Hyperventilation Syndrome and Hypocalcemia: A Unique Case in Autism Spectrum Disorder.

This case report delves into the rare occurrence of hyperventilation syndrome (HVS) with hypocalcemia in an 18-year-old female diagnosed with autism spectrum disorder (ASD). The rare occurrence highlights the importance of recognizing the potential association between HVS, hypocalcemia, and ASD, emphasizing the need for comprehensive evaluation and management strategies in individuals with ASD presenting with unusual symptoms. Despite ongoing psychotherapeutic treatment, the patient's clinical examination revealed ASD-related communication anomalies. Treatment with Escitalopram resolved panic attacks but left residual anxiety. During an emergency room visit for menstrual-related abdominal pain, a hyperventilation crisis ensued, leading to respiratory alkalosis and hypocalcemia. Swift intervention, including closed mask ventilation and electrolyte infusion, successfully alleviated symptoms. Follow-up assessments indicated normal thyroid function and vitamin D levels. The case highlights the necessity for clinicians to consider electrolyte imbalances in anxiety attacks among ASD patients, emphasizing the importance of timely management for patient safety. The intricate interplay between hyperventilation syndrome, anxiety, and hypocalcemia in ASD patients is explored, offering valuable insights for the nuanced understanding and comprehensive assessment of such cases.

Exercise ventilatory response after COVID-19: comparison between ambulatory and hospitalized patients.

Inefficient ventilatory response during cardiopulmonary exercise testing (CPET) has been suggested as a cause of post-COVID-19 dyspnea. It has been described in hospitalized patients (HOSP) with lung parenchymal sequelae but also after mild infection in ambulatory patients (AMBU). We hypothesize that AMBU and HOSP have different ventilatory responses to exercise, due to different etiologies. We analyzed CPET realized between July 2020 and May 2022 of patients with persisting respiratory symptoms 3 mo after COVID-19. Chest computed tomography (CT) scan, pulmonary function tests, quality of life, and respiratory questionnaires were collected. CPET data were specifically explored as a function of ventilation (V̇e) and time. Seventy-nine consecutive patients were included (42 AMBU and 37 HOSP, median: 54 [44-60] yr old, 57% female). Patients were hospitalized for a median of 20 [8-34] days, with pneumonia (41%) or acute respiratory distress syndrome (ARDS; 30%). Among HOSP, 12(32%) patients had abnormal values for spirometry and 18(51%) for carbon monoxide diffusing capacity (P < 0.001). CPET showed no differences between AMBU and HOSP in peak absolute O2 uptake (V̇o2) (1.59 [1.22-2.11] mL·min-1; P = 0.65). Tidal volume (VT) as a function of V̇e, was lower in AMBU than in HOSP (P < 0.01) toward the end of exercise. The slope of the V̇e-CO2 production was higher than normal in both groups (30.9 [26.1-34.3]; P = 0.96). In conclusion, the severity of COVID-19 did not influence the exercise capacity, but AMBU demonstrated a less efficient ventilatory response to exercise as compared with HOSP. CPET with exploration of data as a function of V̇e and throughout the exercise better unveil ventilatory inefficiency.NEW & NOTEWORTHY We evaluated the exercise ventilatory response in patients with persisting dyspnea after severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection. We found that despite similar peak power and peak absolute O2 uptake, tidal volume as a function of ventilation was lower in ambulatory than in hospitalized patients toward the end of exercise, reflecting ventilatory inefficiency. We call for evaluation of minute ventilation with the exploration of data throughout the exercise and not only peak data to better unveil ventilatory inefficiency.

The Effect of Hyperventilation Syndrome on Ionized and Serum Calcium: A Case Presentation in the Emergency Department.

Hyperventilation syndrome is described as a constellation of symptoms that are typically benign but can become a medical emergency in the setting of severe metabolic derangement secondary to shifts in a patient's pH. A 36-year-old male with a history of intravenous (IV) drug abuse presented to the emergency department (ED) in distress, complaining of diffuse muscle cramping with tetany and peripheral vasospasm. This case report discusses his initial ED testing and treatment when ionized calcium was low and serum calcium was high.

[Hyperventilation syndrome, definition, diagnostic and therapy]. / Le syndrome d'hyperventilation, définition, diagnostic et thérapeutique.

