From the Guidelines
Peak flow measurements are not the primary assessment tool for COPD, and spirometry with FEV1 measurement is the preferred method for diagnosing and monitoring COPD severity. For mild to moderate COPD, peak expiratory flow (PEF) values generally range from 50-80% of predicted normal values, while severe COPD patients typically show PEF values below 50% of predicted 1. However, it's essential to note that FEV1 values of 50-80% predicted indicate mild to moderate disease, while values below 50% suggest severe COPD, as stated in the BTS guidelines for the management of chronic obstructive pulmonary disease 1.
Key Points to Consider
- Peak flow meters can be used for home monitoring between clinic visits, with patients establishing their personal best values as reference points.
- Readings should be taken at the same time daily, preferably in the morning and evening, recording the highest of three attempts.
- A consistent decline in peak flow measurements of 20% or more may indicate worsening airflow obstruction and should prompt medical evaluation.
- The limitation of peak flow in COPD is that it primarily measures large airway function, while COPD affects both small and large airways, making spirometry with FEV1/FVC ratio the gold standard for comprehensive assessment 1.
Importance of FEV1 Measurement
The FEV1 is strongly recommended as the measurement of choice in COPD due to its reproducibility, objectivity, and ability to measure disease progression 1. It can be measured relatively easily and quickly, and the forced expiratory manoeuvre records not only FEV1 but also FVC, allowing for the diagnosis of airways obstruction. The variance of repeated measurements in the same person is well documented and is low, making it a reliable tool for monitoring disease progression. Therefore, FEV1 measurement should be prioritized over peak flow measurements for diagnosing and monitoring COPD severity.
From the Research
Peak Flow Measurements in COPD
- Peak flow measurements are an essential tool in managing Chronic Obstructive Pulmonary Disease (COPD) 2.
- A peak expiratory flow of <80% predicted is considered the best cut-off to detect airflow limitation, with a sensitivity of 90% and specificity of 50% 2.
Mild-Moderate COPD
- For patients with mild-moderate COPD, peak flow measurements can be used to monitor disease progression and response to treatment 3, 4.
- Combination therapies, such as salmeterol and fluticasone, have been shown to improve peak expiratory flow rates in patients with COPD 3, 4.
Severe COPD
- In patients with severe COPD, peak flow measurements may be limited by the severity of airway obstruction 5.
- Nebulized beta-agonists, such as arformoterol, may be more effective than dry powder inhalers in improving lung function in patients with severe COPD and suboptimal peak inspiratory flow rates 5.
Comparison of Treatments
- Different combination therapies, such as budesonide/formoterol and fluticasone/salmeterol, have been compared in terms of their effectiveness in preventing exacerbations in COPD 6.
- The PATHOS study found that budesonide/formoterol was more effective than fluticasone/salmeterol in preventing exacerbations in patients with moderate and severe COPD 6.