Pulmonary Function Tests (PFT’s)

Indications

  • Evaluation of Dyspnea (see Dyspnea)
  • Pre-Operative Evaluation

Technique

Flow-Volume Loop

  • Variable Extrathoracic Upper Airway Obstruction: adversely affects predominantly inspiratory flow (as inspiratory negative intraluminal pressures exacerbate the inspiratory airway narrowing, while expiratory positive intraluminal pressures splints the obstruction open)
  • Variable Intrathoracic Upper Airway Obstruction: adversely affects predominantly expiratory flow (as inspiratory negative pressures decrease the inspiratory airway narrowing, while expiratory positive intrapleural pressures exacerbate the airway obstruction)
  • Fixed Upper Airway Obstruction: adversely affects both inspiratory and expiratory flows

Use of Predicted Value Equations for Interpretation of PFT Data

  • Prediction Equations
    • Global Lungs Initiative (GLI 2012) (Eur Respir J, 2012) [MEDLINE]
    • National Health and Nutrition Examination Survey (NHANES) III (Am J Respir Crit Care Med, 1999) [MEDLINE]
    • European Community for Steel and Coal (ECSC)
  • Clinical Data
    • Comparison of Predictive Values of GLI 2012, NHANES, and European Community for Steel and Coal (ECSC) (Eur Respir J, 2013) [MEDLINE]
      • GLI 2012 equations produce similar predicted values for FEV1 and FVC compared with NHANES, but produce larger values than ECSC
      • Differences in the lower limit of normal lead to an important increase in the prevalence rate of a low FVC compared to ECSC, and a significant decrease compared to NHANES prediction equations
      • Adopting GLI 2012 equations has small effects on the prevalence rate of airway obstruction: GOLD stages 2-4 lead to >20% underdiagnosis of airway obstruction up to the age of 55 years and to 16-23% overdiagnosis in older subjects
      • GLI 2012 equations increase the prevalence of a “restrictive spirometric pattern” compared to European Community for Steel and Coal (ECSC) but decrease it compared to NHANES.

ABSTRACT The aim of this study was to determine the diagnostic and interpretative consequences of adopting the Global Lungs Initiative (GLI) 2012 spirometric prediction equations. We assessed spirometric records from 17 572 subjects (49.5% females), aged 18-85 years, from hospitals in Australia and Poland. We calculated predicted forced expiratory volume in 1 s (FEV1), forced expiratory volume (FVC), FEV1/FVC and lower limits of normal (LLN) using European Community for Steel and Coal (ECSC), National Health and Nutrition Examination Survey (NHANES) III and GLI 2012 equations. Obstruction was defined as FEV1/FVCLLN and FVC20% underdiagnosis of airway obstruction up to the age of 55 years and to 16-23% overdiagnosis in older subjects. GLI 2012 equations increase the prevalence of a “restrictive spirometric pattern” compared to ECSC but decrease it compared to NHANES.

Spirometry

Forced Expiratory Volume in One Second (FEV1)

  • FEV1 Reflects XXXXXXXXXX
    • xxxx
  • Considerations in Using the FEV1 % Predicted
    • FEV1 % Predicted is Not Applicable to the Assessment of Upper Airway Obstruction
    • FEV1 % Predicted May Sometimes Fail to Identify the Severity of the Defect, Especially the Very Severe Stage of Disease
    • FEV1 % Predicted Correlates Poorly with Symptoms and Prognosis
    • Lung Hyperinflation and Expiratory Flow Limitation During Tidal Breathing May Be Useful to Categorize the Severity of Lung Impairment
  • Using the FEV1 % Predicted to Assess the Severity of Obstruction (Eur Respir J, 2005) [MEDLINE]
    • Mild Obstruction: FEV1 >70% Predicted
    • Moderate Obstruction: FEV1 60-69% Predicted
    • Moderately Severe Obstruction: FEV1 50-59% Predicted
    • Severe Obstruction: FEV1 35-49% Predicted
    • Very Severe Obstruction: FEV1 <35% Predicted

Bronchodilator Responsiveness Trial

  • Technique
    • Test Baseline FEV1
    • Administer Albuterol 100 μg x 4 Doses Via a Spacer
    • Re-Test FEV1 15 min Later
  • Definition of Bronchodilator Responsiveness: defined as increase in FEV1 and/or FVC ≥12% of control and ≥200 mL
  • Considerations in Using Bronchodilator Responsiveness Trial
    • In the absence of a significant increase in FEV1 and/or FVC, an improvement in lung function parameters within the tidal breathing range, such as increased partial flows and decrease of lung hyperinflation, may explain a decrease in dyspnea
    • The lack of a bronchodilator response in the laboratory does not preclude a clinical response to bronchodilator therapy

Forced Vital Capacity (FVC)

  • xxxx

Forced Expiratory Volume in One Second (FEV1)/Forced Expiratory Volume (FVC) Ratio

  • xxx

Lung Volumes

  • Total Lung Capacity (TLC)
  • Functional Residual Capacity (FRC)
  • Residual Volume (RV)