Hyperventilation syndrome (HVS) is a frequent disorder of which the etiology is unclear. Diagnosis is based on the ruling out of organic disease and, more positively, on results of the Nijmegen questionnaire, reproduction of symptoms during the hyperventilation provocation test (HPVT), and detected hypocapnia. Treatment is based on targeted respiratory physiotherapy consisting in voluntary hypoventilation and instructions to the patient on regular respiratory exercise over an appreciable period of time. Additional research is needed to evaluate the validity of current investigative tools leading to the diagnosis of hyperventilation syndrome and to appraise the efficacy of current respiratory physiotherapy methods.

Hyperventilation syndrome in children with asthma.

BACKGROUND: Hyperventilation syndrome (HVS) may be associated with asthma. In the absence of a gold standard diagnosis for children, its impact on asthma has been rarely assessed. OBJECTIVE: To assess the impact of HVS on the symptoms and lung function of children with asthma and determine the diagnostic value of the Nijmegen questionnaire in comparison to a hyperventilation test (HVT). METHODS: Data from asthmatic children followed in the department of Pediatric Pulmonology of Necker Hospital and explored for HVS were retrospectively analyzed. HVS was diagnosed by a positive HVT. Asthma exacerbations, control and lung function were assessed in children with or without a positive HVT. The sensitivity and specificity of the Nijmegen questionnaire were determined relative to the positivity of a HVT. The Nijmegen questionnaire threshold was ≥23. RESULTS: Data from 112 asthmatic children, median age 13.9 years [11.6-16], were analyzed. Twenty-eight children (25%) had mild or moderate asthma and 84 (75%) severe asthma. The HVT was performed on 108 children and was negative for 34 (31.5%) and positive for 74 (68.5%). The number of asthma exacerbations in the past 12 months, Asthma Control Test (ACT) score, and lung function did not differ between children with a positive HVT and a negative HVT. The Nijmegen questionnaire was administered to 103 children. Its sensitivity was 56.3% and specificity 56.3%. CONCLUSION: The symptoms and lung function of adolescents with asthma are not affected by the presence of HVS. The sensitivity and specificity of the Nijmegen questionnaire are low.

Feasibility of a nasal breathing training during pulmonary rehabilitation. A pilot randomized controlled study.

Hyperventilation syndrome (HVS) is a common source of dyspnea and disability. While pulmonary rehabilitation (PR) including breathing exercises is indicated, randomized controlled trial are warranted to recommend one type of breathing exercise than another. We aimed to compare during PR, the effect of 5 sessions of nasal ventilation exercise (NV+PR) versus voluntary hypoventilation (vHV+PR) on exercise dyspnea (primary outcome) and capacity and health-related quality of life in patients. In this open label randomized controlled trial, 19 HVS patients (age=48.3 ± 15.2 y.o, female/male=18/1, Nijmegen score=33 ± 7.7) were randomized in a NV+PR (n = 9) or vHV+PR (n = 10) group. Modified Medical Research Council (mMRC) dyspnea, 6-minute walking distance (6MWD) with nasal/oral ventilation were assessed before and after 3 months of PR, and questionnaires (Nijmegen, VQ-11). There was a significant effect of PR of but no significant difference between groups in the improvements of dyspnea@max exercise (time effect (T): p < 0.01; group (G): p = 0.63; group*time interaction (G*T): p = 0.49), mMRC dyspnea (T: p < 0.01; G: p = 0.45; G*T: p = 0.62), 6MWD (T: p < 0.05; G: p = 0.36; G*T: p = 0.31), VQ-11 (T: p < 0.001; G: p = 0.16; G*T: p = 0.09) and plasma HCO3- (T: p < 0.05; G: p = 0.93; G*T; p = 0.36), Yet, Nijmegen score (T: p < 0.01; G: p = 0.32; G*T: p < 0.05) improvement was larger in NV+PR group. The exercise oronasal breathing shift during the 6MWT was significantly delayed in all patients (T: p < 0.05; G: p = 0.30; G*T: p = 0.32) and positively correlated with plasma HCO3-(r = 0.42; p < 0.05). Nasal exercise was not superior versus voluntary hypoventilation during PR in HVS patients. Yet, nasal exercise appeared feasible, leading to acquisition of a nasal breathing pattern during walking, improvement of PR outcomes and ventilatory alkalosis. The link between nasal breathing and hyperventilation is discussed in the light of the nasal ventilation rhythm in the limbic system and its role on the limbic emotional and ventilatory functions.

