Cataract Extraction Units,Cataract Extraction Units,PhacoemulsificationPhacoemulsification

PurposePurpose

Phacoemulsification systems are used to Phacoemulsification systems are used to break up break up and remove the cataractous lenses and remove the cataractous lenses of eyes.of eyes.

A cataract is a fogging of the normallyA cataract is a fogging of the normally transparent lens thattransparent lens that inhibits theinhibits the transmission of light to the retina, causingtransmission of light to the retina, causing a a painless blurring of visionpainless blurring of vision

Cataracts are caused byCataracts are caused by:: changes in the chemical composition of the lens changes in the chemical composition of the lens

associatedassociated with many factors: with many factors:– environment, environment, – drugs,drugs,– SystemicSystemic diseases, diseases, – age, age, – traumatic eye injuries, traumatic eye injuries, – Certain Certain diseases of the eye, diseases of the eye, – and genetic or birth defectsand genetic or birth defects

If cataracts are not treated, progressive visual loss, leading to significantly If cataracts are not treated, progressive visual loss, leading to significantly impaired sight, can occur.impaired sight, can occur.

PhacoemulsificationPhacoemulsification

widely used by ophthalmic surgeons widely used by ophthalmic surgeons because the entire procedure — cataract because the entire procedure — cataract extraction and implantation of an intraocular extraction and implantation of an intraocular lens (IOL) —can be done througha single lens (IOL) —can be done througha single small incisionthat may help control surgically small incisionthat may help control surgically inducedinduced astigmatism, quicken visualastigmatism, quicken visual rehabilitation, and decrease surgical rehabilitation, and decrease surgical complications.complications.

Principles of operationPrinciples of operation

Phacoemulsification is one type of Phacoemulsification is one type of extracapsular cataract extraction, a extracapsular cataract extraction, a procedure that removes the lens nucleus, procedure that removes the lens nucleus, surrounding cortex, and the enclosing surrounding cortex, and the enclosing anterior capsule; the zonules and posterior anterior capsule; the zonules and posterior capsule are left intact to help support an capsule are left intact to help support an IOL implant During a phacoemulsification IOL implant During a phacoemulsification procedure, the surgeon performs several procedure, the surgeon performs several steps with the aid of an operatingsteps with the aid of an operating microscopemicroscope

A 2.8 to 3.5 mm incision is made to gain A 2.8 to 3.5 mm incision is made to gain access to the eye’s anterior chamber. A access to the eye’s anterior chamber. A viscoelastic material is then infused to viscoelastic material is then infused to deepen the anterior chamber and protect deepen the anterior chamber and protect the corneal endothelium.the corneal endothelium.

the surgeon inserts a phaco-emulsification probe, the surgeon inserts a phaco-emulsification probe, which consists of a hollow, cylindrical tip surrounded which consists of a hollow, cylindrical tip surrounded by an irrigation sleeve. by an irrigation sleeve.

WhenWhen electrically activated, the probe tip oscillates electrically activated, the probe tip oscillates rapidly,creating ultrasonic waves that cut tissue.rapidly,creating ultrasonic waves that cut tissue.

The surgeonThe surgeon emulsifies the cataractous lens using emulsifies the cataractous lens using shaving or scoopingshaving or scooping motions of the probe tip. motions of the probe tip.

The lens fragments areThe lens fragments are then aspirated from the eye then aspirated from the eye through the hollow tip of the phacoemulsifier. through the hollow tip of the phacoemulsifier. Remaining cortex is aspirated via the I/A Remaining cortex is aspirated via the I/A attachment. Either a polymethyl methacrylateattachment. Either a polymethyl methacrylate (PMMA) or a foldable silicone IOL is inserted (PMMA) or a foldable silicone IOL is inserted through the incision and into the bag of the capsule, through the incision and into the bag of the capsule, which is then sutured; however, self-sealing, which is then sutured; however, self-sealing, sutureless cornealsutureless corneal incisions are becoming more incisions are becoming more widely used for phacoemulsificationwidely used for phacoemulsification procedures.procedures.

Typical phacoemulsification systems Typical phacoemulsification systems integrate intointegrate into a single handpiece the I/A and a single handpiece the I/A and

US capabilities neededUS capabilities needed to break up andto break up and remove a cataractous lens from theremove a cataractous lens from the eye. eye.

The surgeon typically activates theseThe surgeon typically activates these capabilities by depressing a single capabilities by depressing a single

footpedal.footpedal.

