Original Article

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Ann Phlebology 2022; 20(2): 95-99

Published online December 31, 2022

https://doi.org/10.37923/phle.2022.20.2.95

© Annals of phlebology

Change of Venous Return after Diaphragmatic Deep Breathing

Kwangjin Lee, M.D., Hyangkyoung Kim, M.D., Ph.D,, Sungsin Cho, M.D., Ph.D. and Jin Hyun Joh, M.D., Ph.D.

Department of Surgery, Kyung Hee University Hospital at Gangdong, Kyung Hee University School of Medicine, Seoul, Korea

Correspondence to : Hyangkyoung Kim, 892 Dongnam-ro, Gangdong-gu, Seoul 05278, Korea, Department of Surgery, Kyung Hee University Hospital at Gangdong, Kyung Hee University School of Medicine
Tel: 02-440-6261, Fax: 02-440-6296
E-mail: cindycrow7456@gmail.com

Objective: We evaluated the effects of diaphragmatic deep breathing (DB) on venous return in symptomatic patients.
Methods: A prospective study was conducted on volunteers with venous symptoms. After ultrasound confirmation of deep vein patency, the blood flow velocity (peak systolic velocity, PSV) and volume in the common femoral vein (CFV) with duplex ultrasound and wash-out time of 99Technetium-macroaggregated albumin (99Tc-MAA) with radioisotope (RI) venography were measured in supine and standing positions. After practicing DB for a month, the blood flow volume, velocity, and wash-out time of 99Tc-MAA were rechecked.
Results: In the supine position, the PSV of both CFVs and the flow volume of the right CFV were significantly increased after DB (p=0.043, all), while the flow volume of the left CFV did not show a significant change after DB (p=0.138). In the standing position, the PSV of the left CFV significantly increased (p=0.029). The time-to-peak and wash-out times of 99Tc-MAA for both CFVs were significantly shorter with DB than with normal breathing (all, p<0.05).
Conclusion: DB may have a beneficial effect on venous return in patients with symptomatic chronic venous disease. Further research is required to evaluate whether this could be an alternative therapeutic approach.

Keywords Chronic venous disease, Diaphragmatic deep breathing, Venous return, Duplex ultrasound, 99Tc-MAA with radioisotope venography

Chronic venous disease (CVD) is a common medical condition that causes various pathologies, including varicosity, pain, swelling, edema, skin changes, and ulcerations. CVD includes varicose veins and superficial venous reflux conditions. Varicose veins, a common manifestation of venous incompetence in the lower limbs, are dilated, elongated, or tortuous superficial veins that are most often palpable subcutaneous veins with reversed blood flow (1). The incompetence of the deep, superficial, and/or perforating veins leads to increased venous pressure in the lower leg, resulting in skin changes, such as hyperpig-mentation and induration with eventual ulceration (2).

Wearing compression stockings is the primary treatment for symptomatic CVD. However, due to the inconveniences caused in ordinary life, patients often show relatively low treatment compliance. Moreover, CVD patients may be affected by several comorbidities, making their compliance with compressive therapy even worse. The most frequent comorbidities associated with CVD are diabetes mellitus, hypertension, heart failure, peripheral arterial disease, renal insufficiency, emphysema, chronic obstructive pulmonary disease, and malignant disease (3).

Therefore, there is an emerging need for alternative therapeutic strategies. While some studies have reported improvements in venous return in response to various methods in an asymptomatic group (4,5), the fact that these research were conducted with asymptomatic participants in a supine position makes it challenging to apply in clinical practice. In this study, we investigated the effect of diaphragmatic deep breathing (DB) on venous return in symptomatic patients.

Volunteers with venous symptoms participated in this prospective study after obtaining approval from the local institutional review board (C2011116 [566]). Thirteen patients (male:female=4:9) with CVD were recruited from our institution between August 2011 and September 2011. One patient dropped out of the study because of vasovagal syncope during the test, and 12 (four men and eight women) were included in this study.

The study included patients with CVD symptoms who could practice DB correctly and those not indicated for surgery or interventional procedures. Exclusion criteria were: (1) diagnosis of acute or chronic deep venous thrombosis; (2) current use of diuretics, cardiotonics, or vasodilators; (3) heart or kidney disease confirmed through patient history; and (4) current or future pregnancy plan.

