91
ORIGINAL SCIENTIFIC ARTICLE
Pleural manometry
Copyright (c) 2022 Slovenian Medical Journal. This work is licensed under a
Creative Commons Attribution-NonCommercial 4.0 International License.
Measurement of pleural pressure during therapeutic 
thoracentesis (pleural manometry) as a safe and 
objective method in the assessment of pleural effusion 
effect on symptom expression
Merjenje tlakov plevralnega prostora med razbremenilno punkcijo (plevralna manometrija) 
kot varna in objektivna metoda pri ocenjevanju vpliva plevralnega izliva na izražanje 
simptomov
Anita Meglič,1 Katja Adamič,2 Vladimir Dimitrić,2 Vesna Nikolić,2 Aleš Rozman,2 Mateja Marc Malovrh2
Abstract
Background: Patients with pleural effusion often require therapeutic thoracentesis (TT), which results in more or less 
pronounced dyspnea relief. Due to safety concerns, it is recommended to remove up to a maximum of 1500 mL effusion in 
one session.
Methods: 96 patients in whom TT was indicated were included in the study. VAS dyspnea score before, immediately af-
ter, two hours after TT, and in 73 patients additionally 24 hours after TT was collected. The amount of fluid removed was 
measured. During TT, water manometer was used to measure pleural pressures, from which pleural space elastance was 
calculated. Based on their elastance curves characteristics, the patients were divided into different groups.
Results: We found a correlation between initial pleural pressure/volume of effusion removed and dyspnea relief after TT. 
TT was most often terminated due to the onset of symptoms, in 16 patients it was terminated due to pleural pressure mea-
surement. 74 patients were classified in the group with a normal elastane curve, in 22 patients we detected unexpandable 
lungs. Although more than 1500 mL of effusion was removed in 32 (33%) patients, there were no important complications 
during TT.
1 Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
2 Interventional Pulmonology Department, University Clinic of Respiratory and Allergic Diseases Golnik, Golnik, Slovenia
Correspondence / Korespondenca: Anita Meglič, e: anitameglic@gmail.com
Key words: dyspena; visual analogue scale; elastance curves; unexpandable lung
Ključne besede: dispneja; vizualna analogna lestvica; elastančne krivulje; nezmožnost razpenjanja pljuč
Received / Prispelo: 31. 12. 2020 | Accepted / Sprejeto: 2. 5. 2021
Cite as / Citirajte kot: Meglič A, Adamič K, Dimitrić V, Nikolić V, Rozman A, Marc Malovrh M. Measurement of pleural pressure during 
therapeutic thoracentesis (pleural manometry) as a safe and objective method in the assessment of pleural effusion effect on symptom 
expression. Zdrav Vestn. 2022;91(3–4):91–9. DOI: https://doi.org/10.6016/ZdravVestn.3205
eng slo element
en article-lang
10.6016/ZdravVestn.3205 doi
31.12.2020 date-received
2.5.2021 date-accepted
Respiratory system Dihala discipline
Original scientific article Izvirni znanstveni članek article-type
Measurement of pleural pressure during ther-
apeutic thoracentesis (pleural manometry) as 
a safe and objective method in the assess-
ment of pleural effusion effect on symptom 
expression
Merjenje tlakov plevralnega prostora med razbre-
menilno punkcijo (plevralna manometrija) kot 
varna in objektivna metoda pri ocenjevanju vpliva 
plevralnega izliva na izražanje simptomov
article-title
Pleural manometry Plevralna manometrija alt-title
dyspena, visual analogue scale, elastance 
curves, unexpandable lung
dispneja, vizualna analogna lestvica, elastančne 
krivulje, nezmožnost razpenjanja pljuč kwd-group
The authors declare that there are no conflicts 
of interest present.
Avtorji so izjavili, da ne obstajajo nobeni 
konkurenčni interesi. conflict
year volume first month last month first page last page
2022 91 3 4 1 9
name surname aff email
Anita Meglič 1 anitameglic@gmail.com
name surname aff
Katja Adamič 2
Vladimir Dimitrić 2
Vesna Nikolić 2
Aleš Rozman 2
Mateja Marc Malovrh 2
eng slo aff-id
Faculty of Medicine, University 
of Ljubljana, Ljubljana, Slovenia
Medicinska fakulteta, Univerza v 
Ljubljani, Ljubljana, Slovenija 1
Interventional Pulmonology 
Department, University Clinic 
of Respiratory and Allergic 
Diseases Golnik, Golnik, 
Slovenia
Klinični oddelek za interventno 
pulmologijo, Univerzitetna 
klinika za pljučne bolezni in 
alergijo Golnik, Golnik, Slovenija
2
Slovenian Medical Journallovenian Medical Journal
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1 Introduction
Pleural effusion is the presence of an increased 
amount of free fluid in the pleural space, which fre-
quently causes shortness of breath (1). Not every pleu-
ral effusion causes breathing difficulties, so evaluating 
which symptoms a pleural effusion causes, if any, is im-
portant (2). The mechanisms by which a pleural effusion 
causes shortness of breath (dyspnoea) are complex and 
not wholly explained. The displacement and change in 
the shape of the diaphragm, mechanoreceptors that de-
tect changes in lung volume and susceptibility to irri-
tation caused by excess pleural fluid probably all likely 
contribute (1,3).
