FEATURED NEW INVESTIGATOR
Preoperative use of incentive spirometry does not
affect postoperative lung function in bariatric surgery
DAVIDE CATTANO*, ALFONSO ALTAMIRANO, ANDREA VANNUCCI, VLADIMIR MELNIKOV,
CHELSEA CONE, and CARIN A. HAGBERG
HOUSTON, TEX AND ST. LOUIS, MO
Morbidly obese patients undergoing general anesthesia for laparoscopic bariatric
surgery are considered at increased risk of a postoperative decrease in lung function. The purpose of this study was to determine whether a systematic use of incentive
spirometry (IS) prior to surgery could help patients to preserve their respiratory function better in the postoperative period. Forty-one morbidly obese (body mass index
[BMI] . 40 kg/m2) candidates for laparoscopic bariatric surgery were consented in
the study. All patients were taught how to use an incentive spirometer but then
were randomized blindly into 2 groups. The control group was instructed to use the
incentive spirometer for 3 breaths, once per day. The treatment group was requested
to use the incentive spirometer for 10 breaths, 5 times per day. Twenty experimental
(mean BMI of 48.9 6 5.67 kg/m2) and 21 control patients (mean BMI of 48.3 6 6.96 kg/
m2) were studied. The initial mean inspiratory capacity (IC) was 2155 6 650.08 (SD) cc
and 2171 6 762.98 cc in the experimental and control groups, respectively.
On the day of surgery, the mean IC was 2275 6 777.56 cc versus 2254.76 6 808.84
cc, respectively. On postoperative day 1, both groups experienced a significant
drop of their IC, with volumes of 1458 6 613.87 cc (t test P , 0.001) and 1557.89 6
814.67 cc (t test P , 0.010), respectively. Our results suggest that preoperative
use of the IS does not lead to significant improvements of inspiratory capacity and
that it is a not a useful resource to prevent postoperative decrease in lung function.
(Translational Research 2010;156:265–272)
Abbreviations: ABG ¼ arterial blood gases; BiPAP ¼ bilevel positive airway pressure; BMI ¼ body
mass index; CPAP ¼ continuous positive airway pressure; FEV1 ¼ forced expiratory volume in 1 s;
FiO2 ¼ fraction of inspired oxygen; FRC ¼ functional residual capacity; IC ¼ inspiratory capacity;
IS ¼ incentive spirometry; OHS ¼ obesity hypoventilation syndrome; PACU ¼ postanesthesia
care unit; PEEP ¼ positive end-expiratory pressure
*
Davide Cattano, MD, PhD, is an Assistant Professor in the Department of Anesthesiology, University of Texas Medical School at Houston – Home. His article is based on a presentation given at the
Combined Annual Meeting of the Central Society for Clinical Research and Midwestern Section American Federation for Medical Research held in Chicago, Ill, April 2010.
From the Department of Anesthesiology, The University of Texas
Health Science Center Houston, School of Medicine, Houston, Tex;
Department of Anesthesiology, Washington University School of
Medicine, St. Louis, Mo.
Submitted for publication May 20, 2010; revision submitted August 9,
2010; accepted for publication August 12, 2010.
Reprint requests: Davide Cattano, MD, PhD, Department of Anesthesiology, Medical Director Preoperative Anesthesia Clinic, School of
Medicine, UTHSC-Houston, 6431 Fannin, MSB 5.020, Houston,
TX 77030; e-mail: davide.cattano@uth.tmc.edu.
1931-5244/$ - see front matter
Ó 2010 Mosby, Inc. All rights reserved.
doi:10.1016/j.trsl.2010.08.004
265
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Cattano et al
AT A GLANCE COMMENTARY
Cattano D, et al.
Background
Morbidly obese patients undergoing bariatric surgery are at higher risks for perioperative pulmonary atelectasis and impaired gas exchange.
Muscle paralysis and intraoperative mechanical
ventilation (often with high Fi02, insufficient levels
of positive end-expiratory pressure, and erratically
applied alveolar recruiting maneuvers) can
aggravate preexisting deficiencies in respiratory
mechanics.
Translational Significance
The use of preoperative incentive spirometry (IS)
was proposed in this clinical investigation with
the speculation that encouraging morbidly obese
patients to breathe to total lung capacity and,
therefore, opening collapsed alveoli would minimize postoperative respiratory dysfunction. Because of the differences in previous studies, the
therapeutic value of preoperative IS has not yet
been fully understood.
