Respiratory cycles

Concentration-related increases in respiratory resistance, together with prolonged and deepened respiratory cycles... 

Schaper, M., Detwiler, K. and Alarie, Y. (1989). Alteration of respiratory cycle timing by propranolol. Toxicol. Appl. Pharmacol. 97 538-547. 

The power required to sustain physiological processes can be calculated by using the above equation. If a pressure-volume loop for a respiratory cycle is plotted, the work of breathing may be found. If the respiratory rate is now measured then the power may be calculated. The power required for respiration is only approximately 700-1000 mW, compared with approximately 80 W needed at basal metabolic rate. 

In this example, the respiratory rate has increased so that each respiratory cycle only takes 3 s. As a consequence the Petco2 has fallen to approx 2.5 kPa. 

The respiratory rate is reduced such that each complete respiratory cycle takes longer. This is usually a result of a prolonged expiratory phase, so it is the plateau that you should demonstrate to be extended. The Petco2 will be raised as a consequence. 

The compliance of the lung measured during the respiratory cycle when gas flow is still ongoing (ml.cmH20 1 or l.kPa-1)... 

PAOP This must be lower than the PA diastolic pressure to ensure forward flow. It is drawn as an undulating waveform similar to the CVP trace. The normal value is 6-12 mmHg. The values vary with the respiratory cycle and are read at the end of expiration. In spontaneously ventilating patients, this will be the highest reading and in mechanically ventilated patients, it will be the lowest. The PAOP is found at an insertion length of around 45 cm. 

During the respiratory cycle, the volumetric flow rate of air varies from zero up to a maximum and back. Usually, the expiratory phase is longer than the inspiratory phase, and there may be intervening pauses... 

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. 

D.O. Kuethe, V.C. Behr, S. Begay, Volume of rat lungs measured throughout the respiratory cycle using F-19 NMRof the inert gas SFe, Magn. Reson. Med. 48 (2002) 547-549. 

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. 

Figure 7.10 shows the percentage deposition of the exhaust aerosol in the lung as a function of the length of the respiratory cycle (Chamberlain etal., 1978). Eight volunteers inhaled the aerosols. Tidal volumes ranged from 0.3 to 2.31. Individual results showed a coefficient of variation of 20% relative to the curves of Fig. 7.10. In the experiments with the wind-tunnel aerosols (0.02,0.04 and 0.09 m) there was no significant effect of tidal volume on the percentage deposition.

Solubilization, uptake, and precipitation of Ca and Si are directly (or at least energetically) linked to the photosynthetic and respiratory cycling of C, H, and O. Acids from nitrification and sulfur oxidation aid phosphorus mobilization photosynthesis or respiration is required for the uptake and conversion of phosphorous into high-energy phosphate. Sulfur is oxidized (with the concomitant reduction of nitrate) by Thiobacillus denitrificans, likewise, some extremely thermophilic methanogens can transfer hydrogen not only to CO2, but also to S. These are a few examples of interrelations involved in biogeochemical cycles. 

In addition to being important in industry, transition metal ions play a vital role in living organisms. For example, complexes of iron provide for the transport and storage of oxygen, molybdenum and iron compounds are catalysts in nitrogen fixation, zinc is found in more than 150 biomolecules in humans, copper and iron play a crucial role in the respiratory cycle, and cobalt is found in essential biomolecules such as vitamin Bi2-... 

Various tiny structures, so-called organelles, are embedded in the cytoplasm where they make numerous cell functions possible, (s. fig. 2.9) (s. tab. 2.1) The enzyme-rich mitochondria have an outer and an inner membrane, with the latter forming creases (cristae). The outer membrane is relatively permeable for small molecules. However, the inner membrane (which surrounds the matrix) must use specific transport proteins to enable protons, calcium, phosphate and so on to pass. Energy-rich substrates are transformed into ATP in the mitochondria. The enzymes which are responsible for fatty-acid degradation and the citric-acid cycle can be found in the matrix. The inner membrane also contains the enzymes of the so-called respiratory cycle. An enormous number of energy-providing reactions and metabolic processes take effect at this site. They have a round-to-oval shape with a diameter of about 1 im. There are 1,400-2,200 mitochondria per liver cell (18-22% of the liver cell volume). They generally lie in... 

Opioids are potent respiratory depressants, causing a dose-dependent decrease in respiratory frequency, tidal volume and minute ventilation and increased arterial partial pressure of carbon dioxide (PaC02) (Carvey 1998). Opioids depress chemosensors in the brainstem, decreasing the ventilatory response to carbon dioxide. Opioids also depress rhythmicity in the dorsal respiratory group in the nucleus tractus solitarius, attenuating the respiratory cycle. Opioids, however, do not diminish hypoxic ventilatory drive. Significant elevations in Paco2 can result in increased ICP after opioid administration. 

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