Title

Cerebral blood flow velocity during combined lower body negative pressure and cognitive stress

Authors

John J. Durocher, Michigan Technological UniversityFollow
Jason R. Carter, Michigan Technological UniversityFollow
William H. Cooke, Michigan Technological UniversityFollow
Angela H. Young
Morton H. Harwood

Document Type

Article

Publication Date

8-1-2015

Abstract

BACKGROUND: Lower body negative pressure (LBNP) decreases middle cerebral artery blood velocity (MCAv) and can induce hypotension. Mental stress increases MCAv, but the MCAv response to combined LBNP and mental stress (COMBO) is unknown. We hypothesized that performing a stressful cognitive challenge (i.e., mental stress) concurrently with LBNP would prevent LBNP-induced reductions of MCAv.

METHODS: There were 18 subjects (9 men, 9 women; ages 20.1 ± 0.3 yr) who completed 3 randomized 3-min trials: 1) LBNP (−40 mmHg); 2) mental stress (serial subtraction); and 3) COMBO (LBNP + mental stress). All reported values are mean ± SE. Mean arterial pressure (MAP), heart rate (HR), forearm blood flow (FBF), and MCAv were measured continuously. Subjects also reported perceived stress following the mental stress and COMBO trials.

RESULTS: LBNP decreased MAP (−1.4 ± 0.5 mmHg), MCAv (−2.6 ± 1.1 cm s⁻¹) and FBF (−0.8 ± 0.1 units), and increased HR (2.7 ± 1.2 bpm). Mental stress increased MAP (10.1 ± 1.3 mmHg), HR (17.4 ± 2.2 bpm), and FBF (2.4 ± 0.4 units), while MCAv (2.8 ± 1.3 cm s⁻¹) tended to increase. COMBO increased MAP (5.3 ± 2.3 mmHg) and HR (21.3 ± 2.6 bpm), and tended to increase FBF (0.5 ± 0.3 units). However, MCAv (-4.6 ± 2.0 cm s−1) decreased during COMBO. Decreases in MCAv during COMBO were not statistically different from LBNP-induced decreases (−4.6 ± 2.0 vs. −2.6 ± 1.1 cm s⁻¹). Subjective ratings of perceived stress (standard 0 to 4 scale) tended to be higher during COMBO than mental stress (2.9 ± 0.1 vs. 2.5 ± 0.1 units).

CONCLUSION: Our results suggest that mental stress does not effectively preserve MCAv when combined with central hypovolemia (i.e., LBNP).

Publisher's Statement

© 2015 by the Aerospace Medical Association Publisher's version of record: https://doi.org/10.3357/AMHP.4239.2015

Publication Title

Aerospace Medicine and Human Performance

Recommended Citation

Durocher, J. J., Carter, J. R., Cooke, W. H., Young, A. H., & Harwood, M. H. (2015). Cerebral blood flow velocity during combined lower body negative pressure and cognitive stress. Aerospace Medicine and Human Performance, 86(8), 688-692. http://doi.org/10.3357/AMHP.4239.2015
Retrieved from: https://digitalcommons.mtu.edu/kip-fp/96