A large pleural effusion is managed by ultrasound 
(US) guided therapeutic thoracentesis (TT) with which 
as much fluid as possible is removed for symptomatic 
relief, obtaining material for further diagnostic analysis 
and sometimes also to facilitate other necessary invasive 
tests (4,5). To prevent possible TT complications (chest 
pain, pneumothorax, re-expansion pulmonary oedema 
(RPO)), removal of only 1,500 mL of pleural effusion in 
one session is recommended (7,8). One study showed 
that removing more than 1,500 mL of fluid resulted in 
3.8 times more complications and five times as many 
cases of pneumothorax than removing smaller amounts 
of effusion (7). Pleural manometry is a technique used 
for measuring pleural pressures during TT (9). A sim-
ple water manometer or variants of more sophisticated 
Conclusion: Higher initial pleural pressure is weakly correlated with higher initial dyspnea and greater dyspnea relief after 
TT. The dynamic of pleural pressure change is useful for detecting unexpandable lungs during TT. During TT with pleural 
manometry, more than 1500 mL of pleural fluid can be safely removed.
Izvleček
Izhodišča: Bolniki s plevralnim izlivom pogosto potrebujejo razbremenilno plevralno punkcijo (RPP), po kateri navajajo 
bolj ali manj izrazito olajšanje dispneje. Zaradi varnosti se priporoča, da se med RPP odstrani do 1.500 mL tekočine.
Metode: V raziskavo smo vključili 96 bolnikov, pri katerih je bila potrebna RPP. Zbirali smo ocene stopnje dispneje na lestvi-
ci VAS pred, takoj po in 2 uri po RPP, pri 73 bolnikih pa še 24 ur po RPP ter beležili količino odstranjene tekočine. Med RPP 
smo z vodnim manometrom merili plevralne tlake, iz katerih smo izračunali elastanco plevralnega prostora in na podlagi 
meritev bolnike razdelili v skupine z različnimi elastančnimi krivuljami.
Rezultati: Med začetnim plevralnim tlakom in količino odstranjene tekočine ter olajšanjem dispneje po opravljeni RPP 
smo ugotovili statistično značilno povezanost. Pri največjem deležu bolnikov smo RPP zaključili zaradi pojava simptomov, 
zaradi meritev plevralnega tlaka pa smo RPP prekinili pri 16 bolnikih (16,7 %). V skupino z normalno elastančno krivuljo 
smo uvrstili 74 bolnikov, nezmožnost razpenjanja pljuč pa smo ugotovili pri 22 bolnikih. Med RPP ni bilo pomembnih za-
pletov, kljub temu da smo več kot 1.500 mL izliva odstranili pri 32 (33 %) bolnikih.
Zaključek: Višji začetni plevralni tlak je šibko povezan z višjo začetno stopnjo dispneje in večjim olajšanjem dispneje po 
opravljeni RPP. Najbolj uporabna je dinamika sprememb plevralnega tlaka, s katero lahko že med RPP prepoznamo ne-
zmožnost razpenjanja pljuč. Med RPP s plevralno manometrijo lahko varno odstranimo tudi več kot 1.500 mL tekočine.
electronic manometers are used (10). The measurements 
themselves are not time consuming, so TT duration is 
not significantly extended due to manometry (11). There 
is currently no consensus on the routine use of pleural 
manometry during TT (6). During TT, pleural pressure 
varies from patient to patient depending on the volume 
of fluid removed (9). Based on this finding, three dif-
ferent elastance curves were developed to help with di-
agnosing unexpandable lung (9,12). In lungs capable of 
normal expansion, the removal of pleural fluid causes 
the initially positive pleural pressure to gradually drop 
with a calculated pressure drop of less than 14.5 cm H2O 
per 1 litre of removed fluid (elastance < 14,5 cm H2O/L) 
to normal pleural pressures (from –3 do –5 cm H2O): 
we observe a normal elastance curve. In lungs incapable 
of expansion due to sequelae of previous active inflam-
matory or malignant disease (the causes for this are dif-
ferent, e. g. atelectasis, thickened visceral pleura, etc.), 
the elastance curve can initially follow the normal curve 
and breaks from it at the point where lung expansion 
cannot follow the removal of pleural fluid. With further 
removal of fluid, the pleural pressure falls (normally 
in the negative pressure range): we observe a biphasic 
elastance curve. In trapped lung, the initial part of the 
normal elastance curve is missing and pleural pressure 
drops faster from the onset: we observe a monophasic 
curve with high elastance (12,13).
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ORIGINAL SCIENTIFIC ARTICLE
Pleural manometry
The aim of the study was to determine the possible 
association between initial pleural pressure with the de-
gree of dyspnoea before TT and dyspnoea relief after TT 
and to see if the dynamics of changing pleural pressure 
can help with the decision to stop with TT. We further 
sought to determine whether larger amounts of pleural 
fluid than otherwise recommended could be safely re-
moved at one time.
2 Methods
The study was conducted at Interventional Pulmon-
ology Department at the University Clinic Golnik and 
was approved by the National Medical Ethics Commit-
tee (approval nrs. 206/03/13 and 0120-83/2020/9).
The study included patients who required TT and 
who were admitted to the Interventional Pulmonology 
Department during the 18-months study period. In-
clusion criteria were a pleural effusion, visible on chest 
radiography, which required TT, age over 18 years and 
a signed consent form. Exclusion criteria were an inabil-
ity to sit during TT, not wishing to take part in the study 
or an inability to give an adequate estimate of the degree 
of dyspnoea on a visual analogue scale (VAS). Age, pri-
or TT or other pleural space interventions, underlying 
disease, pleural effusion cause and size did not affect the 
inclusion of patients in the study.
All TT with manometry was performed by pulmo-
nologists employed at the Interventional Pulmonology 
Department according to the standardized TT proce-
dure of the University Clinic Golnik. Before TT, the ap-
propriate site for thoracentesis needle insertion in the 
lower part of the pleural effusion was determined by ul-
trasound examination of the hemithorax. A water ma-
nometer, normally intended for measuring central ve-
nous pressures, was used to measure pleural pressures. 
