Asthma pulmonary function test: Difference between revisions

Jump to navigation Jump to search
m (Bot: Removing from Primary care)
 
Line 36: Line 36:
==References==
==References==
{{reflist|2}}
{{reflist|2}}
{{WH}}
{{WS}}


[[Category:Disease]]
[[Category:Disease]]
Line 46: Line 48:
[[Category:Allergology]]
[[Category:Allergology]]
[[Category:Asthma]]
[[Category:Asthma]]
[[Category:Primary care]]
[[Category:Up-To-Date]]
[[Category:Up-To-Date]]
[[Category:Up-To-Date pulmonology]]
[[Category:Up-To-Date pulmonology]]
[[Category:Mature chapter]]
[[Category:Mature chapter]]
{{WH}}
{{WS}}

Latest revision as of 20:30, 29 July 2020

Asthma Microchapters

Home

Patient Information

Overview

Historical Perspective

Classification

Pathophysiology

Causes

Differentiating Asthma from other Diseases

Epidemiology and Demographics

Risk Factors

Screening

Natural History, Complications and Prognosis

Diagnosis

History and Symptoms

Physical Examination

Laboratory Findings

Electrocardiogram

Chest X Ray

CT

MRI

Other Imaging Findings

Other Diagnostic Studies

Pulmonary Function Test
Bronchial Challenge Test
Exhaled nitric oxide

Treatment

Emergency Management

Medical Therapy

Alternative and Complementary Medicine

Bronchial Thermoplasty

Primary Prevention

Secondary Prevention

Cost-Effectiveness of Therapy

Future or Investigational Therapies

Case Studies

Case #1

Asthma pulmonary function test On the Web

Most recent articles

Most cited articles

Review articles

CME Programs

Powerpoint slides

Images

American Roentgen Ray Society Images of Asthma pulmonary function test

All Images
X-rays
Echo & Ultrasound
CT Images
MRI

Ongoing Trials at Clinical Trials.gov

US National Guidelines Clearinghouse

NICE Guidance

FDA on Asthma pulmonary function test

CDC on Asthma pulmonary function test

Asthma pulmonary function test in the news

Blogs on Asthma pulmonary function test

Directions to Hospitals Treating Asthma

Risk calculators and risk factors for Asthma pulmonary function test

Editor(s)-in-Chief: C. Michael Gibson, M.S., M.D. [1] Phone:617-632-7753; Philip Marcus, M.D., M.P.H. [2]; Associate Editor(s)-In-Chief: Lakshmi Gopalakrishnan, M.B.B.S. [3]

Overview

Asthma is defined as reversible airway obstruction that occurs both, spontaneously without intervention or even with treatment. Measurement of peak flow rates and spirometry are two valuable methods to assess pulmonary function. While measurement of airway function is possible in adults, most new cases that are diagnosed constitute the pediatric age group, who are unable to perform such tests. Diagnosis in children is based on a careful compilation and analysis of the individual's medical history and demonstration of symptomatic improvement with the administration of inhaled bronchodilator. In adults, diagnosis can be made with a peak flow meter that assess any airway restriction, diurnal variation and any reversibility following inhaled bronchodilator. Young asthmatics may experience only exercise-induced asthma; hence, testing peak flow at rest and after exercise may be beneficial. If in doubt, spirometry may be conducted to ascertain the diagnosis. Once the diagnosis is established, peak flow meter testing may be conducted to monitor the severity and progression of the disease. Capnography may be used in the emergency situations, to measure the amount of exhaled carbon dioxide and if used in conjunction with pulse oximetry may be possible to estimate the amount of oxygen dissolved in the blood, in order to determine the severity of an asthma attack as well as the predict the response to therapy.[1]

