Hyperventilation syndrome

• Hyperventilation syndrome (HVS) represents a relatively common emergency department (ED) presentation.

• HVS is a condition in which minute ventilation exceeds metabolic demands, resulting in hemodynamic and chemical changes that produce characteristic dysphoric symptoms.

• Many patients with HVS do not manifest low PaCO2 during attacks.

• A better term for this syndrome might be behavioral breathlessness or psychogenic dyspnea, with hyperventilation seen as a consequence rather than a cause of the condition.

• Some patients may be physiologically at risk for the development of psychogenic dyspnea.

• Approximately 50% of patients with panic disorder and 60% of patients with agoraphobia manifest hyperventilation as a symptom, whereas only 25% of patients with HVS manifest panic disorder.

• Hyperpnea or hyperpnoea is increased depth of breathing when required to meet metabolic demand of body tissues, such as during or following exercise, or when the body lacks oxygen (hypoxia), for instance in high altitude or as a result of anemia.

• Tachypnea differs from hyperpnea in that tachypnea is rapid shallow breaths, while hyperpnea is deep breaths.

• In hyperpnoea, the increased breathing rate is desirable as it meets the metabolic needs of the body.

• In hyperventilation, the rate of ventilation is inappropriate for the body's needs (except in respiratory acidosis, when CO2 needs to be breathed off).

• The resulting decrease in CO2 concentration results in the typical symptoms of :

light-headedness, tingling in peripheries, visual disturbances etc.

• In hyperpnoea, there are generally no such symptoms

Pathophysiology• Patients with HVS tend to breathe by using the

upper thorax rather than the diaphragm, and this results in chronic over-inflation of the lungs.

• When stress induces a need to take a deep breath, the deep breathing is perceived as dyspnea.

• The sensation of dyspnea creates anxiety, which encourages more deep breathing, and a vicious circle is created.

Pathophysiology• Patients with panic disorder have a lower

threshold for the fight-or-flight response. • In susceptible patients, even minor stresses

can trigger the syndrome, which then tends to manifest with primarily psychiatric complaints (eg, fear of death, impending doom, or claustrophobia).

• It is believed that HVS patients tend to focus on somatic complaints related to the physiologic changes produced by hyperventilation.

Etiology• The cause of HVS is unknown, but some persons

who are affected appear to have an abnormal respiratory response to stress, sodium, lactate, and other chemical and emotional triggers, which results in excess minute ventilation and hypocarbia.

• In most patients, the mechanics of breathing are disordered in a characteristic way. When stressed, these patients rely on thoracic breathing rather than diaphragmatic breathing, resulting in a hyper-expanded chest and high residual lung volume.

• Because of the high residual volume, they are then unable to take a normal tidal volume with the next breath and consequently experience dyspnea.

Etiology• Proprioceptors in the lung and chest wall

signal the brain with a “suffocation alarm” that triggers release of excitatory neurotransmitters that are responsible for many of the symptoms such as palpitations, tremor, anxiety, and diaphoresis.

• The incidence of HVS is higher in first-degree relatives than in the general population, but no clear genetic factors have been identified.

Epidemiology• As many as 10% of patients in a general

internal medicine practice are reported to have HVS as their primary diagnosis.

• The peak incidence is between the ages of 15 and 55 years, but cases have been reported in all age groups except infants.

• HVS has a strong female preponderance: the female-to-male ratio may be as high as 7:1.

Prognosis• Patients with chronic HVS experience multiple

exacerbations throughout their lives.• Children who experience acute HVS often continue this

pattern into adulthood. • Many patients have associated disorders (eg,

agoraphobia) that may dominate the clinical picture. • Patients who are treated with breathing retraining, stress

reduction therapy, and various medications (eg, benzodiazepines or selective serotonin reuptake inhibitors [SSRIs]) experience significant reductions in the frequency and the severity of exacerbations.

• Death attributable to HVS is extremely rare.

Carpopedal spasm occurs when acute hypocarbia causes reduced ionized calcium and phosphate levels, resulting in involuntary contraction of the feet or (more commonly) the hands .

