Hypercapnic respiratory failure is a complex clinical and functional condition, characterized by an alteration of the acid/base (AB) balance, associated with multi-organ impaired function. Several physiological systems are involved in the control of the AB balance, namely the respiratory system, the kidney, as well as red blood cells and blood proteins, and the bicarbonate buffering system. ^[1] The AB balance and hydro-electrolytic (HE) balance are closely related, as for any increase in CO2 (respiratory acidaemia), a counterbalancing metabolic alkalosis occurs as main compensatory mechanism achieved by a complex ion urinary excretion mechanism. ^[2]

Therefore, in order to manage the AB disorders, it is necessary to understand its fine regulatory mechanisms. For the interpretation of AB disorders two approaches can be used: a physical-chemical approach (which relies on the theory of the Strong Ion Difference [SID]) or a pathophysiologic approach (which relies on the compensation laws). ^[3] Many authors consider the physicochemical approach a complex and unfeasible approach, and poorly matching with the clinical reality. Moreover, it requires many factors to calculate the SID. On the other hand, the physio-pathological approach is easier and much more reliable, because it provides a quantitative measurement of the AB compensatory responses. Many trials, performed in different clinical disorders, have supported its use in humans. ^[4]

Pathophysiologic approach, according to the compensation laws, to evaluate the Chronic Obstructive Pulmonary Disease (COPD) acute exacerbations. In hypercapnic AECOPD the hypoventilation produces or worsens respiratory acidosis. Since most of these patients, especially if elderly and critical, are multi-drugs recipients for comorbidities, the AB and HE disorders are very common, producing a potential bias in the interpretation of the final values. ^[5]

This study was carried out on 110 patients who were admitted with COPD exacerbation to the Chest Department, Pratima Relief Institute of Medical Sciences.

Through clinical examination including: general examination, including vital signs (blood pressure, pulse, and respiratory rate) and level of consciousness according to Glasgow Coma Scale and local examination.

Laboratory investigations were performed at the laboratory of the Menoufia University Hospitals. They include the following:

• Complete blood count.
• Arterial blood gases (ABG).
• Electrolyte levels [potassium (K) and sodium (Na)].
• Random blood sugar. Kidney function test (serum urea and creatinine).

Radiological investigations

Chest radiography can be reported as suggestive of COPD but is not diagnostic. Radiographs was used for the diagnosis of pneumonia, and exclusion of other causes of dyspnea in patients with COPD such as ruptured emphysematous bullae.

On admission, all patients received oxygen through nasal cannula or venturi mask to preserve a normal arterial oxygen saturation (≥90%) and received bronchodilators, corticosteroids, and antibiotics ^[6].

Follow-up was done for patients with clinical examination and laboratory investigations, which showed that some of them improved and others deteriorated, so received NIV.

None of our patients refused the treatment or interrupted ventilation for discomfort. NIV was removed when clinical steady-state was reached: respiratory rate7.35, and SaO2>90% with FiO2<40% ^[7].

Patients were transferred to ICU after NIV failure for invasive mechanical ventilation if the following conditions occurred: (a) worsening of arterial pH and PaCO2; (b) clinical signs of disturbed conscious level; and (c) hemodynamic instability ^[8].

In the table 1, the mean age of the NIV positive were 61.28 years and NIV negative were 64.38 years, who were admitted to the Department of TB and Chest, with hypercapnic COPD exacerbation. They were classified according to the type of management into two groups: the first group received medical treatment and the second received noninvasive positive pressure ventilation (NIPPV).

Table 1: Mean Age of the studied group

Table 2: Distribution of sex of the studied group

In table 2, the total number of patients were 90, where 67 of them were males and 23 females.