Following insertion in the pleural space, the thoracente-
sis catheter was connected to a tube with two outlets, al-
lowing for selective closing or opening of both distribu-
tion outlets. One outlet was connected via sterile tubing 
to an infusion system filled with normal saline, connect-
ed to a manometer, and the other with a 2,000 mL col-
lecting bag placed in a container on the floor where the 
pleural fluid drained. The pleural fluid was drained with 
the help of the hydrostatic pressure difference between 
the pleural space and the lower collecting bag. The pleu-
ral pressure was first measured after removing 20 mL 
of effusion, followed by measurements after every 100 
mL of removed fluid, and finally at the end of TT before 
the removal of the thoracentesis catheter. We measured 
the end-expiratory pleural pressure. Prior to TT start, 
the height of the diaphragm dome was determined and 
marked in the posterior axillary line with ultrasound, 
which was considered the reference point for all further 
measurements. The height of the diaphragm dome was 
checked with US during TT (for every 200mL of fluid 
removed) and at the end. We considered the difference 
between the dome height marks before and after TT as a 
diaphragm elevation. Prior to TT, we also instructed pa-
tients to report any symptoms that would appear during 
TT. We ended the procedure when:
• the fluid stopped draining;
• the pleural space pressure fell to –20 cm H2O or 
pressure fell for more than 4 cm H2O between two 
measurements in a patient with an already negative 
pleural space pressure;
• symptoms such as persistent chest pain or unrelent-
ing cough appeared;
• for other reasons, as decided by the pulmonologist.
VAS is a 100 mm long horizontal line, marked with 
»without any breathing difficulties« at one end and 
»severe breathing difficulties« at the other and is also 
equipped with appropriate pictures. The patient marks 
a point on the line that they believe represents their cur-
rent condition. The VAS value is the distance between 
the start of the line and the marked spot (14). All in-
cluded patients were asked to evaluate their level of dys-
pnoea before, immediately after and two hours after TT. 
In 73 patients, VAS values were additionally obtained 
24 hours after TT (in 23 patients we could not obtain 
this score as they had already left the hospital on the day 
of the procedure, and for some, we forgot to record the 
data). Afterwards, we calculated the VAS changes im-
mediately and two and 24 hours after VAS, depending 
on the initial VAS value before TT.
Dyspnoea relief greater than 20 mm on VAS was 
labelled as clinically significant. The 20 mm limit was 
chosen based on the results of the study by Mishra et al, 
which found that patients perceived dyspnoea relief of 
19 mm and more as clinically significant (15).
The pleural space elastance was calculated by divid-
ing the change in pleural pressure in cm H2O by the 
volume of fluid removed in litres. For biphasic curves, 
the elastances of the first and second parts of the curve 
were calculated separately. According to the dynamics 
of changes in pleural pressures during TT, patients were 
divided into two groups. The first group with a normal 
elastance curve included patients in whom the pleu-
ral pressures changed throughout TT in proportion to 
the volume of the fluid removed. In these patients, the 
elastance curve was monophasic and the pleural space 
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elastance less than 14.5 H2O/L at all times. The second 
group included patients in whom an accelerated de-
cline in pleural pressures (elastance> 14.5 cm H2O/L in 
at least two consecutive measurements in the negative 
range) could be detected during TT with manometry at 
the beginning or in the second part of TT.
Before and after TT, chest radiography was per-
formed in the posteroanterior and lateral projections. 
The size of the pleural effusion was determined based 
on pulmonary opacification.
From the BIRPIS system we obtained data on the 
general demographic characteristics of the patient (age, 
sex), assessment of performance status according to the 
World Health Organization (WHO), the cause of pleu-
ral disease (carcinosis, malignant mesothelioma, infec-
tion, cardiovascular disease, unspecified effusion), pos-
sible pleural effusion treatment before TT and during 
the one-month period after TT.
GraphPad Prism, version 8.4.3 (GraphPad Software, 
San Diego, USA) was used for statistical data process-
ing. The Shapiro-Wilk test was used to test the normal-
ity of data distribution. To test statistically significant 
differences between the two groups, we used the t-test 
for independent samples when the data were normally 
distributed. In case the data were not normally distrib-
uted, we used the Mann-Whitney test. The Spearman 
correlation coefficient was used to test the intensity of 
the correlation of the two variables. Data with a cal-
culated value of p <0.05 were considered statistically 
significant.
3 Results
3.1 Patient characteristics
The study included 96 patients, of whom 68 (70.8%) 
were men and 28 (29.2%) were women. The mean pa-
tient age was 71 ± 1 year. Most of the patients had a 
good performance status score, 71 (74%) were classified 
in the first or second functional class, and 25 (26%) in 
the third class according to the assessment of perfor-
mance status according to the World Health Organiza-
tion (WHO).
Depending on the pleural effusion size on the pre-
TT chest radiograph, 43 (44.8%) patients had an effu-
sion that was smaller than half of the hemithorax and 
53 (55.2%) patients had an effusion that was larger than 
half of the hemithorax, of whom 12 (12.5%) had an ef-
fusion that opacified the entire hemithorax.
The causes of pleural effusion in included patients 
are shown in Table 1.
Cause Number of 
patients
Proportion of 
patients (%)
Pleural carcinomatosis 60 62.5
Pleural mesothelioma 10 10.4
Infection 11 11.5
Cardiovascular diseases 4 4.1
Unspecified 11 11.5
Table 1: Pleural effusion causes in patients, included in the 
study.
3.2 Amount of fluid removed, pleural 
pressures and VAS values during therapeutic 
thoracentesis
The median value of the amount of effusion removed 
during TT was 1,250 mL (800–1,700 mL interquartile 
range). More than 1,500 mL of fluid was removed in 32 
(33%) patients. The median value of the initial pleural 
pressure was 5 cm H2O (interquartile range 2–9.8 cm 
H2O). Negative pleural pressure at TT onset was mea-
sured in 10 patients, two of whom were below −5 cm 
H2O. The median value of the final pleural pressure was 
−4 cm H2O (interquartile range −6–0 cm H2O).