Before evaluating its efficacy, we educated the participants on the proper method of DB and instructed them to practice it for 1 month for two reasons: 1) to prevent hyperventilation by exaggerated breathing during the test and allow natural breathing without awareness, and 2) to allow the influence of the respiratory cycle on venous return to persist as a natural course of daily life. During the inspiration phase, while performing DB, patients were instructed to inhale through the nasal cavity without cessation of inhalation and to distend the abdomen gradually. During expiration, the patients were asked to pull in the abdomen and breathe out as much as possible.

After obtaining informed consent from the volunteers, we evaluated the underlying pathologies, including venous reflux, deep vein occlusion, stenosis, or other anatomical abnormalities, using duplex ultrasound (ProSound a7, ALOKA Co., Ltd., Tokyo, Japan) with a 5∼13 MHz probe. Next, we measured the blood flow volume (ml/min) and maximal value of peak systolic velocity (PSV, cm/s) of the common femoral vein (CFV) and the venous flow velocity in both the supine and standing positions. Data averaged from three readings of PSV and blood flow volume were used for subsequent analyses. In addition, we performed radioisotope (RI) venography with a gamma camera (FORTE, Philips, Milpitas, CA, USA) to measure the wash-out time of 99Technetium-macroaggregated albumin (99Tc-MAA) in the standing position (Fig. 1).

Fig. 1. Radioisotope venography. The time to reach the peak level of 99Tc-MAA (Tmax, min) and the half washout time of 99Tc-MAA(T1/2, min) was measured. 99Tc-MAA: 99Technetium-macroaggregated albu-min with normal breathing (A) and diaphragmatic deep breathing (B).

Following the measurements of blood flow volume, CFV velocity, and 99Tc-MAA wash-out time, a professional trainer educated the patients to practice DB and instructed them to practice it for a month. Then, we re-assessed the blood flow volume, CFV velocity, time to reach the peak level of 99Tc-MAA (tmax, min), and the half wash-out time of 99Tc-MAA(t1/2, min).

Continuous variables were compared using the Mann- Whitney U test, while categorical variables were assessed using the c2 or Fisher’s exact test, as appropriate; p<0.05 was considered significant. All statistical analyses were performed using IBM SPSS version 26.0.

Data from 12 participants, including four men and eight women (median age: 27 years, range 23∼32 years), were analyzed. None of the participants had an obstruction or pathological reflux in the lower extremity veins on duplex examination.

Table 1 shows the PSV and blood flow volume measured in supine and standing positions. In the supine position, PSV of CFV was significantly increased with DB compared to natural breathing (NB) on both sides (Right: 122.5 cm/sec vs. 27.5 cm/sec, Left: 81.4 cm/sec vs. 46.4 cm/sec, p=0.043, both). The blood flow volume measured in the supine position was higher after DB than after NB in the right CFV (NB: 655.0 ml/min and DB: 1098.0 ml/min, p=0.043). However, in the left CFV, the blood flow volume did not significantly increase after DB (NB: 450.7 ml/min and DB: 665.7 ml/min, p=0.138).

Table 1 . The median value of peak systolic velocity and blood flow volume of the CFV measured by duplex ultrasonography in the supine and standing position

NBDBp-value
Supine
Rt. PSV (cm/sec)27.5122.50.043
Lt. PSV (cm/sec)46.481.40.043
Rt. flow volume (ml/min)655.01098.00.043
Lt. flow volume (ml/min)450.7665.70.138
Standing
Rt. PSV (cm/sec)15.042.00.105
Lt. PSV (cm/sec)8.631.60.029
Rt. flow volume (ml/min)220.7310.40.573
Lt. flow volume (ml/min)485.6423.80.743

CFV: common femoral vein, PSV: peak systolic velocity flow, NB: normal breathing, DB: diaphragmatic breathing.



In the standing position, there was no significant increase in the PSV after DB compared to NB in the right CFV (NB: 15.0 cm/sec and DB: 42.0 cm/sec, p=0.105), while the PSV of left CFV significantly increased after DB (NB: 8.6 cm/sec and DB: 31.6 cm/sec, p=0.029). There was no significant increase in the flow volume on either side in the standing position (p=0.573 for the right CFV and p=0.743 for the left CFV).

