definition - kbso · • definition creative application of scientific principles to design or...

• Definition

Creative application of scientific principles to design or develop structures,

machines or works utilizing them

Almost everything you eat, wear, use and like to do involves engineering.

mobile, computer, clothes, medicine, space, national security and renewable energy, …

But most of all, engineering is about SOLVING REAL WORLD PROBLEM!

• Scientist and engineer

Scientist

Develops knowledge from analysis and study

Characteristic activity: research

Engineer

Uses knowledge to create something new

Finding out what people need, developing ideas and the product on time, seeing

how products can be made at a good price….

Characteristic activity: creative design

-Theodore Von Karman, Aerospace Engineer

“Scientists discover the world that exists; engineers create the world that never was.”

• The brain malfunctions:

Cut off or damaged fuel supply

cerebrovascular diseases, stroke, etc.

Physically insulted

Trauma, cerebrospinal fluid disorders, etc.

Under ill-maintenance

bacterial / viral infections, secondary tumor,

etc.

Inherent limitations

Congenital disorders, genetic deficits,

neurodegenerative disorders, etc.

• Brief specifications of the brain for engineers

As a chunk of fat and protein, the brain needs constant

supply of fuel (oxygen and glucose) to function

Without sufficient supply of fuel, it starts show

malfunction

The brain receives its fuel by blood via blood vessels

External damage to the brain is dampened by skull and

cerebrospinal fluid (CSF)

The total volume inside the skull is FIXED

The point is, we engineers see the brain as what it is;

a blood-fuelled, physical entity encased in a thick skull

This concept is super important,

so please, please remember this!

• Structure

The frontal lobe can be divided into a lateral, polar, orbital

(above the orbit), and medial part

Central Sulcus

Broca’sArea

Motor Strip (Primary Motor

Cortex)

Frontal Eye Fields

Copyright © 2016 Wolters Kluwer • All Rights Reserved

• (Bilateral) Frontal lobe dysfunction

Personality disorders, dementia, Apathy, Disinhibition

• Surgical resection

The anterior 7cm of one frontal lobe can be resected

without significant neurological sequelae, providing

the contralateral hemisphere is normal

This may account for the relative late presentation

and large size of some frontal lesions

Resections more posterior than this in the dominant

hemisphere are likely to damage the anterior speech

area

• Important areas/roles

Decision making, executive function

Ability to project future consequences

Choice of good and bad actions

Suppression of socially unacceptable responses

Determination of similarities and differences

between things or events

Sylvian fissure

Wernicke’s area

• Structure

The lateral surface of the temporal lobe is consists of superior,

middle, and inferior temporal gyri

• Temporal lobe dysfunction

Memory impairment, personality changes, seizures

• Surgical resection

Anterior portion of one temporal lobe (approx. at the junction

of the Rolandic and Sylvian fissures): low risk of neuro disability

Generally 4cm (the dominant lobe) or 6cm (the non-dominant lobe)

Superior temporal gyrus: generally preserved to protect the

branches of the middle cerebral artery (MCA) lying in the Sylvian fissure

Posterior portion: resection may damage the speech area

Medial aspect of uncus: should carefully resected because of its

proximity to the optic tract


• Important areas/roles

Memory

Cortical representation of olfactory

Auditory and vestibular information

Some aspects of emotion and behavior

Speaking (Wernicke’s speech area in the

dominant hemisphere)

Part of the visual field pathway

• Location

From the central sulcus to the parieto-occipital sulcus posteriorly and to

the temporal lobe inferiorly

• Roles

Anterior zone – processes somatic sensations and perceptions

Posterior zone – specialized primarily for integrating sensory input from

the somatic and visual regions and, to a lesser extent, from other sensory

regions, mostly for the control of movement

• Parietal lobe dysfunction

left parietal lobe - Gerstmann’s Syndrome, aphasia, agnosia

Bi-lateral damage - Cortical sensory loss or inattention, Balint’s Syndrome

ocular apraxia, simultanagnosia, and optic ataxia

right parietal lobe - contralateral neglect of part of the body or space

constructional apraxia anosognosia, alexiaParieto-occipital Sulcus

Somatosensory Cortex

• Roles

Center of the visual processing (“visual cortex”)

