Pediatric Pulmonology 49:E144–E146 (2014)
Syncope at Altitude: An Enigmatic Case Aliva De,
and Sally L. Davidson Ward, MD
Summary. We report a case of a young boy with recurrent episodes of syncope at elevated altitude. While not conforming to common presentations of altitude sickness, the differential diagnoses and possible etiologies are discussed. Pediatr Pulmonol. 2014; 49:E144–E146. ß 2014 Wiley Periodicals, Inc.
Key words: syncope at altitude; neuro-cardiogenic syncope; altitude related disease in pediatrics. Funding source: none reported.
A 6-year-old boy presented with history of recurrent episodes of syncope during air travel and at altitude since 16 months of age. Symptoms generally occurred 21/2–3 hr after exposure to altitude above 7,000 feet. Episodes were characterized by pallor, peri-oral cyanosis, malaise, and sometimes chest pain. Altered consciousness ensued usually lasting 5–10 min. He became bradycardic at 30–50 bpm with oxygen saturation (SpO2) ranging 80–84% during these episodes. Symptoms resolved with supplemental oxygen or return to sea level and his remaining stay would be uneventful, including normal exercise tolerance and participation in mountain sports. At times, he had normal flight experiences- mostly when flying time was short or cabin pressure was maintained below 7,000 feet. A trial of acetazolamide was ineffective in preventing his symptoms. Review of systems was negative for pulmonary, cardiac, or neurologic disease at sea level. He had a normal physical exam and participated in sports without limitations at sea level. Family history was significant for altitude sickness in father. Because of the repeated, severe nature of his symptoms, supplemental oxygen, and pulse oximetry had been provided for travel. He had a normal electrocardiogram (ECG), echocardiogram, Holter evaluation, CT scan of chest, pulmonary function test, and polysomnogram with continuous PETCO2 monitoring. Hypoxic altitude simulation test at ß 2014 Wiley Periodicals, Inc.
5,000–8,000 feet was normal with SpO2 at 93–94%. Echocardiogram with altitude simulation of 8,000 feet was normal. Around 7 years of age, he was referred to Children’s Hospital Colorado at Denver (altitude 5,471 feet) for further evaluation. ECG, echocardiogram, 24-hr Holter monitoring and an autonomic tilt table test performed there were normal. Subsequently, extended Holter monitoring performed during a family vacation to an altitude of 8,000 feet captured an event. Within 21/2 hr of arrival, while climbing stairs, he felt light-headed, nauseous, and became “glassy eyed.” Pulse oximetry recorded a pulse rate of 54 bpm and SpO2 was 93–94%. He recovered within 10 min of lying down without any supplemental oxygen. Holter download (Fig. 1) revealed a heart rate of 47 bpm lowest with this
Division of Pediatric Pulmonology, Children’s Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, California. Conflict of interest: None.
Correspondence to: Aliva De, MD, Clinical Fellow, Children’s Hospital Los Angeles, 4650 West Sunset Blvd, MS#83, Los Angeles, CA 90036. E-mail: [email protected]
Received 5 December 2013; Accepted 13 April 2014. DOI 10.1002/ppul.23062 Published online 27 May 2014 in Wiley Online Library (wileyonlinelibrary.com).
Syncope at Altitude
Fig. 1. Extended Holter monitoring test at an altitude over 7,000 feet revealed bradycardia with HR 47/min during his symptoms of light-headedness, palor, and glassy eyed appearance. This event was immediately preceded by sinus tachycardia.
