Clinical risk conditions for acute lung injury in the intensive care unit and hospital ward: a prospective observational study

Abstract

Background: Little is known about the development of acute lung injury outside the intensive care unit. We set out to document the following: the association between predefined clinical conditions and the development of acute lung injury by using the American-European consensus definition; the frequency of lung injury development outside the intensive care unit; and the temporal relationship between antecedent clinical risk conditions, intensive care admission, and diagnosis of lung injury.

Methods: We conducted a 4-month prospective observational study in three Spanish teaching hospitals, enrolling consecutive patients who developed clinical conditions previously linked to lung injury, both inside and outside the intensive care unit. Patients were followed prospectively for outcomes, including the diagnosis of acute lung injury or acute respiratory distress syndrome.

Results: A total 815 patients were identified with at least one clinical insult; the most common were sepsis, pneumonia, and pancreatitis. Pulmonary risk conditions were observed in 30% of cases. Fifty-three patients (6.5%) developed acute lung injury; 33 of these (4.0%) met criteria for acute respiratory distress syndrome. Lung injury occurred most commonly in the setting of sepsis (46/53; 86.7%), but shock (21/59; 36%) and pneumonia (20/211; 9.5%) portended the highest proportional risk; this risk was higher in patients with increasing numbers of clinical risk conditions (2.2%, 14%, and 21% (P < 0.001) in patients with one, two, and three conditions, respectively). Median days (interquartile range) from risk condition to diagnosis of lung injury was shorter with pulmonary (0 (0 to 2)) versus extrapulmonary (3 (1 to 5)) (P = 0.029) risk conditions. Admission to the intensive care unit was provided to 9/20 (45%) patients with acute lung injury and to 29/33 (88%) of those with acute respiratory distress syndrome. Lung injury patients had higher mortality than others (acute lung injury 25.0%; acute respiratory distress syndrome 45.5%; others 10.3%; P < 0.001).

Conclusion: The time course from clinical insult to diagnosis of lung injury was rapid, but may be longer for extrapulmonary cases. Some patients with lung injury receive care and die outside the intensive care unit; this observation needs further study.

Figure 1

Patient flow diagram. Locations (ward versus intensive care unit) of risk factor identification and diagnosis of acute lung injury/acute respiratory distress syndrome (ALI/ARDS) are displayed along with hospital outcomes for each group. ICU, intensive care unit.

Figure 2

Prevalence of ALI and ARDS by clinical risk condition. The proportion of patients with each clinical risk condition who went on to develop acute lung injury (ALI; blue columns) or acute respiratory distress syndrome (ARDS; red columns) is shown for all patients (a) and for only those admitted to the intensive care unit (b). In both panels the number of patients at risk with each clinical insult is displayed numerically below each category label.

Figure 3

Time from clinical risk to diagnosis of ALI/ARDS. Kaplan–Meier curves displaying time from clinical risk condition to diagnosis of acute lung injury/acute respiratory distress syndrome (ALI/ARDS) are shown for all patients (a) and separated according to pulmonary (red line) versus extrapulmonary (blue line) risk conditions (b).

Figure 4

Timing of ICU admission relative to clinical risk and diagnosis of lung injury. Frequency histograms are shown for the timing of intensive care unit (ICU) admission relative to development of clinical risk condition (a), and diagnosis of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) relative to ICU admission (b), including together all patients with ALI and ARDS admitted to the ICU. Dx, diagnosis; IQR, interquartile range.