Oxygen Saturation Curve Analysis in 2298 Hypoxia Awareness Training Tests of Military Aircrew Members in a Hypobaric Chamber.

We aim to provide reference values for military aircrews participating in hypoxia awareness training (HAT). We describe several parameters with potential biomedical interest based on selected segments and slopes of the changes in oxygen saturation (SatO2) during a standard HAT. A retrospective analysis of 2298 records of the SatO2 curve was performed, including 1526 military men aged 30.48 ± 6.47 years during HAT in a hypobaric chamber. HAT consisted of pre-oxygenation at 100% and an ascent to 7620 m, followed by O2 disconnection starting the phase of descent of SatO2 until reaching the time of useful consciousness (TUC), and finally reconnection to 100% O2 in the recovery phase. Using an ad hoc computational procedure, the time taken to reach several defined critical values was computed. These key parameters were the time until desaturation of 97% and 90% (hypoxia) after oxygen mask disconnection (D97/D90) and reconnection (R97/R90) phases, the time of desaturation (TUC-D97) and hypoxia (TUC-D90) during disconnection, the total time in desaturation (L97) or hypoxia (L90), and the slopes of SatO2 drop (SDSAT97 and SDSAT90) and recovery (SRSAT97). The mean of the quartiles according to TUC were compared by ANOVA. The correlations between the different parameters were studied using Pearson's test and the effect size was estimated with ω2. Potentially useful parameters for the HAT study were those with statistical significance (p < 0.05) and a large effect size. D97, D90, R97, and R90 showed significant differences with small effect sizes, while TUC-D97, TUC-D90, L97, L90, and SDSAT97 showed significant differences and large effect sizes. SDSAT97 correlated with TUC (R = 0.79), TUC-D97 (R = 0.81), and TUC-D90 (R = 0.81). In conclusion, several parameters of the SatO2 curve are useful for the study and monitoring of HAT. The SDSAT97 measured during the test can estimate the TUC and thus contribute to taking measures to characterize and protect the aircrew members.

An Igor Pro 8.01 Procedure to Analyze Pulse Oximetry during Acute Hypoxia Test in Aircrews.

The recognition of hypoxia symptoms is a critical part of physiological training in military aviation. Acute exposure protocols have been designed in hypobaric chambers to train aircrews to recognize hypoxia and quickly take corrective actions. The goal of the acute hypoxia test is to know the time of useful consciousness and the minimal arterial oxygen saturation tolerated. Currently, there is no computer system specifically designed to analyze the physiological variables obtained during the test. This paper reports the development and analytical capabilities of a computational tool specially designed for these purposes. The procedure was designed using the Igor Pro 8.01 language, which processes oxygen saturation and heart rate signals. To accomplish this, three functional boards are displayed. The first allows the loading and processing of the data. The second generates graphs that allow for a rapid visual examination to determine the validity of individual records and calculate slopes on selected segments of the recorded signal. Finally, the third can apply filters to generate data groups for analysis. In addition, this tool makes it possible to propose new study variables that are derived from the raw signals and can be applied simultaneously to large data sets. The program can generate graphs accompanied by basic statistical parameters and heat maps that facilitate data visualization. Moreover, there is a possibility of adding other signals during the test, such as the oxygenation level in vital organs, electrocardiogram, or electroencephalogram, which illustrates the test's excellent potential for application in aerospace medicine and for helping us develop a better understanding of complex physiological phenomena.

Predicting irreparable renal ischemic injury using a real-time marker in the porcine model.

