Measurement of maximal inspiratory pressure (or NIF)

Article

Author: Bernhard Schmitt, Simon Franz

Date of first publication: 02.10.2020

Last change: 02.10.2020

SW versions updated

Users of Hamilton Medical ventilators may wish to use the maximal inspiratory pressure (MIP) to index the capability of the inspiratory muscles, and in particular the strength of the diaphragm. The term negative inspiratory force (NIF) is used synonymously.

Measurement of maximal inspiratory pressure (or NIF)

Definition of MIP

The MIP is defined as the maximal inspiratory effort in the form of pressure generated against an occluded airway. The MIP value can be determined by means of a prolonged airway opening occlusion maneuver, which allows the maximal inspiratory effort to be obtained even without patient cooperation. The duration of an MIP trial varies from 1 to 25 s, and should be repeated at least twice to ensure a reliable value (Sclauser Pessoa IM, Franco Parreira V, Fregonezi GA, Sheel AW, Chung F, Reid WD. Reference values for maximal inspiratory pressure: a systematic review. Can Respir J. 2014;21(1):43-50. doi:10.1155/2014/9823741).

MIP trial on HAMILTON-G5/S1 ventilators

How to perform an MIP trial using the HAMILTON-G5/S1:

Patient must be active, that means breathing spontaneously
Set the Y-axis of the pressure curve manually: Positive 20, negative -120
Set PEEP to 0
Perform an expiratory hold
Measure the minimum of the pressure curve (see Figure 1)

In this example the measured MIP is 44.6, as MIP is always a positive value.

Currently measurement of these values is only possible on the HAMILTON-G5/S1.

Relevant software: 2.8x and later

Screenshot showing measurement of pressure curve minimum — Figure 1

Footnotes

References

1. Sclauser Pessoa IM, Franco Parreira V, Fregonezi GA, Sheel AW, Chung F, Reid WD. Reference values for maximal inspiratory pressure: a systematic review. Can Respir J. 2014;21(1):43-50. doi:10.1155/2014/982374

Reference values for maximal inspiratory pressure: a systematic review.

Sclauser Pessoa IM, Franco Parreira V, Fregonezi GA, Sheel AW, Chung F, Reid WD. Reference values for maximal inspiratory pressure: a systematic review. Can Respir J. 2014;21(1):43-50. doi:10.1155/2014/982374

Link to article

BACKGROUND

Maximal inspiratory pressure (MIP) is the most commonly used measure to evaluate inspiratory muscle strength. Normative values for MIP vary significantly among studies, which may reflect differences in participant demographics and technique of MIP measurement.

OBJECTIVE

To perform a systematic review with meta-analyses to synthesize MIP values that represent healthy adults.

METHODS

A systematic literature search was conducted using Medline, EMBASE, Cochrane, Cumulative Index to Nursing and Allied Health (CINAHL) and Sport Discus databases. Two reviewers identified and selected articles, and abstracted data. Methodological quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tool. A random-effects model was used to calculate overall means and 95% CIs.

RESULTS

Of 22 included articles, MIP data were synthesized according to age group and sex from six reports (n=840) in the meta-analyses. The mean QUADAS score was 3.5 of 7. The age range was between 18 and 83 years (426 men, 414 women). MIP began to decrease with age in the 40 to 60 years age range and continued to fall progressively with age. For the same age group, men tended to have higher MIPs than women. Sensitivity analysis of withdrawing studies from the meta-analysis identified one study that contributed more to heterogeneity in some age groups.

DISCUSSION

MIP was higher in men and decreased with age, which was initially apparent in middle age. Several characteristics of participants and MIP technique influence values in healthy individuals.

CONCLUSIONS

The present meta-analysis provides normative MIP values that are reflective of a large sample (n=840) and likely represents the broadest representation of participant characteristics compared with previous reports of normative data.