Postural orthostatic tachycardia syndrome: A respiratory disorder?

Postural orthostatic tachycardia syndrome (POTS) is a disorder epitomized by the story of the blind men and the elephant. Patients may see primary care internists or pediatricians due to fatigue, be referred to neurologists for "spells", to cardiologists for evaluation of pre-syncope or chest pain, to gastroenterologists for nausea or dyspepsia, and even pulmonologists for dyspnea. Adoption of a more systematic approach to their evaluation and better characterization of patients has led to greater understanding of comorbidities, hypotheses prompting mechanistic investigations, and pharmacologic trials. Recent work has implicated disordered sympathetic nervous system activation in response to central (thoracic) hypovolemia. It is this pathway that leads one zero in on a putative focal point from which many of the clinical manifestations can be explained - specifically the carotid body. Despite heterogeneity in etiopathogenesis of a POTS phenotype, we propose that aberrant activation and response of the carotid body represents one potential common pathway in evolution. To understand this postulate, one must jettison isolationist or reductionist ideas of chemoreceptor and baroreceptor functions of the carotid body or sinus, respectively, and consider their interaction and interdependence both locally and centrally where some of its efferents merge. Doing so enables one to connect the dots and appreciate origins of diverse manifestations of POTS, including dyspnea for which the concept of neuro-mechanical uncoupling is wanting, thereby expanding our construct of this symptom. This perspective expounds our premise that POTS has a prominent respiratory component.

Expert's Choice: 2018's Most Exciting Research in the Field of Pediatric Exercise Science.

This commentary highlights 23 noteworthy publications from 2018, selected by leading scientists in pediatric exercise science. These publications have been deemed as significant or exciting in the field as they (a) reveal a new mechanism, (b) highlight a new measurement tool, (c) discuss a new concept or interpretation/application of an existing concept, or (d) describe a new therapeutic approach or clinical tool in youth. In some cases, findings in adults are highlighted, as they may have important implications in youth. The selected publications span the field of pediatric exercise science, specifically focusing on: aerobic exercise and training; neuromuscular physiology, exercise, and training; endocrinology and exercise; resistance training; physical activity and bone strength; growth, maturation, and exercise; physical activity and cognition; childhood obesity, physical activity, and exercise; pulmonary physiology or diseases, exercise, and training; immunology and exercise; cardiovascular physiology and disease; and physical activity, inactivity, and health.

Ventilatory Limitation of Exercise in Pediatric Subjects Evaluated for Exertional Dyspnea.

Purpose: Attribution of ventilatory limitation to exercise when the ratio of ventilation ( V ˙ E ) at peak work to maximum voluntary ventilation (MVV) exceeds 0.80 is problematic in pediatrics. Instead, expiratory flow limitation (EFL) measured by tidal flow-volume loop (FVL) analysis - the method of choice - was compared with directly measured MVV or proxies to determine ventilatory limitation. Methods: Subjects undergoing clinical evaluation for exertional dyspnea performed maximal exercise testing with measurement of tidal FVL. EFL was defined when exercise tidal FVL overlapped at least 5% of the maximal expiratory flow-volume envelope for > 5 breaths in any stage of exercise. We compared this method of ventilatory limitation to traditional methods based on MVV or multiples (30, 35, or 40) of FEV1. Receiver operating characteristic curves were constructed and area under curve (AUC) computed for peak V ˙ E /MVV and peak V ˙ E /x⋅FEV1. Results: Among 148 subjects aged 7-18 years (60% female), EFL was found in 87 (59%). Using EFL shown by FVL analysis as a true positive to determine ventilatory limitation, AUC for peak V ˙ E /30⋅FEV1 was 0.84 (95% CI 0.78-0.90), significantly better than AUC 0.70 (95% CI 0.61-0.79) when 12-s sprint MVV was used for peak V ˙ E /MVV. Sensitivity and specificity were 0.82 and 0.70 respectively when using a cutoff of 0.85 for peak V ˙ E /30⋅FEV1 to predict ventilatory limitation to exercise. Conclusion: Peak V ˙ E /30⋅FEV1 is superior to peak V ˙ E /MVV, as a means to identify potential ventilatory limitation in pediatric subjects when FVL analysis is not available.