Table 3: Arterial blood gases finding of the studied group

In table 3, according to ABG finding, patients were classified into three groups: the first group comprised 50 (55.6%) patients who had compensated respiratory acidosis, and the majority of them (39 patients) received medical treatment only. The second group comprised 22 (24.4%) patients, who had mixed respiratory acidosis and metabolic alkalosis. Overall, 16 patients needed non-invasive mechanical ventilation with the medical treatment. The third group comprised 18 (20%) who had combined respiratory and metabolic acidosis. Of them, 14 patients needed non-invasive mechanical ventilation with the medical treatment and mean PO2 was 56.38 mmHg whereas mean PCO2 was 61.68 mmHg.

Table 4: Electrolytes finding of the studied group

In table 4, the mean potassium of the patients who need medical treatment only was 5.78Eq/l and mean Sodium was 138.8 mEq/l, whereas the mean potassium for the other group was 6.38 mEq/l and mean Sodium was 136.9±5.9mEq/l. The mean serum Bicarbonate of the group the need medical treatment only was 24.68mEq/l. The mean serum Bicarbonate of the other group was 30.25mEq/l.

Table 5: Outcome and characteristic of the group that needed NIPPV from the start

Table 6: Effect of COPD treatment on the patient electrolytes

In table 6, the Sodium and Potassium levels before treatment were 138.1±8.1 and 6.8±0.75 mEq/l, respectively, and mean Sodium and Potassium levels after treatment were 136.4±8.8 and 5.5±0.68 mEq/l, respectively.

Acid/base (AB) balance abnormalities are linked to multi-organ impairment in hypercapnic respiratory failure, a complex clinical and functional disease. ^[9] The kidney, respiratory system, red blood cells, blood proteins, and bicarbonate buffering system are among the physiological systems that regulate the acid-base balance. ^[10] The hydro-electrolytic (HE) balance and the AB balance are intimately associated. When CO2 levels rise (respiratory acidaemia), a metabolic alkalosis counteracts the increase. This is mostly accomplished by a complex excretion system involving ions in the urine. Therefore, knowledge of the intricate regulatory processes governing AB diseases is essential for their management. ^[11] The present study was conducted to assess serum electrolytes, acid–base balance and need for noninvasive ventilation in patients with hypercapnic acute exacerbation of chronic obstructive pulmonary disease (AECOPD).

Schiavo, evaluated acid–base and hydroelectrolite alterations in these subjects and the effect of non-invasive ventilation and pharmacological treatment. They retrospectively analysed 110 patients consecutively for acute exacerbation of hypercapnic chronic obstructive pulmonary disease. ^[12]

On admission all patients received oxygen with a Venturi mask to maintain arterial oxygen saturation at least >90 %, and received appropriate pharmacological treatment. Non-Invasive Ventilation (NIV) was started when, despite optimal therapy, patients had severe dyspnea, increased work of breathing and respiratory acidosis. ^[13]

Krishna, analyzed 74 patients for hypercapnic AECOPD. Based on arterial blood gas finding, we categorized our patients into three main groups: the first group comprised 44 (59.4%) patients who had compensated respiratory acidosis, and the majority of them (35 patients) received medical treatment only. The second group comprised 17 (22.97%) patients, who had mixed respiratory acidosis and metabolic alkalosis. Overall, 13 patients needed non-invasive mechanical ventilation with the medical treatment. The third group comprised 13 (17.5%) who had combined respiratory and metabolic acidosis. Of them, 11 patients needed non-invasive mechanical ventilation with the medical treatment The shortcoming of the study is small sample size.  ^[14]

AECOPD afflict millions of patients with COPD annually and account for substantial health care costs. AECOPD episodes can be triggered or complicated by other comorbidities. Oxygen, physical therapy, mucolytics, and airway clearance devices may be useful in selected patients. Pharmacologic management includes broncho- dilators, corticosteroids, and antibiotics in most patients. In hyper- capneic respiratory failure, NPPV may allow other therapies to work and thus avoid endotracheal intubation. Although mild episodes of AECOPD are generally reversible, more severe forms of respiratory failure are associated with a substantial mortality and a prolonged period of disability in survivors.

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