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Work with Computing Systems 2004. H.M. Khalid, M.G. Helander, A.W. Yeo (Editors) . Kuala Lumpur: Damai Sciences.
302
Measurement of Venous Blood Flow in the Lower Limbs:
Prevention of Deep Vein Thrombosis during Prolonged Sitting
Hideki Oyama a, Yuichi Ebine a, Toshihiro Ando b, and Kageyu Noro a
a Graduate School of Human Sciences, Waseda University, Japan.
b Gifu Prefectural Human Life Technology Research Institute, Japan.
Abstract. The venous blood flow during stretching and deep breathing in the sitting posture was
examined in the present study. First, an inguinocrural venous blood flow was measured using the
Doppler method. It was confirmed that the blood flow velocity significantly increased during
stretching with deep breathing. Second, the peripheral blood circulation in the lower limbs was
evaluated during a 60 min sitting session using a near infrared spectroscopy method. It was confirmed
that stretching while sitting restrained the reduction of blood flow. These results effectively showed an
increase in the venous return. Therefore, we suggest that stretching and deep breathing can be used
sometimes as preventive measures for deep vein thrombosis during prolonged sitting.
Keywords. Venous blood flow, Near infrared spectroscopy, Deep vein thrombosis.
1. Introduction
It has been reported that some airline passengers may develop
blood clots (thrombus) in the deep vein, often in the lower part
of the leg, due to sitting for a long period of time without
mobility. This condition is medically known as deep vein
thrombosis (DVT). If thrombus fragments break off and lodge
in other areas of the body, such as lungs, they may cause a
possibly fatal pulmonary thromboembolism when the person
stands and begins to walk after being immobile for a long
period of time. DVT has been termed, “Economy class
syndrome,” because some cases have been reported in airline
passengers who traveled in the economy class. However, DVT
is not restricted to a particular class of airline travelers, and
may affect any traveler in other classes or in other forms of
transport, including cars, trains, vehicles, if they are in the
sitting position for a long period of time without any form of
exercise. Recently, a similar condition termed “Traveler’s
thrombosis” has been reported. Even theater visitors and
visual display unit (VDU) workers can be at a risk. The
mechanisms of intravascular thrombus formation are still
regarded as being based on the Virchow’s triad: 1) Venous
stasis; 2) Hypercoagulability; 3) Vein wall damage. Figure 1
which based on it shows the risk factors in an aircraft cabin.
Immobility, shifts of body fluid, orthostatic stress, and
compression of the popliteal vein at the edge of the seat are
some conditions arising from long-term, cramped sitting
posture that might lead to the pathological conditions
described by Virchow (1954). The decrease in venous return
that is associated with immobility, reduced respiration, and
legs flexion (a hip joint, knee joint angle) during prolonged
sitting, has also been described as a factor that causes the
venous stasis (Kinjo, 2003). To prevent DVT, it has been
recommended that travelers should be advised drink adequate
fluids, avoid smoking and alcohol, remove tight clotting and to
take exercise such as walking and stretching their limbs (e.g.
Landgraf et al., 1994; Morio, 2002). We are of the opinion that
apart from these measures, stretching of the back is also an
useful strategy. Stretching may promote deep breathing and
venous return from the lower limbs. However, sufficient
scientific evidence related to the effects of these
recommendations in an aircraft cabin is not available.
Figure 1. Risk factors of deep vein thrombus in an aircraft cabin (Source: Eklof et al., 1996; Morio, 2002）
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Measurement of Venous Blood Flow in the Lower Limbs: Prevention of
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Work with Computing Systems 2004. H.M. Khalid, M.G. Helander, A.W. Yeo (Editors) . Kuala Lumpur: Damai Sciences.
303
Figure 2. Experimental environment and test items
The objective of this study was to gain a better
understanding of the blood flow changes that occur in the
sitting posture in passenger seats. The questions addressed in
this study are: 1) Do changes occur in venous return under
different sitting conditions?; 2) Will periodic stretching of the
back have an preventive effect on the peripheral blood
circulation in the lower limbs during prolonged periods of
sitting?
