Increased ventilatory variability and complexity in patients with hyperventilation disorder

Abstract

It has been hypothesized that hyperventilation disorders could be characterized by an abnormal ventilatory control leading to enhanced variability of resting ventilation. The variability of tidal volume (VT) often depicts a nonnormal distribution that can be described by the negative slope characterizing augmented breaths formed by the relationship between the probability density distribution of VT and VT on a log-log scale. The objectives of this study were to describe the variability of resting ventilation [coefficient of variation (CV) of VT and slope], the stability in respiratory control (loop, controller and plant gains characterizing ventilatory-chemoresponsiveness interactions) and the chaotic-like dynamics (embedding dimension, Kappa values characterizing complexity) of resting ventilation in patients with a well-defined dysfunctional breathing pattern characterized by air hunger and constantly decreased PaCO2 during a cardiopulmonary exercise test. Compared with 14 healthy subjects with similar anthropometrics, 23 patients with hyperventilation were characterized by increased variability of resting tidal ventilation (CV of VT median [interquartile]: 26% [19-35] vs. 36% [28-48], P = 0.020; slope: -6.63 [-7.65; -5.36] vs. -3.88 [-5.91; -2.66], P = 0.004) that was not related to increased chemical drive (loop gain: 0.051 [0.039-0.221] vs. 0.044 [0.012-0.087], P = 0.149) but that was related to an increased ventilatory complexity (Kappa values, P < 0.05). Plant gain was decreased in patients and correlated with complexity (with Kappa 5 - degree 5: Rho = -0.48, P = 0.006). In conclusion, well-defined patients suffering from hyperventilation disorder are characterized by increased variability of their resting ventilation due to increased ventilatory complexity with stable ventilatory-chemoresponsiveness interactions.

Exercise ventilatory irregularity can be quantified by approximate entropy to detect breathing pattern disorder

“…Many individuals with 'idiopathic' or unexplained breathlessness are now recognized to have irregularities in the pattern and control of their breathing, both at rest and during exercise. 20,21 Historically, individuals with this clinical presentation were described as chronically 'hyperventilating'. Defining and characterising this abnormality, based on the presence of systemic hypocapnia, has however proven difficult.…”

“…24 Accordingly, more recent work has focussed on detecting irregularities in breathing pattern. 2,6,20 Such breathing pattern irregularities appear to be ubiquitous in those with idiopathic breathlessness or hyperventilation 20,25 yet new, readily-accessible, objective techniques are needed to quantify these breathing pattern abnormalities. Caldirola and colleagues 15 utilised the mathematical approach of ApEn analysis to evaluate ventilatory indices acquired from resting breath-by-breath data, to successfully quantify increased ventilatory irregularity in a cohort of individuals with anxiety disorders.…”

“…Specifically, in both respiratory and cardiac disorders, evaluating non-linear statistical models of temporal fluctuation in ventilatory and/or airflow parameters appears to be associated with disease control and prognosis. 20,[27][28][29] Perhaps the most comprehensively studied variable, in this context, is heart rate variability (HRV) 30 several studies indicate that reduced HRV is associated with a poor cardiac prognosis. Thus generally speaking it is believed that irregularity in a time series of physiological data is desirable and associated with 'favourable' pliability within a physiological system.…”

Pathophysiology of dyspnoea in acute pulmonary embolism: A cross‐sectional evaluation

“…Nevertheless, in a multivariate analysis, the sensory‐affective domain of dyspnoea was associated with the depression trait, accordingly with our initial hypothesis. VT demonstrates some physiological variability, any deviation, that is reduction or augmentation, could promote dyspnoea sensation. Interestingly, we further showed that the decreased variability of VT was associated with the sensory‐affective domain of dyspnoea in PE.…”

Novel assessment tool to detect breathing pattern disorder in patients with refractory asthma

“…It is possible to measure breathing pattern by assessing changes in amplitude and frequency of tidal volume using several techniques (e.g. optical electronic plethysmography and manual assessment of respiratory motion).…”