A bottle of balanced salt A bottle of balanced salt solution is used as thesolution is used as theirrigant; mounted on an irrigant; mounted on an

adjustable intravenous (IV)adjustable intravenous (IV)pole, its pressure head can be pole, its pressure head can be

controlled by adjustingcontrolled by adjustingits height.its height.

Centrifuges, TabletopCentrifuges, Tabletop

PurposePurpose

Centrifuges apply centrifugal force toCentrifuges apply centrifugal force to separate suspendedseparate suspended particles from a liquid particles from a liquid or to separate liquids ofor to separate liquids of different densities. different densities. These liquids can be bodily fluidsThese liquids can be bodily fluids (e.g., (e.g., blood, serum, urine), commercial eagents, blood, serum, urine), commercial eagents, or or mixtures of the two with other additives.mixtures of the two with other additives.

In the clinicalIn the clinical laboratory, centrifugation is one laboratory, centrifugation is one of several sampleof several sample preparation steps preparation steps commonly required before measuringcommonly required before measuring analytes in a patient sample. analytes in a patient sample.

By creating forcesBy creating forces many times greater than many times greater than gravity, centrifuges cangravity, centrifuges can greatly accelerate greatly accelerate separations that occur naturally asseparations that occur naturally as a result a result of differences in density.of differences in density.

Centrifuges, Blood BankCentrifuges, Blood Bank Centrifuges, Cell WashingCentrifuges, Cell Washing Centrifuges, CytologicalCentrifuges, Cytological Centrifuges, FloorCentrifuges, Floor Centrifuges, MicrohematocritCentrifuges, Microhematocrit MicrocentrifugesMicrocentrifuges UltracentrifugesUltracentrifuges

TThree general typeshree general types

the low-speed centrifuge,the low-speed centrifuge, the high-speed centrifuge,the high-speed centrifuge, and the ultracentrifuge.and the ultracentrifuge.

the low-speed centrifuge,the low-speed centrifuge,

– general operating general operating range of up to 10,000 rpmrange of up to 10,000 rpm – Available in nonrefrigerated or refrigerated Available in nonrefrigerated or refrigerated

versions, low-speed units are used primarilyversions, low-speed units are used primarily to to centrifuge red blood cells or bulky precipitates; centrifuge red blood cells or bulky precipitates; they cannot reach sufficient speed to they cannot reach sufficient speed to adequately separate ultrasmall particles (e.g., adequately separate ultrasmall particles (e.g., viruses, DNA) or macromolecules or to perform viruses, DNA) or macromolecules or to perform density gradient centrifugation.density gradient centrifugation.

High-speed tabletop centrifugesHigh-speed tabletop centrifuges

operate at 12,000 to 25,000 rpm, are used operate at 12,000 to 25,000 rpm, are used for most preparative applications, and some for most preparative applications, and some are refrigerated to cool the rotorare refrigerated to cool the rotor chamber. chamber.

UltracentrifugesUltracentrifuges

used for high-resolution separationused for high-resolution separation of subcellular of subcellular components, have a general operatingrange of components, have a general operatingrange of 30,000 to 120,000 rpm, with centrifugal forces of 30,000 to 120,000 rpm, with centrifugal forces of up to 700,000 g, where g is the standard up to 700,000 g, where g is the standard acceleration of gravity. Ultracentrifuges must be acceleration of gravity. Ultracentrifuges must be refrigeratedrefrigerated because air friction created at high because air friction created at high speeds generates heat that could decompose speeds generates heat that could decompose the proteins,the proteins, viruses, or other components being viruses, or other components being centrifuged. centrifuged.

UltracentrifugesUltracentrifuges are special-purpose floor units are special-purpose floor units that are typically used in research laboratories.that are typically used in research laboratories.

Principles of operationPrinciples of operation

CentrifugationCentrifugation– Centrifugation is based on the fact that an object Centrifugation is based on the fact that an object

moving in a circular path at a steady angular moving in a circular path at a steady angular velocity is subjected to an outwardly directed velocity is subjected to an outwardly directed force. force.

– The magnitudeThe magnitude of this force depends on both the of this force depends on both the rotor radius and the speed squared. rotor radius and the speed squared.

– This force is called the relative centrifugal force This force is called the relative centrifugal force or relative centrifugal field (RCF).or relative centrifugal field (RCF).

– It isIt is expressed as a multiple of g, the standard expressed as a multiple of g, the standard acceleration acceleration of gravity (e.g., 13,000 g).of gravity (e.g., 13,000 g).