Exertional Dyspnea in Childhood: Is There an Iceberg Beneath the Apex?

This essay expounds on fundamental, quantitative elements of the exercise ventilation in children, which was the subject of the Tom Rowland Lecture given at the NASPEM 2018 Conference. Our knowledge about how much ventilation rises during aerobic exercise is reasonably solid; our understanding of its governance is a work in progress, but our grasp of dyspnea and ventilatory limitation in children (if it occurs) remains embryonic. This manuscript summarizes ventilatory mechanics during dynamic exercise, then proceeds to outline our current understanding of mechanisms of dyspnea, particularly during exercise (exertional dyspnea). Most research in this field has been done in adults, and the vast majority of these studies in patients with chronic obstructive pulmonary disease. To what extent conclusions drawn from this literature apply to children and adolescents-both healthy and those with cardiopulmonary disease-will be discussed. The few, recent, pertinent, pediatric studies will be reviewed in an attempt to provide an empirical basis for proposing a hypothetical model to study exertional dyspnea in youth. Just as somatic growth will have consequences for ventilatory and exercise capacity, so too will neural developmental plasticity and experience affect perception of dyspnea. Our path to understand how these evolving inputs and influences summate during a child's life will be Columbus' India.

Observational study of laryngoscopy plus flow-volume loops during exercise.

Laryngoscopy is the gold standard to diagnose exercise-induced laryngeal obstruction, though inspiratory flow-volume loop may provide a clue. We combined tidal flow-volume loop analysis plus laryngoscopy during exercise and found that cigar-shaped - not flattened - inspiratory loops are associated with obstruction. Pursed-lip breathing slows inhalation thereby reducing vocal fold adduction.

Flow limitation and dysanapsis in children and adolescents with exertional dyspnea.

The consequence of dysanapsis, quantitated by dysanapsis ratio (DR), on expiratory flow limitation (EFL) during exercise in pediatric subjects was examined. EFL occurred in 80 (56%) subjects from an enriched sample of children and adolescents tested during investigation of exertional dyspnea. DR was lower in subjects with vs without EFL during exercise: (0.055 ±â€¯0.015 vs 0.067 ±â€¯0.017, p < 0.001), and lower ratio correlated with greater extent of EFL (r = -0.64, p < 0.001). EFL was seen more often in boys: 67% vs 46% (p = 0.01), as girls had higher DR (0.063 ±â€¯0.016 vs 0.056 ±â€¯0.018, p = 0.007). Lower FEV1 (95 ±â€¯17 vs 102 ±â€¯15%predicted, p < 0.005) and FEF50 (3.47 ±â€¯1.28 vs 4.08 ±â€¯1.20 L s-1, p = 0.002) distinguished those with vs without EFL. Inspiratory capacity rose (IC) steadily, as work increased among those with EFL, whereas it fell to back resting levels after an initial rise in subjects without EFL. Low DR predicts EFL in pediatric subjects. Adjusting operating lung volume during exercise can mitigate EFL but this strategy may contribute to exertional dyspnea.

Pediatric Disorders of Orthostatic Intolerance.

