RT Journal Article SR Electronic T1 Effects of Thyroid Hormone Treatment on Diaphragmatic Efficiency in Mechanically Ventilated Subjects With Nonthyroidal Illness Syndrome JF Respiratory Care FD American Association for Respiratory Care SP 1199 OP 1207 DO 10.4187/respcare.06770 VO 64 IS 10 A1 Giuseppe Bello A1 Giorgia Spinazzola A1 Valentina Giammatteo A1 Luca Montini A1 Gennaro De Pascale A1 Alessandra Bisanti A1 Maria G Annetta A1 Eliana Troiani A1 Antonio Bianchi A1 Alfredo Pontecorvi A1 Mariano A Pennisi A1 Giorgio Conti A1 Massimo Antonelli YR 2019 UL http://rc.rcjournal.com/content/64/10/1199.abstract AB BACKGROUND: Several respiratory abnormalities can be present in primary hypothyroidism and can be reversed with adequate hormone treatment. However, the role of thyroid hormone replacement therapy on the respiratory system in patients with nonthyroidal illness syndrome is still unclear. This physiologic study evaluated the effect of thyroid hormone treatment on respiratory muscle function in subjects with nonthyroidal illness syndrome and while on mechanical ventilation. The primary end point was neuromechanical efficiency, which provides an estimate of the efficiency of diaphragmatic contraction. Secondary end points were the transdiaphragmatic pressure-time product and the swing of the electrical activity of the diaphragm, which reflect the work of breathing and inspiratory effort, respectively.METHODS: Fifteen subjects on mechanical ventilation for ≥48 h and with a diagnosis of nonthyroidal illness syndrome who had a failed spontaneous breathing trial, received intravenous triiodothyronine. The hormone was administered as an intravenous bolus of 0.4 μg/kg triiodothyronine, followed by continuous perfusion at 0.6 μg/kg for 24 h. Neuromechanical efficiency was calculated as the ratio between the drop in airway pressure during an expiratory occlusion and the corresponding electrical activity of the diaphragm peak. Recordings were taken at baseline and after 3, 6, and 24 h.RESULTS: After study completion, free triiodothyronine serum concentrations increased in all the subjects (mean ± SD increase, 0.84 ± 0.34 pg/mL). Neuromechanical efficiency showed no significant changes throughout the study (mean ± SD baseline, 1.40 ± 0.87 cm H2O/μV; 3 h, 1.28 ± 0.64 cm H2O/μV; 6 h, 1.33 ± 0.87 cm H2O/μV; 24 h, 1.41 ± 0.96 cm H2O/μV). Similarly, no variations in transdiaphragmatic pressure-time product per min (mean ± SD baseline, 238.1 ± 124 cm H2O × s/min; 3 h, 242.5 ± 140.3 cm H2O × s /min; 6 h, 247.5 ± 161.7 cm H2O × s/min; 24 h, 281.2 ± 201.2 cm H2O × s/min) or swing of electrical activity of the diaphragm (mean ± baseline, 20.9 ± 13.1 μV; 3 h, 17.2 ± 8.3 μV; 6 h, 17.4 ± 11.3 μV; 24 h, 20.3 ± 13.7 μV) were observed during hormone administration.CONCLUSIONS: In the subjects on mechanical ventilation who were admitted to the ICU with nonthyroidal illness syndrome, thyroid hormone replacement treatment did not yield any benefit on respiratory muscle function when assessed by neuromechanical efficiency, which indicated that, in these subjects restoring normal levels of serum thyroid hormones is debatable. (ClinicalTrials.gov registration NCT03157466.)