Download Lateral Decubitus Position Generates Discomfort

Lateral Decubitus Position Generates
Discomfort and Worsens Lung Function
in Chronic Heart Failure*
Pietro Palermo, MD; Gaia Cattadori, MD; Maurizio Bussotti, MD;
Anna Apostolo, MD; Mauro Contini, MD; and
Piergiuseppe Agostoni, MD, PhD, FCCP
Background: Lateral decubitus position is poorly tolerated by heart failure patients.
Study objectives: To evaluated pulmonary function and lung diffusion in heart failure patients in
the following five body positions: sitting, prone, supine, and left and right decubitus.
Setting: Heart failure unit of a university hospital.
Subjects: We studied 14 chronic heart failure patients in New York Heart Association class III and
14 healthy volunteers.
Measurements and results: After 15 min of a selected position, subjects were evaluated by a
discomfort scale, ear oximetry, and pulmonary function, which included FEV1, FVC, vital capacity
(VC), alveolar volume, and diffusing capacity of the lung for carbon monoxide (DLCO) with
subcomponent membrane resistance (DM) and capillary volume. In healthy subjects, we
observed a reduction of DLCO and capillary volume in both lateral decubiti. Some discomfort was
documented in both lateral decubiti when selected positions were compared with the sitting
position. In the sitting position, pulmonary function suggested slight restriction ([mean ⴞ SD]
FVC, 89.8 ⴞ 22.3% predicted; FEV1, 84.7 ⴞ 16.9% predicted, VC, 88.6 ⴞ 21.5% predicted; and
FEV1/VC, 74 ⴞ 7) with low DLCO (73 ⴞ 19% predicted). Compared with sitting, lung mechanics
were unchanged in prone and supine positions; FEV1, FVC, and FEV1/VC were lower when
patients were lying on their side, with unchanged alveolar volume and VC. DLCO was similar when
comparing sitting, prone, and supine positions, and it was lower in lateral decubitus because of
the lower capillary volume (vs sitting) and DM (vs prone and supine). Body position-related FVC
and DLCO reduction were greatest in the largest hearts (⌬FVC and ⌬DLCO vs left ventricle
diastolic volume R ⴝ 0.524, p < 0.05 and R ⴝ 0.630, p < 0.02, respectively; ⌬FVC and ⌬DLCO vs
cardiothoracic index R ⴝ 0.539, p < 0.05 and R ⴝ 0.685, p < 0.01, respectively).
Conclusions: In heart failure, lateral decubitus airway obstruction and lung diffusion impairment
become greater as heart dimensions increase.
(CHEST 2005; 128:1511–1516)
Key words: cardiomegaly; gravity; heart failure; lung diffusion; pulmonary function
Abbreviations: Dlco ⫽ diffusing capacity of the lung for carbon monoxide; DM ⫽ membrane resistance; VC ⫽ vital
capacity.
t has frequently been observed that heart failure
I patients
report discomfort when lying on their
side. It has also been shown1,2 that heart failure
patients avoid the left lateral decubitus position
during sleep. Although the idea that the heart can
affect regional lung distension is nothing new,3 and
the differences between erect, prone, and supine
*From the Centro Cardiologico Monzino (Drs. Palermo, Cattadori, Bussotti, Apostolo, Contini, and Agostoni), Istituto di
Ricovero e Cura a Carattere Scientifico, Institute of Cardiology,
University of Milan, Milan, Italy; and Division of Respiratory and
Critical Care Medicine (Dr. Agostoni), Department of Medicine,
University of Washington, Seattle, WA.
This study was supported by a Centro Cardiologico Monzino,
Istituto di Ricovero e Cura a Carattere Scientifico research grant.
www.chestjournal.org
positions have been extensively studied in healthy
subjects4 –7 and in patients with cardiac8 and lung9
diseases, to our knowledge, the effect of lying on one
side, in terms of the mechanical properties of the
lungs and of gas diffusion, has never been evaluated
in heart failure patients. The present study was,
Manuscript received April 23, 2004; revision accepted February
7, 2005.