The Tmax and T1/2 are summarized in Table 2. The Tmax (right) was significantly different between the NB and DB conditions (1.15 min and 0.6 min, respectively, p=0.013), as was the measured Tmax (left) (1.4 min and 0.7 min, between the NB and DB, respectively; p=0.016). The T1/2 of 99Tc-MAA (min) was lower in both CFV (right and left) after the DB education; T1/2 (right) was 0.6 min and 0.5 min in NB and DB, respectively (p=0.007), while T1/2 (left) was 0.8 min and 0.4 min in NB and DB, respectively (p=0.013).

Table 2 . The median value of time to reach the peak 99Tc-MAA level and half washout time of 99Tc-MAA measured by 99Tc-MAA venography in standing position

NBDBp-value
Tmax Rt.1.150.60.013
Tmax Lt.1.40.70.016
T1/2 Rt.0.60.50.007
T1/2 Lt.0.80.40.013

Tmax: time to reach peak 99Tc-MAA level (min), T1/2: half washout time of 99Tc-MAA (min), NB: normal breathing, DB: diaphragmatic breathing.


Venous return, the flow of blood back to the heart, is aided by (1) valves, (2) muscles (skeletal muscle), and (3) respiratory (thoracic) pumps. The one-way valves in the veins prevent the backflow of blood, thereby directing the blood flow back towards the heart during venous return. Skeletal muscles act as pumps in the limbs. When muscles are relaxed, closed valves prevent blood from flowing backward. However, when contracting muscles squeeze the veins, open valves allow blood to flow toward the heart. Finally, respiratory pumps modulate intrathoracic pressure. During inspiration at rest, the diaphragm descends, resulting in the lowering of intrathoracic pressure and the resultant expansion of the lungs. This lowered intrathoracic pressure is also transmitted across the walls of the right atrium, thereby promoting right atrial filling and widening of the right atrial transmural pressure (6). Inspiration causes a fall in intra-thoracic pressure and a simultaneous rise in intra-abdominal pressure due to the diaphragm’s descent (7). As we breathe in, the diaphragm flattens, pushing on internal organs, which, in turn, push on veins sending blood back to the heart.

Our study investigated the therapeutic applicability of DB as an intrinsically powerful pump for enhancing venous return. Theoretically, expansion of the abdominal cavity using the appropriate DB method during inspiration might compensate for increased intra-abdominal pressure. However, the effect of DB during inspiration was not significant. In contrast, the increase in venous flow volume and PSV with DB during expiration was evident compared to that with NB. During DB, the duration of each respiratory cycle was much longer than that during NB. A longer expiratory time with DB could have lengthened the time to decrease intra-abdominal pressure, increasing venous return. The effective decrease in intra-abdominal pressure may generate a larger pressure gradient between the infra- and supra- diaphragmatic parts of the inferior vena cava (IVC), “pulling” the blood towards the right atrium and increasing venous return.

The major finding of our study was that DB increased venous return of the lower extremities, which was measured using RI venography in the standing position. This result is supported by previous reports (4,8). Kwon et al. (4) studied the effects of ankle exercise combined with DB on the blood flow velocity in the CFV in the supine position. The mean peak blood flow velocity in the CFV was highest in the participant group that combined ankle exercise with DB. Byeon et al. (8) compared the superior vena cava (SVC) and IVC in patients who had practiced regular DB for over 2 years (mean duration of training was 9.6 years) with the control group. The diameter of the IVC and SVC were measured using transthoracic echocardiography in the supine position. The IVC of participants who practice abdominal breathing had a greater degree of collapse than that of control, suggesting that DB exercise can positively affect venous return via the IVC. The results of our study can be interpreted in the same context. However, previous studies were only performed in the supine position. Considering that CVD symptoms present themselves in the standing position, our study was significant because we examined patients in the supine and standing positions. In our study, not every finding supports the beneficial effect of DB on venous return. The difference in the flow volume in the standing position was not striking, and the flow volume of the left CFV decreased even after DB. In contrast, the Tmax and T1/2 measured by RI venography were improved after DB in the standing position. This difference might result from unclear effects and the small sample size. The difference might have resulted from the different characteristics of both examinations; ultrasound was measured only in the CFV, and RI venography was the sum of all flows in the observed area. The respiration system is a delicate system involved in gas exchange and the body’s balance of acids and bases. To use it therapeutically and not to cause undesirable effects, further research on the exact ratio of expiration and inspiration and breathing methods is required.