The median value of diaphragm lift during TT was 2 
cm (interquartile range 1–4 cm).
VAS values before, immediately after, two hours af-
ter and 24 hours after TT are shown in Figure 1. Clin-
ically significant dyspnoea relief (change in VAS> 20 
mm) was observed immediately after TT in 40 (41.6%) 
patients and in 56 (58.3%) patients two hours after TT. 
Of the 73 patients in whom a VAS score 24 hours after 
TT was collected, clinically significant dyspnoea relief 
immediately after TT was reported by 31 (42.4%) pa-
tients, two hours after TT by 41 (56.2%) patients and in 
46 (63%) patients 24 hours after TT. Clinically signifi-
cant dyspnoea worsening was observed in three (3.1%) 
patients immediately after TT.
Fluid volume removed was statistically significantly 
associated with dyspnoea relief immediately after TT (ρ 
= –0.22; p = 0.028), dyspnoea relief two hours after TT 
(ρ = –0.21; p = 0.04) and dyspnoea relief 24 hours after 
TT (ρ = –0.27; p = 0.019).
Initial pleural pressure was associated with pre-TT 
VAS (ρ = 0.20; p = 0.049), dyspnoea relief two hours 
after TT (ρ = −0.22; p = 0.028) and dyspnoea relief 24 
hours after TT (ρ = −0.32; p = 0.006), but not with dys-
pnoea relief immediately after TT (ρ = −0.15; p = 0.14). 
We also found an association between initial pleural 
pressure and final pleural pressure (ρ = 0.67; p <0.001), 
diaphragm elevation (ρ = 0.44; p <0.001) and fluid vol-
ume removed (Figure 2).
Figure 1: Time-dependent visual analogue scale values 
displayed by median, interquartile range, and range.
Legend: VAS – visual analogue scale; TT – therapeutic 
thoracentesis; VAS p – VAS assessment prior to TT; VAS1 – VAS 
assessment immediately after TT; VAS 2 – VAS assessment 
two hours after TT; VAS 24 – VAS assessment 24 hours after TT.
0
50
100
150
VAS p VAS 1 VAS 2 VAS 24
VA
S 
(m
m
)
p < 0.0001
p < 0.0001
p < 0.0005
p < 0.0001
p < 0.0005
Figure 2: Association between the initial pleural pressure, fluid volume removed (A) and dyspnoea relief two hours after 
TT (B).
Legend: VAS – visual analogue scale); TT – therapeutic thoracentesis; VASchg2 – the difference between the VAS assessment 
prior to TT and two hours after TT.
0
1000
2000
3000
4000
5000
-10 0 10 20
Vo
lu
m
e 
of
 fl
ui
d 
re
m
ov
ed
 (m
L) p < 0.0001
ρ = 0.6533
Initial pleural pressure (cm H2O)
-100
-50
0
50
VA
Sc
hg
2 
(m
m
)
Initial pleural pressure (cm H2O)
-10 0 10 20
p < 0.028
ρ = -0.2249
A B
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ORIGINAL SCIENTIFIC ARTICLE
Pleural manometry
The median value of diaphragm lift during TT was 2 
cm (interquartile range 1–4 cm).
VAS values before, immediately after, two hours af-
ter and 24 hours after TT are shown in Figure 1. Clin-
ically significant dyspnoea relief (change in VAS> 20 
mm) was observed immediately after TT in 40 (41.6%) 
patients and in 56 (58.3%) patients two hours after TT. 
Of the 73 patients in whom a VAS score 24 hours after 
TT was collected, clinically significant dyspnoea relief 
immediately after TT was reported by 31 (42.4%) pa-
tients, two hours after TT by 41 (56.2%) patients and in 
46 (63%) patients 24 hours after TT. Clinically signifi-
cant dyspnoea worsening was observed in three (3.1%) 
patients immediately after TT.
Fluid volume removed was statistically significantly 
associated with dyspnoea relief immediately after TT (ρ 
= –0.22; p = 0.028), dyspnoea relief two hours after TT 
(ρ = –0.21; p = 0.04) and dyspnoea relief 24 hours after 
TT (ρ = –0.27; p = 0.019).
Initial pleural pressure was associated with pre-TT 
VAS (ρ = 0.20; p = 0.049), dyspnoea relief two hours 
after TT (ρ = −0.22; p = 0.028) and dyspnoea relief 24 
hours after TT (ρ = −0.32; p = 0.006), but not with dys-
pnoea relief immediately after TT (ρ = −0.15; p = 0.14). 
We also found an association between initial pleural 
pressure and final pleural pressure (ρ = 0.67; p <0.001), 
diaphragm elevation (ρ = 0.44; p <0.001) and fluid vol-
ume removed (Figure 2).
Figure 1: Time-dependent visual analogue scale values 
displayed by median, interquartile range, and range.
Legend: VAS – visual analogue scale; TT – therapeutic 
thoracentesis; VAS p – VAS assessment prior to TT; VAS1 – VAS 
assessment immediately after TT; VAS 2 – VAS assessment 
two hours after TT; VAS 24 – VAS assessment 24 hours after TT.
0
50
100
150
VAS p VAS 1 VAS 2 VAS 24
VA
S 
(m
m
)
p < 0.0001
p < 0.0001
p < 0.0005
p < 0.0001
p < 0.0005
Figure 2: Association between the initial pleural pressure, fluid volume removed (A) and dyspnoea relief two hours after 
TT (B).
Legend: VAS – visual analogue scale); TT – therapeutic thoracentesis; VASchg2 – the difference between the VAS assessment 
prior to TT and two hours after TT.
