Management of the Second Episode of SpontaneousPneumothorax.docx
1. Management of the Second Episode of Spontaneous
Pneumothorax: A Decision Analysis
Pierre-Emmanuel Falcoz, MD, Christine Binquet, MD, François
Clement, MD,
Djamel Kaili, MD, Catherine Quantin, MD, PhD, Sidney
Chocron, MD, PhD, and
Joseph-Philippe Etievent, MD
Department of Thoracic and Cardiovascular Surgery, Jean-
Minjoz Hospital, Besançon, Department of Biostatistics,
University
Hospital, Dijon, France
Background. Optimal management for patients pre-
senting a second episode of spontaneous pneumothorax
remains controversial. The aim of this study was to
compare two possible treatment strategies, video-assisted
thoracic surgery (VATS) and conservative management,
in order to assess which of the two was better adapted for
the treatment of the second episode of spontaneous
pneumothorax.
Methods. The authors propose a decision analytic
model including a cost-effectiveness study to compare
two clinical strategies: VATS (reference strategy) and
conservative management (alternative strategy). Data
were obtained from a Medline search for English lan-
guage articles and cost estimates were derived from the
financial and public health departments of our hospital.
The model was analyzed to determine the baseline strat-
egy leading to the highest expected effectiveness and the
lowest expected cost.
3. changed since the early 1990s, and video-assisted tho-
racic surgery (VATS) has set a new standard of excellence
for treating the second episode of SP [3–5].
Nevertheless, there is still controversy as to what the
best strategy is for a patient presenting a second episode
of SP. The answer to this question remains unclear due to
the lack of controlled clinical trials comparing the two
possible treatment strategies. We propose a decision
analytic model to examine this clinically important issue.
The aim of this study was to compare two possible
treatment strategies, VATS and CM, in order to assess
which of the two was better adapted for the treatment of
the second episode of SP.
Material and Methods
The Model
This study was conducted using a decision analysis
design. Decision analysis is a quantitative method for
synthesizing data from numerous sources to evaluate
treatment alternatives [6]. All decision analyses involve
the following basic components: the alternative strategies
and potential outcomes associated with each strategy are
specified in the decision model; the probabilities for each
of these outcomes are estimated from the most appropri-
ate available data and assigned to each decision point in
the model; and an analysis is performed to calculate the
expected value of each treatment alternative. By calculat-
ing the expected value, a favored strategy is identified.
All analyses were performed with Data version 3.5 (Tree-
Age Software Inc, Williamstown, MA), a decision analy-
Accepted for publication June 3, 2003.
5. In the present study, the outcomes of each strategy
were examined both in terms of effectiveness and cost. By
performing a cost-effectiveness analysis, we obtained a
more integrated view of the decision-making issue. Thus,
the model was analyzed to determine the baseline strat-
egy that leads to the highest expected effectiveness and
lowest expected cost.
The financial impact of the management of the second
episode of SP may be considered from different perspec-
tives, for example: the physician’s time or health-care
costs. Our model looks at financial impact from the
national health insurance perspective. Because it was not
possible to determine real costs, only direct costs were
taken into account. No attempt was made to include
noninstitutional costs, either direct or indirect, born by
the patients and their families or by society.
Assumptions
In designing the decision tree, several assumptions were
made in order to simplify the analysis. Complications
that followed an episode of SP were categorized into
three groups, regardless of the chosen treatment strat-
egy: short-term (less than 1 month), medium-term (less
than 3 months), and long-term (less than 2 years). All
potential complications were considered either as imper-
fect results or major complications. Imperfect results
were: minor air leak, pleural effusion, incomplete reex-
pansion of the lung (failing pleurodesis), and short-term
ipsilateral recurrent pneumothorax. Major complications
were: hemothorax or pleural infection following surgery
or chest tube insertion, prolonged air leak, and middle-
and long-term ipsilateral recurrent pneumothorax. For
each VATS, the probability of conversion to thoracotomy
was taken into account.