The major strength of our study is that we used RI venography, an objective index of venous flow, as the examination tool. Duplex ultrasound has several advantages in diagnosis, treatment guidance, and follow-up, including low cost, portability, noninvasiveness, and safety (9). Similar to contrast venography, this tool provides a roadmap of vein anatomy and essential hemodynamic information (10,11). Although duplex ultrasound is the diagnostic test of choice for diagnosing and evaluating venous disease, RI veno-graphy was used simultaneously to increase reliability as an objective test. RI venography, while technically simple, is a reliable test for examining vessels with no blood flow, collateral blood flow, various types of adjacent blood flow, or other asymmetric blood flow insufficiency that suggests venous insufficiency (12).

A major limitation of our study is the small sample size. We believe that this might have resulted in the statistical insignificance of the results of the left CFV in the supine position. Although there seemed to be a difference in the blood flow volume between the NB and DB conditions, this effect did not reach statistical significance. Recruiting patients with CVD symptoms is difficult, given that using compression stockings is regarded as the standard method to improve the symptoms of CVD. Thus, attempting DB before using compression stockings is not advisable. In addition, since 99Tc-MAA venography is not a mandatory tool for diagnosing CVD, it was difficult to examine every patient because the test requires intravenous injection. Another key limitation is that the follow-up time was short and symptomatic improvement could not be measured. Further studies are needed to examine the long-term efficacy of this approach.

The time-to-peak and wash-out times of CFV in the standing position increased after DB. This result implies that DB can benefit venous return and improve symptoms experienced by patients with CVD. A well-organized practice program that recruits a larger sample is required.

  1. National Clinical Guideline C. National Institute for Health and Care Excellence: Clinical Guidelines. Varicose Veins in the Legs: The Diagnosis and Management of Varicose Veins. London: National Institute for Health and Care Excellence (UK); 2013. Copyright (c) National Clinical Guideline Centre (July 2013).
  2. Evans CJ, Fowkes FG, Ruckley CV, Lee AJ. Prevalence of varicose veins and chronic venous insufficiency in men and women in the general population: Edinburgh Vein Study. J Epidemiol Community Health. 1999;53:149-53.
  3. Matic P, Jolic S, Tanaskovic S, Soldatovic I, Katsiki N, Isenovic E, et al. Chronic Venous Disease and Comor-bidities. Angiology. 2015;66:539-44.
  4. Kwon OY, Jung DY, Kim Y, Cho SH, Yi CH. Effects of ankle exercise combined with deep breathing on blood flow velocity in the femoral vein. Aust J Physiother. 2003;49:253-8.
  5. Miller JD, Pegelow DF, Jacques AJ, Dempsey JA. Effects of augmented respiratory muscle pressure production on locomotor limb venous return during calf contraction exercise. J Appl Physiol (1985). 2005;99:1802-15.
  6. Miller JD, Pegelow DF, Jacques AJ, Dempsey JA. Skeletal muscle pump versus respiratory muscle pump: modulation of venous return from the locomotor limb in humans. J Physiol. 2005;563:925-43.
  7. Kimura BJ, Dalugdugan R, Gilcrease GW 3rd, Phan JN, Showalter BK, Wolfson T. The effect of breathing manner on inferior vena caval diameter. Eur J Echocardiogr. 2011;12:120-3.
  8. Byeon K, Choi JO, Yang JH, Sung J, Park SW, Oh JK, et al. The response of the vena cava to abdominal breathing. J Altern Complement Med. 2012;18:153-7.
  9. Malgor RD, Labropoulos N. Diagnosis of venous disease with duplex ultrasound. Phlebology. 2013;28 Suppl 1:158-61.
  10. Meissner MH, Moneta G, Burnand K, Gloviczki P, Lohr JM, Lurie F, et al. The hemodynamics and diagnosis of venous disease. J Vasc Surg. 2007;46 Suppl S:4S-24S.
  11. Barleben A, Bandyk DF. Interpretation of peripheral venous duplex testing. Semin Vasc Surg. 2013;26:111-9.
  12. Mangkharak J, Chiewvit S, Chaiyasoot W, Pusuwan P, Permpikul C, Toopmongkol C, et al. Radionuclide venography in the diagnosis of deep vein thrombosis of the lower extremities: a comparison to contrast venography. J Med Assoc Thai. 1998;81:432-41.

