Frenzel maneuver

The middle ear is an air-containing space separated from the external environment by the tympanic membrane (ear drum) and connected to the nasopharynx by the Eustachian tube. The Eustachian tube has several physiological functions, including pressure regulation and ventilation of the middle ear, clearance of middle-ear secretions, and protection of the middle ear from nasopharyngeal sound and secretions.

Middle-ear pressure is influenced by gas exchange across the middle-ear mucosa and by intermittent gas flow through the Eustachian tube. Opening of the tube allows the pressure difference between the middle ear and nasopharynx to be reduced.

Rapid changes in ambient pressure can occur more quickly than passive middle-ear pressure regulation. During an increase in ambient pressure, such as during aircraft descent or a diver's descent, the pressure in the external auditory canal can therefore exceed that of the middle ear. The resulting inward pressure gradient across the tympanic membrane may cause discomfort, pain, retraction of the membrane, and, if sufficiently large or prolonged, barotrauma. Individuals whose Eustachian tubes do not open adequately specifically during changes in ambient pressure may have baro-challenge-induced Eustachian tube dysfunction.

Active equalization maneuvers attempt to reduce this pressure gradient by opening the Eustachian tubes or by generating a pressure in the nasopharynx sufficient to promote their opening.

During the Frenzel maneuver, the glottis is voluntarily closed, separating the upper airway from the lungs. The mouth and external nasal openings are also closed. Contraction of muscles of the floor of the mouth and of the pharynx then compresses the gas contained in the oral and nasopharyngeal spaces. This raises nasopharyngeal pressure and directs pressure toward the pharyngeal openings of the Eustachian tubes.

When the applied nasopharyngeal pressure is sufficient to overcome the opening pressure of a Eustachian tube, the tube opens and gas can pass into the middle-ear cavity. The maneuver therefore acts principally by generating a localized positive pressure in the upper airway rather than by pressurizing the thorax and lungs.

Descriptions used in diving instruction often characterize movement of the tongue as a piston-like component of the maneuver. Experimental descriptions are broader, however, and include coordinated contraction of the floor-of-mouth and pharyngeal musculature rather than defining the maneuver solely by tongue movement.

A prospective pressure-chamber study of 11 experienced breath-hold divers characterized Eustachian-tube opening during Frenzel, Valsalva and Toynbee maneuvers. The study found that the Frenzel maneuver was at least as effective as Valsalva in producing Eustachian-tube opening under the experimental conditions. Valsalva produced a higher Eustachian-tube opening pressure and a longer opening duration than Frenzel, whereas Toynbee produced a lower opening pressure and shorter duration. The small study population limits the extent to which these measurements can be generalized.

Several voluntary maneuvers can alter middle-ear pressure, but they differ in the way Eustachian-tube opening or nasopharyngeal pressure is produced.

Valsalva maneuver

The Valsalva maneuver is a forced expiratory effort against a closed airway. In middle-ear equalization, pressure generated within the chest and lungs is transmitted upward into the throat and nasopharynx, where it can force the Eustachian tubes open.

In practical terms, Valsalva uses the respiratory system to generate the pressure: the muscles of the chest and abdomen compress the gas in the lungs as though attempting to breathe out while the airway is closed. The diaphragm and other respiratory muscles are therefore part of a pressure-generating system involving the thorax and lungs.

The Frenzel maneuver works differently. The glottis is closed before pressure is generated, effectively separating the lungs and chest from the upper airway. Pressure is then produced within the much smaller volume of the mouth and nasopharynx by movements of the tongue, floor of the mouth and pharyngeal musculature. The maneuver therefore does not require the diver to generate increased intrathoracic pressure in order to equalize the middle ears.

This distinction is particularly relevant in breath-hold diving. During descent, increasing ambient pressure progressively compresses the gas contained in the lungs. At sufficiently small lung volumes, generating and transmitting pressure from the thorax by a Valsalva maneuver becomes increasingly difficult. Frenzel equalization is less dependent on this mechanism because the pressure used to open the Eustachian tubes is generated above the closed glottis.

This mechanistic difference does not establish either maneuver as universally superior or safer. Eustachian-tube anatomy and function vary between individuals, and the experimental evidence specific to Frenzel remains limited.

Toynbee maneuver

The Toynbee maneuver combines swallowing with closure of the external nasal openings. Unlike Valsalva and Frenzel, which can create a positive nasopharyngeal pressure to open the Eustachian tubes, Toynbee relies substantially on the muscular actions associated with swallowing and Eustachian-tube opening.