Paroxysmal dyspnoea in asthma: Wheeze, ILO or dysfunctional breathing?

Paroxysms of dyspnoea in the general population are commonly reported and are frequently assumed to be asthma-related, especially if this diagnostic label has been previously applied. Often, this is not the case. Inducible Laryngeal Obstruction (ILO) and Dysfunctional Breathing (DB) are common comorbid conditions that go unrecognised in many difficult-to-treat asthmatics. On average, these patients have a delay in diagnosis of almost 5 years. This delay, along with ineffective, inappropriate escalation of asthma therapy, frequent hospital presentations for uncontrolled symptoms, and even intensive care admissions, magnifies patient morbidity and poor quality of life. ILO and DB have similar presentations and triggers to asthma. Differentiating between them can be challenging, especially in centres that do not have access to multidisciplinary subspecialty asthma services. Objectively confirming the diagnosis can likewise be challenging as symptoms fluctuate, and gold-standard investigations require extensive experience. This mini-review will summarise the clinical features of ILO and DB, with particular focus in the context of individuals treated for asthma. This narrative review will define each condition, highlight poignant aspects of the history and describe elements of the diagnostic pathway to gain objective confirmation.

The Thai version of the Nijmegen questionnaire.

Purpose: The Nijmegen questionnaire is a screening tool for detecting hyperventilation syndrome. The present study aimed to cross-culturally adapt the questionnaire to Thai language and test its psychometric properties for screening hyperventilation syndrome, in which the prevalence is increasing due to the impacts of the COVID-19 pandemic.Design/methodology/approach: The Thai version of the Nijmegen questionnaire (NQ-TH) was generated following a cross-cultural adaptation guideline including initial translation, synthesis of forward translation, back translation, expert committee review, and prefinal testing. Fifty control participants and one-hundred patients with symptoms related to hyperventilation syndrome were enrolled in this study for the determination of psychometric properties. Content validity, construct validity, internal consistency reliability, and test-retest reliability of the NQ-TH were assessed. Its discriminant ability and cutoff point for screening hyperventilation syndrome were also revealed. Findings: The obtained IOC and disappeared floor and ceiling effects indicated excellent content validity of the questionnaire. There were significant correlations between the total scores of the NQ-TH and other questionnaires and recorded respiratory measurements obtained from the patients, i.e., SF-36-TH (r = -0.257), HADS-TH (r = 0.331), RR (r = 0.377), and BHT (r = -0.444). This supported the construct validity of the NQ-TH. An acceptable internal consistency was also observed (Cronbach's alpha = 0.789). Test-retest repeatability of the questionnaire was high (ICC = 0.90). Moreover, the NQ-TH reliability was also ensured by calculated MDC (2.68). The cutoff point of the NQ-TH was at 20 with 98% sensitivity and 94% specificity.Originality/value: The NQ-TH established by the present study is a valid and reliable tool for screening hyperventilation syndrome among Thais.

Validation Criteria for PETCO2 Kinetics during the Hyperventilation Provocation Test in the Diagnosis of Idiopathic Hyperventilation Syndrome.

Background: The hyperventilation provocation test (HPTest) is a diagnostic tool for idiopathic hyperventilation syndrome (HVS), encountered in some long-COVID patients. However, interpretation of the HPTest remains unclear regarding the relevant PETCO2 values to focus on and whether subjective symptoms should be considered. This study aimed to re-evaluate objective HPTest results for diagnosing HVS by determining accurate PETCO2 kinetics in two groups of patients previously screened via the Nijmegen questionnaire (NQ). Methods: The kinetics of PETCO2 during the HPTest were mathematically modeled and compared between 37 HVS patients (NQ ≥23/64) and 37 healthy controls (NQ <23/64) matched for gender, age, and body dimensions. AUC values with sensitivity and specificity were calculated, and analysis was monitored in a validation cohort of 152 routine HPTests. Results: A threshold value of a less than 12.8 mmHg increment of PETCO2 at the 5th minute of the recovery phase of the HPTest diagnosed HVS patients with excellent sensitivity (0.92) and specificity (0.84). These results were confirmed in the validation cohort, highlighting the presence of 24% false positives/negatives when diagnosing on the basis of complaints in the NQ. Conclusions: For HVS diagnosis, we suggest considering the HPTest, which can more reliably reflect the mechanisms of CO2 homeostasis and the response of the respiratory center to a stimulus, regardless of the subjective onset of symptoms.