Original Article

Ann Phlebology 2022; 20(2): 95-99

Published online December 31, 2022 https://doi.org/10.37923/phle.2022.20.2.95

Copyright © Annals of phlebology.

Change of Venous Return after Diaphragmatic Deep Breathing

Kwangjin Lee, M.D., Hyangkyoung Kim, M.D., Ph.D,, Sungsin Cho, M.D., Ph.D. and Jin Hyun Joh, M.D., Ph.D.

Department of Surgery, Kyung Hee University Hospital at Gangdong, Kyung Hee University School of Medicine, Seoul, Korea

Correspondence to:Hyangkyoung Kim, 892 Dongnam-ro, Gangdong-gu, Seoul 05278, Korea, Department of Surgery, Kyung Hee University Hospital at Gangdong, Kyung Hee University School of Medicine
Tel: 02-440-6261, Fax: 02-440-6296
E-mail: cindycrow7456@gmail.com

Abstract

Objective: We evaluated the effects of diaphragmatic deep breathing (DB) on venous return in symptomatic patients.
Methods: A prospective study was conducted on volunteers with venous symptoms. After ultrasound confirmation of deep vein patency, the blood flow velocity (peak systolic velocity, PSV) and volume in the common femoral vein (CFV) with duplex ultrasound and wash-out time of 99Technetium-macroaggregated albumin (99Tc-MAA) with radioisotope (RI) venography were measured in supine and standing positions. After practicing DB for a month, the blood flow volume, velocity, and wash-out time of 99Tc-MAA were rechecked.
Results: In the supine position, the PSV of both CFVs and the flow volume of the right CFV were significantly increased after DB (p=0.043, all), while the flow volume of the left CFV did not show a significant change after DB (p=0.138). In the standing position, the PSV of the left CFV significantly increased (p=0.029). The time-to-peak and wash-out times of 99Tc-MAA for both CFVs were significantly shorter with DB than with normal breathing (all, p<0.05).
Conclusion: DB may have a beneficial effect on venous return in patients with symptomatic chronic venous disease. Further research is required to evaluate whether this could be an alternative therapeutic approach.

Keywords: Chronic venous disease, Diaphragmatic deep breathing, Venous return, Duplex ultrasound, 99Tc-MAA with radioisotope venography

INTRODUCTION

Chronic venous disease (CVD) is a common medical condition that causes various pathologies, including varicosity, pain, swelling, edema, skin changes, and ulcerations. CVD includes varicose veins and superficial venous reflux conditions. Varicose veins, a common manifestation of venous incompetence in the lower limbs, are dilated, elongated, or tortuous superficial veins that are most often palpable subcutaneous veins with reversed blood flow (1). The incompetence of the deep, superficial, and/or perforating veins leads to increased venous pressure in the lower leg, resulting in skin changes, such as hyperpig-mentation and induration with eventual ulceration (2).

Wearing compression stockings is the primary treatment for symptomatic CVD. However, due to the inconveniences caused in ordinary life, patients often show relatively low treatment compliance. Moreover, CVD patients may be affected by several comorbidities, making their compliance with compressive therapy even worse. The most frequent comorbidities associated with CVD are diabetes mellitus, hypertension, heart failure, peripheral arterial disease, renal insufficiency, emphysema, chronic obstructive pulmonary disease, and malignant disease (3).

Therefore, there is an emerging need for alternative therapeutic strategies. While some studies have reported improvements in venous return in response to various methods in an asymptomatic group (4,5), the fact that these research were conducted with asymptomatic participants in a supine position makes it challenging to apply in clinical practice. In this study, we investigated the effect of diaphragmatic deep breathing (DB) on venous return in symptomatic patients.

