Search

BACKGROUND: Unexplained physiological events (PE), possibly related to hypoxia and hyperventilation, are a concern for some air forces. Physiological monitoring could aid research into PEs, with measurement of arterial oxygen saturation (Spo2) often suggested despite potential limitations in its use. Given similar physiological responses to hypoxia and hyperventilation, the present study characterized the cardiovascular and respiratory responses to each.METHODS: Ten healthy subjects were exposed to 55 mins of normobaric hypoxia simulating altitudes of 0, 8000, and 12,000 ft (0, 2438, and 3658 m) while breathing normally and voluntarily hyperventilating (doubling minute ventilation). Respiratory gas analysis and spirometry measured end-tidal gases (PETo2 and PETco2) and minute ventilation. Spo2 was assessed using finger pulse oximetry. Mean arterial, systolic, and diastolic blood pressure were measured noninvasively. Cognitive impairment was assessed using the Stroop test.RESULTS: Voluntary hyperventilation resulted in a doubling of minute ventilation and lowered PETco2, while altitude had no effect on these. PETo2 and Spo2 declined with increasing altitude. However, despite a significant drop in PETo2 of 15.2 mmHg from 8000 to 12,000 ft, Spo2 was similar when hyperventilating (94.7 ± 2.3% vs. 93.4 ± 4.3%, respectively). The only cardiovascular response was an increase in heart rate while hyperventilating. Altitude had no effect on cognitive impairment, but hyperventilation did.DISCUSSION: For many cardiovascular and respiratory variables, there is minimal difference in responses to hypoxia and hyperventilation, making these challenging to differentiate. Spo2 is not a reliable marker of environmental hypoxia in the presence of hyperventilation and should not be used as such without additional monitoring of minute ventilation and end-tidal gases.Haddon A, Kanhai J, Nako O, Smith TG, Hodkinson PD, Pollock RD. Cardiorespiratory responses to voluntary hyperventilation during normobaric hypoxia. Aerosp Med Hum Perform. 2023; 94(2):59–65.

INTRODUCTION: Recently developed wearable monitoring devices can provide arterial oxygen saturation (Spo2) measurements, offering potential for use in aerospace operations. Pilots and passengers are already using these technologies, but their performance has not yet been established under conditions experienced in the flight environment such as environmental hypoxia and concurrent body motion.METHODS: An initial evaluation was conducted in 10 healthy subjects who were studied in a normobaric chamber during normoxia and at a simulated altitude of 15,000 ft (4572 m; 11.8% oxygen). Spo2 was measured simultaneously using a standard pulse oximeter and four wearable devices: Apple Watch Series 6; Garmin Fēnix 6 watch; Cosinusso Two in-ear sensor; and Oxitone 1000M wrist-worn pulse oximeter. Measurements were made while stationary at rest, during very slight body motion (induced by very low intensity cycling at 30 W on an ergometer), and during moderate body motion (induced by moderate intensity cycling at 150 W).RESULTS: Missed readings, defined as failure to record an Spo2 value within 1 min, occurred commonly with all wearables. Even with only very slight body motion, most devices missed most readings (range of 12–82% missed readings) and the rate was higher with greater body motion (range 18–92%). One device tended to under-report Spo2, while the other devices tended to over-report Spo2. Performance decreased across the devices when oxygenation was reduced.DISCUSSION: In this preliminary evaluation, the wearable devices studied did not perform to the same standard as a traditional pulse oximeter. These limitations may restrict their utility in flight and require further investigation.Hearn EL, Byford J, Wolfe C, Agyei C, Hodkinson PD, Pollock RD, Smith TG. Measuring arterial oxygen saturation using wearable devices under varying conditions. Aerosp Med Hum Perform. 2023; 94(1):42–47.

