China 
Africa 
Explore chapters and articles related to this topic
Pediatric Imaging in General Radiography
Published in Christopher M. Hayre, William A. S. Cox, General Radiography, 2020
Allen Corrall, Joanna Fairhurst
In their first few breaths the neonate establishes their total lung capacity, residual volume, and tidal volumes (the amount of air inhaled/exhaled at rest). The air within the airways (nose, trachea, and bronchiolar structures not actively involved in gaseous exchange) is known as dead space.
Animal Models
Published in Brian J. Lukey, James A. Romano, Salem Harry, Chemical Warfare Agents, 2019
The ratio of physiologic dead space over tidal volume (VD/VT) is a routine measurement expressing the ratio of dead-space ventilation (VD) to tidal ventilation (VT), as in physiologic research or the care of patients with respiratory disease. Inadequate pulmonary blood flow will result in increased dead-space ventilation, because there is inadequate blood flow through the lungs to exchange with the gas (ventilation in excess of perfusion). Its value in predicting mortality in patients has been reaffirmed by multiple studies (Cepkova et al., 2007; Fengmei et al., 2012; Lucangelo et al., 2008; Nuckton et al., 2002; Raurich et al., 2010). The specific value of measuring VD/VT to increase the understanding of the underlying pathophysiology of acute lung injuries is based on carbon dioxide’s relatively high diffusibility across tissue membranes compared with oxygen (West, 2008). Thus, VD/VT is considered to be a more perfusion-sensitive variable that may be useful as an indirect marker for pulmonary endothelial injury or vasoconstriction.
Airway
Published in Brian J Pollard, Gareth Kitchen, Handbook of Clinical Anaesthesia, 2017
Cyprian Mendonca, Narcis Ungureanu, Aleksandra Nowicka, William Tosh, Benjamin Robinson, Carol L Bradbury
Dead space is that part of inspired air that fails to take part in gas exchange. The volume of conducting airways leading up to the alveoli constitutes the anatomical dead space. The part of the alveolar air that does not take part in gas exchange accounts for alveolar dead space. The sum of the anatomical and alveolar dead space equates to the physiological dead space. The alveolar dead space increases in pulmonary embolism and in conditions with reduced cardiac output.
Chronic Thromboembolic Disease: Epidemiology, Assessment with Invasive Cardiopulmonary Exercise Testing, and Options for Management
Published in Structural Heart, 2021
W. Cameron McGuire, Mona Alotaibi, Timothy A. Morris, Nick H. Kim, Timothy M. Fernandes
Following the completion of the test, the data generated are used to calculate the direct Fick cardiac output at rest and with exertion. The hemodynamic tracings are reviewed and interpreted. Care is taken to avoid tracings with excessive noise and measurements obtained at end exhalation.16 Using the measured direct Fick, heart rate and hemodynamics, the rest and exercise pulmonary vascular resistance [PVR = (mean PA – PCWP)/CO], stroke volume [SV = CO/HR], pulmonary arterial compliance [PAC = SV/(systolic PA – diastolic PA)], and stroke volume reserve [SV Reserve = (SV at peak exercise/SV at rest)*100] are calculated. The changes in mean pulmonary artery pressure are assessed against the Fick cardiac output with the slope of the mPAP/CO line having important diagnostic implications.4 The measured dead space ventilation is compared with the dead space ventilation estimated by the transcutaneous CO2 monitor. The dead space at rest and the response to exercise in dead space ventilation are assessed. Secondary measures of dead space ventilation such as the VE/VCO2 slope are also calculated and assessed.
Risk assessment of components in tobacco smoke and e-cigarette aerosols: a pragmatic choice of dose metrics
Published in Inhalation Toxicology, 2021
Peter M. J. Bos, Lya G. Soeteman-Hernández, Reinskje Talhout
The following parameters are used in the approach; default values for these parameters are presented in Table 1. The Tidal Volume (TV) is the volume of air that is inhaled or exhaled during breathing at rest. The volume of air that remains in the lungs at the end of the exhalation phase in rest is called the Functional Residual Capacity (FRC). Default values considered to be average values for an average adult human being are 500 mL for TV and 2 L for FRC. Further, during a breathing cycle, approximately 30% of an inhaled volume of air will not reach the alveoli where gas exchange takes place, i.e. the dead space volume. Default parameter values on human smoking behavior are obtained from Djordjevic et al. (2000). After drawing a puff and one subsequent breathing-cycle, the interval until the next puff is set at 20 sec in smokers. Starting from a breathing-frequency at rest of 12 min−1, a 20-sec interval corresponds to four breathing cycles between puffs. Assuming thirteen puffs per cigarette, the time to smoke a cigarette lasts between 5 and 6 min.
Severe, transient pulmonary ventilation-perfusion mismatch in the lung after porcine high velocity projectile behind armor blunt trauma
Published in Experimental Lung Research, 2020
David Rocksén, Ulf P. Arborelius, Jenny Gustavsson, Mattias Günther
Ventilation parameters were obtained and computed by a Hamilton C2 ventilator. Physiological dead space, alveolar ventilation and CO2 slope, indicative of V′A/Q′ mismatch were computed by volumetric capnography, providing a noninvasive and continuous display of the fractional concentration or partial pressure of expired CO2 versus exhaled volume. A volumetric capnogram is divided into three phases. Phase I is the first gas exhaled that comes from the conducting airways and contains no CO2. Phase II represents gas exhaled from conducting airways mixed with gas from fast-emptying alveoli. Phase III represents gas exhaled from the alveoli, and the slope represents the changing time constant of the emptying alveoli; i.e., alveoli with a low V′A/Q′ ratio empty last and contain the highest amount of CO2.15 The physiological dead space calculation is derived from phase III.16 Physiological dead space from volumetric capnography corresponds to the Bohr equation.17 Alveolar ventilation = minute ventilation – physiological dead space.