Characterization of haustral activity in the human colon

The human colon consists of a string of haustral compartments; hence all colonic motility involves haustra, yet contraction patterns are rarely discussed from the perspective of haustra. Haustral activity was analyzed in 21 healthy subjects using an 84-sensor manometry catheter with 1 cm spacing; haustra were on average 4.6 cm long, hence their activity was monitored by 4-5 sensors. On average 47% of the haustra were intermittently active for ~ 30% of the time; 2402 periods of haustra activity were analyzed. Intrahaustral activity showed rhythmic pressure waves centred around a frequency of 2-6 cpm or 7-15 cpm, or a checkerboard segmentation pattern. Boundaries of the haustra showed rhythmic pressure activity at a dominant frequency pf 3 cpm with or without elevated baseline pressure. The haustral activity was a low-amplitude motor pattern, 5-30 mmHg above baseline pressure. The intrahaustral rhythmic pressure waves propagated in a mixed pattern: retrograde, antegrade and simultaneous, with the simultaneous appearance dominating. Active haustra often showed no boundary activity probably allowing transit to neighbouring haustra. Haustral boundaries are seen at the same sensor for the 6-8 hr study duration, indicating that they do not propagate. Based on previous studies we infer that the orchestration of haustral activity involves pacemaker activity from ICC-SMP. High amplitude propagating pressure waves (HAPWs), were often followed by a cyclic motor pattern at a frequency ~ 12 cpm dissolving into haustral activity at that frequency. The HAPW may be composed of neurally-induced summated pressure waves at ~ 12 cpm.

Insights into the natural history of spontaneous intracranial hypotension from infusion testing

ObjectiveTo assess the pathophysiologic changes in patients with spontaneous intracranial hypotension (SIH) based on measures of CSF dynamics, and on the duration of symptoms, in a retrospective case-controlled study.MethodsWe included consecutive patients investigated for SIH at our department from January 2012 to February 2018. CSF leak was considered confirmed if extrathecal contrast spillage was seen on imaging (CT or MRI) after intrathecal contrast application, or dural breach was detected by direct intraoperative visualization. We divided patients with a confirmed CSF leak into 3 groups depending on the symptom duration, as follows: ≤10, 11–52, and >52 weeks. Clinical characteristics and measures of CSF fluid dynamics obtained by computerized lumbar infusion testing were analyzed over time and compared with a reference population.ResultsAmong the 137 patients included, 69 had a confirmed CSF leak. Whereas 93.1% with <10 weeks of symptoms displayed typical orthostatic headache, only 62.5% with >10 weeks of symptoms did (p = 0.004). Analysis of infusion tests revealed differences between groups with different symptom duration for CSF outflow resistance (p < 0.001), lumbar baseline pressure (p = 0.013), lumbar plateau pressure (p < 0.001), baseline pressure amplitude (p = 0.021), plateau pressure amplitude (p = 0.001), pressure–volume index (p = 0.001), elastance (p < 0.001), and CSF production rate (p = 0.001). Compared to the reference population, only patients with acute symptoms showed a significantly altered CSF dynamics profile.ConclusionA CSF leak dramatically alters CSF dynamics acutely, but the pattern changes over time. There is an association between the clinical presentation and changes in CSF dynamics.

Longitudinal Evaluation of Pressure Applied by Custom Fabricated Garments Worn by Adult Burn Survivors

Custom fabricated pressure garments (PGs) are commonly used to prevent or treat hypertrophic scars (HSc) after burn injury. However, there is minimal scientific evidence quantifying pressure after standard measurement and fitting techniques. Adult burn survivors whose HSc was treated with PGs were recruited. Trained fitters, blinded to study locations and results, took the garment measures. Once the PGs arrived and were fitted, baseline pressure measures at HSc and normal skin (NS) sites were determined using the Pliance X® System. Pressure readings were repeated at 1, 2, and 3 months. The mean baseline pressure was 15.3 (SD 10.4) at HSc and 13.4 (SD 11.9) at NS sites. There was a significant reduction during the first month at both sites (P = .0002 HSc; P = .0002 NS). A multivariable linear regression mixed model, adjusting for garment type, baseline pressure, and repeated measures, revealed further reduction at HSc sites between 1 and 2 months (P = .03). By 3 months, the mean pressure reduced to 9.9 (SD 6.7) and 9.15 (SD 7.2) mm Hg at HSc and NS sites, respectively. At each time point, the pressure was higher at HSc compared with NS but was significantly different only at 1 month (P = .01). PGs were worn ≥12 hr/d 7 d/wk. PGs that apply 15 to 25 mm Hg pressure significantly improve HSc; however, immediately after fitting newly fabricated PGs, the average pressure was at the bottom of the recommended range and by 1 month was significantly below. Clinicians are likely underestimating the dosage required and the significant pressure loss within the first 2 months.

Effect of a Waterproof Device in the Noninvasive Ventilation Circuit on patient-machine Synchronization

Objective: Investigate the effect of connecting a waterproof device at the front end of the piezometric tube on pressure transmission and patient-machine synchronization during the noninvasive ventilation. Method: In test 1, the waterproof device was connected to the piezometric tube and put into a closed container, the pressure inside the container was varied to observe the corresponding pressure change in the piezometric tube. In test 2, a waterproof device was connected in front of the piezometric tube during noninvasive ventilation.12 subjects were received noninvasive ventilator so that dynamic changes of the pressure inside the mask (Pmask) and piezometric tube (Ptube) could be measured. Results: In test 1, when the pressure in the container was gradually increased to 50 cmH2O and then decreased to 0, the pressure inside the piezometric tube changed synchronously with the pressure inside the container, with no statistically significant difference between the pressures (0.009 ± 0.138) cmH2O. In test 2, there was no significant increase in triggering time, pressure, and power after connecting the waterproof device at the front end of the piezometric tube. There was no significant difference in the platform pressure and baseline pressure as measured by Pmask, before and after connecting the waterproof device. Finally, there was no significant difference in the platform pressure and baseline pressure between Pmask and Ptube after connecting the waterproof device.

Essential Variables and Breath Types

‘Essential Variables and Breath Types’ describes the eight types of mechanical breath in terms of their five essential variables: triggering, cycling, controlling, targeting, and baseline pressure. This chapter begins with detailed descriptions of these variables, including their definitions, mechanisms, and options. It ends by defining the eight mechanical breath types as different combinations of these variables. The author describes how these variables are used to define such breath types as volume control or pressure support. The author incorporates into the discussion abnormalities of each of these variables.