event, immediately preceded by sinus tachycardia (heart rate 144 bpm), suggesting a diagnosis of vaso-vagal syncope triggered by sympathetic mechanisms at altitude. Patient was advised to increase salt and fluid intake prior to air travel, monitor SpO2, and use supplemental oxygen as needed. He has done well with these precautions. Over the last 3 years he has had 16 flying episodes, 4 of which were above his trigger point (above 7,300 feet cabin altitude for 2.5 hr or more). He did not have an episode during any of these flights. He has had three trips to the mountains and he had a short episode during one of these trips. DISCUSSION
This is an unusual case of altitude-related syncope triggered by commercial air travel and ascent to moderate altitude levels. Altitude related illnesses generally occur following ascent to greater than 2,500 m (8,000 feet) altitude. Airplane cabins are pressurized at 5,000–8,000 feet.1–3 Altitude-related illnesses include high altitude headache, acute mountain sickness (AMS), high altitude pulmonary edema (HAPE), and high altitude cerebral edema (HACE).4,5 AMS develops within 6–12 hr of arrival to altitude with headache, nausea, dizziness, fatigue, and difficulty sleeping. HAPE is non-cardiogenic pulmonary edema with dry cough, occasional blood tinged sputum, crackles on auscultation, and severe hypoxemia. HACE is associated with progressive altered mental status, coma, and even death. Our patient’s
ABBREVIATIONS: bpm beats per minute ECG electrocardiogram PaCO2 arterial partial pressure of carbon dioxide PETCO2 end-tidal partial pressure of carbon dioxide arterial oxygen saturation SpO2
symptoms were atypical of common altitude illnesses as they were abrupt, transient and resolved without descent. The barometric pressure and partial pressure of inspired oxygen decrease with altitude above sea level.6 Patients with underlying respiratory disease are at higher risk of hypoxemia during air travel and an altitude simulation test can predict the requirement for supplemental oxygen during travel.7 Patients with underlying cardio-pulmonary disease and sleep related breathing disorders are also at higher risk of altitude-related illnesses.8 Pulmonary artery vaso-reactivity can be exacerbated at altitude and unmask an underlying pulmonary arterial hypertension crisis.8–10 There is limited data, mostly in the adult literature on syncope at altitude and a possible neuro-cardiogenic mechanism has been described.11,12 Several physiological adaptations in the respiratory, neurological, hematological, cardiovascular, and autonomic systems take place as a result of exposure to hypobaric hypoxia. Ventilatory response increases via peripheral chemoreceptors, thus lowering PaCO2 (hypocapnia), which in turn can inhibit ventilation. Respiratory alkalosis gradually leads to renal compensation by bicarbonate diuresis.13 Over time, PaCO2 and Hþ ions increase, stimulating central chemoreceptor-mediated ventilatory drive. Hypobaric hypoxia also stimulates vasodilatation and consequent sympathetic reflex over-activity and this increases heart rate, maintains blood pressure, and adequate oxygen delivery.14,15 Volume depletion with diuresis, decreased fluid intake and increased physical activity at altitude additionally contribute to sympathetic over-activity.11 The sympathetic overactivity is typically accompanied by a parasympathetic withdrawal. Syncope at altitude appears to be a vasovagal response from abnormal parasympathetic activation and reflex bradycardia following such sympathetic triggering.11,12,16 The reflex bradycardia is thought to be mediated by the Bezold– Jarisch reflex.12,16 Hypocapnia, cerebral vasoconstriction and decreased cerebral blood flow, in addition, may also Pediatric Pulmonology
De and Davidson Ward
contribute to syncope.11 In our patient, the phenomenon of vasovagal syncope was eventually demonstrated during Holter recording at altitude, supporting the utility of this test in unmasking autonomic variations. Our patient also reported to have decreased SpO2 of 80–84% during his events. In healthy individuals, arterial oxygen tension (PaO2) at 8,000 feet altitude is expected to fall to about 60–75 mmHg, and the corresponding SpO2 measured by pulse oximetry would be around 89–94%.17 A decrease in the cardiac output associated with parasympathetic response could account for the further decrease in oxygen saturation in our patient. In addition, our patient’s episodes began at a young age (16 months) and a contribution from decreased pulmonary reserve due to immaturity is also likely. The gradual improvement of his symptoms with time supports this possibility. In general, altitude related disorders have a similar rate of occurrence in children and adults.8,18 Syncope at altitude has been described in adult populations.11,12 There are aviation reports of pilots experiencing near syncopal events during flight as well as during routine aviation physiology testing under hypoxic exposure.16,19 These events typically occur at higher altitudes than experienced by our young patient, though the underlying mechanism appears to be similar. There is limited data in the literature of this condition in the pediatric population. This may be due to age related factors or differences in altitude exposure among children and adults. Our patient responded to the prophylactic precautions of increased salt and fluid intake to alleviate his symptoms. This is a relatively simple intervention and may be an empiric option for other non-specific altitude related symptoms among travelers. CONCLUSION
This case presents a rare manifestation of altituderelated illness in a child and a discussion of the possible physiologic mechanisms. There has been an increased frequency of air travel and mountain recreational activities in recent years. A clinical and logical approach to guiding families for travel has been proposed.8,18 Altitude-related syncope has not been described in children, but does not preclude its occurrence in this population and knowledge of this condition is important for pediatricians and pulmonologists. ACKNOWLEDGMENTS
We would like to acknowledge the contributions of Dr. Dunbar Ivy and Dr. Michael Yaron at University of Colorado, Denver School of Medicine for their contribution to the care of this patient.
