出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/07/24 13:31:32」(JST)
The Valsalva maneuver or Valsalva manoeuvre is performed by moderately forceful attempted exhalation against a closed airway, usually done by closing one's mouth, pinching one's nose shut while pressing out as if blowing up a balloon. Variations of the maneuver can be used either in medical examination as a test of cardiac function and autonomic nervous control of the heart, or to "clear" the ears and sinuses (that is, to equalize pressure between them) when ambient pressure changes, as in diving, hyperbaric oxygen therapy, or air travel.
The technique is named after Antonio Maria Valsalva,[1] a 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.
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The normal physiological response consists of four phases.[2]
Deviation from this response pattern signifies either abnormal heart function or abnormal autonomic nervous control of the heart. Valsalva is also used by dentists following extraction of a maxillary molar tooth. The maneuver is performed to determine if a perforation or antral communication exists.
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.[3][4][5] 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.[4][6][7][8] 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[4], and some can do so without moving their jaw at all. Opening can often be clearly heard by the practitioner, thus providing feedback that the maneuver was successful.
During swallowing or yawning, several muscles in the pharynx (throat) act to elevate the soft palate and open the throat. One of these muscles, the tensor veli palatini, also acts to open the eustachian tube. This is why swallowing or yawning is successful in equalizing middle ear pressure. Contrary to popular belief, the jaw does not pinch the tubes shut when it is closed. In fact, the eustachian tubes are not located close enough to the mandible to be pinched off. People often recommend chewing gum during ascent/descent in aircraft, because chewing gum increases the rate of salivation, and swallowing the excess saliva opens the eustachian tubes.
In a clinical setting the Valsalva maneuver will commonly be done either against a closed glottis, or against an external pressure measuring device, thus eliminating or minimizing the pressure on the Eustachian tubes. Straining or 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.
In diving, the Valsalva maneuver is often used on descent to equalise the pressure in the middle ear to the ambient pressure. If the Valsalva maneuver is conducted during ascent, residual air overpressure in the middle-ear can potentially be released through the Eustachian tubes. During decompression stops at the end of a dive, if the diver unwittingly slightly descends again and makes a Valsalva to relieve his ears, there exists a non-negligible risk to transfer nitrogen bubbles from one side of the heart to the other one if the foramen membrane is permeable. If some of the inert gas-laden blood passes through the patent foramen ovale (PFO), it avoids the lungs and the inert gas is more likely to form large bubbles in the arterial blood stream, causing decompression sickness.[citation needed]
A Valsalva maneuver at the end of a diving must never be attempted as it can cause a decompression accident with severe neurological consequences (gas bubbles in the brain or damages to the spinal cord). Repeated Valsalva maneuvers are also suspected to increase the permeability of the foramen for divers at risk.[citation needed]
The Valsalva maneuver may be used to arrest episodes of supraventricular tachycardia.[9][10] The maneuver can sometimes be used to diagnose heart abnormalities, especially when used in conjunction with echocardiogram.[11] 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 most other murmurs, including aortic stenosis and atrial septal defect.
| Effect of Valsalva | Cardiac Finding |
|---|---|
| Decreased | |
| Aortic Stenosis | |
| Pulmonic Stenosis | |
| Tricuspid Regurgitation | |
| Increased | |
| Hypertrophic cardiomyopathy, mitral valve prolapse |
The Valsalva maneuver works by decreasing preload to the heart. A complementary maneuver for differentiating disorders is the Handgrip maneuver, which increases afterload.
The Valsalva maneuver alters heart rate through sympathetic stimulation (e.g. the accelerator nerve). Neuro-muscular junctions at the sinoatrial node (SAN) release the neurotransmitter norepinephrine(noradrenaline), which increases the SAN's depolarisation rate.
These effects decrease the time between pacemaker action potentials, which results in a faster heartbeat. In later phases of the Valsalva maneuver (phases II and III), heart rate is reduced due to parasympathetic interplay.
The Valsalva maneuver is used to aid in the clinical diagnosis of problems or injury in the nerves of the cervical spine.[12] Upon performing the Valsalva maneuver, intraspinal pressure slightly increases. Thus, neuropathies or radicular pain may be felt or exacerbated, and this may indicate impingement on a nerve by an intervertebral disc or other part of the anatomy. Headache and pain upon performing the Valsalva maneuver is also one of the main symptoms in Arnold–Chiari_malformation. The Valsalva maneuver may be of use in checking for a dural tear following certain spinal operations such as a microdiscectomy. An increase in intra-spinal pressure will cause CSF to leak out of the dura causing a headache.[citation needed]
The Valsalva maneuver is used to aid diagnosis of intrinsic sphincteric deficiency (ISD) in urodynamic tests. Valsalva leak point pressure is the minimum vesicular pressure that is associated with urine leakage. Although there is no consensus on the threshold value, values > 60 cm H2O are commonly considered to indicate hypermobility of the bladder neck and normal sphincter function.[13] Also, when examining women with pelvic organ prolapse, asking the patient to perform the Valsalva maneuver is used to demonstrate maximum pelvic organ descent.[14]
A pathologic syndrome associated with the Valsalva maneuver is Valsalva retinopathy.[15] 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.
On 25 May 2011, NASA reported that during the second spacewalk of Space Shuttle mission STS-134, astronaut Drew Feustel was able to clear tears from his eye by wiggling down far enough in his Extravehicular Mobility Unit (spacesuit) to make use of "a spongy device called a Valsalva that is typically used to block the nose in case a pressure readjustment is needed."[16] The tears came about because some of a film of anti-fogging agent (liquid soap) came free from the inside of the helmet and floated into his eye.
In November 2011 ESA astronaut Samantha Cristoforetti posted on Twitter a picture of her demonstrating the use of the Valsalva device in the Sokol space suit.[17]
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