Nijmegen Questionnaire (also: Nijmegen Hyperventilation Scale)

Abstract

The Nijmegen Questionnaire (NQ; Dutch: Nijmeegse Vragenlijst, also historically known as the Nijmeegse Hyperventilatieschaal or Nijmegen Hyperventilation Scale) is a widely recognized 16-item self-report psychometric instrument designed to screen for functional respiratory complaints, breathing pattern disorders, and hyperventilation syndrome (HVS), currently conceptualized within clinical literature as dysfunctional breathing (DB). Developed in 1983 at the Department of Pulmonology of the University of Nijmegen by Pieter van Doorn, Pierre Colla, and Hans Folgering, the questionnaire systematically captures the multiorgan somatic and psychological manifestations triggered by chronic or episodic hypocapnia, heightened autonomic reactivity, and psychophysiological distress. Each item is scored on a 5-point Likert scale ranging from 0 (never / nooit) to 4 (very often / zeer vaak), yielding a total cumulative score between 0 and 64. A clinical cut-off score of 23 or higher classically indicates the presence of functional respiratory complaints or hyperventilation-related symptomatology, demonstrating high sensitivity (approximately 91%) and specificity (approximately 95%) when benchmarked against clinical hyperventilation provocation testing. Psychometric evaluations of the scale have demonstrated robust internal consistency (Cronbach’s α typically ranging between .80 and .93 across healthy, asthmatic, and anxiety cohorts) and strong test-retest reliability (intraclass correlation coefficients commonly exceeding .80). Factor analytic investigations across clinical and community samples have identified multidimensional symptom clusters, predominantly loading onto respiratory, neurological/central, peripheral neurovascular, and psychological/affective dimensions. The instrument bridges pulmonary medicine, psychosomatics, behavioral therapy, and respiratory physiotherapy, serving as both an essential screening metric and a sensitive outcome measure for breathing retraining and psychological interventions.

Keywords

Nijmegen Questionnaire, Nijmeegse Vragenlijst, Hyperventilation Syndrome, Dysfunctional Breathing, Breathing Pattern Disorders, Respiratory Psychophysiology, Hypocapnia, Psychometrics, Somatization, Anxiety Sensitivity

Authors

The Nijmegen Questionnaire was originally designed, validated, and published in the early 1980s by a multidisciplinary clinical research team at the University of Nijmegen (now Radboud University) and the Dekkerswald Pulmonary Center in Groesbeek, The Netherlands:

• Pieter van Doorn, MSc: Clinical psychologist and researcher specializing in psychophysiological diagnostics and behavioral medicine, Department of Pulmonology and Department of Clinical Psychology, University of Nijmegen, Nijmegen, The Netherlands.
• Pierre Colla, PhD: Medical psychologist and psychotherapist, prominent in behavioral medicine interventions and psychosomatic pulmonary research, University of Nijmegen, Nijmegen, The Netherlands.
• Hans Folgering, MD, PhD: Emeritus Professor of Respiratory Pathophysiology and Pulmonologist, Department of Pulmonology, Radboud University Medical Center and University Lung Center Dekkerswald, Groesbeek/Nijmegen, The Netherlands. Dr. Folgering has been a pioneer in investigating the chemical control of breathing, respiratory sensation, and the pathophysiological mechanisms linking hypocapnia, psychophysiological stress, and functional breathlessness.

Purpose

The primary purpose of the Nijmegen Questionnaire is to provide a non-invasive, cost-effective, and standardized screening tool for identifying functional respiratory complaints and dysfunctional breathing patterns, historically characterized under the diagnostic umbrella of hyperventilation syndrome (HVS). Prior to the development of the NQ, the standard diagnostic procedure for hyperventilation syndrome relied heavily on the Hyperventilation Provocation Test (HVPT). The HVPT is an invasive, technically demanding laboratory procedure that requires forced voluntary hyperventilation followed by continuous capnography to measure end-tidal carbon dioxide partial pressure ($P_{\text{ET}}\text{CO}_2$) recovery curves, blood gas analyses, and the subjective reproduction of clinical symptoms. Van Doorn, Colla, and Folgering developed the NQ to address the need for a practical instrument capable of discriminating between functional respiratory complaints and primary organic pathology, as well as predicting HVPT outcomes without routinely exposing patients to physiological distress.

