Exclusive breastfeeding among women with type 1 and type 2 diabetes mellitus.

OBJECTIVE: To compare exclusive breastfeeding (BF) and BF initiation among 185 women with Type 1 and 212 women with Type 2 pregestational diabetes who intended exclusive or partial BF and delivered at ≥34 weeks of gestation. METHODS: Retrospective cohort study. At discharge, exclusive BF is direct BF or BF complemented with expressed breast milk. BF initiation is defined by exclusive or partial BF. RESULTS: Type 1 and Type 2 groups were similar in prior BF experience (69 vs 67%) but were different in intention to BF exclusively (92 vs 78%) and partially (8 vs 22%). Women in the Type 1 group were younger (median age 30 vs 33y), likely to be primiparous (47 vs 25%), have a lower median BMI (32 vs 36 kg/m2) and deliver by primary cesarean (37 vs 26%). Infants born to Type 1 women were more likely to be admitted to the NICU (44 vs 18%) and to have hypoglycemia (59 vs 41%). At discharge, exclusive BF among Type 1 was higher (34 vs 23%), partial BF was similar (47 vs 46%) while FF (formula feeding) was lower (19 vs 31%) than in the Type 2 group. BF initiation occurred in 81% of Type 1 and 69% of Type 2 women. CONCLUSION: Intention to BF exclusively was higher in Type 1 women compared to Type 2. At discharge, exclusive BF and BF initiation were lower and FF higher in the Type 2 group highlighting the need for different strategies if lactation in this special population is to be improved.

New Chest Drainage Unit with Integrated CO2-Detector Demonstrates False Air Leak.

BACKGROUND: Postoperative observed air leakage does not always originate from parenchymal defects but may arise from defects in the chest drainage unit, connections or reverse airflow in water seals. We investigated such false air leakage using a new chest drainage unit with a built-in CO2-detector and an electronic chest drainage unit. METHODS: Two types of chest drainage units were tested in a simple porcine model: A well-known electronic chest drainage unit and a new chest drainage unit with integrated CO2-detector. We created a setup of true air leakage-a parenchymal lesion, and false air leakage-allowing air to flow into the thoracic cavity alongside the chest drain. RESULTS: We demonstrated that the new chest drainage unit with a built-in CO2-detector can distinguish between experimentally induced true air leakage and false air leakage. CONCLUSION: Available chest drainage systems do not allow direct assessment of true or false air leakage, which may increase chest drain duration unnecessarily. The integration of a CO2-sensitive color indicator into a chest drainage unit allows simple distinction between false air leak and true air leak, which may improve postoperative management.

Neonatal Anthropometric Measures and Peripherally Inserted Central Catheter Depth.

BACKGROUND: Peripherally inserted central catheters (PICCs) are used routinely in neonatal care. Measures of surface anatomy have been used to estimate appropriate PICC depth in neonates since 1973. However, prior PICC research using anthropometric measures to estimate proper PICC insertion depth has been limited to pediatric and adult literature. PURPOSE: The purpose of this study was to explore the relationships among a neonate's anthropometric measures and the appropriate PICC insertion depth. METHODS: Neonates requiring PICC insertion at Nationwide Children's Hospital were enrolled between January and September 2018. Standard PICC procedures were followed. The research group corroborated appropriate PICC tip position of enrolled infants. Multivariable linear regression with robust standard errors was used to evaluate linear relationships between PICC insertion depth and current weight, current length, and PICC insertion site. RESULTS: Demographics of enrolled infants included gestational ages of 23 to 39 weeks, weights of 510 to 3870 g, and lengths of 31 to 54 cm. Of the 56 infants considered, final statistical analysis included 49 neonates (14 ankle, 16 knee, and 19 antecubital insertions). Current neonatal weight was associated with PICC depth at all sites (all Ps < .0001). Current neonatal length was associated with PICC depth at all sites (all Ps < .0001). Preprocedure surface measurement was also strongly associated with PICC insertion depth (P < .0001). IMPLICATIONS FOR PRACTICE: This investigation demonstrated a relationship for both neonatal weight and length that may be an anthropometric model for neonatal PICC insertion depth. IMPLICATIONS FOR RESEARCH: A more robust sample size could more precisely define the anthropometric model.

