Upper airway collapsibility predicts the response to several non-continuous positive airway pressure (CPAP) interventions for obstructive sleep apnoea (OSA). Measures of upper airway collapsibility cannot be easily performed in a clinical context; however, a patient's therapeutic CPAP requirement may serve as a surrogate measure of collapsibility. The present work aimed to compare the predictive use of CPAP level with detailed physiological measures of collapsibility.

Therapeutic CPAP levels and gold-standard pharyngeal collapsibility measures (passive pharyngeal critical closing pressure (Pcrit ) and ventilation at CPAP level of 0 cmH2 O (Vpassive )) were retrospectively analysed from a randomized controlled trial (n = 20) comparing the combination of oxygen and eszopiclone (treatment) versus placebo/air control. Responders (9/20) to treatment were defined as those who exhibited a 50% reduction in apnoea/hypopnoea index (AHI) plus an AHI<15 events/h on-therapy.

Responders to treatment had a lower therapeutic CPAP requirement compared with non-responders (6.6 (5.4-8.1) cmH2 O vs 8.9 (8.4-10.4) cmH2 O, P = 0.007), consistent with their reduced collapsibility (lower Pcrit , P = 0.017, higher Vpassive P = 0.025). Therapeutic CPAP level provided the highest predictive accuracy for differentiating responders from non-responders (area under the curve (AUC) = 0.86 ± 0.9, 95% CI: 0.68-1.00, P = 0.007). However, both Pcrit (AUC = 0.83 ± 0.11, 95% CI: 0.62-1.00, P = 0.017) and Vpassive (AUC = 0.77 ± 0.12, 95% CI: 0.53-1.00, P = 0.44) performed well, and the difference in AUC for these three metrics was not statistically different. A therapeutic CPAP level ≤8 cmH2 O provided 78% sensitivity and 82% specificity (positive predictive value = 78%, negative predictive value = 82%) for predicting a response to these therapies.

Therapeutic CPAP requirement, as a surrogate measure of pharyngeal collapsibility, predicts the response to non-anatomical therapy (oxygen and eszopiclone) for OSA.

BACKGROUND

Ventilation through small-diameter tubes typically precludes use of a cuff as this will impede the necessary passive outflow of gas alongside the tube's outer surface. Ventrain assists expiration and enables oxygenation and normoventilation through small-bore cannulas or catheters, particularly in obstructed airways. A small-bore ventilation catheter (SBVC; 40 cm long, 2.2 mm inner diameter) with a separate pressure monitoring lumen and a cuff was developed. Efficacy of oxygenation and ventilation with Ventrain through this catheter was investigated in sealed and open airways in a porcine cross-over study.

METHODS

Six pigs were ventilated with Ventrain (15 l/min oxygen, frequency 30 breaths per min, I : E-ratio 1 : 1) through the SBVC, both with the cuff inflated and deflated. Prior to each test they were ventilated conventionally until steady state was achieved.

RESULTS

With an inflated cuff, PaO2 rose instantly and remained elevated (median [range] PaO2 61 [52-69] kPa after 30 min; P = 0.027 compared to baseline). PaCO2 remained stable at 4.9 [4.2-6.2] kPa. After cuff deflation, PaO2 was significantly lower (9 [5-28] kPa at 10 min, P = 0.028) and interventional ventilation had to be stopped prematurely in five pigs as PaCO2 exceeded 10.6 kPa. Pulmonary artery pressures increased markedly in these pigs. Intratracheal pressures were kept between 5 and 20 cmH2 O with the cuff inflated, but never exceeded 2 cmH2 O after cuff deflation.

CONCLUSIONS

The SBVC combines the benefits of a small diameter airway and a cuff. Cuff inflation optimizes oxygenation and ventilation with Ventrain.

CONCLUSIONS

Protective reflexes in the throat area (upper airway) are crucial for breathing. Impairment of these reflexes can cause breathing problems during sleep such as obstructive sleep apnoea (OSA). OSA is very common in people with spinal cord injury for unknown reasons. This study shows major changes in protective reflexes that serve to keep the upper airway open in response to suction pressures in people with tetraplegia and OSA. These results help us understand why OSA is so common in people with tetraplegia and provide new insight into how protective upper airway reflexes work more broadly.