• Occipital lobe dysfunction

Homonymous field defect without macular sparing

Visual hallucinations (flashes of light, rather than the formed images that are

typical of temporal lobe epilepsy)

• Surgical Resection

Resection of the occipital lobe will result in a contralateral homonymous

hemianopia

The extent of resection is restricted to 3.5 cm from the occipital pole in the

dominant hemisphere because of the angular gyrus, where lesions can

produce dyslexia, dysgraphia and acalculia

In the non-dominant hemisphere, up to 7 cm may be resected

• Any brain injury other than congenital or genetic neurological

disorders

• Two major forms: Traumatic brain injury (TBI) and stroke

• After the initial physical damage, the ABI often develops

SECONDARY injuries

Primary injury: The injury caused by the actual damage from

1. direct contact with the cause of the accident

2. diffuse injury due to rapid acceleration or deceleration

Secondary injury: Pathologic changes in the brain AFTER the

incident (e.g. ischemia after massive hemorrhage)

• Traumatic brain injury (TBI)• Stroke (ischemic / hemorrhagic)

Systemic

hypotension

Sympathetic

nervous system

hyperactivity

Vascular

occlusion

Diffuse axonal

injury

Vascular

rupturing/leakage

Physical

disruption of

neuronal membranes

Cytotoxic

edema

Axonal necrosis

& swelling

Decreased

myocardial

contractility

Vasogenic

edema

Reduced cerebral

blood flow

Systemic

hypotension

Normal (left) vs. edematous (right) brain

Intracellular water accumulation

Interstitial fluids depletion

Increased osmotic gradient

Compression of nearby capillaries

Cytotoxic edema

Normal

Vasogenic edema

Cytotoxic

edema

Necrosis &

swelling

Vasogenic

edema

(further) Reduced

cerebral blood flow

Parenchyma compartment

CSF compartment

Vascular compartment

𝑉𝑏𝑟𝑎𝑖𝑛 + 𝑉𝑏𝑙𝑜𝑜𝑑 + 𝑉𝐶𝑆𝐹 = 𝑐𝑜𝑛𝑠𝑡.

∴ 𝐼𝑓 𝑡ℎ𝑒 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑜𝑛𝑒 𝑐𝑜𝑚𝑝𝑎𝑟𝑚𝑒𝑛𝑡 𝑖𝑛𝑐𝑟𝑒𝑎𝑠𝑒𝑠 𝑤𝑖𝑡ℎ𝑜𝑢𝑡 𝑡ℎ𝑒 𝑣𝑜𝑙𝑢𝑚𝑒 𝑑𝑒𝑐𝑟𝑒𝑎𝑠𝑒𝑠 𝑖𝑛 𝑜𝑡ℎ𝑒𝑟 𝑐𝑜𝑚𝑝𝑎𝑟𝑡𝑚𝑒𝑛𝑡𝑠;𝑡ℎ𝑒 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑖𝑛𝑠𝑖𝑑𝑒 𝑡ℎ𝑒 𝑠𝑦𝑠𝑡𝑒𝑚 𝑖𝑛𝑐𝑟𝑒𝑎𝑠𝑒𝑠

MABP - ICP = Cerebral perfusion pressure

Brain volume increase

Cranium

Blood flow

CO2

O2

Delivery ConsumptionIntracranial pressure

builds up

Mean arterial blood pressure

Cytotoxic edema

Vasogenic edema

Necrosis & swelling

• Cerebral autoregulation under normal condition • Cerebral autoregulation after Injury

Cere

bra

l Blo

od F

low

/min

]

CPP mmHg50 150

MABP

125

Optimal Zone

50 150

MABP25

75

125

CPP mmHg

Optimal Zone

Cere

bra

l Blo

od F

low

/min

]

Lowered cerebral blood

flow

Tissue swelling

Increase inintracranial pressure

Decrease in cerebral

perfusion pressure

Impaired cerebral

autoregulation

Systemic hypoperfusion

vicious cycle

• Initial damage to the brain, if severe, could lead to cerebral ischemia, edema, and increase in ICP

• Increase in ICP could lead to decrease in CPP, hence decreased CBF, which is aggravated by impaired cerebral autoregulation, or systemic hypotension, decreased myocardial contractility

