Thyroid profile in patients with chronic respiratory failure: effect of domiciliary noninvasive positive airway pressure

Background Various thyroid hormone states have been described in patients with respiratory failure. Domiciliary noninvasive positive airway pressure (NPAP) can be used for management of chronic respiratory failure. Aim This study aims to assess thyroid function in patients with chronic respiratory failure and to evaluate the effect of domiciliary NPAP on thyroid hormone levels. Patients and methods Forty-five patients were admitted with acute on top of chronic respiratory failure of various causes; all were addressed after discharge to domiciliary NPAP, either continuous positive airway pressure (CPAP) or bi-level positive airway pressure (BPAP). Thyroid hormones and arterial blood gas were assessed on admission, at the time of discharge, and at 2-month follow-up. Results On admission, 21 (46.67%) patients had nonthyroidal illness syndrome (NTIS) and eight (17.78%) patients had subclinical hypothyroidism. PO2 level was significantly lower in patients with NTIS than subclinical hypothyroidism, and it correlated positively with thyroid hormone levels. A highly significant increase in PO2 and reduction in PCO2 were found after 2 months of discharge on domiciliary CPAP or BPAP as compared with their levels on discharge and admission. The percentage of change in arterial blood gas and thyroid hormone levels (between admission and 2 months follow-up) when comparing CPAP with BPAP was statistically nonsignificant. Conclusion NTIS and subclinical hypothyroidism can occur in patients with acute-on-chronic respiratory failure correlating with PO2 even in 2-month follow-up period in patients on domiciliary NPAP, with no significant difference between CPAP and BPAP