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Lungs breathing mechanics

Adult cats of either sex are anesthetized with a-chloralose, 80 mg/kg, and pentobarbital 7 mg/kg, given intraperitoneally. Cannulas are placed in the left femoral vein and artery for drug injection and recording blood pressure and heart rate. The lungs are mechanically ventilated through a tracheostomy and a small animal ventilator set to deliver 15 ml/kg tidal volume and 20 breaths/min. [Pg.208]

Respiratory failure following exposure to toxic chemical agents has two causes. The first is the failure of oxygen to be able to difluse across the walls of the alveoli into the pulmonary capillaries and thus into the arteries and cells. The second is the failure of the breathing mechanism to move gas in and out of the lungs leading to a build-up of carbon dioxide in the alveoli. These conditions are known as types 1 and 2 respiratory failure. It should be noted that type 2 respiratory failure has a shorter latency that type 1. [Pg.106]

Inhaled gaseous compounds are absorbed in all parts of the respiratory system whereas particle size determines how deep into the airways the parti cles will he transported in the airstrearn. Shortness of breath is a typical sign of a chemical exposure that has affected the lungs, and it may be evoked through iminunological mechanisms (e.g., formaldehyde, ethyleneoxide), or through toxic irritation (formaldehyde, isocyanates, sulfur dioxide, nitrogen dioxide, Frequently the mechanism depends on the concentration ol the com... [Pg.294]

Most textbooks in the 1960s suggested that deaths from belladonnoid dmgs were likewise due to central respiratory failure, even though there were insufficient empirical data to confirm this conclusion. To the contrary, a review of lethal studies of BZ in rats indicated that cardiac, rather than respiratory, failure caused death. Unlike morphine, BZ disturbs the heartbeat not the ability to breathe. The ability of the rat (or human) beating heart to mechanically ventilate the lungs, therefore, does not apply to BZ. [Pg.134]

There is evidence that ozone has a delayed effect on elastic behavior. Excised lungs of rabbits that were unilaterally exposed to ozone at 1.0 ppm for 3 h and then allowed to breathe ambient air for up to 2 weeks showed a depression in the volume-pressure curves. This change was present during most of the postexposure test period. The mechanism underlying this response was not determined. ... [Pg.334]

The clinical aspects of asbestosis are well defined and predictable. First, the lung tissue changes to scar tissue as inflammation, initiated by the cells normally in the tissue or air spaces, is expressed as an increase of inelastic collagen. The fibrosed or scar tissue renders the lung tissue stiff and narrows the airways. Mechanical constraints become obvious as the patient expends more effort to breathe. [Pg.126]

In this equation, the diffusion coefficient D is related to air viscosity r A and particle diameter dp, with k being the Boltzmann constant and T the absolute temperature. It is clear from this description that diffusion is a rather slow deposition mechanism compared with impaction and sedimentation processes because it depends on the thermal velocity of the particles and not on airflow. It is the primary transport mechanism for small particles and is important when the transport distance becomes small, as in the deep lung. Efficiency of this deposition mechanism can be increased significantly by breath-holding because a portion of the ultrafine particles that are not deposited will be exhaled by the patient. [Pg.238]

In the pulmonary region, air velocities are too low to impact particles small enough to reach that region, and the mechanisms of deposition are sedimentation and Brownian diffusion. The efficiency of both processes depends on the length of the respiratory cycle, which determines the stay time in the lung. If the cycle is 15 breaths/min, the stay time is of the order of a second. Table 7.1 shows the distance fallen in one second and the root mean square distance travelled by Brownian diffusion in one second by unit density particles (Fuchs, 1964). Sedimentation velocity is proportional to particle density, but Brownian motion is independent of density. Table 7.1 shows that sedimentation of unit density particles is more effective in causing deposition than Brownian diffusion when dp exceeds 1 pm, whereas the reverse is true if dp is less than 0.5 pm. For this reason, it is appropriate to use the aerodynamic diameter dA equal to pj dp when this exceeds 1 pm, but the actual diameter for submicrometre particles. [Pg.232]


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