REFERENCES 1. Aerospace Medical Association, Aviation Safety Committee, Civil Aviation Subcommittee. Cabin cruising altitudes for regular transport aircraft. Aviat Space Environ Med 2008;79:433–439. 2. Hampson NB, Kregenow DA, Mahoney AM, Kirtland SH, Horan KL, Holm JR, Gerbino AJ. Altitude exposures during commercial flight: a reappraisal. Aviat Space Environ Med 2013;84:27–31. 3. Cocks R, Liew M. Commercial aviation in-flight emergencies and the physician. Emerg Med Australas EMA 2007;19:1–8. doi: 10.1111/j.1742-6723.2006.00928.x 4. Rodway GW, Hoffman LA, Sanders MH. High-altitude-related disorders–Part I: pathophysiology, differential diagnosis, and treatment. Heart Lung J Crit Care 2003;32:353–359. doi: 10.1016/ j.hrtlng.2003.08.002 5. Imray C, Booth A, Wright A, Bradwell A. Acute altitude illnesses. BMJ 2011;343:d4943. 6. West JB. High-altitude medicine. Am J Respir Crit Care Med 2012;186:1229–1237. doi: 10.1164/rccm.201207-1323CI 7. Tzani P, Pisi G, Aiello M, Olivieri D, Chetta A. Flying with respiratory disease. Respir Int Rev Thorac Dis 2010;80:161–170. doi: 10.1159/000313425 8. Pollard AJ, Niermeyer S, Barry P, Ba¨rtsch P, Berghold F, Bishop RA, Clarke C, Dhillon S, Dietz TE, Durmowicz A, et al. Children at high altitude: an international consensus statement by an ad hoc committee of the International Society for Mountain Medicine, March 12, 2001. High Alt Med Biol 2001;2:389–403. doi: 10.1089/15270290152608561 9. Sylvester JT, Shimoda LA, Aaronson PI, Ward JPT. Hypoxic pulmonary vasoconstriction. Physiol Rev 2012;92:367–520. doi: 10.1152/physrev.00041.2010 10. Das BB, Wolfe RR, Chan K-C, Larsen GL, Reeves JT, Ivy D. High-altitude pulmonary edema in children with underlying cardiopulmonary disorders and pulmonary hypertension living at altitude. Arch Pediatr Adolesc Med 2004;158:1170–1176. doi: 10.1001/archpedi.158.12.1170 11. Nicholas R, O’Meara PD, Calonge N. Is syncope related to moderate altitude exposure? JAMA J Am Med Assoc 1992;268: 904–906. 12. Freitas J, Costa O, Carvalho MJ, Falca˜o de Freitas A. High altituderelated neurocardiogenic syncope. Am J Cardiol 1996;77:1021. 13. Sandberg C, Naylor J. Respiratory physiology at altitude. J R Army Med Corps 2011;157:29–2932. 14. Naeije R. Physiological adaptation of the cardiovascular system to high altitude. Prog Cardiovasc Dis 2010;52:456–466. doi: 10.1016/j.pcad.2010.03.004 15. Hughson RL, Yamamoto Y, McCullough RE, Sutton JR, Reeves JT. Sympathetic and parasympathetic indicators of heart rate control at altitude studied by spectral analysis. J Appl Physiol (1985) 1994;77:2537–2542. 16. Chiang K-T, Yang C-S, Chiou W-Y, Chu H. Repeated hypoxic syncope in a helicopter pilot at a simulated altitude of 18,000 feet. Aviat Space Environ Med 2012;83:609–613. 17. Ahmedzai S, Balfour-Lynn IM, Bewick T, Buchdahl R, Coker RK, Cummin AR, Gradwell DP, Howard L, Innes JA, Johnson AO, et al. Managing passengers with stable respiratory disease planning air travel: British Thoracic Society recommendations. Thorax 2011;66:i1–i30. doi: 10.1136/thoraxjnl-2011-200295 18. Yaron M, Niermeyer S. Travel to high altitude with young children: an approach for clinicians. High Alt Med Biol 2008;9: 265–269. doi: 10.1089/ham.2008.1066 19. Rayman RB, McNaughton GB. Hypoxia: USAF experience 1970– 1980. Aviat Space Environ Med 1983;54:357–359.