Semenov Yury S, Popova Julia A, Luzhnov Petr V, Demin Artem V, Moreva Tatiana I, Kriushev Evgeny S, Nichiporuk Igor A, Dyachenko Alexander I
Department of Cardiovascular and Respiratory Physiology in Extreme Environments, Institute of Biomedical Problems of the Russian Academy of Sciences, Moscow, Russia.
Department of Biomedical Engineering, Bauman Moscow State Technical University, Moscow, Russia.
Front Physiol. 2024 Nov 27;15:1443349. doi: 10.3389/fphys.2024.1443349. eCollection 2024.
Negative pressure breathing is breathing with decreased pressure in the respiratory tract without lowering pressure acting on the torso. We lowered pressure only during inspiration (NPBin). NPBin is used to increase venous return to the heart and is considered as a countermeasure against redistribution of body fluids toward the head during spaceflight. Aims of our study were: to obtain quantitative information on NPBin-induced changes in parameters of circulation and respiration in healthy human at various rarefactions; to identify main processes involved in cardiorespiratory response to NPBin.
Cardiorespiratory response to 25 min of NPBin were studied, rarefaction ranged from -10 to -25 cmHO. Parameters of systemic, cerebral, and peripheral hemodynamics, as well as respiratory and gas exchange parameters, were measured with non-invasive methods (Finometer, impedance cardiography, rheoencephalography, transcranial Doppler ultrasonography, laser Doppler flowmetry, capillaroscopy). Concentrations of endothelin-1, atrial and brain natriuretic peptides precursors in venous blood, O and CO tensions in arterialized capillary blood were measured.
Tidal volume increased, respiratory rate decreased under NPBin with no significant changes in minute ventilation. Group averaged, respiratory rate and tidal volume changed approximately twice relative to their values observed under normal breathing. Despite the decrease in respiratory rate (up to 2-3 breaths/min), the results indicate CO wash-out. Changes in respiratory and gas exchange parameters were virtually independent of rarefaction level. Synchronous with breathing oscillations of circulatory parameters increased in amplitude under NPBin, while values of the parameters averaged over NPBin period changed little. Amplitude of oscillations in parameters associated with arteries virtually did not change with increasing rarefaction. Inspiration under NPBin reduced left ventricle stroke volume and arterial blood pressure, increased heart rate. Head blood filling decreased during inspiration under NPBin, the decrease increased almost linearly with increasing rarefaction. Parameters returned to their initial values after the end of inspiration. Peak-to-peak amplitude of oscillations under NPBin ranged: stroke volume 17-25 mL, mean arterial pressure 7-9 mmHg, heart rate 14-18 bpm. Peripheral hemodynamics responded to NPBin little.
Changes in stroke volume and central venous pressure during inspiration under NPBin appear to be the major phenomena mediating the effects of NPBin on the cardiorespiratory system.
负压呼吸是指呼吸道压力降低而作用于躯干的压力不降低的呼吸方式。我们仅在吸气时降低压力（吸气期负压呼吸，NPBin）。NPBin用于增加静脉回流至心脏，并被视为对抗太空飞行期间体液向头部重新分布的一种对策。我们研究的目的是：获取关于NPBin在不同减压程度下对健康人体循环和呼吸参数影响的定量信息；确定心肺对NPBin反应所涉及的主要过程。
研究了对25分钟NPBin的心肺反应，减压程度范围为-10至-25厘米水柱。采用非侵入性方法（Finometer、阻抗心动图、脑血流图、经颅多普勒超声、激光多普勒血流仪、毛细血管显微镜检查）测量全身、脑和外周血流动力学参数以及呼吸和气体交换参数。测量静脉血中内皮素-1、心房和脑钠肽前体的浓度，以及动脉化毛细血管血中的氧和二氧化碳张力。
NPBin作用下潮气量增加，呼吸频率降低，分钟通气量无显著变化。分组平均值显示，呼吸频率和潮气量相对于正常呼吸时观察到的值变化约两倍。尽管呼吸频率降低（降至每分钟2 - 3次呼吸），但结果表明有二氧化碳排出。呼吸和气体交换参数的变化实际上与减压程度无关。与呼吸同步，循环参数的振荡幅度在NPBin作用下增加，而在NPBin期间参数的平均值变化不大。与动脉相关的参数振荡幅度几乎不随减压程度增加而变化。NPBin作用下吸气时左心室搏出量和动脉血压降低，心率增加。NPBin作用下吸气时头部血液充盈减少，且随着减压程度增加几乎呈线性增加。吸气结束后参数恢复到初始值。NPBin作用下振荡的峰峰值范围为：搏出量17 - 25毫升，平均动脉压7 - 9毫米汞柱，心率14 - 18次/分钟。外周血流动力学对NPBin反应较小。
NPBin作用下吸气时搏出量和中心静脉压的变化似乎是介导NPBin对心肺系统影响的主要现象。