In clinical practice, the questionnaire functions across diverse medical and psychological disciplines. In pulmonology, it serves to detect dysfunctional breathing in individuals diagnosed with asthma, chronic obstructive pulmonary disease (COPD), or post-viral breathlessness syndromes, where functional respiratory disturbances often exacerbate subjective dyspnea beyond what objective spirometry or pulmonary function testing would predict. In cardiology and emergency medicine, the NQ is deployed to assess patients presenting with atypical non-cardiac chest pain, functional palpitations, and episodic dyspnea, aiding in the differential diagnosis of autonomic dysregulation versus ischemic heart disease. In psychiatry and clinical psychology, the NQ provides essential diagnostic insights into panic disorder, agoraphobia, generalized anxiety disorder, and somatic symptom disorders, where respiratory psychopathology frequently drives catastrophic cognitive misinterpretations of bodily sensations.

From a research standpoint, the NQ is utilized to quantify baseline symptom burden, evaluate the efficacy of therapeutic modalities—such as breathing retraining, capnometry-assisted biofeedback, cognitive behavioral therapy (CBT), and diaphragm rehabilitation—and explore the reciprocal feedback loops between systemic hypocapnia, autonomic arousal, and psychological anxiety. Theoretical rationale behind the instrument emphasizes that dysfunctional breathing is not merely a biochemical derangement of gas exchange, but a multidimensional psychophysiological disorder involving sensorimotor dysregulation of respiratory mechanics, altered interoception, and stress-induced somatic hyperawareness.

Psychological Construct

The psychological construct evaluated by the Nijmegen Questionnaire is functional respiratory complaints secondary to dysfunctional breathing and hyperventilation syndrome. This construct encompasses a broad constellation of somatic, cognitive, and affective symptoms that arise when ventilation exceeds metabolic demands, resulting in hypocapnia (reduced arterial partial pressure of carbon dioxide, $P_{\text{a}}\text{CO}_2$), acute or chronic respiratory alkalosis, systemic vasoconstriction, neuromuscular irritability, and concomitant autonomic hyperarousal. The construct integrates four primary interconnected domains:

1. Respiratory Mechanics and Subjective Breathlessness

This dimension captures the experiential distortions of breathing dynamics, including the conscious awareness of breathing rate, depth, and perceived ventilatory restriction. When individuals hyperventilate, thoracic (apical) breathing often replaces diaphragmatic respiration, leading to dynamic hyperinflation and persistent muscle fatigue of the accessory respiratory muscles. Items such as “Faster or deeper breathing” (Snellere of diepere ademhaling), “Shortness of breath” (Kortademigheid), and “Unable to breathe deeply” (Niet diep kunnen doorademen) reflect the subjective sensation of air hunger (dyspnea) and unsatisfied inspiration, which frequently occurs in the absence of mechanical airflow limitation.

2. Central and Neurological Manifestations

Cerebral vasoconstriction is an immediate physiological consequence of hypocapnia; a reduction in arterial $\text{CO}_2$ triggers rapid constriction of cerebral arterioles, diminishing cerebral blood flow by up to 30–40%. This intracranial hemodynamic shift produces central nervous system symptoms captured by items like “Dizzy spells” (Duizeligheid), “Blurred vision” (Wazig zien), and “Feeling confused” (Gevoel van verwardheid). Psychologically, these sensations intensify feelings of unreality, depersonalization, and spatial disorientation, which can initiate catastrophic escalation cycles in panic-prone patients.

3. Peripheral Neurovascular and Musculoskeletal Irritability

Systemic respiratory alkalosis shifts blood pH upward, causing a transient decrease in ionized serum calcium ($Ca^{2+}$) and magnesium. Hypocalcemia increases peripheral nerve axon excitability, precipitating spontaneous action potentials in sensory and motor nerve fibers. The NQ measures these peripheral manifestations through items such as “Tingling in fingers” (Tintelingen in de vingers; paresthesia), “Stiff fingers or arms” (Stijve vingers of armen; tetany or carpopedal spasm), and “Tightness around the mouth” (Strak gevoel rond de mond; circumoral paresthesia). Concurrently, sympathetic vasoconstriction diminishes cutaneous perfusion, manifesting as “Cold hands or feet” (Koude handen of voeten).

4. Affective, Visceral, and Cardiorespiratory Distress

Dysfunctional breathing is intrinsically intertwined with emotional distress and sympathetic autonomic activation. Items addressing “Feeling tense” (Gevoel van spanning) and “Feelings of anxiety” (Gevoel van angst) reflect the direct affective loading of the construct. Somatosensory cross-talk in the mediastinal and abdominal regions is represented by “Pain in the chest” (Pijn op de borst), “Tight feeling in the chest” (Beklemmend gevoel op de borst), “Palpitations” (Hartkloppingen), and “Bloated feeling in the stomach” (Opgeblazen gevoel in de buik), the latter often stemming from aerophagia (air swallowing) and diaphragmatic dyssynergia during hyperventilatory episodes.

