Spirometry: An Interpretation of Patterns and Clinical Implications

Abstract

Introduction: In general practice spirometry is under utilized in the diagnosis of the common respiratory symptom like breathlessness. A standardized forcible expiratory blow inside the spirometry machine followed by a force inspiratory maneuver displays various data related to flow of air in the lungs in the form of a flow-volume loop and volume-time tracings. A valid reporting as per ATS criteria is prerequisite for the interpretation and then compared with a predicted values of an individual.
Results: The main four parameters FVC, FEV1, ratio of FEV1/FVC and peak expiratory flow (PEF) are studied in patients to categorized them in various patterns; e.g. A) Normal pattern (40%), B) Obstructive flow pattern (15%); C) Restrictive (1%); D) Mixed pattern (28%); E) Obstructive (3%); and F) Mixed pattern (13%) with dominant obstructive/pseudo restrictive. A significant BD effect was observed in 28% (32/115) participants with having normal spirometry, while 40% (70/175) BD effect was observed among abnormal spirometry patterns. A low CPF was detected in 91(31%) of case and similarly, a value of less than 1L/sec PIFR was observed in 23 (8%) cases and thus not suitable for the DPI device. An overall restrictive PRISM in 11(4%), obstructive PRISM in 61 (21%) cases were also detected.
Discussion: Once the basic four parameters were identified and grouped together in various patterns, it becomes easy to understand the underlying ailment. These patterns enable differential diagnosis and help to customize management. The BD therapy could be planned and given to all who had produced a significant or partial response. A PIFR value of more than 1 liter/second would be required for the dry powder inhaler (DPI); otherwise, a device like MDI with a spacer or nebulizer should be preferred. Similarly, a normal adult should have more than 4L/Sec of PEFR, which is sufficient to clear the secretion as cough peak flow (CPF). Broadly a breathing exercises for the restrictive disorders, diaphragmatic and purse lip breathing for the obstructive pattern is recommended with periodic reassessment with spirometry. An additional detection of PRISM (preserved ratio impaired spirometry) cases could advise preventive measures, e.g., smoking cessation, etc., to minimize the risk of future disease load.
Conclusion: Spirometry is an important tool in evaluating shortness of breath and other respiratory symptoms which could be due to neuromuscular, pleural, parenchymal, and small or large airways abnormalities. It has a crucial role in differential diagnosis and dynamic volumetric assessment of a forceful expirational and inspirational activities. A newer version of spirometry or advanced technology equipment like FENO and oscillometry have become widely acceptable as thet are free from strict forceful maneuver (e.g. easy usual breath suitable for children and ICU patient), they are handy and cost effective and serve as alternate future modality.