Patient characteristics, management and outcomes in a Nordic subset of the "large observational study to understand the global impact of severe acute respiratory failure" (LUNG SAFE) study

Abstract

Background: The "Large observational study to understand the global impact of severe acute respiratory failure" (LUNG SAFE) study described the worldwide epidemiology and management of patients with acute hypoxaemic respiratory failure (AHRF). Here, we present the Nordic subset of data from the LUNG SAFE cohort.

Methods: We extracted LUNG SAFE data for adults fulfilling criteria for AHRF in intensive care units (ICU) in Denmark, Norway and Sweden, including demographics, co-morbidities, clinical assessment and management characteristics, 90-day survival and length-of-stay (LOS). We analysed ICU LOS with linear regression, and associations between risk factors and mortality were quantified using Cox regression.

Results: We included 192 patients, with a median age of 64 years (IQR 55, 72), and a male-to-female ratio of 2:1. The majority had one or more co-morbidities, and clinicians identified pneumonia as the primary cause of respiratory failure in 56% and acute respiratory distress syndrome (ARDS) in 21%. Median ICU LOS and duration of invasive mechanical ventilation (IMV) were 5 and 3 days. Tidal volumes (TV) were frequently larger than that supported by evidence and IMV allowing for spontaneous ventilation was common. Younger age, co-morbidity, surgical admission and ARDS were associated with ICU LOS. Sixty-one patients (32%) were dead at 90 days. Age and a non-surgical cause of admission were associated with death.

Conclusions: In this subset of LUNG SAFE, ARDS was often not recognised in patients with AHRF and management frequently deviated from evidence-based practices. ICU LOS was generally short, and mortality was attributable to known risk factors.

FIGURE 1

Flow of patient screening and enrolment. The median age of screened patients was 62 years (IQR 53, 73) and 184 (36%) were women. Patients were broadly categorised as non‐sugical (n = 230 [44%]), surgical non‐elective (133 [26%]), planned postoperative (122 [24%]) and trauma (31 [6%]). ARDS, acute respiratory distress syndrome; CXR, chest x‐ray; pf‐ratio; ratio of arterial oxygen partial pressure (PaO₂, in kPa or mmHg) to fractional inspired oxygen (FiO₂); PEEP, positive end‐expiratory pressure; DK, Denmark; NO, Norway; SE, Sweden

FIGURE 2

Frequencies of patients by day of follow‐up and characterised by (A) fulfilment of ARDS‐criteria (Berlin definition ¹ ). (B) Severity of acute hypoxaemic respiratory failure (AHRF) according to PaO₂‐FIO₂ ratio. (C) Method of ventilatory support. (D) ventilator mode. NIV, non‐invasive ventilation; MV, invasive mechanical ventilation; O₂, oxygen therapy only; ARDS, acute respiratory distress syndrome; AHRF, acute hypoxaemic respiratory failure; Controlled, invasive mechanical ventilation with no spontaneous ventilatory efforts; Spontaneous, invasive mechanical ventilation with spontaneous ventilatory efforts; No IMV, no invasive mechanical ventilation (NIV or oxygen therapy only); pf, PaO₂‐FIO₂ ratio; Mild, PaO₂‐FIO₂ ratio > 26.6 and ≤ 40 kPa; Moderate, PaO₂‐FIO₂ ratio > 13.3 and ≤ 26.6 kPa; Severe, PaO₂‐FIO₂ ratio ≤ 13.3 kPa; Non‐AHRF, PaO₂‐FIO₂ ratio > 40 kPa

FIGURE 3

Cumulative frequency distribution of tidal volumes (A, C) and peak inspiratory pressures (B, D) in patients with or mild, moderate or severe AHRF, according to severity of hypoxaemia (PaO₂‐FIO₂ ratio)* and mode of ventilatory support. Dashed red lines illustrate traditional limits for lung‐protective ventilation. AHRF‐severity: Mild, PaO₂‐FIO₂ ratio > 26.6 and ≤ 40 kPa; Moderate, PaO₂‐FIO₂ ratio > 13.3 and ≤ 26.6 kPa; Severe, PaO₂‐FIO₂ ratio ≤ 13.3 kPa; Spontaneous, invasive mechanical ventilation with spontaneous ventilatory efforts; Controlled, invasive mechanical ventilation with no spontaneous ventilatory efforts

FIGURE 4

Odds for continued length of stay (95% CI) in ICU in patients supported by oxygen‐therapy only or non‐invasive ventilation, invasive mechanical ventilation with spontaneous ventilatory efforts or invasive mechanical ventilation with no spontaneous ventilatory efforts. The odds ratio (OR) depicted for each patient group was estimated separately (fit of three separate generalised linear models). Thus, we estimate the odds for staying one more day in the ICU at a given day compared to the reference (day of inclusion). O2 or NIV, non‐invasive ventilation or oxygen therapy only; Spontaneous, invasive mechanical ventilation with spontaneous ventilatory efforts; Controlled, invasive mechanical ventilation with no spontaneous ventilatory efforts

FIGURE 5

Kaplan–Meier estimates of the probability of survival by categories of age (<65 years and ≥65 years). Overall mortality was 32% by day 90. CI, confidence interval

FIGURE 6

(A) Frequencies of patients managed with renal replacement therapy (RRT) by day of follow‐up. (B) Crude estimates of the probability of survival according to requirement for renal replacement therapy (none, early initiation [1–2 days follow‐up] and late initiation [>2 days of follow‐up]). A patient was treated as “not on RRT treatment” until it was provided. Thus, some patients were included two times into the analysis. To model mortality risk for the different RRT categories, we fitted Cox proportional hazards model adjusted for age and gender