Reproduction of this article is prohibited without written permission
from the American College of Chest Physicians (www.chestjournal.
org/misc/reprints.shtml).
Correspondence to: Piergiuseppe Agostoni, MD, FCCP, Centro
Cardiologico Monzino, Istituto di Ricovero e Cura a Carattere
Scientifico, Institute of Cardiology, University of Milan, 20138
Milan, Italy; e-mail: [email protected]
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1511
therefore, undertaken to assess whether the clinically
reported complaints of breathing difficulties and/or
general discomfort in the lateral position is associated with a difference in lung mechanics and gas
diffusion in patients with chronic heart failure while
in such body positions.
Materials and Methods
We studied 14 subjects with chronic severe heart failure (mean
[⫾ SD] age, 62 ⫾ 8 years; one woman and 13 men) attributable
to dilated cardiomiopathy. The study was carried out under stable
clinical conditions with an optimized drug regimen for at least 2
months. Drug therapy included the following types: diuretics in
all cases, ␤-blocker in 12 of 14 cases, ACE-inhibitors in 7 cases,
AT1 blockers in 6 cases, antialdosterone drugs in 12 cases,
amiodarone in 8 cases, and digitalis in 2 cases. The etiology of
dilated cardiomyopathy was coronary artery disease in eight cases
and idiopathic cardiomiopathy in six cases. All of the patients
were in New York Heart Association class III with a peak oxygen
consumption of 14.4 mL/min/kg (⫾ 2.7; 50 ⫾ 11% predicted)
and a ventilation/carbon dioxide production slope of 36 (⫾ 6). We
also studied 14 healthy volunteers, recruited from hospital employees and friends (age, 61 ⫾ 8 years; 2 women and 12 men).
Patient study inclusion criteria included a cardiothoracic index
⬎ 45% at chest radiograph and a left diastolic volume ⬎ 130 mL
at echocardiography. Study exclusion criteria were as follows: (1)
previous cardiac or thoracic surgery; (2) obesity defined as body
mass index ⬎ 28; (3) presence of lung, pleural, chest wall, or
muscular disease; and (4) presence of smoking history. The
healthy subjects had a negative medical history, normal echocardiogram, and cardiopulmonary exercise test, and all of them were
nonsmokers. The patients with heart failure had a chest radiograph for cardiothoracic index determination. This index was
measured as the ratio of the transverse diameter of the heart in
relation to the diameter of the thoracic cavity. Echocardiographic
parameters were collected in all of the patients to determine left
ventricle volumes and ejection fraction.10 We evaluated the
standard pulmonary function, including FEV1, FVC, and vital
capacity (VC), alveolar volume, and diffusing capacity of the lung
for carbon monoxide (Dlco). To allow for measurements in the
various body positions, a 30-cm rigid tube was inserted between
the mouthpiece and the spirometer. This tube was used in all
positions, as well as for instrument calibration. Morris et al11
prediction equations were used for FEV1 and FVC, and the
equations of Crapo and Morris12 were used for Dlco. The
alveolar volume was measured by using a standard single-breath
technique with methane as an indiffusible gas. Dlco was
measured with the single breath-constant expiratory flow technique (model 2200; SensorMedics; Yorba Linda, CA).13 Diffusion
subcomponents, capillary volume, and membrane resistance
(DM) were also measured by applying the method of Roughton
and Forster.14 For this purpose, subjects inhaled gas mixtures
containing 0.3% CH4 and 0.3% CO, with three different oxygen
fractions equal to 20%, 40%, and 60%, respectively, and balanced
with nitrogen. Ear oximetry was also recorded. Measurements
were made on separate consecutive working days, while subjects
were sitting, supine, prone, and recumbent on the left and right
side. Patients remained in the selected position for 15 min before
any measurements were taken. The order of the positions was
random. We also evaluated subjects’ discomfort by asking how
they felt in a specific body position when compared with the
sitting position. The relative discomfort scale was numerical,
from 1 to 5, with 3 being equal to the sitting position, 1 being
much worse, 2 being slightly worse, 4 being slightly better, and 5
being much better. The discomfort evaluation was carried out
immediately before the pulmonary function evaluation. With the
exception of the chest radiograph, all of the control subjects
underwent the same research protocol as the patients.