Cardiac symptoms• The chest pain associated with HVS usually has atypical

features, but on occasion, it may closely resemble typical angina.

• It tends to last hours rather than minutes, and is often relieved rather than provoked by exercise. It is usually unrelieved by nitroglycerin.

• The diagnosis of HVS should be considered in young patients without cardiac risk factors who present with chest pain, particularly if the pain is associated with paresthesias and carpo-pedal spasm.

• ECG abnormalities may include prolonged QT interval, ST depression or elevation, and T-wave inversion.

Cardiac symptoms• In patients with subcritical coronary artery

stenosis, the vasospasm induced by hypocarbia may be sufficient to provoke myocardial injury.

• The incidence of HVS is high among patients with mitral valve prolapse (MVP), and the chest pain associated with MVP may be due to hyperventilation.

• Prinzmetal angina (ie, coronary artery vasospasm) is triggered by HVS, but the chest pain associated with this syndrome normally would be expected to respond to nitrates or calcium channel blockers.

Central nervous system symptoms• Central nervous system (CNS) symptoms occur because

hypocapnia causes reduced cerebral blood flow (CBF).CBF decreases by 2% for every 1 mm Hg decrease in PaCO2.

• Symptoms of dizziness, weakness, confusion, and agitation are common . Patients may experience visual hallucinations, syncope or seizure .

• Paresthesias occur more commonly in the upper extremity and are usually bilateral. Perioral numbness is very common.

Gastrointestinal symptoms• (eg, bloating, belching, flatus, or epigastric pressure)

may result from aerophagia.

Metabolic changes• Acute metabolic changes result from intracellular shifts and

increased protein binding of various electrolytes during respiratory alkalosis.

• Acute secondary hypocalcemia can result in carpopedal spasm, muscle twitching, a prolonged QT interval, and positive Chvostek and Trousseau signs.

• Hypokalemia tends to be less pronounced than hypocalcemia but can produce generalized weakness.

• Acute secondary hypophosphatemia is common and may contribute to paresthesias and generalized weakness.

Chvostek’s sign is twitching of facial muscles in response to tapping over the area of the facial nerve Trousseau’s sign is carpopedal spasm that results from ischemia, such as that induced by pressure applied to the upper arm from an inflated sphygmomanometer cuff .

• Chvostek’s sign is neither sensitive nor specific for hypocalcemia, since it is absent in about one third of patients with hypocalcemia and is present in approximately 10% of persons with normal calcium levels.

• Trousseau’s sign is more sensitive and specific; it is present in 94% of patients with hypo-calcemia and in only 1% of persons with normal calcium levels.

Differential Diagnoses :• Asthma • Atrial Fibrillation• Myocardial Infarction• Diabetic Ketoacidosis• Metabolic Acidosis• Nasopharyngeal Stenosis• Pneumothorax, Pneumomediastinum• Pulmonary Embolism• Respiratory Distress Syndrome, Adult• Carbon monoxide poisoning• Panic Disorders

Approach Considerations• Upon a first attack of acute HVS, the diagnosis depends

on recognizing the typical constellation of signs and symptoms and ruling out the serious conditions that can cause the presenting symptoms.

• Acute coronary syndrome (ACS) and pulmonary embolism (PE) are the 2 most common serious entities that may present similarly to HVS.

• Clinical assessment is sufficient to rule these out. • A standard workup for atypical chest pain, including

pulse oximetry, chest radiography, and ECG, may still be warranted depending on the clinical picture.

Approach Considerations• Patients with a history of HVS who have undergone an

appropriate workup at some earlier time may not need any further laboratory evaluation in the setting of a recurrence. Recognition of the typical constellation of dyspnea, agitation, dizziness, atypical chest pain, tachypnea and hyperpnea, paresthesias, and carpopedal spasm in a young, otherwise healthy patient with an adequate prior evaluation is sufficient to make the diagnosis.

• A low pulse oximetry reading in a patient who is hyperventilating should never be attributed to HVS. The patient should always be evaluated for other causes of hyperventilation.

Approach Considerations

•ABG is indicated if any doubt exists as to the patient’s underlying respiratory status; it may be helpful when HVS-induced acidosis is suspected, or when shunting or impaired pulmonary gas exchange is considered.

