Doppler echocardiographic evaluation of latent pulmonary hypertension by passive leg raising

Posture and Time Arrangement Influence Shank Circumference Reduction When Performing Leg Raising Exercise

This study recruited nine young women who performed a leg raising exercise under six test combinations of three holding postures (lying supine, placing the shanks on a yoga ball, and elevating the legs at 60° against the wall) and two time arrangements (continuous vs. intermittent) for a period of 15 min. The intermittent arrangement included an additional 1-min rest set in the middle of the 15 min test. The participants' shank circumference (SC) reductions and discomfort ratings were measured after each test combination was performed. Results indicated that the most efficient method for SC reduction was the yoga ball (5.4 mm), followed by the supine lying posture (4.6 mm) and wall-supported leg raising (3.1 mm). A significant interaction of posture × time arrangement (p < 0.01) implied that the yoga ball method combined with a 1-min rest produced the greatest SC reduction (6.7 mm). Our results also showed that participants experienced the greatest discomfort (score: 4.96) when performing wall-supported leg raising, compared with both lying supine (score: 1.34) and the yoga ball (score: 1.32). This study suggests that the effectiveness of leg raising as conventionally practiced for eliminating leg fatigue or swelling requires further consideration.

Not Bad: Passive Leg Raising in Cardiopulmonary Resuscitation-A New Modeling Study

Aim: To evaluate, using a simulated haemodynamic circulation model, whether passive leg raising (PLR) is able to improve the effect during cardiopulmonary resuscitation (CPR); to expose the possible reasons why PLR works or not. Materials and Methods: We adapted a circulatory model for CPR with PLR. First we compared cardiac output (CO), coronary perfusion pressure (CPP), blood flow to heart (Q_heart), and blood flow to neck and brain (Q_head) of standard chest compression-only CPR with and without PLR; second we simulated the effects of PLR in different situations, by varying the thoracic pump factor (TPF) from 0 to 1; third we simulated the effects when the legs are lifted to the different heights. Finally, we compared our results with those obtained from a published clinical study. Results: According to the simulation model, (1) When TPF is in the interval (0,1), CPP, CO, Q_heart, and Q_head are improved with PLR, among them with half-thoracic/half-cardiac pump effect (TPF is 0.5), CPP, CO, Q_head, and Q_heart increase the most (by 14, 14, 15, and 17%). (2) When TPF is 1 (pure thoracic pump, with an emphysema or extremely thick thorax), PLR has almost no effect on CPP, CO, and Q_heart (-1, 2, and 0%), whereas Q_head is increased by 9%; (3) Regardless of whether there is a cardiac or thoracic pump effect, PLR is able to increase Q_head by 9-15%. (4) When the legs are lifted to 30° to the ground, the volume transferred from legs to upper body is 36% of the initial volume in legs; when the legs are lifted to 45°, the volume transferred is 43%; when the legs are lifted to 60°, the volume transferred is 47%; when the legs are lifted to 90°, the volume transferred is 50%. Conclusion: Generally PLR is able to achieve improved cerebral perfusion and coronary perfusion. In some extreme situations, it has no effect on cardiac output and coronary perfusion, but still improves cerebral perfusion. PLR could be a beneficial supplement to CPR, and it is not necessary to lift the legs too high above the ground.

Comparison of passive leg raising and hyperemia on macrovascular and microvascular responses

Passive leg raising is a simple diagnostic maneuver that has been proposed as a measure of arterial vasodilator reserve and possibly endothelial function. While passive leg raising has previously been shown to lower blood pressure, increase flow velocity and cause brachial artery dilation, its effects on microvascular flow has not been well studied. Also, passive leg raising has been directly compared previously to upper arm but never to lower arm occlusion of blood flow induced hyperemia responses. We compared changes in macrovascular indices measured by brachial artery ultrasound and microvascular perfusion measured by Laser Doppler Flowmetry induced by passive leg raising to those provoked by upper arm and lower arm induced hyperemia in healthy subjects. Upper arm induced hyperemia increased mean flow velocity by 398%, induced brachial artery dilatation by 16.3%, and increased microvascular perfusion by 246% (p<.05 for all). Lower arm induced hyperemia increased flow velocity by 227%, induced brachial artery dilatation by 10.8%, and increased microvascular perfusion by 281%. Passive leg raising increased flow velocity by 29% and brachial artery dilatation by 5.6% (p<.05 for all), but did not change microvascular perfusion (-5%, p=ns). In conclusion, passive leg raising increases flow velocity orders of magnitude less than does upper arm or lower arm induced hyperemia. Passive leg raising-induced brachial artery dilatation is less robust than either of these hyperemic techniques. Finally, although upper arm and lower arm hyperemia elicits macrovascular and microvascular responses, passive leg raising elicits only macrovascular responses.

