Selective dysfunction of the crural diaphragm in patients with chronic restrictive and obstructive lung disease

Abstract

Background: Gastroesophageal reflux (GER) is known to be associated with chronic lung diseases. The driving force of GER is the transdiaphragmatic pressure (Pdi) generated mainly by costal and crural diaphragm contraction. The latter also enhances the esophagogastric junction (EGJ) pressure to guard against GER.

Methods: The relationship between Pdi and EGJ pressure was determined using high resolution esophageal manometry in patients with interstitial lung disease (ILD, n = 26), obstructive lung disease (OLD, n- = 24), and healthy subjects (n = 20).

Key results: The patient groups did not differ with respect to age, gender, BMI, and pulmonary rehabilitation history. Patients with ILD had significantly higher Pdi but lower EGJ pressures as compared to controls and OLD patients (p < 0.001). In control subjects, the increase in EGJ pressure at all-time points during inspiration was greater than Pdi. In contrast, the EGJ pressure during inspiration was less than Pdi in 14 patients with ILD and 7 patients with OLD. The drop in EGJ pressure was usually seen after the peak Pdi in ILD group (p < 0.0001) and before the peak Pdi in OLD group, (p = 0.08). Nine patients in the ILD group had sliding hiatus hernia, compared to none in control subjects (p = 0.003) and two patients in the OLD, (p = 0.04).

Conclusions and inferences: A higher Pdi and low EGJ pressure, and dissociation between Pdi and EGJ pressure temporal relationship suggests selective dysfunction of the crural diaphragm in patients with chronic lung diseases and may explain the higher prevalence of GERD in ILD as seen in previous studies.

Keywords: crural diaphragm; esophagogastric junction; gastroesophageal reflux; hiatus hernia; lower esophageal sphincter; transdiaphragmatic pressure gradient.

FIGURE 1

(A), Schematic diagram showing position of the manometer catheter in the GI tract with sensors at 1 cm intervals. (B), Manometry recording showing pressure changes (mmHg) in the esophagus, stomach, and EGJ during tidal and deep breathing in a control subject. The pressure from each sensor is displayed as heat map along the entire length of the catheter. Pressure in the esophagus drops during inspiration and increases during expiration while pressure in the EGJ and stomach increases during inspiration and decreases during expiration. The white boxes represent the areas selected to measure mean pressures in the three compartments in this study. EGJ, esophago-gastric junction; GI, gastrointestinal.

FIGURE 2

Representative manometry recordings showing changes in the esophageal, EGJ and stomach pressure during tidal and deep breaths in a healthy control, a patient with ILD and a patient with OLD. (A, B), In normal subject, the esophageal pressure falls, EGJ pressure increases, and stomach pressure increases during inspiration. (C, D) In patient with ILD, the breaths are deeper and faster. The fall in esophageal pressure is greater and EGJ pressure increase is relatively smaller causing higher Pdi and lower pressure difference between Pdi and EGJ pressure. (E, F) The changes in esophageal, EGJ and stomach pressure in patient with OLD are similar to normal subject. EGJ, esophago-gastric junction; ILD, interstitial lung disease; OLD, obstructive lung disease; Pdi, transdiaphragmatic pressure gradient.

FIGURE 3

(A), Representative image of a control subject showing the EGJ pressure during a deep breath. (B), The increase in EGJ pressure during inspiration lasts for the duration of inspiration and remains higher than the Pdi throughout inspiration. (D, E), In patient with ILD the fall in esophageal pressure is greater leading to higher Pdi. The EGJ pressure increase is smaller causing the Pdi and EGJ waveforms to intersect during inspiration. In addition, the EGJ pressure increase does not last during the entire period of inspiration, it starts to fall before the end of negative pressure wave in the esophagus. (G, H) In patients with OLD, the EGJ pressure increases higher than the Pdi and lasts throughout the duration of inspiration. (C, F, I), The graphs show the Pdi and EGJ pressure in each individual subject at the peak of forced inspiration in three groups respectively. Patients with ILD generate lower EGJ pressure and higher Pdi values as compared to normal subjects and patient with OLD. EGJ, esophago-gastric junction; ILD, interstitial lung disease; OLD, obstructive lung disease; Pdi, transdiaphragmatic pressure gradient.

FIGURE 4

(A–D), Simultaneous pressure waveforms of Pdi and EGJ pressure during deep inspiration showing four types of intersections: (A). No intersections, (B), EGJ pressure drops before the peak of Pdi waveform (ascending limb). (C), EGJ pressure drops below the Pdi after the peak of Pdi waveform (descending limb), (D), EGJ pressure drops below Pdi before and after the peak of Pdi waveform (both limbs). (E). Graph showing the number of patients in each group with each type of EGJ-Pdi waveform intersection. EGJ, esophago-gastric junction; Pdi, transdiaphragmatic pressure gradient.