∴ Accurately assessing the extent of seconda

ry ischemic-edematous insult, and evaluating

the cerebral perfusion after ABI could signific

antly help the clinicians, hence the patients

• Definition and symptom

An active distension of the ventricular system due to mismatch between CSF

production and its absorption

Dilatation of ventricle is the common result; ventricular enlargement

Increased intracranial pressure (ICP), enlargement of the head, mental disability

• Definition and symptom

Whether the ventricular system communicates with the subarachnoid space

① Communicating types

② Non-communicating types

Normal pressure hydrocephalus - other types

• For diagnosis, we can use:

– Assessment of clinical symptoms (“Hakim triad”), Neuroimaging (mostly MRI)

(Gallia GL, et al., Nat Clin Pract Neurol ,1998)

– CSF infusion test is needed to minimize the risk of shunt complications

(Farahmand, et al., J Neurol Neurosurg Psychiatry, 2009Rekate, Harold L., Cerebrospinal fluid research, 2008Jouibari, Morteza Faghih, et al., Child's nervous system, 2011

• Characterized by its classic ‘triad’ of symptoms (also known as the Hakim

triad)

Cognitive deterioration, gait disturbance and urinary incontinence

• Recent (2003) guidelines for diagnosing NPH suggest that NPH should be

suspected if

① CSF opening pressures between 5 ~ 18 mmHg

② Evan’s index of at least 0.3, with temporal horn enlargement, periventricular

signal changes, periventricular edema etc.

③ Gait disturbance + at least 1 other symptom in Hakim triad

• CSF shunt is the only viable treatment option

• Often misdiagnosed as Parkinson’s disease, Alzheimer’s disease, dementia

or cerebral atrophy

• FEWER THAN 20 % of those with the NPH receive an appropriate diagnosis

(Relkin N et al., Neurosurgery 2005)

• Cause: gene mutation

• Presentation

Short stature, short limbs, large head, prominent forehead, midface

hypoplasia, lumbar lordosis, genu varum (bow-leggedness), ‘trident’ hands

• Complication

Hydrocephalus, spinal cord compression, syringomyelia, recurrent ear

infections, dental malocclusion

• Macrocephaly in achondroplasia

No clinical evidence of increased ICP, but the measured level of ICP remai

ned at high (possibly, chronic) and have enlarged and stable ventricles (Erd

incler, P., et al., Child's Nervous System, 1997)

• In general, shunt placement in the patient with achondroplasia is not

straightforward, and the incidence of revisions and complications is hi

gher than in the general patient population with shunts (King, James AJ, e

t al., Journal of Neurosurgery: Pediatrics, 2009)

• Treatment by surgically inserting a shunt system

• The shunt redirects CSF out of the head through the tubing to a

location elsewhere in the body where it can be absorbed

VP shunt : Ventriculo-Peritoneal

VA shunt : Ventriculo-Arteial

LP shunt : Lumbar-Peritoneal

• Complications

Obstruction, over / under drainage, fracture/disconnection, infection

• Still, it is the best what we have for treating hydrocephalus and various

CSF disorders. Thus, following problems arise:

Which patients need shunt?

how do we know where to look if shunt malfunction happens

http://neuroanimations.com/Hydrocephalus

/Shunts/VP_Shunt.html

VP shunt VA shunt

• 𝑅𝑜𝑢𝑡 = 𝑅𝑛

• Resistance of the CSF outflow

Sum of total resistances

include at the foramen of Munro, the aqueduct, the foramen of Luschka and

Magendie, the subarachnoid spaces of the infra- and supra-tentorial regions,

the tentorial notch, and the arachnoid granulations of the venous sinuses

• Multiple resistances at the various regions of the CSF pathway may

cause hydrocephalus

• The degree and the location of a resistance increase may determine

the treatments associated with the different types of hydrocephalus

• Rout range

Normal Rout : 6 - 12 mmHg/(minml-1)

Grey zone of Rout : 13 - 18 mmHg/(minml-1)

Threshold of Rout : >18 mmHg/(minml-1)

CSF circulation model (A. Marmarou 1973)