Theoretical Framework

The theoretical framework underpinning the Nijmegen Questionnaire is rooted in cognitive-behavioral psychophysiology, the neurobiology of interoception, and the chemical regulation of respiration. At the core of this model is the interaction between central respiratory control centers within the brainstem, limbic emotional processing networks, and higher-order cortical interpretation of visceral feedback.

1. The Physiological Feedback Loop: Hypocapnic Alkalosis

The foundational physiological framework was articulated by respiratory physiologists including Hans Folgering, J. Gardner, and B. S. Lum. Under basal homeostasis, the medullary chemoreceptors adjust minute ventilation to maintain arterial $P_{\text{CO}_2}$ within narrow limits (approximately 35–45 mmHg). In hyperventilation syndrome, minute ventilation chronically or acutely exceeds metabolic demand, blowing off excess carbon dioxide. The resulting drop in $P_{\text{a}}\text{CO}_2$ triggers extracellular alkalosis, shifting the hemoglobin-oxygen dissociation curve to the left (the Bohr effect), thereby impairing tissue oxygen offloading. This creates a state of cellular hypoxia across cerebral, myocardial, and peripheral tissues despite normal or elevated systemic arterial oxygen saturation ($S_{\text{p}}\text{O}_2$).

2. The Psychophysiological and Cognitive Spiral (Clark’s Panic Model)

From a psychological perspective, the Nijmegen Questionnaire operationalizes concepts congruent with David M. Clark’s cognitive model of panic and Donald Klein’s suffocation false alarm theory. Clark postulated that panic attacks arise when physiological sensations—many of which are benign manifestations of hyperventilation or autonomic activation—are misattributed as signals of imminent physical or mental catastrophe (e.g., interpreting chest tightness and palpitations as an impending myocardial infarction, or lightheadedness and blurred vision as imminent syncope or stroke). This catastrophic misinterpretation fuels acute fear, triggering further sympathetic nervous system activation, which in turn accelerates minute ventilation, decreases carbon dioxide levels further, and intensifies the bodily symptoms. The NQ explicitly measures the physical manifestations that serve as fuel for this reciprocal positive-feedback loop.

3. The Interoceptive and Central Sensitization Paradigm

More recent contemporary frameworks contextualize the Nijmegen Questionnaire within modern neuroscience theories of predictive coding and interoception (e.g., A. D. Craig; Hugo Critchley). Functional respiratory complaints frequently persist in the absence of ongoing biochemical hypocapnia. Patients develop central sensitization and heightened interoceptive prediction errors regarding ventilatory effort. Conditioning, hypervigilance toward thoracic sensations, and fear of suffocation alter breathing mechanics (e.g., excessive rib cage excursion and chronic diaphragmatic inhibition) such that the perception of breathing becomes effortful and distressing. The NQ thus serves as an index of subjective interoceptive distress rather than a purely chemical capnometric readout.

Validity

The psychometric validity of the Nijmegen Questionnaire has been subjected to rigorous empirical evaluation across multiple clinical populations and linguistic adaptations since its inception in 1983.

1. Criterion and Diagnostic Validity

In the original validation study by van Doorn, Colla, and Folgering (1983), the NQ was benchmarked against the gold-standard Hyperventilation Provocation Test (HVPT). Using a threshold score of 23 out of 64, the questionnaire demonstrated high diagnostic utility:

• Sensitivity: Reported at approximately 91%, indicating high effectiveness in identifying individuals who exhibit delayed $P_{\text{ET}}\text{CO}_2$ recovery and symptom reproduction during standardized provocation.
• Specificity: Reported at approximately 95% when discriminating hyperventilating patients from healthy asymptomatic controls.

Subsequent investigations by van Dixhoorn and Duivenvoorden (1985) corroborated these findings, reporting that an elevated NQ score strongly separated patients diagnosed with functional cardiac and respiratory complaints from reference groups.

2. Construct and Convergent Validity

Convergent validity has been established through substantial correlations between the NQ and validated measures of anxiety, panic, and somatic distress. The NQ correlates strongly with:

• The State-Trait Anxiety Inventory (STAI; $r = .50$ to $.68$).
• The Beck Anxiety Inventory (BAI; $r = .60$ to $.72$).
• The Symptom Checklist-90-Revised (SCL-90-R) Somatization subscale ($r = .55$ to $.70$).
• The Anxiety Sensitivity Index (ASI; $r = .52$ to $.65$).