Unchanged cerebrovascular CO2 reactivity and hypercapnic ventilatory response during strict head-down tilt bed rest in a mild hypercapnic environment.

KEY POINTS: Carbon dioxide levels are mildly elevated on the International Space Station and it is unknown whether this chronic exposure causes physiological changes to astronauts. We combined ∼4 mmHg ambient PCO2 with the strict head-down tilt bed rest model of spaceflight and this led to the development of optic disc oedema in one-half of the subjects. We demonstrate no change in arterialized PCO2 , cerebrovascular reactivity to CO2 or the hypercapnic ventilatory response. Our data suggest that the mild hypercapnic environment does not contribute to the development of spaceflight associated neuro-ocular syndrome. ABSTRACT: Chronically elevated carbon dioxide (CO2 ) levels can occur in confined spaces such as the International Space Station. Using the spaceflight analogue 30 days of strict 6° head-down tilt bed rest (HDTBR) in a mild hypercapnic environment ( PCO2 = ∼4 mmHg), we investigated arterialized PCO2 , cerebrovascular reactivity and the hypercapnic ventilatory response in 11 healthy subjects (five females) before, on days 1, 9, 15 and 30 of bed rest (BR), and 6 and 13 days after HDTBR. During all HDTBR time points, arterialized PCO2 was not significantly different from the pre-HDTBR measured in the 6° HDT posture, with a mean (95% confidence interval) increase of 1.2 mmHg (-0.2 to 2.5 mmHg, P = 0.122) on day 30 of HDTBR. Respiratory acidosis was never detected, although a mild metabolic alkalosis developed on day 30 of HDTBR by a mean (95% confidence interval) pH change of 0.032 (0.022-0.043; P < 0.001), which remained elevated by 0.021 (0.011-0.031; P < 0.001) 6 days after HDTBR. Arterialized pH returned to pre-HDTBR levels 13 days after BR with a change of -0.001 (-0.009 to 0.007; P = 0.991). Compared to pre-HDTBR, cerebrovascular reactivity during and after HDTBR did not change. Baseline ventilation, ventilatory recruitment threshold and the slope of the ventilatory response were similar between pre-HDTBR and all other time points. Taken together, these data suggest that the mildly increased ambient PCO2 combined with 30 days of strict 6° HDTBR did not change arterialized PCO2 levels. Therefore, the experimental conditions were not sufficient to elicit a detectable physiological response.

Impact of Prolonged Spaceflight on Orthostatic Tolerance During Ambulation and Blood Pressure Profiles in Astronauts.

BACKGROUND: Astronauts returning to earth usually demonstrate reduced orthostatic tolerance when assessed on a tilt table or quiet standing, but no studies have evaluated postflight orthostatic tolerance during activities of daily living, when it is most clinically relevant. Ambulatory blood pressure (BP) variability also is associated with orthostatic intolerance in certain patient populations and can capture clinically significant orthostatic hypotension during activities of daily living, especially when measured on a beat-to-beat basis. We evaluated the impact of prolonged spaceflight on orthostatic tolerance and BP profiles in astronauts. METHODS: Ambulatory beat-to-beat BP was recorded using a portable device for multiple 24-hour time periods before, during, and after 6 months of spaceflight in 12 astronauts (4 women; age 48±5 [mean±SD] years). BP variability in the time domain was calculated as the SD. Systolic BP distribution during activities of daily living was characterized by skewness and kurtosis. RESULTS: In contrast with results from previous studies that used tilt tables or stand tests, no astronaut experienced orthostatic intolerance/hypotension during activities of daily living before or after spaceflight. Also, 24-hour systolic BP decreased in space (120±10 mm Hg before spaceflight versus 106±9 mm Hg during spaceflight; P<0.01), but it returned to normal upon landing (122±13 mm Hg). Diastolic BP was unchanged during and after spaceflight. Systolic and diastolic BP variability remained the same before, during, and after spaceflight (both P>0.05). The skewness of systolic BP increased in space (0.74±0.51 versus 1.43±1.00; P=0.001), indicating that signal fluctuations became asymmetrical; however, it returned to preflight levels after landing (0.51±0.42). The kurtosis increased in space (5.01±7.67 versus 11.10±11.79; P=0.010), suggesting that fluctuations concentrated around the mean with a narrow distribution; however, it also returned to preflight levels (2.21±2.56) after return to earth. CONCLUSIONS: Given current countermeasures including in-flight exercise training and volume resuscitation on return, no astronauts experienced orthostatic hypotension or intolerance during routine (for landing day) activities in the initial 24 hours after landing following 6 months in space. Prolonged exposure to spaceflight had little impact on systolic BP variability and its distribution, although the latter showed a transient change in space (accompanied by mild relative hypotension), all of which returned to preflight values after return to earth.

