embodiment, the nitric oxide delivery system  300  is attached to the main body  130  by brackets. In other embodiments, however, the nitric oxide delivery system can be integral with the ventilation transport system  100 .  
         [0026]    As described above, the nitric oxide delivery system  300  of the present embodiment is capable of monitoring NO and NO 2  levels. The nitric oxide delivery system  300  may employ either a chemiluminescence or an electrochemical detection method. Using the “AeroNOx Portable System” described above, the present inventors have experimentally determined that the electrochemical method exhibits negligible differences from the chemiluminescence method, although the latter is considered the “gold standard” in the industry. Thus, either the chemiluminescence or the electrochemical detection method for NO and NO 2  gases may be employed in the ventilation transport system  100 .  
         [0027]    [0027]FIGS. 4 and 5 illustrate a ventilation tube  220  of the ventilation transport system  100 . The ventilator tubing facilitates the sampling of nitric oxide at a point downstream from the instillation point  225  of the nitric oxide (NO) gas, as shown in FIGS. 4 and 5. FIG. 4 depicts a Phasitron Y tube, which is a standard sliding Venturi valve system. This Y tube is modified by adding a port  205  for nitric oxide sampling. As shown in FIGS. 4 and 5, this port  205  is provided at a point downstream from the entrainment port  210  of the Y tube so as to permit NO gas sampling. This permits an operator to determine whether gas mixing is adequate. FIG. 4 depicts the state in which the valve system is unpressurized and open for passive expiratory flow, while FIG. 5 depicts the state in which the valve system is pressurized and closed for inspiratory subtidal-volume injection.  
         [0028]    The portable pediatric ventilation transport system  100  also includes a physiological monitor  400  attached to the ventilation transport system  100 . In the illustrated embodiment, the physiological monitor  400  is mounted to the transport main body  130  by a bracket  133 . This physiological monitor  400  is of a standard battery-driven type, and is capable of monitoring various patient parameters, including respiration, SpO 2  (pulse oximetry), ECG, non-invasive blood pressure, invasive blood pressure, carbon dioxide (end-tidal CO 2 ), and nitrous oxide. One example of a physiological monitor  400  is the “Millennia Patient Monitor,” produced by Invivo Research Incorporated (Orlando, Fla.). This again is simply one example, and the skilled artisan will appreciate that other physiological monitors may be employed without departing from the spirit and scope of the present invention.  
         [0029]    The oxygen supply chamber  110  provides storage for gas (oxygen) cylinders. Wheels  112  are attached to the ventilation transport system  100  at oxygen supply chamber  110 .  
         [0030]    The oxygen supply chamber  110  may accommodate a plurality of gas cylinders to enable sufficient oxygen administration during transport, as shown, for example, in the system and method disclosed in U.S. patent application Ser. No. 09/405,316, which is incorporated in its entirety herein by reference. In order to allow high-flow, high-pressure oxygen tanks to be adapted to a portable ventilator and to allow sufficient oxygen to be administered throughout the course of prolonged transport of a patient, the oxygen delivery system (not illustrated) may include at least a first set and a second set of individual oxygen tanks. A first intake tube is interposed between the first set of oxygen tanks and a first regulator, and the first regulator contains a valve that remains open until the pressure of oxygen flowing through the first regulator drops below a predetermined threshold pressure level. A second intake tube is interposed between the second set of oxygen tanks and a second regulator, and the second regulator contains a valve which remains closed until the pressure in the second regulator drops to approximately the predetermined threshold pressure level. This threshold pressure level is, in some embodiments, within the range of 90 to 100 pounds per square inch. One or more outtake tubes connect the first and second regulators, and a central tube is interposed between these outtake tubes and a mechanical ventilator. In some embodiments, there are two sets of oxygen tanks. One or more pressure gauges may be attached to the regulators (not illustrated). In addition, other supplies can also be stored in the oxygen supply chamber  110 .  
         [0031]    The illustrated patient chamber  140  is of a type that is commonly used in intensive care units and, in the case of chambers or beds sized for infants, may include a warming device (not shown) to regulate the temperature of the environment in which the patient is transported. This assists in maintaining the patient&#39;s body temperature at a normal level during transport. The patient chamber  140  illustrated in FIGS.  1 - 3  has a bed adapted for infant use and is provided with a cover  142  that is, at least partially, substantially transparent. Although not illustrated, the cover  142  may include a head access door, two hand insertion ports, and accessory ports for IV or respiratory tubing.  