Orthostatic intolerance (OI), having difficulty tolerating an upright posture because of symptoms or signs that abate when returned to supine, is common in pediatrics. For example, ∼40% of people faint during their lives, half of whom faint during adolescence, and the peak age for first faint is 15 years. Because of this, we describe the most common forms of OI in pediatrics and distinguish between chronic and acute OI. These common forms of OI include initial orthostatic hypotension (which is a frequently seen benign condition in youngsters), true orthostatic hypotension (both neurogenic and nonneurogenic), vasovagal syncope, and postural tachycardia syndrome. We also describe the influences of chronic bed rest and rapid weight loss as aggravating factors and causes of OI. Presenting signs and symptoms are discussed as well as patient evaluation and testing modalities. Putative causes of OI, such as gravitational and exercise deconditioning, immune-mediated disease, mast cell activation, and central hypovolemia, are described as well as frequent comorbidities, such as joint hypermobility, anxiety, and gastrointestinal issues. The medical management of OI is considered, which includes both nonpharmacologic and pharmacologic approaches. Finally, we discuss the prognosis and long-term implications of OI and indicate future directions for research and patient management.

The Diagnostic Accuracy of Fractional Exhaled Nitric Oxide Testing in Asthma: A Systematic Review and Meta-analyses.

OBJECTIVE: To evaluate the diagnostic accuracy of fractional exhaled nitric oxide (FeNO) measurement in individuals with suspected asthma. METHODS: We searched MEDLINE, EMBASE, PsycINFO, Cochrane databases, and SciVerse Scopus from the databases' inception through April 4, 2017, for studies that enrolled patients aged 5 years and older with suspected asthma and evaluated FeNO diagnostic accuracy. Independent reviewers selected studies and extracted data. We used the symmetric hierarchical summary receiver operating characteristic models to estimate test performance. RESULTS: We included 43 studies with a total of 13,747 patients. In adults, using FeNO cutoffs of less than 20, 20 to 29, 30 to 39, and 40 or more parts per billion, FeNO testing had sensitivities of 0.80, 0.69, 0.53, and 0.41, respectively, and specificities of 0.64, 0.78, 0.85, and 0.93, respectively. In children, using FeNO cutoffs of less than 20 and 20 to 29 parts per billion, FeNO testing had sensitivities of 0.78 and 0.61, respectively, and specificities of 0.79 and 0.89, respectively. Depending on the FeNO cutoff, the posttest odds of having asthma with a positive FeNO test result increased by 2.80- to 7.00-fold. Diagnostic accuracy was modestly better in corticosteroid-naive asthmatics, children, and nonsmokers than in the overall population. CONCLUSION: Fractional exhaled nitric oxide measurement has moderate accuracy to diagnose asthma in individuals aged 5 years and older. Test performance may be modestly better in corticosteroid-naive asthmatics, children, and nonsmokers than in the general population with suspected asthma. TRIAL REGISTRATION: International Prospective Register of Systematic Reviews (PROSPERO) Identifier: CRD42016047887.

Aerobic fitness in adolescents with chronic pain or chronic fatigue: parallels and mechanisms?

OBJECTIVE: Chronic fatigue and chronic pain both deter people from participating in exercise, even though exercise is often a key component of treatment. While reasons for this may seem obvious, the extent and mechanism(s) of reduced exercise performance among affected individuals, particularly those with chronic pain, are not well described. We hypothesized that patients with chronic fatigue are more deconditioned than those with chronic pain, due to the nature of their illness or disability. DESIGN: Retrospective chart audit June 2012 to December 2014. SUBJECTS: Adolescents with chronic fatigue (320, 73 males) or chronic pain (158, 30 males). METHODS: Maximal cardiopulmonary exercise test to determine peak oxygen uptake (V̇O2) and work efficiency. RESULTS: Mean (standard deviation (SD)) peakV̇O2 was similar between patients with chronic fatigue and chronic pain: males 36.5 (SD 8.3) vs 34.2 (SD 7.3) ml/kg/min (p = 0.17); females 27.3 (SD 6.1) vs 27.6 (SD 6.6) ml/kg/min (p = 0.67). PeakV̇O2 was < 90% predicted in 80% and 75% of females, or 77% and 83% of males, with chronic fatigue and chronic pain, respectively. Peak O2pulse and work efficiency were likewise similar. CONCLUSION: Patients in both groups manifest exercise responses typical of cardiopulmonary deconditioning and to similar extent. Failure to detect unique cardiopulmonary or muscle pathophysiology suggests a shared pathway to low aerobic work capacity.