Statistical Analysis
Data were reported as the mean ⫾ SD. Comparisons between
heart failure and healthy subjects were done in the sitting
position by an unpaired t test. Comparisons within each group
were made with the sitting position by a paired t test after an
analysis of variance evaluation by applying the Bonferroni correction as needed (four comparisons). Correlations were evaluated by linear regression analysis. The discomfort scale is reported both in numerical values and in percentages and was
statistically evaluated by a signed-rank test.
Results
All of the patients tolerated each study body
position without major complaints. In the patient
group, discomfort scale results relative to the sitting
position showed an increase in discomfort in the
left-side and right-side positions (p ⬍ 0.05; median,
3, 3, 2, and 2, respectively in prone, supine, left-side,
and right-side positions). The percentage of distribution of the discomfort scale is reported in Table 1.
The cardiothoracic index was 57.4 ⫾ 6.4%. Echocardiographic parameters revealed the following: left
ventricular diastolic volume 220 ⫾ 81 mL, left ventricular systolic volume 152 ⫾ 72 mL, and left ventricular ejection fraction 33 ⫾ 7%. In the standard
sitting position, pulmonary function tests suggested a
slight restrictive disease as evidenced by the FVC,
FEV1, VC, and FEV1/VC data (Table 2). No major
changes were observed, in terms of lung mechanics
(Table 2), among the sitting, prone, and supine
positions. The FVC was greatest in sitting, prone,
and supine position in seven, five, and two of the
subjects, respectively; and FEV1 was greatest in
sitting, prone, and supine position in eight, four, and
two subjects, respectively. Compared with the sitting
position, FEV1, FVC, and FEV1/VC were lower
when patients were lying on one side, whereas the
alveolar volume and VC were unchanged (Table 2).
Table 1—Discomfort Scale Relative to Sitting Position*
Discomfort Scale
Position
1
2
3
4
5
Prone
Supine
Right decubitus
Left decubitus
0 (0)
0 (0)
2 (14.3)
3 (21.4)
3 (21.4)
4 (28.6)
8 (57.1)
6 (42.9)
9 (64.3)
9 (64.3)
3 (21.4)
3 (21.4)
1 (7.1)
1 (7.1)
1 (7.1)
2 (14.3)
1 (7.1)
0 (0)
0 (0)
0 (0)
*Values given as No. of patients and (% distribution). 1 ⫽ much
worse; 2 ⫽ slightly worse; 3 ⫽ sitting position; 4 ⫽ slightly better;
5 ⫽ much better.