Intracranial Effects of Microgravity: A Prospective Longitudinal MRI Study.

Background Astronauts on long-duration spaceflight missions may develop changes in ocular structure and function, which can persist for years after the return to normal gravity. Chronic exposure to elevated intracranial pressure during spaceflight is hypothesized to be a contributing factor, however, the etiologic causes remain unknown. Purpose To investigate the intracranial effects of microgravity by measuring combined changes in intracranial volumetric parameters, pituitary morphologic structure, and aqueductal cerebrospinal fluid (CSF) hydrodynamics relative to spaceflight and to establish a comprehensive model of recovery after return to Earth. Materials and Methods This prospective longitudinal MRI study enrolled astronauts with planned long-duration spaceflight. Measures were conducted before spaceflight followed by 1, 30, 90, 180, and 360 days after landing. Intracranial volumetry and aqueductal CSF hydrodynamics (CSF peak-to-peak velocity amplitude and aqueductal stroke volume) were quantified for each phase. Qualitative and quantitative changes in pre- to postflight (day 1) pituitary morphologic structure were determined. Statistical analysis included separate mixed-effects models per dependent variable with repeated observations over time. Results Eleven astronauts (mean age, 45 years ± 5 [standard deviation]; 10 men) showed increased mean volumes in the brain (28 mL; P < .001), white matter (26 mL; P < .001), mean lateral ventricles (2.2 mL; P < .001), and mean summated brain and CSF (33 mL; P < .001) at postflight day 1 with corresponding increases in mean aqueductal stroke volume (14.6 µL; P = .045) and mean CSF peak-to-peak velocity magnitude (2.2 cm/sec; P = .01). Summated mean brain and CSF volumes remained increased at 360 days after spaceflight (28 mL; P < .001). Qualitatively, six of 11 (55%) astronauts developed or showed exacerbated pituitary dome depression compared with baseline. Average midline pituitary height decreased from 5.9 to 5.3 mm (P < .001). Conclusion Long-duration spaceflight was associated with increased pituitary deformation, augmented aqueductal cerebrospinal fluid (CSF) hydrodynamics, and expansion of summated brain and CSF volumes. Summated brain and CSF volumetric expansion persisted up to 1 year into recovery, suggesting permanent alteration. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Lev in this issue.

Neonatal Histamine-2 Receptor Antagonist and Proton Pump Inhibitor Treatment at United States Children's Hospitals.

OBJECTIVE: To determine treatment frequency and duration of histamine-2 receptor antagonist (H2RA)/proton pump inhibitor (PPI) use among infants hospitalized within US children's hospital neonatal intensive care units and evaluate diagnoses/demographic factors associated with use. STUDY DESIGN: We retrospectively analyzed a cohort of neonatal intensive care unit infants admitted to 43 US children's hospitals within the Pediatric Health Information System database between January 2006 and March 2013 to determine H2RA/PPI treatment frequency, timing/duration of treatment, factors associated with use, percent of infants remaining on treatment at discharge, and interhospital prescribing variation. We used a modified Poisson regression to calculate the adjusted probability of infants ever receiving H2RAs/PPIs in relation to diagnosis, gestation, and sex. RESULTS: Of the 122 002 infants evaluated, 23.8% (n = 28 989) ever received an H2RA or PPI; 19.0% received H2RAs (n = 23 187), and 10.5% (n = 12 823) received PPIs. Extremely preterm infants and term infants were the most likely to receive H2RA and PPI treatment. Infants with gastroesophageal reflux disease (relative risk [RR] = 3.13) and congenital heart disease (RR = 2.41) had the highest H2RA/PPI treatment probabilities followed by those with an ear, nose, and throat diagnosis (RR = 2.34; P < .05). The majority of treated infants remained treated at discharge. CONCLUSIONS: Despite limited evidence and increasing safety concerns, H2RAs/PPIs are frequently prescribed to extremely preterm neonates and those with congenital anomalies and continued through discharge. Our findings support the need for innovative studies to examine the comparative effectiveness and safety of H2RA/PPIs vs no treatment in these high-risk neonatal populations.

