Abstract:
A method including placing a portion of a foot of a newborn in a device, the device including a light emitter and a corresponding receiver coupled on opposite sides of the device, the device further including a processor for processing data from the light emitter and receiver; and determining a presence of congenital heart disease. An apparatus including a body including a chamber of a size to accommodate a portion of a newborn&#39;s foot; at least one light emitter and a corresponding detector coupled on opposite sides of the body, the emitter configured to emit light of a prescribed wavelength into the chamber; and a processor coupled to the body and configured to receive a signal from the at least one detector.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The application claims the benefit of the earlier filing date of co-pending U.S. Provisional Patent Application No. 61/375,875, filed Aug. 23, 2010 and incorporated herein by reference. 
     
    
     FIELD 
       [0002]    Pulse oximetry and congenital heart disease. 
       BACKGROUND 
       [0003]    Pulse oximetry is used to measure the arterial oxygen saturation of hemoglobin (SpO 2 ) and pulse rate of a patient. Measurement of these characteristics is accomplished by use of a non-invasive sensor which scatters red and infrared lights through a portion of the patient&#39;s tissue where arterial blood perfuses the tissue. The sensor then senses the absorption of light photoelectrically by the tissue. The differential amounts of red and infrared light absorbed are then used to calculate the percentage of hemoglobin in the arterial blood that is saturated with oxygen. 
         [0004]    Pulse oximetry is commonly used as a monitoring device in the emergency departments, intensive care units, observational units, and operating rooms. Most pulse oximeter probes are designed for prolonged, continuous monitoring of the SpO 2  and pulse rate of a patient. These probes are generally shaped as a clip for the finger or toe, or for infant using adhesive tapes for wrapping around the foot. For spot check of SpO 2  or for the purpose of screening, using disposable probes is time consuming and not cost effective. 
         [0005]    Congenital heart disease (CHD) affects  8  per 1,000 live-born infants and is one of the most common and serious types of birth defect. If diagnosed early, CHD can be managed with successful surgical repair or palliation for the majority of infants. A missed or delayed diagnosis can be life threatening or result in long-term morbidities for these infants. Current clinical practice for detecting CHD in newborns relies on a clinician performing a physical examination before the child&#39;s routine discharge from the nursery. A significant number of newborns with CHD are missed by routine physical examination. 
         [0006]    In recent years, health care professionals have found pulse oximetry an important screening tool to aid clinical examination for detecting some severe forms of CHD. In a 2007 survey of 1,086 pediatric cardiologists, the majority of respondents support a mandate for universal screening by pulse oximetry before newborn discharge. In 2009, the American Heart Association and American Academy of Pediatrics jointly issued a scientific statement recommending routine pulse oximetry screening on the foot of asymptomatic newborns after 24 hours of life, but before hospital discharge. 
         [0007]    The commonly used pulse oximetry sensors require attachment to the fingers or toes. In infants and neonates, the fingers and toes are too small for the clip-type of pulse oximetry sensor commonly used in older children and adults. Commonly used approaches include taping the pulse oximetry sensor in place on the finger/toe or hand/foot by adhesives or by Velcro. These sensors are generally single-use therefore adds substantial expenses to the universal screening of all newborn at hospital discharge. Taping a pulse oximetry sensor on an infant&#39;s toe or foot takes a considerable amount of time, which adds difficulty to screen a large number of newborns. Furthermore, the taping the pulse oximetry sensors on the toe or the foot is prone to motion artifacts, and signal interferences from ambient lights, which are less than ideal to be used in a setting of newborn screening. To summarize, the current pulse oximetry sensors cannot be used for newborn CHD screening because the single-use sensors add to the cost, takes a significant amount of time to place the sensors, and are prone to artifacts from motion and ambient light. 
         [0008]    Kiani (US 2008/0071155 A1) teaches an invention of a congenital heart disease monitor using a pulse oximeter. The pulse oximeter uses conventional finger or wrap around probes to measure SpO 2  from upper and lower extremities. 
         [0009]    Mannheimer (U.S. Pat. No. 5,842,982) teaches an improved infant/neonatal pulse oximeter sensor that attaches to an infant&#39;s foot. A pad conforms to the heel of an infant, with the light emitter and a detector being mounted below the achilles tendon and below the calcaneus bone. The heel pad can be held in place with a stretchable sock. 
