Breathing assessment should always precede HRV biofeedback because dysfunctional breathing can frustrate training success. Clinicians may also find that correcting breathing mechanics can aid neurofeedback training.
Overbreathing may be the most common breathing problem. Its expulsion of CO2 can produce a spectrum of medical and psychological symptoms (Khazan, 2020).
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Waiting Room Assessment
Assessment should begin in the waiting room to observe breathing behaviors without reactivity and continue in the clinic. For example, a client's respiration rate may increase by more than 5 bpm after attaching breathing sensors. Graphic © tsyhun/Shutterstock.com.
Reception staff should covertly observe respiration rate, thoracic breathing, shoulder movement, gasping, sighing, yawning, and breath-holding. Graphic © Pixel-Shot/Shutterstock.com.
Clinical Assessment
1. Watch for restrictive clothing that could interfere with abdominal expansion and the downward movement of the diaphragm muscle. Graphic © kbrowne41/Shutterstock.com.
2. Look for a posture that could also restrict the abdomen. Graphic © Marcin Balcerzak/Shutterstock.com.
Restrictive clothing and poor ergonomics can increase respiration rates beyond a client's resonance frequency, lowering HRV.
3. Check for reverse breathing, in which the abdomen contracts during inhalation.
This breathing pattern can result in respiration rates that exceed the resonance frequency. In the screen capture below, the pink tracing shows instantaneous heart rate (HR), and the violet tracing shows respirometer expansion and contraction.
Caption: At the bottom left, the respirometer shows contraction instead of expansion during inspiration. Unlike ocean waves, the instantaneous heart rate and respirometer waveforms are disorganized and choppy.
4. Check for clavicular breathing, where the shoulders rise and fall during breathing.
Clavicular breathing often involves rapid breathing to compensate for shallow inhalation volumes. In the screen capture below, the pink tracing shows accessory muscle (e.g., trapezius and scalene) SEMG. The violet tracing shows respirometer expansion and contraction.
Caption: SEMG spikes over 5 microvolts (around 00:14:47 and 00:14:58) coincide with the last two inhalations, during which the client elevated their shoulders.
5. Check whether breathing is primarily thoracic or abdominal using covert observation and a respirometer.
Thoracic breathing can speed up respiration above your client's resonance frequency. In the screen capture below, the pink tracing shows instantaneous HR. The violet tracing shows respirometer expansion and contraction.
Caption: The mean respiration rate is 14.32, well above the client's likely resonance frequency, and the two waveforms are shallow and disorganized.
Compare this screen capture with the one below, which illustrates abdominal breathing. The mean respiration rate is 5.07. Both waveforms are sinusoidal with high amplitude and in-phase (their peaks and valleys coincide).
6. Check for apnea, which is the suspension of breathing. Don't confuse apnea with the normal brief pauses after inhalation and exhalation.
Apnea disrupts healthy breathing and can raise blood pressure. In the screen capture below, the pink tracing shows instantaneous HR, and the violet tracing shows respirometer expansion and contraction.
Caption: Toward the middle of the recording, the bottom of the inspirometer wave is flattened, denoting breath-holding.
7. Check respiration rate and amplitude (amount of respirometer movement). Thoracic breathing at rates at or above 16 bpm may be associated with overbreathing or hyperventilation syndrome (HVS). Neblett (2013) cautions that chronic pain patients may breathe faster than 20 bpm. The BioGraph ® Infiniti display below shows the shallow, rapid breathing that can characterize overbreathing.
8. Check breathing effort by monitoring the abdominal tracing for loss of a smooth sinusoidal pattern.
Caption: There are three inflection points in the screen capture below (marked by yellow arrows) where the second breathing cycle is distorted by effort.
9. Monitor accessory and frontal SEMG as a second index of breathing effort.
In the screen capture below, accessory SEMG is pink, and respirometer movement is violet.
Caption: The mean respiration rate is 19.95 bpm. See the elevated SEMG reading and reduced inspirometer expansion at the far right.
10. Check oxygen saturation (PO2) using a pulse oximeter. A range of 95%-98% is ideal. Hyperventilation may increase it to 100% (Gilbert, 2019). Measurements of clients with darkly pigmented skin may exaggerate saturation values. Graphic © TomoTaro/Shutterstock.com.