0
1000
2000
3000
4000
5000
-10 0 10 20
Vo
lu
m
e 
of
 fl
ui
d 
re
m
ov
ed
 (m
L) p < 0.0001
ρ = 0.6533
Initial pleural pressure (cm H2O)
-100
-50
0
50
VA
Sc
hg
2 
(m
m
)
Initial pleural pressure (cm H2O)
-10 0 10 20
p < 0.028
ρ = -0.2249
A B
3.3 Reasons for discontinuing therapeutic 
thoracentesis
Reasons for TT discontinuation and parameter val-
ues in patients with different causes of TT discontinua-
tion are shown in Table 2.
Of the 34 patients in whom TT was discontinued 
due to symptoms, four reported chest pain and 30 re-
ported an unrelenting cough. Patients in whom TT was 
discontinued due to a fall in pleural pressure or low 
pleural pressure, statistically significantly less fluid was 
removed and lower final pressures were recorded than 
in patients in whom TT was discontinued due to ces-
sation of fluid drainage (p <0.001), physician decision 
(p <0.001) or onset of symptoms (p <0.001). Patients 
in whom TT was discontinued due to a fall in pleural 
pressure or low pleural pressure had statistically sig-
nificantly smaller changes in VAS changes immediately 
after TT compared to patients in whom TT was discon-
tinued due to physician decision (p = 0,035); the same 
was true two hours after TT (p = 0,016). The same trend 
was observed in comparison with other groups, but did 
not achieve statistical significance.
3.4 Pleural space elastance
According to the dynamics of pleural pressure chang-
es, 74 (77.1%) patients were classified in the group with 
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a normal elastance curve, and 22 (22.9%) patients in the 
group with unexpandable lung. Examples of patients 
with individual elastance curves are presented in Figure 3.
A group of six patients with unexpandable lung re-
ported symptoms during TT; five developed a cough and 
one experienced chest pain.
In 10 patients, pressures followed the biphasic elas-
tance curve. The cause of the pleural effusion was pleu-
ral malignancy in eight patients, infection in one (para-
pneumonic effusion in the fibrinopurulent phase) and 
active fibroproductive pleuritis in one. In all the pleural 
effusion persisted on the chest radiograph after TT. Two 
hours after TT, clinically significant dyspnoea relief was 
reported by five patients with a biphasic elastance curve. 
In 12 patients, pleural pressures during TT followed 
the monophasic curve with high elastance. In these pa-
tients. the predominant cause of the pleural effusion 
was infection (parapneumonic effusion sequelae in six 
patients), followed by pleural malignancy (five patients) 
and unspecified chronic pleuritis in one patient. After 
TT, two patients reported clinically significant dyspnoea 
Figure 3: Examples of patients with different elastance curves.
-20
-15
-10
-5
0
5
0 1000 2000
Volumen odstranjene tekočine (mL)
Bolnik z normalno elastančno krivuljo
Pl
ev
ra
ln
i t
la
k 
(c
m
 H
2O
)
500 1500 2500
10
Bolnik z bifazno elastančno krivuljo
Bolnik z monofazno krivuljo z visoko elastanco
Legend: *n = 73; TT – therapeutic thoracentesis; VAS – visual analogue scale; VASp – VAS assessment prior to TT; VAS1 – VAS 
assessment immediately after TT; VAS2 – VAS assessment two hours after TT; VAS24 – VAS assessment 24 hours after TT; 
VASchg1 – the difference between the VAS assessment immediately after and before TT; VASchg2 – the difference between the 
VAS assessment prior to TT and two hours after TT; VASchg24 – the difference between the VAS assessment prior to TT and 24 
hours after TT.
Reason for TT discontinuation Symptoms Cessation of 
drainage
Physician decision Fall in pressure/
low pressure
Number of patients 34 31 15 16
Final pleural pressure (cm H2O) –1.5 [–5.3–(+2)] –4 [–5–( –1)] –1 [–4–(+2)] –10 [–12–( –7.3)]
Volume of fluid removed (mL) 1350 [938–1700] 1300 [1000–1700] 1700 [1200–2300] 480 [163–825]
Diaphragm elevation (cm) 2 [1–4] 2.5 [1–4.5] 4 [1–6] 0 [0–2]
Patients without effusion on chest 
radiography after TT (number) 6 31 0 0
VASp (mm) 50 [38–73] 40 [0–60] 50 [30–60] 40 [25–60]
VAS1 (mm) 40 [30–50] 20 [0–40] 30 [10–40] 30 [20–54]
VAS2 (mm) 30 [8–31] 20 [0–30] 10 [0–30] 30 [10–40]
VAS24* (mm) 20 [0–30] 20 [0–30] 20 [0–40] 10 [3–40]
VASchg1 (mm) −13 [−21–0] −10 [−20–0] −20 [−40–0] 0 [−20–0]
VASchg2 (mm) −20 [−40–(–10] −20 [−30–0] −30 [−60–( −20)] −10 [−30–0]
VASchg24* (mm) −30 [−40–( −10)] −20 [−30–0] −30 [−40–( −20)] −18 [−38–( −1)]
Table 2: Parameter values in patients divided into groups according to the reason for TT discontinuation. Values are shown 
as median and interquartile range.
relief, even though only 120 mL and 200 mL of pleural 
fluid was removed; in other patients, TT had no effect 
on symptoms. After TT, all 12 patients still had a pleural 
effusion on chest radiography. No patient in this group 
required additional TT during the one-month follow-up 
period after TT.
3.5 Complications and safety
After TT, we found pneumothorax on chest radiogra-
phy in two patients; of these, the pneumothorax was on-
ly minimal in one patient, a 74-year-old patient in whom 
150 mL of effusion was removed with TT due to trapped 
lung. Pneumothorax also developed in an 81-year-old 
patient in whom 2,300 mL of effusion was removed. 
