1

Monitoring of Ventilation and Air Leakage

during CPAP

Gerd Schmalisch

Clinic of Neonatology Charité-Universitätsmedizin Berlin

2

OutlineOutline

Ventilation and air leakage measurements during MV

Peculiarities of ventilation monitoring during CPAP

Theoretical background

Air leakages and volume correction

Clinical studies

Conclusions and outlook

3

Volume monitoring during MVVolume monitoring during MV

Humidifier

Exp

ira

tory

lim

b

Inspiratory limb

A

B

"Face out" body plethysmograph

C

Ventilator

T insp T exp

T insp

V - VLeak(%) =100

V

Displayed volume:

Vexp

Displayed air leakage:

4

Relationship between volume error and displayed leak during MVRelationship between volume error and displayed leak during MV

Babylog 8000

-40%

-35%

-30%

-25%

-20%

-15%

-10%

-5%

0%

5%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90%

Leak (%)

Vo

lum

e er

ror

(%)

RR=20/min

RR=30/min

RR=40/min

RR=50/min

RR=60/min

RR=70/min

Mahmoud R, et al. Acta Paediatr. 98 (2009) 1116-1122

5

Endotracheal tube leakage in newbornsEndotracheal tube leakage in newborns

Median ET leakage 24h before extubation (%)

Pe

rce

nta

ge

s

0%

10%

20%

30%

40%

50%

60%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Frequency distribution of ET leakage of 163 ventilated (>5h) newborns

No ET leakage:

79/163 (48%)

ET leakage < 20%:

125/163 (77%)

ET leakage >40%:

12/163 (7.4%)

Temporarily ET leakage >40% during MV

59/163 (36%)

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Peculiarities of ventilation monitoring during CPAPPeculiarities of ventilation monitoring during CPAP

Different aims of monitoring

Different patient interfaces

Much higher air leakages

Spontaneous breathing (breath detection)

Worse signal-to-noise ratio

No suitable equipment !

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Current ventilation monitoring during CPAPCurrent ventilation monitoring during CPAP

Indirect methods Breathing belts (inductive (RIP), capacitive) Transthoracic impedance Pressure capsules

Advantages: No influence on breathing (resistance, dead space) Measurement of thoraco-abdominal synchrony

Disadvantage: No reliable measurement of VT, V’E,… No information about air leakages

8

Direct ventilatory measurements during CPAPDirect ventilatory measurements during CPAP

Interface

Oro- /nasopharyngeal tube Endotracheal tube Face mask

Binasal prongsHead box

Benveniste valve Infant Flow™ nCPAP System

FlowsensorAir

Flow driver

0.21 - 1.0

Flow

FiO2

P(t)

CPAP valve

O2

Humidifier

To the patient interface

V’(t))

Flowsensor1

Air

Flow driver

0.21 - 1.0

Flow

FiO2

P(t)

O2

Humidifier

Binasal prongs

V’1(t))

CPAP valve

Flowsensor2

V’2(t))

B

Flowsensor

Air

Flow driver

0.21 - 1.0

Flow

FiO2

O2

Humidifier

Defined leakage

V’(t)) E.g. Benveniste valve

P(t)

Schmalisch G. Yearbook equipments and technology in NIPPV - 2009

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Ventilation and leak flowVentilation and leak flow

How we can separate breathing flow and leakage flow?

(Prerequisite for breath detection and ventilation measurements)

Breathing flow

-2

0

2

4

0 4 8 12 16 20Time (s)

Flo

w (

L/m

in)

Leakage flow

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Bubble CPAP and variable leak flowBubble CPAP and variable leak flow

Under this conditions is the separation of breathing flow and leakage flow is a big challenge!

Flo

w (

L/m

in)

-4

0

4

8

0 4 8 12 16

20Time (s)

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Quantification of the air leakage - 1Quantification of the air leakage - 1A

ir le

ak (

%)

. .VLeak = VE

0%

50%

100%

150%

200%

250%

0 1 2 3 4 5 6 7 8 9

VLeak = max VCPAP

. .

Mea

surin

g ra

nge

of

conv

entio

nal v

entil

ator

s

. .

insp exp

insp

V - VLeak(%) =100

V

insp insp exp

100

T /(T T )

Schmalisch G. Year book of NIPPV 2009

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Quantification of the air leakage - 2Quantification of the air leakage - 2A

ir le

ak (

%)

Leak flow (L/min)

0%

20%

40%

60%

80%

100%

120%

140%

0 200 400 600 800 1000 1200 1400

RR = 30/min

RR = 60/min

RR = 90/min

The quantification of air leakages by the leak flow is more informative than by the currently use of percentages.