UNASSIGNED

More than 60% of people with tetraplegia have obstructive sleep apnoea (OSA). However, the specific causes are unknown. Genioglossus, the largest upper-airway dilator muscle, is important in maintaining upper-airway patency. Impaired genioglossus muscle function following spinal cord injury may contribute to OSA. This study aimed to determine if genioglossus reflex responses to negative upper-airway pressure are altered in people with OSA and tetraplegia compared to non-neurologically impaired able-bodied individuals with OSA. Genioglossus reflex responses measured via intramuscular electrodes to ∼60 brief (250 ms) pulses of negative upper-airway pressure (∼-15 cmH2 O at the mask) were compared between 13 participants (2 females) with tetraplegia plus OSA and 9 able-bodied controls (2 females) matched for age and OSA severity. The initial short-latency excitatory reflex response was absent in 6/13 people with tetraplegia and 1/9 controls. Genioglossus reflex inhibition in the absence of excitation was observed in three people with tetraplegia and none of the controls. When the excitatory response was present, it was significantly delayed in the tetraplegia group compared to able-bodied controls: excitation onset latency (mean ± SD) was 32 ± 16 vs. 18 ± 9 ms, P = 0.045; peak excitation latency was 48 ± 17 vs. 33 ± 8 ms, P = 0.038. However, when present, amplitude of the excitation response was not different between groups, 195 ± 26 vs. 219 ± 98% at baseline, P = 0.55. There are major differences in genioglossus reflex morphology and timing in response to rapid changes in airway pressure in people with tetraplegia and OSA. Altered genioglossus function may contribute to the increased risk of OSA in people with tetraplegia. The precise mechanisms mediating these differences are unknown.

What is the central question of this study? The haemodynamic response to incremental increases in negative intrathoracic pressure (nITP) during spontaneous breathing and the mechanisms of cardiac impairment at these levels of nITP remain unclear. What is the main finding and its importance? nITP of -20 cmH2 O or greater reduces stroke volume in healthy, spontaneously breathing supine humans due to direct ventricular interaction and increased left ventricular afterload.

Negative intrathoracic pressure (nITP) generally augments venous return and left ventricular (LV) stroke volume (LVSV), though large increases in nITP, commonly seen in respiratory disease, attenuate LVSV. Despite this consistent finding, the degree of nITP required to reduce LVSV and the contributions of series and direct ventricular interaction (DVI) in mediating this response remain unclear. We hypothesized that nITP ≤-15 cmH2 O would augment LVSV, while nITP ≥-20 cmH2 O would reduce LVSV via DVI and increased afterload. Twenty-three healthy subjects were randomly given inspiratory loads during spontaneous breathing to generate -5, -10, -15, -20 and -25 cmH2 O. LV volumes, LV geometry, inferior vena cava collapsibility (cIVC) and LV end-systolic meridional wall-stress (LVESMWS) were assessed in the supine position using tri-plane echocardiography. LVSV remained unchanged up to -15 cmH2 O, but was significantly reduced at nITP ≥-20 cmH2 O (-12 ± 8% and -15 ± 11% at -20 and -25 cmH2 O, respectively, P < 0.05) due to significant reductions in LV end-diastolic volume (LVEDV), while LV end-systolic volume was unchanged. cIVC on inspiration was significantly increased at all levels of nITP, while LVESMWS only increased at -25 cmH2 O (P < 0.05). DVI, as indicated by a significant increase in the radius of septal curvature, occurred at nITP ≥-10 cmH2 O. In supine healthy humans, nITP ≤-15 cmH2 O does not significantly affect LV function, despite increased DVI. In contrast, nITP ≥-20 cmH2 O causes significant reductions in LVSV and LVEDV, which appear to be mediated by DVI and increased afterload at -25 cmH2 O. The impact of cIVC during nITP remains unclear.

Mutations in the human cardiac troponin T gene (TNNT2) are associated with familial hypertrophic cardiomyopathy (FHC) linked to chromosome 1q3 (CMH2). Mutation analyses of TNNT2 have been restricted to RNA-based screening methods because only the TNNT2 cDNA sequence was known. We characterized the genomic structure of 15 TNNT2 exons spliced into the adult isoform. A protocol for rapid mutation detection based on direct sequencing of large PCR-amplified genomic DNA fragments revealed a known TNNT2 mutation (Phe110Ile) in one of 30 FHC probands. Three polymorphic short tandem repeat elements (D1S477, D1S2622, and D1S1723), useful for FHC pedigree analyses at CMH2, were shown to be physically tightly linked to TNNT2.

OBJECTIVE

Recognising changes in lung compliance can help clinicians to adjust initial inflations during resuscitation at birth. We examined whether physicians sensed low and normal compliance with a self-inflating bag before and after an educational intervention that used a manikin connected to a newborn lung simulator.

METHODS

We asked 43 physicians with neonatal duties to perform two low compliance ventilation attempts and two normal-compliance ventilation attempts in a randomised order at baseline and after the educational intervention, with 34 taking part in a retest three months later.

RESULTS

The physicians correctly recognised low and normal compliance in 71% and 66% of the ventilations at baseline, 80% and 66% of the ventilations after the intervention and 74% and 81% at retest. Correct recognition of normal compliance improved from baseline to retest (p = 0.04). Ventilations in low- vs normal-compliance settings resulted in lower tidal volumes (4.4 vs 23.0 mL, p < 0.001), lower ventilation rates (42 vs 51, p < 0.001) and higher peak inflating pressure (35.2 vs 31.4 cmH2 O, p < 0.001).

