Postural changes in proximal gastric volume and pressure measured using a gastric barostat

Management of abdominal compartment syndrome in acute pancreatitis

Abdominal compartment syndrome (ACS), defined by the presence of increased intra-abdominal pressure>20mmHg in association with failure of at least one organ system, is a common and feared complication that may occur in the early phase of severe acute pancreatitis (AP). This complication can lead to patient death in the very short term. The goal of this review is to provide the surgeon and intensivist with objective information to help them in their decision-making. In the early phase of severe AP, it is essential to monitor intra-vesical pressure (iVP) to allow early diagnosis of intra-abdominal hypertension or ACS. The treatment of ACS is both medical and surgical requiring close collaboration between the surgical and resuscitation teams. Medical treatment includes vascular volume repletion, prokinetic agents, effective curarization and percutaneous drainage of large-volume ascites. If uncontrolled respiratory or cardiac failure develops or if maximum medical treatment fails, most teams favor performing an emergency xipho-pubic decompression laparotomy with laparostomy. This procedure follows the principles of abbreviated laparotomy as described for abdominal trauma.

Global Physiology and Pathophysiology of Cough: Part 1: Cough Phenomenology - CHEST Guideline and Expert Panel Report

The purpose of this state-of-the-art review is to update the American College of Chest Physicians 2006 guideline on global physiology and pathophysiology of cough. A review of the literature was conducted using PubMed and MEDLINE databases from 1951 to 2019 and using prespecified search terms. We describe the basic phenomenology of cough patterns, behaviors, and morphological features. We update the understanding of mechanical and physiological characteristics of cough, adding a contemporary view of the types of cough and their associated behaviors and sensations. New information about acoustic characteristics is presented, and recent insights into cough triggers and the patient cough hypersensitivity phenotype are explored. Lastly, because the clinical assessment of patients largely focuses on the duration rather than morphological features of cough, we review the morphological features of cough that can be measured in the clinic. This is the first of a two-part update to the American College of Chest Physicians 2006 cough guideline; it provides a more global consideration of cough phenomenology, beyond simply the mechanical aspects of a cough. A greater understanding of the typical features of cough, and their variations, may allow a more informed interpretation of cough measurements and the clinical relevance for patients.

Measuring intrabladder pressure with the head of the bed elevated 30°: evidence to support a change in practice

BACKGROUND

A 30° head-of-bed elevation is recommended for most critically ill patients. Measuring intrabladder pressure with the patient in this position is controversial.

OBJECTIVE

To assess the feasibility of measuring intrabladder pressure with a 30° head-of-bed elevation.

METHODS

A prospective, randomized, and experimental study. Patients had intrabladder pressure measured first while positioned supine with a 30° head-of-bed elevation and 25 mL of saline instilled into the bladder and again after the patients were randomly repositioned to supine without any head-of-bed elevation (flat) or with a 30° head-of-bed elevation while supine or in right lateral or left lateral position with either 25, 50, or 200 mL of saline instilled into the patient's bladder.

RESULTS

Intrabladder pressures measured with the patient in all 3 head-of-bed elevated positions were higher than pressures measured with patients supine and flat after instillation of 25 mL of saline into the bladder, but intrabladder pressure did not differ between the 30° head-of-bed elevated positions and the supine and flat positions when 50 or 200 mL of saline was instilled into the bladder. Two-way analysis of variance showed a significant interaction between volume of saline instilled (P = .05), patient's position (P = .007), and bladder instill volume and position interaction (P = .004).

CONCLUSION

It is feasible to measure intrabladder pressure with a 30° head-of-bed elevation, and that position could be an alternative to supine positioning of patients for measurement of intrabladder pressure.

Small volumes of feed can trigger transient lower esophageal sphincter relaxation and gastroesophageal reflux in the right lateral position in infants

OBJECTIVE

To investigate the threshold amount of constantly infused feed needed to trigger lower esophageal sphincter relaxation (TLESR) in the right lateral position (RLP) and left lateral position (LLP).

