Makindo Medical Notes

Assessment

Overview of Spirometry

Spirometry is a common pulmonary function test that measures the volume of air an individual can exhale after a deep breath and how quickly the air is exhaled. It is essential for diagnosing and monitoring respiratory conditions such as asthma, chronic obstructive pulmonary disease (COPD), and other conditions that affect breathing.

Key Spirometry Measurements

• Forced Vital Capacity (FVC):
  • The total amount of air exhaled during the forced breath.
• Forced Expiratory Volume in 1 Second (FEV1):
  • The amount of air exhaled during the first second of the forced breath.
• FEV1/FVC Ratio:
  • The percentage of the FVC exhaled in the first second. It is a critical parameter for identifying obstructive and restrictive lung diseases.

Normal Spirometry Values

Normal values for spirometry measurements vary based on age, sex, height, and ethnicity. Predicted values are calculated using these variables, and actual measured values are compared to the predicted values.

Spirometry Interpretation

The interpretation of spirometry results involves comparing the measured values to the predicted values and assessing the FEV1/FVC ratio.

Parameter	Normal Range
FEV1	80% or more of the predicted value
FVC	80% or more of the predicted value
FEV1/FVC Ratio	70% or more (may vary with age)

Patterns of Abnormal Spirometry

• Obstructive Pattern:
  • Characterized by a reduced FEV1/FVC ratio (<70%).
  • FEV1 is typically reduced more than FVC.
  • Common causes: asthma, COPD, bronchiectasis.
• Restrictive Pattern:
  • Characterized by a normal or high FEV1/FVC ratio.
  • Both FEV1 and FVC are reduced, but the ratio remains normal because both values are proportionally reduced.
  • Common causes: pulmonary fibrosis, interstitial lung disease, obesity, neuromuscular diseases.
• Mixed Pattern:
  • Features of both obstructive and restrictive patterns.
  • Reduced FEV1/FVC ratio with reduced FVC.
  • Common causes: combined conditions such as COPD with pulmonary fibrosis.

Example Spirometry Interpretation

Below is an example of how spirometry results might be interpreted:

Parameter	Measured Value	Predicted Value	Percentage of Predicted
FEV1	2.5 L	3.0 L	83%
FVC	3.2 L	4.0 L	80%
FEV1/FVC Ratio	78%	75%	-

Interpretation: The measured FEV1 is 83% of the predicted value, and the FVC is 80% of the predicted value, which are both within normal limits. The FEV1/FVC ratio is 78%, which is above the threshold of 70%, indicating no evidence of obstructive lung disease. These results suggest normal spirometry.

Steps for Spirometry Interpretation

• Assess the quality of the test to ensure it meets acceptability and reproducibility criteria.
• Compare measured values (FEV1, FVC) to predicted values based on age, sex, height, and ethnicity.
• Evaluate the FEV1/FVC ratio to identify obstructive or restrictive patterns.
• Consider the clinical context, including patient history and symptoms, to support the spirometry findings.

Flow volume loops