Diffusion Capacity for Carbon Monoxide (DLCO)

Technique

  • xxx

Pulmonary Function Test (PFT) Obstructive Pattern (see Obstructive Lung Disease)

Pulmonary Function Test Features of Obstructive Pattern

  • xxx

Etiology of Obstructive Pattern

Upper Airway Obstruction

Tracheobronchial Airway Obstruction

Other Airway Obstruction

Pulmonary Function Test Restrictive Pattern

Pulmonary Function Test Features of Restrictive Pattern

  • xxx

Etiology of Restrictive Pattern -> P-A-I-N-T-O-P-P-M

Pleural Disease

Alveolar Filling Process

Interstitial Lung Disease (ILD)

Neuromuscular Disease

Thoracic Cage Abnormality

  • PFT Features
    • Decreased TLC
    • Decrease in VC
    • Small Decrease in FRC (normal-slightly increased in Ankylosing Spondylitis cases with restricted thoracic cage expansion)
  • Examples

Obesity

  • PFT Features
    • xxxx

Pulmonary Hypertension

Poor Cooperation

  • PFT Features
    • xxxx

Miscellaneous

  • Beta Thalassemia Major (see Thalassemias): restriction may occur (for unclear reasons)
    • Pulmonary Function Test Defects Correct with Transfusion and Do Not Correlate with the Iron Burden, Blood Counts, or Degree of Hemolysis

Pulmonary Function Test Non-Specific Pattern (Chest, 2009) [MEDLINE] (Chest, 2011) [MEDLINE]

Epidemiology

  • Non-Specific PFT Pattern Occurs in Approximately 9.5% of Complete PFT’s (Chest, 2009) [MEDLINE]
  • The Term “Small Airways Obstruction Syndrome” Has Also Been Suggested to Describe this Finding (Chest, 1999) [MEDLINE]

Diagnostic Pulmonary Function Test Features of Non-Specific Pattern

  • Decreased FEV1 + Decreased FVC + Normal FEV1/FVC Ratio with Normal Total Lung Capacity (TLC)
    • Restriction is Suggested, But a Normal TLC Rules Out Restriction

Clinical Features (Chest, 2009) [MEDLINE]

  • Approximately 56% of Patients with Non-Specific PFT Pattern Had Airway Hyperresponsiveness (by Clinical Diagnosis of Asthma and/or Positive Bronchodilator or Methacholine Challenge Response)
  • Approximately 50% of Patients with Non-Specific Pattern Had BMI ≥30 kg/m2
    • In the Obese Patients, 83% of the Females and 50% of the Males Had Airway Hyperresponsiveness
  • In Follow-Up PFT Testing, Approximately 66% of Patients Demonstrate this Pattern Reliably Over Time (Chest, 2011) [MEDLINE]

Pulmonary Function Abnormalities in Diffusion Capacity for Carbon Monoxide (DLCO)

Etiology of Increased Diffusion Capacity for Carbon Monoxide (DLCO)

  • Diffuse Alveolar Hemorrhage (DAH) (see Diffuse Alveolar Hemorrhage)
    • Physiology: due to increased hemoglobin within alveoli
  • Asthma (see Asthma)
    • Physiology: due to increased pulmonary capillary blood volume

Etiology of Decreased Diffusion Capacity for Carbon Monoxide (DLCO)

References

  • Small airways obstruction syndrome, Chest 1999; 116:231-233 [MEDLINE]
  • Spirometric reference values from a sample of the general U.S. population. Am J Respir Crit Care Med. 1999 Jan;159(1):179-87 [MEDLINE]
  • GOLD Scientific Committee. Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease. NHLBI/WHO Global Initiative for Chronic Obstructive Lung Disease (GOLD) Workshop summary. Am J Respir Crit Care Med 2001; 163: 1256–1276
  • Standard for the diagnosis and treatment of patients with COPD: a summary of the ATS/ERS position paper. Eur Respir J 2004; 23: 932–946
  • Interpretative strategies for lung function tests. Eur Respir J. 2005 Nov;26(5):948-68 [MEDLINE]
  • Conditions associated with an abnormal nonspecific pattern of pulmonary function tests. Chest. 2009 Feb;135(2):419-24. doi: 10.1378/chest.08-1235. Epub 2008 Sep 23 [MEDLINE]
  • The nonspecific pulmonary function test: longitudinal follow-up and outcomes. Chest. 2011 Apr;139(4):878-86. doi: 10.1378/chest.10-0804. Epub 2010 Aug 19 [MEDLINE]
  • Multi-ethnic reference values for spirometry for the 3-95-yr age range: the global lung function 2012 equations. Eur Respir J. 2012 Dec;40(6):1324-43. doi: 10.1183/09031936.00080312. Epub 2012 Jun 27 [MEDLINE]
  • Implications of adopting the Global Lungs Initiative 2012 all-age reference equations for spirometry. Eur Respir J. 2013 Oct;42(4):1046-54. doi: 10.1183/09031936.00195512. Epub 2013 Mar 21 [MEDLINE]