Peripheral Arterial Tone (PAT) is a noninvasive measure designed to track

pulsatile In fluid dynamics, a flow with periodic variations is known as pulsatile flow, or as Womersley flow. The flow profiles was first derived by John R. Womersley (1907–1958) in his work with blood flow in arteries. The cardiovascular system of chord ...

volume changes in peripheral arterial beds. The collected information gives specialists important insight into the

autonomic nervous system The autonomic nervous system (ANS), sometimes called the visceral nervous system and formerly the vegetative nervous system, is a division of the nervous system that operates viscera, internal organs, smooth muscle and glands. The autonomic nervo ...

and the

cardiovascular system In vertebrates, the circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the body. It includes the cardiovascular system, or vascular system, that consists of the heart a ...

. PAT technology is mostly used to detect

heart disease Cardiovascular disease (CVD) is any disease involving the heart or blood vessels. CVDs constitute a class of diseases that includes: coronary artery diseases (e.g. angina pectoris, angina, myocardial infarction, heart attack), heart failure, ...

erectile dysfunction Erectile dysfunction (ED), also referred to as impotence, is a form of sexual dysfunction in males characterized by the persistent or recurring inability to achieve or maintain a Human penis, penile erection with sufficient rigidity and durat ...

and

obstructive sleep apnea Obstructive sleep apnea (OSA) is the most common sleep-related breathing disorder and is characterized by recurrent episodes of complete or partial airway obstruction, obstruction of the respiratory tract#Upper respiratory tract, upper airway lea ...

The PAT technology

The PAT signal is a form of

pulse wave A pulse wave or pulse train or rectangular wave is a non-sinusoidal waveform that is the periodic version of the rectangular function. It is held high a percent each cycle ( period) called the duty cycle and for the remainder of each cycle is ...

amplitude The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of am ...

measured by incorporating both a unified

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and eve ...

field and a specific

isosbestic In spectroscopy, an isosbestic point is a specific wavelength, wavenumber or frequency at which the total absorbance of a sample does not change during a chemical reaction or a physical change of the sample. The word derives from two Greek words: ...

wavelength In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same ''phase (waves ...

. Applying a uniform pressure field around the measured surface releases

arterial An artery () is a blood vessel in humans and most other animals that takes oxygenated blood away from the heart in the systemic circulation to one or more parts of the body. Exceptions that carry deoxygenated blood are the pulmonary arteries in ...

wall motion restriction, magnifies the

dynamic range Dynamics (from Greek δυναμικός ''dynamikos'' "powerful", from δύναμις ''dynamis'' " power") or dynamic may refer to: Physics and engineering * Dynamics (mechanics), the study of forces and their effect on motion Brands and ent ...

of the recorded signal, and prevents the distention of the

veins Veins () are blood vessels in the circulatory system of humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are those of the pulmonary and fetal c ...

distal to the site of pressure application. The use of an isosbestic wavelength results in both

oxyhaemoglobin Hemoglobin (haemoglobin, Hb or Hgb) is a protein containing iron that facilitates the transportation of oxygen in red blood cells. Almost all vertebrates contain hemoglobin, with the sole exception of the fish family Channichthyidae. Hemoglobin ...

and deoxyhaemoglobin having the same absorption level, thereby preventing oxygen saturation level changes. These features result in high signal quality which differentiate PAT technology from other traditional peripheral pulse measurement methods.

Development history

The technology to acquire the PAT signal was developed by Dr. Bob Schnall and Dr. Koby Sheffy at Prof.

Peretz Lavie Peretz Lavie (; born 19 February 1949) was the 16th president of the Technion - Israel Institute of Technology, having taken the position on 1 October 2009 through September 2019. Lavie, an expert in the psychophysiology of sleep disorders, sleep a ...

's Technion laboratory following an observation made by a thoracic surgeon, Dr. Daniel Goor, who observed that during open heart surgery, when the heart becomes

ischemic Ischemia or ischaemia is a restriction in blood supply to any tissue, muscle group, or organ of the body, causing a shortage of oxygen that is needed for cellular metabolism (to keep tissue alive). Ischemia is generally caused by problems ...

, the patient's fingers become very cold and blueish. This was explained by increased sympathetic activity and the unique innervation of the finger's arterial bed by solely alpha-

adrenergic receptors The adrenergic receptors or adrenoceptors are a class of G protein-coupled receptors that are targets of many catecholamines like norepinephrine (noradrenaline) and epinephrine (adrenaline) produced by the body, but also many medications like be ...

pathways. As the PAT signal was manifesting sympathetic activity it was later used to assess exercise stress testing,

mental stress In psychology, stress is a feeling of emotional strain and pressure. Stress is a form of psychological pain, psychological and mental discomfort. Small amounts of stress may be beneficial, as it can improve athletic performance, motivation and ...

response and

sleep apnea Sleep apnea (sleep apnoea or sleep apnœa in British English) is a sleep-related breathing disorder in which repetitive Apnea, pauses in breathing, periods of shallow breathing, or collapse of the upper airway during sleep results in poor vent ...

