Pulmonary Functions in Children Ventilated for Acute Hypoxemic Respiratory Failure*

Objective: To assess pulmonary functions of children who received mechanical ventilation for acute hypoxemic respiratory failure. Design: Longitudinal study. Setting: PICU and Pediatric Pulmonology Clinic of a tertiary care teaching hospital in North India. Patients: All children, 5-12 years old, ventilated for acute hypoxemic respiratory failure in PICU from July 2012 to June 2013 and survived. Interventions: The baseline admission variables recorded were as follows: age, sex, duration of illness, primary diagnosis at admission, Pediatric Risk of Mortality III score, lung injury score, mechanical ventilation parameters, oxygenation indices, and duration of PICU stay. The children were followed up twice, at 3 and 9-12 months, after discharge from PICU and evaluated for any residual respiratory symptoms and signs, pulse oximetry, chest radiograph, 6-minute walk test, peak expiratory flow rate, and spirometry. Age, sex, duration of illness, primary diagnosis, Pediatric Risk of Mortality III score, lung injury score, mechanical ventilation parameters, oxygenation indices (Pao(2)/Fio(2) ratio and oxygenation index), and duration of PICU stay were recorded from patient records. Measurements and Main Results: Twenty-nine children (25 boys and four girls; mean [sd] age, 8.4 [2.4] yr) were followed up at 3.5 ( 1.2) and 10.6 (+/- 2.7) months after discharge from PICU. Recurrent respiratory symptoms were noted in 37.9% patients (11/29) during first and in none during second follow-up. None had limitation of physical activity or need of supplemental oxygen. Chest examination was normal in all, except one during first follow-up, but 13.8% (4/29) had abnormal chest radiograph during first follow-up. Nearly all children could perform 6-minute walk test although mean distance walked increased significantly from first (352 +/- 66.7 m) to second follow-up (401 +/- 60.7 m; p = 0.002). Abnormal spirometry was seen in 82.7% (24/29) versus 18.5% (5/27) children during first and second follow-up visits, respectively (p = 0.0001). Most cases had restrictive abnormality (58.6% vs 11.1%; p = 0.002) during first and second follow-up, respectively. There was no correlation between pulmonary functions and lung injury scores, oxygenation indices (Pao(2)/Fio(2) ratio and oxygenation index), and mechanical ventilation parameters. Conclusions: Significant number of children ventilated for acute hypoxemic respiratory failure had subclinical pulmonary function abnormality, without limiting physical activity, which improved over time. Further research on this topic with a larger sample size and patient categorization according to recent pediatric acute respiratory distress syndrome definition is needed.