Voluntary tubal opening

Voluntary tubal opening, also known as béance tubaire volontaire (BTV) or the Delonca technique, involves voluntary activation of musculature associated with opening the Eustachian tubes without first generating a substantial nasopharyngeal overpressure. It is therefore physiologically distinct from the Frenzel maneuver and should not be considered a hands-free variant of Frenzel.

Aviation

Changes in atmospheric or cabin pressure during flight alter the pressure relationship between the external environment and the gas-containing middle ear. Difficulty opening the Eustachian tube is particularly relevant during descent, when ambient pressure increases and the middle-ear space must receive gas in order to restore the pressure balance across the tympanic membrane.

The Frenzel maneuver originated in the context of aviation medicine. Its later use in military aviation reflected the need for reliable active middle-ear equalization during rapid changes in barometric pressure such as dive bombing.

Underwater diving

Water pressure increases rapidly during descent, producing a corresponding pressure gradient across gas-filled body spaces unless their internal pressure is equalized. The middle ear is therefore particularly susceptible to diving-related barotrauma. Otological complications are among the most frequent medical problems associated with diving.

Although scuba and breath-hold divers face the same basic requirement to equalize middle-ear pressure during descent, the source and availability of respiratory gas differ substantially between the two forms of diving.

Scuba diving

In scuba diving, a demand regulator provides breathing gas approximately at the surrounding ambient pressure. The diver therefore continues to receive respiratory gas as depth increases. The middle ears, however, remain enclosed gas spaces whose pressure must be adjusted through Eustachian-tube opening. Frenzel is one of several maneuvers that can be used for this purpose.

Freediving

In freediving, the diver descends on a single breath. As ambient pressure rises, the volume of pulmonary gas progressively decreases. Consequently, deep breath-hold diving presents an additional problem not present to the same degree in scuba diving: the progressively compressed lungs become a less accessible source of gas for middle-ear equalization.

This distinction is particularly relevant to Valsalva equalization. Lindholm and Lundgren describe how, when the lungs have been compressed sufficiently, the expiratory muscles may no longer be capable of generating adequate pressure in the lungs and upper airways by Valsalva. They also describe the use by advanced breath-hold divers of techniques for moving small quantities of gas from the compressed lungs into the mouth and nasopharynx so that pressure equalization can subsequently be performed.

The Frenzel maneuver is consequently widely used in freediving because its pressure-generating phase does not depend on raising intrathoracic pressure. A prospective study of repetitive freediving found a preference for Frenzel among its participants and also demonstrated pressure-related middle-ear changes after repeated descents, emphasizing the importance of effective Eustachian-tube function and pressure equalization in the sport.

Frenzel equalization nevertheless still requires an adequate quantity of gas to be available in the upper airway. Closing the glottis changes how pressure is generated; it does not create additional gas. For this reason, management of the diminishing gas volume available for equalization becomes increasingly important in deep breath-hold diving.

Deep freediving and mouthfill equalization

At greater depths in breath-hold diving, progressive compression of pulmonary gas can make it increasingly difficult to replenish the gas available in the upper airway for middle-ear equalization. Deep freedivers may therefore use mouthfill equalization, in which a volume of gas is retained in the mouth and upper airway for use during continued descent. Mouthfill is regarded as a distinct equalization technique and is described separately from Frenzel in the diving-medicine literature.

The Frenzel maneuver is named after German otolaryngologist Hermann Frenzel, whose work included problems of the ear, nose and throat in aviation medicine. Modern experimental literature dates his first description of the maneuver to 1938.

The original publication is cited in later otolaryngological literature as:

Hermann Frenzel, Nasen-Rachendruckversuch zur Sprengung des Tubenverschlusses, Luftfahrtmed. Abh., volume 2, pages 203-205 (1938).

The citation appears in Richard A. Davison's 1965 review of middle-ear ventilation and independently in P. F. King's 1979 review of the Eustachian tube in flight medicine.

Frenzel subsequently contributed a chapter on otorhinolaryngology to German Aviation Medicine, World War II, published by the United States Government Printing Office in 1950. Later medical literature states that the maneuver was taught to military personnel during the Second World War.

The technique was subsequently adopted in underwater diving, where the same requirement to regulate middle-ear pressure occurs during descent through increasing ambient pressure. It has become particularly associated with breath-hold diving because of the physiological limitations imposed by progressive lung compression during deep descent.