Background:
Acute respiratory illness carries high morbidity and mortality among patients with severe neurological impairment. Assessment
of acute respiratory decompensation and differentiating it from chronic pathology is a frequently encountered challenge. Partial pressure of CO2 is commonly used as an aid in this setting.
Aim:
To evaluate baseline end tidal CO2 (EtCO2) levels using non-invasive side stream capnometry and to identify factors correlated with higher capnometry readings in this patient population.
Methods:
This was a prospective, cross sectional case controlled study comparing single end tidal CO2 (EtCO2) readings between neurologically impaired patients and healthy controls. Patient's demographic and clinical data were recorded. Variables correlating with higher EtCO2 readings and those that may predict clinically meaningful difference among neurologically impaired patients were evaluated.
Results:
Seventy eight patients and 53 healthy individuals were included. The mean (±SD) EtCO2 values were higher for neurologically impaired patients as compared to healthy individuals (39.14±3.59 and 37.11±1.88 mmHg respectively; p<0.0001), and highest among patients using antipsychotic medications (41.53±5.257 mmHg). Both kyphoscoliosis and use of antipsychotic medications were predictors of higher clinically meaningful EtCO2 difference (kyphoscoliosis with 100% sensitivity; p=0.016, and use of antipsychotics with 84.4% specificity; p=0.01).
Conclusion:
Patients with severe neurological impairment have higher baseline EtCO2 values as compared to healthy individuals. Kyphoscoliosis and the use of antipsychotic medications were found to predict clinically meaningful differences in EtCO2 values. Baseline EtCO2 values may be taken into account while treating this particular population.