11. Check end-tidal CO2 using a capnometer. A value of 36 torr (5%) is normal, while values below 33 torr are seen in hyperventilation syndrome (HVS) and overbreathing. A healthy range is 35-45 torr. Values below 25 mmHg signal severe overbreathing, 25-30 mmHg, moderate-to-severe overbreathing, and 30-35 mmHg, mild-to-moderate overbreathing (Khazan, 2020).
Breathing Assessment Protocol
Breathing assessment requires an ECG or PPG sensor to monitor HRV, a respirometer to measure abdominal excursion and respiration rate, and a SEMG sensor to evaluate accessory muscle activity. A capnometer assessing end-tidal CO2 and an oximeter measuring PO2 are optional.
Dr. Donald Moss (2013) generously provided respiration rate and end-tidal CO2 data from a 53-year-old married woman diagnosed with agoraphobia and panic disorder. The hyperventilation challenge was crucial to this patient's assessment and was conducted by an experienced licensed clinical psychologist.
Despite breathing at 18 bpm during baseline, her end-tidal CO2 was normal. The hyperventilation challenge increased her respiration rate to 42 bpm, resulting in hypocapnia with an end-tidal CO2 of 26. During the recovery trial, her respiration rate decreased below baseline, but her end-tidal CO2 remained below the normal cutoff of 35 torr.
Hyperventilation Challenge Caution
A mild hyperventilation challenge is contraindicated for clients diagnosed with epilepsy, heart disease, kidney disease, panic disorder, and PTSD. Moss and Shaffer (2022) caution:
. . . deliberate hyperventilation is challenging both subjectively and medically. Practitioners should carefully screen patients and refrain from using the hyperventilation trial when there is a history of pulmonary or heart disorders. In addition, each patient should be instructed to cease the rapid breathing if the trial triggers discomfort (p. 54).
Summary of the Breathing Assessment Protocol
Clinicians may add the Stroop test followed by a recovery period. Inquire about color deficiency beforehand since this could invalidate the Stroop test and produce exceptional frustration.
Dr. Inna Khazan (2019) provided an example of a breathing assessment using the Stroop test. The client was a 30-year-old woman who was divorcing her alcoholic husband. She presented with anxiety and diverse symptoms (difficulty focusing, GI distress, headaches, lightheadedness, racing heart, and shortness of breath).
Caption: End-tidal CO2 remained below the normal (35-45 mmHg) range throughout the assessment. Although the client recovered from the math stressor, end-tidal CO2 further declined following the emotional stressor.
Nijmegen Questionnaire
Clinicians should consider administering the Nijmegen Questionnaire. A score of 23 out of 64 on suggests further screening for hyperventilation syndrome.
There are approximately 100,000 miles of blood vessels in the brain, with a flow rate of about 750 milliliters per minute in adults.
The graphic below shows reduced cerebral blood perfusion (depicted by dark colors) during overbreathing, producing the Nijmegen questionnaire's symptoms.
Glossary
accessory muscles: the sternocleidomastoid, pectoralis minor, scalene, and trapezius muscles, which are used during forceful breathing, as well as during clavicular and thoracic breathing.
apnea: breath suspension.
behavioral breathlessness syndrome: the perspective that hyperventilation is the consequence and not the cause of the disorder. The traditional model that hyperventilation results in reduced arterial CO2 levels has been challenged by the finding that many HVS patients have normal arterial CO2 levels during attacks.
capnometer: an instrument that monitors the carbon dioxide (CO2) concentration in an air sample (end-tidal CO2) by measuring the absorption of infrared light.
clavicular breathing: a breathing pattern that primarily relies on the external intercostals and the accessory muscles to inflate the lungs, resulting in a more rapid respiration rate, excessive energy consumption, and incomplete ventilation of the lungs.
diaphragm: the dome-shaped muscle whose contraction enlarges the vertical diameter of the chest cavity and accounts for about 75% of air movement into the lungs during relaxed breathing.
end-tidal CO2: the percentage of CO2 in exhaled air at the end of exhalation.
hyperventilation syndrome (HVS): a respiratory disorder that has been increasingly reconceptualized as a behavioral breathlessness syndrome in which hyperventilation is the consequence and not the cause of the disorder. The traditional model that hyperventilation results in reduced arterial CO2 levels has been challenged by the finding that many HVS patients have normal arterial CO2 levels during attacks.
