Hering Breuer Reflex – Voice Science

Definition

The Hering-Breuer reflex is a protective respiratory mechanism that prevents pulmonary overinflation and underinflation through vagal-mediated feedback. The inflation reflex inhibits inspiration when lungs expand beyond a certain threshold, while the deflation reflex stimulates inspiration when lung volume drops below functional residual capacity, with both components mediated by stretch receptors sending signals via the Vagus Nerve to the brainstem’s respiratory center.

Context

Relevance to Singing

For singers, the Hering-Breuer reflex becomes relevant at the extremes of breath management. Classical singers routinely begin phrases at 70-100% of vital capacity—lung volumes that approach or potentially exceed the reflex’s activation threshold in adults. At the opposite extreme, singers often extend phrases to very low lung volumes, well below functional residual capacity, potentially engaging the deflation reflex. The rapid “catch breaths” singers employ between phrases may involve deflation reflex activation, which generates strong inspiratory drive when lungs are partially depleted (Head, cited in Anaestheasier, 2025).

Understanding these reflexes provides physiological context for pedagogical concepts like avoiding “overcrowding the lungs” at full inspiration and the challenge of maintaining subglottal pressure at low lung volumes. While voluntary control dominates during singing, these automatic mechanisms may integrate with learned breath management strategies in ways that remain incompletely characterized.

Historical Discovery and Developmental Function

German-Austrian physiologists Ewald Hering and Josef Breuer first described the inflation reflex in 1868 through experiments demonstrating that sustained lung distention decreased inspiratory effort in anesthetized animals—establishing the crucial role of vagal feedback in self-regulating breathing (Vadhan and Tadi, 2023). English neurologist Henry Head later clarified that inflation and deflation reflexes represent distinct mechanisms, with the deflation response generating substantially stronger inspiratory effort than vagotomy alone (Anaestheasier, 2025).

The reflex serves dramatically different functions across the lifespan. In newborns, it maintains rhythmic breathing and regulates lung volume in an immature respiratory control system, with infants showing 90-100% increases in expiratory time when the reflex is activated (Landolfo et al., 2008). During postnatal development, the reflex undergoes habituation—progressive attenuation of its inhibitory effect—as the brainstem matures and shifts toward greater central control with reduced reliance on breath-by-breath vagal feedback (Dutschmann et al., 2014).

In adult humans, the inflation reflex threshold elevates substantially above normal tidal volumes, typically exceeding 1 liter above resting capacity (approximately 80-90% of vital capacity). This elevation initially led researchers to conclude the reflex was functionally insignificant during quiet breathing in adults (Widdicombe, 1961).

Scientific Basis

Receptor Characteristics and Neural Circuitry

The inflation reflex is mediated by slowly adapting pulmonary stretch receptors (SARs)—mechanoreceptors embedded within airway smooth muscle that utilize the PIEZO2 ion channel to sense lung distension (Nonomura et al., 2024). These receptors exhibit baseline activity at functional residual capacity, with firing frequency increasing progressively as lung volume rises, reaching maximum rates up to 205 Hz (Schelegle, 2003). Unlike rapidly adapting receptors, SARs maintain elevated discharge throughout sustained inflation.

Afferent signals travel via myelinated vagal fibers to “pump cells” in the nucleus tractus solitarius, which project GABAergic and glycinergic inhibitory signals to medullary inspiratory neurons, terminating inspiration and facilitating expiration (Bonham and McCrimmon, 1990; Ezure and Tanaka, 2004). The deflation reflex operates through a separate pathway that generates strong inspiratory drive when lung volume drops below functional residual capacity (Anaestheasier, 2025).

Threshold Elevation in Adults

While highly prominent in infants, the reflex undergoes postnatal habituation as the brainstem matures, shifting from breath-by-breath sensory dependence toward greater central control (Dutschmann et al., 2014). In adult humans, bilateral vagal blockade produces no apparent changes in resting breathing—a stark contrast to anesthetized animals (Widdicombe, 1961). However, sophisticated studies using pseudorandom mechanical unloading revealed that vagal feedback influences inspiratory timing when tidal volumes substantially exceed normal levels, typically above 1 liter beyond resting capacity (BuSha et al., 2001, 2002).

