Dead space anatomical

Distinguish among anatomical dead space, alveolar dead space, and physiological dead space... 

Alveolar ventilation. Alveolar ventilation is less than the total ventilation because the last portion of each tidal volume remains in the conducting airways therefore, that air does not participate in gas exchange. As mentioned at the beginning of the chapter, the volume of the conducting airways is referred to as anatomical dead space. The calculation of alveolar ventilation includes the tidal volume adjusted for anatomical dead space and includes only air that actually reaches the respiratory zone ... 

Dead space. Anatomical dead space is equal to the volume of the conducting airways. This is determined by the physical characteristics of the lungs because, by definition, these airways do not contain alveoli to participate in gas exchange. Alveolar dead space is the volume of air that enters unperfused alveoli. In other words, these alveoli receive airflow but no blood flow with no blood flow to the alveoli, gas exchange cannot take place. Therefore, alveolar dead space is based on functional considerations rather than anatomical factors. Healthy lungs have little or no alveolar dead space. Various pathological conditions, such as low cardiac output, may result in alveolar dead space. The anatomical dead space combined with the alveolar dead space is referred to as physiological dead space ... 

It is calculated by measuring the nitrogen concentration in expired gas after a single breath of 100% oxygen. The nitrogen wash-out test is the same method used to measure anatomical dead space. Closing volume increases with age and reaches the standing FRC at 70 years and the supine FRC at 40 years. 

The anatomical dead space can be measured by Fowler s method. 

Phase 2 A mixture of dead space gas and alveolar gas. The curve rises steeply to a plateau. Demonstrate a vertical line that intercepts this curve such that area A equals area B. The anatomical dead space is taken as the volume expired at this point. 

Conducting airways do not contribute to the gas exchange and can be considered to be merely a conduit between the external environment and the respiratory zone (vide infra). The volume of air accommodated by the conducting airways represents the anatomic dead space and is air not directly available for gas exchange. Aside from serving as a conduit to the respiratory zone, the conducting airways perform two other functions gas buffering and humidification. 

The single-breath nitrogen (Ng) test is a simple, sensitive test whose major usefulness is in its diagnostic value in the early stages of airway obstruction. This test is also valuable in the assessment of anatomical dead space, uneven ventilation, and abnormal intrapulmonary gas mixing (Buist, 1975). 

Deposition in the thoracic region is the sum of aerodynamic and thermodynamic deposition of particulate material. Aerodynamic deposition depends on aerodynamic particle size, total volumetric flow rate, anatomical dead space, tidal volume, functional residual capacity (FRC) (combined residual and expiratory reserve volume or the amount of air remaining in the lungs after a tidal expiration) and diameter of the airways. Thermodynamic deposition depends on anatomical and physical characteristics, such as tidal volume, anatomical dead space, functional residual capacity and the transit time of air within each region. Thermodynamic particle size, which is derived from the diffusion coefficient, particle shape factor and the particles mass density, influence thermodynamic deposition. 

Values estimating the variability for Vp in 1-year-old children and 3-month-old infants were not available in the open literature therefore, an alternative method was used to estimate their variability. Vp correlates better with an individuals height than any other anatomical parameter (Zapletal et al., 1987 Phalen et al., 1985). The variability in height (Stoudt et al., 1960), and hence anatomical dead space, is assumed to be normally distributed, and the percent standard deviation in height has been applied as a measure of the age-specific variability in anatomical dead space. 

Anatomical dead space is an important parameter with respect to deposition of particulate material in the AI region of 5-year-old children. Ten-year-old children, regardless of breathing pattern, demonstrate a similar relationship with respect to which parameters are most... 

Generally, fractional deposition in the lung, as modeled in ICRP 66 (1994), is directly proportional to particle mass density and BR, and inversely proportional to trachea diameter. Other parameters play a relatively minor role in modefing regional deposition within the respiratory tract for adults, adolescents and 10-year-old children. The parameters of anatomical dead space and windspeed are more important to deposition in infants and children. Research into these more sensitive parameters and their distributions may lead to reduction in the uncertainty of... 

Widdicombe JG. Nasal pathophysiology. Respir Med 1990 84(suppl A) 3-10. Numa AH, Newth CJL. Anatomic dead space in infants and children. J Appl Physiol 1996 80 1485-1489. 

Methodologieally, the differenee between these two types of samples is the control over which portion of the breath is collected. Many techniques make use of the Haldane-Prestley tube to collect the last portion of the expiration. Earlier work used the simultaneous monitoring of COj or temperature in the exhaled breath to identify the moment (CO2 or temperature reaching a maximum) when air from the anatomical dead space has been purged and alveolar air can be sampled. 

The solvent is not soluble in the conducting portion of the lung (anatomical dead space). 

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