Lung ultrasound and blood gas-based classification of critically ill patients with dyspnea: A pathophysiologic approach

IntroductIonDyspnea is the most common presenting symptom among critically ill patients.[1] Various etiologic classifications of dyspnea focus on history, physical examination, chest radiography, or electrocardiography (ECG) to classify patients in cardiovascular, respiratory, or metabolic categories.[1,2] Such classifications are difficult to interpret in critically ill patients, due to overlapping symptoms and signs or lack of them in acutely developing conditions.[3] In the previous decade, elevated B-type natriuretic peptide was considered sensitive and was a specific marker to distinguish cardiovascular causes of acute dyspnea, but this biomarker is elevated in a variety of noncardiac critical conditions, including sepsis.[4,5] Further, etiologies of dyspnea are more diverse, and an objective, minimally-invasive, less expensive, and rapid assessment tool for the evaluation of dyspnea is required for critically ill patients.Development and expansion of lung ultrasound (LUS) have helped in the classification of acute dyspnea.[6] This technique is rapid, is noninvasive, and has no additional expense in settings where a bedside ultrasound is available.It is an extension of clinical examination and can distinguish between a dry and a wet lung field.In combination with cardiac ultrasound, it was possible to distinguish pulmonary and cardiac causes of dyspnea in one study.[6] Arterial blood gas (ABG) analysis has 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.