STUDY DESIGN

Eight healthy infants (3 male; gestational age: 32.9 +/- 2.4 weeks; corrected age: 36.1 +/- 1.3 weeks) were studied using an esophageal impedance-manometry catheter incorporating an intragastric infusion port. After tube placement, infants were randomly positioned in RLP or LLP. They were then tube-fed their normal feed (62.5 [40 to 75] mL) at an infusion rate of 160 mL/h. Recordings were made during the feed and 15 minutes thereafter. The study was repeated with the infant in the opposite position.

RESULTS

More TLESRs were triggered in the RLP compared with LLP (4.0 [3.0 to 6.0] vs 2.5 [1.0 to 3.0], P = .027). First TLESR occurred at a significantly lower infused volume in RLP compared with LLP (10.6 +/- 9.4 vs 21.0 +/- 4.9 mL, P = .006). The percentage of feed infused at time of first TLESR was significantly lower in RLP compared with LLP (17.6% +/- 15.5% vs 35.4% +/- 8.02%, P = .005).

CONCLUSIONS

In the RLP, TLESRs and gastroesophageal reflux are triggered at volumes unlikely to induce gastric distension.

Diminished functional association between proximal and distal gastric motility in critically ill patients

OBJECTIVE

This study examined the effects of critical illness on the relationship between proximal and distal gastric motor activity during fasting and duodenal nutrient stimulation.

DESIGN

Prospective, case-controlled study.

PATIENTS AND PARTICIPANTS

Ten critically ill patients and ten healthy volunteers.

INTERVENTIONS

Concurrent proximal gastric (barostat) and antro-pyloro-duodenal (manometry) motility were recorded during fasting and during two 60-min duodenal nutrient infusions (Ensure at 1 kcal/min and 2 kcal/min) in random order, separated by a 2-h wash-out period.

RESULTS

Baseline proximal gastric volumes were similar between the two groups. At 10 min nutrient-induced fundic relaxation was lower in patients than healthy subjects (45 +/- 26 vs. 196 +/- 29 ml). In patients the frequency and volume amplitude of fundic waves were also lower. There were fewer propagated antral waves in patients than in healthy subjects during both fasting and nutrient infusion. These were more retrograde, shorter in length and associated with a pyloric contraction. The proportion of fundic waves followed by a distally propagated antral wave was significantly less in patients (0%, 0-8%) than controls 36% (11-44%).

CONCLUSIONS

In critical illness, in addition to impairment of proximal and distal gastric motor activity, the association between the two gastric regions is abnormal. This disturbance may interfere with meal distribution and further contribute to slow gastric emptying in these patients.

Functional association between proximal and distal gastric motility during fasting and duodenal nutrient stimulation in humans

A functional integration exists between proximal and distal gastric motor activity in dogs but has not been demonstrated in humans. To determine the relationship between proximal and distal gastric motor activity in humans. Concurrent proximal (barostat) and distal (antro-pyloro-duodenal (APD) manometry) gastric motility were recorded in 10 healthy volunteers (28 +/- 3 years) during (i) fasting and (ii) two 60-min duodenal infusions of Ensure((R)) (1 and 2 kcal min(-1)) in random order. Proximal and APD motor activity and the association between fundic and propagated antral waves (PAWs) were determined. During fasting, 32% of fundic waves (FWs) were followed by a PAW. In a dose-dependent fashion, duodenal nutrients (i) increased proximal gastric volume, (ii) reduced fundic and antral wave (total and propagated) activity, and (iii) increased pyloric contractions. The proportion of FWs followed by a distal PAW was similar between both infusions and did not differ from fasting. During nutrient infusion, nearly all PAWs were antegrade, propagated over a shorter distance and less likely to traverse the pylorus, compared with fasting. In humans, a functional association exists between proximal and distal gastric motility during fasting and duodenal nutrient stimulation. This may have a role in optimizing intra-gastric meal distribution.

