45 research outputs found
A mathematical model for breath gas analysis of volatile organic compounds with special emphasis on acetone
Recommended standardized procedures for determining exhaled lower respiratory
nitric oxide and nasal nitric oxide have been developed by task forces of the
European Respiratory Society and the American Thoracic Society. These
recommendations have paved the way for the measurement of nitric oxide to
become a diagnostic tool for specific clinical applications. It would be
desirable to develop similar guidelines for the sampling of other trace gases
in exhaled breath, especially volatile organic compounds (VOCs) which reflect
ongoing metabolism. The concentrations of water-soluble, blood-borne substances
in exhaled breath are influenced by: (i) breathing patterns affecting gas
exchange in the conducting airways; (ii) the concentrations in the
tracheo-bronchial lining fluid; (iii) the alveolar and systemic concentrations
of the compound. The classical Farhi equation takes only the alveolar
concentrations into account. Real-time measurements of acetone in end-tidal
breath under an ergometer challenge show characteristics which cannot be
explained within the Farhi setting. Here we develop a compartment model that
reliably captures these profiles and is capable of relating breath to the
systemic concentrations of acetone. By comparison with experimental data it is
inferred that the major part of variability in breath acetone concentrations
(e.g., in response to moderate exercise or altered breathing patterns) can be
attributed to airway gas exchange, with minimal changes of the underlying blood
and tissue concentrations. Moreover, it is deduced that measured end-tidal
breath concentrations of acetone determined during resting conditions and free
breathing will be rather poor indicators for endogenous levels. Particularly,
the current formulation includes the classical Farhi and the Scheid series
inhomogeneity model as special limiting cases.Comment: 38 page
Reduced Exercise Tolerance and Pulmonary Capillary Recruitment with Remote Secondhand Smoke Exposure
RATIONALE: Flight attendants who worked on commercial aircraft before the smoking ban in flights (pre-ban FAs) were exposed to high levels of secondhand smoke (SHS). We previously showed never-smoking pre-ban FAs to have reduced diffusing capacity (Dco) at rest. METHODS: To determine whether pre-ban FAs increase their Dco and pulmonary blood flow (Qc) during exercise, we administered a symptom-limited supine-posture progressively increasing cycle exercise test to determine the maximum work (watts) and oxygen uptake (VO2) achieved by FAs. After 30 min rest, we then measured Dco and Qc at 20, 40, 60, and 80 percent of maximum observed work. RESULTS: The FAs with abnormal resting Dco achieved a lower level of maximum predicted work and VO2 compared to those with normal resting Dco (mean±SEM; 88.7±2.9 vs. 102.5±3.1%predicted VO2; p = 0.001). Exercise limitation was associated with the FAs' FEV(1) (r = 0.33; p = 0.003). The Dco increased less with exercise in those with abnormal resting Dco (mean±SEM: 1.36±0.16 vs. 1.90±0.16 ml/min/mmHg per 20% increase in predicted watts; p = 0.020), and amongst all FAs, the increase with exercise seemed to be incrementally lower in those with lower resting Dco. Exercise-induced increase in Qc was not different in the two groups. However, the FAs with abnormal resting Dco had less augmentation of their Dco with increase in Qc during exercise (mean±SEM: 0.93±0.06 vs. 1.47±0.09 ml/min/mmHg per L/min; p<0.0001). The Dco during exercise was inversely associated with years of exposure to SHS in those FAs with ≥10 years of pre-ban experience (r = -0.32; p = 0.032). CONCLUSIONS: This cohort of never-smoking FAs with SHS exposure showed exercise limitation based on their resting Dco. Those with lower resting Dco had reduced pulmonary capillary recruitment. Exposure to SHS in the aircraft cabin seemed to be a predictor for lower Dco during exercise
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Growth rate measurements and deposition modelling of hygroscopic aerosols in human tracheobronchial models.
A laboratory system has been developed in which the atmosphere and fluid dynamics of the upper tracheobronchial (TB) tree of the human are simulated. It is used to measure the hygroscopic growth rates of monodisperse NaCl and bronchodilator (Isuprel® hydrochloride with and without glycerine) aerosols. Dry particles are mixed with water vapour-laden air at the entrance to a growth chamber temperature controlled at 37°C with a relative humidity (RH) between 88 and 95%. Hygroscopic growth rates increased with degree of RH and magnitude of Reynolds number in the chamber. The growth data are incorporated into an aerosol deposition model to calculate the effect of hygroscopic growth upon the dose distribution of medicinal aerosols in the human TB network. The model uses some original deposition formulae to compute particle deposition efficiencies. Calculations show that the rate of water vapour absorption within TB airways is an important factor affecting the fate of particles used in aerosol therapy. © 1982 British Occupational Hygiene Society
Recommended from our members
Growth rate measurements and deposition modelling of hygroscopic aerosols in human tracheobronchial models.
A laboratory system has been developed in which the atmosphere and fluid dynamics of the upper tracheobronchial (TB) tree of the human are simulated. It is used to measure the hygroscopic growth rates of monodisperse NaCl and bronchodilator (Isuprel® hydrochloride with and without glycerine) aerosols. Dry particles are mixed with water vapour-laden air at the entrance to a growth chamber temperature controlled at 37°C with a relative humidity (RH) between 88 and 95%. Hygroscopic growth rates increased with degree of RH and magnitude of Reynolds number in the chamber. The growth data are incorporated into an aerosol deposition model to calculate the effect of hygroscopic growth upon the dose distribution of medicinal aerosols in the human TB network. The model uses some original deposition formulae to compute particle deposition efficiencies. Calculations show that the rate of water vapour absorption within TB airways is an important factor affecting the fate of particles used in aerosol therapy. © 1982 British Occupational Hygiene Society