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Chapter 16: Pulmonary Function Testing, Plethysmography, and Pulmonary Diffusing Capacity

Gerald S. Zavorsky; Andrew J. Lechner

LEARNING OBJECTIVES

Learning Objectives

  • The student will be able to identify the static and dynamic pulmonary function tests (PFTs) commonly performed to establish obstructive and/or restrictive patterns.

  • The student will be able to describe the operating principle of a whole-body plethysmograph and the measurements obtained from such an apparatus.

  • The student will be able to explain the use of carbon monoxide to estimate pulmonary diffusing capacity and diseases in which diffusion is altered.

This chapter examines the many practical applications of pulmonary function testing (PFT) for evaluating lung function and disease progression in individual patients, as well as identifying broader public health concerns across populations. The full range of PFT procedures can assess airway resistance, functional residual capacity (FRC) and residual volume, pulmonary diffusing capacity, arterial blood gases (ABGs), exercise capacity, and even energy expenditure. While spirometry was introduced in Chaps. 4 and 6, the more detailed descriptions here include specific diagnostic criteria for grading the severities of obstructive and restrictive lung disease types, as developed by the American Thoracic Society and European Respiratory Society (ATS/ERS) (Table 16.1).

Table 16.1Primary reasons for pulmonary function testing
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Table 16.1 Primary reasons for pulmonary function testing
Confirming a Diagnosis of Primary or Secondary Lung Disease
To evaluate:

New signs of diminished breath sounds, crackles, clubbing, hyperinflation;

Symptoms of dyspnea, wheezing, orthopnea, cough, sputum production, chest pain;

Abnormal imaging studies and arterial blood gases (hypoxemia, hypercapnia).
To measure: Effects of new systemic diseases on pulmonary function.
To screen:

Past and present smokers, and those exposed to second-hand smoke;

Individuals with occupational, domestic, or social risk factors.
To assess: Preoperative risk and/or prognosis for lung transplantation, cystic fibrosis (CF), etc.
Sequential Monitoring during Management of Known Lung Disease
To assess:

Therapeutic interventions for asthma with bronchodilators, corticosteroids, etc;

Complications from systemic disorders (congestive heart failure, sarcoidosis, etc);

Adequacy of antibiotics for CF, antiarrhythmics that affect DLCO, etc.
To define: Pulmonary complications from cardiovascular and neuromuscular diseases.
To monitor:

Adverse drug reactions when pulmonary toxicity is known or suspected;

Mitigation efficacy against occupational or domestic risk factors for lung disease.
Evaluating Known or Suspected Disabilities and Impairments
To assess: Patient suitability for medical, industrial, or vocational rehabilitation programs.
To confirm:

Eligibility for insurance or worker's compensation, and personal injury lawsuits;

Compliance with behavioral, pharmacological, or other prescribed activities.
Establishing Public Health Policies, Regional Action Plans, and Legislative Agendas
To survey: Identified or suspected populations at risk for pulmonary disease.
To validate:

Subjective complaints of occupational, environmental, or industrial risk or injury;

Reference equations derived to predict any related feature of lung function.

SPIROMETRY AS THE ENTRY POINT TO PULMONARY FUNCTION TESTING

Spirometry is non-invasive, dynamic pulmonary function testing that indirectly assesses airway resistance, notably in medium-sized bronchi. Among the lung volumes estimated by spirometry to distinguish obstructive and restrictive ...

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