CONCLUSIONS

Around one in four physicians failed to recognise correct compliance levels when using a self-inflating bag and showed limited improvement after an educational intervention. Ventilations in a low-compliance setting resulted in suboptimal ventilation.

OBJECTIVE

To investigate the long-term course of the detrusor pressure during sacral anterior root stimulation in spinal cord injury (SCI) patients.

METHODS

Retrospective evaluation of 111 patients who had undergone sacral deafferentation and implantation of an anterior root stimulator at a single SCI rehabilitation center with a minimum follow-up time of 5 years.

RESULTS

The median follow-up time was 11.7 years (range 5.0-24.9 years). The maximum detrusor pressure (Pdet_max) during stimulation was higher in men compared to women (P = 0.0004) and decreased over time (P = 0.0006). However, there were no significant (P ≥ 0.06) differences in the median Pdet_max during stimulation between the first measurement time point and any follow-up time point. The Pdet_max during stimulation decreased from 62 cmH2 O (95%CI 57-73 cmH2 O) to 53 cmH2 O (95%CI 47-69 cmH2 O) (P = 0.9). The time had also a significant effect on Pdet_max during the storage phase (P < 0.0001) and bladder compliance (P = 0.0007). The Pdet_max during the storage phase decreased, whereas bladder compliance increased during the follow-up period. There were no significant (P ≥ 0.1) changes over time in bladder capacity, the number of daily stimulations and the residual urine volume after voiding.

CONCLUSIONS

The detrusor pressure during sacral anterior root stimulation decreases over time in SCI individuals. However, the changes do not seem to be clinically relevant during the first decade after surgery.

OBJECTIVE

To generate real-time radio-telemetric urodynamic reference data of maximum detrusor pressure (Pdet max ), maximum flow rate (Qmax) and estimated grade of infravesical obstruction, as well as duration of detrusor contraction (DOC), in female Göttingen minipigs and to describe translational aspects of the use of Göttingen minipigs for urological research.

METHODS

A telemetric transmitter was implanted into five female Göttingen minipigs, and 24 h measurements in metabolic cages were taken. Through operator-based analysis, synchronized real-time radio-telemetric cystometric data with flowmetric data and video sequences were used to determine voiding detrusor contractions (VCs) and non-voiding detrusor contractions (NVCs). Furthermore, data from telemetric natural-filling cystometry from free-moving and restricted maintenance conditions were compared for potential differences.

RESULTS

The median (range) Pdet max of VCs was 120.6 (21.0-370.0) cmH2 O and, therefore, significantly different from that of NVCs (64.60 [20.4-280.6 cmH2 O] cm H2 O). Intraindividual comparison of minipig data revealed great differences in voiding contractions. The effects of limited movement on VCs were analysed and showed significantly higher Pdet max and lower DOC than in free-moving conditions.

CONCLUSIONS

The presented data can be used for the development of telecystometric implanted minipig models, to investigate changes of detrusor function such as under- or overactivity, and might serve as model for bladder changes occurring with iatrogenic bladder outlet obstruction (BOO) or different therapeutic options for overactive bladder. Radio-telemetric real-time natural filling and voiding cystometries are feasible, reproducible in non-anaesthetized minipigs with free or limited movement and can give new insights into circadian behaviour and physiological and pathological bladder function.

Mechanical ventilation (MV) is routinely used in pediatric general anesthesia and critical care, but may adversely affect the cardiocirculatory system. Biomarkers are increasingly measured to assess cardiovascular status and improve clinical treatment decision-making. As the impact of mechanical ventilation strategies on cardiovascular biomarkers in ventilated infants is largely unknown, we conducted this retrospective study in a healthy in vivo infant rat ventilation model using 14-days old Wistar rats. We hypothesized that 2 h of mechanical ventilation with high and low positive end-expiratory pressure (PEEP), hyperoxemia, hypoxemia, hypercapnia, and hypocapnia would significantly impact B-type natriuretic peptide (BNP), vascular endothelial growth factor (VEGF), and endothelin-1 (ET-1). We found BNP to be driven by both high (9 cmH2 O) and low (1 cmH2 O) PEEP compared to ventilated control animals (P < 0.05). VEGF concentrations were associated with high PEEP, hyperoxemia, hypoxemia, and hypocapnia (P < 0.05), whereas ET-1 levels were changed only in response to hypoxemia (P < 0.05). In conclusion, the mode of mechanical ventilation alters plasma biomarker concentrations. Moreover, BNP and VEGF might serve as surrogate parameters for ventilation induced cardiovascular compromise and lung tissue damage. Furthermore, our data support the hypothesis, that sudden onset of hyperoxemia may trigger a quick VEGF release as a possible cellular survival reflex.

What's known on the subject? and what does the study add?: The AMS 800 urinary control system is the gold standard for the treatment of urinary incontinence due to sphincter insufficiency. Despite excellent functional outcome and latest technological improvements, the revision rate remains significant. To overcome the shortcomings of the current device, we developed a modern electromechanical artificial urinary sphincter. The results demonstrated that this new sphincter is effective and well tolerated up to 3 months. This preliminary study represents a first step in the clinical application of novel technologies and an alternative compression mechanism to the urethra.