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Relationship between air leakage and volume error- modeling and in-vitro measurements -

Relationship between air leakage and volume error- modeling and in-vitro measurements -

Volume error

exE

in exCPAP

in

in ex

TVLeak

T Tmax VV 100

T100 Leak

T T

Leak100

200 Leak

V`E - measured minute ventilation

maxV‘CPAP - maximal CPAP flow

Tin/Tex - inspiratory/expiratory time

Leakmeasured (%)

Err

or o

f the

dis

play

ed ti

dal v

olum

e (

%)

-90%

-80%

-70%

-60%

-50%

-40%

-30%

-20%

-10%

0%0 10 20 30 40 50 60 70 80 90 100

In-vitro measurementsCalculated by modeling

Schmalisch G, et al. Med. Eng Phys. 31 (2009) 124-130 Fischer HS,, et al. Physiol. Meas. 29 (2008) 95-107

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Volume correction during CPAP- in vitro study -

Volume correction during CPAP- in vitro study -

Leakmeasured (%)

0 20 40 60 80 100

0

3

6

9

12

15

18

Tid

al v

olum

e V

T (

ml)

Corrected VT

MeasuredVT

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Clinical applications – 1Hückstädt T et al. Intens. Care Med. 29 (2003) 1134-1140Clinical applications – 1Hückstädt T et al. Intens. Care Med. 29 (2003) 1134-1140

Clinical cross-over study N=69 Comparison of Infant Flow system vs. Babylog 8000 by TB parameters Custom-made equipment (Flow-Through Technique) 49/69 (72%) infants excluded due to incompensable air leaks

-40% -20% 0% 20% 40% 60%

DCPAP= [kPa]

tPTEF:tE

Mean V’ex [L·min-1 kg-1]

Mean V’in [L·min-1 kg-1]

PTEF [L·min-1 kg-1]

PTIF [L·min-1 kg-1]

V’E [mL·min-1 kg-1]

VT [mL·kg-1]

RR [min-1]

**

**

*

*

*

Relative difference (%) Infant Flow System – Babylog 8000

* p < 0.05 ** p < 0.01

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Clinical applications – 2Fischer HS, et al. Intens. Care Med. (2009) (in press)Clinical applications – 2Fischer HS, et al. Intens. Care Med. (2009) (in press)

Clinical cross-over study N=32 Air leaks during mononasal CPAP with and without nostril occlusion Commercial Ventilator (Leoni M, Heinen&Löwenstein) 11/32 (34.4%) infants excluded due to air leaks >90%

1) Schmalisch G, et al. BMC Pediatrics 2009

* After BTPS Correction

Fischer HS, et al. 2009

(Leak <20%)

Hückstädt T, et al. 2003

Boumecid H, et al. 2007

Pandit et al. 2001

(CPAP=6cmH2O)

TB Measurements in CLD infants1)

Device Leoni

(H&L)

Infant Flow system (H&L)

Infant Flow (EME Tricomed)

Aladin/Infant Flow system (Hamilton)

Custom-made

VT measurement Anemometer FTT (PNT) Calibrated RIP Calibrated RIP FTT (PNT)

VT (ml·kg-1) 5.8±1.3 5.3±1.3 5.8±2.4 6.0±2.9 5.7±1.5*

RRvent (min-1) 53.6±19.2 57.0±18 57.0±19.5 64±18 55.4±14

V?E (ml·min-1·kg-1) 294±101 322±157 330 384 304±84*

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Time (min) 1 10

Nostril open Nostril occluded

Pat. 1

Pat. 32

2 3 4 5 6 7 8 9 1 102 3 4 5 6 7 8 9

Mouth open

Mouth occluded

Mouth opening 79.7% Mouth opening 86.6%

Fischer HS, et al. ERS Vienna 2009

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Effect of mouth opening on measured leakEffect of mouth opening on measured leak

90%

80%

70%

60%

50%

40%

30%

20%

10%

0%

Mouth closed Mouth open

Air

leak

age

(%)

Fischer HS, et al. Intens. Care Med. 2009 (in press)

Nasopharyngeal CPAP with occluded contralateral nostril

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Clinical impact of air leakages during CPAPClinical impact of air leakages during CPAP

Consequences of air leakages during nasal mask ventilation in adultsRabec CA et al. Leak Monitoring in Noninvasive Ventilation. Arch Bronconeumol 2004;40(11):508-17 

Temporary air leakages Large air leakages

Discomfort and treatment

intolerance

Adverse effects (eye irritation,

mouth dryness, nasal symptoms)

Trigger failure

Failure in automatic CPAP titration

Decrease in ventilation

effectiveness

Impossible to maintain optimal CPAP

Loss of patient triggering

Failure of CPAP control

Sleep fragmentation

Greater requirement of oxygen

Inefficacy of CPAP treatment

What is relevant for the CPAP treatment in newborns?

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ConclusionConclusion

Monitoring of ventilation and air leakages during CPAP is much

more difficult compared to mechanical ventilation

For most CPAP interfaces used in neonates no suitable

measuring technique is available

Air leakages during CPAP (e.g. mouth leaks) are very common

and should be quantified by the leak flow.

To which extent a breath detection (e.g. for CPAP triggering)

and volume monitoring is possible in the presence of large air

leakages is still unknown.

New clinical studies are necessary to investigate the effect of

air leakages on the efficiency of the CPAP treatment.