. It is also used to assess

endothelial The endothelium (: endothelia) is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the res ...

function as the endothelial cells in the arterial walls also regulate vasoactivity. The first company to utilize PAT technology in its medical devices wa
Itamar Medical
an Israeli medical device manufacturer. Itamar developed unique probes with contiguous cuffs which are capable of applying a unified pressure to a finger, including its most distal tip. Apparatus And Method For Monitoring A Hemodynamic Condition Of A Subject, Particularly For Measuring Blood Pressure. Israel Patent #120109 (Filed 30/01/1997)

/ref>Method And Apparatus For The Non-Invasive Detection Of Medical Conditions By Monitoring Peripheral Arterial Tone. US Patent #6,319,205 (Filed 02/05/1997)

/ref>Schnall RP, Shlitner A, Sheffy J, Kedar R, & Lavie P. Periodic, Profound Peripheral Vasoconstriction – A New Marker of obstructive Sleep Apnea. SLEEP 1999; 22(7):939-46

/ref> There are two versions of PAT probes developed by Itamar Medical: A pneumo-optical sensing PAT probe, and a

pneumatic Pneumatics (from Greek 'wind, breath') is the use of gas or pressurized air in mechanical systems. Pneumatic systems used in Industrial sector, industry are commonly powered by compressed air or compressed inert gases. A centrally located a ...

sensing probe: The pneumo-optical sensing based probe detects

optical density Absorbance is defined as "the logarithm of the ratio of incident to transmitted radiant power through a sample (excluding the effects on cell walls)". Alternatively, for samples which scatter light, absorbance may be defined as "the negative log ...

changes of the measured finger and generates its own self-contained pressure field, by virtue of an arrangement of inner and outer membranes. Bar A, Pillar G, Dvir I, Sheffy J, Schnall RP, & Lavie P. Evaluation of a Portable Device Based on Peripheral Arterial Tone for Unattended Home Sleep Studies. Chest 2003; 123(3): 695-703

/ref> The pressure applied within the probe is independent of the volume of the finger, based on use of the outer pre-tensioned membrane, and governed by the

Young–Laplace equation In physics, the Young–Laplace equation () is an equation that describes the capillary pressure difference sustained across the interface between two static fluids, such as water and air, due to the phenomenon of surface tension or wall tensi ...

. The pneumatic sensing probe, senses finger blood volume changes based on pressure changes within a conventional constant volume, variable pressure pneumatic system, which also supplies the desired level of pressure to be used.

Clinical applications of the PAT technology

The PAT Technology has received regulatory approval in several countries to diagnose a variety of conditions involving changes in sympathetic activity. The most common use of the PAT technology is in detection of

sleep disordered breathing When we sleep, our breathing changes due to normal biological processes that affect both our respiratory and muscular systems. Physiology Sleep Onset Breathing changes as we transition from wakefulness to sleep. These changes arise due to biologi ...

such as

and

central sleep apnea Central sleep apnea (CSA) or central sleep apnea syndrome (CSAS) is a sleep-related Disorder (medicine)#Disorder, disorder in which the effort to Breathing, breathe is diminished or absent, typically for 10 to 30 seconds either intermittently o ...

PAT technology in sleep disordered breathing

A hallmark of sleep disordered breathing is the occurrence of arousals during sleep. Such arousals elicit generalized autonomic activation, which among other physiological changes, includes

sympathetic nervous system The sympathetic nervous system (SNS or SANS, sympathetic autonomic nervous system, to differentiate it from the somatic nervous system) is one of the three divisions of the autonomic nervous system, the others being the parasympathetic nervous sy ...

-mediated peripheral vasoconstriction, and transient pulse rate elevation. The PAT technology allows measurement of these changes in order to accurately diagnose sleep disordered breathing. Pillar G, Bar A, Bettito M, Schnall R, Dvir I, Sheffy J, & Lavie P. An automatic ambulatory device for detection of AASM defined arousals from sleep: the WP100. Sleep Med 2003; 4(3):207-212

/ref> Yalamanchali S, Farajian V, Hamilton C, Pott TR, Samuelson CG, & Friedman M. Diagnosis of Obstructive Sleep Apnea by Peripheral Arterial Tonometry: Meta-analysis. JAMA Otolaryngol Head Neck Surg 2013 Dec;139(12):1343-50

/ref> Pillar, Giora, Murray Berall, Richard Berry, Tamar Etzioni, Noam Shrater, Dennis Hwang, Marai Ibrahim et al. Detecting central sleep apnea in adult patients using WatchPAT— a multicenter validation study. Sleep and Breathing 2019 Aug: 1-12.

References

{{reflist Autonomic nervous system Cardiovascular system