Effects on Pulmonary Functions in Patients Undergoing Hyperbaric Oxygen Therapy: A Prospective Observational Study

Abstract Introduction: Hyperbaric Oxygen Therapy (HBOT) consists of administering oxygen at pressures higher than atmospheric pressure. Though HBOT remains one of the safest therapies used today, it is not completely devoid of side effects. Pulmonary oxygen toxicity can result as a result of continuous exposure of elevated levels of oxygen for increased duration and at increased pressures. The main pathological manifestations occur as acute exudative phase followed by subacute proliferative phase. Effects of HBOT on pulmonary functions has not been studied in detail. This study was conducted to ascertain the effects of HBOT on pulmonary functions and determine if these changes are reversible in nature. Material and Method: A prospective observational study was conducted at a tertiary care hospital over a period of 02 years. A total of 72 patients who were undergoing HBOT for any indication normal chest radiograph and normal spirometry/DLCO were included in the study. Spirometry and DLCO was done initially at the time of inclusion and repeated after half of the total planned HBOT sessions and finally at the end of all sessions of HBOT. Spirometry and DLCO was also repeated 6 months post completion of HBOT. The HBOT protocol consisted of breathing 100% oxygen at 2.4 atmospheric absolute (ATA) for 90 minutes which was referred as one session. Total sessions varied from 20-30 based on indication and response of their primary disease to HBO. Results: The mean age score in study population was 47.12 ± 12.88. Among the study population, 12(24%) participants were male and 38(76%) participants were female. The mean BMI was 24.49 ± 5.45. The mean DLCO was 6.67 ± 1.45 ml/min/mm Hg pre intervention, it was 6.38 ± 1.43 ml/min/mm Hg at mid cycle and 6.21 ± 1.41 ml/min/mm Hg post intervention and at 6 months follow up it was 6.43 ± 1.46 ml/min/mm Hg. The difference in the DLCO at mid cycle, post intervention and 6 months follow up period with baseline value were statistically significant (P value <0.05). The mean FVC was 2.59 ± 0.59 L pre intervention, 2.41 ± 0.6 L at mid cycle, 2.22 ± 0.53 L immediately post intervention and 2.44 ± 0.59 L at 6 months follow up. The difference in the FVC score at mid cycle, post intervention and 6 months follow up with baseline value were statistically significant (P value <0.001). The mean FEV1 was 2.15 ± 0.52L pre- intervention, 2.14 ± 1.97L at mid cycle, 2.03 ± 0.53 L post intervention and 2.52 ± 2.02 L at 6 months follow up. The difference in the FEV1 score at post intervention with baseline value (pre-intervention) was statistically significant (P value <0.001). However, the difference in the FEV1 score at 6 months follow up period with baseline value (pre-intervention) was not statistically significant (P value >0.005). Conclusion: HBOT although a safe intervention, it is not totally devoid of complications. Although our study did reveal statistically significant changes in pulmonary function in most of the instances, it did not show any clinically significant changes in pulmonary function with use of HBOT protocol at 2.4 ATA. Studies with larger sample size will be required to ensure evidence based safety of HBOT use.