Asthma patients with hypocapnia see higher mortality rates, need for intubation
Click Here to Manage Email Alerts
Key takeaways:
- Hypocapnia patients had an intubation rate of 41%.
- They also had an in-hospital mortality rate of 27.7%
- There was no significant association in length of ICU stay.
BOSTON — ICU patients with comorbid asthma with hypocapnia showed a significantly higher in-hospital mortality rate and intubation requirement than patients without hypocapnia, according to an abstract presented at the CHEST Annual Meeting.
“Asthma exacerbations that lead to ICU admissions are serious and carry a significant risk of morbidity and mortality,” Sergio Andres Vallejo Avila, MD, internal medicine resident at UT Health San Antonio, told Healio.
“Despite advancements in asthma management, we still lack clear, independent prognostic markers that could help predict which patients are at the highest risk for poor outcomes,” he continued. “Our aim with this study was to explore whether specific markers like arterial carbon dioxide (PaCO2) levels could serve as early indicators of risk in critically ill asthma patients.”
This observational study included data from the MIMIC-IV database. It looked at patients admitted to the ICU departments at Beth Israel Deaconess Medical Center between 2008 and 2019 with an asthma diagnosis.
Based on their carbon dioxide (CO2) levels, these patients were then stratified into two groups. The first group included patients with hypocapnia (CO2 < 35 mmHg), and the second included patients without hypocapnia (CO2 35 mmHg).
Among the 1,364 patients in the study, 120 (9.5%) had hypocapnia (median age, 63 years; 51.8% female) and 1,232 (90.5%) did not have hypocapnia (median age, 65 years; 48.8% female). Hypocapnia patients had a median CO2 level of 32 mmHg (interquartile range [IQR], 28.7-34) whereas non-hypocapnia patients had a CO2 level of 47 mmHg (IQR, 43-54).
The hypocapnia patients also had a Charlson Comorbidity Index (CCI) score of 6 (IQR, 3-8) and a Sequential Organ Failure Assessment (SOFA) score of 5 (IQR, 2-9), and non-hypocapnia patients had a CCI of 5 (IQR, 3-7) and a SOFA score of 5 (IQR, 3-8).
Hypocapnia patients had significantly higher in-hospital mortality rates compared with non-hypocapnia patients (27.7% vs. 11.5%; P = .001) as well. They also had a higher intubation rate (41% vs. 21.8%; P = .001). There was no significant difference in the length of an ICU stay between the two groups.
“We found that patients with hypocapnia (CO2 < 35 mmHg) at the time of ICU admission had significantly higher in-hospital mortality rates compared to those with normal or elevated CO2 levels,” Vallejo Avila said.
“Hypocapnia was also associated with a higher likelihood of requiring intubation. This indicates that low PaCO2 levels, commonly seen as part of respiratory failure, may actually be an independent marker of more severe disease in this population,” he said.
Vallejo Avila further emphasized that the study challenges the traditional understanding of hypocapnia as a compensatory mechanism during respiratory distress. It found hypocapnia to be a marker of worse outcomes, indicating that these patients may need more aggressive monitoring and treatment early in their ICU course to avoid fatal outcomes.
“Recognizing this as a risk factor for increased mortality and intubation should encourage closer monitoring and possibly more aggressive interventions, such as earlier ventilatory support,” he said. “Understanding that hypocapnia could indicate more severe disease may lead to earlier interventions that could improve outcomes.”
This study represents an important first step in identifying specific risk factors for ICU-admitted asthma patients, according to Vallejo Avila.
“While these are early findings, they hold the potential to form the basis of a scoring system that could help clinicians stratify patients based on their individual risk profiles,” he said. “Such a tool could allow for more personalized care, where patients at higher risk of poor outcomes (due to markers like low PaCO2 or eosinophilia) receive more aggressive treatment from the start.”