         [0032]    One example of a patient chamber  140  that can be used in the ventilation transport system  100  is the “Multipurpose Infant Transport System Model 20H” produced by International Biomedical, Inc. (Austin, Tex.), which includes an incubator with a double-wall hood, a head access door, a front access door with two hand insertion ports, accessory ports for IV and respiratory tubing, a mattress, a high-intensity exam light, a skin temperature probe, an accessory module, an oxygen cart module, a double-wall hood for pediatric transport, IV syringe pumps, a humidifier, a suction device, a blender, and oxygen analyzer, a ventilator monitor, a physiological monitor and an infant ventilator. The “Multipurpose Infant Transport System Model 20H” does not include a high-frequency ventilator or a nitric oxide delivery system, and its physiological monitor cannot measure certain parameters measured by the physiological monitor  400  of the ventilation transport system  100 , such as nitrous oxide.  
         [0033]    An advantage of the ventilation transport system  100  is its compactness. Typically, the transverse width of the system ranges from about 15 inches to about 35 inches. In some embodiments, the transverse width of the device, including the cart, bed, and monitor, does not exceed 30 inches. In other embodiments, the width of the device does not exceed 25 inches. This relatively narrow width allows the ventilation transport system to be easily moved into and out of ambulances, emergency transport helicopters, and other patient transport vehicles, thus making it possible to conduct high frequency ventilation and inhaled nitric oxide therapy while a patient is being transported. As discussed above, due to space limitations within the transport vehicle, this was not previously conventionally possible. To accomplish this, the height and width of the device are adapted to fit within the patient-entry doorway of an ambulance or transport helicopter. For example, a year-2000 Ford model F350 ambulance, such as those operated by Lynch Ambulance Company (Anaheim, Calif.), has rear doors which open to form a patient-entry space of about 55 inches in height and 46 inches in width. Thus, the width of the ventilation transport system  100 , that is to say, the distance in FIG. 3 from the left side of the system to the right side of the system, allows for easy entry into this type of standard ambulance for patient transport. Other exemplary dimensions for the ventilation transport system  100  are as follows: height (from bottom to top of the system in FIG. 2): about 35 to about 50 inches; and length (from left side to right side of the system in FIG. 2): about 34 to about 50 inches.  
         [0034]    Furthermore, a second embodiment of the present invention is depicted in FIG. 6; this figure shows an embodiment adapted for the transport of persons larger than infants. The pediatric ventilation transport system  600  of this embodiment is similar to the ventilation transport system  100  described in connection with FIGS.  1 - 3 , except that it is modified to accommodate larger children or small adults.  
         [0035]    This transport system is provided with a mechanical or high-frequency ventilator  700  installed in a support module  610 , a physiological monitor  900 , and an inhaled nitric oxide delivery system  800 . The physiological monitor  900  and the inhaled nitric oxide delivery system  800  are attached to the support module  610  via brackets  611  and  612 . Commercially available unit components are assembled to form the remainder of the transport system of the second embodiment.  
         [0036]    As in the first embodiment above, the pediatric transport system  600  of this embodiment is provided with a ventilator  700 , which is preferably a mechanical ventilator, and more preferably a high-frequency ventilator. Advantageously, the high-frequency ventilator is capable of ventilating the patient in at least one of the following modes: positive pressure high-frequency ventilation, high-frequency jet ventilation, and high-frequency oscillatory ventilation. In one embodiment, the “VDR®-3C Universal Logistical Percussionator®,” produced by the Percussionaire® Corporation (Sandpoint, Ind.), was employed as this ventilator  700 . Other ventilators may be employed, as will be apparent to those of skill in the art.  
         [0037]    The pediatric ventilation transport system  600  also includes a nitric oxide delivery system  800 , which is mounted on bracket  611  of the support module  610 . As in the first embodiment described above, this nitric oxide delivery system  800  is preferably a nitric oxide delivery system capable of delivering therapeutic doses of inhaled nitric oxide. Advantageously, the nitric oxide delivery system is capable of monitoring of NO and NO 2  levels, and may employ a mass flow meter. As in the embodiment described above, either the chemiluminescence or the electrochemical detection method for NO and NO 2  gases may be employed. In the present embodiment, the “AeroNOx Portable System” produced by Pulmonox Medical Corporation (Alberta, Canada) was employed. The skilled artisan will readily appreciate that other nitric oxide systems may be employed and are within the scope of the invention.  
