Expiratory Flow Limitation in ICU Patients With COPD Linked to Adverse Outcomes

Expiratory flow limitation (EFL) is common among patients with chronic obstructive pulmonary disease in the intensive care unit (ICU) and may be correlated with adverse outcomes, according to a recent study published by Critical Care.

The researchers aimed to assess the prevalence of EFL in patients who require mechanical ventilation for acute respiratory failure. Specifically, they aimed to identify the main clinical characteristics, risk factors, and clinical outcome associated with EFL.

“The mechanisms leading to EFL can vary among different pathologies. COPD patients may develop EFL because of increased expiratory resistanc that tend to reduce the transmural pressure (ie, the difference between the pressure inside and outside the airways), leading to the development of the EPP,” explained the authors. “Incomplete lung emptying is frequently associated with dynamic lung hyperinflation with the generation of intrinsic positive end-expiratory pressure (PEEPi).”

The study involved patients admitted to the ICU with an expected length of mechanical ventilation of 72 hours. The patients were evaluated within 24 hours from ICU admission and for at least 72 hours, in terms of respiratory mechanics, presence of EFL through the PEEP test, and daily fluid balance, according to the study.

In total, 121 patients were enrolled and 31% exhibited EFL upon admission. The evaluations revealed that flow-limited patients had higher BMI, history of pulmonary or heart disease, worse respiratory dyspnoea score, higher intrinsic positive end-expiratory pressure, flow and additional resistance.

Twenty-one (17%) additional patients developed EFL over the course of the 72 hours of mechanical ventilation. The new onset of EFL was associated with a more positive cumulative fluid balance at day 3 compared to patients without EFL, according to the results. Additionally, flow-limited patients had longer duration of mechanical ventilation, longer ICU length of stay, and higher in-ICU mortality.

“The presence of EFL is common among ICU patients requiring mechanical ventilation for acute respiratory failure of different aetiologies,” concluded the authors. “Interestingly, the major determinant for developing EFL in patients during the first 3 days of their ICU stay is a positive fluid balance.”

The researchers suggest the need for additional studies to determine if a restrictive fluid therapy may be associated with a lower incidence of EFL.

Reference

Volta C, Corte F, Ragazzi R, et al. Expiratory flow limitation in intensive care: prevalence and risk factors [published online December 5, 2019]. Critical Care. doi: 10.1186/s13054-019-2682-4.