MATERIALS AND METHODS

Volunteers with venous symptoms participated in this prospective study after obtaining approval from the local institutional review board (C2011116 [566]). Thirteen patients (male:female=4:9) with CVD were recruited from our institution between August 2011 and September 2011. One patient dropped out of the study because of vasovagal syncope during the test, and 12 (four men and eight women) were included in this study.

The study included patients with CVD symptoms who could practice DB correctly and those not indicated for surgery or interventional procedures. Exclusion criteria were: (1) diagnosis of acute or chronic deep venous thrombosis; (2) current use of diuretics, cardiotonics, or vasodilators; (3) heart or kidney disease confirmed through patient history; and (4) current or future pregnancy plan.

Before evaluating its efficacy, we educated the participants on the proper method of DB and instructed them to practice it for 1 month for two reasons: 1) to prevent hyperventilation by exaggerated breathing during the test and allow natural breathing without awareness, and 2) to allow the influence of the respiratory cycle on venous return to persist as a natural course of daily life. During the inspiration phase, while performing DB, patients were instructed to inhale through the nasal cavity without cessation of inhalation and to distend the abdomen gradually. During expiration, the patients were asked to pull in the abdomen and breathe out as much as possible.

After obtaining informed consent from the volunteers, we evaluated the underlying pathologies, including venous reflux, deep vein occlusion, stenosis, or other anatomical abnormalities, using duplex ultrasound (ProSound a7, ALOKA Co., Ltd., Tokyo, Japan) with a 5∼13 MHz probe. Next, we measured the blood flow volume (ml/min) and maximal value of peak systolic velocity (PSV, cm/s) of the common femoral vein (CFV) and the venous flow velocity in both the supine and standing positions. Data averaged from three readings of PSV and blood flow volume were used for subsequent analyses. In addition, we performed radioisotope (RI) venography with a gamma camera (FORTE, Philips, Milpitas, CA, USA) to measure the wash-out time of 99Technetium-macroaggregated albumin (99Tc-MAA) in the standing position (Fig. 1).

Figure 1. Radioisotope venography. The time to reach the peak level of 99Tc-MAA (Tmax, min) and the half washout time of 99Tc-MAA(T1/2, min) was measured. 99Tc-MAA: 99Technetium-macroaggregated albu-min with normal breathing (A) and diaphragmatic deep breathing (B).

Following the measurements of blood flow volume, CFV velocity, and 99Tc-MAA wash-out time, a professional trainer educated the patients to practice DB and instructed them to practice it for a month. Then, we re-assessed the blood flow volume, CFV velocity, time to reach the peak level of 99Tc-MAA (tmax, min), and the half wash-out time of 99Tc-MAA(t1/2, min).

Continuous variables were compared using the Mann- Whitney U test, while categorical variables were assessed using the c2 or Fisher’s exact test, as appropriate; p<0.05 was considered significant. All statistical analyses were performed using IBM SPSS version 26.0.

RESULTS

Data from 12 participants, including four men and eight women (median age: 27 years, range 23∼32 years), were analyzed. None of the participants had an obstruction or pathological reflux in the lower extremity veins on duplex examination.

Table 1 shows the PSV and blood flow volume measured in supine and standing positions. In the supine position, PSV of CFV was significantly increased with DB compared to natural breathing (NB) on both sides (Right: 122.5 cm/sec vs. 27.5 cm/sec, Left: 81.4 cm/sec vs. 46.4 cm/sec, p=0.043, both). The blood flow volume measured in the supine position was higher after DB than after NB in the right CFV (NB: 655.0 ml/min and DB: 1098.0 ml/min, p=0.043). However, in the left CFV, the blood flow volume did not significantly increase after DB (NB: 450.7 ml/min and DB: 665.7 ml/min, p=0.138).

Table 1 . The median value of peak systolic velocity and blood flow volume of the CFV measured by duplex ultrasonography in the supine and standing position.

NBDBp-value
Supine
Rt. PSV (cm/sec)27.5122.50.043
Lt. PSV (cm/sec)46.481.40.043
Rt. flow volume (ml/min)655.01098.00.043
Lt. flow volume (ml/min)450.7665.70.138
Standing
Rt. PSV (cm/sec)15.042.00.105
Lt. PSV (cm/sec)8.631.60.029
Rt. flow volume (ml/min)220.7310.40.573
Lt. flow volume (ml/min)485.6423.80.743

CFV: common femoral vein, PSV: peak systolic velocity flow, NB: normal breathing, DB: diaphragmatic breathing..