The prevalence of obesity is high in the United States,
exceeding 30% in most age and sex groups.1 Morbid
obesity affects millions of Americans that, in association with obesity, frequently carry several additional
medical problems such as type 2 diabetes mellitus, gastroesophageal reflux disease, arthritis, heart disease, and
importantly for anesthesiologists, pulmonary diseases
such as obesity hypoventilation syndrome (OHS).2
OHS is a term used to describe the pulmonary state of
patients with obesity, chronic hypercapnia, and sleepdisordered breathing.3 It is most common in patients
with a body mass index (BMI) $40 kg/m2 (defined by
the World Health Organization as morbidly obese4)
and often involves pulmonary hypertension and restrictive lung disease.2
Morbidly obese patients undergoing bariatric surgery
are at higher risks for perioperative pulmonary complications such as atelectasis and impaired gas exchange.5
Muscle paralysis and intraoperative mechanical ventilation (often with high Fi02, insufficient levels of positive
end-expiratory pressure [PEEP], and erratically applied
alveolar recruiting maneuvers) can aggravate preexisting deficiencies in respiratory mechanics.6 The insufflation of pneumoperitoneum and postural changes
associated with bariatric procedures may impair respiratory function and gas exchange further both intraoperatively and postoperatively.7 In fact, hypoxemia is
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November 2010
a common postoperative complication in these patients
even in the absence of preoperative obstructive pulmonary symptoms, indicating a need for routine positive
pressure treatment.8
Postoperative chest physiotherapy in the form of mechanical breathing devices such as continuous positive
airway pressure (CPAP), bilevel positive airway pressure (BiPAP), and incentive spirometry (IS) have been
introduced to prevent pulmonary complications after
bariatric surgery. The use of CPAP immediately after
extubation has been shown to reduce the loss of significant lung volumes after surgery, which may be an additional intervention in risk minimization.9 However,
many surgeons caution the use of positive pressure airway ventilation as they are concerned about anastomosis tension and sutures breakage.
IS uses a device that allows the patient to mimic natural yawning or sighing by having them take slow, deep
breaths while sustaining maximal inspiration. Studies
directed at combating pulmonary risk in the postoperative period demonstrate that lung volume expansion
techniques, such as aggressive IS and early ambulation,
are useful in preventing respiratory complications,10,11
obviating the need for positive pressure techniques
such as BiPAP and CPAP that can be labor intensive
and expensive to implement.
Still, several studies suggest that IS is taught inconsistently (a brief explanation in the preoperative clinics;
the brochure is provided. Instructions are given to bring
in the spirometer the day of surgery, yet no education is
provided regarding its use, and then it likely is used inadequately by patients) and the effects of IS may be
measured inconsistently because of the different variables in each clinical trial.10,12-14 All of these studies
looked at the effect of prophylactic respiratory
physiotherapy on several measures of postoperative
outcome, but none focused on the modalities of IS use.
Our hypothesis was that a systematic use of IS for at
least 3 days prior to surgery could increase the preoperative inspiratory capacity of our patients on the day of
surgery and also could result in a smaller decrease in
the postoperative inspiratory lung volume of bariatric
patients.
Therefore, our primary goal was to determine
whether IS could lead to improved preoperative respiratory mechanics, as assessed by measuring inspiratory
lung volumes postoperatively. The underlying assumption was that optimizing and preserving the respiratory
function can result in better perioperative oxygenation
and in a lower incidence of pulmonary complications
in this high-risk population and that a formal preoperative program of IS utilization could help the patient to
familiarize themselves with the device and possibly to
appreciate the benefits, resulting in a better utilization
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Volume 156, Number 5
and compliance in the postoperative period with
minimal reliance on the hospital staff support. The
secondary aims of our study were to assess postoperative respiratory complications’ rate, patients’ satisfaction with IS treatment, and patient compliance
(indirect assessment).
METHODS
After approval from the local institutional board, this
study was registered at www.clinicaltrials.gov.
(NCT01004146), and 41 ASA 1–3 bariatric patients
were enrolled and consented in this study. All patients
enrolled presented to the preoperative anesthesia clinic
for evaluation at least 3 days prior to their procedure
date. Morbid obesity with a BMI $40 kg/m2 was a prerequisite for inclusion in the study. Patients were
excluded if they had both current symptoms of obstructive sleep apnea and actively were being treated with
CPAP during their sleep.
