Introduction: Unilateral phrenic nerve injury is common in mediastinal tumor resections, which leads to diaphgramatic dysfunction and acute respiratory failure. However, it remains unclear how the other unaffected respiratory muscles compensate for the respiratory weakness caused by unilateral diaphragmatic dysfunction. This study aims to (1)observe the morbidity of respiratory failure following unilateral phrenic nerve injury; and (2) to evaluate relationship between ultrasonic performance of respiratory muscles and the necessity of respiratory support.
Methods: The prospective observational study enrolled 40 ICU patients with post-operative unilateral diaphragmatic dysfunction due to mediastinal tumor surgery. The corhort was divided into Conventional Oxygen Therapy (COT) group and Respiratory Support (RS) group according to whether patients received upgraded respiratory support therapies such as: high-flow nasal cannulation, non-invasive ventilation and invasive mechanical ventilation. Bed-side ultrasound was used to evaluate parasternal intercostal muscles and diaphragm activities during ICU stay.
Results: Of all the patients, 21 received RS and 19 received COT. RS group has a higher proportion of male (76.2% vs 36.8%, p=0.012) and higher SOFA scores (2.15 vs 1.11, p=0.003). The RS group had longer ICU stay(6.09 days vs 2.84 days, p=0.037), and overall hospital stays(20.43 days vs 13.11 days, p=0.029), and a higher risk of bloodstream infections(28.6% vs 5.3%, p=0.036) during the ICU course. At the time of ICU admission, the RS group exhibited higher TFic, respiratory rate (RR), and TFic/TFdi ratio, which decreased significantly at ICU discharge. Both groups showed increasing in bilateral TFdi at ICU discharge compared to admission, and the RS group indicated higher overall TFdi than the COT group. Combining RR and TFic showed predictive value of upgraded respiratory support necessity (AUC 0.83, p=0.001). Logistics regression indicated male, RR, and TFic as independent predictors for the requirement of RS.
Conclusions: Respiratory failure is common in patients following post-operative unilateral phrenic nerve injury. Increased intercostal muscle activities may cover early stage of acute diaphram dysfunction, but eventually, the contralateral diaphragm will compensate for the respiratory workload.