In respiratory cohorts, Thomas et al. (2001, 2003) demonstrated that in patients with asthma, elevated NQ scores (≥23) identify a distinct subpopulation (approximately 30% of adult asthmatics) with high functional morbidity, significantly lower disease-specific quality of life (measured via the Asthma Quality of Life Questionnaire [AQLQ]), and increased emergency healthcare utilization, independent of objective spirometric parameters (e.g., $\text{FEV}_1$).

3. Discriminant and Known-Groups Validity

Discriminant validity is supported by the NQ’s ability to differentiate between purely functional respiratory complaints and primary organic respiratory diseases where breathing pattern is unperturbed. While patients with severe panic disorder or functional dysphonia score significantly above the clinical cut-off (means often ranging from 26 to 34), well-controlled asthmatic patients or individuals with uncomplicated structural lung disease exhibit baseline scores comparable to healthy normative cohorts (means typically between 10 and 16).

Reliability

The Nijmegen Questionnaire exhibits consistently high reliability estimates across clinical and non-clinical populations, languages, and settings.

1. Internal Consistency

In the seminal psychometric investigations by van Doorn et al. (1983) and van Dixhoorn and Duivenvoorden (1985), internal consistency measured via Cronbach’s alpha (α) was reported between .82 and .87. Later validations in various international cohorts yielded similar values:

• Asthma and Primary Care: Thomas et al. (2001) reported Cronbach’s α of .89 in a large British primary care asthma sample ($N = 4,206$).
• Cardiorespiratory and Anxiety Clinics: Studies across outpatient populations have observed alpha coefficients ranging from .87 to .93, confirming that the 16 items represent a coherent overarching psychometric construct.
• Item-Total Correlations: Corrected item-total correlations generally range between .40 and .72. Items measuring breathing changes (“Faster or deeper breathing”), chest sensations (“Tight feeling in the chest”), and anxiety symptoms (“Feeling tense”) regularly demonstrate the strongest item-total correlations.

2. Test-Retest Reliability and Measurement Invariance

The stability of the instrument over time has been verified across various test-retest intervals in stable clinical participants:

• Short-Term Stability (1 to 2 weeks): Intraclass correlation coefficients (ICC) and Pearson correlation coefficients range between $r = .80$ and $.87$ in untreated, stable cohorts, indicating high temporal stability.
• Responsiveness to Clinical Change: Despite strong stability under unchanged conditions, the NQ is highly sensitive to therapeutic interventions. Studies evaluating behavioral respiratory therapy, capnography biofeedback, and diaphragmatic retraining routinely demonstrate significant reductions in NQ scores (often from baseline means of >28 down to <16 post-intervention; effect sizes Cohen’s $d$ frequently exceeding 0.80–1.20).

Factor Analysis

Although the Nijmegen Questionnaire is commonly utilized as a unidimensional composite score in clinical screening (with the total score serving as the primary diagnostic threshold), extensive Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA) have illuminated a multifaceted underlying structure reflecting the physiological diversity of hypocapnic symptoms.

1. Classic Factor Solution (van Dixhoorn & Duivenvoorden, 1985)

The landmark psychometric factor analysis performed by van Dixhoorn and Duivenvoorden identified a three-to-four factor oblique solution explaining over 50% of the common variance:

• Factor 1: Respiratory / Thoracic Complaints—Comprising items: 6 (Faster or deeper breathing), 7 (Shortness of breath), 8 (Tight feeling in the chest), 11 (Unable to breathe deeply), and 1 (Pain in the chest). Factor loadings range from .54 to .78.
• Factor 2: Central / Neurological Symptoms—Comprising items: 3 (Blurred vision), 4 (Dizzy spells), 5 (Feeling confused), and often 2 (Feeling tense). Factor loadings range from .51 to .74.
• Factor 3: Peripheral Neurovascular / Vasomotor Sensations—Comprising items: 10 (Tingling in fingers), 12 (Stiff fingers or arms), 13 (Tightness around the mouth), and 14 (Cold hands or feet). Factor loadings range from .48 to .81.
• Factor 4: Psychological / Autonomic Arousal—Comprising items: 2 (Feeling tense), 15 (Palpitations), 16 (Feelings of anxiety), and 9 (Bloated feeling in the stomach). Factor loadings range from .46 to .69.

2. Confirmatory Factor Analytic (CFA) Fit Indices

Modern structural equation modeling and CFA studies evaluating both hierarchical (bifactor) and correlated four-factor models have demonstrated acceptable-to-good model fit indices:

• Comparative Fit Index (CFI): Ranges between .91 and .95 across validated language adaptations.
• Tucker-Lewis Index (TLI): Typically > .90.
• Root Mean Square Error of Approximation (RMSEA): Values between .045 and .068 (90% CI [.038, .074]).
• Standardized Root Mean Square Residual (SRMR): Commonly < .06.

