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. 2021 Jun;9(11):e14882.
doi: 10.14814/phy2.14882.

Altered chemosensitivity to CO2 during exercise

Stanley M Yamashiro  1 , Takahide Kato  2 , Takaaki Matsumoto  3
Affiliations

Altered chemosensitivity to CO2 during exercise

Stanley M Yamashiro et al. Physiol Rep. 2021 Jun.

Abstract

The effect of exercise on chemosensitivity to carbon dioxide (CO2 ) has been controversial. Most studies have been based on rebreathing to alter inspired CO2 which is poorly tolerated in exercise. Instead, inhaling a fixed 3% CO2 from rest to moderate exercise was found to be well tolerated by seven normal subjects enabling CO2 chemosensitivity to be studied with minimal negative reaction. Results showed that chemosensitivity to CO2 following 5-6 min of stimulation was significantly enhanced during mild exercise (p < 0.01). This motivated exploring how much of the dynamic ventilatory response to mild exercise breathing air could be predicted by a model with central and peripheral chemosensitivity. Chemoreceptor stimulation combined with hypercapnia has been associated with long-term facilitation of ventilation (LTF). 3% CO2 inhalation during moderate exercise led to ventilation augmentation consistent with LTF following 6 min of exercise in seven normal human subjects (p < 0.01). Increased ventilation could not be attributed to hypercapnia or metabolic changes. Moderate exercise breathing air resulted in significantly less augmentation. In conclusion, both peripheral and central chemosensitivity to CO2 increased in exercise with the peripheral chemoreceptors playing a dominant role. This separation of central and peripheral contributions was not previously reported. This chemoreceptor stimulation can lead to augmented ventilation consistent with LTF.

Keywords: CO2 inhalation; chemosensitivity; exercise.

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Conflict of interest statement

No conflicts of interest, financial or otherwise, are declared by the author (s).

Figures

FIGURE 1
FIGURE 1
CO2 responses from rest to moderate exercise. VE, minute ventilation; PetCO2, end‐tidal partial pressure of CO2. Response slopes: rest 0.83, 40W 3.48, 45%VO2max 5.35 (L/min)/mmHg
FIGURE 2
FIGURE 2
Correlation of ventilation with CO2 production rate in time. VE, minute ventilation; VCO2, minute carbon dioxide output
FIGURE 3
FIGURE 3
Central and peripheral model prediction compared to measured ventilation. VE, minute ventilation; G p, peripheral gain; G c, central gain
FIGURE 4
FIGURE 4
Averaged ventilation response in seven subjects to 45% VO2max and 3% CO2 inhalation. Values are means ± SEM. Baseline was 40 W exercise and 3% CO2 inhalation. Averaged responses to 45% Maximum VO2 breathing air‐dashed line curve
FIGURE 5
FIGURE 5
Individual subject 40W exercise response fitted with model. VE, minute ventilation; G p, peripheral gain; G c, central gain
See this image and copyright information in PMC

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