Certainly for many decades the topic was presented in a study of the profane so complex and often difficult to deter even the most willing.
The introduction of the "log" and "PK" in the equation of Henderson-Hasselbach confuses and frightens anyone who has not already familiar with these parameters, so as to discourage any kind of approach. In clinical practice every day and especially in the context of the urgent need for some aspettisemplicistico approach, however, proper and immediate.
The human body, due to its metabolism produces acids continuously, and indeed many foods and beverages that commonly use are harbingers of acids, and thus hydrogen ions (H +), even the solution "physiological" is highly acidic!.
. The body defends itself against changes in concentration of hydrogen ions with the systems 'buffer', which, even if immediate intervention, constitute a limited source and drain (about 2400mMoli). The lungs are involved in a few minutes, the kidneys within several hours and complete their intervention only after two or three days. The normal pH is between 7.40 and 7.35 and 7.45, below these values \u200b\u200bgo to acidemia, above in alcalemia. Values \u200b\u200bthat exceed or fall below 7.80 to 6.80 represent a danger "deadly".
the pH is essentially the ratio between the activity the kidney and activity of the lung (pH = pK + log [HCO3-] / [H2CO3]) or between the metabolic component (slow) and the respiratory component (fast). In fact, the H2CO3 is nothing more than CO2 dissolved in water.
But if we take the first glimpse of Henderson, dating back to 1909, we see how it turns out to be a lot easier because instead of pH takes into account the concentration of hydrogen ions, which in fact constitutes the real problem: [H +] = K x [H2CO3] / [HCO3-], the higher the [H +], the higher the acidity the lower the [H +] less acidity. The relationship between [H +] and acidity diventadiretto and linear. The concentration of hydrogen ions, and hence the degree of acidity of a solution depends on the relationship between lung function and the metabolic CO2/HCO3-. This concept is perhaps more immediate. In fact, more CO2 is retained, the higher the [H +] and consequently the acidemia.
as an approach to reading selfish?
A reading called "stage" may be just the right way to unapproccio simple, fast and comprehensive.
At The step we find the O2
the first step we find the partial pressure of oxygen (PaO2). It 's the first information to be found because people die of hypoxia in quickly and because it can explain some of the acid-base disorders. Also helps us determine in a short time, as mentioned above, a value of relative security that is represented by a PaO2 above 60 mmHg. Also we can derive important information about the patient's gas exchange by calculating P / F (PaO2/FiO2) and D (Aa) O2. The
P / F in normal subjects breathing room air is higher than 450, is an indicator of rapid, but effective, and cosolidato literature, intrapulmonary gas exchange. It fact, comparing the FIO2, the percentage of oxygen inhaled by the patient, the response in terms of PaO2, it highlights the magnitude of the intrapulmonary shunt. Similarly, and for the same reasons,
this index can be used to monitor the efficacy of ventilation and the patient's response to it: a PaO2 of 90 mmHg may be quite normal in a patient breathing room air, but indicates an exchange intrapulmonary totally inadequate if the patient is assisted with a high FiO2.
The formula for calculating the D (Aa) O2 is as follows: [(760-47) x FIO2] - (PaCO 2 / 0.8) - PaO2. In the patient breathing room air in the above formula can be simplified as: 150 - (PaCO 2 / 0.8) - PaO2, and roughly corresponds the mnemonic: (age: 4) + 4. The normal value of this index in ambient air of10-15; values \u200b\u200babove 20 indicate the existence of a trade deficit of intrapulmonary O2, while values \u200b\u200babove 50 are suggestive of severe pulmonary dysfunction. The use of this index does not enjoy the same evidence in the literature of the P / F, but including the factor in the calculation PaCO2,
can be a useful aid in the initial screening of those situations, such as pulmonary embolism, which is accompanied to its reduction. It becomes less reliable, however, where co-occurs hypercapnia.
In step II we find the pH
It would all be linear if we found the concentration of hydrogen ions, but for now we provide the equipment and therefore the pH must be able to interpret this parameter. The pH tells us immediately if our pc has a acidemia or a alcalemia and is certainly the strongest indicator of the state of gravity of our pieces. Reading it provides us with no difficulty to define the primitive nature of the disorder.
In step III we find the
PaCO2 PaCO2 level allows us to:
1.di understand what and how our pc fan (since PaCO2 and ventilation are inversely related);
2. readily define if the primary disorder (head of acidemia or alcalemia)
is or is not breathing (respiratory acidosis or alkalosis).
In step IV are bicarbonate (HCO3-)
quantify the alkaline reserve means to better define the primitive type of disorder, if the PaCO2 is not found diriment (metabolic acidosis or alkalosis). But it is only integration of the two figures (PaCO2 and HCO3-) which allows us to salirel'ultimo rung of our ladder.
0 comments:
Post a Comment