REPRODUCIBILITY OF EUCAPNIC VOLUNTARY HYPERVENTILATION FOR EXERCISE-INDUCED BRONCHOSPASM DIAGNOSIS IN ASTHMATIC CHILDREN AND ADOLESCENTS.

BACKGROUND: Exercise-induced respiratory symptoms are frequently reported by asthmatics and exercise-induced bronchospasm (EIB) is a frequent cause that requires objective testing for diagnosis. Eucapnic voluntary hyperventilation (EVH) is recommended as an exercise surrogate stimulus for this purpose, but its short-term reproducibility is not yet established in young asthmatics. OBJECTIVE: To evaluate the short-term test-retest agreement and reproducibility of FEV1 changes after EVH in young asthmatics. METHODS: Asthmatics aged between 10 and 20 years underwent EVH for EIB diagnosis on two occasions 2-4 days apart at a specialized university clinic. FEV1 was measured 5, 15 and 30 minutes after EVH with a target ventilation rate 21 times baseline FEV1. EIB was diagnosed as a decrease >10% in FEV1 from baseline. RESULTS: Twenty-six of 62 recruited individuals tested positive for EIB on both visits (positive group) and 17 on one visit only (divergent group); and 19 tested negative on both visits (negative group). The overall agreement was 72.5% (95%CI 61.6%, 83.6%) and positive and negative agreement was 41.9% and 30.6% respectively. Despite overall low bias in FEV1 response between test days (0.87%), the limits of agreement were wide (+20.72%). There were no differences in pre-challenge FEV1 or achieved ventilation rate, between visits either between groups (p=0.097 and p=0.461) or within groups, (p=0.828 and p=0.780). No test was interrupted by symptoms and there were no safety issues. CONCLUSIONS: More than one EVH test should be performed in young asthmatics with a negative test to exclude EIB and minimize misdiagnosis and mistreatment.

Apnea central del sueño en pacientes con insuficiencia cardiaca: Efectos fisiológicos de la ventilación periódica

<b>Background:</b> The effects of hyperventilation and hyperventilation in the context of periodic breathing (PB) on sympatho-vagal balance (SVB) and hemodynamics in conditions of decreased cardiac output and feedback resetting, such as heart failure (HF) or pulmonary arterial hypertension (PAH), are not completely understood. Objectives: To investigate the effects of voluntary hyperventilation and simulated PB on hemodynamics and SVB in healthy subjects, in patients with systolic HF and reduced or mid-range ejection fraction (HFrEF and HFmrEF) and in patients with PAH. <b>Methods:</b> Study participants (n = 20 per group) underwent non-invasive recording of diastolic blood pressure, heart rate variability (HRV), baroreceptor-reflex sensitivity (BRS), total peripheral resistance index (TPRI) and cardiac index (CI). All measurements were performed at baseline, during voluntary hyperventilation and during simulated PB with different length of the hyperventilation phase. <b>Results:</b> In healthy subjects, voluntary hyperventilation led to a 50% decrease in the mean BRS slope and a 29% increase in CI compared to baseline values (<i>p</i> &#x3c; 0.01 and <i>p</i> &#x3c; 0.05). Simulated PB did not alter TPRI or CI and showed heterogeneous effects on BRS, but analysis of dPBV revealed decreased sympathetic drive in healthy volunteers depending on PB cycle length (<i>p</i> &#x3c; 0.05). In HF patients, hyperventilation did not affect BRS and TPRI but increased the CI by 10% (<i>p</i> &#x3c; 0.05). In HF patients, simulated PB left all of these parameters unaffected. In PAH patients, voluntary hyperventilation led to a 15% decrease in the high-frequency component of HRV (<i>p</i> &#x3c; 0.05) and a 5% increase in CI (<i>p</i> &#x3c; 0.05). Simulated PB exerted neutral effects on both SVB and hemodynamic parameters. <b>Conclusions:</b> Voluntary hyperventilation was associated with sympathetic predominance and CI increase in healthy volunteers, but only with minor hemodynamic and SVB effects in patients with HF and PAH. Simulated PB had positive effects on SVB in healthy volunteers but neutral effects on SVB and hemodynamics in patients with HF or PAH.

Zentrale Schlafapnoe bei Patienten mit Herzinsuffizienz: Physiologische Auswirkungen der periodischen Beatmung

Background: The effects of hyperventilation and hyperventilation in the context of periodic breathing (PB) on sympatho-vagal balance (SVB) and hemodynamics in conditions of decreased cardiac output and feedback resetting, such as heart failure (HF) or pulmonary arterial hypertension (PAH), are not completely understood. Objectives: To investigate the effects of voluntary hyperventilation and simulated PB on hemodynamics and SVB in healthy subjects, in patients with systolic HF and reduced or mid-range ejection fraction (HFrEF and HFmrEF) and in patients with PAH. Methods: Study participants (n = 20 per group) underwent non-invasive recording of diastolic blood pressure, heart rate variability (HRV), baroreceptor-reflex sensitivity (BRS), total peripheral resistance index (TPRI) and cardiac index (CI). All measurements were performed at baseline, during voluntary hyperventilation and during simulated PB with different length of the hyperventilation phase. Results: In healthy subjects, voluntary hyperventilation led to a 50% decrease in the mean BRS slope and a 29% increase in CI compared to baseline values (p < 0.01 and p < 0.05). Simulated PB did not alter TPRI or CI and showed heterogeneous effects on BRS, but analysis of dPBV revealed decreased sympathetic drive in healthy volunteers depending on PB cycle length (p < 0.05). In HF patients, hyperventilation did not affect BRS and TPRI but increased the CI by 10% (p < 0.05). In HF patients, simulated PB left all of these parameters unaffected. In PAH patients, voluntary hyperventilation led to a 15% decrease in the high-frequency component of HRV (p < 0.05) and a 5% increase in CI (p < 0.05). Simulated PB exerted neutral effects on both SVB and hemodynamic parameters. Conclusions: Voluntary hyperventilation was associated with sympathetic predominance and CI increase in healthy volunteers, but only with minor hemodynamic and SVB effects in patients with HF and PAH. Simulated PB had positive effects on SVB in healthy volunteers but neutral effects on SVB and hemodynamics in patients with HF or PAH.