PURPOSE: We determined the maximal renal tolerance of warm ischemia using renal cortical interstitial metabolic changes to identify a potential real-time marker of irreparable renal function. MATERIALS AND METHODS: Using a single kidney model 3 groups of 5 pigs each underwent 120, 150 and 180 minutes of warm ischemia, respectively. Microdialysis samples were collected before, during and after ischemia. Renal function assessments consisting of serum creatinine and GFR measurements were performed before ischemia and on post-ischemia days 1, 5, 9, 14 and 28. Kidneys exposed and not exposed to ischemia were collected for histological study. RESULTS: Interstitial glucose and pyruvate concentrations decreased, while lactate concentrations increased to stable levels during ischemia. Glutamate spiked at 30 minutes of ischemia and subsequently tapered, while glycerol increased throughout warm ischemia time. At post-ischemia day 28 renal function returned to pre-ischemia baseline levels in the group with 120 minutes of ischemia but did not recover to baseline in the 150 and 180-minute ischemic groups. Functional data correlated with histological findings. The 120-minute maximal renal tolerance of warm ischemia correlated with a mean +/- SD glycerol concentration of 167 +/- 24 micromol/l. CONCLUSIONS: Interstitial glycerol is a real-time, renal unit specific, minimally invasive marker of renal function deterioration. Exposure of porcine kidneys to ischemic insults resulting in renal cortical interstitial glycerol concentrations higher than 167 micromol/l is associated with irreparable functional damage in this model.

Real-time analysis of renal interstitial metabolites during induced renal ischemia*.

PURPOSE: Microdialysis is an innovative technique used to monitor the chemistry of the interstitial fluid in living tissue. We documented changes in concentration of interstitial fluid metabolites before, during, and after induced renal ischemia. MATERIALS AND METHODS: Under general anesthesia, a microdialysis probe was laparoscopically positioned into the renal cortex of six pigs. Isotonic sterile perfusion fluid was pumped through the probe at 2 microL/min. After collecting a baseline sample, the renal artery was occluded with a Satinsky clamp for 90 (n = 3) or 120 (n = 3) minutes. A dialysate sample was collected every 30 minutes during the ischemic and 3-hour postischemic period. The samples were analyzed for glucose, lactate, pyruvate, glutamate, urea, and glycerol concentrations with the CMA/600 Microdialysis Analyzer. Serum metabolic panels from peripheral venous samples drawn before ischemia, after ischemia, and 3 hours after ischemia were analyzed. RESULTS: Glucose and pyruvate concentrations significantly declined (P = 0.01, P = 0.05, respectively) while lactate and glycerol concentrations significantly increased during ischemia (P = <0.01, P < 0.01, respectively). Glutamate increased to 2.5 times the baseline concentration (P < 0.01) at 1 hour of ischemia and subsequently declined during ischemia. The lactate/pyruvate ratio increased sharply during ischemia and returned to baseline within 1 hour postischemia. There were no changes noted in serum creatinine levels before and after ischemia. CONCLUSIONS: Microdialysis can accurately measure minute real-time changes in the renal interstitial environment caused by ischemia not detected with serum studies. These local changes may be correlated with ischemic times to predict tissue preservation in future studies.

The effects of ureteral mobilization and transection on ureteral oxygenation.

OBJECTIVES: To determine the impact of ureteral transection with and without prior ureteral mobilization on ureteral oxygen partial pressure (p(u)O(2)). METHODS: Sixteen pigs underwent general anesthesia with laparoscopic transperitoneal access to the right ureter. With no dissection and minimal manipulation, a tissue oxygen probe (Licox, Kiel, Germany) was introduced via a trocar and inserted into the ureter. The probes were placed at the ureteropelvic junction (UPJ, n = 8) and ureterovesical junction (UVJ, n = 8). Baseline p(u)O(2) was measured. Subsequently, half of the animals at each level (n = 4) underwent complete ureteral transection proximal to UPJ probes and distal to UVJ probes with or without prior mobilization. p(u)O(2) levels were measured after ureteral mobilization and transection. RESULTS: Of the ureters transected at the UPJ without mobilization, the mean p(u)O(2) level declined by 13 mm Hg relative to baseline (P = 0.07). The baseline UPJ p(u)O(2) level declined by 5 mm Hg after ureteral mobilization alone and subsequently by 31 mm Hg after transection (P <0.01). Of the ureters transected at the UVJ without mobilization, the p(u)O(2) level decreased by 4 mm Hg relative to baseline (P = 0.08). The baseline UVJ p(u)O(2) level decreased by 15 mm Hg after ureteral mobilization alone and subsequently by 39 mm Hg after transection (P <0.01). At both the UPJ and UVJ, the transected-only p(u)O(2) level was statistically higher than the mobilized and transected level (P = 0.03, respectively). CONCLUSIONS: During ureteral surgery, mobilization alone exposes the distal ureter to more ischemia than the proximal ureter, and efforts to minimize ureteral mobilization when transection is necessary are crucial in maintaining tissue oxygenation.

