A proposed lung ultrasound and phenotypic algorithm for the care of COVID-19 patients with acute respiratory failure

Abstract

Pulmonary complications are the most common clinical manifestations of coronavirus disease (COVID-19). From recent clinical observation, two phenotypes have emerged: a low elastance or L-type and a high elastance or H-type. Clinical presentation, pathophysiology, pulmonary mechanics, radiological and ultrasound findings of these two phenotypes are different. Consequently, the therapeutic approach also varies between the two. We propose a management algorithm that combines the respiratory rate and oxygenation index with bedside lung ultrasound examination and monitoring that could help determine earlier the requirement for intubation and other surveillance of COVID-19 patients with respiratory failure.

Keywords: COVID-19; and oxygenation index; lung ultrasound; respiratory failure; respiratory rate.

Fig. 1

A) Computed tomography scan in a 68-yr-old coronavirus disease (COVID-19) patient with progressive dyspnea and oxygen saturation of 86% on room air. A L-type phenotypic pattern is shown. Lung ultrasound revealed a small right pleural effusion, several anterior subpleural consolidations, and B-lines in the posterior region. While in the intensive care unit, the patient experienced fever and progressive respiratory deterioration requiring intubation after 24 hr. The peripheral pulse oximetry remained at 87% despite a fraction of inspired oxygen (F_iO₂) at 100%, positive end-expiratory pressure titration of 10 cmH₂O, and inhaled nitric oxide of 10 ppm. Blood gas revealed a pH of 7.37, partial pressure of carbon dioxide (PCO₂) of 43.4 mmHg, and oxygen partial pressure (PaO₂) of 63.8 mmHg. After 15 min of prone positioning, the SaO₂ increased to 95% and on the following blood gas assessment, the PaO₂/ F_iO₂ ratio was 268 with a compliance of 53 mL·cmH₂O. B) A repeat CT scan in the same patient was done on day 4 to rule-out a pulmonary embolism. A transition to the H-type is observed. C) Transition in a 49-yr-old man recovering from COVID-19 respiratory failure. His phenotype changed from an H-type to an (D) L-type (courtesy of Dr. Emmanuel Charbonney and Dr. Lawrence Leroux)

Fig. 2

COVID-19 respiratory failure management. Following clinical and ultrasound examination to determine the L-type (low elastance) or H-type (high elastance) pattern, oxygen therapy is initiated. There can be progression or regression from one type to the other. The respiratory rate and oxygenation (ROX) index can be used, calculated, and monitored along with lung ultrasound to help in the process of deciding if and when to intubate. Mechanical ventilation settings include the tidal volume (TV), the respiratory rate (RR), and the degree of positive end-expiratory pressure (PEEP), which will vary according to the L or H phenotype. * Indicates that the decision to intubate is based on oxygenation and ventilation failure or compromised airway patency before initiating mechanical ventilation. ARDS = acute respiratory distress syndrome; CT = computed tomography; ECMO = extracorporeal membrane oxygenation; ETCO₂ = end-tidal carbon dioxide; F_iO₂ = inspired oxygen; P = pressure; PaO₂ = oxygen partial pressure; PAP = pulmonary artery pressure; PBW = predicted body weight; Pplat = plateau pressure; ROX index; SpO₂ = pulse oxygen saturation; V/Q = ventilation perfusion. Adapted in part from Gattinoni et al. ^{11, 13} and Marini et al. ²⁷

Fig. 3

COVID-19 lung ultrasound findings. (A) B-lines (arrow); (B) irregular and broken pleural lines with multiple B-lines (dotted region); (C) peripheral or subpleural consolidation with (D) minimal colour Doppler signal. (E) Larger zone of consolidation in right lower posterior base with air bronchograms and (F) reduced perfusion using colour Doppler. (Courtesy of Dr. Stéphan Langevin and Dr. Caroline Gebhard) (Videos 3A, 3B, 3C, 3D, 3E, and 3F available as Electronic Supplementary Material)

Fig. 4

Computed tomographic and lung ultrasound correlation in a COVID-19 patient with subpleural consolidation. (Courtesy of Dr. Stéphan Langevin and Mr. Jacques Cadorette) (Video 4 available as Electronic Supplementary Material)

Fig. 5

Examples of various COVID-19 complications detected using bedside ultrasound. Pulmonary hypertension with a trans-tricuspid pressure gradient (PG) of 45 mmHg in a patient developing right ventricular failure. B) Transthoracic short-axis aortic valve view showing a dilated right ventricular outflow tract (RVOT) of 35 mm and pulmonary artery in a patient with pulmonary embolism. C) Deep venous thrombosis of the femoral vein. D) Abnormal hepatic venous flow (HVF) Doppler velocity suggestive of right ventricular diastolic dysfunction. E) Renal venous congestion pattern-II associated with right ventricular dysfunction., F) Enlarged optic nerve sheath (ONS), in a patient with severe encephalopathy and extra-pyramidal signs. (Courtesy of Dr. Caroline Gebhard and Stéphan Langevin.). AR = atrial reversal HVF; D = diastolic HVF; S = systolic HVF. (Video 5B, 5C available as Electronic Supplementary Material.)

Fig. 6

Lung ultrasound examination in a COVID-19 patient with severe hypoxia. before (A–C) and after (D–F) prone positioning. Note the significant changes with loss of pleural fluid and consolidation with increased aeration. Oxygen requirement were significantly reduced from 100% inspired oxygen to 60% for an adequate oxygen saturation after proning. RLPAL = right lower posterior axillary line; RMPAL = right middle posterior axillary line; RUPAL = right upper posterior axillary line. (Courtesy of Dr. Stéphan Langevin.) (Videos 6A, 6B, 6C, 6D, 6E, and 6F available as Electronic Supplementary Material.)

Fig. 7

Cardiac examination and portal vein interrogation before (A–B) and after (C–D) prone positioning. Note the reduction in the size of the right ventricle (RV) in relation to the left ventricle (LV) and the improved portal velocities and reduction in the portal vein pulsatility index (PVPI). (Courtesy of Dr. Stéphan Langevin.) (Videos 7A and 7C available as Electronic Supplementary Material.)