OBJECTIVE

To evaluate the effectiveness in continence achievement of a new electromechanical artificial urinary sphincter (emAUS) in an animal model. To assess urethral response and animal general response to short-term and mid-term activation of the emAUS.

METHODS

The principle of the emAUS is electromechanical induction of alternating compression of successive segments of the urethra by a series of cuffs activated by artificial muscles. Between February 2009 and May 2010 the emAUS was implanted in 17 sheep divided into three groups. The first phase aimed to measure bladder leak point pressure during the activation of the device. The second and third phases aimed to assess tissue response to the presence of the device after 2-9 weeks and after 3 months respectively. Histopathological and immunohistochemistry evaluation of the urethra was performed.

RESULTS

Bladder leak point pressure was measured at levels between 1091 ± 30.6 cmH2 O and 1244.1 ± 99 cmH2 O (mean ± standard deviation) depending on the number of cuffs used. At gross examination, the explanted urethra showed no sign of infection, atrophy or stricture. On microscopic examination no significant difference in structure was found between urethral structure surrounded by a cuff and control urethra. In the peripheral tissues, the implanted material elicited a chronic foreign body reaction. Apart from one case, specimens did not show significant presence of lymphocytes, polymorphonuclear leucocytes, necrosis or cell degeneration. Immunohistochemistry confirmed the absence of macrophages in the samples.

CONCLUSIONS

This animal study shows that the emAUS can provide continence. This new electronic controlled sequential alternating compression mechanism can avoid damage to urethral vascularity, at least up to 3 months after implantation. After this positive proof of concept, long-term studies are needed before clinical application could be considered.

BACKGROUND

A spirometry device equipped with mainstream CO2 flow sensor is not available for large animal anaesthesia.

OBJECTIVE

To measure the resistance of a new large animal spirometry device and assess its agreement with reference methods for volume measurements.

METHODS

In vitro experiment and crossover study using anaesthetised horses.

METHODS

A flow partitioning device (FPD) equipped with 4 human CO2 flow sensors was tested. Pressure differences were measured across the whole FPD and across each sensor separately using air flows (range: 90-720 l/min). One sensor was connected to a spirometry monitor for in vitro volume (3, 5 and 7 l) measurements. These measurements were compared with a reference method. Five anaesthetised horses were used for tidal volume (VT) measurements using the FPD and a horse-lite sensor (reference method). Bland-Altman analysis, ANOVA and linear regression analysis were used for data analysis.

RESULTS

Pressure differences across each sensor were similar suggesting equal flow partitioning. The resistance of the device increased with flow (range: 0.3-1.5 cmH2 O s/l) and was higher than that of the horse-lite. The limits of agreement for volume measurements were within -1 and 2% in vitro and -12 and 0% in vivo. Nine of 147 VT measurements in horses were outside of the ± 10% limits of acceptance but most of these erroneous measurements occurred with VTs lower than 4 l. The determined correction factor for volume measurements was 3.97 ± 0.03.

CONCLUSIONS

The limits of agreement for volume measurements by the new device were within ± 10% using clinically relevant range of volumes. The new spirometry device can be recommended for measurement of VT in adult Warmblood horses.

OBJECTIVE

It is believed, that sustained lung inflation (SLI) at birth in preterm infants reduces the need for mechanical ventilation (MV) and improves respiratory outcomes. The aim of this study was to compare need for MV in preterm infants at high risk for respiratory distress syndrome (RDS) after prophylactic SLI via short binasal prongs at birth combined with early nasal continuous positive airway pressure (nCPAP) versus nCPAP alone.

METHODS

Medical records of infants born at 260/7 to 296/7 weeks gestation through 2015 and 2017 were retrospectively assessed. Infants who get sustained inflations at 25 cmH2 O pressure for 15 s following delivery via binasal short prongs comprised the study group. Gestational age matched infants who was supported solely with nCPAP (6 cmH2 O PEEP) comprised the control group. Early rescue surfactant (200 mg/kg poractant alfa) was delivered using the less invasive surfactant administration technique in infants with established RDS.

RESULTS

A total of 215 infants were analyzed. Fewer infants in the SLI group required MV within the first 72 h of life compared to the control group (25.7% vs 56.9%, P < 0.001). In multiple logistic regression analysis, SLI emerged as an independent factor for reduced MV need. Bronchopulmonary dysplasia (BPD) incidence including mild BPD was significantly lower in the SLI group (31.9% vs 48%, P = 0.01); however, moderate and severe BPD rates did not reach to a statistical significance (11.5% vs 20.6%, P = 0.06).

CONCLUSIONS

Prophylactic SLI maneuver at birth for preterm infants with impending RDS reduces the need for MV with no adverse effects.

