794 DOES TRACHEOSTOMY PREDISPOSE GASTROESOPHAGEAL REFLUX?

Lung diseases have a strong relationship with gastroesophageal reflux disease (GERD). It has been previously demonstrated that conditions such as tracheal stenosis, asthma and even lung transplantation may worsen with reflux and these patients have few symptoms of GERD. With the COVID-19 pandemic, the number of people who needed mechanical ventilation and tracheostomy increased. Our objective was to demonstrate the prevalence of gastro-oesophageal reflux in patients with tracheostomy and describe its characteristics. Methods Esophageal manometry and 24 h pH-metry was performed in 137 consecutive patients with a tracheostomy already in a chronic phase, independent of symptoms. Inquire on respiratory and digestive symptoms was also carried out at the time of the examination. Prevalence of gastroesophageal reflux was identified in this population and description of the groups with reflux and without it, as well as comparison between them. Results Of the 137 patients, 49 were male, the average age was 40.94 ± 17.3 and the body mass index was 26.3 ± 4.85. The prevalence of gastroesophageal reflux was 45.2%. Baseline characteristics were similar between the groups with and without reflux. In the reflux group, the mean DeMeester score was 36.5 ± 20.8 and the presence of lower sphincter hypotonia was found in only 31% of the patients and was not correlated with reflux between the groups (p = 0.285). Regarding the symptoms, 48% had heartburn symptoms and only 30% had a combination of typical symptoms (heartburn + regurgitation). Conclusion The presence of tracheostomy is related to an increased prevalence of reflux, even without typical symptoms most of the time. The mechanism for this is still unknown, perhaps the altered respiratory dynamics has a role. These patients should be investigated with functional exams if they develop any condition that may be affected by reflux.

A new method to measure inter-breath intervals in infants for the assessment of apnoea and respiratory dynamics

Background Respiratory disorders, including apnoea, are common in preterm infants due to their immature respiratory control and function compared with term-born infants. However, our inability to accurately measure respiratory rate in hospitalised infants results in unreported episodes of apnoea and an incomplete picture of respiratory dynamics. Methods We develop, validate and use a novel algorithm to identify inter-breath intervals (IBIs) and apnoeas in infants. In 42 infants (a total of 1600 hours of recordings) we assess IBIs from the chest electrical impedance pneumograph using an adaptive amplitude threshold for the detection of individual breaths. The algorithm is refined by comparing its accuracy with clinically-observed breaths and pauses in breathing. We also develop an automated classifier to differentiate periods of true central apnoea from artefactually low amplitude signal. We use this algorithm to explore its ability to identify morphine-induced respiratory depression in 15 infants. Finally, in 22 infants we use the algorithm to investigate whether retinopathy of prematurity (ROP) screening alters the IBI distribution. Findings 88% of the central apnoeas identified using our algorithm were missed in the clinical notes. As expected, morphine caused a shift in the IBI distribution towards longer IBIs, with significant differences in all IBI metrics assessed. Following ROP screening, there was a shift in the IBI distribution with a significant increase in the proportion of pauses in breathing that lasted more than 10 seconds (t-statistic=1.82, p=0.023). This was not reflected by changes in the monitor- derived respiratory rate or episodes of apnoea recorded on clinical charts. Interpretation Better measurement of infant respiratory dynamics is essential to improve care for hospitalised infants. Use of the novel IBI algorithm demonstrates that following ROP screening increased instability in respiratory dynamics can be detected in the absence of clinically-significant apnoeas. Funding Wellcome Trust and Royal Society

The influence of heat load on Merino sheep. 2. Body temperature, wool surface temperature and respiratory dynamics

