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1 The importance of measuring negative expiratory pressure (NEP) in the diagnosis of obstructive sleep apnoea syndrome (OSAS) Yelda Turgut, Zeynep Atam, Melahat Uygun, Çağlar Çuhadaroğlu, Tunçalp Demir, Birsen Mutlu

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The importance of measuring negative expiratory pressure (NEP) in the diagnosis of obstructive sleep apnoea syndrome (OSAS). Yelda Turgut, Zeynep Atam, Melahat Uygun, Çağlar Çuhadaroğlu, Tunçalp Demir, Birsen Mutlu. Diagnosis and Pathophysiology of OSAS. - PowerPoint PPT Presentation

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Page 1: Yelda Turgut, Zeynep Atam, Melahat Uygun, Çağlar Çuhadaroğlu,  Tunçalp Demir, Birsen Mutlu

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The importance of measuring negative expiratory pressure (NEP) in the diagnosis of obstructive sleep

apnoea syndrome (OSAS)

Yelda Turgut, Zeynep Atam, Melahat Uygun, Çağlar Çuhadaroğlu,

Tunçalp Demir, Birsen Mutlu

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Diagnosis and Pathophysiology of OSASDiagnosis and Pathophysiology of OSAS The diagnosis is made when the PSG monitoring of the The diagnosis is made when the PSG monitoring of the

patients who have clinical characteristics of OSAS such patients who have clinical characteristics of OSAS such as excessive daytime sleepiness, snoring and witnessed as excessive daytime sleepiness, snoring and witnessed apnoea, as well as demonstration of AHI>5 and apnoea, as well as demonstration of AHI>5 and obstructive nature of hypopnoea in more than 50% of obstructive nature of hypopnoea in more than 50% of occasions. occasions.

There are three major factors causes upper airway (UA) There are three major factors causes upper airway (UA) obstruction and collapse, namely anatomical obstruction and collapse, namely anatomical abnormalities of UA, negative pressure generated abnormalities of UA, negative pressure generated during inspiration and the loss of activity of pharyngeal during inspiration and the loss of activity of pharyngeal muscles that dilate the airway during sleep. muscles that dilate the airway during sleep.

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**Abnormal-narrow UA increases the resistance Abnormal-narrow UA increases the resistance ** Increased pharyngeal compliance -Pcrit is Increased pharyngeal compliance -Pcrit is

higher during inspirationhigher during inspiration** Muscles are hypotonic and response to negative Muscles are hypotonic and response to negative

pressure is decreasedpressure is decreased

OBSTRUCTED UPPER AIRWAY DURING INSPIRATION

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Airway during expiratory phaseAirway during expiratory phase

The compliance of UA is higher during expiratory The compliance of UA is higher during expiratory phase of patients who have increased OSASphase of patients who have increased OSAS

Marked narrowed UA is seen at the end of expiration in supine Marked narrowed UA is seen at the end of expiration in supine position in patients with OSAS. Expiratory positive airway position in patients with OSAS. Expiratory positive airway pressure (EPAP) is required to maintain the UA patency.pressure (EPAP) is required to maintain the UA patency.

Schwab R. Am Rev Respir Dis 1993, Sanders MH. Chest Schwab R. Am Rev Respir Dis 1993, Sanders MH. Chest 1990 1990

Studies suggest that both in loud snorers and OSAS patients, Studies suggest that both in loud snorers and OSAS patients, increased airway resistance, particularly in supine position, flow increased airway resistance, particularly in supine position, flow limitation (FL) and obstruction occur both during inspiration and limitation (FL) and obstruction occur both during inspiration and expiration. expiration.

Liistro G, J Appl Physiol 1990, Brown IG, Am Rev Respir Dis 1985, Liistro G, J Appl Physiol 1990, Brown IG, Am Rev Respir Dis 1985, Tamisier Sleep 2004 Sanders MH. Am Rev Respir Dis 1983,.Morrell AJRCCM 1998,

Focus on Focus on expirationexpiration

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NEGATIVE EXPIRATORY PRESSURE NEGATIVE EXPIRATORY PRESSURE (NEP) TECHNIQUE(NEP) TECHNIQUE

NEP is a technique which is basically NEP is a technique which is basically developed to detect the intrathorasic flow developed to detect the intrathorasic flow limitation during expiration.limitation during expiration.

