A new and simple parameter for diagnosis pulmonary edema: Expiratory air humidity

Acute pulmonary edema is characterized by increased levels of fluid in the interstitial and alveolar space of the lung and requires emergency treatment. In acute pulmonary edema, the amount of fluid in the intra-alveolar, interstitial space, and pleural space vary considerably and this fluid will evaporate in different amounts compared to the physiological fluid. The aim of this study was to compare the humidity rates of expiratory air measured before and after pulmonary edema induced by α-naphthylthiourea (ANTU) in rats.

The study included twenty healthy adult rats divided equally into a healthy control group and a pulmonary edema group. Pulmonary edema was induced by administering ANTU intraperitoneally in the rats in the study group. Humidity, temperature, lung weight, pleural effusion, and histopathological changes in the respiratory system due to pulmonary edema were examined in the ANTU group. Control measurments were taken before administration of ANTU and again 4 h after administration of ANTU when lung damage was considred to be at maximum levels.

Mean expiratory air humidity was 71.22±3.59% before ANTU and 56.28±3.94% after administration of ANTU. The mean humidity difference of -14.94±5.96% was considered statistically different (p = 0.01).

Humidity rate in expiratory air was significantly lower in rats with acute pulmonary edema compared to healthy rats. This result supports the hypothesis that humidity in expiratory air can be considered an important parameter in patients during clinical are follow-up for pulmonary edema.