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<> The direct effect of the external respiratory dysfunction caused by thediv class" "clear" >
is the change of blood gas, i.e. paO2 decreases or is accompanied by a increase or decrease in PaCO2 The most important causes of changes in the functions of the various systems of respiratory failure are hypoxemia, high carbonateemia, andbalance disorders. The effects of hypoxemia and hypocarbonemia on the body depend on the urgency, degree, longer and metabolism of the body's original function. In the course of onset, especially in patients with chronic respiratory failure with delayed course of illness, a series of compensation adaptation reactions often occur, which can improve the oxygen supply oftissue and regulate acid-base balance, or change the function metabolism of tissue organs to adapt to the new environment. In severe cases, organs outside the respiratory system can also develop dysfunction and even become a direct cause of death.
1, gas metabolic changes
breathing failure must have changes in blood gas, sometimes due to the cover-up of primary disease, respiratory failure itself caused by clinical manifestations can not be obvious, but according to changes in blood gas can be judged whether respiratory failure occurred. Due to the differences in lesions, properties and degrees, as well as the body's reactivity and compensation function, changes in blood gas during respiratory failure can vary from one to the next, with the following four types:
(i) PaO 2 decline PaCO 2 rise, the two in a proportional relationship
"tt1" > all kinds of reasons as long as the cause of total vesicles breathing Insufficient amount, will make the bubble oxygen pressure (PAo2) drop and the bubble gas carbon dioxide pressure (PAco2) increased, the blood flowing through the veins of the veins of the veins can not be fully arterialized, and thus inevitably lead to (Pao2) reduction and PA2
(ii PaO2
down while Paco 2 little change< p class "tt1" > changes in this blood gas It can be seen in the following cases:1. When the proportion of the decompression of the pulmonary function is increased, the venous blood flowing through here is not fully arterialized, so oxygen pressure reduces the carbon dioxide sub-pressure increase. Because Paco2 elevates the stimulating central chemical receptor and PaO2 reduces the p Ao2 increased and PAco2 decreased, blood flow through these bubbles, its oxygen pressure will also increase, carbon dioxide pressure will inevitably decrease. Mixed pulmonary vein blood is often eventually lower than normal oxygen pressure, while carbon dioxide pressure is normal or slightly reduced. When the dead cavity-like breathing increases, the blood in the lesions area can be fully oxygenated, but the gas is wasted, the rest of the albath will be relatively short of breath, and therefore there is also an increase in functional severity, the change of blood gas is PaO2 and PaCO2 change is small (Figure 13-4C).
< p-align"">Figure 13-5 Blood CO2 dissocation curve
| 2.67 | < "50%" >20"
Patients with restrictive breathing disorders caused by reduced lung compliance, breathing is often accelerated, Total air intake can be increased. At the same time, because the lesions are not uniform, there is also an imbalance in the proportion of the air flow of the vesicles, so the body's carbon dioxide recoverable discharge increased, its blood gas changes are often Pao 2 decline, and Paco 2 unchanged or slightly lower.
< hypoxia caused by increased functional section and increased cavity-like breathing in >p class-"tt1" can be alleviated by inhalation of high concentration oxygen therapy. Short circuits in the lungs can also cause changes in blood gas similar to functional section, but inhalation of high concentrations of oxygen can not change hypoxia.2. When the area of the diaphragm vesicle membrane is reduced, the thickness increases or the permeability decreases, in addition to the hypoxemia caused by the simultaneous imbalance of the proportion of the air flow of the anostobumin, in severe cases itself may also cause paO2 to be blocked by oxygen dispersion from the to the blood However, because carbon dioxide dispersion capacity is very strong (about 20 times greater than oxygen) its discharge is less affected, so PaCO 2 more normal, and even because of excessive inspensive breathing and decline. Inhalation of high concentrations of oxygen in such patients can also relieve hypoxic blood pressure.
< p class" "tt1" > dispersion disorder and the imbalance of the ratio of the air flow of the veleculation of the vesicles can not be carried out effectively, so the difference between Pao2 below PAo2 PAo2 and Pao2 is a common feature.(iii paO2 decrease, Paco 2 increase, the change between the two is not proportional
< p class "tt1" > this blood gas Changes can be seen in the following conditions:1. The limiting of the lack of thoracic compliance caused by the reduction of the lesions of the chest is often even, so the pathogenesis of respiratory failure at this time, not only the lack of air ventilation, but also the proportion of the ratio of the air flow of the vesicles. At this time, the lesions of the chest limit the breathing response, so that it can not be fully strengthened, carbon dioxide although part of the recoverable discharge, but not enough, so the change of blood gas for Pao 2 decreased, PaCO 2 increased, but the changes between the two are not consistent proportion of the relationship, of which Pao 2 decline is more serious (Figure 13-4B).
Figure 13-6 abbulmonary breathing and abas bubble PO2, Pco2
< Center " class" "tt3" > the relationship between arterial oxygen saturation and arterial blood pHtt1" >2. Chronic obstructive pulmonary disease due to the external small valve obstruction and other lesions are not uniform at this time, so the proportion of albathic gas flow is obviously out of balance. This is an important mechanism for abnormal blood gas. In addition to the changes in blood gas that can manifest them as Pao2 reducing Paco2 unchanged, in some patients may be due to the central nervous system reaction to reduce the response to enhanced breathing, so it is not only Pao The 2 is lower, and paco 2 rises early on, but Paco 2 changes less than Pao2 changes, the two are not a fixed proportion of the relationship. These patients with chronic respiratory failure have reduced the effect of CO2-enhanced breathing due to the imbalance in the proportion of 2 until the CO2 produced per minute is entirely ventilated Good depulent discharge, in turn, can make carbon dioxide production and discharge at the high Paco 2 level to achieve a new balance, so Paco 2 can be maintained at a higher level for a longer period of time, patients can continue to survive.
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