NEP technique involves applying -3 or –5 cm HNEP technique involves applying -3 or –5 cm H22O O negative pressure on the mouth during tidal expiration negative pressure on the mouth during tidal expiration and comparing the emerged expiratory and comparing the emerged expiratory ύύ-V curve with -V curve with the standard control expiration curve. Data analysis is the standard control expiration curve. Data analysis is made by visual analysis of the two made by visual analysis of the two ύύ -V curves. -V curves.

To simply the readings, limited expiratory flow is To simply the readings, limited expiratory flow is expressed as the percentage of the control tidal volume expressed as the percentage of the control tidal volume (V(VTT%). %).

Page 6: Yelda Turgut, Zeynep Atam, Melahat Uygun, Çağlar Çuhadaroğlu,  Tunçalp Demir, Birsen Mutlu

66Examples of NEP tracing of normal and flow Examples of NEP tracing of normal and flow

limited patientslimited patients

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A highly suggestive example of NEP tracing A highly suggestive example of NEP tracing demonstrating increased upper airway demonstrating increased upper airway

resistanceresistance

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NEP in OSASNEP in OSAS The major drawback of NEP technique in detecting intrathoracic The major drawback of NEP technique in detecting intrathoracic

FL in snorers and patients with OSAS is the reflection of FL in snorers and patients with OSAS is the reflection of increased airway resistance to NEP measurement. increased airway resistance to NEP measurement.

In the absence of any underlying cardiac-lung disease that can In the absence of any underlying cardiac-lung disease that can cause intrathoracic FL, this disadvantage was turned into an cause intrathoracic FL, this disadvantage was turned into an advantage by using the NEP technique in the diagnosis of OSAS advantage by using the NEP technique in the diagnosis of OSAS patients. patients. UUnstable UAs with high compliance will respond with nstable UAs with high compliance will respond with narrowing even if not with obstruction to negative pressure narrowing even if not with obstruction to negative pressure created during expiration, namely FL in the NEP trace during created during expiration, namely FL in the NEP trace during expiration FL that is expressed as the percentage of Vexpiration FL that is expressed as the percentage of VTT was found was found to be well-correlated with DI and AHI. to be well-correlated with DI and AHI.

Liistro G. Eur Respir J 1999, Verin E. Thorax 2002.Liistro G. Eur Respir J 1999, Verin E. Thorax 2002.

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The role of NEP technique in the diagnosis of OSAS ?

Aim of the study

The correlation between FL demonstrated by NEP technique and PFTs, the airway resistance

(Raw) and AHI and DI derived by PSG?

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Material-Method & Statistical AnalysisMaterial-Method & Statistical Analysis

63 patients (43 male63 patients (43 male, 20 female, 20 female) were subjected ) were subjected to overnight PSG in sleep laboratoriesto overnight PSG in sleep laboratories

Extended PFTs by body pletsymography Extended PFTs by body pletsymography

FL detection by NEP technique at -5 cmHFL detection by NEP technique at -5 cmH22O O

both in upright and supine position both in upright and supine position

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AnthropometricAnthropometriccharacteristicscharacteristics

mean±SDmean±SD Sleep parametersSleep parameters mean±SDmean±SD

Age (years)Age (years) 47.28±9,6347.28±9,63AHIAHI

29,49± 23,1529,49± 23,15

BMI (kg/heightBMI (kg/height22)) 32,7732,77±±6,236,23DIDI

25,58±21,9425,58±21,94

Neck circumference Neck circumference (cm)(cm)

41.66±4,4841.66±4,48Minimum Minimum

saturation (%) saturation (%) 79,59±9,7679,59±9,76

HIHI 11,03±8,5611,03±8,56

RESULTS-1RESULTS-1

Table 1: Anthropometric characteristics of patients and Table 1: Anthropometric characteristics of patients and parameters obtained from PSGparameters obtained from PSG

