Mechanical properties of the gastro-esophageal junction in health, achalasia, and scleroderma

Background: Manometric assessment of the gastro-esophageal junction (GEJ) i s deceptive in that ignores key dynamic properties of the junction, such as resistance to flow and compliance. Our aim was to investigate the mechanic al properties of the GEJ comprising intraluminal pressure (measured by mano metry), resistance to flow and compliance (measured by resistometry). Metho ds: We studied 8 healthy subjects, 11 patients with achalasia and 11 patien ts with scleroderma. We used a pneumatic resistometer, previously developed and validated in our laboratory. The resistometer consists of a flaccid po lyurethane 5-cm cylinder connected to an electronically regulated nitrogen- injection system; the instrument records nitrogen flow through the cylinder while maintaining a constant pressure gradient between its proximal and di stal ends. By placing the cylinder successively in the proximal stomach and along the GEJ we measured the GEJ-gastric resistance gradient (GEJ resista nce minus gastric resistance) and were able to calculate the cumulative res istance (sum of resistance exerted at each pressure level), peak resistance (at any injection pressure), nil resistance point (injection pressure in m mHg at which GEJ resistance equals gastric resistance), and compliance slop e (flow/pressure relationship). Results: We found that GEJ resistance to fl ow (cumulative resistance, peak resistance, and nil resistance point) is si gnificantly increased in achalasia and decreased in scleroderma (P < 0.05 v ersus health) while GEJ compliance is diminished in achalasia (P < 0.05 ver sus health) and normal in scleroderma. Conclusion: Achalasia is a disease c haracterized by increased GEJ resistance and rigidity. By contrast, althoug h scleroderma is characterized by decreased GEJ resistance, GEJ compliance may be normal.