• CSF pressure = 𝑃𝑠𝑠 + 𝑅𝑐𝑠𝑓 × 𝐼𝑓𝑜𝑟𝑚𝑎𝑡𝑖𝑜𝑛

• “CSF pressure equals pressure in sagittal sinus (𝑃𝑠𝑠) plus

resistance to CSF outflow (𝑅𝑐𝑠𝑓) times CSF formation (𝐼𝑓𝑜𝑟𝑚𝑎𝑡𝑖𝑜𝑛)”

• Pre-shunted patient • Post-shunted patient

• Before shunting: Normal ICP, fast rising during infusion Infusion interrupted at 40 mmHg, Rout > 20 mmHg/(ml/min) big amplitude to CSF outflow (4

mmHg)

• After shunting (Strata @ 1): Normal ICP, low rise in pressure

during the test Rout - 4 mmHg/(ml/min) Low amplitude of pulse waves (1

mmHg)

a) Normal b) Under drainage c) Proximal blockage d) Distal blockage

• Example of infusion study associated with shunt analysis

FIGURE CSF circulation model with shunt system

http://neuroanimations.com/Hydrocephalus/Shunts/VP_Shunt.html

Czosnyka, Z. H., et al. "Hydrocephalus shunts and waves of intracranial pressure." Medical

and Biological Engineering and Computing 43.1 (2005): 71-77.


• Human behavior

Product of brain activity

• Brain

Product of two mutually interacting factors;

Heredity – Even identical twins, have different shape of

brain because of DNA

Environment – History of personal life (e.g. somatosensory map)

• Physical vs. mental health?

Ignorance or the lack of biological explanation on disorders of mood,

thought and behavior has reinforced the dichotomy

• Psychiatric disorders

Higher brain functions such as fears, moods, and thoughts are disturbed

Anxiety disorders, affective disorders, schizophrenia


• Anxiety disorder

Characterized by significant feelings of anxiety and fear

A number of anxiety disorders; panic disorder, agoraphobia, obsessive-

compulsive disorder, generalized anxiety disorder , specific phobia, post-

trauma stress disorder (PTSD)

• Stress response

Coordinated reaction to threatening stimuli

Hypothalamic-pituitary-adrenal (HPA) axis

Stress corticotropin-releasing hormone (CRH) adrenocorticotropic hormone(ACTH) cortisol

CRH - chemical messenger between the paraventricular nucleus of the hypothalamus and the anterior pituitary gland

ACTH – released by the pituitary gland, travels in the bloodstream to the adrenal gland

Cortisol – broad variety of effects throughout our system, including metabolic, cardiovascular, and immune responses

Dedovic, Katarina, et al. Neuroimage 47.3 (2009): 864-871.


• Regulation of HPA Axis

Push – pull regulation of the HPA axis by the

Amygdala, Hippocampus

Anxiety disorders have been related to both

• Amygdala regulation

Inappropriate activation of amygdala was seen in some anxiety disorders

Bed nucleus of stria terminalis (BNST)

• Hippocampus regulation

Hippocampus inhibits CRH release

Continuous stress can cause hippocampal neurons to die

Human PTSD patients have shown a decrease in hippocampal volume

hyperactivity of the amygdala and diminished activity of the hippocampus


• Affective disorders

Affect - Emotional state or mood

Feeling that one’s emotional state is no longer under one’s

control

Main types of affective disorders are depression, bipolar

disorder

Symptoms vary by individual, and can range from mild to

severe

• Monoamine Hypothesis of mood disorders

Reserpine :

Blood pressure control drug caused psycho)c depression

in 20% cases

Deplete catecholamines and serotonin (interfere with

synaptic vesicle loading)

Monoamine Oxidase (MAO) :

Tuberculosis drug caused a marked

elevation in mood

MAO inhibitor

Imipramine :

Antidepressant

Inhibits reuptake of serotonin and

norepinephrine


Disrupted feedback

Decrease in glucocorticoid receptor (GR)

expression

Diminished hippocampal response to cortisol

GR expression regulation

Early sensory experience (tactile stimulation by

mother)

Ascending serotonergic inputs to hippocampus

Increased gene expression

• The Diathesis-Stress Hypothesis

Genetic and nongenetic : family history and

early childhood experience (abuse, neglect),

stresses of life

HPA system : main site of convergence

(genetic and environmental influences)

Comorbidity : anxiety and depression - both

can be incurred by exaggerated HPA activity

HPA function : causal relationship?

