Lung Ultrasound and Blood Gas-Based Classification of Critically Ill Patients with Dyspnea: A Pathophysiologic Approach

Introduction: The objective of this study was to classify dyspneic patients and to evaluate outcome variables on the basis of lung ultrasound (LUS) and arterial blood gas (ABG) findings.

Methods: We performed a retrospective chart-based review in which we included patients with dyspnea admitted to our intensive care unit (ICU) between March 2015 and August 2016. On the basis of LUS (presence of A-lines/B-lines) and ABG (hypoxia/hypercarbia), patients were classified into six groups: (i) metabolic defect (dry lung, no hypoxia); (ii) perfusion defect (dry lung, hypoxia); (iii) ventilation defect (dry lung, hypoxia, and hypercarbia); (iv) ventilation and alveolar defect (wet lung, hypoxia, and hypercarbia); (v) alveolar defect-consolidation ([wet lung] hypoxia, no echocardiographic [ECG] abnormality); (vi) alveolar defect-pulmonary edema (wet lung [usually bilateral], hypoxia, ECG abnormality). The patient's demographic data, sequential organ failure assessment (SOFA) score, need for intubation, vasopressors, form of mechanical ventilation, ICU outcome, and length of stay were noted.

Results: A total of 244 out of 435 patients were eligible for inclusion in the study. The median age was 56 years. 132 patients (54.1%) required mechanical ventilation, and median SOFA score was 7. Noninvasive ventilation was required in 87.5% of patients with ventilation defect as compared to 9.2% with alveolar defect-consolidation (P < 0.0001). We had 21.7% mortality in patients with alveolar defect-consolidation, 10.8% mortality in patients with metabolic defect, and 8.7% mortality in patients with alveolar defect-pulmonary edema (P < 0.0001).

Conclusion: This classification gives an organized approach in managing patients with dyspnea. It predicts that patients with alveolar defect-consolidation are most sick of all the groups and need immediate intervention.