         [0010]    Jackson III (US 2002/0133067 A1) discloses an invention of a SIDS warning device by a pulse oximeter mounted in a woven foot wrap. This device uses a low-powered transmitter to transmit readings to a remote monitoring unit. The wrapping is made of an opaque elastic material that secure not only around the arch and ball area of the infant&#39;s foot, but also around the ankle. The pulse oximeter will be placed in the wrap on the dorsal and plantar area near the arch of the infant&#39;s foot. 
         [0011]    Pulse oximter probes to be used at other parts of the body have been proposed by other inventers. Melker et al (US 2004/0260161 A1) teaches a pulse oximeter probe to be used on the lip or cheek. Melker et al (WO 2005/065540 A1) also teaches a pulse oximeter probe to be used on the nose. Shepard et al (US 2002/0028990 A1) teaches a pulse oximeter probe to be used in the posterior pharynx. Although these pulse oximeter probes may be useful for patient monitoring, they cannot be used on newborns. Furthermore, the American Academy of Pediatrics specifically recommends the pulse oximetry to be performed on the foot for the purpose of screening for critical congenital heart disease. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is an illustration of one embodiment of a newborn pulse oximeter device with a hollow space in the center to place a newborn&#39;s foot in. 
           [0013]      FIG. 2  is a diagram showing a top surface of the newborn pulse oximeter device shown in  FIG. 1 . 
           [0014]      FIG. 3  is a diagram showing an under surface of the newborn pulse oximeter device shown in  FIG. 1 . 
           [0015]      FIG. 4  is an illustration of the arterial blood supply of the foot. 
           [0016]      FIG. 5  is an illustration of the positions of emitters and receivers inside the newborn pulse oximeter device of  FIG. 1  for detecting signals from the arteries of the newborn&#39;s foot. 
           [0017]      FIG. 6  is an illustration of the longitudinal section view of the newborn pulse oximeter device of  FIG. 1  with the newborn&#39;s foot in the oximeter. 
           [0018]      FIG. 7  is a top side view illustration of a cover that may be positioned within the newborn pulse oximeter device of  FIG. 1 . 
           [0019]      FIG. 8  is a diagram showing the electrical connections of the receivers to the signal processor for the newborn pulse oximeter device of  FIG. 1 . 
           [0020]      FIG. 9  is a diagram showing the algorithm for signal processing and power management for the newborn pulse oximeter device of  FIG. 1 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0021]      FIG. 1  illustrates one embodiment of a newborn pulse oximeter device. In this embodiment, device  5  has a tubular body with an open front end. The tubular body defines hollow space or chamber  10  sized to accommodate at least a portion of a newborn&#39;s foot (toes first) for signal acquisition. Opposite the open front end of case  16  of device  5 , in this embodiment, the case has a closed back end. As illustrated, in one embodiment, the closed back end has a dome shape. It is appreciated that other shapes are possible (e.g., flat, pyramidal, etc.). In another embodiment, the closed back end may be open or partially open. It is further appreciated that, although case  16  of device  5  is shown having a tubular shape, other shapes are possible, so long as a portion of a newborn&#39;s foot can fit inside. Details of device  5  are further illustrated in  FIGS. 2 ,  3  and  6 . 
         [0022]      FIG. 2  shows a top side surface of device  5 . In one embodiment, case  16  of device  5  is made of a cellulose-based plastic. A top surface of case  16  contains components to control an operation of the device and provide information. Two main components of the top surface are power button  15  and display  14 . In display  14 , signals representative of one or more of SpO 2  (oxygen saturation), heart rate, and arterial pulse waveforms may be displayed. Referring to display  14  of  FIG. 2 , the signals are displayed in panel  11  as SpO 2 , panel  12  as heart rate, and panel  13  as arterial pulse waveforms. Display  14  is, for example, a liquid crystal display (LCD). In one embodiment, there are two indicator lights ( 41  and  42 ). Indicator light  41  displays the quality and strength of the pulse signals, using, for example, a green color indicator for good signal quality, an amber color as questionable or borderline signal quality, and a red color as poor signal quality. Indicator  42  provides a pass/fail indication for a congenital heart disease. When, for example, a newborn&#39;s foot is placed in device  5  and there are greater than 10 seconds of a green color signal on indicator  41 , and the SpO 2  reading on panel  11  is equal or greater than 95 percent, indicator  42  will display a green color light to indicate that the newborn has passed the screening test. When there are greater than 10 seconds of a green color signal on indicator  41 , and the SpO 2  reading on panel  11  is lower than 95 percent, indicator  42  will display a red color light to indicate that the newborn has failed the screening test. In one embodiment, port  17  in the back side of the oximeter is used for connecting to an external pulse oximeter probe which can be the conventional finger clip on probe or existing infant probes with adhesive tapes for wrapping around the foot. 
