Purpose of the study is to investigate the effect of hyperbaric oxygen on FVC, FEV1 andon oxygen saturation in post-COVID-19 patients, The effect of breathing exercises in formof diaphragmatic breathing exercise and pursed lip breathing with traditional medicaltreatment in form of (vitamin D, vitamin C and anticoagulation drugs on FVC, FEV1 and onoxygen saturation in post-COVID-19 patients.and the difference between the effect ofhyperbaric and breathing exercises in form of diaphragmatic breathing exercise and pursedlip breathing with traditional medical treatment in form of (vitamin D, vitamin C andanticoagulation drugs on FVC, FEV1 and on oxygen saturation in post-COVID-19 patientsSeventy two covid-19 patients from both genders ranged in age chronology from twenty oneto sixty six years will be conducted to participate in this study .Selection of the studysample and evaluate of pulmonary functions improvement as well as hyperbaric oxygentherapy will be conducted at Agriculture Hospital in El Mansoura town.The study sample will be divided randomly into two equal groups of(A&B).All patientsparticipated in the current study will receive breathing excesses in form ofDiaphragmatic breathing exercise and Pursed lip breathing with traditional medicaltreatment in form of (vitamin D, vitamin C and Anticoagulation drugs ,group A willreceive 60 minutes of HBOT(100%oxygen at 2 ATA with five minutes air breaks every twentyminutes daily in morning for three weeks then take period time of rest about 30 minutesbefore starting breathing exercise.The Body mass index (BMI) of each participated patient will be determined by measuringweight/ Kg and height/ m2 using Electronic weight and height scale to include BMI25.0-29.9 Kg/ . Also using Digital spirometer SMP 21/01 RD (Russian) for measuring of FVCparameters , to be less than 80% ,FEV1 to be less than 80% and Pulse Oximeter formeasuring Oxygen saturation to range from 90%to 95% assessment will be done before andafter treatment.The obtained results of this study will measure Forced vital capacity (FVC), Forcedexpiratory volume (FEV1) and oxygen saturation to determine the significant improvementof participated patients.