Respiratory Distress in Pregnancy

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Kami Hu
Kami Hu
EM/IM/CC doc at the University of Maryland. Resuscitationist, educator, low-key philomath, mom.

Pregnant Patients with Respiratory Distress

The charge nurse grabs you – “I’ve got a pregnant lady with respiratory distress going to room 2, I think she might need a tube.”

Your heart rate should pick up a little to deal with this one. But if you maintain a healthy respect for the airway and remember the following tips, you might end up saving two lives (and your scrub bottoms).

 

 

The airway of a pregnant patient is a difficult airway

Estrogen promotes neovascularization, which in combination with increased fluid retention from a more active RAAS and smooth muscle relaxation due to progesterone, causes airway edema and narrowing. Progesterone also decreases gastroesophageal sphincter tone and contributes to delayed gastric emptying, increasing the risk of aspiration. These airways are smaller and more likely to bleed with instrumentation, so getting it on your first pass is even more important than usual.

 

Pregnant patients have decreased pulmonary reserve and increased metabolic demand and oxygen utilization

The oxygen utilization of the pregnant female is increased by approximately 30% due to higher metabolic activity and fetal needs. Pregnant women have a decreased FRC (functional residual capacity); the gravid uterus displaces the diaphragm upward while enlarged breasts can compress the chest, especially if the patient is lying supine. They can and will desaturate rapidly on you once paralyzed.

 

 

The oxygenation and ventilation goals for pregnant women are different than the general population

The increased oxygen demand and needs of the fetus mandate a higher oxygenation goal than usual and a PaO2 of >70 mmHg, corresponding to a SaO2 >94%, is recommended to avoid fetal bradycardia due to increased reliance on anaerobic metabolism and resultant acidemia. The hyperventilation of pregnancy and the need for a CO2 concentration gradient to help offload fetal CO2 into the maternal circulation leads to a lower PCO2, and the documented occurrence of fetal acidosis with extremes of maternal CO2 mandate that physicians try to achieve a goal PCO2 of around 30 mmHg.

 

 

The use of noninvasive positive pressure is not contraindicated

Due to the risks of aspiration mentioned above, the use of continuous or bilevel positive pressure has previously been thought to be contraindicated. However, noninvasive ventilation is a viable method to stabilize these patients and potentially avoid intubation as long as the patient is alert and able to protect their airway.

Tips for Management: 

  • Noninvasive ventilation is not contraindicated due to pregnancy alone. Depending on etiology for respiratory failure, it can be attempted if the patient is alert and able to protect her airway. Consider higher PEEPs if needed (8-10 cmH20) in 3rd-trimester patients to recruit lung compressed by the upwardly-displaced diaphragm.
  • The most experienced provider should intubate for a higher chance of first-pass success, in order to avoid a bloody airway and worsened visualization after failed attempt(s).
  • Use a smaller than usual size endotracheal tube. I recommend starting with a 7.0 but having a 6.5 or even 6.0 tube ready as a back-up.
  • Utilize apneic oxygenation and keep the patient’s head elevated in order to help prevent rapid desaturations when apneic.
  • Target a PaO2 of 70 mmHg and/or saturation of 95% or greater, and a PaCO2 of approximately 30 mmHg. Recognize that a PaCO2 of 40 mmHg, although considered normal in the general population, is an indicator of likely hypercapnic respiratory failure in pregnant women.

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