Pediatric Exercise Testing: Value and Implications of Peak Oxygen Uptake.

Peak oxygen uptake (peak V ˙ O 2 ) measured by clinical exercise testing is the benchmark for aerobic fitness. Aerobic fitness, estimated from maximal treadmill exercise, is a predictor of mortality in adults. Peak V ˙ O 2 was shown to predict longevity in patients aged 7-35 years with cystic fibrosis over 25 years ago. A surge of exercise studies in young adults with congenital heart disease over the past decade has revealed significant prognostic information. Three years ago, the first clinical trial in children with pulmonary arterial hypertension used peak V ˙ O 2 as an endpoint that likewise delivered clinically relevant data. Cardiopulmonary exercise testing provides clinicians with biomarkers and clinical outcomes, and researchers with novel insights into fundamental biological mechanisms reflecting an integrated physiological response hidden at rest. Momentum from these pioneering observations in multiple disease states should impel clinicians to employ similar methods in other patient populations; e.g., sickle cell disease. Advances in pediatric exercise science will elucidate new pathways that may identify novel biomarkers. Our initial aim of this essay is to highlight the clinical relevance of exercise testing to determine peak V ˙ O 2 , and thereby convince clinicians of its merit, stimulating future clinical investigators to broaden the application of exercise testing in pediatrics.

Cardiac responses to exercise distinguish postural orthostatic tachycardia syndrome variants.

We previously showed that one-third of adolescents with postural orthostatic tachycardia syndrome (POTS) have hyperkinetic circulation. In a subsequent cohort, we compare participants with POTS grouped according to cardiac output (Q˙) versus oxygen uptake (V˙O2) function, whose circulatory response to exercise lay at the lower end of this distribution. We hypothesized that such grouping determines the circulatory response to incremental-protocol, upright, cycle ergometry by whatever blend of flow and resistance adjustments best maintains normal blood pressure. We reviewed data on 209 POTS participants aged 10-19 years (73% female) grouped as follows: Q˙-V˙O2 < 3.20 L·min-1 per L·min-1 were designated low Q˙ or hypokinetic variant (N = 31); normal-Q˙ had slopes between 3.21 and 7.97; hyperkinetic participants had Q˙-V˙O2 slope >8 L·min-1 per L·min-1 (N = 32). Heart rate response to exercise was virtually identical in each group. Mean stroke volume (SV) rose normally in the hyperkinetic group (51 ± 38%); less in the normal Q˙ group (22 ± 27%); but was flat in the low Q˙ group (-7 ± 16%). Mean arterial pressure was similar at rest while systemic vascular conductance was flat from rest to exercise in the hypokinetic group, and by comparison rose more steeply in the normal Q˙ (P < 0.001) and in the hyperkinetic (P = 0.02) groups. In conclusion, we identified a variant of POTS with a hypokinetic circulation maintained by a vasoconstricted state. We speculate that they cannot muster preload to augment exercise SV due to profound thoracic hypovolemia, and must resort to vasoconstriction in order to maintain perfusion pressure within working muscle.

Cardiopulmonary exercise performance is reduced in congenital diaphragmatic hernia survivors.