In the standing position, there was no significant increase in the PSV after DB compared to NB in the right CFV (NB: 15.0 cm/sec and DB: 42.0 cm/sec, p=0.105), while the PSV of left CFV significantly increased after DB (NB: 8.6 cm/sec and DB: 31.6 cm/sec, p=0.029). There was no significant increase in the flow volume on either side in the standing position (p=0.573 for the right CFV and p=0.743 for the left CFV).

The Tmax and T1/2 are summarized in Table 2. The Tmax (right) was significantly different between the NB and DB conditions (1.15 min and 0.6 min, respectively, p=0.013), as was the measured Tmax (left) (1.4 min and 0.7 min, between the NB and DB, respectively; p=0.016). The T1/2 of 99Tc-MAA (min) was lower in both CFV (right and left) after the DB education; T1/2 (right) was 0.6 min and 0.5 min in NB and DB, respectively (p=0.007), while T1/2 (left) was 0.8 min and 0.4 min in NB and DB, respectively (p=0.013).

Table 2 . The median value of time to reach the peak 99Tc-MAA level and half washout time of 99Tc-MAA measured by 99Tc-MAA venography in standing position.

NBDBp-value
Tmax Rt.1.150.60.013
Tmax Lt.1.40.70.016
T1/2 Rt.0.60.50.007
T1/2 Lt.0.80.40.013

Tmax: time to reach peak 99Tc-MAA level (min), T1/2: half washout time of 99Tc-MAA (min), NB: normal breathing, DB: diaphragmatic breathing..


DISCUSSION

Venous return, the flow of blood back to the heart, is aided by (1) valves, (2) muscles (skeletal muscle), and (3) respiratory (thoracic) pumps. The one-way valves in the veins prevent the backflow of blood, thereby directing the blood flow back towards the heart during venous return. Skeletal muscles act as pumps in the limbs. When muscles are relaxed, closed valves prevent blood from flowing backward. However, when contracting muscles squeeze the veins, open valves allow blood to flow toward the heart. Finally, respiratory pumps modulate intrathoracic pressure. During inspiration at rest, the diaphragm descends, resulting in the lowering of intrathoracic pressure and the resultant expansion of the lungs. This lowered intrathoracic pressure is also transmitted across the walls of the right atrium, thereby promoting right atrial filling and widening of the right atrial transmural pressure (6). Inspiration causes a fall in intra-thoracic pressure and a simultaneous rise in intra-abdominal pressure due to the diaphragm’s descent (7). As we breathe in, the diaphragm flattens, pushing on internal organs, which, in turn, push on veins sending blood back to the heart.

Our study investigated the therapeutic applicability of DB as an intrinsically powerful pump for enhancing venous return. Theoretically, expansion of the abdominal cavity using the appropriate DB method during inspiration might compensate for increased intra-abdominal pressure. However, the effect of DB during inspiration was not significant. In contrast, the increase in venous flow volume and PSV with DB during expiration was evident compared to that with NB. During DB, the duration of each respiratory cycle was much longer than that during NB. A longer expiratory time with DB could have lengthened the time to decrease intra-abdominal pressure, increasing venous return. The effective decrease in intra-abdominal pressure may generate a larger pressure gradient between the infra- and supra- diaphragmatic parts of the inferior vena cava (IVC), “pulling” the blood towards the right atrium and increasing venous return.