After written informed consent, patients received an
incentive spirometer (Cardinal Health Inc., Dublin,
Ohio) and were randomized to the experimental group
or the control group. Patients assigned to the experimental group were instructed to use the spirometer by inhaling as slowly and deeply as possible in a set of 10 times
and to repeat the process at least 5 times every day until
the day of surgery. Patients assigned to the control group
were educated on the proper technique of using the incentive spirometer and were instructed to use it for
3 breaths once per day to become able to use the device
properly and consistently.
During the preoperative visit, all patients were instructed on how to use the spirometer effectively. The
principal investigator made sure that they all could use
it properly after instruction. The IS volume (best out of
2 attempts) achieved was documented, as well as the relevant pulmonary history, planned date of surgery, type of
the bariatric surgical procedure, and their demographic
information such as age, sex, height, and weight; and
the BMIIS volume always was measured first in the sitting position and then in the supine position.
All patients were given a log sheet (included in the
manufacturer’s packaging) to record their IS volumes
while at home. They were requested to record the volume inspired on the third attempt in each cycle of using
the spirometer. For example, patients in the experimental group recorded at least 5 attempts per day as they
were instructed to repeat 5 cycles of 10 attempts per
day. These log sheets were collected on their arrival to
the day surgery unit on the day of the operation, and
each patient was interviewed as to their use of the spirometer. Room air SpO2, baseline heart rate, respiratory
rate, and IS volume (best out of 2 attempts) achieved all
Cattano et al
267
were documented. The level of compliance with the assigned protocol was measured objectively by reviewing
the lung volumes recorded on the patient log sheet and
by reviewing the patient questionnaire regarding improvement in breathing.
A standard intravenous induction of general anesthesia
was achieved with full muscle relaxation. Intraoperatively, SpO2, tidal volume, peak airway pressures, ventilation modality, PEEP applied via ventilator, and any
intraoperative events (bucking, coughing, desaturation,
and evidence of aspiration) all were documented. All patients in our study were reversed fully prior to extubation.
Invasive blood pressure monitoring was established after
the induction of general anesthesia and endotracheal intubation. The ventilatory support during the bariatric procedures is standardized to 10 mL/kg to 12 mL/kg (ideal body
weight), 7 cmH2O to 10 cmH2O of PEEP is used for patients with a BMI below or equal and above 50, respectively, and fraction of inspired oxygen (FiO2) is
maintained at 60%. Typically, no recruiting maneuvers
are performed after endotracheal intubation unless peripheral oxygen saturations levels are unexpectedly below
97%. Extubation is perfomed with patient in a 30-degree
semirecumbent position and with 100% FiO2.
After the operation, the patients to be discharged on
the same day were approached in the postanesthesia
care unit (PACU) and requested to use the spirometer
again. The volume (best out of 2 attempts) was recorded
together with the same vital signs recorded preoperatively. Patients who were admitted to the hospital were
requested to use the spirometer again on postoperative
day 1. The largest IS volume (out of 2 attempts) was recorded in addition to their vital signs. Additionally, any
postoperative complications were noted (fever, atelectasis on chest x-ray, postoperative pneumonia, desaturation episodes, shortness of breath, and cough), and
any interventions undertaken to improve respiratory status also were documented (nebulizer/inhaled medication use, CPAP, BiPAP, intubation, and respiratory
physiotherapy). These items were assessed daily during
the first 3 postoperative days. Patients also were given
a questionnaire to report notes on the subjective improvement with their breathing in the preoperative period, as well as convenience of use of the device, level
of pain, ease of breathing on day 1 postoperatively,
and, finally, their overall evaluation regarding their prescribed usage of IS.
Measurements. An IS calibration was performed randomly before the start of this study on 3 incentive spirometers and compared with spirometry. A difference
of ,5% was noted for volumes greater than 3 L, 10%
for volumes of 1 L to 3 L, and between 10% and 15%
for volumes ,1 L.
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Cattano et al
For all patients enrolled in the study, IS volumes
achieved were recorded for the best out of 2 attempts
in both the sitting and the supine positions during the
anesthesia clinic visit, preoperatively in the day surgery unit, postoperatively in the PACU, and on postoperative day 1. Intraoperative data collected included
length of surgery, intraoperative SpO2, ventilatory modality, application of PEEP, intraoperative tidal volume, intraoperative peak airway pressures, and any
adverse intraoperative events. Postoperative data collected included vital signs in PACU and postoperative
day 1, any postoperative pulmonary complications (as
outlined previously), and any pulmonary interventions
undertaken (as outlined previousy) in the first 3 postoperative days. The patient questionnaire included several questions that the patient had to rate on a Liekert
scale (eg, 1 5 highly improved to 5 5 no improvement on their breathing progression preoperatively using IS, and 1 5 no pain to 5 5 severe on level of pain
postoperatively).