Lapra-Ty holding strength and slippage with various suture types and sizes.

OBJECTIVES: To investigate the holding strength and slippage of Lapra-Ty clips on various suture types and sizes. METHODS: Using an automated materials testing system with the Lapra-Ty in a fixed position, Lapra-Ty holding strength and displacement were determined with 0, 2-0, 3-0, and 4-0 Vicryl, Monocryl, and polydioxanone suture (PDS). To simulate clinical application, Lapra-Tys were also tested by applying a load to these sutures after being passed through a full-thickness layer of tautly suspended fresh porcine bladder tissue. Three trials were performed with each suture type and size. RESULTS: The Lapra-Ty holding strength with Vicryl suture was significantly higher than with Monocryl or PDS of the same suture size in bladder tissue trials. Monocryl suture had a significantly higher displacement than Vicryl or PDS of the same suture size in bladder tissue trials (except for 4-0 Monocryl and PDS having insignificantly different displacements). Lapra-Tys slipped off Vicryl, Monocryl, and PDS in 25%, 67%, and 67% of their respective trials. Lapra-Tys did not slip during any of the trials with 2-0 suture of any type or 3-0 Vicryl. Lapra-Tys with holding strengths on suture less than approximately 8 Newtons (N) slipped and greater than 8 N pulled through the bladder tissue without slipping. CONCLUSIONS: The optimal suture type and size to maximize Lapra-Ty holding strength and minimize slippage was determined to be 2-0 and 3-0 Vicryl, 2-0 Monocryl, and 2-0 PDS. Monocryl suture stretches more than Vicryl and PDS at higher loads.

Shock wave lithotripsy success for renal stones based on patient and stone computed tomography characteristics.

OBJECTIVES: To determine the patient and noncontrast computed tomography (NCCT) stone characteristics that predict either of 2 extracorporeal shock wave lithotripsy (ESWL) outcomes: stone-free (SF) status or ESWL success. METHODS: The records of 200 consecutive patients with nephrolithiasis treated with ESWL were reviewed. Patient age, sex, stone laterality, body surface area, body mass index, maximal stone dimension, mean stone Hounsfield units (HU), stone Hounsfield density, skin-to-stone distance (SSD), and intrarenal stone location were studied as potential predictors. Patients with no calcifications on postoperative kidneys, ureters, and bladder (KUB) at 6 weeks were defined as SF. ESWL success was defined as SF or remaining stone fragments less than 4 mm. RESULTS: Intrarenal stone location was found to be the only predictor of SF status. Renal pelvic/ureteropelvic junction (UPJ) stones cleared better than calyceal stones, and upper/middle calyceal stones cleared better than lower calyceal stones. Stone size, mean HU, and location predicted ESWL fragmentation success. Smaller stones and stones with lower mean HU levels were more successfully fragmented. Higher SF and ESWL success rates were found with a shorter SSD among calyceal stones when renal pelvic/UPJ stones were excluded from analysis. CONCLUSIONS: Stone location is the most important factor in achieving SF status after ESWL. NCCT stone characteristics such as stone size, mean HU, and intrarenal location are important predictors of ESWL success.

Feasibility of laparoscopic renal cooling with near-freezing saline irrigation delivered with a standard irrigator aspirator.