Impedance monitoring shows that posture and a meal influence gastro-oesophageal reflux composition and frequency

Impedance monitoring determines reflux composition as liquid and/or gas, and we assess with impedance the effect of posture and a meal on reflux composition. Twenty-nine gastro-oesophageal reflux disease (GORD) patients and 10 normal volunteers underwent simultaneous impedance, manometry and pH for three 40-min periods, each 20-min upright, 10-min left side and 10-min right side. One period was fasting, and two postprandial. We found that reflux event composition on the right side was liquid-only near exclusively (93%). In contrast, 85% of reflux on the left side and 74% upright was gas-only or liquid and gas (P < 0.001). More gas-only reflux occurred fasting (80%) than postprandial (P < 0.01). Reflux composition was similar in the study groups and two postprandial periods (P > 0.25). After confirming gas reflux suppression on the right side, a pilot study assessed gastric anatomy as a cause. Five achalasia patients had fluid injected into the stomach at endoscopy, and the EG junction was submerged below liquid-only on the right side. We conclude that reflux is nearly always liquid-only on the right side where the EG junction may be below fluid. Reflux fasting is usually gas-only. Different posture and fasting times may (i) explain variations in acid exposure during pH monitoring and (ii) promote or prevent GORD symptoms.

The effect of macronutrients on gastric volume responses and gastric emptying in humans: A magnetic resonance imaging study

The effects of macronutrients on gastric volume changes, emptying, and gastrointestinal symptoms are incompletely understood. Three liquid meals of 500 ml (fat emulsion, 375 kcal; protein solution, 375 kcal; glucose solution, 400 kcal) were infused into the stomach of 12 healthy volunteers on three occasions. Studies were performed in seated body position using an open-configuration magnetic resonance imaging (MRI) system. MRI imaging sequences, assessing stomach and meal volumes, were performed prior to and at times t = 0, 3, 6, 9, 12, 15, 25, 35, 45, 60, 75, and 90 min after meal administration. Areas under the curve for the early emptying phase (0-15 and 0-45 min) were calculated, and characteristics of the volume curves were analyzed by a gastric emptying model. Gastrointestinal symptoms were assessed by a self-report scale. Initial (t = 0 min) and early postprandial gastric volumes were highest for glucose because of lower initial emptying. However, in the early emptying phase the characteristics of the volume curves for stomach and meal were uniform for all macronutrients. Perceptions of fullness and satiety were linearly associated with postprandial gastric volumes, but not with macronutrient composition. Isovolumic macronutrient meals modulate gastric volume response by initial meal emptying patterns. Macronutrient specific accommodation responses, as shown in barostat studies, are not reflected as gastric volume responses under noninvasive conditions.

Gastric accommodation and motility are influenced by the barostat device: Assessment with magnetic resonance imaging

The barostat is considered the gold standard for evaluation of proximal gastric motility especially for the accommodation response to a meal. The procedure is invasive because it involves the introduction of an intragastric catheter and bag and is not always well tolerated. Moreover, the barostat bag itself may influence motility. Nowadays magnetic resonance imaging (MRI) is able to measure several aspects of gastric motility noninvasively. To evaluate whether the accommodation response of the stomach, observed with the barostat, is present during MRI and whether the barostat interferes with gastric physiology, gastric accommodation, motility, and emptying were studied twice in 14 healthy subjects with MRI using three-dimensional volume scans and two-dimensional dynamic scans once in the presence of a barostat bag and once when the barostat bag was not present. Fasting and postprandial intragastric volumes were significantly higher in the experiment with barostat vs. without barostat (fasting: 350 +/- 132 ml vs. 37 +/- 21 ml, P < 0.0001; postprandial: 852 +/- 126 ml vs. 361 +/- 62 ml, P < 0.0001). No significant differences were found in gastric emptying (88 +/- 41 vs. 97 +/- 40 ml/h, not significant) and contraction frequency between both experiments. The accommodation response observed in the presence of the barostat bag was not observed in the absence of the barostat bag. In conclusion, the presence of an intragastric barostat bag does not interfere with gastric emptying or motility, but the accommodation response measured with the barostat in situ is not observed without the barostat bag in situ. Gastric accommodation is a nonphysiological barostat-induced phenomenon.

Proximal gastric response to small intestinal nutrients is abnormal in mechanically ventilated critically ill patients

AIM: To determine the response of the proximal stomach to small intestinal nutrients in critically ill patients.

