Respiratory comfort and breathing pattern during volume proportional assist ventilation and pressure support ventilation: a study on volunteers with artificially reduced compliance

OBJECTIVE

To assess respiratory comfort and associated breathing pattern during volume assist (VA) as a component of proportional assist ventilation and during pressure support ventilation (PSV).

DESIGN

Prospective, double-blind, interventional study.

SETTING

Laboratory.

SUBJECTS

A total of 15 healthy volunteers (11 females, 4 males) aged 21-31 yrs.

INTERVENTIONS

Decreased respiratory system compliance was simulated by banding of the thorax and abdomen. Volunteers breathed via a mouthpiece with VA and PSV each applied at two levels (VA, 8 cm H2O/L and 12 cm H2O/L; PSV, 10 cm H2O and 15 cm H2O) using a positive end-expiratory pressure of 5 cm H2O throughout. The study was subdivided into two parts. In Part 1, volunteers breathed three times with each of the four settings for 2 mins in random order. In Part 2, the first breath effects of multiple, randomly applied mode, and level shifts were studied.

MEASUREMENTS AND MAIN RESULTS

In Part 1, the volunteers were asked to estimate respiratory comfort in comparison with normal breathing using a visual analog scale. In Part 2, they were asked to estimate the change of respiratory comfort as increased, decreased, or unchanged immediately after a mode shift. Concomitantly, the respiratory pattern (change) was characterized with continuously measured tidal volume, respiratory rate, pressure, and gas flow. Respiratory comfort during VA was higher than during PSV. The higher support level was less important during VA but had a major negative influence on comfort during PSV. Both modes differed with respect to the associated breathing pattern. Variability of breathing was higher during VA than during PSV (Part 1). Changes in respiratory variables were associated with changes in respiratory comfort (Part 2).

CONCLUSIONS

For volunteers breathing with artificially reduced respiratory system compliance, respiratory comfort is higher with VA than with PSV. This is probably caused by a better adaptation of the ventilatory support to the volunteer's need with VA.

Breathing pattern associated with respiratory comfort during automatic tube compensation and pressure support ventilation in normal subjects

BACKGROUND

Automatic tube compensation (ATC) is a new option to support spontaneously breathing tracheally intubated patients. We have previously demonstrated an increased respiratory comfort compared to pressure support ventilation (PSV) in volunteers. Here we characterized the breathing pattern during ATC associated with respiratory comfort in comparison to PSV. Furthermore, we studied whether ATC can be substituted by a simple modification of PSV.

METHODS

We exposed 10 volunteers breathing through a 7.5 mm endotracheal tube via mouthpiece to PSV with 1) immediate and 2) delayed pressure rise and to 3) ATC. Immediate changes of the respiratory pattern after mode shifts were analyzed in detail. Furthermore, the volunteers were instructed to indicate changes in comfort after transitions between these modes as increased, unchanged, or decreased.

RESULTS

Decreased comfort was associated with a substantial increase of tidal volume, minute ventilation, gas flow, and pressure. No differences in respiratory comfort were perceived between immediate and delayed pressure rise during PSV.

CONCLUSION

PSV resulted in excessive tidal volumes and airflow, which was perceived as discomfort. This cannot be avoided by a delayed pressure rise but can be by the more comfortable ATC. ATC seems to adapt better to the ventilatory demand than PSV.