Context Australia exports ~2 million sheep annually. On these voyages, sheep can be exposed to rapidly changing ambient conditions within a short time, and sheep may be exposed to periods of excessive heat load. Aims The aim of this study was to define the responses of sheep exposed to incremental heat load under simulated live export conditions. The study herein describes the influence of heat load on wool surface temperature, body temperature (rumen temperature (TRUM), °C; and rectal temperature (TREC), °C) and respiratory dynamics (respiration rate, breaths/min; and panting score (PS)) of sheep under live export conditions. In addition, the relationship between body temperature and respiratory dynamics was investigated. Methods A total of 144 Merino wethers (44.02 ± 0.32 kg) were used in a 29-day climate controlled study using two cohorts of 72 sheep (n = 2), exposed to two treatments: (1) thermoneutral (TN; ambient temperature was maintained between 18°C and 20°C), and (2) hot (HOT; ambient temperature minimum and maximum were 22.5°C and 38.5°C respectively). Sheep in the HOT treatment were exposed to heat load simulated from live export voyages from Australia to the Middle East. Respiration rate, PS and wool surface temperature (°C) data were collected four times daily, at 3-h intervals between 0800 hours and 1700 hours. Rectal temperatures were collected on five occasions at 7-day intervals. These data were evaluated using a repeated measures model, assuming a compound symmetry covariance structure. Individual TRUM were obtained via rumen boluses at 10-min intervals between Days 23 and 29 of Cohort 2. Individual TRUM data were collated and converted to an hourly mean TRUM for each sheep, these data were then used to determine the hourly mean TRUM for TN and HOT, then analysed using a first order autoregressive repeated measures model. Additionally, the relationship between respiratory dynamics and TRUM were investigated using a Pearson’s correlation coefficient, a partial correlation coefficient and a multivariate analysis of variance. Key results The respiration rate of the HOT sheep (140 ± 3.55 breaths/min) was greater (P < 0.01) than that of the TN sheep (75 ± 3.55 breaths/min). Similarly, the PS of the HOT (1.5 ± 0.02) sheep was greater (P = 0.009) compared with the TN sheep (1.2 ± 0.02). Wool surface temperatures and TREC were greater (P < 0.05) for the HOT sheep than for the TN sheep. There were treatment (P < 0.0001), hour (P < 0.0001), day (P = 0.038) and treatment × hour (P < 0.0001) effects on the TRUM of TN and HOT sheep. Conclusions The climatic conditions imposed within the HOT treatment were sufficient to disrupt the thermal equilibrium of these sheep, resulting in increased respiration rate, PS, TREC and TRUM. Implications These results suggest that the sheep were unable to completely compensate for the imposed heat load via respiration, thus resulting in an increase in TREC and TRUM.

Efficacy of combination therapy with dexmedetomidine for benzodiazepines-induced disinhibition during endoscopic retrograde cholangiopancreatography

Background: Benzodiazepines (BZDs) and analgesics are widely used for conscious sedation during endoscopic ultrasound (EUS) or endoscopic retrograde cholangiopancreatography (ERCP). However, endoscopic procedures are sometimes discontinued because of BZD-induced disinhibitory reactions such as excessive movement. We evaluated the usefulness of dexmedetomidine (DEX) for BZD-induced disinhibition in ERCP. Methods: Between February 2018 and August 2019, 22 patients who underwent EUS or ERCP were enrolled. All patients showed BZD-induced excessive movement at the first examination (BZD group) and received DEX at the second examination (DEX group). The initial DEX dose was 6 μg/kg/h for a 10-min loading, followed by 0.4 μg/kg/h during the procedure. BZDs and analgesics were administered before scope insertion. An additional sedative was administered to achieve a Ramsay sedation scale (RSS) of 4–5. Sedative effect, procedure completion rate, and changes in circulatory and respiratory dynamics were evaluated. Results: Mean RSS scores were significantly higher ( p < 0.001) in the DEX (5.1 ± 0.5) compared with the BZD (4.0 ± 0.5) group. The movement score ( p < 0.001) and number of additional sedatives required ( p < 0.01) were lower in the DEX group. The procedure completion rate was significantly higher in the DEX (95.5%) compared with the BZD group (63.6%; p < 0.05). Significant differences in the frequency of hypotension ( p = 1.00), bradycardia ( p = 0.22), and respiratory depression ( p = 0.68) were not noted between groups. Conclusions: The addition of DEX to BZD therapy yielded better sedative efficacy, lower excessive movement, a reduction in BZDs used, and a higher procedure complete rate. DEX may be used as an alternative method for BZD-induced inhibition during ERCP.