Thoracoabdominal pressure gradient and gastroesophageal reflux: insights from lung transplant candidates

Abstract

Advanced lung disease is associated with gastroesophageal reflux disease (GERD). The thoracoabdominal pressure gradient (TAPG) facilitates gastroesophageal reflux, but the effects of TAPG on gastroesophageal reflux in patients with pulmonary disease have not been well defined. Patients diagnosed with end-stage lung disease are expected to have the most extreme derangement in respiratory mechanics. The aim of this study is to explore the relationship between TAPG and reflux in lung transplant (LTx) candidates. We reviewed LTx recipients who underwent pretransplant esophageal high-resolution manometry and a 24-hour pH study. Patients were excluded if they were undergoing redo LTx, had manometric hiatal hernia, or had previously undergone foregut surgery. TAPG was defined as the intra-abdominal pressure minus the intrathoracic pressure during inspiration. Adjusted TAPG was calculated by the TAPG minus the resting lower esophageal sphincter (LES) pressure (LESP). Twenty-two patients with normal esophageal function tests (i.e., normal esophageal motility with neither manometric hiatal hernia nor pathological reflux on 24-hour pH monitoring) were selected as the pulmonary disease-free control group. In total, 204 patients underwent LTx between January 2015 and December 2016. Of these, 77 patients met inclusion criteria. We compared patients with obstructive lung disease (OLD, n = 33; 42.9%) and those with restrictive lung disease (RLD, n = 42; 54.5%). 2/77 patients (2.6%) had pulmonary arterial hypertension. GERD was more common in the RLD group than in the OLD group (24.2% vs. 47.6%, P = 0.038). TAPG was similar between the OLD group and the controls (14.2 vs. 15.3 mmHg, P = 0.850); however, patients in the RLD group had significantly higher TAPG than the controls (24.4 vs. 15.3 mmHg, P = 0.002). Although TAPG was not correlated with GERD, the adjusted TAPG correlated with reflux in all 77 patients with end-stage lung disease (DeMeester score, rs = 0.256, P = 0.024; total reflux time, rs = 0.259, P = 0.023; total number of reflux episodes, rs = 0.268, P = 0.018). Additionally, pathological reflux was seen in 59.1% of lung transplant candidates with adjusted TAPG greater than 0 mmHg (i.e., TAPG exceeding LESP); GERD was seen in 30.9% of patients who had an adjusted TAPG ≤ 0 mmHg. In summary, TAPG varies based on the underlying cause of lung disease. Higher adjusted TAPG increases pathological reflux, even if patients have normal antireflux anatomy and physiology (i.e., no hiatal hernia and manometrically normal LES function). Adjusted TAPG may provide further insights into the pathophysiology of GERD.

Esophageal disease in lung transplant patients

“…These patients had higher DeMeester greater prevalence of pathological reflux, higher total time pH <4, and more total number of reflux episodes compared with patients who had adjusted thoracoabdominal pressure gradient ≤0 mmHg (15.2 vs. 6.3, P=0.006; 59.1 vs. 30.9%, P=0.022; 4.5 vs. 1.5%, P=0.003; 66.5 vs. 23.4, P=0.012, respectively). The study supported the claim that especially in patients with restrictive lung disease, that ventilator mechanics and an elevated adjusted thoracoabdominal pressure gradient play a role in the development of GERD (8).…”

“…The lung transplant population has a heterogeneous mix of etiologies, many with different risk factors for esophageal dysfunction as demonstrated in a number of studies (8,9). Connective tissue disease such as systemic sclerosis and scleroderma are commonly linked with pulmonary disease and can affect multiple systems including the gastrointestinal system.…”

Foregut function before and after lung transplant

“…15 Intra-abdominal pressure (AP), intrathoracic pressure (TP), TAPG, and adjusted TAPG were measured during a resting period without swallowing or esophageal peristalsis (Figure 1), according to previously described methods. 16 Briefly, AP was defined as the pressure 1 cm below the lower border of the crural diaphragm at inspiration (referenced to atmospheric pressure), TP was defined as the pressure 5 cm above the upper border of the LES at inspiration (referenced to atmospheric pressure), and TAPG was calculated as AP minus TP. LESP, referenced to the pressure at the same level of AP measurement (1 cm below the lower border of the crus) was also assessed, and adjusted TAPG was calculated as TAPG minus pressure at the same level of AP measurement.…”

“…Presumably, gastroesophageal reflux can be induced if TAPG overcomes LESP, which works as a fundamental barrier to reflux. 16,17 Manometric esophageal length between the lower border of the upper esophageal sphincter and the upper border of the LES at the end inspiration was assessed (Figure 1). The esophageal length index (ELI), which is the ratio of endoscopic esophageal length (centimeters) to patient height (meters), has been proposed by Yano and colleagues.…”

Prevalence and Natural History of Barrett’s Esophagus in Lung Transplant: A Single-Center Experience

“…The purpose of the EGDs was twofold: (1) to look for stigmata of GERD, and (2) for BE surveillance. We have recently shown that derangement of lung conditions affects the transdiaphragmatic pressure gradient, which can facilitate gastroesophageal reflux [5], and we therefore carry out full foregut examinations early in the post-LTx period. Surveillance endoscopies were performed annually in patients with nondysplastic BE, with fourquadrant biopsies at 1-cm intervals along the length of the involved segment of esophagus.…”