Diagnostic tests and subtypes of dysfunctional breathing in children with unexplained exertional dyspnea.

BACKGROUND: Inappropriate hyperventilation during exercise may be a specific subtype of dysfunctional breathing (DB). OBJECTIVE: To assess whether Nijmegen questionnaire and hyperventilation provocation test (HVPT) are able to differentiate inappropriate hyperventilation from other DB subtypes in children with unexplained exertional dyspnea, and normal spirometry and echocardiography. METHODS: The results were compared between a subgroup of 25 children with inappropriate hyperventilation (increased V'E/V'CO2 slope during a cardiopulmonary exercise test (CPET)) and an age and sex matched subgroup of 25 children with DB without hyperventilation (median age, 13.5 years; 36 girls). Anxiety was evaluated using State-Trait Anxiety Inventory for Children questionnaire. RESULTS: All children were normocapnic (at rest and peak exercise) and the children with hyperventilation had lower tidal volume/vital capacity on peak exercise (shallow breathing). The Nijmegen score correlated positively with dyspnea during the CPET and the HVPT (p = 0.001 and 0.010, respectively) and with anxiety score (p = 0.022). The proportion of children with a positive Nijmegen score (≥19) did not differ between hyperventilation (13/25) and no hyperventilation (14/25) groups (p = 0.777). Fractional end-tidal CO2 (FETCO2 ) at 5-min recovery of the HVPT was < 90% baseline in all children (25/25) of both subgroups. Likewise, there was no significant difference between the two subgroups for other indices of HVPT (FETCO2 at 3-min recovery and symptoms during the test). CONCLUSION: The validity of the Nijmegen questionnaire and the HVPT to discriminate specific subtypes of dysfunctional breathing, as well as the relevance of the inappropriate hyperventilation subtype itself may both be questioned.

The impact of mental toughness and postural abnormalities on dysfunctional breathing in athletes.

Background: While asthma and exercise-induced bronchoconstriction (EIB) can explain some cases of exertional dyspnea, the differential diagnosis of dyspnea is extensive. Dysfunctional breathing (DB) is a condition that is often overlooked and underdiagnosed. Pharmacologic treatments are available and widely utilized by clinicians for exertional dyspnea, but a better understanding of the non-pharmacologic treatments as well as psychological factors that play a role in DB can provide professional, elite amateurs, and recreational athletes with more therapeutic options.Measurement tools for mental toughness: Given the psychological components involved with these conditions, a tool to measure domains of sports mental toughness in athletes could help medical providers create a more comprehensive athlete profile which can be used in conjunction with standard pharmacologic therapy to provide a more effective treatment plan.Diagnosing DB: While normal breathing mechanics help shape appropriate posture and spinal stabilization, DB has been shown to contribute to pain and motor control deficits resulting in dysfunctional movement patterns, which further contribute to DB. Most respiratory specialists are unaware of how to assess the role of faulty sports technique, especially running gait, in dysfunctional breathing patterns making it difficult to recommend appropriate treatment and offer referrals for relevant therapies.Assessing postural changes: Three key components of proper running gait are reviewed and described in detail including trunk counter-rotation, extension of atlanto-occipital joint in conjunction with a forward tilted trunk, and ankle and hip joint range of motion.Conclusions: When underlying gait abnormalities and mental skills are addressed properly, they can disrupt poor breathing mechanics, facilitating a transition away from DB and toward healthier breathing patterns.KEY POINTS In summary, the following points should be considered when evaluating athletes who are having difficulty breathing even when compliant with their medications or if there is not an indication of asthma or EIB:Assess dysfunctional breathing (DB) with Nijmegen questionnaire (NQ).If DB is present, measure mental skills using the Sisu Quiz to determine an athlete's mental skills profile.Evaluate postural changes that may impact an athlete's ability to breathe.Using the three tools of the NQ, Sisu Quiz, and Postural assessments creates an athlete profile that is clinically useful to improve breathing technique.DB is often mistaken for other conditions for which medications are prescribed. By identifying DB early and making appropriate changes may negate or reduce the need for pharmacotherapy.Improving DB will improve athletic performance.

