Last updated June 26, 2025
Definition
Hyperventilation Syndrome (HVS) is a functional respiratory disorder characterized by episodic inappropriate overbreathing, usually in response to emotional stress or panic. This causes hypocapnia, leading to respiratory alkalosis and a wide range of symptoms — many of which mimic life-threatening emergencies like PE, ACS, or seizure.
Pathophysiology
- Respiratory alkalosis: ↓ CO₂ from rapid/deep breathing → vasoconstriction & altered calcium binding
- Cerebral vasoconstriction: leads to dizziness, paresthesias, visual changes
- Calcium shift: alkalemia promotes albumin binding of Ca²⁺ → relative hypocalcemia → perioral numbness, carpopedal spasm
- Sympathetic surge: anxiety → ↑ catecholamines → tachycardia, chest tightness
Clinical Features
Symptom Category | Common Presentations |
Neurologic | Dizziness, paresthesias (hands, perioral), visual changes, headache |
Respiratory | Air hunger, chest tightness, sighing, tachypnea |
Cardiac | Palpitations, non-anginal chest pain |
Other | Nausea, fatigue, globus sensation, tremor |
Even though the patient’s symptoms are subjective and may not have clear physical findings, they tend to recur in a consistent pattern during repeated episodes, especially under similar stress or triggers.
HVS Subtypes
- Panic-associated HVS – sudden, obvious emotional trigger
- Chronic HVS – baseline dyspnea, worsens under stress
- Situational – e.g. workplace, social setting
- Somatoform – minimal anxiety reported, symptoms dominate
Don’t anchor on “anxiety” in undifferentiated dyspnea — use decision tools (Wells, HEART, PERC) to avoid premature closure, especially on first presentations.
Red Flags and Differential Diagnosis
Red Flag | Considerations |
Hypoxia, abnormal vitals | PE, ACS, pneumonia |
Unilateral neuro symptoms | Stroke, TIA |
Drug exposure or toxidrome | Salicylates, simtlants (cocaine, ampheramines), carbon monixide, cyanide, theophylline |
Persistent metabolic findings | DKA, sepsis, acidosis |
Toxic-induced hyperventilation often has a mixed or metabolic acidosis picture — unlike the isolated respiratory alkalosis of HVS.
ED Management
Workup
Risk stratify first — don’t over-test. Proceed with diagnostics only if uncertainty exist.
Test | Purpose | Expected Findings in HVS |
Vitals | Rule out hypoxia, shock | Normal SpO₂, mild tachypnea |
Blood Gas (VBG or ABG) | Confirm alkalosis | ↓ PaCO₂, ↑ pH |
ECG | Screen for ACS, PE | Sinus tachycardia, otherwise normal |
CXR | Rule out pneumonia, pneumothorax | Normal |
D-dimer ± CTA Chest | If PE cannot be ruled out clinically | Use risk scores to guide |
Stepwise ED Approach:
- Provide a calm environment to the best of your ability
- Explain diagnosis gently and validate symptoms
- Coach controlled breathing technqiues
- Short-acting benzodiazepine (if severe or refractory): Lorazepam 0.5–1 mg PO/SL/IV
- Address underlying anxiety: Reinforce safety, offer follow-up with PCP or behavioral health
Breathing techniques
Paper bag rebreathing is no longer recommended due to the risk of hypoxia in patients with undiagnosed organic pathology (e.g., PE, asthma, metabolic acidosis). Though older sources mention it cautiously, modern EM practice favors safe, supervised breathing strategies. Historically, paper bag breathing aimed to correct acute hypocapnia by rebreathing exhaled CO₂ — but no high-quality evidence supports its clinical efficacy.
Evidence-based alternatives include:
- Slow, Deep Breathing (0.1 Hz / ~6 breaths per minute)
- Enhances vagal tone, increases heart rate variability, and reduces state anxiety
- Improves baroreflex sensitivity and supports emotional regulation via the central autonomic network
- Useful in both younger and older adults
- Diaphragmatic (Abdominal) Breathing
- Emphasizes abdominal expansion on inhalation and slow, prolonged exhalation
- Shown to reduce symptoms of HVS and anxiety when practiced over 2–3 months
- Benefits are linked to slower respiratory rate, not necessarily CO₂ normalization
- Pursed-Lip Breathing & Long Exhalations
- Commonly used in acute dyspnea and anxiety episodes
- Can be combined with:
- Forward-leaning posture
- Handheld fan
- Relaxation training
- Promotes rapid symptom relief and reduces air hunger
- Mindfulness & Breath Awareness
- Directing attention to the act of breathing helps interrupt panic loops
- Forms the foundation of many CBT and mindfulness-based therapies for panic and dyspnea
Avoid dismissing symptoms as “just anxiety” This may leads to future fear and recurrence. Instead, validate, educate, and reframe the experience using functional and physiologic language.
Pearls & Pitfalls
- Pearl: Paresthesias + perioral numbness + carpopedal spasm = respiratory alkalosis
- Pitfall: Diagnosing HVS without ruling out real emergencies
- Insight: Many patients with recurrent HVS have undiagnosed panic or somatic symptom disorder
- Teach: Use non-dismissive terms like “stress-related breathing episodes” when discharging
Disposition
- Most patients can be safely discharged after reassurance and education
- Provide verbal and/or written explanation of symptoms
- Normalize the experience
- Consider anxiety resources, primary care or psych follow-up
References
- Buttaravoli P, Stair TO. Minor Emergencies. 4th ed. Elsevier; 2021.
- Chin P, Gorman F, Beck F, et al. A systematic review of brief respiratory, embodiment, cognitive, and mindfulness interventions to reduce state anxiety. Front Psychol. 2024;15:1412928. doi:10.3389/fpsyg.2024.1412928.
- Gardner WN. The pathophysiology of hyperventilation disorders. Chest. 1996;109(2):516–534. doi:10.1378/chest.109.2.516.
- Han JN, Stegen K, De Valck C, Clément J, Van de Woestijne KP. Influence of breathing therapy on complaints, anxiety and breathing pattern in patients with hyperventilation syndrome and anxiety disorders. J Psychosom Res. 1996;41(5):481–493. doi:10.1016/s0022-3999(96)00220-6.
- Leyro TM, Versella MV, Yang MJ, et al. Respiratory therapy for the treatment of anxiety: meta-analytic review and regression. Clin Psychol Rev. 2021;84:101980. doi:10.1016/j.cpr.2021.101980.
- Lum LC, Goh LG, Chan ST. Hyperventilation syndrome: an overlooked diagnosis in the ED. Emerg Med J. 2003;20(4):388–389. doi:10.1136/emj.20.4.388.
- Nelson LS, Howland MA, Lewin NA, et al. Goldfrank’s Toxicologic Emergencies. 11th ed. McGraw Hill; 2019.
- Raz M, Pouryahya P, eds. Decision Making in Emergency Medicine: Biases, Errors and Solutions. Springer; 2021.
- Rosen’s Emergency Medicine: Concepts and Clinical Practice. 8th ed. Elsevier; 2014.
- Schloesser K, Eisenmann Y, Bergmann A, Simon ST. Development of a brief cognitive and behavioral intervention for the management of episodic breathlessness—a Delphi survey with international experts. J Pain Symptom Manage. 2021;61(5):963–973.e1. doi:10.1016/j.jpainsymman.2020.09.034.
- Szuhany KL, Simon NM. Anxiety disorders: a review. JAMA. 2022;328(24):2431–2445. doi:10.1001/jama.2022.22744.
- Walls RM, Hockberger RS, Gausche-Hill M, et al. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 8th ed. Elsevier; 2014.