Centrifuge componentsCentrifuge components

The basic components of a tabletop The basic components of a tabletop centrifuge includecentrifuge include::– an electric motor, a shaft and rotor heads (often an electric motor, a shaft and rotor heads (often

interchangeable) on which the centrifuge head interchangeable) on which the centrifuge head turns,and a motor drive assembly. If the turns,and a motor drive assembly. If the centrifuge is refrigerated,centrifuge is refrigerated, a compressor and a compressor and associated components are included. The entire associated components are included. The entire system is housed within a chamber.system is housed within a chamber.

Incubators, InfantIncubators, Infant

PurposePurpose– An infant incubator provides a closed, controlled An infant incubator provides a closed, controlled

environmentenvironment that warms an infant by circulating that warms an infant by circulating heated air over the skin. The heat is then heated air over the skin. The heat is then absorbed into the bodyabsorbed into the body by tissue conduction by tissue conduction and blood convectionand blood convection

At birth, an infant’s core and skin At birth, an infant’s core and skin temperatures tend to drop temperatures tend to drop significantly because of significantly because of – heat loss from conductionheat loss from conduction (heat loss to (heat loss to

cooler surfaces in direct contact with thecooler surfaces in direct contact with the infant), infant),

– convection (heat loss to air moving past convection (heat loss to air moving past thethe infant), infant),

– radiation (heat loss to cooler objects not radiation (heat loss to cooler objects not in directin direct contact with the infant), contact with the infant),

– and water evaporation (heat lossand water evaporation (heat loss from from the infant’s lungs and skin surface).the infant’s lungs and skin surface).

Whereas term neonates naturally regulate Whereas term neonates naturally regulate their body temperature to some extent, their body temperature to some extent, premature infants have premature infants have – thinner skin, which allows surface blood thinner skin, which allows surface blood

vessels to more readily lose heat to the vessels to more readily lose heat to the environment; environment;

– a large ratio of surface area to volume, a large ratio of surface area to volume, resulting in greater heat losses from radiation resulting in greater heat losses from radiation and convection;and convection;

– and almost no subcutaneous fat toand almost no subcutaneous fat to either either metabolize into heat or act as an insulator.metabolize into heat or act as an insulator.

Prolonged cold stress in Prolonged cold stress in neonates can cause oxygenneonates can cause oxygendeprivation, hypoglycemia, deprivation, hypoglycemia,

metabolic acidosis, andmetabolic acidosis, andrapid depletion of glycogen rapid depletion of glycogen stores. Therefore, energystores. Therefore, energyconservation provided by conservation provided by thermal support is critical.thermal support is critical.

Principles of operationPrinciples of operation

The neonate lies on a mattress in the infant The neonate lies on a mattress in the infant compartment,compartment, which is enclosed by a clear plastic which is enclosed by a clear plastic hood.hood.

Most incubators warm the infant by a forced or Most incubators warm the infant by a forced or natural flow of heated airnatural flow of heated air

Heating and humidification systems are located Heating and humidification systems are located beneathbeneath the infant compartment. A fan or natural the infant compartment. A fan or natural flowflow circulates air past the heater and the circulates air past the heater and the temperature measuring device, over a water temperature measuring device, over a water reservoir used to humidifyreservoir used to humidify the air (if desired), and the air (if desired), and up into the infant up into the infant compartmentcompartment

Oximeters, PulseOximeters, Pulse

PurposePurpose– Pulse oximeters noninvasively monitor the Pulse oximeters noninvasively monitor the

oxygen saturation (expressed as a oxygen saturation (expressed as a percentage or decimal) ofpercentage or decimal) of arterialarterial hemoglobin by measuring lighthemoglobin by measuring light absorbanceabsorbance changes resulting from arterial blood flow changes resulting from arterial blood flow pulsations.pulsations.

Principles of operationPrinciples of operation

Pulse oximeters provide a Pulse oximeters provide a spectrophotometric assessmentspectrophotometric assessment of of hemoglobin oxygenation (SpO2) by hemoglobin oxygenation (SpO2) by measuringmeasuring light transmitted through a light transmitted through a capillary bed, synchronized with the pulse. capillary bed, synchronized with the pulse. The detection systemThe detection system consists of single-consists of single-wavelength light-emitting diodeswavelength light-emitting diodes (LEDs) and (LEDs) and microprocessors.microprocessors.

The pulse oximeter probe is applied to an area The pulse oximeter probe is applied to an area of the body such as a finger, a toe, or an ear. of the body such as a finger, a toe, or an ear.

Two wavelengthsTwo wavelengths of light (e.g., 660 nm [red] and of light (e.g., 660 nm [red] and 930 nm [infrared]) are transmitted by the probe 930 nm [infrared]) are transmitted by the probe through the skin and are differentiallythrough the skin and are differentially absorbed absorbed by oxyhemoglobin, which is red and absorbs by oxyhemoglobin, which is red and absorbs infrared light, and deoxyhemoglobin, which is infrared light, and deoxyhemoglobin, which is blue and absorbs red light. blue and absorbs red light.