Statistical analysis. A power analysis (a 5 0.05;
b 5 0.20) to estimate the sample size was conducted
considering a clinically significant difference of 15%
in inspiratory volumes, based on mean and standard deviation values reported in a previous study.15,16
A minimum of 21 patients per group was deemed
necessary. Data were compared between the groups
using the t test for unpaired data, analysis of
correlation, Pearson’s c2 test, or Fisher exact test
when appropriate with the analysis of association.
Results were presented as means with standard
deviations and confidence intervals; P , 0.05 was
considered statistically significant.
RESULTS
Forty-one ASA 1–3 patients consented to participate
in the study. These patients were randomized into
2 groups—the control (21) and the experimental (20).
Four of these patients were discharged home on the
same day of surgery. As a result, postoperative day 1
data and analysis was performed on 37 patients (control
n 5 19; experimental n 5 18) only. The physical and
clinical characteristics of the patients in the 2 groups
were similar, as indicated in Table I. Most patients in
both groups were middle-aged women. Patients received 1 of 3 procedures, including laparoscopic small
pouch gastric bypass, laparoscopic gastric sleeve, or
laparoscopic gastric banding. No significant differences
were present in BMI, age, or length of preoperative IS
use between the 2 groups. None of the patients experienced intraoperative desaturation or required arterial
blood gas monitoring for abnormal peripheral oxygen
saturation.
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November 2010
The use of preoperative IS before the scheduled
surgery was similar in both groups—control (7.2 6
4.91 days) and experimental (6.4 6 3.30 days)
(P , 0.330). The inspiratory capacity (IC) volumes
were comparable in the preoperative anesthesia clinic
for both groups (control 5 2171.43 6 762.98; experimental 5 2155 6 650.08) (P , 0.941). Figure 1 illustrates that a significant decrease occurred in IC in
both groups when comparing the day of surgery volume (control 5 2254.76 6 808.84, experimental 5
2275 6 777.56) with the postoperative day 1 volume
within each group (control 5 1557.90 6 814.67, experimental 5 1458.33 6 613.87), (P , 0.010 and
P , 0.001, respectively). In addition, the 2 groups
were compared with each other, and no significant
difference (P , 0.935) was found in the day of surgery IC volumes (as noted previously). The postoperative day 1 IC volumes (as mentioned earlier) also
were compared between the control and experimental
groups, and again, no significant difference
(P , 0.676) was found between the 2 groups. Clinical evaluation on postoperative day 1 revealed no pulmonary complications for either group.
Univariate analysis of different variables did not detect any difference between the 2 groups or any correlation with postoperative IC lung loss in a particular
gender, length of IS use, length of surgery, type of surgery, or pain score. However, the BMI and the preoperative ratio between the actual volume and the ideal
volume showed a trend toward an inverse relationship,
but the P level was not statistically significant.
All patients were considered together regardless of
their study assignment and were subdivided into 2 categories based on their BMI (BMI ,40 mg/kg2 to
49.9 mg/kg2 and BMI $50 mg/kg2). The preoperative
day of surgery IC was compared with the postoperative
day 1 IC. When evaluating the group with a BMI ,40
mg/kg2 to 49.9 mg/kg2, the IC on the day of surgery
was 2214 6 775 cc, which decreased to 1532.61 6
688 cc displaying a 31% (P , 0.002) reduction,
whereas the group with a BMI $50 mg/kg2 exhibited
a decrease of 36% (P , 0.008) when their IC decreased
2312.50 6 819 cc on the day of surgery to 1471.43 6
784 cc on postoperative day 1.
