Department of Anaesthesiology, Pharmacology, Intensive Care and Emergencies, University of Geneva, Geneva, Switzerland.
Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy.
Exp Physiol. 2020 Dec;105(12):2216-2225. doi: 10.1113/EP088977. Epub 2020 Oct 15.
What is the central question of this study? We modelled the alveolar pathway during breath holding on the hypothesis that it follows a hypoventilation loop on the O -CO diagram. What is the main finding and its importance? Validation of the model was possible within the range of alveolar gas compositions compatible with consciousness. Within this range, the experimental data were compatible with the proposed model. The model and its characteristics might allow predictions of alveolar gas composition whenever the alveolar ventilation goes to zero; for example, static and dynamic breath holding at the surface or during ventilation/intubation failure in anaesthesia.
According to the hypothesis that alveolar partial pressures of O and CO during breath holding (BH) should vary following a hypoventilation loop, we modelled the alveolar gas pathways during BH on the O -CO diagram and tested it experimentally during ambient air and pure oxygen breathing. In air, the model was constructed using the inspired and alveolar partial pressures of O ( and , respectively) and CO ( and , respectively) and the steady-state values of the pre-BH respiratory exchange ratio (RER). In pure oxygen, the model respected the constraint of . To test this, 12 subjects performed several BHs of increasing duration and one maximal BH at rest and during exercise (30 W cycling supine), while breathing air or pure oxygen. We measured gas flows, and before and at the end of all BHs. Measured data were fitted through the model. In air, = 150 ± 1 mmHg and = 0.3 ± 0.0 mmHg, both at rest and at 30 W. Before BH, steady-state RER was 0.83 ± 0.16 at rest and 0.77 ± 0.14 at 30 W; = 107 ± 7 mmHg at rest and 102 ± 8 mmHg at 30 W; and = 36 ± 4 mmHg at rest and 38 ± 3 mmHg at 30 W. By model fitting, we computed the RER during the early phase of BH: 0.10 [95% confidence interval (95% CI) = 0.08-0.12] at rest and 0.13 (95% CI = 0.11-0.15) at 30 W. In oxygen, model fitting provided : 692 (95% CI = 688-696) mmHg at rest and 693 (95% CI = 689-698) mmHg at 30 W. The experimental data are compatible with the proposed model, within its physiological range.
本研究的核心问题是什么？我们基于假设在呼吸暂停期间肺泡途径遵循 O -CO 图上的低通气环来建立模型。主要发现及其重要性是什么？在与意识相容的肺泡气体组成范围内，模型可以得到验证。在这个范围内，实验数据与提出的模型相符。该模型及其特征可能允许在肺泡通气降至零时预测肺泡气体组成；例如，在表面进行静态和动态呼吸暂停或麻醉期间通气/插管失败时。
根据在呼吸暂停期间（BH）肺泡中 O 和 CO 分压应遵循低通气环的假设，我们在 O -CO 图上建立了 BH 期间的肺泡气体途径模型，并在空气和纯氧呼吸时进行了实验验证。在空气中，该模型使用吸入和肺泡中 O 的分压（分别为 和 ）和 CO 的分压（分别为 和 ）以及 BH 前的稳态呼吸交换比（RER）值来构建。在纯氧中，模型遵守 的限制。为了验证这一点，12 名受试者在休息和运动（仰卧位 30 W 自行车）时，分别在空气或纯氧中进行了多次不同持续时间的 BH 和一次最大 BH，并测量了气体流量、 和 。在所有 BH 之前和结束时测量了这些值。通过模型拟合来测量数据。在空气中， 为 150 ± 1 mmHg， 为 0.3 ± 0.0 mmHg，无论在休息时还是在 30 W 时均如此。BH 前，休息时的稳态 RER 为 0.83 ± 0.16，30 W 时为 0.77 ± 0.14； 为 107 ± 7 mmHg，休息时为 102 ± 8 mmHg，30 W 时为 102 ± 8 mmHg； 为 36 ± 4 mmHg，休息时为 38 ± 3 mmHg，休息时为 38 ± 3 mmHg。通过模型拟合，我们计算了 BH 早期的 RER：休息时为 0.10 [95%置信区间（95% CI）= 0.08-0.12]，30 W 时为 0.13（95% CI = 0.11-0.15）。在氧气中，模型拟合提供了 ：休息时为 692（95% CI = 688-696）mmHg，30 W 时为 693（95% CI = 689-698）mmHg。实验数据与提出的模型在其生理范围内是相符的。