During TT, pleural pressure fell from +10 cm H2O to 
–5 cm H2O. Both patients were without problems after 
TT and also in the following days. Despite the resulting 
pneumothorax, both reported an improvement in VAS 
scores. Apart from observation, no further action was 
required.
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ORIGINAL SCIENTIFIC ARTICLE
Pleural manometry
a normal elastance curve, and 22 (22.9%) patients in the 
group with unexpandable lung. Examples of patients 
with individual elastance curves are presented in Figure 3.
A group of six patients with unexpandable lung re-
ported symptoms during TT; five developed a cough and 
one experienced chest pain.
In 10 patients, pressures followed the biphasic elas-
tance curve. The cause of the pleural effusion was pleu-
ral malignancy in eight patients, infection in one (para-
pneumonic effusion in the fibrinopurulent phase) and 
active fibroproductive pleuritis in one. In all the pleural 
effusion persisted on the chest radiograph after TT. Two 
hours after TT, clinically significant dyspnoea relief was 
reported by five patients with a biphasic elastance curve. 
In 12 patients, pleural pressures during TT followed 
the monophasic curve with high elastance. In these pa-
tients. the predominant cause of the pleural effusion 
was infection (parapneumonic effusion sequelae in six 
patients), followed by pleural malignancy (five patients) 
and unspecified chronic pleuritis in one patient. After 
TT, two patients reported clinically significant dyspnoea 
Figure 3: Examples of patients with different elastance curves.
-20
-15
-10
-5
0
5
0 1000 2000
Volumen odstranjene tekočine (mL)
Bolnik z normalno elastančno krivuljo
Pl
ev
ra
ln
i t
la
k 
(c
m
 H
2O
)
500 1500 2500
10
Bolnik z bifazno elastančno krivuljo
Bolnik z monofazno krivuljo z visoko elastanco
Legend: *n = 73; TT – therapeutic thoracentesis; VAS – visual analogue scale; VASp – VAS assessment prior to TT; VAS1 – VAS 
assessment immediately after TT; VAS2 – VAS assessment two hours after TT; VAS24 – VAS assessment 24 hours after TT; 
VASchg1 – the difference between the VAS assessment immediately after and before TT; VASchg2 – the difference between the 
VAS assessment prior to TT and two hours after TT; VASchg24 – the difference between the VAS assessment prior to TT and 24 
hours after TT.
Reason for TT discontinuation Symptoms Cessation of 
drainage
Physician decision Fall in pressure/
low pressure
Number of patients 34 31 15 16
Final pleural pressure (cm H2O) –1.5 [–5.3–(+2)] –4 [–5–( –1)] –1 [–4–(+2)] –10 [–12–( –7.3)]
Volume of fluid removed (mL) 1350 [938–1700] 1300 [1000–1700] 1700 [1200–2300] 480 [163–825]
Diaphragm elevation (cm) 2 [1–4] 2.5 [1–4.5] 4 [1–6] 0 [0–2]
Patients without effusion on chest 
radiography after TT (number) 6 31 0 0
VASp (mm) 50 [38–73] 40 [0–60] 50 [30–60] 40 [25–60]
VAS1 (mm) 40 [30–50] 20 [0–40] 30 [10–40] 30 [20–54]
VAS2 (mm) 30 [8–31] 20 [0–30] 10 [0–30] 30 [10–40]
VAS24* (mm) 20 [0–30] 20 [0–30] 20 [0–40] 10 [3–40]
VASchg1 (mm) −13 [−21–0] −10 [−20–0] −20 [−40–0] 0 [−20–0]
VASchg2 (mm) −20 [−40–(–10] −20 [−30–0] −30 [−60–( −20)] −10 [−30–0]
VASchg24* (mm) −30 [−40–( −10)] −20 [−30–0] −30 [−40–( −20)] −18 [−38–( −1)]
Table 2: Parameter values in patients divided into groups according to the reason for TT discontinuation. Values are shown 
as median and interquartile range.
4 Discussion
The study, which sought to evaluate the usefulness of 
measuring pleural space pressures during TT, included 
96 patients who were hospitalized at the Intervention-
al Pulmonology Department at the University Clinic 
Golnik during the study and required TT due to pleural 
effusion.
An important part of our study was determining the 
possible association between initial pleural pressure, 
volume of fluid removed and the degree of dyspnoea 
before TT and dyspnoea relief after TT. The expected 
correlation between the initial pleural space pressure 
and the volume of fluid removed was confirmed. Higher 
initial pleural pressure was also weakly associated with 
greater diaphragm lift during TT.
Dyspnoea severity after TT was clinically significant-
ly reduced in 42% of patients immediately after TT. The 
proportion of patients with clinically relevant dyspnoea 
relief increased to 58% after two hours and to 63% after 
24 hours. The temporal dynamics of symptoms suggest 
that the actual effect of TT on dyspnoea relief is more 
correctly assessed at least two hours after TT and not 
immediately afterwards, when patients still have prob-
lems with lung expansion and frequent cough or other 
symptoms. A study by Boshuizen et al found that most 
patients felt the greatest relief two days after TT, but un-
fortunately, we did not perform the VAS assessment in 
later days in our study (14).
The degree of dyspnoea relief was influenced by the 
amount of fluid removed, but the association was other-
wise weak. In other studies, too, little or no association 
was found between the amount of fluid removed and 
dyspnoea relief after TT (14,16). Therefore, the volume 
of removed pleural effusion alone is not a good prog-
nostic factor for dyspnoea relief after TT.