2．Material and Methods
2.1. Experimental environment
The experiments were carried out in a mock-up of a Boeing
767 aircraft cabin (Figure 2). The experimental seat was
adjusted for the Japanese body size. The backrest of the seat
was improved so that the subject’s back was easily extendable,
and it consisted of two independent supports to the upper
(thoracic) and lower (lumbar) back. The following two
investigations were designed for understanding the blood
circulation during sitting.
2.2. Experiment 1: effect of posture conditions and respiration
on venous blood flow velocity
The aim of the first experiment was to investigate the effect of
the interaction between posture conditions and respiration on
venous blood flow velocity in five healthy males. The venous
blood flow velocity was measured using an ultrasonic
rheometer (Smartdop 50EX, Hayashie Electric Co., Japan).
The measurement was carried out on the right inguinocrural
vein. The experimental condition is shown in Table 1. For the
upright position the backrest angle was fixed at 95 degree, for
the reclining position it was fixed at 105 degree, and for the
stretch position it was fixed at 95-115 degree by adjusting the
upper part. In addition, the subject was made to sit with
normal breathing condition and deep breathing condition,
under the former three posture conditions.
Table 1. Conditions of experiment 1
Respiration
Normal
breathing Deep
breathing
Upright position Group-1 Group-4
Reclining position Group-2 Group-5
Posture
Stretching Group-3 Group-6
2.3. Experiment 2: effect of stretching on peripheral blood
circulation during prolonged sitting
The effect of stretching on peripheral circulation in the lower
limbs during prolonged sitting was examined in this study
using the near-infrared spectroscopy (NIRS). The experiment
was performed on ten healthy, middle and old aged females
(mean age, 52.9±7.9 years; weight, 61.4±6.5 kg; stature,
155.8±5.3 cm; body mass index, 25.3±2.5) under two
conditions: “quiet sitting” condition and “sitting with stretch”
condition. Under the two conditions, the subjects were made
to sit for 60 min. In the “sitting with stretch” condition, the
subject stretched for 30 sec during a time interval of 20 min,
40 min, and 60 min from the point when the sitting posture
was attained. NIRS was used to measure and evaluate tissue
blood oxygen saturation non-invasively and continuously.
Using NIRS, it is possible to measure the changes in
oxygenated hemoglobin (OxyHb), deoxygenated hemoglobin
(DeoxyHb), and total hemoglobin (TotalHb) in tissues. During
the sitting posture, peripheral muscle oxygenation was
continuously measured in the right gastrocnemius using a
laser tissue blood oxygen monitor (BOM-L1TRW, Omega
Wave Co., Japan). This instrument uses three laser diodes
(780, 810, and 830 nm), and calculates tissue levels of
OxyHb, DeoxyHb, and TotalHb according to the Beer-
Lambert law. The absorption coefficient of hemoglobin at
each wavelength is based on the data reported by Matcher et
al. (1995).
Work with Computing Systems 2004. H.M. Khalid, M.G. Helander, A.W. Yeo (Editors) . Kuala Lumpur: Damai Sciences.
304
Figure 3. Venous blood flow velocity under each condition
It has been examined that NIRS parameter reflected the
systemic oxygenation consumption (VO2) in the local muscle
by Kawaguchi et al. (2001). For taking the measurements, the
distance between the incident point and the detector was at 13-
30 mm. They were fixed with a tape after shielding with a
rubber sheet and vinyl. The data were input into a personal
computer at sampling frequency of 60 Hz. The analytical data
was calculated one frame per one sec.
3. Results and Discussion
3.1. Results of experiment 1
Figure 3 shows the result of venous blood flow velocity in
each of the condition. A two-way factorial ANOVA was
applied to maximum velocity of venous blood flow. The main
effect of respiration was significant (F = 8.23 p < 0.01), and
the main effect of posture was also significant (F = 3.56 p <
0.05). These results show that the effects of posture and
respiration on the venous blood flow velocity were different.