Evidence from Vocalization Research

Speech production studies demonstrate that vagal sensory information from pulmonary stretch receptors flows unmitigated during vocal tasks. Research on respiratory sinus arrhythmia during reading aloud showed no attenuation of low-level respiratory reflex mechanisms, contradicting hypotheses that reflexes must be suppressed for behavioral respiratory control (Reilly and Moore, 2003). Animal studies confirmed that vagal feedback from slowly adapting receptors signals the transition from inspiration to vocalization, operating similarly during vocalizations and rest breathing (Davis et al., 1993).

Pedagogical Considerations

Reflex Engagement at Extreme Lung Volumes

Classical singers commonly initiate phrases at 70-100% vital capacity to manage elastic recoil forces at high volumes (Mendes et al., 2017). If the adult inflation reflex threshold exceeds approximately 80-90% vital capacity, most singing occurs below activation threshold, limiting the reflex’s protective role except at extreme inspiration. Pedagogical cautions against “tanking up” or “overcrowding the lungs” align with biomechanical concerns—elastic recoil following Hooke’s Law means excessive inhalation increases subglottal pressure control demands, independent of reflex activation.

At the opposite extreme, singers routinely extend phrases to very low lung volumes, well below functional residual capacity. At these volumes, the deflation reflex generates strong inspiratory drive, potentially contributing to the challenge of maintaining controlled phonation at phrase endings. Singers must develop expiratory muscle strength to overcome both diminishing elastic recoil and reflex-driven inspiratory impulses when singing at low volumes.

Catch Breaths and Deflation Reflex

The rapid “catch breaths” singers employ between phrases—inspiration completed in fractions of a second—typically occur from partially depleted lungs. The deflation reflex, activated below functional residual capacity, could theoretically contribute to the rapid inspiratory drive needed for these quick breaths (Anaestheasier, 2025). Whether singers learn to utilize this reflex-generated drive or must consciously override it to maintain silent, efficient catch breaths remains uninvestigated.

Integration with Voluntary Control

Professional singers demonstrate distinct respiratory kinematics compared to untrained individuals, including greater abdominal contribution to volume changes, pre-phonatory inward abdominal movements, and predominant rib cage contribution during phonation (Binazzi et al., 2016). These patterns reflect voluntary control strategies optimizing subglottal pressure regulation throughout extended lung volume ranges.

Research demonstrates that cortical control can modulate reflex strength, altering both inspiratory-inhibitory and expiratory-promoting components (Zera et al., 2009). This suggests higher-level control may modify reflex gain during singing, allowing integration rather than override of automatic mechanisms. Evidence from speech production confirms that respiratory reflexes remain active during vocalization rather than being suppressed (Reilly and Moore, 2003), supporting the view that effective breath management involves integrating reflexive and voluntary control.

Common Misconceptions

Misconception: “The Hering-Breuer reflex controls all breathing during singing”

Reality: In adult humans, the HBR threshold is substantially elevated above normal tidal volumes. Classic studies demonstrate that vagal blockade in conscious adults produces no apparent changes in resting breathing patterns. The reflex only influences breathing when tidal volumes substantially exceed normal levels—typically greater than 1 liter above resting capacity. During most singing, voluntary cortical control dominates respiratory patterns, with the HBR playing a minimal direct role except potentially at extreme inspiratory volumes (Widdicombe, 1961; BuSha et al., 2001).

Misconception: “Respiratory reflexes are suppressed during vocalization to allow voluntary control”

Reality: Research on speech production demonstrates that vagal sensory information from pulmonary stretch receptors flows unmitigated during vocal production, with respiratory sinus arrhythmia patterns suggesting maintained vagal modulation. Rather than being suppressed, respiratory reflexes remain active during vocalization and likely integrate with voluntary control strategies. Studies found no evidence that low-level respiratory reflex mechanisms were attenuated during speech, contradicting earlier speculation that reflexes would be incompatible with behavioral respiratory tasks (Hoit et al., 2014).