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Clinical Investigations
Table 2—Pulmonary Function in Different Body Positions in Heart Failure Patients*
Variables
Sitting
Prone
Supine
Right Side
Left Side
FEV1, L/s
FEV1 % predicted
FVC, L
FVC % predicted
VC, L
VC % predicted
FEV1/VC
Alveolar volume, L
Hb saturation, %
2.5 ⫾ 0.5
84.7 ⫾ 16.9
3.4 ⫾ 0.9
89.8 ⫾ 22.3
3.5 ⫾ 0.9
88.6 ⫾ 21.5
74 ⫾ 7
4.9 ⫾ 0.8
95.9 ⫾ 1.7
2.5 ⫾ 0.4
83.1 ⫾ 14.1
3.4 ⫾ 0.7
89.2 ⫾ 19.2
3.4 ⫾ 0.8
88.9 ⫾ 18.7
74 ⫾ 5
4.7 ⫾ 0.7
94.4 ⫾ 1.3
2.5 ⫾ 0.5
83.1 ⫾ 15.6
3.3 ⫾ 0.8
87.5 ⫾ 21.6
3.4 ⫾ 0.9
89.7 ⫾ 21.1
74 ⫾ 6
4.7 ⫾ 0.9
96.3 ⫾ 1.5
2.3 ⫾ 0.4†
76.3 ⫾ 13.0†
3.2 ⫾ 0.9†
84.5 ⫾ 22.2†
3.4 ⫾ 0.9
87.5 ⫾ 21.1
69 ⫾ 7†
4.7 ⫾ 0.7
95.7 ⫾ 1.6
2.4 ⫾ 0.5†
77.8 ⫾ 14.5†
3.2 ⫾ 0.8†
85.1 ⫾ 20.7†
3.4 ⫾ 0.9
88.1 ⫾ 21.4
69 ⫾ 7†
4.8 ⫾ 0.9
95.3 ⫾ 1.5
*Values given as mean ⫾ SD, unless otherwise indicated. Hb ⫽ hemoglobin.
†p ⬍ 0.05 vs sitting position.
Dlco was low in the standard sitting position and
was 73 ⫾ 19% of the predicted value. On average,
Dlco was similar when comparing the sitting,
prone, and supine positions (Fig 1); the greatest
Dlco value was observed as follows: while sitting, in
eight subjects; while prone, in two subjects; and
while supine, in four subjects. The capillary volume
was lower in prone and supine positions when
compared with sitting (Fig 2). Dlco was significantly lower with patients lying either on the left or
the right side (Fig 1). This was attributable to a
difference in capillary volume when comparing side
positions with sitting and in DM when comparing
side positions with prone or supine (Fig 2). On
average, Dlco showed no difference between the
left and right side, with the lowest Dlco measurements observed in nine and five of the patients,
respectively on the left and right side. Ear oximetry was unaffected by the body position changes
(Table 2).
Compared with heart failure patients, healthy
subjects had higher FEV1, FVC, VC, alveolar vol-
ume, Dlco, and DM. In healthy subjects, body
position changes did not generate any discomfort.
Lung volumes and flows were unaffected by body
position (Table 3). Dlco decreased when patients
were lying on one side (Fig 1). This is attributable to
a reduction in capillary volume (Fig 2). The body
positions did not influence the hemoglobin oxygen
saturation in healthy subjects (Table 3).
We also evaluated the possibility (either by means
of echocardiographic or radiograph measurements)
that patients with the largest hearts were those with
the greatest body position-related lung mechanics
and Dlco changes. To do so, we correlated the
maximal change (calculated as the difference between the greatest and the smallest value recorded of
a selected parameter) with the left ventricle diastolic
volume and cardiothoracic index. The correlation
between FEV1 and FEV1/VC changes with both left
ventricle diastolic diameter and the cardiothoracic
index did not result in statistical significance (⌬FEV1
and FEV1/VC vs left ventricle diastolic volume:
R ⫽ 0.218 with difference not significant and
R ⫽ 0.229 with difference not significant, respectively; and ⌬FEV1 and FEV1/VC vs cardiothoracic
index: R ⫽ 0.248 with difference not significant and
R ⫽ ⫺0.219 with difference not significant, respectively). On the contrary, a significant correlation was
observed with FVC and Dlco maximal body position-related changes, left ventricle diastolic volume,
and the cardiothoracic index (Fig 3). No correlation
was found between the Dlco changes and cardiac
dimensions in the healthy subjects.