BACKGROUND: Congenital diaphragmatic hernia (CDH) is associated with lung hypoplasia. CDH survivors may have pulmonary morbidity that can decrease cardiopulmonary exercise. We aimed to examine whether cardiopulmonary exercise testing (CPET) results differ in CDH survivors versus healthy age-matched controls and whether CPET results among CDH survivors differ according to self-reported daily activity. METHODS: In one medical center in Croatia, CDH survivors-patients with surgically corrected CDH who were alive at age 5 years-were invited to participate in spirometry and CPET. Values were compared with those of controls matched 2:1 by age and sex for each CDH survivor aged 7 years or older. RESULTS: Among 27 CDH survivors aged 5-20 years, 13 (48%) had continued symptoms or spirometric evidence of pulmonary disease. Compared with controls (n = 44), survivors (n = 22) had lower peak oxygen consumption (V˙O2 mean [SD], 35.7 [6.9] vs. 45.3 [8.2] ml/kg per min; P < 0.001). At peak exercise, V˙O2/heart rate (P < 0.001), tidal volume (P = 0.005), and minute ventilation (P < 0.001) were lower in survivors, but the maximal respiratory rate was not different (P = 0.72). Among survivors, mean (SD) V˙O2peak (ml/kg per min) differed by self-reported activity level: athletic, 40.3 (5.0); normal, 35.8 (6.5); and sedentary, 32.1 (6.8) (by ANOVA, P = 0.10 across three groups and P = 0.04 athletic vs. sedentary). CONCLUSION: More than half of CDH survivors continue to have chronic pulmonary disease. CDH survivors had lower aerobic exercise capacity than controls. Self-reporting information on daily activities may identify CDH patients with low V˙O2max who may benefit from physical training. Pediatr Pulmonol. 2016;51:1320-1329. © 2016 Wiley Periodicals, Inc.

Measuring Dyspnea and Perceived Exertion in Healthy Adults and with Respiratory Disease: New Pictorial Scales.

BACKGROUND: Dyspnea or perceived exertion during exercise is most commonly measured using Borg or visual analog scales, created for use in adults. In contrast, pictorial scales have been promoted for children due to skepticism concerning applicability of the said scales in pediatrics. We sought to validate our newly created, pictorial Dalhousie Dyspnea and Perceived Exertion Scales in adult populations and compare ratings with the Borg scale. METHODS: Dyspnea and perceived exertion ratings obtained with both modified Borg CR-10 and Dalhousie scales during maximal cycle exercise were compared in 24 healthy adults and 17 with various pulmonary disorders. Scale ratings for perceived exertion were plotted against work while ratings for dyspnea were plotted against ventilation using previously developed alternative models to simple power law. Goodness of fit was determined by lowest root-mean-square error or by corrected Akaike information criterion. RESULTS: Pictorial ratings of dyspnea and perceived exertion measured by both scale ratings rose as expected with increasing exercise intensity, and individual trajectories obtained by either scale were virtually superimposable in 90 % of subjects. In general, the lowest root-mean-square error or corrected Akaike information criterion was found with models which incorporated a time delay, defined as the fraction of maximum work or ventilation at which point a clear increase in ratings above resting level was reported. CONCLUSIONS: The Dalhousie Dyspnea and Exertion Scales offer an equally good alternative to the Borg scale for measuring dyspnea and perceived exertion in adults.

Asthma-associated comorbidities in children with and without secondhand smoke exposure.

BACKGROUND: Secondhand smoke (SHS) exposure is known to trigger asthma, but asthma disease severity and comorbidities in children exposed to SHS are not very well quantified. OBJECTIVE: To identify comorbidities and understand health care usage in children with asthma exposed to SHS (cases) compared with children with asthma but without SHS exposure (controls). METHODS: A retrospective nested matched case-and-control study was conducted with children 5 to 18 years old who were enrolled in the Pediatric Asthma Management Program. Pulmonary function testing (spirometry, methacholine challenges, and exhaled nitric oxide) and body mass index were reviewed. Influenza vaccination rates, oral steroid usage, emergency department visits, and hospitalizations were assessed. Network analysis of the 2 groups also was conducted to evaluate for any associations between the variables. RESULTS: Cases had significantly higher body mass index percentiles (>75%, odds ratio [OR] 1.64, 95% confidence interval [CI] 1.22-2.2, P = .001). Cases were less likely to have had a methacholine challenge (OR 0.49, 95% CI 0.36-0.68, P < .001) and an exhaled nitric oxide (OR 0.6, 95% CI 0.37-0.97, P = .04) performed than controls. The ratio of forced expiration volume in 1 second to forced vital capacity and forced expiration volume in 1 second were lower in cases than in controls (P < .05). Cases were less likely to have received an influenza vaccination (OR 0.61, 95% CI 0.45-0.82, P = .001) than controls. Unsupervised multivariable network analysis suggested a lack of discrete and unique subgroups between cases and controls. CONCLUSION: Children with asthma exposed to SHS are more likely to have comorbid conditions such as obesity, more severe asthma, and less health care usage than those not exposed to SHS. Smoking cessation interventions and addressing health disparities could be crucial in this vulnerable population.

