Effect of volume history on measurements of respiratory mechanics using the interrupter technique

The importance of the viscoelastic properties of the tissues of the respiratory system has recently been recognized, and lung models have been produced to describe the resistive and viscoelastic properties of the lung. The pulmonary mechanics of 10 rabbits were studied using the interrupter technique to assess the effect of volume history on the resistive and viscoelastic elements of the respiratory system. The influence of the tone of the muscles of respiration was also studied. In healthy lungs, the resistive and viscoelastic elements of the lung are dependent on the volume history of the respiratory system and are significantly lower if these elements do not reach a resting position before expiration. The chest wall made a significant contribution to the resistive and viscoelastic elements of the respiratory system, which was also dependent on the lung volume history. The tone of the muscles of respiration had no effect on the resistive or viscoelastic elements of the respiratory system

Effect of pulmonary blood flow on measurements of respiratory mechanics using the interrupter technique

The relationship between respiratory mechanics, changes in pulmonary blood flow (PBF), pulmonary arterial pressure, and left atrial pressure is unclear. Conventional methods for the measurement of respiratory mechanics model the respiratory system as a single compartment, which may not adequately represent the respiratory system in a diseased state. The interrupter technique models the respiratory system as two compartments, with the 'flow resistance' of the conducting airways and chest wall (Raw) considered separately from Pdif, a measure of the viscoelastic properties of the lung and chest wall, together with any pendelluft present. The respiratory mechanics of 15 infants in the first year of life were studied during cardiac catheterization with the use of conventional methods and the interrupter technique. The infants had a PBF-to-systemic blood flow ratio ranging from 0.6 to 4.0:1. The specific dynamic compliance of the respiratory system was not related to the PBF; however, there was a significant relationship between PBF and the total resistance of the respiratory system (Rrs) [analysis of variance (ANOVA) F = 5.69, P < 0.05], Raw (ANOVA F = 12.30, P < 0.01), and Pdif (ANOVA, F = 3.79, P < 0.05). Rrs increased significantly with an increase in mean left atrial pressure (ANOVA F = 6.92, P < 0.05); however, dynamic compliance, Raw, and Pdif did not. These results suggest that the relationship between Rrs and PBF is due an increase in the resistive properties of the conducting airways and tissue components

Exercise-Induced Asthma: An Update

Exercise-induced asthma (E.I.A) affects 12–16% of the general population and most of the patients affected by extrinsic or intrinsic asthma. Surprisingly, also a high percentage of professional and Olympic athletes are affected, showing that E.I.A. does not impair physical activity, whereas endurance sports bear a higher risk than the others. The mast cell role, late asthmatic responses, diagnosis, therapy, theories and data about immunological parameters in sports are taken into consideration in this review