VENTILATOR GRAPHICSVENTILATOR GRAPHICS

LOOPS AND CURVESLOOPS AND CURVES

dr.r.selvakumardr.r.selvakumar

Some definitions…Some definitions…

•Inspiratory flow time: beginning of flow to Inspiratory flow time: beginning of flow to end of flow during inspirationend of flow during inspiration

•Inspiratory pause time:time in inspiration whereInspiratory pause time:time in inspiration where flow is zeroflow is zero

•Inspiratory phase time: Insp.flow time+insp.pauseInspiratory phase time: Insp.flow time+insp.pause timetime

Expiratory flow time,Exp.pause timeExpiratory flow time,Exp.pause timeExp.phase timeExp.phase time

Inspiratory flow rate: rate at which gas flows Inspiratory flow rate: rate at which gas flows into the pt expressed as volume per unit of timeinto the pt expressed as volume per unit of time

Peak pressure: max. pressure during the Peak pressure: max. pressure during the insp.phase timeinsp.phase time

Plateau pressure: resting pressure during Plateau pressure: resting pressure during the insp.pausethe insp.pause

Some definitions…contdSome definitions…contd

•Resistance: ratio of the change in drivingResistance: ratio of the change in drivingpressure to the change in flow rate.cmH2O/L/secpressure to the change in flow rate.cmH2O/L/sec

•Compliance: ratio of a change in volume to a Compliance: ratio of a change in volume to a change in pressurechange in pressure

Some definitions…contdSome definitions…contd

Exp.phase time

flow pause

Insp phase time flow

pause

Flow 0

hold

volume

0

pressure

0

peak plateau

AIRWAY PRESSURE WAVE FORM

normal

High airway resistance

40

20

peakplateau

Volume cont.ventilation

Press.cont.ventilation

LOOPS:LOOPS:

Dynamic relationship between two variablesDynamic relationship between two variableson a graphon a graph

pressure

VOlUMe

inspiration

exhalation

End inspiration

NORMAL P-V LOOPNORMAL P-V LOOP

FRC

inspiration

exhalation

Flow lpm

TV

NORMAL FLOW-VOLUME LOOPNORMAL FLOW-VOLUME LOOP

+30

CONTROLLED VENTILATIONCONTROLLED VENTILATION

- No ins.pause- No ins.pause

Double convexDouble convexBegins at zero volume and near zero pressureBegins at zero volume and near zero pressureIns. Slope – complianceIns. Slope – complianceEnd of insp- peak press and TV attainedEnd of insp- peak press and TV attained

P-V LOOPP-V LOOP

Peakpressure

TV

300

600

900

volumeNormal P-V loopNormal P-V loop

Normal flow-volume loopNormal flow-volume loop

Smoothly curved,rectangular insp.limbSmoothly curved,rectangular insp.limbUpper triangular exp.portionUpper triangular exp.portionApex – peak exp.flowApex – peak exp.flowSlope of exp.flow- reflects the resistanceSlope of exp.flow- reflects the resistanceAnd recoil pressure of the entire ventilatoryAnd recoil pressure of the entire ventilatory systemsystem

Cont.ventilation with PEEPCont.ventilation with PEEP

P-V loop shifts to the rightP-V loop shifts to the right Begins at the PEEP valueBegins at the PEEP value

volume

pressure

Insp.pause

Controlled ventilation with insp.pauseControlled ventilation with insp.pause

•After peak press. Is reached,there is a pauseAfter peak press. Is reached,there is a pause

•During pause,press. drops to a plateau levelDuring pause,press. drops to a plateau level

•Insp.volume will increase during insp.pauseInsp.volume will increase during insp.pause

SPONTANEOUS RESPIRATIONSPONTANEOUS RESPIRATION

starts at zerostarts at zeroinspiration- airway press is negative.inspiration- airway press is negative.loop moves on to left loop moves on to left End of insp- press. Becomes zeroEnd of insp- press. Becomes zeroExhalation-pree.becomes positive,volume dropsExhalation-pree.becomes positive,volume drops

volume

-10 10 20pressure

exhalaton

inspiration

30 lpm

600 volume

Normal F-V loop-spon.respirationNormal F-V loop-spon.respiration

exhalationinhalation

P-V loop –spon.breathing with PEEPP-V loop –spon.breathing with PEEP

F-V loop- lower flows during insp and expirationF-V loop- lower flows during insp and expiration