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RESULTS-2RESULTS-2

Patients n (%)Patients n (%) DiagnosisDiagnosis

BMI<25BMI<25 3 (%4,8)3 (%4,8) NormalNormal

25 ≤ 25 ≤ BMI<30BMI<30 19 (%30,2)19 (%30,2) OverweightOverweight

30 ≤BMI<4030 ≤BMI<40 36 (%57,1)36 (%57,1) ObeseObese

BMI ≥40BMI ≥40 5 (%7,9)5 (%7,9) Morbid ObeseMorbid Obese

Table 2: The classification of obesity according to BMI Table 2: The classification of obesity according to BMI of the patientsof the patients

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63 Patients63 Patients

7 Patients 7 Patients (%11.1)(%11.1)

AHI<5

Primary snoring

5≤AHI<15

13 Patients 13 Patients (%20.6)(%20.6)

Mild OSAS

15≤AHI<30 AHI≥30

17 Patients 17 Patients (%27)(%27)

26 Patients 26 Patients (%41,3)(%41,3)

Severe OSASModerate OSAS

The severity of OSAS patients according to PSG

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Table 3: Significant correlations between all parameters and FL Table 3: Significant correlations between all parameters and FL % both in supine and upright position% both in supine and upright position

FL %(upright) FL %(supine)

r p r p

FL %(supine) ,349 ,005

AGE ,105 ,413 ,276 ,028

FEV1 -,194 ,128 -,246 ,050

RV -,065 ,616 ,256 ,043

RV/TLC ,116 ,366 ,304 ,015

SRAW% ,072 ,576 ,250 ,049

RAWTOT ,136 ,287 ,283 ,025

RAWTOT% ,134 ,294 ,285 ,023

RESULTS-4RESULTS-4

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Neck circumference -,5 ,694 -,15 ,220

BMI ,173 ,176 ,203 ,110

AHİ -,079 ,539 ,020 ,874

Desaturation index -,091 ,479 ,005 ,968

MINSAT -,021 ,868 -,013 ,918

FL %(upright) FL % (Supine)

r p r p

Table 4: The correlations between the important parameters for Table 4: The correlations between the important parameters for OSAS and FL % both in upright and supine positionsOSAS and FL % both in upright and supine positions

RESULTS-5RESULTS-5

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FL (upright)

FL (-) FL (+)

mean sd mean sd p

HEIGHT 168,94 10,26 161,20 10,69 ,034

BMI 32,06 5,66 36,51 7,98 ,037

FEV1 3164,07 878,68 2495,00 879,33 ,050

TLC 5822,64 1159,33 4910,00 1233,10 ,027

VC 3868,11 1035,68 3135,00 1145,36 ,048

P0.1 3,32 1,30 4,47 1,50 ,015

MEP% 72,94 28,03 97,62 40,01 ,033

Table 5: The parameters significantly different between the Table 5: The parameters significantly different between the patients with limited & unlimited flow while upright.patients with limited & unlimited flow while upright.

RESULTS-6RESULTS-6

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Table 6: The parameters significantly different between the Table 6: The parameters significantly different between the patients with limited & unlimited flow in supine position.patients with limited & unlimited flow in supine position.

Supine FL FL (-) FL (+)

mean sd mean sd p

WEIGHT 86,68 13,01 98,42 21,27 ,009

BMI 30,85 5,01 35,16 6,84 ,005

RV/TLC 32,74 7,34 37,14 9,32 ,040

FRC% 94,60 16,41 84,50 19,14 ,028

SRAWTOT 1,25 ,38 1,53 ,53 ,030

RAWTOT ,42 ,13 ,57 ,21 ,004

RAWTOT% 143,25 43,62 191,60 70,89 ,004

P0.1 3,15 1,32 3,95 1,35 ,014

P0.1% 157,85 66,32 212,25 104,56 ,010

RESULTS-7RESULTS-7

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1818Table 7: The differences of sleep parameters in the presence Table 7: The differences of sleep parameters in the presence of FL in upright and supine positions. of FL in upright and supine positions.