Figure 2 exhibits the IC separately in both the control
and the experimental groups when each is subdivided
into the following categories: BMI ,40 mg/kg2
to 49.9 mg/kg2 (23 patients) and BMI $50 mg/kg2
(14 patients). When separately evaluating the preoperative day of surgery IC and the postoperative day 1 IC in
both groups with a BMI ,40 mg/kg2 to 49.9 mg/kg2, the
IC in the control group (12/23 patients) was reduced
from 2488.46 6 815 cc to 1854.17 6 822 cc, respectively, decreasing by 25% (P , 0.070). The IC in the
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Volume 156, Number 5
Cattano et al
269
Table I. Patient demographics, length of preoperative, IS use, surgical procedures, and inspiratory vital
capacity in both groups. No significant differences were found in any the data on this table
Data
Control group (n 5 21)
Experimental group (n 5 20)
Gender
Age (year)
Weight (kg)
Height (m)
BMI (kg/m2)
Length of preoperative IS (d)
Gastric bypass (n)
Gastric sleeve (n)
Gastric lap band (n)
Clinic lung volume (sitting) (cc)
DOS lung volume (sitting) (cc)
POD lung volume (sitting) (cc)
81% female
45.0 6 12.4
136.15 6 19.38
1.68 6 0.09
48.3 6 6.9
7.2 6 4.91
16
3
2
2171.43 6 762.98
2254.76 6 808.84
1557.90 6 814.67
90% female
45.2 6 12.3
134.95 6 22.53
1.65 6 0.07
48.9 6 5.7
6.4 6 3.30
14
2
4
2155.00 6 650.08
2275.00 6 777.56
1458.33 6 613.87
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
Abbreviations: NS, not significant; DOS, day of surgery; POD, postoperative day 1.
experimental group (11/23 patients) decreased from
1958.33 6 656 cc on the day of surgery to 1181.82 6
197 cc on postoperative day 1, showing a 40% reduction
(P , 0.002). The groups with a BMI $50 mg/kg2 had
the opposite effect in which the IC in the control group
(7/14 patients) decreased from 1875 6 681 cc on the
day of surgery to 1050 6 525 cc on postoperative day
1, a 44% reduction (P , 0.020). The IC in the experimental group (7/14 patients) decreased by 31%
(P , 0.052), starting from 2750 6 732 cc on the day
of surgery and decreasing to 1892.86 6 802 cc on
postoperative day 1.
A multivariate analysis was performed in which
10 patients exhibiting $3000 cc IC volume in the initial
Fig 1. IC volumes measured preoperatively (day of surgery) and postoperatively in patients separated by their assigned group. Both the experimental and the control groups showed a significant difference in
IC lung volume as shown by the (*). The percentage loss for the control group was 31%, and for the experimental group, it was 36%. No
significant differences were found between the control and the experimental groups when comparing day of surgery and postoperative day
1 IC volumes as shown by the 2 solid connecting bars. (Color version
of figure is available online.)
preoperative anesthesia clinic assessment were removed, and the 31 patients left were organized within
their respective groups according to an actual/ideal volume ratio of 0.70. The actual/ideal volume ratio $0.70
decreased (from the preoperative anesthesia clinic to
postoperative day 1) by 29% (P , 0.009) and 37%
(P , 0.001) in the control (9 patients) and experimental
(10 patients) groups, respectively. In addition, both
groups with a ratio ,0.70 also exhibited a similar outcome, with the control group (6 patients) decreasing
Fig 2. Preoperative and postoperative IC volumes. The groups were
divided further by their BMI. The experimental group with
BMI .50 showed an improvement (31% vs 44%) of IC lung loss.
(Color version of figure is available online.)
270
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November 2010
Cattano et al
by 35% (P , 0.039) and the experimental group
(6 patients) decreasing by 21% (P , 0.017).
Patient questionnaires regarding IS use and breathing
improvement, as illustrated in Table II, revealed that
48% (10/21) of patients in the control group (3 breaths
once per day) described moderate-to-high improvement
in breathing after their preoperative use of IS. In the
experimental group (10 breaths 5 times per day), 45%
(9/20) of patients exhibited a moderate-to-high improvement in breathing. We also investigated the level of pain
through the questionnaire, and only 11% of patients in
both groups stated they were experiencing moderate
pain postoperatively the day after surgery (no patients
were in severe or intolerable pain at the time of the visit),
whereas the remaining patients were comfortable or
slightly in pain. Univariate analysis was performed on
both groups based on the patient’s subjective feeling of
improvement in breathing after IS usage. No absolute
or relative change was noted in lung volume in both
groups when comparing the IC from the clinic with the
day of surgery or when comparing the day of surgery
with postoperative day 1. None of the patients in both
groups had a SpO2 lower than 95% on postoperative
day 1 at the time of IS assessment (no significant difference between experimental vs control group).