The major finding of our study was that DB increased venous return of the lower extremities, which was measured using RI venography in the standing position. This result is supported by previous reports (4,8). Kwon et al. (4) studied the effects of ankle exercise combined with DB on the blood flow velocity in the CFV in the supine position. The mean peak blood flow velocity in the CFV was highest in the participant group that combined ankle exercise with DB. Byeon et al. (8) compared the superior vena cava (SVC) and IVC in patients who had practiced regular DB for over 2 years (mean duration of training was 9.6 years) with the control group. The diameter of the IVC and SVC were measured using transthoracic echocardiography in the supine position. The IVC of participants who practice abdominal breathing had a greater degree of collapse than that of control, suggesting that DB exercise can positively affect venous return via the IVC. The results of our study can be interpreted in the same context. However, previous studies were only performed in the supine position. Considering that CVD symptoms present themselves in the standing position, our study was significant because we examined patients in the supine and standing positions. In our study, not every finding supports the beneficial effect of DB on venous return. The difference in the flow volume in the standing position was not striking, and the flow volume of the left CFV decreased even after DB. In contrast, the Tmax and T1/2 measured by RI venography were improved after DB in the standing position. This difference might result from unclear effects and the small sample size. The difference might have resulted from the different characteristics of both examinations; ultrasound was measured only in the CFV, and RI venography was the sum of all flows in the observed area. The respiration system is a delicate system involved in gas exchange and the body’s balance of acids and bases. To use it therapeutically and not to cause undesirable effects, further research on the exact ratio of expiration and inspiration and breathing methods is required.

The major strength of our study is that we used RI venography, an objective index of venous flow, as the examination tool. Duplex ultrasound has several advantages in diagnosis, treatment guidance, and follow-up, including low cost, portability, noninvasiveness, and safety (9). Similar to contrast venography, this tool provides a roadmap of vein anatomy and essential hemodynamic information (10,11). Although duplex ultrasound is the diagnostic test of choice for diagnosing and evaluating venous disease, RI veno-graphy was used simultaneously to increase reliability as an objective test. RI venography, while technically simple, is a reliable test for examining vessels with no blood flow, collateral blood flow, various types of adjacent blood flow, or other asymmetric blood flow insufficiency that suggests venous insufficiency (12).

A major limitation of our study is the small sample size. We believe that this might have resulted in the statistical insignificance of the results of the left CFV in the supine position. Although there seemed to be a difference in the blood flow volume between the NB and DB conditions, this effect did not reach statistical significance. Recruiting patients with CVD symptoms is difficult, given that using compression stockings is regarded as the standard method to improve the symptoms of CVD. Thus, attempting DB before using compression stockings is not advisable. In addition, since 99Tc-MAA venography is not a mandatory tool for diagnosing CVD, it was difficult to examine every patient because the test requires intravenous injection. Another key limitation is that the follow-up time was short and symptomatic improvement could not be measured. Further studies are needed to examine the long-term efficacy of this approach.

CONCLUSION

The time-to-peak and wash-out times of CFV in the standing position increased after DB. This result implies that DB can benefit venous return and improve symptoms experienced by patients with CVD. A well-organized practice program that recruits a larger sample is required.

Fig 1.

Figure 1.Radioisotope venography. The time to reach the peak level of 99Tc-MAA (Tmax, min) and the half washout time of 99Tc-MAA(T1/2, min) was measured. 99Tc-MAA: 99Technetium-macroaggregated albu-min with normal breathing (A) and diaphragmatic deep breathing (B).
Annals of Phlebology 2022; 20: 95-99https://doi.org/10.37923/phle.2022.20.2.95

Table 1 . The median value of peak systolic velocity and blood flow volume of the CFV measured by duplex ultrasonography in the supine and standing position.

NBDBp-value
Supine
Rt. PSV (cm/sec)27.5122.50.043
Lt. PSV (cm/sec)46.481.40.043
Rt. flow volume (ml/min)655.01098.00.043
Lt. flow volume (ml/min)450.7665.70.138
Standing
Rt. PSV (cm/sec)15.042.00.105
Lt. PSV (cm/sec)8.631.60.029
Rt. flow volume (ml/min)220.7310.40.573
Lt. flow volume (ml/min)485.6423.80.743

CFV: common femoral vein, PSV: peak systolic velocity flow, NB: normal breathing, DB: diaphragmatic breathing..


Table 2 . The median value of time to reach the peak 99Tc-MAA level and half washout time of 99Tc-MAA measured by 99Tc-MAA venography in standing position.

NBDBp-value
Tmax Rt.1.150.60.013
Tmax Lt.1.40.70.016
T1/2 Rt.0.60.50.007
T1/2 Lt.0.80.40.013

Tmax: time to reach peak 99Tc-MAA level (min), T1/2: half washout time of 99Tc-MAA (min), NB: normal breathing, DB: diaphragmatic breathing..


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Vol.21 No.2 Dec 31, 2023, pp. 53~98

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