Aspiration-related pulmonary syndromes.

Aspiration of foreign matter into the airways and lungs can cause a wide spectrum of pulmonary disorders with various presentations. The type of syndrome resulting from aspiration depends on the quantity and nature of the aspirated material, the chronicity, and the host responses. Aspiration is most likely to occur in subjects with a decreased level of consciousness, compromised airway defense mechanisms, dysphagia, gastroesophageal reflux, and recurrent vomiting. These aspiration-related syndromes can be categorized into airway disorders, including vocal cord dysfunction, large airway obstruction with a foreign body, bronchiectasis, bronchoconstriction, and diffuse aspiration bronchiolitis, or parenchymal disorders, including aspiration pneumonitis, aspiration pneumonia, and exogenous lipoid pneumonia. In idiopathic pulmonary fibrosis, aspiration has been implicated in disease progression and acute exacerbation. Aspiration may increase the risk of bronchiolitis obliterans syndrome in patients who have undergone a lung transplant. Accumulating evidence suggests that a causative role for aspiration is often unsuspected in patients presenting with aspiration-related pulmonary diseases; thus, many cases go undiagnosed. Herein, we discuss the broadening spectrum of these pulmonary syndromes with a focus on presenting features and diagnostic aspects.

Dalhousie Pictorial Scales Measuring Dyspnea and Perceived Exertion during Exercise for Children and Adolescents.

RATIONALE: Alternative scales to measure dyspnea and perceived exertion have been sought due to concerns regarding understanding and validity of any Borg scale in pediatric populations. OBJECTIVES: To demonstrate content validity of Dalhousie Dyspnea and Perceived Exertion Scales developed for children and adolescents. METHODS: We obtained ratings for dyspnea and perceived exertion using both Borg CR-10 and Dalhousie Scales during incremental cycle exercise in 100 children and adolescents, healthy or with respiratory disease. Content validity was determined by correlating perceived leg exertion rating versus heart rate or %peak work capacity and dyspnea rating versus ventilation expressed as %peak ventilation. The stimulus-perceptual response was modeled as a quadratic function with a delay term. Reproducibility, cross-modality usage, and language effects were assessed in a small group of Italian children during treadmill exercise. MEASUREMENTS AND MAIN RESULTS: Pictorial ratings of dyspnea and perceived exertion measured by both scale ratings rose as expected with increasing exercise intensity in children and adolescents, demonstrating excellent correlation between perceived leg exertion versus exercise intensity and dyspnea rating versus ventilation (median Spearman ρ ≥ 0.9) with either scale. There were no systematic differences in dyspnea or perceived exertion ratings between children with or without respiratory disease. Understandability and reproducibility of the Dalhousie scales was affirmed in Italian-speaking subjects performing treadmill exercise. CONCLUSIONS: Dalhousie Dyspnea and Perceived Exertion Scales offer an alternative to the Borg scale for use during exercise in pediatric subjects. Children and adolescents exhibit large variation in patterns of ratings of dyspnea and perceived exertion in incremental exercise.

The clinical translation gap in child health exercise research: a call for disruptive innovation.