6. Utility and Probabilities of Chance Events
The concept of utility is a measure of a decision maker’s
relative preference for an outcome state. Each of the
health states at the terminal nodes of the decision tree,
which represent the final outcomes, are thus assigned a
utility value that quantifies preferences for these states
[7]. In the context of the present decision tree, the final
outcomes under study were either definitive resolution
or ensuing complications. They were estimated over a
2-year period because most recurrences occur during the
first 2 years after the initial pneumothorax [8]. The utility
of a patient having a definitive resolution, which is the
optimal outcome, was assigned a value of 100. The utility
of a patient experiencing a course with ensuing compli-
cations was assigned a value of 0.
Table 1 summarizes the main data probabilities and
estimates of their values used in the decision analysis.
Fig 1. Decision trees representing the choice of
management strategies for the second episode
of spontaneous pneumothorax. The two clinical
strategies to be chosen from are represented at
the square decision node of the first tree (A).
The probabilities and estimates of their values
are listed in Table 1. � � the choice between
strategies (decision node); E � the occurrence
of chance events (chance node); and � � a
logic check in the simulation (terminal node).
(CM � conservative management; VATS �
video-assisted thoracic surgery.)
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These values are based on a critical review of the avail-
able literature regarding SP management. We performed
a systematic Medline search for all English language
articles dating from 1966 and falling under the medical
subject headings “spontaneous pneumothorax,” “pleural
drainage,” “thoracoscopy,” and “video-assisted thoracic
surgery” alone and in combination with the terms “ran-
domized controlled trials,” “meta-analysis,” and “guide-
lines.” This survey of the medical literature was done to
obtain a baseline value and a range for all variables of
interest. Decision tree values were assigned by applying
critical appraisal criteria (methodologic quality, largest
8. number of cases reported, most recent information, and
relevance to our study population) in the articles re-
trieved [9].
Cost Data
Costs, expressed in euros (€), were provided by the
financial department of our hospital. They are those of
the actual procedures for pneumothorax. The total cost of
both surgical and anesthetic procedures was taken into
account. The anesthetic cost was €188.1 for VATS and
thoracotomy, and €20.9 for CM. The surgical cost was
€418 for VATS and thoracotomy, and €41.8 for CM. The
cost per day of hospitalization was €584.19 (ranging from
€416.93 to €724.03).
The public health department provided the mean and
standard deviation of length of stay over a 5-year period
(1998 to 2002) of 133 patients suffering a second episode of
SP: 5.4 � 1.8 days for VATS (n � 82 patients), 10.5 � 3.5
days for thoracotomy (n � 17 patients), and 9.4 � 6.9 days
for CM (n � 34 patients).
Sensitivity Analysis
The stability of the results obtained from the model for
mean probabilities and costs was assessed through sen-
sitivity analysis. Sensitivity analysis is a method of vary-
ing probabilities over a defined range to determine how
the optimal choice would change if the value of a chance
event changed [10]. Sensitivity analysis can be performed
on individual probabilities (one-way sensitivity analysis)
or by varying two probabilities at the same time (two-way
sensitivity analysis). One-way sensitivity analysis was
performed for each probability in the decision tree, and
the value at which the optimal strategy changed (thresh-
old value) was identified. Two-way sensitivity analysis
was performed for all probabilities found to be relevant
9. in one-way sensitivity analysis.
Results
Baseline Analysis
The baseline analysis (Table 2) was based on the assump-
tions described above and used the aforementioned
probabilities (Table 1), costs estimates, and formalized
utility scores.
Conservative management offered a slight increase in
expected effectiveness as compared to VATS. The incre-
mental effectiveness, obtained by calculating the differ-
ence between the expected effectiveness values associ-
ated with the two strategies, was 0.06. This value
indicates that CM would have provided six additional
recoveries for 10,000 patients. Similarly, when focusing
on the hierarchical choice between VATS and thoracot-
omy, our analysis suggests that VATS would have pro-
vided 95 additional recoveries for 10,000 patients under-
going surgery.