         [0023]      FIG. 3  shows an under side surface of newborn pulse oximeter device  5 . In one embodiment, device  5  is battery-operated. Accordingly, an under side surface of device  5  includes a battery compartment  18  with a removable cover. In one embodiment, the batteries are standard AAA or AA batteries that can be replaceable when needed. In another embodiment, the batteries are lithium based rechargeable batteries. An under side surface of device  5  also includes, in this embodiment, connector  19  that is used for plugging device  5  to an AC adaptor for battery charging or as a separate power source for device  5 . 
         [0024]      FIG. 4  is an anatomical illustration of the arterial blood supply of the foot. The two major arteries to the foot are anterior tibial artery  51  and posterior tibial artery  52 . Anterior tibial artery  51  branches to dorsalis pedis artery  53  which courses through the dorsal side of the foot to the first toe. Posterior tibial artery  52  courses through the ventral side of the foot and becomes plantar arch artery  54 . 
         [0025]      FIG. 5  is an illustration of the positions of light emitters and receptors associated with device  5 . In one embodiment, the light emitters and detectors are connected to device  5 , such as connected (adhered) to case  16  in chamber  10  to emit light and receive light in chamber  10 . In one embodiment, there are three pairs of light emitters  21 ,  22 ,  23  and receivers ( 31 ,  32 ,  33 ) of device  5 . It is appreciated that there can be more or less than three pairs of light emitters and detectors. The illustration is a view from an under side surface of device  5  and the ventral surface of foot  50 , therefore, receivers  31 ,  32 ,  33  are shown, but emitters  21 ,  22 ,  23  are, on the other side of foot  50 , are not shown in the illustration of  FIG. 5 . The pair of emitter/receiver  21 / 31  are separately connected to case  16  and positioned inside chamber  10  to detect the pulse signals from dorsalis pedis artery  53  of the first toe when the infant&#39;s right foot is placed inside the chamber  10  of device  5 . The pair of emitter/receiver  23 / 33  are separately connected to case  16  and positioned inside chamber  10  to detect the pulse signals from dorsalis pedis artery  53  of the first toe when the infant&#39;s left foot is placed inside the chamber  10 . The pair of emitter/receiver  22 / 32  are separately connected to case  16  and positioned inside chamber  10  to detect the pulse signals from plantar arch artery  54  of the foot when either the right foot or left foot is placed inside chamber  10 . In one embodiment, each emitter emits a light at red (660 nanometers (nm)) and a light at infrared (940 nm), possibly modulated, to pass through a newborn&#39;s foot and be detected by the corresponding detector. Each emitter  21 ,  22 ,  23  is electrically connected to a processor and instruction logic in the processor directs the emission of light (red and infrared) from each emitter. Likewise, each receiver  31 ,  32 ,  33  is electrically connected to the processor and transmits received signals to the processor. A receiver produces an electrical signal corresponding to the red and infrared light energy attenuated from transmission through a newborn&#39;s foot. 
         [0026]    Pulse oximetry uses the differential light absorption of oxygenated hemoglobin HbO 2 , and deoxygenated hemoglobin, Hb, to compute their relative concentrations in the arterial blood. The arterial saturation of hemoglobin, SpO 2 , may then be calculated as SpO 2 =100 C HbO2 /(C Hb +C HbO2 ). 
         [0027]      FIG. 6  is an illustration of a longitudinal sectional view of pulse oximeter device  5  with a newborn&#39;s foot in chamber  10 . In this view, light emitters  21 ,  22 ,  23  are located on the top side of the chamber, and the paired receivers  31 ,  32 ,  33  located on the bottom side directly opposite the paired emitters. When the newborn&#39;s foot  50  is inside chamber  10 , the paired emitter and receiver are on either side of foot  50  in order to have the infrared and red lights traverse through dorsalis pedis artery  53  or plantar arch artery  54 . Power button  15  and LCD display  14  are on the top surface of the oximeter as viewed.  FIG. 6  also shows processor  6  and memory  7  in or on case  16  on a top side of device  5  as viewed. Processor  6  is electrically connected to emitters  21 ,  22 ,  23 ; to receivers  31 ,  32 ,  33 ; and to port  17 . Battery compartment  18  and charging port  19  are located on the under side of the oximeter. 