Discussion
Figure 1. Dlco in sitting, prone, supine, and right-side and
left-side decubitus. White columns are heart failure patients and
black columns are healthy individuals. * ⫽ p ⬍ 0.02 vs sitting.
www.chestjournal.org
In this study, the heart is viewed as a structure that
occupies part of the intrathoracic space and that
weighs differently on the lung in relation to body
position.15,16 In congestive heart failure, the lungs
are stiff and heavy, whereas the heart is large and
heavy. As a consequence, the negative effects of
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1513
Figure 2. Lung diffusion for carbon monoxide subcomponents: DM and capillary volume in the five
body positions evaluated. White columns are heart failure patients and black columns are healthy
individuals. * ⫽ p ⬍ 0.02 vs sitting.
lung-heart interdependence are increased.17 Indeed,
it is known that, as the cardiac dimension increases,
lung volume, mechanical function, and diffusion
capacity decrease.18,19 Body position may influence
the lung-heart interaction. Indeed, in healthy, young
subjects, Dlco is higher in the supine position,
when compared with the sitting position,6,5 because
of an increase in capillary volume.6,7 In patients with
ARDS, the prone position eliminates compression of
the lung by the heart,9 and in heart failure patients,
Dlco is similar in the sitting and supine positions
with relevant interpatient variability.8 However, a
systematic evaluation of the effects of body position
on lung function in congestive heart failure patients
has never been carried out. This evaluation is important, because heart failure patients often complain of
difficulties when lying on one side.1,2 Furthermore,
lung function, both lung mechanics and lung diffusion (which are impaired in heart failure), correlates
with exercise capacity and prognosis.17,20 –22 The
main finding of the present study is that, as a patient
lies on one side, right or left, the lung function
deteriorates, and the larger the heart, the greater the
deterioration.
In the sitting position, our findings were similar to
those previously reported8,18 –23 for chronic congestive heart failure. Indeed, we observed data that is
suggestive of a light restrictive syndrome with a
reduction in Dlco. The prone and supine positions
did not influence the lung mechanics as evaluated by
FEV1, FVC, VC, or FEV1/VC in both the healthy
subjects and the heart failure patients. Overall,
Dlco was unchanged.8 However, when comparing
patients in the sitting position, the capillary volume
decreased in both the supine and prone positions.
This observation has never been reported, and the
physiologic reasons cannot be resolved by our study;
however, a speculative hypothesis is tempting. Indeed, redistribution of lung fluids and changes in
ventilation/perfusion relationship, attributable to
gravity, are likely. In the sitting position, heart failure
patients, because of their elevated pulmonary capil-
Table 3—Pulmonary Function in Different Body Positions in Healthy Subjects*
Variables
Sitting
Prone
Supine
Right Side
Left Side
FEV1, L/s
FEV1, % predicted
FVC, L
FVC, % predicted
VC, L
VC, % predicted
FEV1/VC
Alveolar volume, L
Hb saturation, %
3.8 ⫾ 0.8
114 ⫾ 11
4.8 ⫾ 0.9
119 ⫾ 11
5.0 ⫾ 1.0
116 ⫾ 16
75 ⫾ 8
7.1 ⫾ 1.1
96.1 ⫾ 1.0
3.7 ⫾ 0.7
110 ⫾ 14
4.8 ⫾ 0.9
115 ⫾ 13
4.9 ⫾ 0.9
113 ⫾ 14
75 ⫾ 8
6.8 ⫾ 1.2
95.1 ⫾ 2.1
3.6 ⫾ 0.7
109 ⫾ 11
4.8 ⫾ 0.8
115 ⫾ 11
4.8 ⫾ 0.9
112 ⫾ 14
76 ⫾ 8
6.9 ⫾ 1.2
95.2 ⫾ 1.0
3.6 ⫾ 0.7
108 ⫾ 13
4.7 ⫾ 0.9
114 ⫾ 13
4.9 ⫾ 0.9
113 ⫾ 13
74 ⫾ 8
7.1 ⫾ 1.2
96.3 ⫾ 0.9
3.6 ⫾ 0.7
109 ⫾ 12
4.8 ⫾ 0.8
116 ⫾ 12
4.9 ⫾ 0.9
114 ⫾ 14
74 ⫾ 6
7.1 ⫾ 1.3
95.5 ⫾ 0.7
*Values given as mean ⫾ SD, unless otherwise indicated. See Table 2 for abbreviation not used in the text.
