# Influence of Achalasia on the Spirometry Flow–Volume Curve and Peak Expiratory Flow

## TL;DR

This study explores how achalasia, a digestive disorder, affects lung function tests, showing that it can cause abnormal spirometry results that might be mistaken for lung disease.

## Contribution

The study identifies a novel link between achalasia and specific spirometry patterns, highlighting the importance of recognizing non-pulmonary causes of airway obstruction.

## Key findings

- Achalasia patients with mega-esophagus showed a plateau in the inspiratory flow–volume curve.
- A plateau in spirometry correlated with a larger esophageal diameter and reduced peak expiratory flow (PEF).
- Improvement in spirometry after surgery was not significant, but FEV1 improved more than FVC.

## Abstract

Background: Achalasia is an esophageal motor disorder characterized by aperistalsis and the failure of the relaxation of the lower esophageal sphincter. We want to find out whether external compression or recurrent micro-aspiration of undigested food has a functional effect on the airway. Methods: The aim of this research was to analyze the influence of achalasia on the peak expiratory flow and flow–volume curve. All of the 110 patients performed spirometry. Results: The mean diameter of the esophagus was 5.4 ± 2.1 cm, and nine of the patients had mega-esophagus. Seven patients had a plateau in the inspiratory part of the flow–volume curve, which coincides with the patients who had mega-esophagus. The rest of the patients had a plateau in the expiration part of the curve. The existence of a plateau in the diameter of the esophagus of more than 5 cm was significant (p 0.003). Statistical significance between the existence of a plateau and a lowered PEF (PEF < 80) has been proven (p 0.001). Also, a statistical significance between the subtype and diameter of more than 4 cm has been proved. There was no significant improvement in the PEF values after operation. In total, 20.9% of patients had a spirometry abnormality finding. The frequency of the improvement in the spirometry values after surgery did not differ significantly by achalasia subtype. The improvement in FEV1 was statistically significant compared to the FVC values. Conclusions: Awareness of the influence of achalasia on the pulmonary parameters is important because low values of PEF with a plateau on the spirometry loop can lead to misdiagnosis. The recognition of various patterns of the spirometry loop may help in identifying airway obstruction caused by another non-pulmonary disease such as achalasia.