We did not find studies on the effect of pleural pres-
sure on the degree of dyspnoea. In our study, we found 
an association between initial pleural pressure and the 
degree of dyspnoea before TT and the degree of dys-
pnoea relief two and 24 hours after TT; the connection 
was otherwise weak. We can conclude that the associ-
ation between initial pleural pressure and the degree 
of dyspnoea relief after TT is too weak to predictably 
determine which patients will benefit symptomatically 
from TT only by assessing initial pleural pressure. By 
monitoring and recording the dynamics of pleural pres-
sures during the entire course of TT, we obtained im-
portant data on the pleural space events during the pro-
cedure, particularly the inability to expand the lungs. 
If negative pleural pressures are detected at any point 
during TT while the effusion is still present and high 
elastance is detected after further drainage, it is a certain 
sign that the lungs are incapable of further expansion 
and the patient would not benefit from additional fluid 
removal. There are the previously described cases of two 
groups of patients in whom pleural pressures during TT 
follow a biphasic elastance curve in the steep part, or 
the monophasic curve with hight elastance, characteris-
tic of trapped lung. Patients with trapped lung normally 
have less symptoms due to pleural effusions. Efficient 
treatment is surgical with decortication, rather than TT 
(13). In all patients in whom we suspected unexpand-
able lung from pleural space pressures during TT, chest 
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RESPIRATORY SYSTEM
Zdrav Vestn | March – April 2022 | Volume 91 | https://doi.org/10.6016/ZdravVestn.3205
radiography after TT still showed a pleural effusion 
(additionally, we found pneumothorax in two patients), 
which confirmed our suspicions. In patients whose 
pleural pressures followed a monophasic curve with 
high elastance, the suspicion of trapped lung during 
manometry was additionally confirmed by the subse-
quent course, in which their symptoms did not progress 
during the one-month follow-up after TT and they did 
not need additional effusion removal.
Metastatic malignancy was the cause of the pleural 
effusion in more than 70% of patients, which explains 
the higher proportion of large effusions (more than half 
of the hemithorax) and the significant proportion of in-
completely expanded lungs after TT (13,17). In patients 
with malignancy, the presence of central tumours or ex-
tensive visceral pleura involvement which can prevent 
complete lung expansion is possible, so complete remov-
al of the effusion is not possible or reasonable. In our 
study, opacification of more than half of the hemitho-
rax on chest radiography was found in 53 patients and 
more than 1,500 mL of fluid was removed in 31 (32%) 
patients, which is three times more than in the Lentz 
group, in which more than 1,500 mL was removed in 
only 7 (11%) patients. At the same time, we can observe 
than in 37 (38%) patients included in our study, pleural 
effusion was not detected or was only minimal on chest 
radiography after TT, which is a lower proportion than 
in the Lentz group, in which and US-visible residual ef-
fusion was reported in only 40% of patients (18).
Although the median volume of the effusion re-
moved during TT was 1,250 mL and we removed more 
than 1,500 mL of effusion in one third of the patients, 
no significant complications were detected. We found 
two (2.1%) instances of otherwise asymptomatic pneu-
mothorax ex vacuo with chest radiography after TT 
among 96 patients. In both cases an inability to expand 
the lung was found; in one case, the pressure changes 
followed the monophasic curve with high elastance and 
the biphasic curve in the second. The lower proportion 
of pneumothorax in our study compared to the study 
by Lentz et al, in which pneumothorax was detected in 
5% of patients, and the study by Villena et al, in which 
pneumothorax was detected in 14.8% of patients, can be 
attributed to a more conservative approach and TT dis-
continuation with less negative pressures in cases where 
we detected a rise in elastance, which we believe is the 
correct approach (18,19). RPO, a rarely described com-
plication of TT, was not detected in any patient. 
In 35% of patients, the onset of symptoms was the 
cause of TT discontinuation. Similar results were pub-
lished by Lentz et al, who discontinued TT in 37% due 
to the onset symptoms, and by Feller-Kopman et al, who 
discontinued TT in 17% due to the onset of symptoms, 
but in their studies, contrary to our results, chest pain 
was the most common symptom (18,20). Interestingly, 
in both our and the aforementioned studies, chest pain 
was not associated with either large volumes of fluid re-
moved or low final pleural pressures. Other, still unex-
plained factors obviously contribute to the discomfort, 
so chest pain cannot be prevented with pleural manom-
etry. In our patients, the most common TT-associated 
symptoms were a cough, which is not the consequence 
of the fall in pleural pressure, but rather the conse-
quence of lung expansion and resolution of atelectasis, 
which occur due to the removal of excess fluid (20).
The study’s shortcoming is that we chose a change 
in the degree of dyspnoea, which was assessed by VAS, 
to evaluate the effect of TT. Dyspnoea is an important 
symptom, which affects the patient’s quality of life, but 
it is difficult to objectively evaluate; we use subjective 
tools, which are by their nature not very reliable. Using 
more objective methods, such as measuring the patient’s 
performance with a 6-minute walk test, oxygenation at 
rest and during exertion and sleep abnormalities with 
polysomnography to evaluate the effect of TT on the 
patient’s quality of life would mean an upgrade to our 
study.
In 15 patients, TT was discontinued due to physician 
decision, which is probably the reason for the incorrect 
classification of some patients in the group with a nor-
mal elastance curve. We hypothesize that should TT 
continue, the transformation of the elastance curve into 
a biphasic one would manifest in some of these patients, 
as most had pressures in the negative range with the ef-
fusion still present.
5 Conclusion
Based on the findings of our study, we can predict 
the volume of fluid removed and change in the degree 
of dyspnoea after TT from the initial pleural pressure, 
although the association is weak. The main advantage 
of pleural manometry is its ability to detect patients 
whose lungs cannot expand during the procedure itself, 
thus allowing it to be discontinued in time, reducing the 
possibility of complications. With TT, more 1,500 mL of 
fluid can be safely removed with simultaneous pleural 
pressure measurements.