METHODS: Proximal gastric motility was measured in 13 critically ill patients (49.3 ± 4.7 years) and 12 healthy volunteers (27.7 ± 2.9 years) using a barostat technique. Recordings were performed at baseline, during a 60-min intra-duodenal infusion of Ensure^® (2 kcal/min), and for 2 h following the infusion. Minimum distending pressure (MDP), intra-bag volume and fundic wave activity were determined.

RESULTS: The MDP was higher in patients (11.7 ± 1.1 vs 7.8 ± 0.7 mmHg; P < 0.01). Baseline intra-bag volumes were similar in the 2 groups. In healthy subjects, a ‘bimodal’ proximal gastric volume response was observed. In patients, the initial increase in proximal gastric volume was small and delayed, but eventually reached a maximal volume similar to that of healthy subjects. In healthy subjects, the proximal gastric volume rapidly returned to baseline level after nutrient infusion (median 18 min). In contrast, the recovery of volume to baseline was delayed in critically ill patients (median 106 min). In 6 patients, the volume had not returned to baseline level 2 hours after nutrient infusion. In patients, fundic volume waves were less frequent (P < 0.05) and had lower amplitude (P < 0.001), compared to healthy subjects.

CONCLUSION: In critical illness, proximal gastric motor responses to small intestinal nutrient stimulation are abnormal.

Gastric motor function and emptying in the right decubitus and seated body position as assessed by magnetic resonance imaging

PURPOSE

To determine the effect of the right decubitus lying body position (RP) on relevant parameters of human gastric motor function in healthy volunteers.

MATERIALS AND METHODS

Postprandial gastric function after ingestion of a solid/liquid meal (150 g/150 mL) was assessed over 90 minutes in volunteers in the RP and seated position (SP). Ten healthy volunteers were imaged using two MRI systems that differed in architecture and field strength. Stomach and intragastric air volume, intragastric meal distribution, gastric emptying, and gastric peristalsis were compared between the RP and SP.

RESULTS

Body position did not affect gastric relaxation (RP, 372 mL vs. SP, 384 mL) and initial gastric volumes (stomach: RP, 458 mL vs. SP, 462 mL; meal: RP, 377 mL vs. SP, 399 mL; intragastric air: RP, 110 mL vs. SP, 98 mL). Postprandial stomach volume and gastric activity (RP and SP, 3.1 minute(-1)) were also similar. Meal emptying showed different characteristics, resulting in a significant but small difference in meal volume of -43 mL at t = 90 minutes (P < 0.05).

CONCLUSION

Gastric MRI in RP is feasible for clinical research assessing gastric motor function. The subtle difference in meal emptying may be induced by posture-dependent vagal activity. This study confirms that MRI is a highly sensitive imaging technique for assessing gastrointestinal function in humans.

Mechanisms of gastro-oesophageal reflux in the lateral decubitus positions

Gastro-oesophageal reflux is more common in the right than in the left lateral position but the reasons why are not well understood. We have therefore studied the mechanisms underlying reflux in the lateral decubitus positions in patients with reflux disease. Fifteen patients with symptomatic reflux and excessive oesophageal acid exposure were studied (nine male, age 25-63 years). Each was intubated with a perfused manometric assembly, incorporating a Dent sleeve, and a pH probe. Following a 30-min basal period, a 400-kCal meal was infused into the stomach and patients were studied for 60 min in each lateral position. Following infusion of the meal, lower oesophageal sphincter (LOS) pressure fell and transient LOS relaxation (TLOSR) frequency increased. Acid reflux episodes were more common in the postprandial period (fasting 0 (0-6) h, first postprandial hour 1 (0-9) h, P = 0.0002, second postprandial hour 1 (0-22) h, P = 0.02) and occurred more than twice as often in the right lateral position (right 3 (0-22) h, left 0 (0-10) h, P = 0.01). However, TLOSRs, swallow-related relaxations and low basal LOS pressures were equally common in both lateral positions. In patients with reflux disease, postprandial reflux is twice as common in the right lateral position. This does not relate to differences in gastro-oesophageal junctional pressure, suggesting that other aspects of barrier function or differences in the intragastric distribution of chyme may be important.