Breath holding as an example of extreme hypoventilation: experimental testing of a new model describing alveolar gas pathways

Taboni, Anna; Fagoni, Nazzareno; Fontolliet, Timothée; Grasso, Gabriele; Moia, Christian; Vinetti, Giovanni; Ferretti, Guido

doi:10.1113/ep088977

Cited by 10 publications

(9 citation statements)

References 37 publications

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“…Moreover, data concerning the durations of the different phases between air and oxygen confirms previous findings. In resting apnoeas, φ2 is shorter in air than in oxygen, and is absent during exercise apnoeas in air, whereas it is possible to identify the φ2 during apnoeas carried out after breathing pure oxygen (Sivieri et al 2015;Fagoni et al 2015;Taboni et al 2018bTaboni et al , 2020. Probably the higher oxygen stores compared to air apnoeas increase the total duration of apnoea.…”

Section: Methodological Considerationsmentioning

confidence: 99%

“…The PRE-ss HR and MAP and their respective values and during φ2 were computed from the maximal apnoeas, both at rest and during exercise. Only exception concerned exercise apnoeas in air, for the lack of φ2 (Sivieri et al 2015;Taboni et al 2018bTaboni et al , 2020). An automated procedure implemented under MATLAB (version 7.6.0.324, MathWorks ® , Natick, MA, USA) was used to this aim.…”

Section: Measurements and Data Treatmentmentioning

confidence: 99%

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Baroreflex responses during dry resting and exercise apnoeas in air and pure oxygen

et al. 2020

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Purpose We analysed the characteristics of arterial baroreflexes during the first phase of apnoea (φ1). Methods 12 divers performed rest and exercise (30 W) apnoeas (air and oxygen). We measured beat-by-beat R-to-R interval (RRi) and mean arterial pressure (MAP). Mean RRi and MAP values defined the operating point (OP) before (PRE-ss) and in the second phase (φ2) of apnoea. Baroreflex sensitivity (BRS, ms·mmHg−1) was calculated with the sequence method. Results In PRE-ss, BRS was (median [IQR]): at rest, 20.3 [10.0–28.6] in air and 18.8 [13.8–25.2] in O2; at exercise 9.2[8.4–13.2] in air and 10.1[8.4–13.6] in O2. In φ1, during MAP decrease, BRS was lower than in PRE-ss at rest (6.6 [5.3–11.4] in air and 7.7 [4.9–14.3] in O2, p < 0.05). At exercise, BRS in φ1 was 6.4 [3.9–13.1] in air and 6.7 [4.1–9.5] in O2. After attainment of minimum MAP (MAPmin), baroreflex resetting started. After attainment of minimum RRi, baroreflex sequences reappeared. In φ2, BRS at rest was 12.1 [9.6–16.2] in air, 12.9 [9.2–15.8] in O2. At exercise (no φ2 in air), it was 7.9 [5.4–10.7] in O2. In φ2, OP acts at higher MAP values. Conclusion In apnoea φ1, there is a sudden correction of MAP fall via baroreflex. The lower BRS in the earliest φ1 suggests a possible parasympathetic mechanism underpinning this reduction. After MAPmin, baroreflex resets, displacing its OP at higher MAP level; thus, resetting may not be due to central command. After resetting, restoration of BRS suggests re-establishment of vagal drive.

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Section: Methodological Considerationsmentioning

confidence: 99%

Section: Measurements and Data Treatmentmentioning

confidence: 99%

Baroreflex responses during dry resting and exercise apnoeas in air and pure oxygen

et al. 2020

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“…Farhi and Rahn (1955) later proposed that the alveolar pathway of ventilatory unsteady states can be described by exponential functions. Taboni et al (2020) treated the alveolar gas pathways during breath-holding as an extreme hypoventilation loop. The theoretical loop is shown in Fig.…”

Section: Breaking the Equilibrium: Breath-holdingmentioning

confidence: 99%

“…Taboni et al ( 2020 ) treated the alveolar gas pathways during breath-holding as an extreme hypoventilation loop. The theoretical loop is shown in Fig.…”