It was found that the venous blood flow velocity significantly
increased during stretching with deep breathing, which was
slowest during the upright position. It is considered that the
combination of stretching and deep breathing further
increased the venous return. The reclining position that adjusts
the hip joint angle to an obtuse angle may increase the venous
return and reduce the inguinocrural venous blood pressure
from inguinal ligament or fat.
3.2. Results of experiment 2
Figure 4 shows the average values of the blood circulation in
the gastrocnemius muscle. The average amplitude under each
condition after 20 min was converted into a relative value by
using the mean score from 18 min to 20 min as the baseline. A
two-way factorial ANOVA was applied to the category
variables that were time points, and each condition was
applied to scores of OxyHb, DeoxyHb, and TotalHb. A
significant interaction was found between each factor
(OxyHb, F = 2.46, p < 0.05; DeoxyHb, F = 3.30，p < 0.01;
TotalHb, F = 4.25，p < 0.01). This result shows that the blood
circulation was significantly different between the “quiet
sitting” condition and the “sitting with stretch” condition. No
particular trend was observed in the OxyHb levels, and the
DeoxyHb and TotalHb levels gradually decreased under the
“quiet sitting” condition. This trend shows that the peripheral
blood flow decreased because the leg muscle pump was not
active under “quiet sitting” condition. On the other hand,
OxyHb and TotalHb levels increased after stretching during
the 20 min time interval. It is considered that the inflow from
arterial blood increases due to stretching. The DeoxyHb level
decreased after stretching and was recovered later. It is
considered that the outflow of venous blood increases and
OxyHb is converted into DeoxyHb by gastrocnemius muscle
for contraction or circulation regulation function. This finding
suggests that exercise during prolonged sitting restrains the
reduction of blood flow in the lower limbs and has a
preventive effect on DVT.
The clinical DVT cases of Japanese travelers were
females older than 40 years, smaller than 160 cm, and body
mass index 23.8±2.2 reported by Morio et al. (2000). The
female subjects on experiment 2 were similar to this clinical
example and were considered high-risk group. The results of
this experiment suggest evidence that stretching is useful for
high-risk group.
4. Summary
The effect of physical exercise on blood flow in the lower
limbs during a sitting posture was examined in the present
study. The results showed that when back stretching and deep
breathing were both carried out by a person, a significant
increase was observed in the inguinocrural venous blood
velocity using the Doppler method. The reclining position that
adjusts the hip joint angle to an obtuse angle increases venous
return. Furthermore, the peripheral blood circulation in the
gastrocnemius was measured during a 60 min sitting session
using the NIRS. The results show that no particular trend was
observed in the OxyHb levels, and the DeoxyHb and TotalHb
levels gradually decreased under the “quiet sitting” condition.
On the other hand, OxyHb, TotalHb, and DeoxyHb levels
increased under the “sitting with stretch” condition.
Work with Computing Systems 2004. H.M. Khalid, M.G. Helander, A.W. Yeo (Editors) . Kuala Lumpur: Damai Sciences.
305
Figure 4. Peripheral blood circulation (OxyHb, DeoxyHb, and TotalHb levels) in the gastrocnemius under each condition.
These findings suggest that exercise during prolonged sitting
restrains the reduction of venous return from lower limbs and
has a preventive effect on DVT. As a preventive measure for
DVT, leg exercises are commonly recommended. The authors
were of the opinion that apart from leg exercises, back
stretching was also a useful measure. The above results
support this idea. DVT affects not only individuals working in
an aircraft cabin but may also affect VDU workers in an office
or any traveler using any forms of transport, including cars
and trains, if they are in the sitting posture for a long period of
time without any exercise. To prevent DVT in daily life,
stretching and deep breathing are recommended along with
leg exercises during a sitting posture.
5. Acknowledgments
This study was supported by Koito Industries, Ltd, Japan. The
authors would like to thank Dr. Masayoshi Kinjo (Shonan
Toubu Hospital) and Dr. Hiroshi Morio (Narita Red Cross
Hospital) for their valuable advice.
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