From the Guidelines
A high peak expiratory flow (PEF) with a low-normal peak inspiratory flow (PIF) is indicative of a potential issue with inspiratory muscle function or upper airway obstruction during inhalation, and thus, requires evaluation by a pulmonologist or respiratory specialist for proper diagnosis and management. This pattern is characterized by a reduction in inspiratory flows, which can be seen in conditions such as respiratory muscle weakness or upper airway obstruction 1. The maximum expiratory and maximum inspiratory flow–volume curves can show a reduction in those flows that are most effort dependent, including maximum inspiratory flow at all lung volumes.
Some possible causes of this pattern include:
- Vocal cord dysfunction
- Paradoxical vocal fold movement
- Extrathoracic airway obstruction Treatment depends on the underlying cause, but may include:
- Speech therapy with breathing exercises for vocal cord issues
- Continuous positive airway pressure (CPAP) therapy if related to sleep apnea
- Bronchodilators like albuterol (2 puffs every 4-6 hours as needed) if there's a reversible component
- Inspiratory muscle training using devices like POWERbreathe or Threshold IMT for 30 breaths twice daily at 30% of maximal inspiratory pressure to strengthen breathing muscles, as seen in patients with respiratory muscle weakness 1.
It is essential to note that this breathing pattern differs from asthma or COPD, which typically show reduced expiratory flows. Proper diagnosis is crucial as misdiagnosis can lead to inappropriate treatment with medications that won't address the actual problem. Therefore, a comprehensive evaluation by a specialist is necessary to determine the underlying cause and develop an effective treatment plan.
From the Research
Peak Inspiratory and Expiratory Flow Rates
- Peak inspiratory flow (PIF) and peak expiratory flow (PEF) are important measures of lung function, with PEF being the maximum airflow generated during exhalation and PIF being the maximum airflow generated during inhalation 2, 3.
- A very high PEF and low normal PIF may indicate an issue with inspiratory muscle strength or coordination, or an obstruction in the airways that affects inhalation more than exhalation 4, 5.
Relationship Between PIF and PEF
- Studies have shown that PIF is often less reduced than expiratory parameters of pulmonary function in patients with asthma or COPD, suggesting that inspiratory and expiratory flows may be affected differently by lung disease 2, 5.
- However, there is a significant correlation between inspiratory and expiratory volumes, and PIF can be predicted based on its determinants such as gender, age, and height 3.
Clinical Significance of PIF and PEF
- Measuring PIF and PEF can be useful in diagnosing and monitoring respiratory diseases, and can help identify patients who may benefit from specific treatments or interventions 4, 5.
- Peak inspiratory flow has been identified as a predictive therapeutic biomarker in COPD, and can help optimize therapy and improve patient outcomes 4.
Measurement of PIF and PEF
- PIF and PEF can be measured using a variety of devices, including spirometers and peak flow meters, and can be performed in a clinical or home setting 2, 3.
- The measurement of PIF and PEF should be performed according to standardized protocols and guidelines to ensure accurate and reliable results 3, 5.