BACKGROUND: High-G acceleration experienced during launch and re-entry of suborbital spaceflights may present challenges for older or medically susceptible participants. A detailed understanding of the associated physiological responses would support the development of an evidence-based medical approach to commercial suborbital spaceflight.METHODS: There were 24 healthy subjects recruited into ‘younger’ (18-44 yr), ‘intermediate’ (45-64 yr) and ‘older’ (65-80 yr) age groups. Cardiovascular and respiratory variables were measured continuously during dynamic combinations of +Gx (chest-to-back) and +Gz (head-to-foot) acceleration that simulated suborbital G profiles for spaceplane and rocket/capsule platforms. Measurements were conducted breathing air and breathing 15% oxygen to simulate a cabin pressure altitude of 8000 ft.RESULTS: Suborbital G profiles generated highly dynamic changes in heart rate, blood pressure, and cardiac output. G-induced hypoxemia was observed, with minimum arterial oxygen saturation < 80% in a quarter of subjects. Increased age was associated with greater hypoxemia and reduced cardiac output responses but did not have detrimental cardiovascular effects. ECG changes included recurrent G-induced trigeminy in one individual. Respiratory and visual symptoms were common, with 88% of subjects reporting greyout and 29% reporting blackout. There was one episode of G-induced loss of consciousness (G-LOC).DISCUSSION: Suborbital acceleration profiles are generally well tolerated but are not physiologically inconsequential. Marked hemodynamic effects and transient respiratory compromise could interact with predisposing factors to precipitate adverse cardiopulmonary effects in a minority of participants. Medically susceptible individuals may benefit from expanded preflight centrifuge familiarization that includes targeted physiological evaluation in the form of a ‘G challenge test’.Smith TG, Pollock RD, Britton JK, Green NDC, Hodkinson PD, Mitchell SJ, Stevenson AT. Physiological effects of centrifuge-simulated suborbital spaceflight. Aerosp Med Hum Perform. 2022; 93(12):830–839.

The accuracy and ease of metabolite assignments from a complex mixture are expected to be facilitated by employing a multispectral approach. The two-dimensional (2D)

ObjectivesTo identify predictors of early artificial sphincter (AUS) erosion among a cohort of men with erosion, who underwent AUS placement by either university or community-based surgeons.MethodsThe records of all patients with AUS erosions, including men who underwent AUS placement at outside facilities, were retrospectively reviewed. A Cox proportional-hazards model for time to erosion was performed with the predictors being the components of a fragile urethra (history of radiation, prior AUS, prior urethroplasty), androgen deprivation therapy (ADT), trans-corporal (TC), and 3.5 cm cuff, controlling for other risk factors. Kaplan-Meier survival curves and log-rank test compared "fragile" urethras with "not fragile" urethras. All statistical analysis was done using R version 3.5.2.ResultsOf the 156 men included, 36% had undergone AUS placement in the community. Median time to erosion was 16.0 months (1.0-240.0 months), and 122 (78%) met at least one fragility criteria. Radiation (HR 2.36, 95% CI 1.52-3.64) and prior urethroplasty (HR 2.12, 95% CI 1.18-3.80) were independently associated with earlier time to erosion. The Kaplan-Meier estimates demonstrate 1- and 5-year survival rates of 76.5% and 50.0%, respectively, for "non-fragile" and 44.1% and 14.8% for "fragile" urethras (P < .0001).ConclusionIn a diverse cohort of men with AUS erosion, men with "fragile" urethras eroded sooner. Radiation and prior urethroplasty were independent risk factors for earlier time to erosion, but prior AUS, ADT, TC and 3.5 cm cuff were not.