The ratio of red to infraredThe ratio of red to infrared light is used to derive light is used to derive oxygen saturation. oxygen saturation.

The photo-detectorThe photo-detector on the other side of the on the other side of the tissuetissue converts theconverts the transmitted light into transmitted light into electrical signalselectrical signals proportional toproportional to the absorbance the absorbance

Nebulizers, Heated; UltrasonicNebulizers, Heated; Ultrasonic

PurposePurpose– Nebulizers provide aerosol treatment and/or Nebulizers provide aerosol treatment and/or

medicinemedicine to patients with certain respiratory to patients with certain respiratory disordersdisorders

– Nebulizer therapy is particularly effective in Nebulizer therapy is particularly effective in treating conditionstreating conditions such as cystic fibrosis, such as cystic fibrosis, emphysema, croup, bronchitis,emphysema, croup, bronchitis, and severe and severe asthmaasthma

Most nebulizers are either pneumatic Most nebulizers are either pneumatic (driven by compressed air) or (driven by compressed air) or ultrasonic. Both types provide anultrasonic. Both types provide an effective aerosol mist for depositing effective aerosol mist for depositing medication intomedication into the lungs.the lungs.

Heated nebulizers provide warmed Heated nebulizers provide warmed aerosol mist to spontaneously aerosol mist to spontaneously breathing patients being treated withbreathing patients being treated with oxygen or compressed air, which, oxygen or compressed air, which, delivered cold, candelivered cold, can cause severe cause severe bronchospasm in patientsbronchospasm in patients with with hyperac-tivehyperac-tive airways (asthma airways (asthma patients).patients).

Principles of operationPrinciples of operation

Heated nebulizersHeated nebulizers– A heated nebulizer generally consists ofA heated nebulizer generally consists of

a reservoir,a reservoir, a heating element, a heating element, a compressor, a compressor, and a nebulizer jet.and a nebulizer jet.

Ultrasonic nebulizersUltrasonic nebulizers

An ultrasonic nebulizer consists of several An ultrasonic nebulizer consists of several compo-nents:compo-nents:– an electronic oscillator, an electronic oscillator, – an ultrasound transduceran ultrasound transducer (piezoelectric(piezoelectric crystal),crystal),– a coupling basin,a coupling basin,– aa nebulizer chamber (also called a cup), nebulizer chamber (also called a cup), – and a fanand a fan

To begin nebulization, a high-frequencyTo begin nebulization, a high-frequency (typically 1 to 2 MHz) electrical voltage(typically 1 to 2 MHz) electrical voltage

is applied to a piezoelectricis applied to a piezoelectric crystalcrystal within the oscillator circuit, whichwithin the oscillator circuit, which

changes thechanges the applied electrical signalapplied electrical signal into mechanical vibrations.into mechanical vibrations.

These vibrations, in turn, produce 1 to 2 MHz These vibrations, in turn, produce 1 to 2 MHz soundsound waves in the coupling basin. waves in the coupling basin.

The couplerThe coupler (water or(water or saline) transmits the sound saline) transmits the sound waves to thewaves to the solution insolution in the nebulizer chamber. the nebulizer chamber.

The ultrasonicThe ultrasonic waves inducewaves induce cavitation (formation cavitation (formation of partialof partial vacuums in a liquid),vacuums in a liquid), which causes which causes

bubbles to formbubbles to form when the low-pressurewhen the low-pressure phase of phase of the wave is lowerthe wave is lower than the liquid’s vaporthan the liquid’s vapor pressure. pressure.

When the soundWhen the sound waves reach the liquid/airwaves reach the liquid/air interface, the liquidinterface, the liquid forms a geyser and disperses forms a geyser and disperses

intointo an aerosol mist an aerosol mist

During drug therapy, During drug therapy, medication cups hold smallmedication cups hold small

quantities of medication such asquantities of medication such as albuterol;albuterol; the water in thethe water in the chamber serves only as achamber serves only as a

medium tomedium to transmit the transmit the ultrasonic energyultrasonic energy

The size of the mist particles is The size of the mist particles is determined primarilydetermined primarily by theby the

vibrating frequency; the highervibrating frequency; the higher the frequency, the smaller thethe frequency, the smaller the

particles. particles. UltrasonicUltrasonic nebulizers produce nebulizers produce particles in the range ofparticles in the range of 0.5 to 0.5 to

35 mm;35 mm;