Progress of hyperventilation syndrome in children / 国际儿科学杂志

Hyperventilation syndrome(HVS)in children is a common functional respiratory disorder with a group of symptoms mainly characterized by hyperventilation, which is usually triggered by anxiety or stress events.A standardized questionnaire and the hyperventilation provocation test are helpful for diagnosis.Currently, the Nijmegen questionnaire is a common clinical tool to quantify and assess the severity of the symptoms.Emotional and psychological factors are major causes of HVS onset, meanwhile, abnormal breathing patterns are also implicated.Reassurance therapy and breathing retraining can improve the symptoms.

Respiratory rehabilitation for Covid-19 related persistent dyspnoea: A one-year experience.

BACKGROUND: Growing consideration is emerging regarding the burden of persisting sequelae after SARS-CoV-2 infection. Out-patients exhibiting long Covid may benefit from ambulatory rehabilitation which is, to date, poorly documented. METHODS: A longitudinal follow-up over a one-year period was conducted in two ambulatory rehabilitation structures in order to describe the characteristics of real-life patients referred with Covid-19 sequelae and their evolution over the course of rehabilitation. RESULTS: 39 consecutive patients were included from April 1st, 2020 to April 1st, 2021. Patients were middle-aged (48 ± 15yr), without comorbidities, and mostly mild to moderate SARS-CoV-2 infection (25(64%) not requiring hospitalisation). Rehabilitation referral was considered with a median delay of 73[34-178] days after disease onset. Most prevalent symptoms were dyspnoea (n = 35(90%)) and fatigue (n = 30(77%)). Hyperventilation syndrome was highly frequent (n = 12(34%)). 29(74%) patients presented with prolonged functional sequelae, which was associated with younger age (43 ± 14 vs. 50 ± 10yr; p = 0.002), greater prevalence of hyperventilation syndrome (n = 12(41%) vs. 0(0%); p = 0.255) and poorer quality of life (VQ-11; 31 ± 10 vs. 23 ± 9; p = 0.030). Over the course of rehabilitation, exertional dyspnoea, 6-min walking distance, 3-min sit-to-stand test, hyperventilation syndrome prevalence and quality of life significantly improved. CONCLUSION: Hyperventilation is frequent in long Covid and may explain persistent dyspnoea as well as altered quality of life. Our data support screening of hyperventilation syndrome and functional impairment in mild Covid-19 out-patients as both of these components may improve with ambulatory rehabilitation.

[The psychological burden of asthma]. / Le fardeau psychologique de l'asthme.

The experience of living with asthma varies between patients. In some cases, the psychological experience can take a central place and determine the course of asthma. Asthmatic disease can be complicated by adaption disorders that hamper the treatment, or genuine anxiety and depressive disorders that require the intervention of mental health specialists. Even more, the psychological experience can influence the intensity and frequency of the physical symptoms themselves, for example when asthma is associated with a hyperventilation syndrome worsening the functional impact and complicating the treatment. In this article, we underline the significance of the psychological experience through several clinical vignettes of patients suffering from asthma. In particular, we discuss the role of denial, or conversely identification with the status of being a patient, and the importance of the emotional experience associated with the symptoms of asthma. We highlight the relevance of therapeutic education programs as well as cognitive-behavioral therapies and psycho-corporal techniques, such as relaxation, for the psychological care of asthmatic disease. Finally, we detail how to better recognize a hyperventilation syndrome associated with asthma, how it can be approached with the patient and the treatment options. Through these examples, we illustrate the relevance of a comprehensive approach that integrates the psychological experience into the care of asthmatic disease.

Psycho-demographic profile in severe asthma and effect of emotional mood disorders and hyperventilation syndrome on quality of life.