CRH injection into brain caused depression

Symptoms : insomnia, decreased appetite,

decreased interest in sex, increased anxiety


• The Dopamine Hypothesis

2 Links between dopamine and schizophrenia

1. Effects of Amphetamine in healthy people

Enhances neurotransmission at catecholamine-utilizing

synapses and causes the release of dopamine

Resemblance to schizophrenia of Amphetamine’s normal

stimulant action

Addictive properties – craving Amphetamine

2. Central nervous system affecting drugs

Chlorpromazine, initially developed as an antihistamine,

could prevent the positive symptoms in schizophrenia

Potent blockers of dopamine receptors.

The correlation between the dosage effective for

controlling schizophrenia

Atypical neuroleptics

Clozapine

No effect on dopamine receptor

Evidence that schizophrenia seems to

be more than an overactive dopamine

system


• The Glutamate Hypothesis

Behavioral effects of phencyclidine (PCP)

Caused postoperative side effects

hallucinations and paranoia

Illegal drug, known on the street as an ‘angel dust’ or ‘hog’

No effect on dopaminergic transmission

Affects synapses that use glutamate as a neurotransmitter

Inhibits NMDA receptors

Glutamate: Fast excitatory neurotransmitter in the brain,

two important receptor subtypes, AMPA and NMDA

Animal study

Low doses of PCP mice or genetically engineered to express

fewer glutamate receptors mice

Produce changes in brain biochemistry

and behavior that resemble those in

schizophrenic patients

• CT (Computed Tomography) records a series of coplanar projections by rotating the source and detector around the patient

• Recorded projections are then used to recover the X-ray attenuation of each point in the plane

• CT has replaced the use of plain skull radiographs and is routinely used to assess all patients with acute neurological injury and head trauma

• Advantages

Early assessment of the extent of injury

Can be obtained quickly using multi-detector high-resolution scanners

Can be visualized using brain or bone contrast windows and reconstructed into 3D CT datasets in order to demonstrate bony injury and intracranial pathology

FIGURE 3D CT reconstruction.This patient sustained injuryfollowing a road traffic accident.The reconstruction allowedoperative planning of the cranialand facial fractures.

Thanks to J. P. Coles and D. K. Menon

• Limitation

Delivers high dose of radiation

Beam-hardening artefacts

Limited resolution can result in partial volume errors

Limited availability of scanners compared to traditional radiographic equipment and ultrasound

FIGURE Beam-hardening artifact caused by unusually severe hardening of x-rays passing though thick bone.

Goldman, Lee W. "Principles of CT: radiation dose and image quality." Journal of nuclear medicine technology 35.4 (2007): 213-225.

• Imaging modality based on the nuclear phenomena of magnetic

resonance

• Produced using powerful static magnetic fields, which are measured in

units termed Tesla (T), and intermittent oscillating radiofrequency

electromagnetic fields that elicit signals from the nuclei of certain atoms

1 T = 10,000 G (Gauss)

The magnetic field strength at the surface of the Earth = 0.5 ~ 1.5 G

Field strengths used in clinical MRI = 1 ~ 3 T

• By employing a variety of different MR sequences, the extent of injury

can be demonstrated with high resolution

On a T1-weighted images, fat appear bright while water- and fluid-

containing tissues appears dark

On a T2-weighted scan, water and fluid are bright while fat is dark

• Advantages

Provide high spatial resolution (the ability to distinguish two separate

structures at a small distance from each other) and contrast resolution

(the ability to distinguish the differences between two similar but not

identical tissues)

• Limitation

Relatively long image acquisition time, which can be particularly

challenging in paediatric patients

Projectile risks from ferromagnetic objects (e.g. oxygen cylinders,

identification badges, paging devices

Implanted devices can be disastrous if the ferromagnetic implant (e.g.

cardiac pacemaker) is large or in a critical location

Monitoring devices may dysfunction due to magnetic fields

• Functional MRI (fMRI) can be used to measure neural activity by the measurement of changes in blood oxygenation using the blood oxygen level-dependent (BOLD) signal

Neural activation results in an increase in regional blood flow and influx of oxygenated blood

• Partial volume effect

BOLD signal occurs in gray matter where synapses and dendrites are. Therefore if voxel includes white matter (e.g.axons), or CSF, or spaces outside the brain, can occur distortion

fMRI data can be difficult to interpret in disease states

• Positron emission tomography (PET) is a nuclear medicine functional imaging technique that is used to observe metabolic processes in the body.