Impact of Stereotactic Ventriculocisternostomy on Delayed Cerebral Infarction and Outcome After Subarachnoid Hemorrhage

Background and Purpose- Delayed cerebral infarction (DCI) is an important cause of morbidity and mortality in patients with aneurysmal subarachnoid hemorrhage (aSAH). Stereotactic catheter ventriculocisternostomy (STX-VCS) and fibrinolytic/spasmolytic lavage is a new method for DCI prevention. Here, we assess the effects of implementing STX-VCS in an unselected aSAH patient population of a tertiary referral center. Methods- Retrospective cohort study of all consecutive aSAH patients admitted to a neurosurgical referral center during a 7-year period (April 2012 to April 2019). Midterm STX-VCS was introduced and offered to patients at high risk for DCI. We compared the incidence and burden of DCI, neurological outcome, and the use of induced hypertension and endovascular rescue therapy in this consecutive aSAH population 3.5 years before versus 3.5 years after STX-VCS became available. Results- Four hundred thirty-six consecutive patients were included: 222 BEFORE and 214 AFTER. Fifty-seven of 214 (27%) patients received STX-VCS. Stereotactic procedures resulted in one (2%) subdural hematoma. Favorable neurological outcome at 6 months occurred in 118 (53%) patients BEFORE and 139 (65%) patients AFTER (relative risk, 0.79 [95% CI, 0.66-0.95]). DCI occurred in 40 (18.0%) patients BEFORE and 17 (7.9%) patients AFTER (relative risk, 0.68 [95% CI, 0.57-0.86]), and total DCI volumes were 8933 (100%) and 3329 mL (36%), respectively. Induced hypertension was used in 97 (44%) and 30 (15%) patients, respectively (relative risk, 0.55 [95% CI, 0.46-0.65]). Thirty (13.5%) patients BEFORE versus 5 (2.3%) patients AFTER underwent endovascular rescue therapies (relative risk, 0.17 [95% CI, 0.07-0.42]). Conclusions- Selecting high-risk patients for STX-VCS reduced the DCI incidence, burden, and related mortality in a consecutive aSAH patient population. This was associated with an improved neurological outcome.

Cerebral Abscess Caused by Listeria monocytogenes: Case Report and Literature Review

BACKGROUND

 Listeria monocytogenes is an opportunistic gram-positive, facultative intracellular bacterium that causes invasive diseases mostly in pregnant women and immunosuppressed patients. Despite the predilection toward the central nervous system (CNS), it usually causes meningitis and meningoencephalitis, whereas brain abscesses are very uncommon.

CASE PRESENTATION

 We describe the case of a 69-year-old homeless patient with a brain abscess due to L. monocytogenes who was successfully treated surgically by a guided stereotactic aspiration and antibiotic therapy with ampicillin and gentamicin. Our patient was discharged after 4 weeks of therapy without neurologic deficits. Additionally, we provide a review of the literature of brain abscesses caused by L. monocytogenes.

CONCLUSIONS

 This case highlights the need to drain cerebral abscesses and culture pus to correctly treat patients with antibiotics, especially given the high mortality rate of this infectious entity.

Are drivers more likely to injure their right or left foot in a frontal car crash: a crash and biomechanical investigation

In this study we hypothesized that for frontal crashes, the driver was more likely to sustain foot injury than the front seated passenger and the right foot was more likely to be injured than the left because the driver's right foot was positioned in dorsiflexion and eversion during the crash and less able to tolerate crash forces. Seventeen CIREN frontal crashes were studied to document the circumstances and resulting foot injuries. NASS data was sampled to determine frequencies of injury to foot side and occupant position. Biomechanically, matched pairs of cadaveric feet were tested in compression with one in dorsiflexion, and the other, dorsiflexion, and eversion. Results showed that drivers were more likely than passengers to sustain a foot or ankle injury and this was almost exclusively due to a higher frequency of right foot injuries in drivers. Braking, with significant toepan intrusion, was associated with an increase in both right and left foot injuries in drivers. Biomechanically, 9 of 15 pairs tested provided useable data. There was a significant decrease in load to failure between specimens forced into dorsiflexion and eversion (mean, 4107 N, sd = 1630 N) compared with dorsiflexion alone (mean, 6468 N, sd = 2435 N, p = 0.001). The majority (16 of 17) of foot injuries in the CIREN cases were to drivers of which 13 injured their right foot and ankle. An implication of this work is that if thresholds based on data from dorsiflexion and compression loading are used to predict foot and ankle injury in frontal crashes they may not represent that population of drivers who are braking at the time of the crash and could suffer injuries at forces lower than current threshold values.