OBJECTIVES: To determine the feasibility of laparoscopic renal cooling with near-freezing saline irrigation in the porcine model delivered using readily available operating room equipment. METHODS: Five pigs underwent laparoscopic renal surgery with temperature sensors placed in the medulla and upper, middle, and lower pole renal cortex. After complete occlusion of the renal artery and vein, near-freezing saline was delivered with a standard irrigator/aspirator onto the renal surface. The run-off was simultaneously suctioned as it pooled in the hilum with a second aspirator. The kidney and body temperatures were monitored throughout the 1-hour ischemic period and for 10 minutes after unclamping the hilum. RESULTS: Continuous irrigation of the kidney with near-freezing saline in the first pig resulted in hypothermic renal (13.8 degrees C) and core body (33.1 degrees C) temperatures. For the subsequent four pigs, irrigation was limited to the first 5 minutes of ischemia to achieve renal cortical and medullary temperatures of less than 20.0 degrees C within 6 and 8 minutes of ischemia, respectively. Subsequently, the kidney was irrigated for 1 minute every 12 to 14 minutes to maintain renal temperatures of less than 20.0 degrees C. The core body temperatures decreased from a mean baseline of 37.0 degrees to 35.4 degrees C using the intermittent irrigation technique. Our early clinical experience with near-freezing saline intermittent irrigation during laparoscopic partial nephrectomy with 10 patients showed stable core body temperature and serum creatinine with a mean ischemic time of 48 minutes. CONCLUSIONS: Using standard, readily available laparoscopic irrigator/aspirators, renal cooling during laparoscopic partial nephrectomy with near-freezing saline creates acceptable renal tissue temperatures for preservation of renal function.

Caracterización clínica de la vejiga inestable motora / Clinical characterization of dynamic unstable bladder

Clínicamente, la inestabilidad del detrusor se asocia con síntomas como frecuencia miccional, nicturia,urgencia y urgeincontinencia (Sd. de Urgencia).El propósito de nuestro trabajo es objetivar la sintomatología urinaria baja de pacientes con diagnósticourodinámico confirmado de vejiga inestable motora (VIM).A un total de 19 pacientes que consultaron en un período de 6 meses por síntomas sugerentes de síndromede urgencia y cuya urodinamia demostró la presencia de una vejiga inestable motora, se les solicitó quecompletaran un diario miccional durante dos días.El promedio de edad fue de 59 años, todos los pacientes cumplieron con, al menos, un criterio clínico deSd. de Urgencia. Los síntomas que más se asocian a VIM en nuestros pacientes son la urgencia miccionaly la disminución en la capacidad vesical.

Riesgo precoz de recidiva bioquímica en prostatectomizados radicales (T1c): aplicación de una ecuación predictiva validada / Precocious risk of biochemical recurrence in radical prostatectomy (Rp): application of a validated predictive equation

Muchos modelos predictivos de recidiva para cáncer de próstata (CaP) post prostatectomía radical (PR)son difíciles de aplicar y la tendencia es a encontrar modelos que consideren datos clínicos y patológicosde fácil y rápida obtención. El grupo de trabajo del Johns Hopkins Hospital desarrolló una ecuación deriesgo validada para identificar pacientes de alto riesgo de recidiva precoz de CaP (etapa clínica T1c),después de PR.Realizamos una revisión retrospectiva de pacientes sometidos a PR retropúbica por CaP etapa clínica T1,con un seguimiento mínimo de 6 meses. En estos pacientes aplicamos la ecuación Rw.De un total de 190 pacientes sometidos a PR en los últimos 7 años, encontramos 60 pacientes analizablesen etapa T1c. El promedio de seguimiento fue de 25,4 meses. Al aplicar la ecuación Rw encontramos unasensibilidad de 29 porciento, especificidad de 98 porciento, VPP de 83 porciento y VPN de 78 porciento. En nuestra serie la ecuación RWtiene una pobre sensibilidad pero una buena especificidad.