Alveolar breath

Phillips M, Greenberg J. 1992. Ion-trap detection of volatile organic compounds in alveolar breath. Clin Chem (Winston-Salem, N. C.) 38(l) 60-5. 

Euler, D.E., Dave, S.J., and Guo, H. Effect of cigarette smoking on pentane excretion in alveolar breath, Clin. Chem., 42 303-308, 1996. 

Raymer JH, Thomas KW, Cooper SD, et al. 1990. A device for sampling of human alveolar breath for the measurement of expired volatile organic compounds. J Anal Toxicol 14 337-344. 

A simple method for the analysis of small volumes of gas from single-breath samples from humans was described by Zarling and Clapper (1987). Total breath samples were collected into a gas-tight bag and 50 ml aliquots withdrawn into polyethylene/polypropylene syringes. Alveolar breath samples collected by use of a Haldane-Priestly tube were also collected in this way. Gas samples were injected directly into the GLC via a gas-sampling valve. 

Raymer JH, Thomas K, Cooper S, et al. 1989. VOC breath measurement study Alveolar breath method, final report. Research Triangle Park, NC Research Triangle Institute. 

Pulmonary retention (net respiratory uptake) of MTBE in volunteers exposed to concentrations ranging from 5 to 75 ppm is around 40%, while pulmonary retention of ETBE over an exposure range of 5 to 50 ppm is about 26% [35]. About 7-9% of the inhaled MTBE is reversibly taken up by the mucous membranes of the upper airways [31]. The internal dose calculated from the area under the inhaled air concentration and alveolar breath concentration curves, after inhalation exposure to 1.7 ppm for 15 min [26], averaged 197 50 pg for all subjects (about 3.86 pg/kg bw). 

Human evolution has taken place close to sea level, and humans are physiologically adjusted to the absolute partial pressure of the oxygen at that point, namely 21.2 kPa (159.2 mm Hg), ie, 20.946% of 101.325 kPa (760 mm Hg). However, humans may become acclimatized to life and work at altitudes as high as 2500—4000 m. At the 3000-m level, the atmospheric pressure drops to 70 kPa (523 mm Hg) and the oxygen partial pressure to 14.61 kPa (110 mm Hg), only slightly above the 13.73 kPa (102.9 mm Hg) for the normal oxygen pressure in alveolar air. To compensate, the individual is forced to breathe much more rapidly to increase the ratio of new air to old in the lung mixture. 

TABLE 5.6 Effect of Dead Space Volume, Tidal Volume, and Breathing Frequency on Alveolar >fentllation at a Fixed Minute Ventilation (V = 58.0 Umin). Modified from Chemiack. ... 

Certain characteristics of the developing human may increase exposure or susceptibility while others may decrease susceptibility to the same chemical. For example, although infants breathe more air per kilogram of body weight than adults breathe, this difference might be somewhat counterbalanced by their alveoli being less developed, which results in a disproportionately smaller surface area for alveolar absorption (NRC 1993). 

Alveolar pressure (Palv) is the pressure within the alveoli. In between breaths, it is equal to 0 cmH20. Because no pressure gradient exists between the atmosphere and the alveoli, there is no airflow. However, in order for air to flow into the lungs, alveolar pressure must fall below atmospheric pressure. In other words, alveolar pressure becomes slightly negative. According to Boyle s law, at a constant temperature, the volume of a gas and its pressure are inversely related ... 

Pulmonary surfactant decreases surface tension of alveolar fluid. Reduced surface tension leads to a decrease in the collapsing pressure of the alveoli, an increase in pulmonary compliance (less elastic recoil), and a decrease in the work required to inflate the lungs with each breath. Also, pulmonary surfactant promotes the stability of the alveoli. Because the surface tension is reduced, the tendency for small alveoli to empty into larger ones is decreased (see Figure 17.2, panel b). Finally, surfactant inhibits the transudation cf fluid out of the pulmonary capillaries into the alveoli. Excessive surface tension would tend to reduce the hydrostatic pressure in the tissue outside the capillaries. As a result, capillary filtration would be promoted. The movement of water out of the capillaries may result in interstitial edema formation and excess fluid in the alveoli. 

During exercise, the increase in minute ventilation results from increases in tidal volume and breathing frequency. Initially, the increase in tidal volume is greater than the increase in breathing frequency. As discussed earlier in this chapter, increases in tidal volume increase alveolar ventilation more effectively. Subsequently, however, as metabolic acidosis develops, the increase in breathing frequency predominates. 

Pulmonary i Respiratory muscle strength i Chest wall compliance i Total alveolar surface i Vital capacity i Maximal breathing capacity... 

Breath (alveolar air) Collection in glass tube cap. GC/MSD Not reported Not reported Brugnone et al. 1991... 

The patient takes a single vital capacity breath of 02 and exhales through a N2 analyser. Dead space gas, which is pure 02, passes the analyser first, followed by a mixture of dead space and alveolar gas. When pure alveolar gas passes the analyser, a plateau is reached. At closing capacity, small airways begin to close, leading to preferential exhalation from the larger-diameter upper airways. These airways contain more N2 as they are less well ventilated, so the initial concentration of N2 within them was not diluted with 02 during the 02 breath. 

Alveolar air Collection of exhaled air using a specially-designed device to provide pure air for inhalation. Breath collected into duplicate evacuated canisters. GC/MS 0.5 pg/m (0.5 ppt, w/v) 112 (8% RSD) at 5.1 pg/m Raymer et al. 1990... 

Pleil JD, Lindstrom AB. 1995. Collection of a single alveolar exhaled breath for volatile organic compounds analysis. Am J Ind Med 28(1) 109-121. 

Because of the complexity of the actual structures, the emphasis in modeling has been on obtaining an average representation, and the variability among individuals tends to be neglected. There are two experimental studies of variability of airway dimensions in living humans as revealed by aerosol-deposition studies. Lapp et al. assessed the size of alveolar spaces in terms of half-life of aerosol persistence during breath-... 

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