Comparison of Measured and Calculated Bicarbonate Values

Diagnostic Predictors of Obesity-Hypoventilation Syndrome in Patients Suspected of Having Sleep Disordered Breathing

“…10,[19][20][21] Although gold standard for diagnosis of OHS remains raised arterial pCO 2 , an increase in the bicarbonate level due to metabolic compensation of respiratory acidosis has been found to be a sensitive screening tool for daytime hypercapnia. 7,27 In our study, bicarbonate level was calculated from the CBG data using arterial pH and pCO 2 28 In our study using logistic regression with various thresholds for HCO 3 , a cutoff value of 27 mmol/L had the highest sensitivity (85.7%) and specificity (89.5%) in detecting OHS.…”

“…Patients with an AHI > 5 were diagnosed with obstructive sleep apnea (OSAHS). Severity of OSAHS was scaled according to AHI: mild (5-15), moderate (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30), and severe (> 30). The oxygen desaturation index (ODI) was calculated by establishing the total number of episodes of significant oxygen desaturation (> 4% fall from baseline) per hour of sleep.…”

Comparison of measured venous carbon dioxide and calculated arterial bicarbonates according to the PaCO2 and PaO2 cut-off values of obesity hypoventilation syndrome

“…In the hypercapnic hypoxemic patients, the calculated bicarbonate concentrations were increased compared to the measured ones. A previous study also showed higher calculated bicarbonate values compared to measured ones (+0.36±1.23 mmol/L) [8]. The authors stated that there was a close relationship between measured and calculated bicarbonates values, with a difference exceeding ±1 mmol/L in 64% of sample pairs and ±2 mmol/L in 18% of pairs.…”

“…Given these variations, added to our results in concordance analysis, a bicarbonate cut-off value at 29 mmol/L would probably be more appropriate for the detection or the diagnosis of OHS, rather than that at 27 mmol/L proposed by Hart et al [3]. Furthermore, the well known decrease of plasma/serum CO 2 concentration due to the volatility of dissolved CO 2 [8,10] should also be considered . As determined in our laboratory, this decrease was of 5.5%, 12.4%, and 19.7% after 2, 4 and 6 h post-centrifugation ( Figure C in the online supplement).…”

Comparison of measured Serum Total Carbon Dioxide with calculated Bicarbonate calculated from Arterial Blood Gas Analysis

“…The agreement between calculated bicarbonate from venous sample and measured TCO 2 from ABG have shown good agreement in some studies [3][4][5] while revealing conflicting results in others. [6][7][8] The objective is to find out whether the values obtained by both the methods can be used interchangeably in our laboratory.…”