Hypovolemic men and women regulate blood pressure differently following exposure to artificial gravity.

PURPOSE: In addition to serious bone, vestibular, and muscle deterioration, space flight leads to cardiovascular dysfunction upon return to gravity. In seeking a countermeasure to space flight-induced orthostatic intolerance, we previously determined that exposure to artificial gravity (AG) training in a centrifuge improved orthostatic tolerance of ambulatory subjects. This protocol was more effective in men than women and more effective when subjects exercised. METHODS: We now determine the orthostatic tolerance limit (OTL) of cardiovascularly deconditioned (furosemide) men and women on one day following 90 min of AG compared to a control day (90 min of head-down bed rest, HDBR). RESULTS: There were three major findings: a short bout of artificial gravity improved orthostatic tolerance of hypovolemic men (30 %) and women (22 %). Men and women demonstrated different mechanisms of cardiovascular regulation on AG and HDBR days; women maintained systolic blood pressure the same after HDBR and AG exposure while men's systolic pressure dropped (11 ± 2.9 mmHg) after AG. Third, as presyncopal symptoms developed, men's and women's cardiac output and stroke volume dropped to the same level on both days, even though the OTL test lasted significantly longer on the AG day, indicating cardiac filling as a likely variable to trigger presyncope. CONCLUSIONS: (1) Even with gender differences, AG should be considered as a space flight countermeasure to be applied to astronauts before reentry into gravity, (2) men and women regulate blood pressure during an orthostatic stress differently following exposure to artificial gravity and (3) the trigger for presyncope may be cardiac filling.

Gradient compression garments protect against orthostatic intolerance during recovery from bed rest.

INTRODUCTION: Abdomen-high, lower body graded compression garments (GCGs) may represent the next-generation of orthostatic intolerance protection with applications for exploration missions and commercial space flight. PURPOSE: To evaluate the efficacy of the GCG to prevent orthostatic intolerance after a 14-day 6° head-down tilt bed rest (BR) and to determine whether wearing thigh-high compression garments impairs recovery from BR. METHODS: Sixteen (12 M, 4 F) subjects participated in a 15-min 80° head-up tilt test 5 day before BR (BR-5), on the last morning of BR (BR+0), and on day 1 (BR+1) and 3 after BR (BR+3). No subjects wore the GCG on BR-5, and all subjects wore the GCG during testing on BR+0. Control subjects (n = 8) wore the GCG only through testing on BR+0. Treatment subjects (n = 8) wore the GCG on BR+0 and thigh-high garments on BR+1 and BR+2. RESULTS: No subjects were presyncopal during tilt on BR+0 while wearing the GCG. Despite lower plasma volume index (BR-5: 1.52 ± 0.06, BR+0: 1.32 ± 0.05 l/m(2)), the tilt-induced increase in heart rate (ΔHR, 17 ± 2 bpm) and decrease in stroke volume (ΔSV, -28 ± 3 ml) on BR+0 were less than on BR-5 (24 ± 2 bpm, -43 ± 4 ml). On BR+1 ΔHR in the control group (33 ± 4 bpm) was higher than in the treatment group (23 ± 2 bpm) but there were no group differences on BR+3. CONCLUSIONS: Wearing the GCG prevented the orthostatic intolerance that is normally present after BR. Thigh-high garments provided protection after BR, and wearing these garments did not impair recovery.