Cisternal Blood Clearance Attenuates Systemic Inflammatory Response After Subarachnoid Hemorrhage

BACKGROUND

Aneurysmal subarachnoid hemorrhage (SAH) frequently triggers systemic inflammatory response syndrome (SIRS). SIRS has been associated with inferior outcomes and, specifically, delayed cerebral infarction after aneurysmal SAH. Here, we assess the impact of intracranial blood clearance through stereotactic catheter ventriculocisternostomy on SIRS in patients with aneurysmal SAH.

METHODS

We assessed daily SIRS criteria (heart rate > 90 beats/min, respiratory rate > 20 breaths/min or abnormal respiratory coefficient, temperature > 38 °C or < 36 °C, white blood cell count < 4000 or > 12,000 cells/mm3) between admission and day 21 in 80 consecutive patients who underwent cisternal lavage through stereotactic catheter ventriculocisternostomy from 2015 to 2022. These patients were compared with 80 matched controls who received treatment at our institution between 2010 and 2015. We conducted a mixed effects model analysis using restricted maximum likelihood estimation to assess the effects of treatment groups on the SIRS rate while accounting for repeated measures. Additionally, Bonferroni's correction was employed to examine specific differences between groups at different time points.

RESULTS

The mean percentages of patients meeting SIRS criteria during the first 21 days after aneurysmal SAH were 23% in the matched cohort group and 14% in patients who underwent cisternal lavage (p < 0.001). Additionally, significant differences were observed in the mean leukocyte count (p = 0.047), mean heart rate (p = 0.019), and mean respiratory rate (p = 0.0018) between the two groups. However, there was no significant difference in mean body temperature (p = 0.36).

CONCLUSIONS

Intracranial blood clearance and cisternal lavage after aneurysmal SAH is associated with a decline in SIRS prevalence and severity.

Twist-drill craniostomy with pressure-controlled fibrinolytic irrigation therapy reduces recurrence of chronic subdural hematomas: initial experience in 16 cases

BACKGROUND

Chronic subdural hematoma (cSDH) is prevalent in the elderly, frail, and those on antithrombotic therapy, often resulting in significant morbidity and mortality. Recurrence and reoperation rates are substantial concerns. Emerging evidence suggests that irrigation, drainage, and possibly fibrinolytic therapy, may improve reoperation rates.

OBJECTIVE

To explore safety and efficacy of twist-drill craniostomy (TDC) with pressure-controlled fibrinolytic irrigation therapy (TDC-FIT) in reducing recurrence rates of cSDH compared to conventional TDC with subdural passive drainage.

METHODS

A retrospective study included 314 patients treated with TDC and 16 patients treated with TDC-FIT between January 2021, and March 2024. The primary endpoint was the reoperation rate due to symptomatic recurrence or persistence of cSDH at 6 months. Secondary endpoints included hematoma resolution, perioperative complications, and the impact of antithrombotic therapy and preoperative membrane formation.

RESULTS

Reoperation was required in 107 (34.1 %) TDC patients and in one (6.3 %) TDC-FIT patient (P = .026). Hematoma membranes (OR 2.6, 95 % CI 1.6-4.3, P < .001) and dual antithrombotic therapy (OR 10.3, 95 % CI 1.1-93.3, P = .041) were significantly associated with reoperation in the TDC cohort. TDC-FIT showed superior hematoma resolution with a similar complication profile and functional outcome. TDC-FIT patients had a significantly lower reoperation rate despite a higher presence of hematoma membranes (75 % vs. 34.7 %, P = .002).

CONCLUSION

Preliminary data on TDC-FIT suggests improved reoperation rate and membranous hematoma resolution with comparable safety profiles to conventional TDC. Further prospective studies are needed to validate these findings in larger cohorts.