Medical assessor guidance note 16

The Respiratory System: Assessment of Pulmonary Function


This material is issued by the Motor Accidents Authority under s.65 (2) of the Motor Accidents Compensation Act 1999 (the Act) in the interests of promoting accurate and consistent medical assessments under the Act. The interpretation provided here is not legally binding but represents the clinically recommended interpretation in an area where more than one interpretation of existing provisions may be possible. This recommended interpretation is publically available. Any medical assessment which does not adopt this interpretation should be accompanied by clinical justification for the interpretation adopted, supported by full, robust reasons.


  • The Motor Accidents Authority Permanent Impairment Guidelines – Guidelines for the assessment of permanent impairment of a person injured as a result of a motor vehicle accident 1 October 2007 (MAA Guidelines): Chapter 8 The Respiratory System Clauses 8.2 to 8.5 (page 48).
  • The American Medical Association Guides to the Evaluation of Permanent Impairment, 4th Edition (AMA 4 Guides): Chapter 5, (page 153-167) and Tables 2, 3, 4, 5, 6 and 7 (page 156-161).


Physiologic testing of pulmonary function is the quantitative basis on which the evaluation of respiratory system impairment rests. The values obtained from pulmonary function testing are interpreted and quantified in accordance with Tables 2 to 7, (page 156-161) of the AMA 4 Guides against a predicted normal value or reference value.

Issue requiring clarification

The predicted values in the AMA 4 Guides are taken from North American Caucasians. Although an adjustment formula is provided for African Americans, no such recommendation for the proportional adjustment of predicted lung function is provided in the AMA 4 Guides (page 160) for Hispanics, Native Americans, or Asians.

Likewise, Tables 2 to 7, (page 156-161) of the AMA 4 Guides do not provide any proportional adjustment of predicted lung function for children to quantify respiratory impairment in persons under 18 years of age.

Preferred interpretation

Medical assessments within the Medical Assessment Service (MAS) are currently conducted with reference to the MAA Guidelines and the AMA 4 Guides. Where appropriate, Tables 2 to 7, (page 156-161) of the AMA 4 Guides should be used as the quantitative basis of the evaluation of respiratory system impairment.

In cases where use of Tables 2 to 7 (page 156-161) of the AMA 4 Guides is considered inappropriate or likely to give rise to an inaccurate interpretation of lung function and impairment due to age or race, a Medical Assessor may rely on documentation outside the AMA 4 Guides.

Examples of documentation that may be appropriate include (but are not limited to):

  • Spirometric Reference Values from a Sample of the General U.S. Population; Hankinson JL, Odencrantz JR and Fedan KB; American Journal of Respiratory and Critical Care Medicine Vol 159 1999.
  • Lung function in white children aged 4 to 19 years: ll—Single breath analysis and plethysmography: Rosenthal M, Cramer D, Bain SH, Denison D, Bush A, and Warner JO; Thorax 1993; 48:803-808 Downloaded from on 18 March 2009.

Reliance on documentation outside the AMA 4 Guides must be based on a substantial body of peer reviewed research literature. Any such documentation must be referenced in the certificate and:

  1. reasons provided why Tables 2 to 7 of the AMA 4 Guides were not appropriate; and,
  2. a copy or copies attached to the certificate.

Justification for preferred interpretation

In the absence of specific Tables or adjustment formulas in the AMA 4 Guides to accommodate all claimants the accuracy of impairment assessments may not be consistent.

The preferred interpretation and methodology as outlined above is suggested to promote consistency of assessment.

Issued by:

Injury Strategy Branch

April 2014