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Spirometry PIF Peak Inspiratory Flow

last modified on: Fri, 02/23/2024 - 15:19

return to: 10 Minute Primer on PFTs Lecture 07 30 2016; Case Example 1: Subglottic Stenosis due to Wegener's Granulomatosis

Subglottic stenosis; Tracheostomy and Upper Airway Management Symposium July 30 2016 IAO and SOHN Iowa City Iowa

see also: Pulmonary Function Testing (PFT) made simple and NIF or PImax in PFTs

Spirometry = dynamic study dependent on coaching, effort, and technique

Click on video below for demonstration of procedure:

Pulmonary function tests

  1. Of all the variables tested and reported, the flow volume loop (inferior limb = inspiratory limb) is the most directly relevant to the upper airway (laryngeal or tracheal narrowing)
  2. Request "PIF" (peak inspiratory flow rate) to be reported - calculated from inspiratory limb of flow volume loop – general rules (modified by the patients size, overall health, symptoms):
    1. < 1 liter /sec: admit the patient or operate immediately
    2. 1-2 liters/sec: schedule surgery soon
    3. 2-3 liters/sec: schedule followup in 6-8 weeks
    4. 3-4 liters/sec: schedule followup in 4 to 6 months
    5. >4 liters/sec: relax
  3. Difficulties in interpreting PFT's can arise from variation in effort expended as well as muscle weakness compromising an otherwise intense effort
    1. PIMAX = maximum inspiratory mouth pressure (also termed NIF = negative inspiratory force) see video NIF or PImax in PFTs
      1. Is an index of inspiratory muscle strength (Black 1969)
        1. Is a routine procedure in many pulmonary function laboratories
        2. Hautmann et al in 2000 published the mean PIMAX (kPA)
          • for men (N=248) to be 9.95 kPa
          • for women (N=256) to be 7.43 kPa
        3. "strongly dependent on the skill of the technician" (may account for 5%- 12% variation) and "the motivation of the patient"
        4. strongest correlation in results were for sex and age, but also height/weight/BMI and different lung function parameters.

REFERENCES

Alternative, experimental method for measuring air flow in patients with laryngotracheal stenosis 

Wassermann et al. Measuring in situ central airway resistance in patients with laryngotracheal stenosis. Laryngoscope 1999 Sep;109(9):1516-20.

Tasche KK, Bayan S, Schularick NM, Wilson J and Hoffman HT: Utility of peak inspiratory flow in managing subglottic stenosis. Ann Oto Rhinol Laryngol. 2015 Jun;124(6):499-504 Epub 2014 Dec 23

Hautmann H, Hefele S, Schotten K, Huber RM: Maximal inspiratory mouth pressures (PIMAX) in Healthy Subjectes – what is the lower limit of normal. Respir Med. 2000 Jul; 94(7):689-93

Black LF, Hyatt RE. Maximal respiratory pressures: normal values and relationship to age and sex. Am Rev Respir Dis 1969;99:696-702