Bedside Ultrasound Assessment of Lung Reaeration in Patients With Blunt Thoracic Injury Receiving High-Flow Nasal Cannula Oxygen Therapy: A Retrospective Study

Abstract

Background: High-flow nasal cannula (HFNC) oxygen therapy has been shown to reduce the need for mechanical ventilation and decrease the duration of hospital and intensive care unit (ICU) stays for patients with a severely compromised respiratory system. This study aims to observe the evolution of lung aeration via lung ultrasound score (LUS) in a chest-injured population who had been treated with HFNC oxygen therapy, and to assess the benefit of the HFNC oxygen therapy in trauma patients. Methods: A retrospective study examined trauma patients with moderate to severe thoracic injuries who were admitted to the ICU at a tertiary hospital between October 2015 and March 2017. The decision to initiate HFNC oxygen therapy was made at the discretion of the trauma surgeon and respiratory therapist when supplemental oxygen delivery was required. All of the patients were assessed by transthoracic lung ultrasound every day after being admitted into the ICU. We retrospectively analyzed 3 time points for this study: the initial emergency intensive care units presentation within 12 hours (T1), 24 to 48 hours after the treatment (T2), and 72 to 96 hours after the treatment (T3). Transthoracic lung ultrasound was performed by an experienced investigator with level 3 certification using a Mindray M9 echograph and a 2- to 4-MHz round-tipped probe. Primary outcomes were the need for intubation after HFNC oxygen therapy for respiratory failure during the treatment within 72 hours, the length of ICU stay, and mortality of 28 days. Results: During the study period, 50 patients with blunt chest trauma were admitted to the study; 18 patients received HFNC therapy and 32 received conventional oxygen therapy (COT); there was no significant difference in the baseline clinical characteristics between the 2 groups. The length of ICU stay and intubation rate for respiratory failure within 72 hours were significantly different between the 2 groups ( P < .05), but there was no difference in the 28-day mortality. The LUS of the COT group was not significantly different from T1 to T2 or from T2 to T3 ( P > .05). However, the LUS decreased significantly—by 25% from T1 to T2 ( P < .05) and by 31% from T1 to T3 ( P < .05) in the HFNC therapy group. The LUS of the patients intubated for respiratory failure within 72 hours, in the COT group increased from T1 (17 ± 3) to T3 (21 ± 3), and the LUS (21 ± 3) was much higher than the patients who were not intubated (11 ± 3) at T3; the LUS of the HFNC group was all above 15, which was not significantly different from T1 to T2 or from T2 to T3 ( P > .05). Conclusions: High-flow nasal cannula oxygen therapy may be considered as an initial respiratory therapy for trauma patients with blunt chest injury. High-flow nasal cannula therapy could improve lung aeration as noted by the transthoracic lung ultrasound assessment, and LUS may help the attending physicians identify the usefulness of HFNC therapy and decide whether to continue the use of HFNC therapy or intubate the patient.