• Principle

1) The nucleus of the radioisotope emits a positron (positive electron).

2) This collides with an electron in the tissue and in the process converts mass to energy in the form of two photons.

3) The PET camera uses scintillation crystals placed around the subject to detect these photons.

4) The crystals absorb the photons, producing light that is converted into an electrical signal.

• Single-photon emission computed tomography (SPECT, or less commonly, SPET) is a type of nuclear imaging test that shows how blood flows to tissues and organs.

• Principle

1) Radiolabeled (emits Gamma rays) chemical tracer is injected into the blood steam

2) Radioactive Tracers; Iodine 123, Technetium 99, Xenon 133, Thallium 201, and Fluorine 18

3) Gamma rays are emitted by the tracer, which are detected by the scanner

4) Scanner collects emitted gamma rays and translates them as an image

FIGURE Schematic principle of SPECT

FIGURE A SPECT scan of a patient with uncontrolled complex partial seizures. The temporal lobe on the left side of the brain shows less blood flow than the right, confirming for the surgeon the nonfunctioning area of the brain causing seizures

• Monitoring (the repeated and consistent measurement of biological variables) for

patients with traumatic brain injury (TBI) can be crucial

1/3 of patients with TBI show clinical deterioration which is dangerous, sometimes life-

threatening, and associated with worse long-term outcomes

In deeply sedated patients, instrumental monitoring can become the predominant source of

information

• Current practice recommends the simultaneous acquisition of

multiple parameter in neurointensive care

All available commercial monitors offer multiple parameters to

be registered and displayed simultaneously

Intracranial disturbances are better treated when their causes

are identified, and the most productive way of achieving this

goal is performed by integrating multiple sources of information

Dept. of CriticalDept. of Neurosurgery, Addenbrooke’s Hospital (University of Cambridge,

UK) Care Medicine, The Hospital for Sick Children (University of Toronto, Canada)

• The purpose of multimodality monitoring

– To continuously measure relevant biological variable regarding condition of patient’s brain

– To detect possible causes of the patient’s symptom

– To identify trends in the clinical evolution of disease

– To contribute to the assessment of prognosis

• Clues for stabilizing the patient’s condition!

• Monitoring needs a device, placed inside the head

Subdural screw

used if monitoring needs to be done right away

catheter is inserted through the brain into the lateral

ventricle

Epidural sensor

less invasive than other methods

• Alternative methods have therefore been sought

with which ICP can be estimated non-invasively

Otoacoustic emission

acoustic phenomenon allow assessment of the

pressure of the peri- and endo-lymph, and

consequently, of ICP

Ocular measurements

the space between the optic nerve and its sheath is

consequently filled with cerebrospinal fluid whose

pressure is equal to intracranial pressure

[1] Monro A. (1783). “Observations on the structure and function of the nervous system.”, Edinburgh: Creech & Johnson.

[2] Kelly G. (1824). “Appearances observed in the dissection of two individuals; death from cold and congestion of the brain.”, Trans. Med.

ChirSciEdinb1: 84-169

• Brain weigh approx. 1400g

– Intracranial compartment 83% + Cerebrospinal fluid (CSF) 11% + Cerebral blood volume (CBV) 6%

• Brain floats in the fluid, losing its relative weight according to Archimedes’ law (Any floating object displaces its own weight of fluid) – In fact, there are not enough volume of CSF to make such a mechanism effective

• Due to continuous fluid environment, all gradients of the ICP within the CNS are equilibrated according to Pascal’s law (the principle of transmission of fluid-pressure)

• According to the Pascal, pressure exerted anywhere in a confined incompressible fluid is transmitted equally in all directions throughout the fluid such that the pressure ratio (initial difference) remains the same

( )P g h

• Raw physiological signals can be useful but often carry hidden

information (Sörnmo, Leif, Academic Press, 2005)