DISCUSSION
The use of preoperative IS was proposed in this clinical investigation with the speculation that encouraging
morbidly obese patients to breathe to total lung capacity
and therefore opening collapsed alveoli would minimize postoperative respiratory dysfunction.
Because of the many differences in previous studies’
design and the etherogeneity of investigated popula-
tions, the therapeutic value of preoperative IS has not
yet been fully understood.11,17 Studies have been done
comparing the use of IS, CPAP, and a combination of
cough and deep breathing to prevent postoperative
pulmonary complications in patients undergoing upper
abdominal surgery.
Investigators comparing CPAP, IS, and the combination of cough and deep breathing have suggested that using IS or CPAP may be beneficial; however, CPAP may
increase mean functional residual capacity (FRC) more
rapidly in patients receiving the combination of IS or
cough and deep breathing. Nonetheless, no statistically
significant differences were found between the groups,
as was reported by Pasquina et al18 and in a recent review from the Cochrane review.14
Our results demonstrate that patients undergoing
a bariatric procedure do not benefit from the preoperative use of IS, as assessed with IS exercises performed
within the first 24 h after surgery, and in fact, a decrease
was noted postoperative lung volume.
We investigated whether this volume decline was related to preoperative inspiratory volume. To increase
the sensitivity of our post hoc analysis, we pooled together both groups, stratifying them by BMI (,50 or
$50). The preoperative IC volumes were not significantly different between the 2 BMI groups nor were
the postoperative volumes. This result is consistent
with the hypothesis, that both preoperative and postoperative IC not only are determined by patients’ BMI but
may be affected by other preoperative factors that we
did not consider in the present analysis.
Even if preoperative IS was not sufficient in our study
to prevent a decrease in IC postoperatively, it did not
lead to any complication, was not too consuming or expensive, and was well received by patients overall. We
Table II. Patient questionnaire responses for level of pain, feeling of breathing improvement, and patient
satisfaction with prescribed IS usage.*
Questionnaire patient response
Questions
Control (n) (%)
Experimental (n) (%)
How would you rate your level of
improvement in regard to breathing after
IS usage? (1–5)
What level of pain are you experiencing?
(POD) (1–5)†
10 (48%) Moderate/high improvement
5 (24%) Undecided
6 (28%) Little to no improvement
2 (11%) Moderate/severe pain
1 (,1%) Undecided
16 (84%) Little to no pain
1 (4%) Too much
15 (71%) Just right
3 (14%) Not enough
2 (10%) Undecided
9 (45%) Moderate/high improvement
5 (25%) Undecided
6 (30%) Little to no improvement
2 (11%) Moderate/severe pain
3 (1%) Undecided
13 (73%) Little to no pain
1 (5%) Too much
17 (85%) Just right
1 (5%) Not enough
1 (5%) Undecided
How would you rate the prescribed usage
of IS? (1–4)
*The responses were graded as follows: (1 5 no pain to 5 5 severe pain; 1 5 highly improved to 5 5 no improvement; 1 5 too much to 3 5 not
enough and 4 undecided).
†
Two fewer patients were included in this question per group because 4 patients (2 control and 2 experimental) were discharged the same day
of surgery.
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Volume 156, Number 5
now consider that it may be advantageous to institute
a form of aggressive IS (as reported by Jensen et al11)
associated with early ambulation and preoperative patient education. Such an approach was accompanied,
in fact, by a low incidence of postoperative pulmonary
complications and early patient discharge. However,
no patient enrolled in our study required a hospital
stay longer than 3 days.
We used a BMI stratification to identify any difference between the 2 groups as related to weight. IS did
not impact the postoperative day 1 lung volumes in patients with BMI $50 mg/kg2. The control groups actually fared better and experienced a smaller percentage
decrease than the experimental group. However, when
evaluating patients of both groups with a BMI $50
mg/kg2, IS was beneficial in the experimental group
whose patients had a less important decrease in lung
volume than those in the control group. Although this
result may suggest that preoperative IS might benefit patients with a BMI $50 mg/kg2 undergoing bariatric surgery, we cannot rule out a b error because of the small
number of enrolled patients, and any hypothetical effect
is deferred to further investigation.
