More and more patients are undergoing elective surgery after SARS-CoV-2 infection, and little is known about the residual pulmonary changes in these patients after infection and postoperative pulmonary complications. So, we propose an observational study comparing postCOVID-19 patients with normal population (control group) undergoing surgery.

The most common lung complications of severe COVID-19 are pneumonia and hypoxemic respiratory failure/ARDS. Manifestations of lung inflammation or fibrosis were also observed in late stages of COVID-19 causing respiratory sequelae. Fibrous lesions may form during the healing of pulmonary chronic inflammation or proliferative diseases, with gradual replacement of cellular components by scar tissues indicating a poor outcome of COVID-19. Ultrasound allows to stratify the severity of lung damage and combined with the clinic, can help estimate the patient's prognosis and support therapeutic decision-making. On the other hand, pulmonary inflammatory processes and fibrosis are responsible for a decrease in respiratory distensibility or pulmonary compliance. Pulmonary parenchyma distensibility is known as static distensibility or compliance and it´s calculated by mechanical ventilators during general anesthesia.

There are no studies that determine the results of lung ultrasound and pulmonary compliance in preoperative and intraoperative period respectively in postCOVID patients, and the postoperative complications of postCOVID patients are poorly understood.

Control group

Inclusion criteria.:

-Patients over the age of 18 who did not have COVID-19 and who are going to undergo scheduled surgery

Exclusion criteria:

• Patients under the age of 18.
• Unstable patients in shock
• Patients in current state of pulmonary hypertension or heart failure
• Patients with moderate-severe pulmonary pathology prior to surgery.
• Patients previously surgery for chest surgery
• Patients in current state of respiratory infection

Post-COVID group Inclusion criteria

-Post-COVID-19 patients (confirmed by PCR) >18 years undergoing scheduled surgery without pulmonary disease prior to SARS-CoV-2 infection, that at the time of surgery present negative PCR and absence of clinic due to SARS-CoV-2 infection.

Exclusion criteria:

• Patients under the age of 18
• Unstable patients in shock
• Patients in current state of pulmonary hypertension or heart failure
• Patients with moderate-severe pulmonary pathology prior to SARS-CoV-2.
• Patients previously surgery for chest surgery
• Patients in current state of respiratory infection

The written consent forms are obtained from all the subjects who agreed to participate in the study. Patients who suffered Covid-19 prior to surgery without previous moderate-severe pulmonary pathology, that at the time of surgery present negative PCR and absence of clinic due to SARS-CoV-2, are included in the Post-COVID 19 group. The "control group" includes patients over the age of 18 who did not have COVID-19 and without moderate-severe pulmonary pathology prior to surgery.