P010 The characteristics of patients with symptomatic unilateral diaphragm dysfunction and hypoventilation

Abstract Introduction Despite the diaphragm being the primary muscle involved in respiration, clinical manifestations in those with unilateral diaphragm dysfunction (UDD) are heterogeneous. Though often asymptomatic, UDD can be implicated in breathlessness, sleep disordered breathing and hypoventilation. The characteristics of those with UDD and sleep hypoventilation are poorly described. We aimed to provide a descriptive analysis of patients with UDD considered for plication, and the characteristics of those with hypoventilation. Methods A clinical audit was performed at a tertiary centre providing evaluation of UDD for consideration of plication. Anthropomorphic data, symptom scores and respiratory function measurements were collected. Patients underwent polysomnography, with hypoventilation assessed based on PaCO2 >45mmHg and/or transcutaneous CO2 rise of ≥10mmHg for over 10minutes. Characteristics of those with- and without hypoventilation were compared using unpaired t-test or Mann-Whitney U test. Results 39 patients were included (median age 65 [50—73]). Of the 34 participants who underwent polysomnography, 14 (41.2%) demonstrated hypoventilation. Compared to those without hypoventilation, the group with hypoventilation had a lower forced vital capacity (74±17.3% vs 61.8±13.4%, p<0.05), lower maximal inspiratory muscle pressures (55.8±16.4% vs 39.3±13.4%%, p=0.02) and lower maximal expiratory muscle pressures (84.5 [74—93.8]% vs 66 [47.5—86.5]%, p=0.03). There were no differences in body mass index. Discussion Hypoventilation was common amongst patients with symptomatic UDD referred for plication, who may benefit from nocturnal ventilatory support. Though respiratory function was found to be worse in those with hypoventilation, it was surprising that BMI was no different.