5. Predicted respiratory pH

The predicted respiratory pH is usually calculated by pCO2 variance. This calculation is slightly different for higher (>40 mmHg) and lower (<40 mmHg) pCO2

Figure 11. X-axis predicted respiratory pH vs. y-axis [NRH]/{[40]\*[H]}.

levels. The difference between the predicted respiratory pH and the measured pH reflects the metabolic pH change. [15] The predicted respiratory pH is calculated by using a newly derived formula which is common for all pCO2 values [18]. The graphical relationship is shown in Figures 11–13 and tabulated

The postulates of the acid-base balance theory are listed below [14]:

1.The net changes in pH of the blood reflect the sum total changes in the

[ΔpH (pH 7.4)] are due to both the changes in respiratory [ΔRpH (pH NRpH)] and non-respiratory (metabolic) components [ΔNRpH

2.The sum total changes in the hydrogen ion concentration (ΔH + = [H+

the blood include both the changes due to respiratory (ΔRH+ = [H+

a given standard bicarbonate concentration represented by the relation

4.The concentration of hydrogen ion excess given by [NRH<sup>+</sup> 40] is directly proportional to the base deficit. This quantity with opposite sign [40 NRH<sup>+</sup>

is directly proportional to the base excess. Standard base excess is the base

component are due to the changes by the independent variables, namely, strong ion difference (SID) and the total concentration of weak nonvolatile

6.The changes in the dependent variable [HCO3] are a marker of metabolic acid-

7.The magnitude and direction (positive or negative) of the changes in the parameter ΔNRpH(NRpH 7.4) are due to the accumulation of acids other than carbonic acid or bases. The value is negative for acidic effect and positive

8.The magnitude and direction (positive or negative) of the changes in the parameter ΔRpH(pH NRpH) denote the respiratory influence in causing changes in pH represented by the relation pH NRpH = 1.6 + log{(HCO3/Std HCO3)/pCO2}. The value is negative for acidic effect and positive for alkaline

(pH NRpH) which denotes the respiratory influence of pCO2.

] representing the non-respiratory (metabolic)

] is directly proportional to the parameter ΔRpH

5.The changes in the dependent variable non-respiratory hydrogen ion

and non-respiratory (metabolic) components (ΔNRH+ = [NRH+

3.The non-respiratory hydrogen ion concentration [NRH<sup>+</sup>

excess at hemoglobin concentration of 5 g/dl.

acids, namely, albumin and phosphate [ATOT].

base disturbances and not its causative mechanism.

hydrogen ion concentration in the blood. The net changes in total or actual pH

] [40]) in

])

]

] [NRH+

] [40]).

] has a unique value for

6. Postulates of the acid-base balance theory

(NRpH 7.4)] affecting the pH.

Who Is Balancing: Is It RBC or Acid-Base Status? DOI: http://dx.doi.org/10.5772/intechopen.84768

NRH<sup>+</sup> = 960/Std bicarbonate.

concentration [NRH+

for alkaline effect.

effect.

45

9.The ratio [NRH<sup>+</sup>

/H<sup>+</sup>

in Table 2.

Figure 12. X-axis predicted respiratory pH vs. y-axis pCO2.

#### Figure 13.

X-axis predicted respiratory pH(Pr RpH) calculated by newer formulae vs. y-axis Pr RpH calculated using pCO2 variance.


#### Table 2.

Comparison of predicted respiratory pH calculation (one by previous method using pCO2 variance and the other by newly derived formulae).

Who Is Balancing: Is It RBC or Acid-Base Status? DOI: http://dx.doi.org/10.5772/intechopen.84768

levels. The difference between the predicted respiratory pH and the measured pH reflects the metabolic pH change. [15] The predicted respiratory pH is calculated by using a newly derived formula which is common for all pCO2 values [18]. The graphical relationship is shown in Figures 11–13 and tabulated in Table 2.