The Pseudomonas syringae DC3000 type III effector HopAM1 suppresses plant immunity and contains a Toll/interleukin-1 receptor (TIR) domain homologous to immunity-related TIR domains of plant nucleotide-binding leucine-rich repeat receptors that hydrolyze nicotinamide adenine dinucleotide (NAD+ ) and activate immunity. In vitro and in vivo assays were conducted to determine if HopAM1 hydrolyzes NAD+ and if the activity is essential for HopAM1's suppression of plant immunity and contribution to virulence. HPLC and LC-MS were utilized to analyze metabolites produced from NAD+ by HopAM1 in vitro and in both yeast and plants. Agrobacterium-mediated transient expression and in planta inoculation assays were performed to determine HopAM1's intrinsic enzymatic activity and virulence contribution. HopAM1 is catalytically active and hydrolyzes NAD+ to produce nicotinamide and a novel cADPR variant (v2-cADPR). Expression of HopAM1 triggers cell death in yeast and plants dependent on the putative catalytic residue glutamic acid 191 (E191) within the TIR domain. Furthermore, HopAM1's E191 residue is required to suppress both pattern-triggered immunity and effector-triggered immunity and promote P. syringae virulence. HopAM1 manipulates endogenous NAD+ to produce v2-cADPR and promote pathogenesis. This work suggests that HopAM1's TIR domain possesses different catalytic specificity than other TIR domain-containing NAD+ hydrolases and that pathogens exploit this activity to sabotage NAD+ metabolism for immune suppression and virulence.

Cyclic adenosine diphosphate (ADP)–ribose (cADPR) isomers are signaling molecules produced by bacterial and plant Toll/interleukin-1 receptor (TIR) domains via nicotinamide adenine dinucleotide (oxidized form) (NAD + ) hydrolysis. We show that v-cADPR (2′cADPR) and v2-cADPR (3′cADPR) isomers are cyclized by O-glycosidic bond formation between the ribose moieties in ADPR. Structures of 2′cADPR-producing TIR domains reveal conformational changes that lead to an active assembly that resembles those of Toll-like receptor adaptor TIR domains. Mutagenesis reveals a conserved tryptophan that is essential for cyclization. We show that 3′cADPR is an activator of ThsA effector proteins from the bacterial antiphage defense system termed Thoeris and a suppressor of plant immunity when produced by the effector HopAM1. Collectively, our results reveal the molecular basis of cADPR isomer production and establish 3′cADPR in bacteria as an antiviral and plant immunity–suppressing signaling molecule.

Objective To determine surgical site infection and urinary tract infection (UTI) rates in the setting of urethroplasty. Given significant variation in the utilization of antibiotics, there is an opportunity to improve antibiotic stewardship. This study aims to elucidate the rate of both UTI and surgical site infection after urethroplasty on a standardized perioperative antibiotic regimen, and to obtain patient and operative characteristics that may predict infection. Methods We prospectively treated 390 patients undergoing urethroplasty at 11 centers with a standardized perioperative antibiotic protocol. Patients had a urine culture or urine analysis within 3 weeks of surgery. After surgery, patients were discharged with an indwelling catheter, removed per usual surgeon practice. All were given nitrofurantoin from discharge until catheter removal. Logistic regression analyses were performed to determine the correlation between patient characteristics or operative categories with post-operative infection. Results The rates of postoperative UTI and wound infection within 30 days were 6.7% and 4.1%, respectively. On multivariate analysis of demographics, comorbidities, and stricture characteristics and repair, only preoperative UTI (P = .012), history of cardiovascular disease (P = .015), and performing a membranous urethroplasty (0.018) were significant predictors of a UTI within 30 days postoperatively. Location of repair nor graft use increased the risk of UTI. There were no factors predictive of postoperative wound infection. Conclusion A standardized antibiotic protocol was created to narrow and limit excess antibiotic use. This protocol, with clear definitions of UTI and wound infection, allowed determination of accurate infection rates in urethroplasties. Preoperative UTI, even when properly treated, increases the risk of postoperative UTI.