overbreathing: a mismatch between breathing rate and depth due to excessive breathing effort and subtle breathing behaviors like sighs and yawns can reduce arterial CO2.
pulse oximeter: a device that measures dissolved oxygen in the bloodstream using a photoplethysmograph sensor placed against a finger or earlobe.
respiratory amplitude: the excursion of an abdominal strain gauge.
resonance frequency: the breathing rate that maximizes the most time-domain measurements of HRV.
respiratory sinus arrhythmia (RSA): HR acceleration during inspiration and deceleration during expiration.
respirometer: a sensor that changes resistance to a current as it expands and contracts during the respiratory cycle.
reverse breathing: the abdomen expands during exhalation and contracts during inhalation, often resulting in incomplete ventilation of the lungs.
thoracic breathing: a breathing pattern that primarily relies on the external intercostals to inflate the lungs, resulting in a more rapid respiration rate, excessive energy consumption, and incomplete ventilation of the lungs.
torr: a unit of atmospheric pressure, named after Torricelli, which equals 1 millimeter of mercury (mmHg) and is used to measure end-tidal CO2.
trapezius-scalene placement: the active SEMG electrodes are located on the upper trapezius and scalene muscles to measure respiratory effort.
Quiz
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References
Fried, R. (1987). The hyperventilation syndrome: Research and clinical treatment. John Hopkins University Press.
Gevirtz, R. N. (2005). Heart rate variability biofeedback in clinical practice. AAPB Fall workshop.
Gilbert, C. (2012). Pulse oximetry and breathing training. Biofeedback, 40(4), 137-141. https://doi.org/0.5298/1081-5937-40.4.04
Gilbert, C. (2019). A guide to monitoring respiration. Biofeedback, 47(1), 6-11. https://doi.org/10.5298/1081-5937-47.1.02
Kern, B. (2014). Hyperventilation syndrome. eMedicine.
Khazan, I., & Shaffer, F. (2019). Practical strategies for teaching your clients to breathe. Association for Applied Psychophysiology and Biofeedback 50th Annual Meeting, Denver, CO.
Khazan, I. (2020). The myths and misconceptions of heart rate variability. Association for Applied Psychophysiology and Biofeedback Virtual Conference.
Khazan, I. Z. (2013). The clinical handbook of biofeedback: A step-by-step guide for training and practice with mindfulness. John Wiley & Sons, Ltd.
Lehrer, P., Vaschillo, B., Zucker, T., Graves, J., Katsamanis, M., Aviles, M., & Wamboldt, F. (2013). Protocol for heart rate variability biofeedback training. Biofeedback, 41(3), 98-109. https://doi.org/10.5298/1081-5937-41.3.08
Moss, D., & Shaffer, F. (2022). A primer of biofeedback. Association for Applied Psychophysiology and Biofeedback.
Neblett, R. (2013). Personal communication about breathing patterns in chronic pain patients.
Peper, E., Gibney, K. H., Tylova, H., Harvey, R., & Combatalade, D. (2008). Biofeedback mastery: An experiential teaching and self-training manual. Association for Applied Psychophysiology and Biofeedback.
Shaffer, F., Bergman, S., & Dougherty, J. (1998). End-tidal CO2 is the best indicator of breathing effort [Abstract]. Applied Psychophysiology and Biofeedback, 23(2).
Shaffer, F., Bergman, S., & Henson, M. (1998). Description of the Truman breathing assessment protocol [Abstract]. Applied Psychophysiology and Biofeedback, 23(2).
Shaffer, F., Bergman, S., & White, K. (1997). Indicators of diaphragmatic breathing effort [Abstract]. Applied Psychophysiology and Biofeedback, 22(2), 145.
Shaffer, F., Mayhew, J., Bergman, S., Dougherty, J., & Irwin, D. (1999). Designer jeans increase breathing effort [Abstract]. Applied Psychophysiology and Biofeedback, 24(2), 124-125.
Shaffer, F., & Moss, D. (2006). Biofeedback. In Y. Chun-Su, E. J. Bieber, & B. Bauer (Eds.). Textbook of complementary and alternative medicine (2nd ed.). Informa Healthcare.
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