Is a 12-h Nitrox dive hazardous for pulmonary function?
Prolonged exposure to a high partial pressure of oxygen leads to inflammation of pulmonary tissue [pulmonary oxygen toxicity (POT)], which is associated with tracheobronchial irritation, retrosternal pain and coughing, and decreases in vital capacity (VC). The nitric oxide (NO) concentration in exhaled gas (FeNO) has been used as an indicator of POT, but the effect of SCUBA diving on FeNO has rarely been studied. The study presented here aimed to assess alterations to pulmonary function and FeNO following a 12-h dive using breathing apparatus with a relatively high partial pressure of oxygen.
Six healthy, male, non-smoking military SCUBA divers were recruited (age 31.8 ± 2.7 years, height 179 ± 0.09 cm, and body weight 84.6 ± 14 kg). Each diver completed a 12-h dive using a demand-controlled semi-closed-circuit rebreather. During the 12 h of immersion, divers were subjected to 672 oxygen toxicity units (OTU).
A complete pulmonary function test (PFT) was completed the day before and immediately after immersion. FeNO was measured using a Nobreath™ Quark (COSMED™, Rome, Italy), three times for each diver. The first datapoint was collected before the dive to establish the “basal state”, a second was collected immediately after divers emerged from the water, and the final measurement was taken 24 h after the dive.
Despite prolonged inhalation of a hyperoxic hyperbaric gas mixture, no clinical pulmonary symptoms were observed, and no major changes in pulmonary function were detected. However, a major decrease in FeNO values was observed immediately after emersion [0–12 ppb (median, 3.8 ppb)], with a return to baseline [2–60 ppb (median, 26 ppb) 24 h later (3–73 ppb (median, 24.7 ppb)].
These results suggest that if the OTU remain below the recommended limit values, but does alter FeNO, this type of dive does not persistently impair lung function.
KeywordsHyperoxia Diving Pulmonary oxygen toxicity Fractional concentration of exhaled nitric oxide FeNO
Expiratory reserve volume
- FEF 25–75%
Forced expiratory flow 25–75%
Concentration in exhaled nitric oxide
Forced expiratory volume in 1 s
Forced vital capacity
Inspiratory reserve volume
Meter sea water (is a unit of pressure used in underwater diving)
Oxygen toxicity units (OTU)
Peak expiratory flow
Pulmonary function test
Pulmonary oxygen toxicity
Parts per billion
Total lung capacity
Transfer factor for carbon monoxide
Unit pulmonary toxic dose
We thank B. Schmid, Engineer, for his invaluable contribution to this work.
OC, CB and JEB conceptualized and designed the study, performed the experiments, analyzed the data, interpreted the results of experiments, and prepared the figures. OC and JEB drafted, edited, and revised the manuscript. OC, CB and JEB approved the final version of the manuscript.
Compliance with ethical standards
Conflict of interest
The authors have no competing interests to disclose in relation to this study. The results of the present study do not constitute endorsement by the European JAP, and are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation.
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