Respiratory failure, ventilation and massive pulmonary embolism in pregnancy

It is 02:05, two hours after an uneventful caesarean. The midwife calls you to the recovery bay: the woman has collapsed, she is cyanosed, her blood pressure is unrecordable, and her oxygen saturation will not rise. The single most important thought in your head is pulmonary embolism — because the treatment that saves her (thrombolysis) is the one most often delayed. This topic is the rehearsal for that minute.^[3][8]

Overview and definition

Respiratory failure in pregnancy is failure to oxygenate (type 1, a PaO₂ under 8 kPa or 60 mmHg) or to ventilate (type 2, a PaCO₂ over 6.5 kPa or 50 mmHg), judged against the altered normal values of pregnancy. The causes span the obstetric (aspiration, amniotic fluid embolism, pulmonary oedema of pre-eclampsia) and the general (asthma, pneumonia, ARDS from sepsis or haemorrhage, and massive pulmonary embolism).^[6]

Massive (high-risk) pulmonary embolism is PE with haemodynamic instability — sustained hypotension, obstructive shock, or cardiac arrest. The 2019 European Society of Cardiology guidelines define three presentations that constitute high-risk PE: cardiac arrest, obstructive shock, and persistent hypotension.^[3][8]

Venous thromboembolism remains a leading direct cause of maternal death, and pregnancy is a hypercoagulable state — Virchow's triad of venous stasis, endothelial injury and increased clotting factors, with the risk greatest in the first postpartum week.^[5]

References12ShowHide

1. [1]Brower RG, Matthay MA, Morris A, et al. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome N Engl J Med, 2000.PMID 10793162
2. [2]Guérin C, Reignier J, Richard JC, et al. Prone positioning in severe acute respiratory distress syndrome N Engl J Med, 2013.PMID 23688302
3. [3]Konstantinides SV, Meyer G, Becattini C, et al. 2019 ESC Guidelines for the diagnosis and management of acute pulmonary embolism developed in collaboration with the European Respiratory Society (ERS) Eur Heart J, 2020.PMID 31504429
4. [4]Leung AN, Bull TM, Jaeschke R, et al. An official American Thoracic Society/Society of Thoracic Radiology clinical practice guideline: evaluation of suspected pulmonary embolism in pregnancy Am J Respir Crit Care Med, 2011.PMID 22086989
5. [5]ACOG Practice Bulletin No. 196: Thromboembolism in Pregnancy Obstet Gynecol, 2018.PMID 29939938
6. [6]Feuer D, Shivakumar V, Abu-Rmaileh M, et al. Clinical approach to respiratory failure in the obstetric patient: a comprehensive clinical review Proc (Bayl Univ Med Cent), 2025.PMID 40821480
7. [7]Ejikeme C, Nandakumar V, Gotur D Respiratory physiological changes in pregnancy Respir Med, 2025.PMID 40614834
8. [8]Ebner M, Sentler C, Harjola VP, et al. Outcome of patients with different clinical presentations of high-risk pulmonary embolism Eur Heart J Acute Cardiovasc Care, 2021.PMID 34125186
9. [9]Kislovskiy Y, Hauspurg A, Donadee C, et al. Lung Protective Ventilation during Pregnancy: An Observational Cohort Study AJP Rep, 2024.PMID 38646587
10. [10]Guérin C, Papazian L, Reignier J, et al. Effect of driving pressure on mortality in ARDS patients during lung protective mechanical ventilation in two large randomised controlled trials Crit Care, 2016.PMID 27894328
11. [11]Karakosta A, Evangelou T, Flindris S, et al. Systemic Thrombolysis for Treatment of Acute Life-threatening Pulmonary Embolism During Cesarean Section In Vivo, 2023.PMID 36593053
12. [12]Söderberg M, Smedberg E, Lindqvist PG Cardiac Arrest Due to out-of-Hospital Pulmonary Embolism During Pregnancy: Successful Thrombolysis Eur J Case Rep Intern Med, 2023.PMID 37304997