Conflict of interest
None declared.
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ORIGINAL SCIENTIFIC ARTICLE
Pleural manometry
References
1. Diaz-Guzman E, Dweik RA. Diagnosis and management of pleural 
effusions: a practical approach. Compr Ther. 2007;33(4):237-66. DOI: 
10.1007/s12019-007-8016-5 PMID: 18025616 
2. Miserocchi G. Physiology and pathophysiology of pleural fluid turnover. 
Eur Respir J. 1997;10(1):219-25. DOI: 10.1183/09031936.97.10010219 
PMID: 9032518 
3. Thomas R, Jenkins S, Eastwood PR, Lee YC, Singh B. Physiology of 
breathlessness associated with pleural effusions. Curr Opin Pulm Med. 
2015;21(4):338-45. DOI: 10.1097/MCP.0000000000000174 PMID: 25978627 
4. Qureshi N, Momin ZA, Brandstetter RD. Thoracentesis in clinical practice. 
Heart Lung. 1994;23(5):376-83. PMID: 7989206 
5. Karkhanis VS, Joshi JM. Pleural effusion: diagnosis, treatment, and 
management. Open Access Emerg Med. 2012;4:31-52. DOI: 10.2147/
OAEM.S29942 PMID: 27147861 
6. Havelock T, Teoh R, Laws D, Gleeson F; BTS Pleural Disease Guideline 
Group. Pleural procedures and thoracic ultrasound: British Thoracic 
Society Pleural Disease Guideline 2010. Thorax. 2010;65:ii61-76. DOI: 
10.1136/thx.2010.137026 PMID: 20696688 
7. Ault MJ, Rosen BT, Scher J, Feinglass J, Barsuk JH. Thoracentesis 
outcomes: a 12-year experience. Thorax. 2015;70(2):127-32. DOI: 10.1136/
thoraxjnl-2014-206114 PMID: 25378543 
8. Shechtman L, Shrem M, Kleinbaum Y, Bornstein G, Gilad L, Grossman C. 
Incidence and risk factors of pneumothorax following pre-procedural 
ultrasound-guided thoracentesis. J Thorac Dis. 2020;12(3):942-8. DOI: 
10.21037/jtd.2019.12.39 PMID: 32274162 
9. Light RW, Jenkinson SG, Minh VD, George RB. Observations on pleural 
fluid pressures as fluid is withdrawn during thoracentesis. Am Rev Respir 
Dis. 1980;121(5):799-804. PMID: 7406313 
10. Hu K, Chopra A, Huggins JT, Nanchal R. Pleural manometry: techniques, 
applications, and pitfalls. J Thorac Dis. 2020;12(5):2759-70. DOI: 
10.21037/jtd.2020.04.04 PMID: 32642184 
11. Zielinska-Krawczyk M, Krenke R, Grabczak EM, Light RW. Pleural 
manometry-historical background, rationale for use and methods 
of measurement. Respir Med. 2018;136:21-8. DOI: 10.1016/j.
rmed.2018.01.013 PMID: 29501243 
12. Huggins JT, Doelken P. Pleural manometry. Clin Chest Med. 
2006;27(2):229-40. DOI: 10.1016/j.ccm.2005.12.007 PMID: 16716815 
13. Huggins JT, Doelken P, Sahn SA. The unexpandable lung. F1000 Med Rep. 
2010;2:77. DOI: 10.3410/M2-77 PMID: 21173837 
14. Boshuizen RC, Vincent AD, van den Heuvel MM. Comparison of modified 
Borg scale and visual analog scale dyspnea scores in predicting re-
intervention after drainage of malignant pleural effusion. Support Care 
Cancer. 2013;21(11):3109-16. DOI: 10.1007/s00520-013-1895-3 PMID: 
23842597 
15. Mishra EK, Corcoran JP, Hallifax RJ, Stradling J, Maskell NA, Rahman NM. 
Defining the minimal important difference for the visual analogue scale 
assessing dyspnea in patients with malignant pleural effusions. PLoS 
One. 2015;10(4):e0123798. DOI: 10.1371/journal.pone.0123798PMID: 
25874452 
16. Psallidas I, Yousuf A, Talwar A, Hallifax RJ, Mishra EK, Corcoran JP, 
et al. Assessment of patient-reported outcome measures in pleural 
interventions. BMJ Open Respir Res. 2017;4(1):e000171. DOI: 10.1136/
bmjresp-2016-000171 PMID: 28883922 
17. Petrov R, Bakhos C, Abbas AE. Management of Malignant Lung 
Entrapment, the Oncothorax. Thorac Surg Clin. 2018;28(1):81-90. DOI: 
10.1016/j.thorsurg.2017.08.009 PMID: 29150040 
18. Lentz RJ, Lerner AD, Pannu JK, Merrick CM, Roller L, Walston C, et al. 
Routine monitoring with pleural manometry during therapeutic large-
volume thoracentesis to prevent pleural-pressure-related complications: 
a multicentre, single-blind randomised controlled trial. Lancet Respir 
Med. 2019;7(5):447-55. DOI: 10.1016/S2213-2600(18)30421-1 PMID: 
30772283 
19. Villena V, López-Encuentra A, Pozo F, De-Pablo A, Martín-Escribano P. 
Measurement of pleural pressure during therapeutic thoracentesis. 
Am J Respir Crit Care Med. 2000;162(4 Pt 1):1534-8. DOI: 10.1164/
ajrccm.162.4.9907047 PMID: 11029373 
20. Feller-Kopman D, Walkey A, Berkowitz D, Ernst A. The relationship 
of pleural pressure to symptom development during therapeutic 
thoracentesis. Chest. 2006;129(6):1556-60. DOI: 10.1378/chest.129.6.1556 
PMID: 16778274