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Copyright ©ERS Journals Ltd 2005
Nasal potentials at high altitude
1 Medical Clinic VII, Sports Medicine, University of Heidelberg, Germany. 2 Dept of Critical Care Medicine, University Hospital Wales, Cardiff, UK
To the Editors:
In their recent publication in the European Respiratory Journal, Sartori et al. 1 explain the difference between their results and previous studies by arguing that in other studies "no particular care was taken to locate the electrode in the inferior turbinate", without contacting the investigators who performed the measurements that they criticise. This argument is not acceptable for us. We can assure them that we paid very careful attention to the placement of the nasal electrode as we are well aware that potentials vary considerably in magnitude in different regions of the nose 2, 3. The fact that the magnitude of measured potentials is comparable among all studies at high altitude rules out a significant effect of the site of recording and disproves the argument by Sartori et al. 1.
We would like to make further observations on the discrepant results which are summarised in table 1
. In a study by Mairbäurl et al. 5, performed in 1999 in freezing temperatures and strong winds, subjects reported dryness of the nasal epithelium. This was not a problem in a second study performed in 2003 6 when weather conditions were warm and nasal dryness was prevented with aerosolised isotonic saline. This manoeuvre entirely prevented the hyperpolarisation of total nasal potential difference. Mason et al. 4 and Sartori et al. 1 did not observe a problem with nasal dryness, although the subjects in Mason et al. 4 bathed their nostrils with isotonic saline twice daily. These variations indicate the problems and difficulty of interpretation of nasal potential difference measurements. Mairbäurl et al. 5 found no statistically significant change in the amiloride-sensitive change in the nasal potential difference (NP
amil) in high-altitude pulmonary oedema (HAPE)-susceptible subjects; only a nonsignificant trend was reported, whereas, in another study by Mairbäurl et al. 6, significantly decreased NPamil in HAPE was seen, again pointing to possible effects of nasal dryness. This argument is strengthened by the increase seen in the chloride-sensitive change in the nasal potential difference (NPCl) reported by both Mairbäurl et al. 5 and Mason et al. 4. Increased NPCl is compatible with increased nasal secretion. This possibility was not addressed in the study by Sartori et al. 1.
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In summary, these results indicate that the potential across the nasal epithelium might very well be affected by climatic conditions 7 to which the nose is exposed but to which the alveolar epithelium is not 1, 4. Due to this, particular caution must be exercised when extrapolating data obtained at the nasal epithelium to make claims about changes occurring at the level of the alveolar epithelium.
REFERENCES
- Sartori C, Duplain H, Lepori M, et al. High altitude impairs nasal transepithelial sodium transport in HAPE-prone subjects. Eur Respir J 2004;23:916–920.
[Abstract/Free Full Text] - Knowles MR, Buntin WH, Bromberg PA, Gatzy JT, Boucher RC. Measurements of transepithelial electric potential differences in the trachea and bronchi of human subjects in vivo. Am Rev Respir Dis 1982;126:108–112.[Web of Science][Medline] [Order article via Infotrieve]
- Knowles MR, Carson JL, Collier JT, Gatzy JT, Boucher RC. Measurements of nasal transepithelial electric potential differences in normal human subjects in vivo. Am Rev Respir Dis 1981;124:484–490.[Web of Science][Medline] [Order article via Infotrieve]
- Mason NP, Petersen M, Melot C, et al. Serial changes in nasal potential difference and lung electrical impedance tomography at high altitude. J Appl Physiol 2003;94:2043–2050.
[Abstract/Free Full Text] - Mairbäurl H, Weymann J, Möhrlein A, et al. Nasal epithelium potential difference at high altitude (4559 m): evidence for secretion. Am J Respir Crit Care Med 2003;167:862–867.
[Abstract/Free Full Text] - Mairbäurl H, Bärtsch P, Peth S, et al. Dexamethasone prevents high-altitude pulmonary oedema without effects on nasal potentials. Eur Respir J 2004;24: Suppl. 8 327s
- Canning BJ. Neurology of allergic inflammation and rhinitis. Curr Allergy Asthma Rep 2002;2:210–215.[Medline] [Order article via Infotrieve]
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