Spon.breath900ml

10

pressure

SPON.BREATH DURING CONT.VENTILATIONSPON.BREATH DURING CONT.VENTILATION

Spon.breath during cont.ventilationSpon.breath during cont.ventilation

If it occurs during expiration,the pressure dropsIf it occurs during expiration,the pressure dropsand volume increasesand volume increasesAs the pt exhales,press. increases briefly and As the pt exhales,press. increases briefly and volume dropsvolume drops

F-V Loop-spon.breath in cont.ventilationF-V Loop-spon.breath in cont.ventilation

Breath occurs during inspiration

Sudden increase in ins.flow and volumeSudden increase in ins.flow and volumeAs the breath is exhaled,flow & volume move As the breath is exhaled,flow & volume move towards zerotowards zero

30

600ml

Fighting with ventilatorFighting with ventilator

Inhalation at the beginning of ventilator insp.Inhalation at the beginning of ventilator insp.So loop moves to the left of the vertical axisSo loop moves to the left of the vertical axismarked decrease in compliancemarked decrease in compliance

OPEN LOOPOPEN LOOP

900ml

pressure

30 lpm

Open F-V loopOpen F-V loop

OPEN LOOPOPEN LOOP

A loop should return to its starting pointA loop should return to its starting pointGap between the end and starting pointsGap between the end and starting pointsExhaled volume is less than inhaled volumeExhaled volume is less than inhaled volume

Causes:Causes:uncuffed ETT,LMA,leakuncuffed ETT,LMA,leakPartial disconnectionPartial disconnectiontension pnemothoraxtension pnemothoraxextreme absorption of N2Oextreme absorption of N2O

30 lpm

600 ml

An open F-V loopAn open F-V loop

There is still exp.flow when the There is still exp.flow when the next insp. Is commencednext insp. Is commenced

COPDCOPD

OVERSHOOT LOOPOVERSHOOT LOOP

exhaled volume is more than the inspired volumeexhaled volume is more than the inspired volume

P-V loop in decreased complianceP-V loop in decreased compliance

Normal loop

Loop shiftedTo right and down

PEEP may restore the curve back towards leftPEEP may restore the curve back towards left

60 lpmF-V loop- decreased complianceF-V loop- decreased compliance

Flow will be increased during exhalation with a higher peak and steeper slope

500 ml

10 30

pressure

P-V loop – increased resistanceP-V loop – increased resistance

CHANGES IN RESISTANCE:CHANGES IN RESISTANCE:

Higher insp.pressure required to Higher insp.pressure required to deliver the given flowdeliver the given flow TV reducedTV reduced Curve shifted right and downCurve shifted right and down Large internal areaLarge internal area Loop may be open if air trappingLoop may be open if air trapping

P-V loop in emphysemaP-V loop in emphysema

No problem in inflating lungsNo problem in inflating lungsExhalation - press.drops with little Exhalation - press.drops with little change in volume until the end of exhalationchange in volume until the end of exhalationOpen loopOpen loop

F-V loop in emphysemaF-V loop in emphysema

Insp. Almost normalInsp. Almost normalSevere reduction in exp.flowSevere reduction in exp.flowLoop may be openLoop may be open

30 lpm

Fixed tracheal obsBoth are restricted

Extra thoracic obsIns.plateauNormal expiratoryflow

F-V LOOPS IN OBSTRUCTIVE PATHOLOGYF-V LOOPS IN OBSTRUCTIVE PATHOLOGY

airway collapse during exhalationairway collapse during exhalationNormal ins. flowNormal ins. flow

Intra thoracic obstructionIntra thoracic obstruction

RESTRICTIVE LUNG DISEASERESTRICTIVE LUNG DISEASE

increase in elastic recoil increase in elastic recoil associated with high exp.flow and associated with high exp.flow and deep descending flow deep descending flow As disease progresses, lung volume decreases As disease progresses, lung volume decreases And the loop becomes tall and narrowAnd the loop becomes tall and narrow

60 lpm

RESTRICTIVE DISEASERESTRICTIVE DISEASE

normal

One lung intubationDLT deeply placed

BALL VALVE OBSTRUCTIONBALL VALVE OBSTRUCTION

BALL VALVE OBSTRUCTIONBALL VALVE OBSTRUCTION

Tip of the tube impinging on the side wall of tracheaTip of the tube impinging on the side wall of tracheaPress. Rises rapidly with little increase in volumePress. Rises rapidly with little increase in volumeUntil press is sufficient to overcome the obstruction.Until press is sufficient to overcome the obstruction.The vol. Increases and press.drops.The vol. Increases and press.drops.If the press. drops low enough, there will beIf the press. drops low enough, there will beagain an obstruction to flow,creating anotheragain an obstruction to flow,creating anothernotch on the upswing of the loopnotch on the upswing of the loop