The strategy producing the lowest expected cost was
VATS. The cost-effectiveness ratio for one recovery was
€44 for VATS and €75 for CM. The incremental cost-
effectiveness ratio was €57,750 for CM, which means that
the cost of one additional recovery by CM, when com-
pared to VATS, was €57,750.
Sensitivity Analysis
Because the probabilities for the various outcomes used
in this analysis could conceivably vary, sensitivity testing
was performed to assess the validity of the conclusions
over a wide range of probabilities.
In terms of effectiveness, the sensitivity analysis dem-
10. Table 1. Literature-Based Range of Probabilities Comparing
VATS With Conservative Management
Parameter
Baseline
Value
(%)
Sensitivity
Analysis
Range (%) References
Definitive resolution after
CM
70 48 – 84 [11a–13]
Complications after CM 30 16 –52 [11a, 14a]
Imperfect results 27 5–50 [15a, 16]
Major complications 3 0 –3 [15a, 17, 18]
Definitive resolution after
VATS
90 86 –98 [11a, 12, 14a]
Complications after
VATS
10 5–10 [11a, 19]
Imperfect results 7.5 0 –22 [20 –22]
11. Major complications 2.5 0 –24 [20, 21, 23]
Conversion to
thoracotomy
7 2–10 [12, 19]
Definitive resolution after
thoracotomy
99 99 –99.5 [14a, 24]
a Review articles compiling different studies.
The baseline value is the best estimate for each probability
(average of the
results from the different studies to estimate the probability).
The range
reflects the lowest and highest estimates from the retrieved
studies.
CM � conservative management; VATS � video-assisted
thoracic
surgery.
Table 2. Summary of Baseline Results Comparing VATS
With Conservative Management
VATS CM
Effectiveness 99.93 99.99
Incremental effectiveness — 0.06
Cost (€) 4,347 7,536
Incremental cost (€) — 3,189
Cost-effectiveness ratio (€) 44 75
Incremental cost-effectiveness ratio (€) — 57,750
12. CM � conservative management; VATS � video-assisted
thoracic
surgery.
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onstrated consistent results and advocated CM as the
better of the two strategies regardless of the probability
concerned. Within the ranges tested, the different vari-
ables in the model influenced the weight of VATS, but
13. did not change the preferred strategy. Examples are
given in Figure 2, which illustrates the effect of definitive
resolution after VATS (Fig 2A) and the effect of definitive
resolution after CM (Fig 2B) on the two management
strategies.
In terms of costs, the sensitivity analysis was insensi-
tive to changes in the estimate of the values, except for
length of stay, and favored VATS over CM for the
treatment of the second episode of SP. One-way sensi-
tivity analysis for VATS did not reveal any threshold (Fig
2C). One-way sensitivity analysis for CM revealed that
the threshold value at which strategies were equivalent
for length of stay was 4.9 days (Fig 2D). Two-way sensi-
tivity analysis indicated how the optimal strategy
changed as the length of stay related to each strategy
varied (Fig 3). A combination of these two lengths of stay
corresponds to a point on the graph. For any combina-
tion, if the point lies in the black area, VATS is the
optimal choice and in the white area, it is CM. The
boundary line between the two areas represents a series
of threshold values at which the two strategies yield an
equivalent outcome.
Comment
In the field of SP, a consensus emerging in the literature
indicates clearly what to do for an initial episode of SP
(CM) or the third episode (VATS). Conversely, the need
for and method of promoting adequate pleural symphy-
sis at the second episode has given rise to great contro-
versy. The usefulness of VATS as opposed to CM for the
second episode of SP remains controversial. Although
some centers recommend VATS [5, 19, 25], others, who
report a high recurrence and complication rate and
14. recommend more caution [1, 2], advocate CM. Clearly
there is still much debate over which approach is more
appropriate in any given patient. The British Thoracic
Society [26] and the American College of Chest Physi-
cians [27] have both published guidelines for the imme-
diate and subsequent management of patients with SP.