OBJECTIVE

This study aims to identify the predictors for detrusor overactivity (DO) in women following extensive vaginal pelvic reconstructive surgery (PRS) for advanced pelvic organ prolapse (POP).

METHODS

We enrolled 1503 women who had prolapse POP-Q stage ≥ 3 and underwent vaginal PRS with or without MUS from January 2006 to December 2015. All subjects completed a 72-h voiding diary, IIQ-7, UDI-6, POPDI-6, and PISQ-12. Urodynamics (UDS) was performed pre- and post-operatively.

RESULTS

Among 1503 women, 56 patients were excluded due to incomplete data. Women who had trans-vaginal mesh were 1083 of 1447 (74.8%) and concomitant MUS were 353 (24.4%). Pre-operative DO were 245 (16.9%) and 24.5% (60/245) of them continued to have persistent DO post-operatively. Women who had normal pre-operative stable detrusor were 1202 (83.1%) and 3.5% (30/1202) developed de novo DO post-operatively. The overall incidence of post-operative DO was 6.2% (90/1447). Patients with age ≥66 year, neurological factors like Cerebrovascular accident and Parkinsonian disease, pre-operative bladder outlet obstruction (BOO) maximum urethral closure pressure (MUCP) ≥60 cmH2 O, Maximum flow rate (MFR) <15 mL/s and detrusor at maximum flow (Dmax) ≥20 cmH2 O) and post-void residue (PVR) ≥200 mL hold a significant higher risk of developing DO either persistent or de novo following PRS.

CONCLUSIONS

Age ≥66 year, neurological factors like CVA and Parkinsonian disease, pre-operative MUCP ≥60 cmH2 O, MFR < 15 mL, Dmax ≥ 20 cmH2 O, and PVR ≥ 200 mL are independent risk factors for developing post-operative DO following vaginal PRS for advanced POP.

OBJECTIVE

To assess the respiratory muscle time constant of relaxation (τ), an index of respiratory muscle function in ventilated newborns.

METHODS

Sixty-two infants (42 born prematurely) with a median gestational age of 29 [interquartile range (IQR) 26-37] weeks were prospectively studied. Measurement of τ was taken during spontaneous breathing on endotracheal continuous positive airway pressure prior to extubation, and τ was calculated from the reciprocal of the slope of the airway pressure decline versus time. Infants were classified as having had systemic or respiratory infection (positive microbiology) if they had any positive bacterial blood or respiratory culture prior to measurement.

RESULTS

Measurement of τ was taken at a median post-natal age of 6 (IQR 3-29) days. The median τ was higher in premature infants [17.4 (IQR 7.7-28.3) sec/cmH2 O] compared to term infants [6.8 (IQR 4.4-8.7) sec/cmH2 O, p < 0.001]. The median τ was higher in infants who had had positive microbiology [17.6 (IQR 9.9-29.1) sec/cmH2 O] compared to infants with negative microbiology [8.0 (IQR 6.3-17.9) sec/cmH2 O, p = 0.034]. τ was related to gestational age (r = -0.265, p = 0.003) and weight at measurement (r = -0.269, p = 0.002).

CONCLUSIONS

Respiratory muscle function in ventilated newborns is negatively affected by prematurity and previous systemic or respiratory infection.

To evaluate if urinary continence in patients with refractory neurogenic detrusor overactivity (NDO) incontinence after intradetrusor onabotulinumtoxinA injections is sufficient for appropriate outcome assessment or if urodynamic investigation (UDI) is needed.

A consecutive series of 148 patients undergoing intradetrusor onabotulinumtoxinA injections for refractory NDO incontinence were prospectively evaluated. Patients underwent UDI before and at 6 weeks after onabotulinumtoxinA injections. The primary outcome was the prevalence of maximum storage detrusor pressure (Pdetmax storage) of >40 cmH2 O in continent patients at 6 weeks after treatment. The secondary outcomes were treatment effects on other clinical and video-urodynamic variables.

At 6 weeks after intradetrusor onabotulinumtoxinA injections, 98 of the 148 patients (66%) with NDO incontinence were continent. Of these patients, 18 (18%, confidence interval 12-27%) had a Pdetmax storage of >40 cmH2 O. Gender, underlying neurological disorder, and high Pdetmax storage before treatment appear to increase the risk of poor urodynamic outcomes.

Urinary continence is not sufficient for outcome assessment after intradetrusor onabotulinumtoxinA injections, as high intravesical pressures threatening the upper urinary tract may be missed in a relevant proportion of continent patients. Therefore, we strongly recommend UDI as a routine part of the follow-up.

Spontaneous cerebrospinal fluid (CSF) leaks have imaging findings consistent with chronically elevated intracranial pressure, such as empty sella. Meckel's cave is a CSF-filled space that houses the trigeminal ganglion at the cranial base. Our objective in this study was to evaluate "dilated" Meckel's cave as a radiologic sign in patients with elevated intracranial pressure spontaneous CSF leaks and compare the dimensions with those from a control cohort.