This study has several limitations. First, patients undergoing 3 specific procedures were included in this
study, so we have combined different surgical procedures that possibly could have a different impact on respiratory mechanics. Another limitation of the study
was the underpowered sample size. A prestudy power
analysis described the need for 21 patients per group
(25 considering the patient drop-out for 50 patients)
for a 15% improvement in total IC. However, based on
our results, to achieve a relative 50% improvement,
60 patients would have been required. Perioperative respiratory function usually is assessed with a combination
of parameters obtained with pletismography, arterial
blood gases (ABG), and spirometry, such as FRC, forced
expiratory volume in 1 s (FEV1), and vital capacity.
However, our study focus was limited to the incentive
spirometer, which is not a sophisticated tool and only
provided measurements of IC. Another limitation of
our study is that enrolled patients used IS for nonuniform
periods of time, as the study protocol requested at least
3 preoperative treatment days but could not assure the
same interval to all patients between the preoperative assessment and the day of surgery followed by the postoperative evaluation. As several patients only used IS for
3 days before surgery, they may not have had sufficient
time to receive the full benefits.
Adequate tidal volume and the use of PEEP intraoperativley are important factors in preventing the formation
of intraoperative atelectasis that may persist after extubation. In our study, mechanical ventilation settings
were not consistent. Furthermore, it has been shown
Cattano et al
271
Fig 3. Preliminary results of lung spirometry from a cohort of bariatric patients. (Color version of figure is available online.)
that keeping a FiO2 at 70% at extubation is effective
in preventing the formation of atelectasis that otherwise
could last up to 24 h after surgery.19,20 Our results
could have been influenced by our institution’s
standard practice of administrating 100% oxygenation
immediately before extubation, causing atelectasis
formation that may mask a possible beneficial effect
of the preoperative spirometry on lung volumes.
Because ABG monitoring was not included in the
research protocol, the correlation between arterial
blood oxygen tension and lung volumes was not
calculated.
Besides, in general, female patients populate studies
on bariatric surgery, and we cannot exclude an
influence determined by gender discrepancies in the
study population.
Neither postoperative pain therapy nor pain scores
were standardized to rule out an interference from
pain on IS performance; however, based on our questionnaires, no patients were affected by inappropriate
pain control.
The postoperative evaluation of IS was scheduled at
postoperative day 1 after surgery. Therefore, we cannot
comment on the possibility that continuing postoperative IS and repeating lung volume measurements during
the next 2 days postoperatively could provide better data
on lung volume. Indeed, a previous preliminary study
on 21 patients (76% female) at an outside institution
(unpublished data graciously provided by A.V.) demonstrated that spirometry of patients undergoing bariatric
surgery demonstrated a significant decrease in all 3 major values (FRC, FEV1, and FEF 75% to 25%) that persisted up to the day of discharge (Fig 3). The patients
in this study were 38 6 11 years of age with a BMI of
40 6 2.8 kg/m2.
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Cattano et al
CONCLUSION
Patients undergoing bariatric surgery seem to not benefit, in terms of postoperative inspiratory lung volumes,
from preoperative use of IS as applied in our study. Of
interest, none of the patients experienced any pulmonary complications. However, our analysis was limited
to measuring lung volumes up until postoperative
day 1. Overall, both groups of patients were satisfied
with their designated use of IS and the study itself, but
some concern was present of poor compliance with
the treatment as reflected by the questionnaires. Extending this study a few days postoperatively likely would
allow us to achieve a better understanding of the course
of respiratory function recovery, and it might allow us to
detect a possible longer term benefit from preoperative
IS use. Additionally, based on our results, any treatment
that results in at least a relative 50% improvement of IC
would require a sample population of 30 patients per
group. Future studies are necessary to identify the predictors or risk factors of postoperative volume loss
more accurately in individual patients and to identify
therapeutic strategies better.
A larger study consisting of patients with a BMI .50
kg/m2 undergoing a single lengthy bariatric procedure,
such as gastric bypass, stratified by gender, that would
include a sensitive marker of blood oxygenation
(ABG) and lung function (spirometry) to be correlated
with IS possibly might provide better data regarding
the perioperative respiratory physiology derangements
in this population.
We thank Vineela Maddukuri, MD, for her assistance in the statistical analysis and research organization, Russell Graham, RT, and Joey
Wilson, RT, for support by providing patient education on incentive
spirometry use and data on the incentive spirometer, the Bariatric Surgery Team at the Memorial Hermann Hospital for their collaboration,
and Memorial Hermann Hospital—Texas Medical Center for their
support.
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