What is TPEF (Tidal Peak Expiratory Flow) on spirometry?

Understanding TPEF (Tidal Peak Expiratory Flow) on Spirometry

TPEF (Tidal Peak Expiratory Flow) is a measurement of the maximum flow rate achieved during normal tidal breathing, which is used to evaluate respiratory mechanics and can help identify airway obstruction patterns in patients, particularly in young children who cannot perform forced maneuvers. 1

Definition and Measurement

TPEF is part of tidal breathing analysis, which examines the flow patterns during normal, relaxed breathing. Key parameters related to TPEF include:

• Time to peak tidal expiratory flow (tPTEF): The time from the beginning of expiration to the point of maximum expiratory flow, measured in seconds
• Total expiratory time (tE): The total duration of expiration, measured in seconds
• tPTEF/tE ratio: The ratio of time to peak flow to total expiratory time 1

Similarly, volume-based measurements include:

• Volume at peak tidal expiratory flow (Vptef): The volume expired when peak flow is reached, measured in milliliters
• Expired tidal volume (Ve): Total volume expired, measured in milliliters
• Vptef/Ve ratio: The ratio of volume at peak flow to total expired volume 1

Clinical Significance

TPEF and related parameters have several important clinical applications:

1. Distinguishing airway obstruction: Adults, children, and infants with wheezing disorders typically have lower tPTEF/tE and Vptef/Ve values compared to healthy individuals, though with considerable overlap between groups 1

2. Early detection of respiratory issues: Reduced tPTEF/tE in early infancy has been associated with increased subsequent wheezing, although with low predictive value 1

3. Monitoring response to treatment: Studies have shown that nebulized epinephrine in infants with bronchiolitis and β2-agonists in wheezy infants and young children with asthma result in an increase in tPTEF/tE 1

4. Discrimination between asthmatic and non-asthmatic children: TPEF-related parameters (TPEF/TE, VPEF/VE, and TEF25/PEF) are significantly lower in asthmatic children than in controls 2

Technical Considerations

When measuring TPEF:

• Measurements should be calculated from at least 10 (ideally consecutive) individual breaths, then expressed as a mean 1
• The coefficient of variation (CV) should be reported to assess measurement reliability
• Repeatability of tPTEF/tE measurements typically shows intraindividual CV between 20-26% in normal subjects 1
• The child's breathing pattern must be natural and stable during measurement
• Real-time visualization of the signal is essential to ensure stable respiratory patterns before data recording 1

Limitations and Caveats

• There is considerable overlap in TPEF values between healthy individuals and those with respiratory disorders, limiting its diagnostic specificity 1
• TPEF parameters show variable correlation with direct measures of lung function:
  • In infants, Vptef/Ve correlates poorly with measures of respiratory resistance
  • In older children, tPTEF/tE correlates moderately with FEV1 and FEF50 (r values around 0.5) 1
• Unlike peak expiratory flow (PEF) in forced maneuvers, TPEF is measured during normal tidal breathing and should not be confused with PEF from forced spirometry 3
• TPEF measurements are particularly useful in preschool children who cannot perform standard forced spirometry maneuvers 1

TPEF analysis represents one approach to assessing respiratory function in situations where standard spirometry is difficult or impossible to perform, particularly in young children and infants.