Meckel's cave dimensions were measured in patients with spontaneous CSF leaks and documented elevated intracranial pressure. A control group of subjects who underwent magnetic resonance imagine (MRI) scans for unrelated diagnoses were also evaluated. Subjects were included only if suitable MRIs with T2-weighted sequences in the axial plane were available.

Sixty-three patients with spontaneous CSF leaks and 91 normal control patients were included in the study. There was significant (p < 0.05) enlargement in all measured dimensions (length and width) for the spontaneous CSF leak group. When evaluating area, spontaneous CSF leak subjects again showed significant enlargement compared with controls (0.81 ± 0.35 cm2 vs 0.52 ± 0.15 cm2 ; p < 0.0001). Average intracranial pressure measurements were 25.9 ± 9.0 cmH2 O.

Patients with spontaneous CSF leaks have evidence of enlarged Meckel's caves. Evaluation of Meckel's cave dimensions should be included in preoperative imaging assessment as an additional indicator of chronically elevated intracranial pressure.

What is the central question of this study? This study is the first to measure objectively both inspiratory and expiratory muscle fatigue after inspiratory resistive loading to determine whether the expiratory muscles are activated to the point of fatigue when specifically loading the inspiratory muscles. What is the main finding and its importance? The absence of abdominal muscle fatigue suggests that future studies attempting to understand the neural and circulatory consequences of diaphragm fatigue can use inspiratory resistive loading without considering the confounding effects of abdominal muscle fatigue. Expiratory resistive loading elicits inspiratory as well as expiratory muscle fatigue, suggesting parallel coactivation of the inspiratory muscles during expiration. It is unknown whether the expiratory muscles are likewise coactivated to the point of fatigue during inspiratory resistive loading (IRL). The purpose of this study was to determine whether IRL elicits expiratory as well as inspiratory muscle fatigue. Healthy male subjects (n = 9) underwent isocapnic IRL (60% maximal inspiratory pressure, 15 breaths min-1 , 0.7 inspiratory duty cycle) to task failure. Abdominal and diaphragm contractile function was assessed at baseline and at 3, 15 and 30 min post-IRL by measuring gastric twitch pressure (Pga,tw ) and transdiaphragmatic twitch pressure (Pdi,tw ) in response to potentiated magnetic stimulation of the thoracic and phrenic nerves, respectively. Fatigue was defined as a significant reduction from baseline in Pga,tw or Pdi,tw . Throughout IRL, there was a time-dependent increase in cardiac frequency and mean arterial blood pressure, suggesting activation of the respiratory muscle metaboreflex. The Pdi,tw was significantly lower than baseline (34.3 ± 9.6 cmH2 O) at 3 (23.2 ± 5.7 cmH2 O, P < 0.001), 15 (24.2 ± 5.1 cmH2 O, P < 0.001) and 30 min post-IRL (26.3 ± 6.0 cmH2 O, P < 0.001). The Pga,tw was not significantly different from baseline (37.6 ± 17.1 cmH2 O) at 3 (36.5 ± 14.6 cmH2 O), 15 (33.7 ± 12.4 cmH2 O) and 30 min post-IRL (32.9 ± 11.3 cmH2 O). Inspiratory resistive loading elicits objective evidence of diaphragm, but not abdominal, muscle fatigue. Agonist-antagonist interactions for the respiratory muscles appear to be more important during expiratory versus inspiratory loading.

BACKGROUND

The optimal combination of inflation pressures and times to produce adequate expiratory tidal volumes during initial resuscitation in prematurely born infants has not been determined. The aim of this study was therefore to assess combinations of inflation pressures and times and the resulting expiratory tidal volume levels using a respiratory function monitor.

METHODS

Sixty-four infants born before 34 weeks of gestation were studied. The infants were divided according to whether the inflation pressure (peak inflation pressure minus positive end expiratory pressure) was < or ≥20 cmH2 O during the first five inflations delivered by a face mask, and those groups were then subdivided according to whether the inflation time was < or ≥1.5 s.

RESULTS

Inflation pressure ≥20 cmH2 O compared with lower pressure at both inflation times produced significantly higher expiratory tidal volume. Longer compared with shorter inflation times when the inflation pressure was ≥20 cmH2 O resulted in no significant difference in expiratory tidal volume. At <20 cmH2 O inflation pressure, longer inflation time overall resulted in higher end tidal volume, but the majority of infants had a tidal volume less than the anatomical dead space.

CONCLUSIONS

At higher inflation pressure, a longer inflation time was not necessary to increase expiratory tidal volume.

Continuous airflow in the upper airway can cause discomfort, leading to nasopharyngeal complaints. The aim of the present study is to evaluate the acute effects of continuous positive upper-airway pressure on nasal patency in awake normal subjects.