On one hand, the guidelines of the British Thoracic
Society make no distinction between patients with first
and recurrent episodes of SP. On the other hand, most of
the panel members of the American College of Chest
Fig 2. One-way sensitivity analysis demonstrating the effect of
different variables in terms of effectiveness and cost. The upper
graphs illustrate
the effect of definitive resolution after VATS (A) and after CM
(B) on expected effectiveness. The lower graphs illustrate the
effect of length of
stay for VATS (C) and for CM (2 d) on expected cost (D). The
threshold value at which strategies were equivalent was 4.9
days. ■ � CM; E
� VATS. (CM � conservative management; T � threshold
value; VATS � video-assisted thoracic surgery.)
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Physicians recommend VATS at the second episode.
Because a consensus has not been clearly established
from these basic recommendations, even among experts,
and given the lack of controlled clinical trials, we decided
to address this controversial question using formal deci-
sion analysis.
The use of decision analysis in surgery is gaining
interest [28, 29]. In a complex decision-making environ-
ment, where medical practice is influenced by published
clinical trials, consensus statements and detailed formal
examination of procedures, physicians may perform in-
adequately in establishing the standard of care if they
rely only on their clinical judgment based uniquely on
past experience. Since none of us can intuitively estimate
probabilities accurately, decision analysis becomes use-
ful when it is desirable to compare alternative treatment
strategies quantitatively. Nevertheless, this method has
its own limitations. Some of the limitations of our deci-
sion analysis imposed by the assumptions and tree
structure deserve mention. First, the possibility of having
to perform a thoracotomy was taken into account. We
16. decided not to exclude this option from our model in
order to leave the surgeon the choice of which technique
he judged the more appropriate to treat a major compli-
cation (eg, hemothorax). Second, we used estimated costs
of the actual procedures for SP to compare the cost of the
two strategies. The ideal approach would have been to
look at the real cost of each procedure and model those
costs explicitly. Such a cost analysis was beyond the
scope of the current work and not really justified in a
comparative study.
Despite the above limitations from the standpoint of
baseline probabilities, our analysis reveals only a slight
advantage in terms of expected effectiveness for CM. The
difference we take into account in our analysis between
CM and VATS (incremental effectiveness value of 0.06)
may be somewhat disturbing to readers. This value is
rather small and, consequently, the difference between
the two strategies is only slight. However, from the
perspective of decision analysis, it is not the quantity but
the sense of the difference between two treatment strat-
egies that guides the choice of the decision [6]. It is
especially noteworthy that sensitivity analysis did not
have a significant impact on the baseline results. In the
absence of variation in the sensitivity analysis, the inter-
pretation of results can be considered reliable and robust.
In addition, although the primary goal of this study was
to compare two possible treatment strategies, VATS and
CM, in the management of a second episode of SP, the
present model also provides information for a hierarchi-
cal choice between VATS and thoracotomy, keeping in
mind that thoracotomy is often reserved for patients with
technically more complex problems. Be that as it may,
VATS would have provided 95 additional recoveries for
10,000 patients undergoing surgery for a second episode
17. of SP. Hence, it should be considered whenever surgery
is necessary. This finding has already been reported in
many studies dealing with VATS versus thoracotomy for
SP [19, 24, 27], especially in primary SP [25].
In the present study, VATS was the strategy found to
produce the lowest expected cost. This result was prin-
cipally due to a shorter “cost-consuming” length of stay.
