Swimming-induced pulmonary edema
Other namesSwimming-induced pulmonary oedema,[1] pulmonary oedema of immersion

Swimming induced pulmonary edema (SIPE), also known as immersion pulmonary edema, is a life threatening condition that occurs when fluids from the blood leak abnormally from the small vessels of the lung (pulmonary capillaries) into the airspaces (alveoli).[2][3]

SIPE usually occurs during exertion in conditions of water immersion, such as swimming and diving. With the recent surge in popularity of triathlons and swimming in open water events there has been an increasing incidence of SIPE. It has been reported in scuba divers,[4][5] apnea (breath hold) free-diving competitors,[6] combat swimmers, and triathletes.[2] [7] The causes are incompletely understood as of 2010.[2][8][9] Some authors believe that SIPE may be the leading cause of death among recreational scuba divers, but there is insufficient evidence at present.[3]

Signs and symptoms

As with other forms of pulmonary edema, the hallmark of SIPE is a cough which may lead to frothy or blood-tinged sputum. Symptoms include:

Risk factors

It has been described in scuba divers, long-distance swimmers, and breath-hold divers.[11][7]


Immersion causes increased external hydrostatic pressure, leading to redistribution of blood from the periphery to the chest, which increases cardiac filling pressures and stroke volume, and also reduces total lung capacity. There is a movement of fluid from the alveolar capillaries into the alveoli and extravascular lung tissues, which increases with time, and is normal in healthy humans when immersed.[2][4][5][6][8][9][3] This is normally counteracted by the release of BNP which causes sodium and water excretion through the kidneys. This natriuresis is slow, so lung water increase is to some extent normal, but in susceptible people a higher rate of accumulation produces symptoms of SIPE[3]

The alveoli of the lungs fill with edema fluid, causing dyspnoea, cough and frothy or bloodstained sputum. Gas exchange is affected, and as hypoxia increases there may be a loss of consciousness. Oxygenation in divers may be affected by breathing gas mix and partial pressure reduction due to ascent. In severe cases hypoxia may cause cardiac arrest and death. Research continues into the various factors causing IPO.[3]

Possible aggravating factors include:

SIPE is believed to arise from some combinations of these factors, which overwhelms the ability of the body to compensate, and leads to alveolar flooding.[2][8][9]


Acute onset of breathing problems caused by fluid accumulation in lung extravascular spaces induced by immersion, usually in cold water, often with intense physical exertion. Symptoms reported developed during physical activity and usually include dyspnoea/shortness of breath and a cough, often haemoptysis, occasionally chest tightness, chest pain or confusion. Auscultation shows crackles or wheezing. Oxygen saturation usually shows hypoxemia. In most cases chest radiological examination shows signs of pulmonary edema, but a significant minority have a normal initial chest X-Ray. [3]

Rapid resolution of initial signs and symptoms within 48 hours is typical. Symptoms usually resolve spontaneously after the physiologic environment has been normalised by removal from immersion to a warm environment, with supportive treatment.[3]



Management has generally been reported to be conservative, though deaths have been reported.[5][7]


The majority of cases rapidly resolve symptoms within 48 hours.[16] There is a significant risk of further episodes under similar conditions. Investigation for other cardiac problems is indicated.[3] In some cases a medical condition predisposing to SIPE can be corrected, and in some other cases divers who have had SIPE have resumed diving against medical advice.[3]


SIPE is estimated to occur in 1-2% of competitive open-water swimmers, with 1.4% of triathletes,[2] 1.8% of combat swimmers and 1.1% of divers and swimmers[4] reported in the literature. Fatal cases can be mistaken for drowning because in both SIPE and drowning the lungs are heavy and filled with fluid, so post mortem findings may be similar. Consequently, most information about this condition comes from survivors and the true incidence is uncertain and likely to be underreported.[3]


Most of the medical literature on the topic comes from case series in military populations and divers,[4] and an epidemiological study in triathletes.[2] A recent experimental study showed increased pulmonary artery pressure with cold water immersion, but this was done in normal subjects rather than in people with a history of SIPE.[17] A study in SIPE-susceptible individuals during submersion in cold water showed that pulmonary artery and pulmonary artery wedge pressures were higher than in non-susceptible people. These pressures were reduced by Sildenafil.[15] SIPE may also be a cause of death during triathlons.[18]