Pulmonary Function Test

Spirometry

  • The preliminary investigation of choice to establish diagnosis of asthma is the assessment of lung function using spirometry that includes measurement of forced vital capacity (FVC) and forced expiratory volume in one second (FEV1). Baseline spirometry provides a fairly accurate assessment of the disease severity, degree of airway obstruction and also helps to differentiate between obstructive or restrictive patterns of airway disease.[2]
  • The classic spirometry findings consistent with airway obstruction include a reduced FEV1 and a subsequent reduction in the FEV1:FVC ratio. However, a normal to increased FEV1:FVC ratio would rule out the presence of an airway obstruction.
  • The hallmark of asthma is the reversibility of airway obstruction that can be demonstrated with the initial spirometry by measuring the lung volumes before and after the administration of a short-acting bronchodilator. A 12% or greater increase in forced expiratory volume in 1 second (FEV1) is strongly suggestive of asthma.
  • Single-breath counting is a measurement of how far an individual can count in a normal speaking voice after a maximal effort inhalation and serves as a convenient method to measure pulmonary function in children.[3]

Peak Expiratory Flow Rate

  • Peak expiratory flow rate (PEFR) is a measurement of an individual's maximum ability to expel air from the lungs.
  • A significant reduction in the peak expiratory flow rate from normal predicted value is suggestive but not diagnostically conclusive of asthma. However, the reversibility of peak flow rate following the administration of a short-acting bronchodilator may favor the diagnosis of asthma.
  • A serial monitoring of peak expiratory flow rate helps to monitor the patient's response to therapy, evaluate the severity of symptoms and estimate the frequency of exacerbations.
  • The PEFR is an effort dependent measurement that is recorded using a peak flow meter which is a small hand-held device and helps to define the patient's normal peak flow rate.
  • Based on the American Lung Association, peak flow readings are classified into three zones of measurement namely: green, yellow, and red.
  • The green zone means 80 to 100 percent of the usual or normal peak flow readings are clear. A peak flow reading in the green zone indicates that the asthma is deemed under "good" control.
  • The yellow zone means 50 to 80 percent of the usual or normal peak flow readings indicate caution. It may indicate narrowing of respiratory airways and hence an additional medication may be required.
  • The red zone means less than 50 percent of the usual or normal peak flow readings indicate a medical emergency. It signifies severe airway obstruction that may warrant immediate medical attention.
  • Reduced PEFR may be observed in both obstructive and restrictive airway disease and is not specific for asthma.
  • PEFR does not differentiate asthmatic wheeze from other causes of wheeze. A predominant inspiratory monophonic wheeze is suggestive of vocal cord dysfunction, while a polyphonic expiratory wheeze is more consistent with asthma.
  • PEFR is effort dependent and the validity of the measurement solely depends on the individual's effort and technique employed.
  • PEFR readings are not consistent and varies with different instruments.

Diagnostic Criteria Based on The British Thoracic Society[7]

  • ≥20% difference on at least three days in a week for at least two weeks;
  • ≥20% improvement of peak flow following treatment. For example:

References

  1. Corbo J, Bijur P, Lahn M, Gallagher EJ (2005) Concordance between capnography and arterial blood gas measurements of carbon dioxide in acute asthma. Ann Emerg Med 46 (4):323-7. PMID: 16187465
  2. 2.0 2.1 Enright PL, Lebowitz MD, Cockroft DW (1994) Physiologic measures: pulmonary function tests. Asthma outcome. Am J Respir Crit Care Med 149 (2 Pt 2):S9-18; discussion S19-20. PMID: 8298772
  3. Ali SS, O'Connell C, Kass L, Graff G (2011) Single-breath counting: a pilot study of a novel technique for measuring pulmonary function in children. Am J Emerg Med 29 (1):33-6. DOI:10.1016/j.ajem.2009.07.006 PMID: 20825771
  4. (1991) Lung function testing: selection of reference values and interpretative strategies. American Thoracic Society. Am Rev Respir Dis 144 (5):1202-18. PMID: 1952453
  5. Smith HR, Irvin CG, Cherniack RM (1992) The utility of spirometry in the diagnosis of reversible airways obstruction. Chest 101 (6):1577-81. PMID: 1350971
  6. (1995) Standardization of Spirometry, 1994 Update. American Thoracic Society. Am J Respir Crit Care Med 152 (3):1107-36. PMID: 7663792
  7. Pinnock H, Shah R (2007) Asthma. BMJ 334 (7598):847-50. DOI:10.1136/bmj.39140.634896.BE PMID: 17446617

Template:WH Template:WS