Twenty-seven adults (17 men; 10 women; age range, 18 to 43 years) were exposed to continuous airway pressure (20 cmH2 O) in the nasal cavity, delivered by a continuous positive airway pressure (CPAP) device through a nasal mask for 2 hours. Visual analogue scale (VAS) of nasal obstruction, Nasal Obstruction Symptom Evaluation (NOSE) modified scale, acoustic rhinometry (AR), and peak nasal inspiratory flow (PF) were measured before and after the use of CPAP.

There was an increase in nasal obstruction scores both on the VAS (p < 0.05) and on the NOSE scale (p < 0.05), as well as a reduction in nasal cavity volume on AR (p < 0.05) and a decline in PF (p < 0.05). Subjects were stratified into 2 groups: with and without symptoms of allergic rhinitis. Nasal parameters were significantly worse in the rhinitis group, with higher nasal obstruction scores on the VAS (p = 0.001) and NOSE scale (p < 0.001) and decreased PF (p < 0.001).

Acute exposure to positive pressure via CPAP is associated with subjective and objective reductions in nasal patency. In individuals with allergic nasal symptoms, deterioration is even more severe than in patients without these symptoms.

Nasal high frequency oscillatory ventilation (nHFOV) is a promising mode of non-invasive neonatal respiratory support. To combine the effects of nasal continuous positive airway pressure (nCPAP) and high frequency oscillatory ventilation, an oscillatory pressure waveform is superposed to a nCPAP via a nasal or nasopharyngeal interface. nHFOV has been described to facilitate carbon dioxide (CO2 ) elimination compared to nCPAP. The influence of unintended leakage on CO2 elimination has not been investigated in nHFOV before. We explored the effects of oral leakage on CO2 elimination during nHFOV in a physical model of the neonatal respiratory system.

A neonatal ventilator was connected to an airway- and lung model using binasal prongs as interface. The model comprised a continuous CO2 influx. Alveolar CO2 partial pressure was continuously measured. Gas flow rates and pressures were measured simultaneously at the prongs, pharynx, lung, and at the leakage. Effects of combined nasopharyngeal leakage (0, 5, or 10 L/min) on CO2 elimination, gas flow rate and pressure were determined at various ventilation frequencies (6, 8, 10, and 12 Hz) and amplitudes (10%, 20%, and 30% of maximum ventilator performance) at a mean airway pressure of 10 cmH2 O.

nHFOV with moderate leakage was more effective in CO2 elimination than without leakage (P < 0.001) for all tested amplitudes and frequencies. Maximum leakage resulted in highly variable, partly ineffective CO2 elimination.

A moderate oral leakage rather improves than impairs gas exchange during non-invasive ventilatory support with nHFOV. Pediatr Pulmonol. 2017;52:367-372. © 2016 Wiley Periodicals, Inc.

BACKGROUND

With the development of newer polyurethane cuffed endotracheal tubes (cETTs), there has been a shift in clinical practice among pediatric anesthesiologists. Despite improvements in design, excessive inflation of the cuff can still compromise tracheal mucosal perfusion. Several perioperative factors can affect the intracuff pressure (CP), and there is no consensus on safe CP in pediatric patients undergoing repair of congenital cardiac disease (CHD) utilizing cardiopulmonary bypass (CPB). In the current study, the CP was continuously monitored in pediatric patients undergoing surgery for CHD.

METHODS

After IRB approval, this observational study was conducted on pediatric patients who underwent repair of CHD using CPB with a cETT in place. After anesthetic induction and endotracheal intubation, the cuff was inflated using the air leak technique while maintaining a continuous positive airway pressure of 20 cmH2 O. After inflation, the CP was continuously monitored throughout the procedure. In addition, temperature and mean arterial pressure (MAP) were also recorded.

RESULTS

The study included 33 patients who ranged in age from 1 month to 15.3 years. Their weight ranged from 4.0 to 83.6 kg. Six patients were excluded from the analysis due to the need to add or remove air from the cuff, leaving 27 patients for data analysis for cuff pressure over time. The baseline CP at the time of inflation was 16.1 ± 7.6 cmH2 O. With the use of CPB and initiation of hypothermia, when compared to the baseline, the CP decreased by -0.7 ± 5.8 cmH2 O at 35-37°C, -9.1 ± 8.4 cmH2 O at 31-33°C, -7.8 ± 6.2 cmH2 O at 27-29°C, and -11.1 ± 6.0 cmH2 O at <27°C. With rewarming, the CP increased back to the baseline level (-3.5 ± 7.0 cmH2 O).

CONCLUSIONS

There was a significant decrease in the CP during CPB and associated hypothermia. This may offer some protection for mucosal perfusion during CPB which is usually associated with lower than normal MAP. However, the decrease in the CP may compromise the tracheal seal which may not offer the intended protection for the airway from aspiration.