• The critical level of ICP is controversial

• ICP at 20mmHg or less was not shown to be superior to care based on

imaging and clinical examination (Chesnut, Randall M., et al. New England Journal of Medicine, 2012)

Mean ICP is not very useful for predicting neurological outcome

Figure 1 Cumulative Survival Rate According to Study Group

Parenchymal

compartment

CSF space

Vascular

compartment

• The morphology of ICP waveform holds information about the

outcome of head injury patients (Scalzo, Fabien, et al. Artificial intelligence in medicine, 2012)

development of intracranial hypertension, craniospinal compliance

• Extraction of morphological features may provide insight to

monitor and to understand ICP with the ultimate goal of

improving the treatment (Anile, Carmelo, et al. Interdisciplinary Neurosurgery, 2014)

• Arterial Blood Pressure (ABP)

Basic hemodynamic index often utilized to guide therapeutic interventions,

especially in critically ill patients

Hypotension, hypertension, bradycardia and tachycardia are all critical for

the prognosis of TBI

However, the measured ABP signals are often unstable and riddled with

signal artifact

Clinical parameters derived from artifact-contaminated signals can easily

induce erroneous recognition of clinical events; clinicians may either apply

excessively aggressive therapy or avoid necessary treatment

The continuous monitoring of physiological signals is a hallmark of critical

care units, problems due to poor signal quality are the most severe in

critical care units, which manage TBI cases

McGhee, Beate H., and Elizabeth J. Bridges. Critical Care Nurse22.2 (2002): 60-79.

Hypotension

Hypertension

Bradycardia

Tachycardia

• Indirect measurement

Manometry

Measured indirectly with a cuff over the brachial artery or the femoral artery

Ultrasound

Measure changes in blood velocity in the large arteries

The PWV values are used to convert distension waveforms to pressure waveforms with good correlation to reference pressure traces

• Direct measurement

Most accurate and real-time method of monitoring blood pressure

Cannula

Hydraulically coupled via a column of saline to a diaphragm and transducer assembly

Transducer

Changes in pressure produce very small movements of the diaphragm that in turn alters the length of the strain gauge wire and its electrical resistance

• Blood pressure waveform = Pressure wave by left ventricle + reflected wave(form termination and bifurcation in vascular bed)

• Stiffer arteries (compliance ↓) Pressure wave speed ↑ → earlier return of

reflected wave

• Risk factors with arterial compliance Increased central pulse pressure raise stroke risk Decreased coronary artery PP in diastole may

results in myocardial ischemia Increased left ventricular load (LV) may lead LV

hypertrophy risk

• The waveform of ABP pulses is affected by thechanges in the cerebrovascular resistance

FIGURE Pulse wave reflection (Hahn, J. et al., 2008)

• ECG

Electrical currents are generated from the propagating action potentials

Electrocardiogram (ECG) is used to record the potential difference

between two points on the skin surface

ECG enables monitoring of cardiac activity

Signal interpretation

P wave – depolarization of the atria, signal from SA node

QRS complex – ventricular depolarization and atrial repolarization

T wave – ventricular repolarizationFig. Typical ECG signal morphology

P-Q interval – conduction time from atria, AV node to the fibers remaining in the conduction system

S-T segment – time when both ventricles are completely depolarized

Q-T interval – Time for both ventricular depolarization and repolarization to occur

Andersson, David. "Real-time ECG for objective stress level measurement." (2017).

Martinez, R., et al. Computer Methods and Programs in Biomedicine 148 (2017): 81-90.Tarvainen, Mika P., et al. Computer methods and programs in biomedicine 113.1 (2014): 210-220.

• HRV

Beat to beat alterations in heart rate

Evaluation of ANS function; recordings of timing and

strength of each heartbeat

1) Sympathetic – Heart rate up / HRV down

2) Parasympathetic – Heart rate down / HRV up

A result of ANS regulation of the sinoatrial (SA) node

Frequency domain interpretation

1) High frequency (0.15 ~ 0.4 Hz) – parasympathetic nervous activity

2) Low frequency (0.04 ~ 0.15Hz) – Both of sympathetic and parasympathetic origin,

Normalized value of the LF component could be used to assess

sympathetic efferent activity

HRV analysis in stress

1) Low HRV: related to abnormal physiological condition, mental stress

2) High HRV: good adaptability of ANS

• ElectroEncephaloGram (EEG) =

Electro (electrical) + Encephalo (brain) + Gram (Graph)

