The correlation and level of agreement between end-tidal and blood gas pCO(2 )in children with respiratory distress: a retrospective analysis

BACKGROUND: To investigate the correlation and level of agreement between end-tidal carbon dioxide (EtCO(2)) and blood gas pCO(2 )in non-intubated children with moderate to severe respiratory distress. METHODS: Retrospective study of patients admitted to an intermediate care unit (InCU) at a tertiary care center over a 20-month period with moderate to severe respiratory distress secondary to asthma, bronchiolitis, or pneumonia. Patients with venous pCO(2 )(vpCO(2)) and EtCO(2 )measurements within 10 minutes of each other were eligible for inclusion. Patients with cardiac disease, chronic pulmonary disease, poor tissue perfusion, or metabolic abnormalities were excluded. RESULTS: Eighty EtCO(2)-vpCO(2 )paired values were available from 62 patients. The mean ± SD for EtCO(2 )and vpCO(2 )was 35.7 ± 10.1 mmHg and 39.4 ± 10.9 mmHg respectively. EtCO(2 )and vpCO(2 )values were highly correlated (r = 0.90, p < 0.0001). The correlations for asthma, bronchiolitis and pneumonia were 0.74 (p < 0.0001), 0.83 (p = 0.0002) and 0.98 (p < 0.0001) respectively. The mean bias ± SD between EtCO(2 )and vpCO(2 )was -3.68 ± 4.70 mmHg. The 95% level of agreement ranged from -12.88 to +5.53 mmHg. EtCO(2 )was found to be more accurate when vpCO(2 )was 35 mmHg or lower. CONCLUSION: EtCO(2 )is correlated highly with vpCO(2 )in non-intubated pediatric patients with moderate to severe respiratory distress across respiratory illnesses. Although the level of agreement between the two methods precludes the overall replacement of blood gas evaluation, EtCO(2 )monitoring remains a useful, continuous, non-invasive measure in the management of non-intubated children with moderate to severe respiratory distress.