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Clinical Investigations
Figure 3. Correlation between lung diffusion (⌬Dlco) and FVC (⌬FVC) maximal change, calculated
as the difference between the greatest and the smallest value recorded in a selected parameter vs the
cardiothoracic index (CTI) and left ventricle diastolic volume (LVDV).
lary pressure, have a better perfusion of the upper
lobes with above-normal capillary volume.23 Contrarily, in the prone and supine positions, the gravitational effect is lower, and capillary volume is
reduced. In healthy subjects, pulmonary vascular
pressures are low, and no significant gravitationalrelated changes in capillary volume can be detected
among the sitting, prone, and supine positions.
Although heart failure patients complain about
lying on one side (as often reported by patients and
as quantified by our discomfort scale), a reduction in
hemoglobin oxygen saturation was not observed.
This is not surprising, considering that, at sea level,
heart failure patients do not desaturate even during
exercise, regardless of the low Dlco values.20,21 We
have not consistently measured ventilation while
patients were in the different positions, but a small
increase in ventilation can easily be the compensatory mechanism that explains the finding of an
unchanged hemoglobin saturation.
Different from some previous reports,4 –7 we did
not observe significant Dlco changes among sitting,
supine, and prone positions in healthy subjects. This
is likely attributable to differences in the age of
subjects, ours being significantly older than subjects
www.chestjournal.org
in previous reports.6,7 We observed a significant
reduction of Dlco in both lateral decubiti. This
observation was unexpected and deserves some comment. Indeed, the observed Dlco reduction is
attributable to capillary volume reduction without
evidence of alveolar edema, given that DM is unchanged.24 It should be remembered that capillary
volume is, as per the technique of Roughton and
Forster,14 the amount of pulmonary blood, or, more
precisely, of pulmonary blood flow, through the
capillaries that participate in the exchange of gas and
not the total amount of capillary volume. It is likely,
therefore, that the reduction of capillary volume we
observed in the lateral decubitus position is attributable to the deterioration of the ventilation/perfusion
mismatch. The absence of alveolar edema formation24 concurs with the absence of discomfort in the
lateral decubitus position.
To answer the clinical question we have raised,
that is, why patients with heart failure often complain of discomfort in the lateral decubitus position
and not in the supine or prone position, it is important to compare data on the prone and supine
positions with right-side or left-side decubitus and
not with data on the sitting position. Indeed, no
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major differences in the height of the thorax are
present when comparing prone, supine, or lateral
decubitus. Our observation suggests that, in the
lateral decubitus, either left or right, the heart
weighs on one lung, compressing both airways and
lung parenchyma; indeed, the reduction of FEV1/VC
with unchanged alveolar volume and VC is suggestive of the occurrence of some obstruction that,
when patients were in a lateral decubitus position, is
likely attributable to airway compression. Dlco,
because of a DM reduction, was lower in the lateral
positions; this is suggestive of some alveolar edema
formation.24 The finding of a greater FVC and Dlco
position-related reduction in the largest hearts (Fig
3) reinforces the concept of some body positiondetermined variability in the compressive forces of
the heart on the lungs. The lack of a significant
correlation between the amount of FEV1 positionrelated changes and heart dimension is likely because of the somewhat greater impairment of FEV1
vs FVC observed in the sitting, prone, or supine
positions (Table 1). All of the above, for example, the
parallel appearance of some airway obstruction and
the reduction of Dlco, are the likely explanations
for the clinically reported discomfort in the lateral
positions. In conclusion, this study reports evidence
of the frequently reported presence of discomfort in
heart failure patients while lying on one side and
shows the transitory occurrence of airways obstruction and, additionally, gas diffusion impairment in
such body positions.
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Clinical Investigations