Simulations of gravitational stress on normovolemic and hypovolemic men and women.

BACKGROUND: Earth-based simulations of physiologic responses to space mission activities are needed to develop prospective countermeasures. To determine whether upright lower body positive pressure (LBPP) provides a suitable space mission simulation, we investigated the cardiovascular responses of normovolemic and hypovolemic men and women to supine and orthostatic stress induced by head-up tilt (HUT) and upright LBPP, representing standing in lunar, Martian, and Earth gravities. METHODS: Six men and six women were tested in normovolemic and hypovolemic (furosemide, intravenous, 0.5 mg x kg(-1)) conditions. Continuous electrocardiogram, blood pressure, segmental bioimpedance, and stroke volume (echocardiography) were recorded supine and at lunar, Martian, and Earth gravities (10 degrees, 20 degrees, and 80 degrees HUT vs. 20%, 40%, and 100% bodyweight upright LBPP), respectively. Cardiovascular responses were assessed from mean values, spectral powers, and spontaneous baroreflex parameters. RESULTS: Hypovolemia reduced plasma volume by approximately 10% and stroke volume by approximately 25% at supine, and increasing orthostatic stress resulted in further reductions. Upright LBPP induced more plasma volume losses at simulated lunar and Martian gravities compared with HUT, while both techniques induced comparable central hypovolemia at each stress. Cardiovascular responses to orthostatic stress were comparable between HUT and upright LBPP in both normovolemic and hypovolemic conditions; however, hypovolemic blood pressure was greater during standing at 100% bodyweight compared to 80 degree HUT due to a greater increase of total peripheral resistance. CONCLUSIONS: The comparable cardiovascular response to HUT and upright LBPP support the use of upright LBPP as a potential model to simulate activity in lunar and Martian gravities.

Cardiovascular models of simulated moon and mars gravities: head-up tilt vs. lower body unweighting.

INTRODUCTION: In this study we compare two models [head-up tilt (HUT) vs. body unweighting using lower body positive pressure (LBPP)] to simulate Moon, Mars, and Earth gravities. A literature search did not reveal any comparisons of this type performed previously. We hypothesized that segmental fluid volume shifts (thorax, abdomen, upper and lower leg), cardiac output, and blood pressure (BP), heart rate (HR), and total peripheral resistance to standing would be similar in the LBPP and HUT models. METHODS: There were 21 subjects who were studied while supine (simulation of spaceflight) and standing at 100% (Earth), 40% (Mars), and 20% (Moon) bodyweight produced by LBPP in Alter-G and while supine and tilted at 80 degrees, 20 degrees, and 10 degrees HUT (analogues of Earth, Mars, and Moon gravities, respectively). RESULTS: Compared to supine, fluid shifts from the chest to the abdomen, increases in HR, and decreases in stroke volume were greater at 100% bodyweight than at reduced weights in response to both LBPP and HUT. Differences between the two models were found for systolic BP, diastolic BP, mean arterial BP, stroke volume, total peripheral resistance, and thorax and abdomen impedances, while HR, cardiac output, and upper and lower leg impedances were similar. CONCLUSIONS: Bodyweight unloading via both LBPP and HUT resulted in cardiovascular changes similar to those anticipated in actual reduced gravity environments. The LBPP model/Alter-G has the advantage of providing an environment that allows dynamic activity at reduced bodyweight; however, the significant increase in blood pressures in the Alter-GC may favor the HUT model.

Sex differences in blood pressure control during 6° head-down tilt bed rest.