Schramel and colleagues [30] highlighted this in a cost
analysis study comparing VATS and CM. The length of
stay for VATS was 5.4 � 1.8 days in our study, 6.9 days
(ranging from 2 to 15 days) in Crisci and Coloni’s study
[31], whereas it was 11 � 4 days in Schramel associates’
study [30] and 2.9 � 0.9 in Hazelrigg and coworkers’
study [32]. In considering the discordance in the length of
stay between these studies (postoperative length of stay
for European patients is typically much longer than for
US patients) it was necessary to examine the impact on
the results of these variations in duration. By varying the
length of stay for CM, the one-way sensitivity analysis
revealed that the threshold value at which outcomes
were equivalent was 4.9 days. CM should be preferred
below this threshold value, and VATS above it. The
two-way sensitivity analysis indicates the preferred strat-
egy in function of the mean length of stay (Fig 3). The
shorter the length of stay for VATS, the smaller the area
in which CM was the optimal strategy. Therefore, de-
pending on the length of stay in a given institution, the
clinician may well choose one strategy or the other.
Cost effectiveness is becoming more and more impor-
tant in the choice of treatment. The incremental cost-
effectiveness ratio found in our study was approximately
€58,000 for CM. Deciding whether a strategy is cost
effective is a subjective interpretation of the cost-
effectiveness ratio. Although there is no absolute cutoff
18. Fig 3. Two-way sensitivity analysis of the relation between the
length of stay for VATS and CM that illustrates how the optimal
strategy changes according to the length of stay when all other
prob-
abilities are maintained at the baseline. The black area indicates
VATS as the preferred strategy; the white area indicates CM as
the
preferred strategy. The base-case scenario, indicated by a star,
is
defined by a mean length of stay of 5.4 days for VATS and 9.4
days
for CM. (CM � conservative management; VATS � video-
assisted
thoracic surgery.)
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level, there is a consensus that a cost-effectiveness ratio
under the accepted limit of €50,000 corresponds to a
cost-effective strategy [33]. Hence, CM is definitely not
cost effective for the management of the second episode
of SP in our study.
In conclusion, the results we obtained using decision
analysis for the management of the second episode of SP
reveal that VATS offers substantial savings in cost for
only a slight decrease in effectiveness when compared
with CM. Institutions whose probabilities reflect those
presented in our analysis may well want to consider
performing VATS in all patients undergoing a second
episode of SP. Nevertheless, further clinical trials should
help to validate the formal analytic results found in this
study.
The authors thank Nancy Richardson-Peuteuil for her editorial
assistance, and Catherine Lejeune for her helpful comments.
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Management of the Second Episode of Spontaneous
Pneumothorax: A Decision AnalysisMaterial and MethodsThe
ModelAssumptionsUtility and Probabilities of Chance
EventsCost DataSensitivity AnalysisResultsBaseline
AnalysisSensitivity AnalysisCommentReferences
Sheet1Data for Coursework Part 2 - Question 2Month
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![Results. Conservative management offered a slight
advantage in expected effectiveness value (99.99 vs 99.93
for VATS). VATS produced the lowest expected cost
(€4347 vs €7536 for conservative management). The incre-
mental cost-effectiveness ratio was €57,750. Within the
ranges tested, the sensitivity analysis presented consis-
tent results in terms of effectiveness and advocated
conservative management as the best strategy. In terms of
cost, with the exception of length of stay, the sensitivity
analysis was insensitive in estimating the different prob-
abilities, and favored VATS over conservative
management.
Conclusions. In the management of the second episode
of spontaneous pneumothorax, VATS offers substantial
savings in cost for only a slight decrease in effectiveness,
when compared with conservative management.
(Ann Thorac Surg 2003;76:1843– 8)
© 2003 by The Society of Thoracic Surgeons
Spontaneous pneumothorax (SP) is a disabling disor-der that
may present either in young and otherwise
healthy patients (primary pneumothorax) or as a compli-
cation of an underlying lung disease (secondary pneu-
mothorax). Since the 1960s clinical trials have led to
opposing recommendations for management of SP, an
issue still under debate particularly for the management
of the second episode.
Conservative management (CM) has long been the
generally accepted treatment strategy for the second
episode of SP (pleural drainage and a “wait and see”
approach) [1, 2]. Thanks to advances in thoracoscopic
instrumentation (such as optics, instruments, and endo-
scopic staplers) treatment strategy has progressively](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)