Diagnostic significance of pleural fluid pH and pCO2

Abstract

The diagnosis of pleural effusion is still difficult. The presence of pleural effusion can be confirmed by radiological studies including simple chest radiography, ultrasonography, or computed tomography. Identifying the causes of pleural effusions by pleural fluid analysis is essential.Aim of this work: The aim of this work is to assess the role of pleural fluid pH and pCO 2 in differentiating the etiologies of pleural effusion and to study the correlation between pleural fluid pH and pCO 2 and cellular content of the effusion.Results: We conducted this study on 50 patients with pleural effusions of different causes. The patients were classified into 5 groups according to the cause. For all the patients, measurement of pleural pH, pCO 2 , pO 2 , HCO 3 , protein, LDH, glucose and WBC was done. We observed lowest pH in complicated parapneumonic effusion (empyema) 6.80 ± 0.15 and highest pH was observed in transudative effusion 7.47 ± 0.07. Tuberculous effusion has pH lower than pH of malignant effusion 7.17 ± 0.017 and 7.39 ± 0.08, respectively. Post pleurodesis malignant effusion has pH lower than pH of malignant effusion 7.28 ± 0.17 and 7.39 ± 0.08, respectively. There is a strong inverse correlation between pH and pCO 2 , WBC, LDH and protein (r = À0.813 and p < 0.001), (r = À0.796 and p, 0.001), (r = À0.829 and p, 0.001) and (r = À.837 and p, 0.001), respectively. While there is a weak correlation between pH and glucose of pleural fluid (r = 0.249 and p = 0.066). The highest increase of PNL numbers was in empyema (20169 ± 8094.8 cells/cc). The highest increase of lymphocytes was in malignant effusions (4285.00 ± 2948.20 cells/cc) and tuberculous effusion (3977.7 ± 3169 cells/cc).

Discrimination of Exudative Pleural Effusions Based on Pleural Adenosine Deaminase (ADA)-C-Reactive Protein (CRP) Levels, and Their Combination: An Observational Prospective Study

“…Several biochemistries have been widely used in differentiating between the three categories. Pleural pH levels are lower among empyemas and parapneumonic effusions, although low pH levels could also be observed in TPE and MPE [ 20 ]. Pleural fluid for total white blood cell count and differential cell count heightens suspicion for PPE in case of a neutrophilic predominance.…”

An acidic microenvironment in Tuberculosis increases extracellular matrix degradation by regulating macrophage inflammatory responses

“…An acidic microenvironment arises during the host response to infection due to lactic acid secretion by inflammatory cells, and inflamed tissues typically have an extracellular pH around 7.0 compared to pH 7.4 in healthy tissue. In TB patients, CSF [ 15 ], pleural [ 16 ], peritoneal [ 17 ] and lung lining fluid [ 18 ] are more acidic than healthy tissue. Extracellular acidosis is signaled by the Ovarian Cancer G-Protein Coupled Receptor (OGR) family of cell surface receptors, including OGR-1, T-cell death associated gene-8 (TDAG-8) and G-protein coupled receptor-4 (GPR-4) [ 19 ].…”