  1. ^ 'Oedema' is the standard form defined in the Concise Oxford English Dictionary (2011), with the precision that the spelling in the United States is 'edema'.
  2. ^ a b c d e f g h i j k l m n o p q Miller III, Charles C.; Calder-Becker, Katherine; Modave, Francois (2010). "Swimming-induced pulmonary edema in triathletes". The American Journal of Emergency Medicine. 28 (8): 941–6. doi:10.1016/j.ajem.2009.08.004. PMID 20887912.
  3. ^ a b c d e f g h i j k l m n o p q r s t u v w "Immersion Pulmonary Oedema". www.ukdmc.org. UK Diving Medical Committee. Retrieved 6 June 2022.
  4. ^ a b c d e f Pons, M; Blickenstorfer, D; Oechslin, E; Hold, G; Greminger, P; Franzeck, UK; Russi, EW (1995). "Pulmonary oedema in healthy persons during scuba-diving and swimming". The European Respiratory Journal. 8 (5): 762–7. doi:10.1183/09031936.95.08050762. PMID 7656948. S2CID 35365328. [unreliable medical source?]
  5. ^ a b c d e f Henckes, A; Lion, F; Cochard, G; Arvieux, J; Arvieux, C (2008). "L'œdème pulmonaire en plongée sous-marine autonome : fréquence et gravité à propos d'une série de 19 cas" [Pulmonary oedema in scuba-diving: frequency and seriousness about a series of 19 cases]. Annales Françaises d'Anesthésie et de Réanimation (in French). 27 (9): 694–9. doi:10.1016/j.annfar.2008.05.011. PMID 18674877.
  6. ^ a b c d Liner, M. H.; Andersson, J. P. A. (2008). "Pulmonary edema after competitive breath-hold diving". Journal of Applied Physiology. 104 (4): 986–90. CiteSeerX doi:10.1152/japplphysiol.00641.2007. PMID 18218906. [unreliable medical source?]
  7. ^ a b c d e f g h Kumar, Manish; Thompson, Paul D. (2019-04-03). "A literature review of immersion pulmonary edema". The Physician and Sportsmedicine. 47 (2): 148–151. doi:10.1080/00913847.2018.1546104. ISSN 0091-3847. PMID 30403902. S2CID 53209012.
  8. ^ a b c d e f g h i j k Koehle, Michael S; Lepawsky, Michael; McKenzie, Donald C (2005). "Pulmonary Oedema of Immersion". Sports Medicine (review). 35 (3): 183–90. doi:10.2165/00007256-200535030-00001. PMID 15730335. S2CID 2738792.
  9. ^ a b c d e f g h i j Yoder, JA; Viera, AJ (2004). "Management of swimming-induced pulmonary edema". American Family Physician. 69 (5): 1046, 1048–9. PMID 15023003.
  10. ^ a b c Watson, Jim; Peddie, Ben, eds. (October 2021). "BSAC Annual Diving Incident Report 2020" (PDF). www.bsac.com. British Sub-Aqua Club.
  11. ^ Koehle, MS; Lepawsky, M; McKenzie, DC (2005). "Pulmonary oedema of immersion". Sports Medicine. 35 (3): 183–90. doi:10.2165/00007256-200535030-00001. PMID 15730335. S2CID 2738792.
  12. ^ Pollock, Neal W. (2016). Pollock, NW; Sellers, SH; Godfrey, JM (eds.). Factors in Decompression Stress (PDF). Rebreathers and Scientific Diving. Proceedings of NPS/NOAA/DAN/AAUS June 16–19, 2015 Workshop. Wrigley Marine Science Center, Catalina Island, CA. pp. 145–162.
  13. ^ Little, W (2001). "Hypertensive pulmonary oedema is due to diastolic dysfunction". European Heart Journal. 22 (21): 1961–4. doi:10.1053/euhj.2001.2665. PMID 11603900.
  14. ^ Almuntaser, Ibrahim; Mahmud, Azra; Brown, Angie; Murphy, Ross; King, Gerard; Crean, Peter; Feely, John (2009). "Blood Pressure Control Determines Improvement in Diastolic Dysfunction in Early Hypertension". American Journal of Hypertension. 22 (11): 1227–31. doi:10.1038/ajh.2009.173. PMID 19763121.
  15. ^ a b Moon, Richard E.; Martina, Stefanie D.; Peacher, Dionne F.; Potter, Jennifer F.; Wester, Tracy E.; Cherry, Anne D.; Natoli, Michael J.; Otteni, Claire E.; Kernagis, Dawn N. (2016-03-08). "Swimming-Induced Pulmonary EdemaCLINICAL PERSPECTIVES". Circulation. 133 (10): 988–996. doi:10.1161/CIRCULATIONAHA.115.019464. ISSN 0009-7322. PMC 5127690. PMID 26882910.
  16. ^ Grünig, Hannes; Nikolaidis, Pantelis T.; Moon, Richard E.; Knechtle, Beat (31 August 2017). "Diagnosis of Swimming Induced Pulmonary Edema—A Review". Frontiers in Physiology. 8: 652. doi:10.3389/fphys.2017.00652. PMC 5583207. PMID 28912730.
  17. ^ Wester, T. E.; Cherry, A. D.; Pollock, N. W.; Freiberger, J. J.; Natoli, M. J.; Schinazi, E. A.; Doar, P. O.; Boso, A. E.; Alford, E. L. (2008). "Effects of head and body cooling on hemodynamics during immersed prone exercise at 1 ATA". Journal of Applied Physiology. 106 (2): 691–700. doi:10.1152/japplphysiol.91237.2008. PMID 19023017. S2CID 13339293.
  18. ^ Moon, Richard E.; Martina, Stefanie D.; Peacher, Dionne F.; Kraus, William E. (2016-08-01). "Deaths in triathletes: immersion pulmonary oedema as a possible cause". BMJ Open Sport & Exercise Medicine. 2 (1): e000146. doi:10.1136/bmjsem-2016-000146. ISSN 2055-7647. PMC 5117085. PMID 27900191. Open access icon