PurposeThere are no established guidelines regarding management of antibiotics for patients specifically undergoing urethral reconstruction. Our aim was to minimize antibiotic use by following a standardized protocol in the pre-, peri- and postoperative setting, and adhere to American Urological Association antibiotic guidelines. We hypothesized that prolonged suppressive antibiotics post-urethroplasty does not prevent urinary tract infection and/or wound infection rates.Materials and methodsWe prospectively treated 900 patients undergoing urethroplasty or perineal urethrostomy at 11 centers over 2 years. The first-year cohort A received prolonged postoperative antibiotics. Year 2, cohort B, did not receive prolonged antibiotics. A standardized protocol following the American Urological Association guidelines for perioperative antibiotics was used. The 30-day postoperative infectious complications were determined. We used chi-square analysis to compare the cohorts, and multivariate logistic regression to identify risk factors.ResultsThe mean age of participants in both cohorts was 49.7 years old and the average stricture length was 4.09 cm. Overall, the rate of postoperative urinary tract infection and wound infection within 30 days was 5.1% (6.7% in phase 1 vs 3.9% in phase 2, p=0.064) and 3.9% (4.1% in phase 1 vs 3.7% in phase 2, p=0.772), respectively. Multivariate logistic regression analysis of patient characteristics and operative factors did not reveal any factors predictive of postoperative infections.ConclusionsThe use of a standardized protocol minimized antibiotic use and demonstrated no benefit to prolonged antibiotic use. There were no identifiable risk factors when considering surgical characteristics. Given the concern of antibiotic over-prescription, we do not recommend prolonged antibiotic use after urethral reconstruction.

PurposeA successful urethroplasty has been defined in different ways across studies. This variety in the literature makes it difficult to compare success rates and techniques across studies. We aim to evaluate the success of anterior urethroplasty based on different definitions of success in a single cohort.Materials and methodsData were collected from a multi-institutional, prospectively maintained database. We included men undergoing first-time, single-stage, anterior urethroplasty between 2006 and 2020. Exclusion criteria included lack of followup, hypospadias, extended meatotomy, perineal urethrostomy, posterior urethroplasty and staged repairs. We compared 5 different ways to define a "failed" urethroplasty: 1) stricture retreatment, 2) anatomical recurrence on cystoscopy, 3) peak flow rate

Cyclic ADP ribose (cADPR) isomers are important signaling molecules produced by bacterial and plant Toll/interleukin-1 receptor (TIR) domains via NAD+ hydrolysis, yet their chemical structures are unknown. We show that v-cADPR (2’cADPR) and v2-cADPR (3’cADPR) isomers are cyclized by O-glycosidic bond formation between the ribose moieties in ADPR. Structures of v-cADPR (2’cADPR)-producing TIR domains reveal that conformational changes are required for the formation of the active assembly that resembles those of Toll-like receptor adaptor TIR domains, and mutagenesis data demonstrate that a conserved tryptophan is essential for cyclization. We show that v2-cADPR (3’cADPR) is a potent activator of ThsA effector proteins from Thoeris anti-phage defence systems and is responsible for suppression of plant immunity by the effector HopAM1. Collectively, our results define new enzymatic activities of TIR domains, reveal the molecular basis of cADPR isomer production, and establish v2-cADPR (3’cADPR) as an antiviral signaling molecule and an effector-mediated signaling molecule for plant immunity suppression.One-Sentence SummaryThe chemical structures of two O-glycosidic bond-containing cyclic ADP ribose isomers, the molecular basis of their production, and their function in antiviral and plant immunity suppression by bacteria are reported.

OBJECTIVE To demonstrate our hypothesis that the presence of extravasation on postoperative urethrogram is inconsequential for disease recurrence in urethroplasty postoperative follow-up. MATERIALS AND METHODS We utilized the Trauma and Urologic Reconstructive Network of Surgeons database to assess 1691 patients who underwent urethroplasty and post-operative urethrogram. Anatomic and functional recurrence were defined as RESULTS Among 1101 patients with cystoscopy follow-up, 54 (4.9%) had extravasation on initial postoperative urethrogram. Among those 54, 74.1% developed an anatomic recurrence vs 13% without extravasation (P CONCLUSION Postoperative urethrogram has a high specificity but low sensitivity for anatomic and functional recurrence during short term follow-up. The positive predictive value of urinary extravasation is high: patients with extravasation incur a high risk of anatomic recurrence within 1 year and such patients may warrant increased monitoring.