What good old breath-holding tests really show? or Good old breath-holding test does not reflect the state of the cardiorespiratory system, but the ability of volitional inhibition of inspiratory neurons

Abstract

Background. The breath-holding tests of Stange (after a deep inspiration) and Guenchi (after a normal expiration) have been used in clinical and sports practice for more than a century as simple bedside markers of cardio-respiratory reserve. Their physiological meaning, however, has never been firmly established, and the literature has alternated between treating the test as an index of lung capacity, of haemodynamic efficiency or of CO₂ tolerance. Objectives. We aimed to verify whether the duration of voluntary apnoea really reflects the state of the cardiorespiratory system, or whether — as we hypothesised — it reflects mainly the capacity of supraspinal structures to inhibit the bulbar inspiratory generator. Material and methods. Forty-four adult patients with chronic pyelonephritis and cholecystitis in remission (34 men aged 23–70 years; 10 women aged 33–76 years) were examined twice — on admission and after 7–10 days of standard balneotherapy at Truskavets' Spa (Naftussya bioactive water, ozokerite, mineral baths). At each examination Stange's and Guenchi's tests were performed together with submaximal cycle-ergometer PWC₁₅₀, echocardiographic haemodynamics, heart rate variability (HRV), 16-lead resting EEG, faecal microbiota, urinary syndrome, gall-bladder cholekinetics, urinary and serum electrolytes, immunogram and phagocytic activity of neutrophils, giving a total of 88 paired observations. Correlation, multiple regression and canonical correlation analyses were applied. Results. Stange and Guenchi durations were entirely uncorrelated with each other (r = –0.02; Fig. 1) and only marginally with PWC₁₅₀. Classical haemodynamic parameters (cardiac output, ejection fraction, blood pressure, peripheral resistance, contractile-activity indices) failed to predict either test (|r| ≤ 0.18 throughout). In contrast, both apnoea durations were tightly linked to neural variables: Stange's test was determined by Baevskiy's Activity Regulation Systems Index, pNN₅₀, θ-power in central loci and α-rhythm frequency (R = 0.911; R² = 0.830; p < 10⁻⁶), while Guenchi's test depended on serum urea, %CD22 B-lymphocytes, frontal δ-power, occipito-temporal α-power, HF-band of HRV and β-index (R = 0.723; R² = 0.523; p < 10⁻⁵). Conclusions. The duration of a voluntary breath-hold does not measure pulmonary or cardiac reserve. It measures the central nervous capacity to override the chemoreflex — that is, the strength of cortical and autonomic inhibition of the bulbar inspiratory generator. Stange and Guenchi tests, although superficially similar, tap two largely independent neural circuits and should not be used interchangeably as markers of cardiorespiratory fitness.