         [0028]    In one embodiment, a single use interior cover for pulse oximeter device  5  will be used to protect a newborn&#39;s skin, prevent infection and enhance signal acquisition.  FIG. 7  shows disposable cover  70  shaped to fit within the interior of device  5  (in chamber  10 ) before placing a newborn&#39;s foot into chamber  10 . Representatively, cover  70  is made of a thin polyurethane membrane and shaped to fit the interior of the device. The membrane may be translucent or is translucent in the six locations (shown are three locations  71 ,  72 ,  73 ) that correspond to the locations of the three pairs of light emitters  21 ,  22 ,  23  and their respective receivers  31 ,  32 ,  33  in the device. By using a design where only the six locations of the membrane are translucent, there is a reduction in potential “noise” and the chance of optical detector saturation from ambient lights. It will also minimize light scattering from the interior of the unit from emitters in one channel to the receiver of another channel. As shown in  FIG. 7 , in one embodiment, cover  70  includes plastic ring  75  at the end opening of cover  70  to provide a shape of the cover similar to a shape of chamber  10  of device  5 . An applicator may be used for easy placement of cover  70  into device  5 . A membrane of cover  70  may be impermeable to micro-organisms and pre-sterilized to protect against infection. No adhesives need to be applied to the side of the membrane with skin contact to avoid irritation. Polyurethane is commonly used in surgical implants and is the material in Tegaderm® (3M), which has been used extensively in neonates with very low rate of skin irritation or allergy. 
         [0029]      FIG. 8  is a diagram showing the electrical and signal connections of the receivers  31 ,  32 ,  33  to signal processor  45  of pulse oximeter device  5 . Receiver  40  is an optional external oximeter probe connected to the oximeter via port  17  (see  FIG. 2 ). Signal processor  45  receives signals from receivers  31 ,  32 ,  33  and  40  and processes the signals based on the algorithm stored in a memory associated with signal processor  45  in device  5 . In one embodiment, signal processor contains program instructions in machine readable form to receive from receiver(s) emitted signals from the emitter(s) directly connected to the device (emitters  21 ,  22 ,  23 ) or from an external receiver (e.g., receiver  40 ) and determine the best quality signal(s). Signal processor  45  also contains instructions to perform a machine readable method to determine SpO 2  and pulse rate based on received signals from receivers directly connected to the device ( 31 ,  32 ,  33 ) or external to it and to make a determination of congenital heart disease if, for example, an SpO 2  reading is below 95 percent for a period of time. Signal processor  45  performs its program instructions (e.g., a machine readable method) and displays data and results at display  14  and indicator lights  41  and  42 . 
         [0030]      FIG. 9  shows algorithm  60  for signal processing and power management of pulse oximeter device  5 . When an operator pushes power button  15  to turn device  5  on (block  61 ), signal processor  45  will first search signals from external receivers (e.g., receiver  40 ,  FIG. 8 ) (block  62 ). If signal(s) are found from external receiver(s), signal processor  45  will search signals from internal receivers  31 ,  32 ,  33  (block  63 ). If signal(s) are found, signal processor  45  can interpret both internal (e.g., lower extremity (foot)) and external (e.g., upper extremity) signals (block  64 ). Processor  45  will then identify the best quality internal signals (block  65 ), and display the results of the internal and external signals on display  14  (see  FIG. 2 ) (block  66 ). The quality of the signals will be shown by indicator light  41  (see  FIG. 2 ). If no signals are found in receivers  31 ,  32  or  33 , processor  45  will read only the signal(s) from external receiver(s) and display signals from the external receiver(s) (blocks  67  and  68 ). 
         [0031]    If no signals from external receiver(s) are found initially (block  62 ), processor  45  will search for signals from internal receivers  31 ,  32 ,  33  (block  69 ). If signals are found from internal receivers  31 ,  32 ,  33 , processor  45  will read such signals (block  70 ) and select the best quality signal (block  71 ). The best quality signal (from receivers  31 ,  32 ,  33 ) will be processed and displayed on display  14  (block  72 ). If no signals from internal receivers  31 ,  32 ,  33  are found, the power will be turned off (block  73 ). 
         [0032]    As will be understood by those skilled in the art, the current invention may be embodied in other forms without departing from the essential characteristics thereof. The foregoing description is intended to be illustrative, but not limiting, of the scope of the invention which is set forth in the following claims.