Lung mechanics of patients in ICU with COVID-19 similar among those pregnant, not pregnant
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Key takeaways:
- Only one of four respiratory parameters in pregnant women with COVID-19 was significantly different after delivery.
- With this knowledge, general ventilatory settings can be applied to pregnant women.
Compared with mechanical ventilation parameters of nonpregnant patients with critical COVID-19, no difference was found in pregnant women with COVID-19 in the ICU, according to study results published in CHEST.
“We expected to observe some changes in pregnant patient lung mechanics associated with physiological changes of pregnancy,” Daniela N. Vasquez, MD, of Sanatorio Anchorena in Argentina, told Healio. “For example, we expected to find higher plateau pressure in pregnant patients under invasive mechanical ventilation, as a result of the normal decreased chest wall compliance during pregnancy. However, we found no differences between pregnant vs. nonpregnant patient lung mechanics. Additionally, contrary to common belief, pregnant patient lung mechanics did not improve after inducing delivery.”
In a multicenter prospective cohort study, Vasquez and colleagues analyzed 91 women in Argentina or Colombia with COVID-19 who needed ventilatory support and were either admitted to the ICU before or after giving birth to understand their ventilatory parameters and if delivery changes these parameters. They also evaluated risk factors for death in the mother, fetus and neonate.
Characteristics
Of the total cohort, 63 women did not give birth prior to entering the ICU (mean gestation, 29.2 weeks), and the women who gave birth in the ICU did so at an average gestation of 31 weeks. The remainder of the patient population gave birth before entering the ICU at an average of 34 weeks’ gestation.
Delivery was induced in 71 women, with maternal being the reason behind more than half (60.5%) of these deliveries, followed by maternal plus fetal (29.5%) and fetal (9.9%) reasons. Of the pregnant women in the ICU, 43 gave birth there and 14 were discharged without giving birth. The rest of these patients either had a spontaneous abortion (n = 2) or experienced a fetal death (n = 4).
The highest method of ventilatory support varied in the total population, but most patients received invasive mechanical ventilation (n = 69, including 47 pregnant women), followed by high-flow nasal cannula (n = 20) and noninvasive mechanical ventilation (n = 2).
Notably, most patients on invasive mechanical ventilation received neuromuscular blockers (92.7%). Other requirements found in this cohort included tracheostomy (36.2%) and prone positioning (71%), according to researchers.
When assessing the risk for invasive mechanical ventilation, researchers found one significant risk factor: Sequential Organ Failure Assessment score within the first 24 hours (OR = 1.97; 95% CI, 1.29-2.99).
Ventilatory parameters, mortality
At the start of invasive mechanical ventilation in pregnant women, researchers found a median PaO2 to FIO2 ratio of 142 (interquartile range [IQR], 110-176), a mean plateau pressure (PP) of 24.3 cm H2O (standard deviation [SD], ± 4.5 cm H2O), a median static compliance (SC) of 31 mL/cm H2O (IQR, 26-40 mL/cm H2O) and a mean driving pressure (DP) of 12.5 cm H2O (SD, ± 3.3 cm H2O).
To see if these respiratory parameters changed with delivery, researchers accounted for them less than 2 hours prior to delivery, less than 2 hours after delivery and 24 hours after delivery.
Among the studied parameters, median PaO2 to FIO2 ratio (oxygenation) was the only factor that differed significantly before and after delivery in pregnant women on invasive mechanical ventilation. Before delivery, the median PaO2 to FIO2 ratio was 134 (IQR, 100-230), and this went up to 168 (IQR, 136-185) 2 hours or less after delivery and 192 (IQR, 132-232.5) 24 hours after delivery.
On the other hand, mean PP before delivery (25.6 ± 6.6 cm H2O) did not significantly differ from the measurements taken 2 hours or less after delivery (24 ± 6.7 cm H2O) and 24 hours after (24.6 ± 5.2 cm H2O). Mean DP prior to birth (13.6 ± 4.2 cm H2O) also did not differ after birth ( 2 hours after, 12.9 ± 3.9 cm H2O; 24 hours after, 13 ± 4.4 cm H2O).
Further, median SC showed no significant difference from before birth (28 mL/cm H2O; IQR, 22.5-39 mL/cm H2O) to either time after birth ( 2 hours after, 30 mL/cm H2O; IQR, 24.5-44 mL/cm H2O; 24 hours after, 30 mL/cm H2O; IQR, 24.5-44 mL/cm H2O). The lack of difference in respiratory parameters before and after birth was unexpected, Vasquez told Healio.
When assessing mortality, researchers observed 16 maternal deaths — all in those receiving invasive mechanical ventilation — and identified BMI (OR = 1.1; 95% CI, 1.006-1.204) and having a comorbidity (OR = 4.15; 95% CI, 1.212-14.2) as significant risk factors for this outcome. In the observed 14 fetal/neonatal losses, significant risk factors differed from those found for maternal mortality and included gestational age at delivery (OR = 0.67; 95% CI, 0.52-0.86) and Sequential Organ Failure Assessment score within the first 24 hours (OR = 1.53; 95% CI, 1.13-2.08).
“This study offers two main takeaways for clinicians,” Vasquez told Healio. “First, ventilator setting will not change for pregnant patients in ICU. Setting proven to reduce mortality can be trusted for pregnant patients as well. Second, pregnant patients with viral pneumonia under invasive mechanical ventilation can continue pregnancy. Interrupting pregnancy does not improve maternal outcomes and can jeopardize fetal wellbeing.”
In terms of future studies, Vasquez said pregnant women need to be included more to guarantee favorable maternal outcomes.
“More data collection is necessary for this population to ensure they receive the best possible care,” she told Healio.
This study by Vasquez and colleagues presents important findings on mechanical ventilation parameters in pregnant women after they have delivered a baby and brings attention to how physicians should treat pregnant women in a critical care setting, according to an accompanying editorial by Stephen E. Lapinsky, MB, site director and education director of the ICU at Mount Sinai Hospital, and Julien Viau-Lapointe, MD, of Hôpital Maisonneuve-Rosemont.
“Although there is a natural tendency for intensive care physicians to seek to remove the complicating factor of a gestation in critically ill pregnant patients, this cannot be justified by the assumption that delivery will improve maternal well-being,” Lapinsky and Viau-Lapointe wrote. “Any surgical procedure carries risks, particularly in the unstable patient with severe ARDS. Our suggestion is to deliver only for usual obstetric indications, which may include fetal distress caused by maternal hypoxemia. Finally, we think it is important to reiterate a big picture mantra overarching the treatment of the ill pregnant patient: ‘Treat a pregnant woman as you would a nonpregnant woman, unless there is a clear reason not to.’”
For more information:
Daniela N. Vasquez, MD, can be reached at daniela.vasquez@alumni.utoronto.ca.