Table 1

Description of IPFT indices and their physiological interpretation

IPFTIPFT indicesUnitPhysiological interpretation
TBFVLInspiratory time (tI), expiratory time (tE), total respiratory time (ttot), time to peak tidal inspiratory or expiratory flow (tPTIF or tPTEF)sTime taken to complete individual manoeuvres
Tidal volume (VT), inspiratory or expiratory tidal volume (VI or VE)mLTidal lung volume
Peak tidal inspiratory or expiratory flow (PTIF or PTEF)
Mid tidal inspiratory or expiratory flow (MTIF or MTEF)
Tidal expiratory flow (TEF) at 75, 50, 25 or 10% of tidal expiratory volume still have to be expired (TEF75, TEF50, TEF25 or TEF10)
mL/sFlow rate
Ratio of inspiratory or expiratory time to total respiratory time (tI/ttot or tE/ttot), inspiratory to expiratory time (tI/tE),
Peak ratio: time to PTEF to tE(tPTEF/tE)
Ratio of exhaled volume to PTEF to tidal expiratory volume (VPTEF/VE)
Ratio of TEF75,TEF50, TEF25 or TEF10 to peaked tidal expiratory flow (PTEF)
%Represent airway resistance
RTCMaximum expiratory flow at functional residual capacity (max,FRC)
Maximum expiratory flow at 50% or 70% of expiration (50 or 70)
mL/sFlow rate
Volume to peak expiratory flow (VPEF)mLLung volume at partial expiratory flow—airway resistance
RVRTCForced expiratory volume (FEV), FEV at 0.5, 0.75 or 1.0 s of the forced expiration (FEV0.5/FEV0.75/FEV1.0)mLForced lung volume at given period
Maximum expiratory flow at 25% or 10% of FVC (MEF25 or MEF10)
Forced expiratory flow between 25% and 75% of FVC (FEF25–75)
Peak expiratory flow (PEF)
mL/sForced flow rate representing airway resistance.
Ratio of forced expiratory volume at 0.5 s to total forced expiratory volume (FEV0.5/FEV)%Airway obstruction
  • IPFT, infant pulmonary function testing; RTC, rapid thoracoabdominal compression; RVRTC, raised volume rapid thoracoabdominal compression; TBFVL, tidal breathing flow-volume loop.