Question 3
What is the Valsalva manoeuvre? Explain the cardiovascular response and include graphs in your answer.
College Answer
A good answer to this question required attention to detail and an ability to describe
changes in many variables at each stage e.g. intrathoracic pressure, blood volumes,
baroreceptor firing and the subsequent cardiovascular response (e.g. heart rate and blood
pressure). Using graph(s) is a useful way to assist the explanation and was required as part
of the answer. Dividing the response into four stages makes answering the question much
easier. Overall there was a deficiency in a deep understanding of the integrated physiology
associated with the Valsalva manoeuvre. The most common mistakes were describing a
change but not saying why it happened, not considering each element at each stage and
confusing terms e.g. saying increased cardiac output when the response was increased
mean arterial pressure. Very few candidates drew accurate graphs. Graphs required were
those of the changes in intrathoracic pressure, the pulse pressure response and the heart
rate response.
Discussion
From the above, it sounds as if the examiners wanted something with graphs, but also something that describes the change, "saying why it happened", and considering each element at each stage. The latter sounds a lot like some kind of table.
- The Valsalva Manoeuvre is
- expiratory effort against an obstructed airway (eg. closed glottis),
- which generates an intrathoracic pressure of ~ 40 mmHg
- which continues for 15-20 seconds
- and which is usually performed in a seated or supine position
The graph:
And now, the change, why it happened, and considering each element at each stage:
| Phase | Event | Causes of that event |
| Phase 1 | Increased intrathoracic pressure | Voluntary breath hold against a closed glottis, or a closed expiratory valve of a ventilator |
| Decreased venous return | Increased intrathoracic pressure | |
| Decreased LV afterload | Decreased LV transmural pressure and aortic transmural pressure | |
| Increased LV preload | Displacement of blood | |
| Increased blood pressure with stable pulse pressure | Decreased afterload and increased preload on the LV, which increases the stroke volume | |
| Decreased heart rate | Baroreflex activated by high blood pressure decreases the heart rate by means of the vagus | |
| Early Phase 2 | Decreased venous return to the LV | Sustained high intrathoracic pressure |
| Decreased cardiac output | Decreased venous return to the LV and RV | |
| Decreased pulse pressure | Smaller stroke volume due to low venous return | |
| Increased heart rate | Baroreflex vagally mediated tachycardia | |
| Decreased blood pressure | Baroreflex activation of peripheral vasoconstriction lags behind vagal tachycardia | |
| Late Phase 2 | Restored cardiac output | Increased heart rate compensates for the decreased stroke volume |
| Restored blood pressure | Sympathetic activation by the baroreflex increases the peripheral vascular resistance | |
| Phase 3 | Decreased (re-normalised) intrathoracic pressure | Release of the obstruction, eg. voluntary exhalation or the opening of the expiratory valve |
| Reduced RV afterload | Decreased intrathoracic pressure | |
| Increased RV preload | Restored venous return, plus the return of blood from engorged extrathoracic veins | |
| Decreased LV preload | Interventricular interdependence | |
| Increased LV afterload | Increased LV transmural pressure due to loss of intrathoracic pressure | |
| Decreased blood pressure and pulse pressure | Increased LV afterload and decreased LV preload | |
| Increased heart rate | Baroreceptor-mediated, due to low blood pressure | |
| Phase 4 | Restoration of LV preload | After several heartbeats the LV preload returns to normal as right and left sided flow equalises |
| Increased blood pressure | Blood pressure and cardiac output increase transiently because the preload is restored but peripheral vascular resistance remains high | |
| Heart rate decreases | Baroreceptor-mediated reaction to restored blood pressure |
References
Pstras, L., et al. "The Valsalva manoeuvre: physiology and clinical examples." Acta physiologica 217.2 (2016): 103-119.
Jellinek, Ernest H. "The Valsalva manoeuvre and Antonio Valsalva (1666–1723)." Journal of the Royal Society of Medicine 99.9 (2006): 448-451.
Junqueira Jr, Luiz Fernando. "Teaching cardiac autonomic function dynamics employing the Valsalva (Valsalva-Weber) maneuver." Advances in Physiology Education 32.1 (2008): 100-106.
Looga, Robert. "The Valsalva manoeuvre—cardiovascular effects and performance technique: a critical review." Respiratory physiology & neurobiology 147.1 (2005): 39-49.
Page, Richard L., et al. "2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society." Journal of the American College of Cardiology 67.13 (2016): e27-e115.
Derbes, Vincent J., and Andrew Kerr Jr. "Valsalva's maneuver and Weber's experiment." (1955): 822-823.
Wenner, Megan M., et al. "Preserved autonomic function in amenorrheic athletes." Journal of Applied Physiology 101.2 (2006): 590-597.