Approach Considerations• ABG sampling confirms a compensated

respiratory alkalosis in a majority of cases. The pH is typically near normal, with a low PaCO2 and a low bicarbonate level.

• ABG sampling is also useful in ruling out toxicity from carbon monoxide poisoning, which may present similarly to HVS.

• Toxicology screening is indicated. • If acute PE is being considered, ELISA D-dimer

assay may be helpful.

Approach Considerations• Imaging studies are not indicated when the

diagnosis of HVS is clear. • Because PE can present with findings identical

to those of HVS, a first-ever episode of acute HVS may warrant V/Q scanning or CT pulmonary angiography to rule out perfusion defects.

• Chest radiography is indicated for patients who are at high risk for cardiac or pulmonary pathology.

Approach Considerations• ECG changes are common and may include the

following:1- ST depression or elevation2- Prolonged QT interval3- T-wave inversion4- Sinus tachycardia• Rebreathing into a paper bag is not recommended in the

field. Deaths have occurred in patients with acute myocardial infarction (MI), pneumothorax, and pulmonary embolism (PE) who were initially misdiagnosed with HVS and treated with paper bag rebreathing.

Breathing Techniques• Rebreathing into a paper bag is no longer a recommended

technique, because significant hypoxia and death have been reported

• . Moreover, carbon dioxide itself may be a chemical trigger for anxiety in these patients.

• Simple reassurance and an explanation of how hyperventilation produces the patient’s symptoms are usually sufficient to terminate the episode.

• Provoking the symptoms by having the patient voluntarily hyperventilate for 3-4 minutes often convinces the patient of the diagnosis.

Breathing Techniques• Most patients with HVS tend to breathe with the upper

thorax and have hyper-inflated lungs throughout the respiratory cycle. Because residual lung volume is high, they are unable to achieve full tidal volume and experience dyspnea.

• Physically compressing the upper thorax and having patients exhale maximally decreases hyperinflation of the lungs.

• Instructing patients to breathe abdominally, using the diaphragm more than the chest wall, often leads to improvement in subjective dyspnea and eventually corrects many of the associated symptoms.

What is “calm breathing”?• Calm breathing (sometimes called “diaphragmatic

breathing”) is a technique that helps you slow down your breathing when feeling stressed or anxious.

• Newborn babies naturally breathe this way, and singers, wind instrument players, and yoga practitioners use this type of breathing.

• Diaphragmatic breathing slows the respiratory rate, gives patients a distracting maneuver to perform when attacks occur, and provides patients with a sense of self-control during episodes of hyperventilation.

• This technique has been shown to be very effective in a high proportion of patients with HVS.

How to Do It? • Calm breathing involves taking smooth,

slow, and regular breaths.• Sitting upright is usually better than

lying down or slouching, because it can increase the capacity of your lungs to fill with air.

• It is best to 'take the weight' off your shoulders by supporting your arms on the side-arms of a chair, or on your lap.

How to Do It ?1. Take a slow breath in through the nose, breathing into

your lower belly (for about 4 seconds)2. Hold your breath for 1 or 2 seconds3. Exhale slowly through the mouth (for about 4 seconds)4. Wait a few seconds before taking another breath• About 6-8 breathing cycles per minute is often helpful to

decrease anxiety, but find your own comfortable breathing rhythm.

• These cycles regulate the amount of oxygen you take in so that you do not experience the fainting, tingling, and giddy sensations that are sometimes associated with overbreathing.

Pharmacologic Therapy• Benzodiazepines are useful in the treatment of hyperventilation

resulting from anxiety and panic attacks.• Lorazepam (ativan) is a sedative-hypnotic of the benzodiazepine

class that has a short time to onset of effect and a relatively long half-life.

• Diazepam (valium) depresses all levels of the CNS (eg, limbic and reticular formation), possibly by increasing the activity of GABA. It is considered second-line therapy for seizures.

• Paroxetine (paxil) is the alternative drug of choice for HVS. It is a potent selective inhibitor of neuronal reuptake of serotonin and has a weak effect on neuronal reuptake of norepinephrine and dopamine.