https://ogma.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:35487 Thu 30 Jan 2020 13:53:08 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:2825 Sat 24 Mar 2018 08:28:25 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:11262 Sat 24 Mar 2018 08:10:52 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:42376 Mon 22 Aug 2022 14:29:29 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:12206 10%. Distortion of pulsed Doppler signal peaks occurred in the conscious rabbit at peak aortic velocities, at which Reynold's number for turbulence was exceeded and the Doppler shift surpassed the Nyquist limit of 31.25 kHz for the velocimeter. Although the Doppler shift-volume flow relationship is linear at < 5 kHz, in some cases at higher Doppler shifts and blood flow velocities the relationship may become nonlinear, thus causing the volume flow rate to be underestimated by up to 38%. The cause of this phenomenon may be "aliasing" and/or the consequence of the range control capability of the velocimeter selectively sampling changing velocity profiles and flow disturbances in the central stream at higher velocities.]]> Fri 27 Sep 2019 16:32:00 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:12405 br), Q_br conductance (C_br), bronchial hemicircumference (CIRC_br), and bronchial wall thickness (WALL TH_br) in recovered, standing, awake sheep. Methacholine (MCh; 0.125–2.0 μg/kg iv), at the highest dose, caused a 233% rise in Qbr (P < 0.05) and a 286% rise in C_br (P < 0.05). CIRC_br fell to 90% (P < 0.05); WALL TH_br did not change. In contrast, nebulized MCh (1–32 mg/ml), inhaled through a mask at the highest dose, caused a rise in ventilation and a rise in Qbr proportional to aortic pressure without change in C_br. CIRC_br fell to 91% (P < 0.01), and WALL TH_br did not change. Thus inhaled MCh has access to cholinoceptors of bronchial circumferential smooth muscle to cause airway lumen narrowing but effectively not to those of the systemic bronchovascular circulation. It is speculated that the mechanism is selective neuroparacrine inhibition of muscarinic acetylcholine receptors (M3 bronchovascular cholinoceptors) by prostanoids released by intense MCh activation of epithelial and mucosal cells lining the airway.]]> Fri 27 Sep 2019 16:25:54 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:12664 τ) has been calculated in dogs from the rearranged Kubicek formula: p_τ = (SV · Z₀²)/(L² dZ/dt_max·T), where SV was measured by the electromagnetic flowmeter (EM). Hematocrit (Hct) in the dog was varied by hemorrhage and infusion. In contrast to the direct and exponential bench p-Hct relationship, p_τ varies inversely with Hct, but by no more than +6.3 Ω · cm (at Hct 26%) and -11.8 Ω · cm (at Hct 66%) about a mean p_τ of 135 ± 1.0 Ω · cm (at Hct 40%). Impedance SV calculated using p_τ over a wide range of SV bears a linear relationship to EM values with a 95% prediction limit for a single SV estimate of ±0.84 about a mean value of 26.9 ml. The findings suggest that p_τ is virtually constant during a variety of physiological disturbances.]]> Fri 27 Sep 2019 16:12:28 AEST ]]>