Section: Breaking the Equilibrium: Breath-holdingmentioning

confidence: 99%

A century of exercise physiology: key concepts on coupling respiratory oxygen flow to muscle energy demand during exercise

et al. 2022

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After a short historical account, and a discussion of Hill and Meyerhof’s theory of the energetics of muscular exercise, we analyse steady-state rest and exercise as the condition wherein coupling of respiration to metabolism is most perfect. The quantitative relationships show that the homeostatic equilibrium, centred around arterial pH of 7.4 and arterial carbon dioxide partial pressure of 40 mmHg, is attained when the ratio of alveolar ventilation to carbon dioxide flow ($${\dot{V}}_{A}/{\dot{V}}_{R}{CO}_{2}$$ V ˙ A / V ˙ R CO 2 ) is − 21.6. Several combinations, exploited during exercise, of pertinent respiratory variables are compatible with this equilibrium, allowing adjustment of oxygen flow to oxygen demand without its alteration. During exercise transients, the balance is broken, but the coupling of respiration to metabolism is preserved when, as during moderate exercise, the respiratory system responds faster than the metabolic pathways. At higher exercise intensities, early blood lactate accumulation suggests that the coupling of respiration to metabolism is transiently broken, to be re-established when, at steady state, blood lactate stabilizes at higher levels than resting. In the severe exercise domain, coupling cannot be re-established, so that anaerobic lactic metabolism also contributes to sustain energy demand, lactate concentration goes up and arterial pH falls continuously. The $${\dot{V}}_{A}/{\dot{V}}_{R}{CO}_{2}$$ V ˙ A / V ˙ R CO 2 decreases below − 21.6, because of ensuing hyperventilation, while lactate keeps being accumulated, so that exercise is rapidly interrupted. The most extreme rupture of the homeostatic equilibrium occurs during breath-holding, because oxygen flow from ambient air to mitochondria is interrupted. No coupling at all is possible between respiration and metabolism in this case.

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“…5A, B, both P < 0.003). Although these findings suggest that breathhold-induced hypercapnia did not directly affect MCA V mean and PCA V mean , the previous evidence has suggested the possibility that apnoeas of longer duration, where hypercapnia is present or a delta CO 2 is high, show modifications of the CBF velocities (Fagoni et al 2017;Taboni et al 2020). In addition, it has been reported that hypercapnia impairs dynamic cerebral autoregulation (Ainslie and Duffin 2009).…”

Section: Discussionmentioning

confidence: 82%

Effect of breath-hold on the responses of arterial blood pressure and cerebral blood velocity to isometric exercise

et al. 2021

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Purpose The present study examined the effect of breath-hold without a Valsalva maneuver during isometric exercise on arterial blood pressure (ABP) and cerebral blood flow (CBF). Methods Twenty healthy adults (15 men and five women) randomly performed only breath-hold without a Valsalva maneuver (BH), and an isometric handgrip exercise for 30 s at 40% of individual maximal voluntary contraction with continuous breathing (IHG) and with breath-hold without the Valsalva maneuver (IHG-BH). Mean ABP (MAP) and blood velocity in the middle (MCA V mean ) and posterior cerebral arteries (PCA V mean ) were continuously measured throughout each protocol. Results MAP was elevated during the IHG-BH compared with IHG (P < 0.001) and BH (P = 0.001). Similarly, both MCA V mean and PCA V mean were higher during IHG-BH compared with IHG and BH (all P < 0.001). Moreover, the relative change in MAP from the baseline was correlated with that in both cerebral blood velocities during the BH (MCA V mean : r = 0.739, P < 0.001 and PCA V mean : r = 0.570, P = 0.009) and IHG-BH (MCA V mean : r = 0.755, P < 0.001 and PCA V mean : r = 0.617, P = 0.003) condition, but not the IHG condition (P = 0.154 and P = 0.306). Conclusion These results indicate that during isometric exercise, a breath-hold enhances an exercise-induced increase in MAP and, consequently, MCA V mean and PCA V mean.

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Breath holding as an example of extreme hypoventilation: experimental testing of a new model describing alveolar gas pathways

Cited by 10 publications

References 37 publications

Baroreflex responses during dry resting and exercise apnoeas in air and pure oxygen

Baroreflex responses during dry resting and exercise apnoeas in air and pure oxygen

A century of exercise physiology: key concepts on coupling respiratory oxygen flow to muscle energy demand during exercise

Effect of breath-hold on the responses of arterial blood pressure and cerebral blood velocity to isometric exercise

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