These findings substantiate the practice of utilizing the total sum score for broad screening while also allowing clinicians to profile specific subscale vulnerabilities (e.g., identifying patients with predominantly peripheral paresthesias versus those with isolated thoracic tightness and breathlessness).

Instrument / Measurement Tool

The operational specifications of the Nijmegen Questionnaire are summarized below:

• Test Type: Self-report screening inventory and clinical outcome measurement instrument.
• Target Population: Adults, adolescents, and older adults evaluated for functional respiratory complaints, breathing pattern disorders, asthma with disproportionate breathlessness, non-cardiac chest pain, panic disorder, and hyperventilation syndrome. (Validated pediatric versions and parental proxy adaptations also exist).
• Administration Format: Paper-and-pencil self-completion, digital survey, or clinician-assisted interview.
• Completion Time: Approximately 3 to 5 minutes.
• Item Count: 16 items.
• Response Scale: 5-point Likert scale (0 = nooit / never, 1 = zelden / rarely, 2 = soms / sometimes, 3 = vaak / often, 4 = zeer vaak / very often).
• Scoring System:
  • All 16 items are scored positively from 0 to 4.
  • There are no reverse-scored items.
  • The total score is derived by calculating the direct arithmetic sum of all 16 items: $\text{Total Score} = \sum_{i=1}^{16} \text{Item}_i$.
  • Theoretical score range: 0 to 64 points.
• Interpretation and Clinical Cut-off:
  • Score 0 – 18: Normal / Asymptomatic baseline range; typical of healthy community populations.
  • Score 19 – 22: Borderline / Subclinical functional complaints; mild respiratory dysregulation or physiological stress reactivity.
  • Score ≥ 23: Clinical threshold indicating positive screen for functional respiratory complaints / hyperventilation syndrome / dysfunctional breathing. Demonstrates high diagnostic agreement with positive capnographic hyperventilation provocation testing.

Permissions & Fee and Test Year

The Nijmegen Questionnaire was originally constructed and published in 1983 by Pieter van Doorn, Pierre Colla, and Hans Folgering. In its clinical and academic format, the instrument is generally considered to be in the public domain for research, academic, and non-commercial clinical evaluation purposes, provided appropriate attribution and scientific citation are granted to the original authors.

No royalty or user fees are required for routine individual clinical usage, non-funded academic dissertations, or scientific investigations. However, organizations seeking to incorporate the questionnaire into commercial digital health platforms, electronic medical record proprietary modules, or industry-sponsored clinical trials should review institutional copyright guidelines and obtain formal institutional approval from Radboud University Medical Center (Nijmegen, The Netherlands) or the respective copyright holders.

References

• Clark, D. M. (1986). A cognitive approach to panic. Behaviour Research and Therapy, 24(4), 461–470. https://doi.org/10.1016/0005-7967(86)90011-2
• Folgering, H., & Colla, P. (1978). Some anomalies in the control of PACO2 in patients with a hyperventilation syndrome. Bulletin Europeen de Physiopathologie Respiratoire, 14(5), 503–512.
• Thomas, M., McKinley, R. K., Freeman, E., & Foy, C. (2001). Prevalence of dysfunctional breathing in patients treated for asthma in primary care: cross sectional survey. BMJ, 322(7294), 1098–1100. https://doi.org/10.1136/bmj.322.7294.1098
• Thomas, M., McKinley, R. K., Freeman, E., Foy, C., & Prodger, P. (2003). Breathing retraining for dysfunctional breathing in asthma: a randomised controlled trial. Thorax, 58(2), 110–115. https://doi.org/10.1136/thorax.58.2.110
• van Dixhoorn, J., & Duivenvoorden, H. J. (1985). Efficacy of Nijmegen Questionnaire in recognition of the hyperventilation syndrome. Journal of Psychosomatic Research, 29(2), 199–206. https://doi.org/10.1016/0022-3999(85)90042-X
• van Dixhoorn, J., & Folgering, H. (2015). The Nijmegen Questionnaire and dysfunctional breathing. ERJ Open Research, 1(1), 00001-2015. https://doi.org/10.1183/23120541.00001-2015
• van Doorn, P., Colla, P., & Folgering, H. (1983). A checklist for hyperventilation: Nijmeegse Vragenlijst. In Proceedings of the Annual Meeting of the European Academy of Allergology and Clinical Immunology, Brussels, Belgium.

Items of the Scale