In children, levels of play, physical activity, and fitness are key indicators of health and disease and closely tied to optimal growth and development. Cardiopulmonary exercise testing (CPET) provides clinicians with biomarkers of disease and effectiveness of therapy, and researchers with novel insights into fundamental biological mechanisms reflecting an integrated physiological response that is hidden when the child is at rest. Yet the growth of clinical trials utilizing CPET in pediatrics remains stunted despite the current emphasis on preventative medicine and the growing recognition that therapies used in children should be clinically tested in children. There exists a translational gap between basic discovery and clinical application in this essential component of child health. To address this gap, the NIH provided funding through the Clinical and Translational Science Award (CTSA) program to convene a panel of experts. This report summarizes our major findings and outlines next steps necessary to enhance child health exercise medicine translational research. We present specific plans to bolster data interoperability, improve child health CPET reference values, stimulate formal training in exercise medicine for child health care professionals, and outline innovative approaches through which exercise medicine can become more accessible and advance therapeutics across the broad spectrum of child health.

High flow variant postural orthostatic tachycardia syndrome amplifies the cardiac output response to exercise in adolescents.

Postural orthostatic tachycardia syndrome (POTS) is characterized by chronic fatigue and dizziness and affected individuals by definition have orthostatic intolerance and tachycardia. There is considerable overlap of symptoms in patients with POTS and chronic fatigue syndrome (CFS), prompting speculation that POTS is akin to a deconditioned state. We previously showed that adolescents with postural orthostatic tachycardia syndrome (POTS) have excessive heart rate (HR) during, and slower HR recovery after, exercise - hallmarks of deconditioning. We also noted exaggerated cardiac output during exercise which led us to hypothesize that tachycardia could be a manifestation of a high output state rather than a consequence of deconditioning. We audited records of adolescents presenting with long-standing history of any mix of fatigue, dizziness, nausea, who underwent both head-up tilt table test and maximal exercise testing with measurement of cardiac output at rest plus 2-3 levels of exercise, and determined the cardiac output () versus oxygen uptake () relationship. Subjects with chronic fatigue were diagnosed with POTS if their HR rose ≥40 beat·min(-1) with head-up tilt. Among 107 POTS patients the distribution of slopes for the , relationship was skewed toward higher slopes but showed two peaks with a split at ~7.0 L·min(-1) per L·min(-1), designated as normal (5.08 ± 1.17, N = 66) and hyperkinetic (8.99 ± 1.31, N = 41) subgroups. In contrast, cardiac output rose appropriately with in 141 patients with chronic fatigue but without POTS, exhibiting a normal distribution and an average slope of 6.10 ± 2.09 L·min(-1) per L·min(-1). Mean arterial blood pressure and pulse pressure from rest to exercise rose similarly in both groups. We conclude that 40% of POTS adolescents demonstrate a hyperkinetic circulation during exercise. We attribute this to failure of normal regional vasoconstriction during exercise, such that patients must increase flow through an inappropriately vasodilated systemic circulation to maintain perfusion pressure.

Adolescent fatigue, POTS, and recovery: a guide for clinicians.

Many teenagers who struggle with chronic fatigue have symptoms suggestive of autonomic dysfunction that may include lightheadedness, headaches, palpitations, nausea, and abdominal pain. Inadequate sleep habits and psychological conditions can contribute to fatigue, as can concurrent medical conditions. One type of autonomic dysfunction, postural orthostatic tachycardia syndrome, is increasingly being identified in adolescents with its constellation of fatigue, orthostatic intolerance, and excessive postural tachycardia (more than 40 beats/min). A family-based approach to care with support from a multidisciplinary team can diagnose, treat, educate, and encourage patients. Full recovery is possible with multi-faceted treatment. The daily treatment plan should consist of increased fluid and salt intake, aerobic exercise, and regular sleep and meal schedules; some medications can be helpful. Psychological support is critical and often includes biobehavioral strategies and cognitive-behavioral therapy to help with symptom management. More intensive recovery plans can be implemented when necessary.