Acute Respiratory Failure in Pregnancy: Clinical Presentation and Diagnosis

Introduction

• Acute respiratory failure is estimated to affect 15-130/100,000 deliveries or 0.1-0.3% of pregnancies.^1-4
• Pregnancy may predispose patients to developing ARDS secondary to increased blood volume, decreased oncotic pressure, upregulation of the inflammatory response, and increased capillary leak.⁵
• Perinatal morbidity and mortality are increased in pregnancies associated with maternal respiratory failure.¹

Clinical Presentation

• Presenting signs and symptoms include cough, dyspnea, fatigue, and fever.
• Physical exam findings may be significant for tachypnea, use of accessory respiratory muscles, crackles and/or wheezing on lung auscultation, hypoxia, and altered mental status.
• Vital sign changes may include tachycardia, hypotension in the setting of infection, increased respiratory rate, and hypoxemia (oxygen saturation < 95%).
• Laboratory changes may include hypercarbia (PaCO₂ > 40 mmHg) and/or hypoxemia (PaO₂ < 75 mmHg). Patients may exhibit early hypocarbia (PaCO₂ < 28 mmHg) with tachypnea, which can evolve into hypercarbia as they begin to tire.

Clinical Diagnosis

ARDS Definition

The Berlin criteria for ARDS include the following:^2,3

• Acute onset <7d between risk factor exposure and the development of ARDS
• Abnormal chest imaging (bilateral infiltrates on chest x-ray not fully attributed to cardiac effusions, lobar collapse, or nodule)
• Exclusion of pulmonary edema
• Oxygenation deficits:
  • Mild: PaO₂:FiO₂ (P:F ratio) 200 to <300 mmHg with PEEP or CPAP ≥5 cmH₂O
  • Moderate: P:F ratio 100 to <200 mmHg with PEEP or CPAP ≥5 cmH₂O
  • Severe: P:F ratio ≥100 mmHg with PEEP or CPAP ≥5 cmH₂O

Differential Diagnosis

Initial Management

• Oxygen supplementation to maintain a goal oxygen saturation of ≥ 92% (ideally >95% due to higher oxygen consumption and lower respiratory reserve).
  Awake, passive prone positioning is recommended in pregnant patients if feasible and may reduce the risk of intubation.⁵
• Advanced interventions and obstetric management are discussed in Part II of this summary.

Long-Term Outcomes

• Mortality rates vary across studies from 25-60% in older studies, with newer studies suggesting improved outcomes and mortality rates closer to 5-10%.⁵
• Mortality risk is associated with a prolonged need for mechanical ventilation, renal failure requiring renal replacement therapy, liver failure, amniotic fluid embolism, septic emboli, and puerperal infection.
• ICU admission is associated with reduced maternal quality of life at 6 months.
• Psychological support is recommended for patients who have had pregnancies complicated by perinatal morbidity and/or mortality or significant organ failure requiring advanced therapies (hemodialysis, invasive ventilation, extracorporeal membrane oxygenation) to support long-term mental health, given the high risk of anxiety, depression, and posttraumatic stress syndrome.