Centrifugal Force and Blood Pressure Elevation in the Wings of Flying Hummingbirds (Trochilidae)

Whereas circulatory consequences of large body size are known to include dramatic elevation of blood pressure, other physical contexts such as acceleration of fluid systems may also impose physiological demands. Centrifugal forces acting on rapidly reciprocating appendages may in particular challenge circulatory system performance. In hummingbirds, a physical model suggests that mean wing blood pressure during flapping flight can increase by about 50 mm Hg through centrifugal forces acting on spanwise blood columns. These centrifugally induced pressures correspond to a blood pressure elevation of approximately 30% relative to resting avian blood pressures. For hummingbird species ranging over an order of magnitude in body mass, estimated allometric variation in blood-pressure elevation owing to centrifugal forces is small. Centrifugal enhancement of blood pressure may characterize large amplitude wing motions in all flying animals.