BACKGROUND: Severe asthma affects a small population but carries a high psychopathological risk. Therefore, the psychodemographic profile of these patients is of interest. A substantial prevalence of anxiety, depression, alexithymia and hyperventilation syndrome in severe asthma is known, but contradictory results have been observed. These factors can also affect patients' quality of life. For this reasons, our purpose is to evaluate the psychodemographic profile of patients with severe asthma and assess the prevalence of anxiety, depression, alexithymia and hyperventilation syndrome and their impact on the quality of life of patients with severe asthma. METHODS: A cross-sectional study of 63 patients with severe asthma. Their psychodemographic profile was evaluated using the Hospital Anxiety and Depression Scale (HADS), Toronto Alexithymia Scale (TAS-20), Nijmegen questionnaire and Asthma Control Test (ACT) to determine the state of anxiety and depression, alexithymia, hyperventilation syndrome and control of asthma, respectively. Quality of life was assessed with the Mini Asthma Quality of Life Questionnaire (Mini-AQLQ). RESULTS: The mean age was 60 ± 13.6 years. Personal psychopathological histories were found in 65.1% of participants, and 8% reported previous suicidal attempts. The rate of anxiety and/or depression (HADS ≥ 11) was 68.3%. These patients present higher scores on the TAS-20 (p < 0.001) for the level of dyspnea (p = 0.021), and for emotional function (p = 0.017) on the Mini-AQLQ, compared with patients without anxiety or depression. Alexithymia (TAS-20 ≥ 61) was observed in 42.9% of patients; these patients were older (p = 0.037) and had a higher HADS score (p = 0.019) than patients with asthma without alexithymia. On the other hand, patients with hyperventilation syndrome (Nijmegen ≥ 23) scored higher on the HADS (p < 0.05), on the Mini-AQLQ (p = 0.002) and on the TAS-20 (p = 0.044) than the group without hyperventilation syndrome. Quality of life was related to anxiety-depression symptomatology (r = - 0.302; p = 0.016) and alexithymia (r = - 0.264; p = 0.036). Finally, the Mini-AQLQ total score was associated with the Nijmegen questionnaire total score (r = - 0.317; p = 0.011), and the activity limitation domain of the Mini-AQLQ correlated with the ACT total score (r = 0.288; p = 0.022). CONCLUSIONS: The rate of anxiety, depression, alexithymia and hyperventilation syndrome is high in patients with severe asthma. Each of these factors is associated with a poor quality of life.

Cardiopulmonary Exercise Testing in the Assessment of Dysfunctional Breathing.

Dysfunctional breathing (DB) is a disabling condition which affects the biomechanical breathing pattern and is challenging to diagnose. It affects individuals in many circumstances, including those without underlying disease who may even be athletic in nature. DB can also aggravate the symptoms of those with established heart or lung conditions. However, it is treatable and individuals have much to gain if it is recognized appropriately. Here we consider the role of cardiopulmonary exercise testing (CPET) in the identification and management of DB. Specifically, we have described the diagnostic criteria and presenting symptoms. We explored the physiology and pathophysiology of DB and physiological consequences in the context of exercise. We have provided examples of its interplay with co-morbidity in other chronic diseases such as asthma, pulmonary hypertension and left heart disease. We have discussed the problems with the current methods of diagnosis and proposed how CPET could improve this. We have provided guidance on how CPET can be used for diagnosis, including consideration of pattern recognition and use of specific data panels. We have considered categorization, e.g., predominant breathing pattern disorder or acute or chronic hyperventilation. We have explored the distinction from gas exchange or ventilation/perfusion abnormalities and described other potential pitfalls, such as false positives and periodic breathing. We have also illustrated an example of a clinical pathway utilizing CPET in the diagnosis and treatment of individuals with suspected DB.

Hyperventilation: A Possible Explanation for Long-Lasting Exercise Intolerance in Mild COVID-19 Survivors?

Since the outbreak of the coronavirus (COVID-19) pandemic, most attention has focused on containing transmission and addressing the surge of critically ill patients in acute care settings. As we enter the second phase of the pandemic, emphasis must evolve to post-acute care of COVID-19 survivors. Persisting cardiorespiratory symptoms have been reported at several months after the onset of the infection. Information is lacking on the pathophysiology of exercise intolerance after COVID-19. Previous outbreaks of coronaviruses have been associated with persistent dyspnea, muscle weakness, fatigue and reduced quality of life. The extent of Covid-19 sequelae remains to be evaluated, but persisting cardiorespiratory symptoms in COVID-19 survivors can be described as two distinct entities. The first type of post-Covid symptoms are directly related to organ injury in the acute phase, or the complications of treatment. The second type of persisting symptoms can affect patients even with mild initial disease presentation without evidence of organ damage. The mechanisms are still poorly qualified to date. There is a lack of correlation between initial symptom severity and residual symptoms at exertion. We report exercise hyperventilation as a major limiting factor in COVID-19 survivors. The origin of this hyperventilation may be related to an abnormality of ventilatory control, by either hyperactivity of activator systems (automatic and cortical ventilatory control, peripheral afferents, and sensory cortex) or failure of inhibitory systems (endorphins) in the aftermath of pulmonary infection. Hyperventilation-induced hypocapnia can cause a multitude of extremely disabling symptoms such as dyspnea, tachycardia, chest pain, fatigue, dizziness and syncope at exertion.