Passive leg raising induced brachial artery dilation: is an old technique a simpler method to measure endothelial function?

OBJECTIVES

Passive leg raising (PLR) is a diagnostic maneuver that has been shown to cause brachial artery dilation (BAD). The objectives of this study were to compare BAD induced by PLR with flow mediated dilation (FMD), and to investigate the mechanism of PLR-BAD. We studied a total of 75 subjects with and without cardiovascular risk factors/disease in order to provide a wide range of FMD responses.

METHODS

Using ultrasound, PLR-BAD and FMD induced by release of arterial cuff occlusion were measured.

RESULTS

BA diameter increased from 0.33+0.06 at baseline to 0.35+/-0.06 cm (p<.001) (4.8% increase) upon PLR and from 0.33+/-0.06 to 0.37+/-0.06 (11.8%) upon hyperemia. PLR induced BAD was significantly correlated with FMD (r=.82, p<.001). On receiver operating characteristic analysis of the two techniques, the area under the curve was 0.86 (95% CI 0.79-0.94, p<.001). Heart rate variability measures remained unchanged upon PLR indicating minimal contributions from changes in autonomic activity. The combination of FMD and PLR did not result in greater BAD than did FMD alone consistent with a common underlying mechanism. Mean blood flow velocity increased prior to BAD suggesting that shear stress increases prior to BAD.

CONCLUSIONS

BAD occurs in response to PLR and is proportional to FMD, although the magnitude of PLR-BAD is less than half that of FMD. It appears to occur by the same endothelial dependent mechanism as FMD. PLR-BAD may be used as a surrogate measure of FMD to evaluate vascular function, and has the advantage of being simpler to perform.

The effects of passive leg raising on arterial wave reflection in healthy adults

BACKGROUND

Passive leg raising (PLR) produces hemodynamic and physiological changes related to centralizing blood volume and baroreceptor activation.

METHODS/RESULTS

To evaluate the effects of PLR on central hemodynamics, we prospectively studied 50 healthy participants (80% male, age 37 +/- 12 years). Central aortic blood pressures (CA-BPs) and reflected wave properties were evaluated using applanation tonometry at baseline and upon 1 min of PLR. Heart rate (HR) was unchanged. Brachial artery (BA)-systolic BP, BA-diastolic BP, and BA-pulse pressure (PP) all decreased from baseline to PLR. Changes in BA-PP were significantly greater than changes in CA-PP. Reflected wave augmentation pressure (P(s)-P(i)), HR corrected augmentation index (AIx@75), and augmentation index decreased significantly [(P(s)-P(i)): 5 +/- 6 vs. 4 +/-5, P < 0.001; AIx@75%: 10 +/- 13 vs. 7 +/- 12, P = 0.004; AI%: 14 +/- 12 vs. 12 +/- 12, P = 0.014, respectively]. HR corrected ejection duration (ED(c)), round trip travel time (deltat(p)), and reflected wave systolic duration (deltat(r)) all increased upon PLR [ED(c): 433 +/- 15 vs. 444 +/- 17, P < 0.001; deltat(p): 149 +/- 18 vs. 156 +/- 20, P = 0.003; deltat(r): 174 +/- 33 vs. 179 +/- 32, P = 0.046, respectively]. Indices of left ventricular (LV) workload including wasted LV energy and tension-time index decreased upon PLR.

CONCLUSION

PLR decreases the amplitude and delays the onset of the reflected aortic pressure wave. This decreases wasted LV pressure energy and workload.