Effects of Acceleration on the Lung

Glaister, D. H.

doi:10.1201/b15295-3

Cited by 19 publications

(27 citation statements)

References 12 publications

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“…Corresponding data from hypergravity are sparse. Pulmonary perfusion becomes more heterogeneous with increasing G force (Hlastala et al 1998;Glaister, 2001) and the same is true for ventilation distribution and ventilation-to-perfusion ratio in supine posture during hypergravity. To our knowledge, there are no reports of comparisons between the topographical ventilation/perfusion distributions in prone and supine posture during hypergravity.…”

Section: Intrathoracic Pressure Gradients and Ventilationperfusion Inmentioning

confidence: 73%

“…We increased intrathoracic hydrostatic pressure gradients with resulting gas exchange impairment by exposing subjects to hypergravity (Barr, 1962;Glaister, 1967Glaister, , 1970Glaister, , 2001, and we hypothesized that the protective effect of prone posture seen in patients with lung insufficiency would be demonstrable also in healthy humans under conditions of hypergravity. If so, the beneficial effects of prone posture in patients with lung insufficiency would at least in part rely on basic structural properties of the lungs, rather than on reversal of a disease process.…”

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confidence: 99%

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Protective effect of prone posture against hypergravity-induced arterial hypoxaemia in humans

Rohdin

Petersson

Mure

et al. 2003

The Journal of Physiology

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Patients with acute respiratory distress syndrome have increased lung tissue weight and therefore an increased hydrostatic pressure gradient down the lung. Also, they have a better arterial oxygenation in prone (face down) than in supine (face up) posture. We hypothesized that this effect of the direction of gravity also existed in healthy humans, when increased hydrostatic gradients were induced by hypergravity. Ten healthy subjects were studied in a human centrifuge while exposed to 1 or 5 G in anterio-posterior (supine) or posterio-anterior (prone) direction. We measured blood gases using remote-controlled sampling and gas exchange by mass spectrometry. Hypergravity led to marked impairments of arterial oxygenation in both postures and more so in supine posture. At 5 G, the arterial oxygen saturation was 84.6 +/- 1.2 % (mean +/- S.E.M.) in supine and 89.7 +/- 1.4 % in prone posture (P < 0.001 for supine vs. prone). Ventilation and alveolar PO2 were increased at 5 G and did not differ between postures. The alveolar-to-arterial PO2 difference increased at 5 G to 8.0 +/- 0.2 kPa and 6.6 +/- 0.3 kPa in supine and prone postures (P = 0.003). Arterial oxygenation was less impaired in prone during hypergravity due to a better-preserved alveolo-arterial oxygen transport. We speculate that mammals have developed a cardiopulmonary structure that favours function with the gravitational vector in the posterio-anterior direction.

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Section: Intrathoracic Pressure Gradients and Ventilationperfusion Inmentioning

confidence: 73%

mentioning

confidence: 99%

Protective effect of prone posture against hypergravity-induced arterial hypoxaemia in humans

Rohdin

Petersson

Mure

et al. 2003

The Journal of Physiology

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“…Before G-LOC, Wilson et al (33) found a widespread, high-frequency activity at ϳ33 Hz, starting at 40% of ϩG z , at which individuals lost consciousness. At this point, cerebral regional oxygen saturation remained unchanged to normal gravity conditions (11), although broad declines in mean arterial pressure and mean blood flow velocities in the middle cerebral artery have been found between ϩ2G z and ϩ3G z (21).…”

Section: Discussionmentioning

confidence: 97%

The relationship between brain cortical activity and brain oxygenation in the prefrontal cortex during hypergravity exposure

Smith

Goswami

Robinson

et al. 2013

Journal of Applied Physiology

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Artificial gravity has been proposed as a method to counteract the physiological deconditioning of long-duration spaceflight; however, the effects of hypergravity on the central nervous system has had little study. The study aims to investigate whether there is a relationship between prefrontal cortex brain activity and prefrontal cortex oxygenation during exposure to hypergravity. Twelve healthy participants were selected to undergo hypergravity exposure aboard a short-arm human centrifuge. Participants were exposed to hypergravity in the +Gz axis, starting from 0.6 +Gz for women, and 0.8 +Gz for men, and gradually increasing by 0.1 +Gz until the participant showed signs of syncope. Brain cortical activity was measured using electroencephalography (EEG) and localized to the prefrontal cortex using standard low-resolution brain electromagnetic tomography (LORETA). Prefrontal cortex oxygenation was measured using near-infrared spectroscopy (NIRS). A significant increase in prefrontal cortex activity (P < 0.05) was observed during hypergravity exposure compared with baseline. Prefrontal cortex oxygenation was significantly decreased during hypergravity exposure, with a decrease in oxyhemoglobin levels (P < 0.05) compared with baseline and an increase in deoxyhemoglobin levels (P < 0.05) with increasing +Gz level. No significant correlation was found between prefrontal cortex activity and oxy-/deoxyhemoglobin. It is concluded that the increase in prefrontal cortex activity observed during hypergravity was most likely not the result of increased +Gz values resulting in a decreased oxygenation produced through hypergravity exposure. No significant relationship between prefrontal cortex activity and oxygenation measured by NIRS concludes that brain activity during exposure to hypergravity may be difficult to measure using NIRS. Instead, the increase in prefrontal cortex activity might be attributable to psychological stress, which could pose a problem for the use of a short-arm human centrifuge as a countermeasure.

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“…Due to the 28° reclined back of the seat in the Gripen, the weights of the rib cage and jacket will result in a compression of the thoracic cage which is proportional to the G load. Infl ation of the abdominal bladder in the anti-G suit will counteract the G-induced lowering of the diaphragm, and thus, presumably, facilitate compression of the lower, basilar regions of the thoracic cage and lungs ( 7 ). PPB has been used for a long time to prevent hypoxia in case of decompression in the cabin when fl ying at high altitude (pressure breathing for altitude protection; PBA).…”

Section: Discussionmentioning

confidence: 99%

Lung Mechanics and Transpulmonary Pressures During Unassisted Pressure Breathing at High G<SUB>z</SUB> Loads

Grönkvist¹,

Bergsten²,

Eiken³

2008

aviat space environ med

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Effects of Acceleration on the Lung

Cited by 19 publications

References 12 publications

Protective effect of prone posture against hypergravity-induced arterial hypoxaemia in humans

Protective effect of prone posture against hypergravity-induced arterial hypoxaemia in humans

The relationship between brain cortical activity and brain oxygenation in the prefrontal cortex during hypergravity exposure

Lung Mechanics and Transpulmonary Pressures During Unassisted Pressure Breathing at High G<SUB>z</SUB> Loads

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