Unilateral recurrent laryngeal nerve palsy post-thyroidectomy: Looking for hyperventilation syndrome.

AIMS: Unilateral Recurrent Laryngeal Nerve (RLN) palsy is responsible for dysphonia and difficulties in swallowing. The role of unilateral RLN palsy on dyspnea is not fully elucidated. Our hypothesis is that air leak could be responsible for development of hyperventilation syndrome (HVS). OBJECTIVE: The objective of this study was to determine in patients with unilateral RLN palsy if dyspnea could be associated with HVS. MATERIAL AND METHODS: Over a 12-month period, all patients with permanent unilateral RLN palsy after thyroidectomy complaining from the onset of unexplained dyspnea were tested. Measurement of Nijmegen score, an hyperventilation test, an arterial blood gas, lung function and cardiac tests were performed. The diagnosis of HVS was defined if at least two criteria were present among: Nijmegen score>23; reproduction of at least 2 usual symptoms during hyperventilation test; an expirated pressure of CO2 (EpCO2)<30mmHg or<90% of the initial EpCO2 after a 5minutes recovery period following a 3minutes voluntary hyperventilation. RESULTS: Ten out of 366 patients with thyroidectomy for benign disease had permanent unilateral RLN palsy and dyspnea. Among 10 patients included, 8 were diagnosed having HVS on the hyperventilation test without cardiac/lung dysfunction. CONCLUSION: In summary, this study is a proof of concept that HVS might be involved in dyspnea associated with unilateral RLN palsy.

Why Physiology Is Critical to the Practice of Medicine: A 40-year Personal Perspective.

Accuracy in diagnosis trumps all other elements in clinical decision making. If diagnosis is inaccurate, management is likely to prove futile if not dangerous. Knowledge of physiology provides a periscope for identifying abnormalities beneath the skin responsible for clinical manifestations on the surface. Expert diagnosticians suspect disorders based on pattern recognition and automatic retrieval of knowledge stored in memory. A superior diagnostician looks at the same findings other clinicians see but thinks of causes that others have not imagined. Solving clinical mysteries depends on a clinician's power of imagination, not the capacity to recite an algorithm or apply a protocol.

Prevalence and extent of right-to-left shunt on contrast-enhanced transcranial Doppler in patients with chronic hyperventilation syndrome: results of a case-control study.

AIM: Chronic hyperventilation syndrome (CHVS) represents a frequent but poorly understood breathing pattern disorder. In a previous small pilot study, we reported a higher prevalence of right-to-left shunt (RLS) in CHVS patients than in healthy subjects. The aim of this study was to confirm those previous results from this larger and matched case-control study, and to evaluate the prevalence and grade of RLS in patients with CHVS in whom organic and psychiatric causes were excluded. CLINICAL RATIONALE FOR THE STUDY: Determining other types of CHVS triggers not related to organic or psychiatric causes which could be clinically useful. MATERIAL AND METHODS: 100 subjects (mean age 34 ± 6 years; 80% females), including 50 patients with CHVS and 50 age- and sex-matched healthy controls (CG), were prospectively recruited into this single-centre study. Vascular RLS was diagnosed using contrast-enhanced transcranial Doppler (c-TCD). RESULTS: RLS prevalence significantly increased in the CHVS group (n = 23) compared to the CG group (n = 8) (46% vs 16%; p < 0.01). Patients with CHVS and RLS tended to have more frequent permanent shunts compared to the CG (60% vs 25%; p = 0.08), but there was no difference regarding RLS grading between the groups. CONCLUSIONS AND CLINICAL IMPLICATIONS: This study confirmed our previous findings in which the prevalence of RLS in patients with CHVS was significantly higher than in an age- and sex-matched healthy control group. However, we could not confirm the results of our prior study, where RLS was larger in CHVS than in CG. The tentative association between RLS and CHVS needs to be further examined.