• Electrophysiological monitoring

Capturing electrical potential differences on the scalp surface → electrical activity of the brain

• Summation of the synchronous activity of cortical neurons

Neural activity is conducted through the brain volume to the scalp

and sensors by Volume conductance

Generalized, Large-scale neural activity of cerebral cortex

Triggered by external (e.g. perception), internal (e.g. sleep) events

• Neural mechanism

Pyramidal cells, stellate (granule) cells

largest contributors of the EEG signal is pyramidal cells because it is

radially oriented in the cortex

• EEG device

Electrodes to scalp, low-resistance connection

Amplifiers, recording devices

Voltage fluctuations (tens of microvolts) based on

the reference electrical cap (e.g. Cz)

• Pros and Cons Advantage of fully noninvasive high temporal

resolution

Disadvantage of poor signal-to-noise ratio, low

spatial resolution

• Types of EEG

Gel EEG uses a gel to lower the resistance to get

a more accurate signal when measuring

Dry EEG has the advantage of being practical

enough to be used in real products

• Categorization of rhythms based on frequency

Beta: Greater than 14Hz, activated cortex

Alpha: 8-13 Hz, quiet, waking state

Theta: 4-7 Hz, some sleep states

Delta: Less than 4Hz, deep sleep

• According to central pacemaker hypothesis, thalamus is the starting point of neuronal oscillation mechanism causing synchronized high EEG amplitude sleep state EEG signal

• EEG can discriminate sleep stage using brain rhythms

• This characteristic of EEG enables sleep studies, especially distinguishing REM and non-REM sleep stage

Dimitriadis, Stavros I. "A high performing EEG approach for the automated scoring of the sleep stages of neonates." (2017).

• Near-InfraRed Spectroscopy (NIRS) = Spectro (spectrum) + scopy (observation/inspection)

• Light attenuation monitoring Measuring tissue absorbance of light at several

wavelengths (spectral region from 700-1100nm) Capable of deeper penetration of several centimeters Indirect, optical neuroimaging method which monitors

hemodynamic response to brain activation.

• fNIRS Capturing changes of attenuated near-infrared light

(owing to scattering or absorption) → fNIRS Changes in concentration between oxyhemoglobin

(HbO2) and De-oxyhemoglobin (Hb) during localneural activity

HbO2 differs in parts of it’s light absorption pattern from Hb, and thus in their apparent opticalspectrum

Nervous system was associated with changes in the optical properties of light Strong correlation with PET measures of changes in regional CBF (rCBF) and fMRI BOLD signals

• NIRS components

Light-Emitting Diode (LED)

Photo detector

• Hemodynamic response affecting factors Chromophore concentration affects

attenuated light levels

Biological tissue transparency, absorption

capacity of the diverse chromophores in

optical pigments (e.g. melanin, myoglobin or

hemoglobin)

• Absorption spectrum in NIR window Absorption spectra difference of HbO2 and

Hb at 700-900 (optical window) allow

spectroscopy methods to assess their

respective concentrations

Beyond 900nm, the majority of the photons

are absorbed by the water, making

measurement difficult

• NIRS depth determinants

Wavelength, Inter-optode distance (IOD)

• NIRS depth problem

1. Impossible to detect deep brain structure using NIRS

The greater the source-detector distance, the deeper thepenetration however, a greater distance can also to a lowerintensity of light captured by the detector

2. NIRS disabled

Dark skin and very dark hair can absorb most wavelengths,hence a shorter distance between light source and detectorwould be recommended, which increases the intensity of thewavelength

• Recommended NIRS depth The ideal distance between source and detector depends on the capillary depth and

demographic variables of subjects being studied

• The total cost of any system is likely to be high because of the initial investment and

the human work implied in maintaining and implementing it

• In fact, technology is advancing, new ‘toys’ are on the horizon and a conclusive

statement about the utility of multimodality monitoring may be premature

• However, even as things stand, multimodality

monitoring has improved our detection and

interpretation of pathophysiology at the bed side,

and is increasingly seen as a basis for selecting and

implementing therapies

definition - kbso · • definition creative application of scientific principles to design or...

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