Spirometry
Spirometry was performed by a portable spirometer, spirolab (Medical
International Research, Rome, Italy) which is standardised for Indian
children (based on height) in Paediatric OPD AIIMS, New Delhi during
follow up visits. Forced expiratory volume in 1 second of predicted
(FEV1), forced vital capacity (FVC), FEV1/FVC ratio were assessed after
obtaining acceptable spirometry curves. Abnormal pulmonary function is
determined as presence of obstructive, restrictive or mixed pattern on
spirometry or abnormality in three minute step test. Obstructive pattern
is defined as having forced vital capacity of percent predicted ≥80%
and FEV1/FVC <85%. Restrictive pattern is defined as having
forced vital capacity of percent predicted <80% and FEV1/FVC
≥85%. Mixed pattern is defined as having forced vital capacity of
percent predicted <80% and FEV1/FVC <85%. Based on
FEV1, severity of obstructive pattern was assessed as mild, moderate,
moderately severe, severe or very severe obstruction if predicted FEV1
is >70%, between 60% to 69%, between 50% to 59%,
between 35% to 49%, <35% respectively. Based on FVC,
severity of restrictive pattern was assessed as mild, moderate, severe
or very severe obstruction if predicted FVC is >70%,
between 50% to 69%, between 35% to 49%, between, <35%
respectively