Table 1.
L-Type and H-Type Presentation of COVID-19, Goals of NIV Helmet CPAP Therapy, and Indications for Initiation of Endotracheal Intubation and Mechanical Ventilation11, 12, 13, 14, 15
| Phenotypes of COVID-19 | Atypical ARDS or L-Type Disease | Typical ARDS or H-Type Disease |
|---|---|---|
| Clinical features | Hypoxemia accompanied by high pulmonary compliance and little shortness of breath | Hypoxemia accompanied by loss of alveolar air space, congested lungs, and shortness of breath |
| Pulmonary mechanics | Low elastance, low ventilation-to-perfusion ratio, low lung weight on CT, low lung recruitment, and reasonably aerated lung tissue | High elastance, high right-to-left shunt, high lung weight, and high lung parenchyma recruitment |
| Respiratory support | NIV helmet CPAP therapy recommended in Italy | Intubation and mechanical ventilation |
| Respiratory support goals | Mild-to-moderate respiratory effort, normal respiratory rate | Ventilation strategies: Less is more Low tidal volumes, low PEEP, and low plateau pressure in order to prevent VILI |
| Signs of improvement | Normal-to-increased PaCO2, low respiratory rate, maintain a PaO2/FiO2 ratio of 150 | Decrease in the need for mechanical ventilatory support, weaning |
| Need for endotracheal intubation and mechanical ventilation | Increasing respiratory rate, excessive patient inspiratory and expiratory effort, low PaCO2, FiO2 >80% after 1 h of initiating helmet CPAP therapy |
Abbreviations: ARDS, acute respiratory distress; COVID-19, coronavirus-2019; CPAP, continuous positive airway pressure; CT, computed tomography; FiO2, fraction of inspired oxygen; NIV, noninvasive ventilation; PaO2, partial pressure of oxygen; PaCO2, partial pressure of carbon dioxide; PEEP, positive end-expiratory pressure; SILI, self-induced lung injury; VILI, ventilator-induced lung injury