FL (upright) FL (-) FL (+)

mean sd mean sd p

AHİ 30,84 24,18 22,33 15,68 ,290

Desaturation index 26,67 23,1645 19,82 13,14 ,369

MINSAT 79,83 9,7762 78,28 10,10 ,647

FL (Supine) FL (-) FL (+)

mean sd mean sd p

AHİ 27,32 21,31 32,21 25,40 ,498

Desaturation index 22,77 19,24 29,11 24,82 ,361

MINSAT 81,28 6,89 77,48 12,27 ,364

RESULTS-8RESULTS-8

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Table 8: The statistical characteristics of NEP technique in Table 8: The statistical characteristics of NEP technique in the diagnosis of OSASthe diagnosis of OSAS

RESULTS-9RESULTS-9

Sensivity(%)

Spesifit (%)

PPD(%)

NPD(%)

FL(upright) 14,3 71,4 80 7,9

FL(supine) 44,6 57,1 89,3 6,3

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DISCUSSION-1DISCUSSION-1

The positive (+) PV of NEP technique when seated and The positive (+) PV of NEP technique when seated and supine were % 80 and % 89.3, respectively. This (+) supine were % 80 and % 89.3, respectively. This (+) PV strongly suggests that FL, that was found when PV strongly suggests that FL, that was found when seated and supine position in patients who are seated and supine position in patients who are suspected for OSAS is due to OSAS. suspected for OSAS is due to OSAS.

No differences found between the patients who are No differences found between the patients who are flow limited and free of limitation in sleep parameters flow limited and free of limitation in sleep parameters and no correlation found with the degree of FL that was and no correlation found with the degree of FL that was shown by the previous studies.shown by the previous studies.

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DISCUSSION-2DISCUSSION-2 The high value of BMI, the reduction in FEVThe high value of BMI, the reduction in FEV11, VC, , VC,

and TLC together in patients who are flow limited and TLC together in patients who are flow limited both in upright and supine positions suggest that both in upright and supine positions suggest that obesity cause the restriction.obesity cause the restriction.

The increase of the degree of FL in correlation with The increase of the degree of FL in correlation with the airway resistance and the significant elevation of the airway resistance and the significant elevation of these parameters in flow limited patients suggest that these parameters in flow limited patients suggest that NEP technique may be used to indicate the increased NEP technique may be used to indicate the increased UA resistance, and consequently the collapsibility of UA resistance, and consequently the collapsibility of UA when intrathoracic obstruction is excluded.UA when intrathoracic obstruction is excluded.

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HIGHBMI

HIGHRAW

HIGHP 0,1

Narrowed UA by fat deposition

flow limited patients by NEP

Decreaed response during sleep

HIGH(+)PD

The pathophysiological components of

OSAS

The role of NEP technique in the diagnosis of OSAS ?

UA with high compliance

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DISCUSSION-4DISCUSSION-4 The widely accepted approach to patients who have The widely accepted approach to patients who have

clinically diagnosed as a possible OSAS is to perform clinically diagnosed as a possible OSAS is to perform limited PSG recording respiratory signals only. limited PSG recording respiratory signals only.

In order to select the patients who will undergo the In order to select the patients who will undergo the limited PSG, variety of scoring systems based on clinical limited PSG, variety of scoring systems based on clinical and anthropometric properties were suggested. and anthropometric properties were suggested.

However, the lack of correlation between the symptoms However, the lack of correlation between the symptoms and AHI is well-known. NEP technique can be used as and AHI is well-known. NEP technique can be used as an aide in diagnosis. an aide in diagnosis.

NEP technique is a simple, non-invasive method which NEP technique is a simple, non-invasive method which is performed daytime, therefore, it can be used as a is performed daytime, therefore, it can be used as a screening test to select patients for limited PSG in screening test to select patients for limited PSG in patients who are suspected to have OSASpatients who are suspected to have OSAS..

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THANK YOU FOR YOUR ATTENTION…THANK YOU FOR YOUR ATTENTION…