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Valsalva maneuver
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The Valsalva maneuver is performed by forcibly exhaling against a closed airway. Variations of the maneuver can be used either in medicine, as a test of cardiac function and autonomic nervous control of the heart or to "clear" the ears and sinuses (equalize pressure) when ambient pressure changes, as in diving or aviation.
The technique is named after Antonio Maria Valsalva, the 17th Century physician and anatomist from Bologna, whose principal scientific interest was the human ear.
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Encyclopedia
The Valsalva maneuver is performed by forcibly exhaling against a closed airway. Variations of the maneuver can be used either in medicine, as a test of cardiac function and autonomic nervous control of the heart or to "clear" the ears and sinuses (equalize pressure) when ambient pressure changes, as in diving or aviation.
The technique is named after Antonio Maria Valsalva, the 17th Century physician and anatomist from Bologna, whose principal scientific interest was the human ear. He described the Eustachian tube and the maneuver to test its patency (openness). He also described the use of this maneuver to expel pus from the middle ear.
A modified version is done by expiring against a closed glottis. This will elicit the cardiovascular responses described below but will not force air into the eustachian tubes.
Physiological response
The normal physiological response consists of 4 phases, which are marked on the figure at right:
- Initial pressure rise: On application of expiratory force, pressure rises inside the chest forcing blood out of the pulmonary circulation into the left atrium. This causes a mild rise in blood pressure.
- Reduced venous return and compensation: Return of systemic blood to the heart is impeded by the pressure inside the chest. The output of the heart is reduced and blood pressure falls. This occurs from 5 to about 14 seconds in the illustration. The fall in blood pressure reflexively causes blood vessels to constrict with some rise in pressure (15 to 20 seconds). This compensation can be quite marked with pressure returning to near or even above normal, but the cardiac output and blood flow to the body remains low. During this time the pulse rate increases.
- Pressure release: The pressure on the chest is released, allowing the pulmonary vessels and the aorta to re-expand causing a further initial slight fall in pressure (20 to 23 seconds) due to decreased left ventricular return and increased aortic volume, respectively. Venous blood can once more enter the chest and the heart, cardiac output begins to increase.
- Return of cardiac output: Blood return to the heart is enhanced by the effect of entry of blood which had been dammed back, causing a rapid increase in cardiac output and of blood pressure (24 seconds on). The pressure usually rises above normal before returning to a normal level. With return of blood pressure, the pulse rate returns towards normal.
Deviation from this response pattern signifies either abnormal heart function or abnormal autonomic nervous control of the heart.
Valsalva is also used by dentist following extraction of a maxillary molar tooth. The maneuver is performed to determine if a perforation or antral communication exist.
Normalizing middle ear pressures
When rapid ambient pressure increase occurs as in diving or aircraft descent, this pressure tends to hold the Eustachian tubes closed, preventing pressure equalization across the ear drum, with painful results. To avoid this painful situation, divers, caisson workers and aircrew attempt to open the Eustachian tubes by swallowing, which tends to open the tubes, allowing the ear to equalize itself.
If this fails, then the Valsalva maneuver may be used. It should be noted this maneuver, when used as a tool to equalize middle ear pressure, carries with it the risk of auditory damage from over pressurization of the middle ear. It is safer, if time permits, to attempt to open the Eustachian tubes by swallowing a few times, or yawning. The effectiveness of the "yawning" method can be improved with practice; some people are able to achieve release or opening by moving their jaw forward or forward and down, rather than straight down as in a classical yawn. Opening can often be clearly heard by the practitioner, thus providing feedback that the maneuver was successful.
The reason opening the mouth is successful while trying to open the Eustachian tubes is because when the jaw is closed, it pinches these tubes, restricting flow. Opening the mouth relieves the pinching. Thus, while using the Valsalva maneuver, having the jaw open (with lips shut) will make it much more successful. This is also the reason some people recommend to chew gum during an airplane descent, because the chewing motion of the jaw opens the Eustachian tubes.
Note that in a clinical setting the Valsalva maneuver will be done either against a closed glottis, or against an external pressure measuring device, in each case either eliminating or minimizing the pressure on the Eustachian tubes. Straining, blowing against resistance as in blowing up balloons has a Valsalva effect and the fall in blood pressure can result in dizziness and even fainting.
Cardiology
The Valsalva maneuver may be used to arrest episodes of supraventricular tachycardia. The maneuver can sometimes be used to diagnose heart abnormalities, especially when used in conjunction with echocardiogram. For example, the Valsalva maneuver classically increases the intensity of hypertrophic cardiomyopathy murmurs, viz. those of dynamic subvalvular left ventricular outflow obstruction; whereas it decreases the intensity of all other murmurs, including aortic stenosis and atrial septal defect.
The Valsalva maneuver alters heart rate through parasympathetic stimulation (i.e. the Vagus Nerve/ Cranial Nerve X). Vagal neuro-muscular junctions at the sinoatrial node release the neurotransmitter acetylcholine (ACh). Ligand-receptor binding causes several effects:
1. ACh lowers the permiability of muscle cell membranes to sodium and calcium ions, resulting in a slower rate of pacemaker depolarization. Hence, the cell takes longer to generate an action potential.
2. ACh also lowers the number of available L-type calcium channels, which elevates the cell's threshold for action potentials. Thus, the cell needs to depolarize more than normal to fire an action potential.
3. New research suggests that ACh also activates latent potassium channels in the cell membrane. Increased potassium ion influx decreases the maximum diastolic potential of the cell. That is, hyperpolarization decreases the membrane potential of the pacemaker cells.
These effects elongate the time between pacemaker action potentials, which results in a slower heartbeat and a mechanism to interrupt or diagnose arrhythmia. In later phases of the valsalva maneuver (Phases II and III), heart rate elevates due to sympathetic interplay.
Neurology
The Valsalva maneuver is used to aid in the clinical diagnosis of problems or injury in the nerves of the cervical spine. Upon the exertion of pressure, neuropathies or radicular pain may be felt, and may indicate impingement on a nerve by an intervertebral disc or other part of the anatomy.
Valsalva retinopathy
A pathologic syndrome associated with the Valsalva maneuver is Valsalva retinopathy. It presents as preretinal hemorrhage (bleeding in front of the retina) in people with a history of transient increase in the intrathoracic pressure. The bleeding may be associated with a history of heavy lifting, a forceful coughing, straining on the toilet, or vomiting. The bleeding may cause a reduction of vision if it obstructs the visual axis. Patients may also note floaters in their vision. Usually a full recovery of vision is made.
See also
External links
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