Gas exchange, in lungs

According to Pick s law of diffusion, the amount of gas that moves across the blood-gas interface is proportional to the surface area of the interface and inversely proportional to thickness of the interface. In other words, gas exchange in the lungs is promoted when the surface area for diffusion is... 

Lin, K. H., and G. Gumming. A model of time-varying gas exchange in the human lung during a respiratory cycle at rest. Respir. Physiol. 17 93-112, 1973. 

Q5 Restrictive lung disease reduces lung capacity and results in rapid, shallow breathing. This type of respiration tends to wash C02 out of the lung and may result in an increase in blood pH. Gas exchange in alveoli is reduced or inadequate because of the poor expansion of lung tissue, so the arterial P02 of arterial blood may also be rather low. 

Figure 2.4. Schematic of gas exchange in the human lung. The distance for diffusion is a mere 20 pm. The total surface area available for exchange is about 80 m. Exchange of oxygen, CO2 and dmg gases such as narcotics is therefore very fast.

Fedde, M.R., Dodd, D.E., Troup, C.M., Fowler, E.H. (1987). Biological effects of short-term, high-concentration exposure to methyl isocyanate. III. Influence on gas exchange in the guinea pig lung. Environ. Health Perspect. 72 29-33. 

Depending on the physicochemical natme of the toxic gas or aerosol, absorption will take place at different areas of the respiratory tract. Apart from the chemical properties the size of particles and aerosols will also affect the targeted area. Materials with diameters less than 2 pm will reach the alveoli whereas larger ones (about 20 pm in diameter) are retained in the upper respiratory areas of throat and bronchi thus protecting gas exchange in the lung. 

Bratel T, Hedenstierna G, Nyquist O, Ripe E. The effect of a new calcium antagonist, felodipine, on pulmonary hypertension and gas exchange in chronic obstructive lung disease. Eur J Respir Dis 1985 67(4) 244-53. 

Most of the symptoms produced by phosgene poisoning occur as a consequence of damage to the lung and its associated structures. Man s respiratory system is highly specialized for gas exchange in air. The internal surfaces of the system are brought into contact with the air via the respiratory tract and the operation of a tidal ventilation mechanism (see Fig. 2.1). 

Without pulmonary surfactant, gas exchange in the lungs is very poor. Pulmonary surfactant is not produced until early in the sixth month of pregnancy. Premature babies born before they have begun secretion of natural surfactant suffer from respiratory distress syndrome (RDS), which is caused by the severe difficulty they have obtaining enough oxygen from the air that they breathe. 

Intensive care aims at the replacement or support of deficient central functions. Important functions are respiration and a sufficient cardiac and circulation function. Monitoring the gas exchange in intensive care especially of ventilated patients requires, in addition to gas analysis at several measuring sites in the body, information on the heart function, eg, heart rate, on the pressure of the circulation system, eg, arterial pressure, and on the actual utilization of the available amount of oxygen. With regard to the methods required to achieve information that is as complete as possible, the clinical task consists in the determination of gas concentrations or partial pressures in the gas phase of the lung, airways, and equipment hoses, in the transportation system of the blood, and in the tissue. In recent years there has been an increasing importance of non-invasive methods, as invasive procedures are combined with risk and additional stress for the patient. 

Pulmonary and Peripheral Gas Exchange in Health and Disease, edited by J. Roca, R. Rodriguez-Roisen, and P. D. Wagner Lung Surfactants Basic Science and Clinical Applications, R. H. Natter Nosocomial Pneumonia, edited by W. R. Jarvis Fetal Origins of Cardiovascular and Lung Disease, edited by David J. P. Barker... 

West, J. 1962. Regional differences in gas exchange in the lung of erect man. /. Appl. Physiol. 17 893-898. West, J.B. (Ed.) 1977. Bioengineering Aspects of the Lung. New York, Marcel Dekker. 

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