         [0038]    In this embodiment of the pediatric ventilation transport system  600 , as in the embodiment described above, a further modification is made to the ventilator tubing  220  in order to facilitate the sampling of nitric oxide at a point downstream from the instillation point of the NO gas, as shown in FIGS. 4 and 5. As shown in FIG. 3, the Phasitron Y tube, which is a standard sliding Venturi valve system, is modified by the addition of a port  205  for nitric oxide sampling. As shown, this port is provided at a point downstream from the entrainment port  210  of the Y tube so as to permit NO gas sampling. This permits an operator to determine whether gas mixing is adequate. FIG. 4 depicts the state in which the valve system is unpressurized and open for passive expiratory flow, while FIG. 5 depicts the state in which the valve system is pressurized and closed for inspiratory subtidal-volume injection.  
         [0039]    In addition, the pediatric ventilation transport system  600  of the present embodiment is further provided with a physiological monitor  900 , which is mounted to a bracket  612  of the support module  610 . As in the first embodiment described above, this physiological monitor  900  is preferably of a standard battery-driven type because it may be used in the field, away from a wall source of electricity.  
         [0040]    In addition, a number of commercially available component units are assembled with the ventilator  700 , the nitric oxide delivery system  800 , and the physiological monitor  900  to produce the pediatric ventilation transport system  600  of the present embodiment. The bed  613  thereof is adapted for persons larger than infants. The pediatric ventilation transport system  600  includes a support module  610 , a blender  620 , a flow meter  630 , gas contents gauges  640 , shut off valves  650 , an oxygen cart latch  660 , and syringe pumps  670 . These component units are representative of those commonly employed in conventionally available pediatric transport systems.  
         [0041]    The pediatric transport system  600  also includes a folding cart  710 , or an oxygen tank chamber that is provided with wheels to facilitate transport, as is depicted in FIG. 6. As in the embodiment described above, the oxygen tank cart  710  may accommodate a plurality of gas cylinders to enable sufficient oxygen administration during transport, as shown, for example, in the system and method disclosed in U.S. patent application Ser. No. 09/405,316. In this embodiment, a pediatric transport cart that was employed was the “Pedi-Porter” pediatric transport cart produced by International Biomedical, Inc. (Austin, Tex.). The “Pedi-Porter” is adapted for use with persons who are larger than infants. The “Pedi-Porter” pediatric transport cart includes a stretcher, a support module with yokes and regulators for gas cylinders, gas contents gauges, shut off valves, external gas connections, two IV poles, a mattress, a patient restraint system, a blender, a flowmeter, IV syringe pumps, a ventilator, and a physiological monitor. The “PediPorter” pediatric transport system does not include the high frequency ventilator or nitric oxide delivery system of the ventilator transport system  100 , and its physiological monitor cannot measure certain parameters measured by the physiological monitor  900  of the ventilation transport system  100 , such as nitrous oxide. Other pediatric transport carts can also be employed in the pediatric ventilation transport system  600 .  
         [0042]    Use of the ventilation transport systems  100  and  600  will now be described in detail. After an incident of respiratory failure is reported in a remote location, a transport team may be dispatched by air or ground ambulance, together with the portable ventilation transport system  100  or  600 , depending on the size of the patient. On arrival, the patient is placed on or in the transport system and is connected to the physiological monitor via ventilator tubing  220 . Mechanical ventilation and, if necessary, nitric oxide administration are initiated. Often, a neuromuscular blocking agent such as pancuronium bromide (Pavulon™) or succinylcholine chloride (Anectine™) is administered to the patient, along with a sedative, to facilitate ventilation. Once this has been accomplished, the patient is transported on or within the transport system to a hospital intensive care unit, where therapy may be continued.  
         [0043]    From the foregoing description, it will be appreciated that a novel approach for the ventilatory transport of patients has been disclosed. While aspects of the invention have been described with reference to specific embodiments, the description is illustrative and is not intended to limit the scope of the invention. Various modifications and applications of the invention may occur to those who are skilled in the art, without departing from the true spirit or scope of the invention. The breadth and scope of the invention should be defined only in accordance with the appended claims and their equivalents.