Rezvankhoo K, Stella F, Gilman C, and colleagues
Type I: Fever with or without respiratory symptoms, negative chest x-ray, no hypoxia on blood gas (commonly hypocapnic). If no desaturation during walk test, then patient can be safely discharged home. (Large majority of patients fall into this category)
Type II: Fever and hypoxia OR fever and positive x-ray. These patients MUST be admitted because they can deteriorate very quickly.
Type III: Fever and hypoxia AND positive x-ray. Usually spO2 > 90% can be obtained with high flow oxygen. These patients need hospitalization in areas with continuous monitoring and non-invasive ventilation (NIV).
Type IV: Early Acute Respiratory Distress Syndrome (ARDS). These patients needs NIV to achieve acceptable levels of oxygen saturation.
TYPE V: ARDS. The typical patient is male between 35 and 70 years of age, pO2 between 30 and 45 at arterial blood gas analysis. If lung US shows only a wet lung, patient can be treated at the beginning with NIV. If lung US shows reduced lung sliding and/or multiple subpleural areas of consolidation, then early endotracheal intubation is necessary. They are easy to vent and need high PEEP (usually 15) to obtain acceptable sat levels.