Misconception: “Training at high lung volumes desensitizes the Hering-Breuer reflex in singers”

Reality: While respiratory muscle strength training in singers has demonstrated increased maximum inspiratory and expiratory pressures, no studies have directly investigated whether singing training produces measurable changes in HBR threshold, sensitivity, or central processing. Although the reflex demonstrates plasticity during postnatal development (habituation), and analogous plasticity exists in other sensory-motor systems, whether adult singers develop altered HBR characteristics through training remains an unanswered research question (Dutschmann et al., 2014; Mendes et al., 2017).

Related Terms

Also known as: HBR, Inflation Reflex, Hering-Breuer Inflation Reflex

See also: Vagus Nerve (carries sensory signals from lung stretch receptors), Breath Support (voluntary control strategies that may integrate with reflexive mechanisms)

References

Anaestheasier. 2025. “Hering-Breuer and the Respiratory Reflexes.” January 13, 2025. https://www.anaestheasier.com/hering-breuer-and-the-respiratory-reflexes/.

Binazzi, Benedetta, et al. 2016. “Breathing and Singing: Objective Characterization of Breathing Patterns in Classical Singers.” PLOS One 11(5): e0155084.

Bonham, Ann C., and Donald R. McCrimmon. 1990. “Neurones in a Discrete Region of the Nucleus Tractus Solitarius Are Required for the Breuer-Hering Reflex in Rat.” Journal of Physiology 427: 261-280.

BuSha, Barbara F., et al. 2001. “Identification of Respiratory Vagal Feedback in Awake Normal Subjects Using Pseudorandom Unloading.” Journal of Applied Physiology 90(6): 2330-2340.

BuSha, Barbara F., et al. 2002. “Termination of Inspiration by Phase-Dependent Respiratory Vagal Feedback in Awake Normal Humans.” Journal of Applied Physiology 93(3): 903-910.

Davis, Paul J., Su Ping Zhang, and Richard Bandler. 1993. “Pulmonary and Upper Airway Afferent Influences on the Motor Pattern of Vocalization Evoked by Excitation of the Mid-Brain Periaqueductal Gray of the Cat.” Brain Research 607(1-2): 61-80.

Dutschmann, Mathias, et al. 2014. “Learning to Breathe: Habituation of Hering-Breuer Inflation Reflex Emerges with Postnatal Brainstem Maturation.” Respiratory Physiology & Neurobiology 195: 44-49.

Ezure, Kazuhisa, and Ikuo Tanaka. 2004. “GABA, in Some Cases Together with Glycine, Is Used as the Inhibitory Transmitter by Pump Cells in the Hering-Breuer Reflex Pathway of the Rat.” Neuroscience 127(2): 409-417.

Reilly, Kevin J., and Christopher A. Moore. 2003. “Respiratory Sinus Arrhythmia During Speech Production.” Journal of Speech, Language, and Hearing Research 46(1): 164-177. https://doi.org/10.1044/1092-4388(2003/013).

Schelegle, Edward S. 2003. “Functional Morphology and Physiology of Slowly Adapting Pulmonary Stretch Receptors.” Anatomical Record Part A: Discoveries in Molecular, Cellular, and Evolutionary Biology 270(1): 11-16.

Mendes, Ana Paula, William S. Brown, and Christine Sapienza. 2017. “Effects of Respiratory Muscle Strength Training in Classically Trained Singers.” Journal of Voice 31(6): 760.e1-760.e11.

Nonomura, Kenta, et al. 2024. “A Vagal Reflex Evoked by Airway Closure.” Nature 626: 154-160.

Landolfo, Francesca, et al. 2008. “Hering–Breuer Reflex, Lung Volume and Position in Prematurely Born Infants.” Pediatric Pulmonology 43(8): 767-771. https://doi.org/10.1002/ppul.20855.

Trippenbach, Tadeusz. 1994. “Pulmonary Reflexes and Control of Breathing During Development.” Biology of the Neonate 65(3-4): 205-210.

Vadhan, Jason, and Prasanna Tadi. 2023. “Physiology, Herring Breuer Reflex.” In StatPearls. Treasure Island, FL: StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK551725/.

Widdicombe, J. G. 1961. “Respiratory Reflexes in Man and Other Mammalian Species.” Clinical Science 21: 163-170.

Zera, Tomasz, et al. 2009. “Cortical Control of Hering-Breuer Reflexes in Anesthetized Rats.” European Journal of Medical Research 14(Suppl 4): 1-5.