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Nareg Roubinian, MD, MPH; Paul D. Blanc, MD, MSPH, FCCP; Hubert Chen, MD, MPH, FCCP
Author and Funding Information

From the Department of Medicine (Drs Roubinian, Blanc, and Chen), University of California-San Francisco; and Genentech, Inc (Dr Chen).

Correspondence to: Nareg Roubinian, MD, MPH, University of California-San Francisco, Department of Medicine, 533 Parnassus Ave, Room U127, San Francisco, CA 94143; e-mail: Nareg.Roubinian@ucsfmedctr.org


Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2013;143(3):877. doi:10.1378/chest.12-2898
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Published online
To the Editor:

We thank Dr Smith for his thoughtful comments regarding our recent publication in CHEST (October 2012).1 We took great interest in his recently published findings demonstrating an increase in estimated pulmonary artery pressures in healthy air passengers without hypoxemia.2

In our study, we used an a priori-defined oxygen desaturation value of pulse oxygen saturation (SpO2) <85% (corresponding to partial pressure of oxygen in the blood of approximately 50 mm Hg at sea level). We chose this value to maintain a high specificity for oxygen desaturation events, consistent with this being the recommended threshold for prescribing in-flight supplemental oxygen in individuals, based on altitude simulation testing.3

We agree that a more sensitive threshold for oxygen desaturation may correlate better with flight symptoms and/or pulmonary vasoconstriction events. Using our original threshold of SpO2 <85%, we did not find a significant association between desaturation events and flight symptoms (P = .25). However, we did find that the oxygen saturation nadir was lower in individuals with flight symptoms compared with those without symptoms (SpO2, 85% vs 89%; P = .03). Notably, even when using this more restrictive cutoff for SpO2 of 85%, there were four subjects who remained asymptomatic despite desaturation events.

Using a more sensitive threshold of oxygen desaturation (SpO2 <88%), we found a significant association with flight symptoms (P < .01) and a similar number of individuals with asymptomatic oxygen desaturation. When the threshold was further increased (SpO2 <90%), we saw an even stronger association with flight symptoms, but there was also a substantial increase in the number of individuals with asymptomatic oxygen desaturation by this definition. Therefore, a cutpoint of SpO2 <88% appeared to have the best performance characteristics with respect to reported symptoms.

Dr Smith’s findings, taken together with our study results, imply that even under mildly hypoxic conditions, individuals with underlying pulmonary vascular disease may experience symptoms as a result of elevations in pulmonary artery pressure.1,4 Further studies are needed to better understand the relationship between changes in pulmonary artery pressures, symptoms, and desaturation events during flight, and their implications with regard to air travel safety for patients with pulmonary vascular disease.

References

Roubinian N, Elliott CG, Barnett CF, et al. Effects of commercial air travel on patients with pulmonary hypertension. Chest. 2012;142(4):885-892. [CrossRef] [PubMed]
 
Smith TG, Talbot NP, Chang RW, et al. Pulmonary artery pressure increases during commercial air travel in healthy passengers. Aviat Space Environ Med. 2012;83(7):673-676. [CrossRef] [PubMed]
 
Shrikrishna D, Coker RK; Air Travel Working Party of the British Thoracic Society Standards of Care Committee. Managing passengers with stable respiratory disease planning air travel: British Thoracic Society recommendations. Thorax. 2011;66(9):831-833. [CrossRef] [PubMed]
 
Smith TG, Chang RW, Robbins PA, Dorrington KL. Commercial air travel and in-flight pulmonary hypertension. Aviat Space Environ Med. 2013;84(1):65-67. [CrossRef] [PubMed]
 

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References

Roubinian N, Elliott CG, Barnett CF, et al. Effects of commercial air travel on patients with pulmonary hypertension. Chest. 2012;142(4):885-892. [CrossRef] [PubMed]
 
Smith TG, Talbot NP, Chang RW, et al. Pulmonary artery pressure increases during commercial air travel in healthy passengers. Aviat Space Environ Med. 2012;83(7):673-676. [CrossRef] [PubMed]
 
Shrikrishna D, Coker RK; Air Travel Working Party of the British Thoracic Society Standards of Care Committee. Managing passengers with stable respiratory disease planning air travel: British Thoracic Society recommendations. Thorax. 2011;66(9):831-833. [CrossRef] [PubMed]
 
Smith TG, Chang RW, Robbins PA, Dorrington KL. Commercial air travel and in-flight pulmonary hypertension. Aviat Space Environ Med. 2013;84(1):65-67. [CrossRef] [PubMed]
 
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