This randomized controlled trial study aimed to identify the optimal positive pressure (PP) level that can clear atelectasis while avoiding pulmonary hyperinflation during the breath-hold technique in dogs undergoing thoracic computed tomography (CT). Sixty dogs affected by mammary tumors undergoing thoracic CT for the screening of pulmonary metastases were randomly assigned to six groups with different levels of PP during the breath-hold technique: 0 (control), 5 (PP5), 8 (PP8), 10 (PP10), 12 (PP12), and 15 (PP15) cmH2 O. The percentage of atelectatic lung region was lower in the PP10 (3.7 ± 1.1%; P = 0.002), PP12 (3.4 ± 1.3%; P = 0.0001), and PP15 (2.8 ± 0.9%; P = 0.006) groups than in the control group (5.0 ± 2.3%), and the percentage of poorly aerated lung region was lower in the PP8 (15.1 ± 2.6%; P = 0.0009), PP10 (13.0 ± 2.0 %; P = 0.002), PP12 (13.0 ± 2.2 %; P = 0.0002), and PP15 (11.1 ± 1.9%; P = 0.0002) groups than in the control group (19.8 ± 5.0). The percentage of normally aerated lung region, however, was higher in the PP10 (79.7 ± 4.1%; P = 0.005), PP12 (79.8 ± 5.1%; P = 0.0002), and PP15 (80.2 ± 4.9%; P = 0.002) groups than in the control group (73.4 ± 6.6%). A PP of 10-12 cmH2 O during the breath-hold technique should be considered to improve lung aeration during a breath-hold technique in dogs undergoing thoracic CT.

Cuffed tracheal tubes are increasingly used in paediatric anaesthetic practice. This study compared tidal volume and leakage around cuffed and uncuffed tracheal tubes in children who required standardised mechanical ventilation of their lungs in the operating theatre. Children (0-16 years) undergoing elective surgery requiring tracheal intubation were randomly assigned to receive either a cuffed or an uncuffed tracheal tube. Assessments were made at five different time-points: during volume-controlled ventilation 6 ml.kg-1 , PEEP 5 cmH2 O and during pressure-controlled ventilation 10 cmH2 O / PEEP 5 cmH2 O. The pressure-controlled ventilation measurement time-points were: just before a standardised recruitment manoeuvre; just after recruitment manoeuvre; 10 min; and 30 min after the recruitment manoeuvre. Problems and complications were recorded. During volume-controlled ventilation, leakage was significantly less with cuffed tracheal tubes than with uncuffed tracheal tubes; in ml.kg-1 , median (IQR [range]) 0.20 (0.13-0.39 [0.04-0.60]) vs. 0.82 (0.58-1.38 [0.24-4.85]), respectively, p < 0.001. With pressure-controlled ventilation, leakage was less with cuffed tracheal tubes and stayed unchanged over a 30-min period, whereas with uncuffed tracheal tubes, leakage was higher and increased further over the 30-min period. Tidal volumes were higher in the cuffed group and increased over time, but in the uncuffed group were lower and decreased over time. Both groups showed an increase in tidal volumes following recruitment manoeuvres. There were more short-term complications with uncuffed tracheal tubes, but no major complications were recorded in either group at long-term follow-up. With standardised ventilator settings, cuffed tracheal tubes produced better ventilation characteristics compared with uncuffed tracheal tubes during general anaesthesia for routine elective surgery.

BACKGROUND

The aim of this prospective study was to investigate the success of ultrasound in pediatric patients in determining the appropriate sized cuffed endotracheal tube and to compare the results with conventional height-based (Broselow) tape and age-based formula tube size.

METHODS

One hundred and fifty-two children of 1-10 years of age, who received general anesthesia for adenotonsillectomy were enrolled to the study. In all participants, the transverse diameter of the subglottis was measured with ultrasound during apnea. An endotracheal tube was chosen with the outer diameter matched to the measured subglottic airway diameter. An age-based (Motoyama-Khine) and height-based (Broselow) endotracheal tube size was calculated. If there was resistance to passage of the tube into the trachea or an airway pressure >25 cmH2 0 was required to detect an audible leak, the endotracheal tube was replaced with internal diameter of 0.5 mm smaller. If there was an audible leak at airway pressure <10 cmH2 O, or peak pressure >25 cmH2 0 or a cuff pressure>> 25 cmH2 O was required to seal, the tube was changed to the 0.5 mm larger internal diameter. Best-fit tube internal diameter was the resultant tube internal diameter that met the previously stated conditions. The need for endotracheal tube replacement and peak airway pressure were recorded.

RESULTS

The internal diameter of ultrasound determined tube was the same as best-fit tube in 88% of children. Endotracheal tube was replaced in 15 patients with a one size larger, and in three patients with one size smaller tube. Using Bland-Altman analysis, a better agreement was observed with ultrasound measurement rather than height-based estimation and age-based formulas.

CONCLUSIONS

Our findings show that subglottic diameter measured by ultrasound appears to be a reliable predictor for the assessment of the subglottic diameter of the airway in estimating appropriate size pediatric endotracheal tube.