Does mean arterial blood pressure scale with body mass in mammals? - effects of measurement of blood pressure.

For at least the last 30 years it has been discussed whether mean arterial blood pressure (MAP) is independent of body mass or whether it increases in accordance with the vertical height between the heart and the brain. The debate has centered on the most appropriate mathematical models for analysing allometric scaling and phylogenetic relationships, there has been preciously little focus on evaluating the validity of underlying physiological data. Currently, the two most comprehensive scaling analyses are based on data from 47 species of mammals, based on 114 references. We reviewed all available references to determine under which physiological conditions MAP had been recorded. In 44 (38.6%) of the cited references MAP was measured in anaesthetized animals. Data from conscious animals were reported in 59 (51.8%) of references, of these 3 (2.6%) were radiotelemetric studies. In 5 species, data were reported from both anaesthetized and conscious animals, the mean difference in MAP between these settings was 20 ± 29 mmHg. From a literature search we identified MAP measurements performed by radiotelemetry in 11 of the 47 species included in the meta-analyses. A Bland-Altman analysis showed a bias of 1 mmHg with 95% confidence interval (from -35 to 36 mmHg); i.e. the limits of agreement between radiotelemetric studies and studies in restrained animals was double the supposed difference in MAP between the mouse and elephant. In conclusion, the existing literature does not provide evidence for either a positive or neutral scaling of arterial pressure to body mass across taxa. This article is protected by copyright. All rights reserved.