Spaceflight-induced orthostatic intolerance has been studied for decades. Although ∼22% of the astronaut corps are women, most mechanistic studies use mostly male subjects, despite known sex differences in autonomic control and postflight orthostatic intolerance. We studied adrenergic, baroreflex, and autonomic indexes during continuous infusions of vasoactive drugs in men and women during a 60-day head-down bed rest. Volunteers were tested before bed rest (20 men and 10 women) and around day 30 (20 men and 10 women) and day 60 (16 men and 8 women) of bed rest. Three increasing doses of phenylephrine (PE) and sodium nitroprusside were infused for 10 min after an infusion of normal saline. A 20-min rest period separated the phenylephrine and sodium nitroprusside infusions. Autonomic activity was approximated by spectral indexes of heart rate and blood pressure variability, and baroreflex sensitivity was measured by the spontaneous baroreflex slope. Parasympathetic modulation and baroreflex sensitivity decreased with bed rest, with women experiencing a larger decrease in baroreflex sensitivity by day 30 than men. The sympathetic activation of men and parasympathetic responsiveness of women in blood pressure control during physiological stress were preserved throughout bed rest. During PE infusions, women experienced saturation of the R-R interval at high frequency, whereas men did not, revealing a sex difference in the parabolic relationship between high-frequency R-R interval, a measurement of respiratory sinus arrhythmia, and R-R interval. These sex differences in blood pressure control during simulated microgravity reveal the need to study sex differences in long-duration spaceflight to ensure the health and safety of the entire astronaut corps.

High thoracic epidural analgesia as an adjunct to general anesthesia is associated with better outcome in low-to-moderate risk cardiac surgery patients.

OBJECTIVE: The purpose of this study was to evaluate the addition of high thoracic epidural analgesia (HTEA) to general anesthesia in cardiac surgery patients to enhance the fast-track and improvement in outcome. DESIGN: Retrospective cohort study of prospectively registered data using population-based healthcare databases. PARTICIPANTS: One thousand seven hundred thirteen consecutive patients scheduled for elective coronary artery bypass grafting, aortic valve replacement, mitral valve surgery, and combinations eligible for supplementation with epidural analgesia. One thousand sixteen patients were matched and analyzed. SETTING: University hospital, single center. INTERVENTION: To minimize bias and confounding, epidural patients were matched using EuroSCORE criteria to nonepidural in a 1:1 ratio requiring exact match on sex, age, patient factors, cardiac factors, and procedure type together with normal/moderate/poor left ventricular function, insulin-dependent diabetes, and on-pump/off-pump surgery. All together, 1,016 patients (508 each group) were identified with matching criteria. MEASUREMENTS AND MAIN RESULTS: Outcome parameters were 30-day and 6-month mortality, postoperative dialysis, stroke, and myocardial infarction. Univariate analysis showed that epidural analgesia was associated with lower 6-month mortality (p = 0.021), lower frequency of postoperative dialysis (p = 0.029), and lower frequency of myocardial infarction (p = 0.049). No difference was seen in stroke (p = 0.341). However, adjusted odds ratio of selected perioperative variables showed that HTEA only had a positive impact on the frequency of postoperative dialysis (0.22 [0.06-0.74]). CONCLUSION: This large, uniquely matched single-center cohort was generated, and, subject to the listed limitations the authors concluded that supplemental HTEA to general anesthesia had a better outcome in low-risk cardiac surgery patients, with a significantly lower 6-month mortality rate compared with the control group. However, regression analysis revealed that HTEA only had an independently positive effect on the frequency of postoperative dialysis.

Abdomen-high elastic gradient compression garments during post-spaceflight stand tests.

UNLABELLED: Space Shuttle astronauts wore an inflatable antigravity suit during reentry and landing, and astronauts and cosmonauts wear an elastic-compression garment (with lacing) during Soyuz re-entry and landings and in the first few days of recovery. However, neither garment is an ideal countermeasure to spaceflight-induced orthostatic intolerance. Our laboratory has been investigating an elastic graded compression garment (GCG) that applies graduated pressures from the feet to the abdomen for use following International Space Station missions and possibly during exploration missions. METHODS: Before and after Shuttle missions, 14 astronauts participated in a 3.5-min stand test. The stand test was conducted without garments preflight. On landing day, 7 astronauts wore the GCG while 7 astronauts did not (controls). Heart rate and blood pressure were measured in all astronauts during prone rest and standing. Stroke volume and cardiac output were measured only in GCG subjects. RESULTS: No astronauts in either group became presyncopal during the stand test preflight or postflight. The change in heart rate from prone to standing was lower in the GCG subjects on landing day than in the control subjects. Within the GCG subjects only, the increase in total peripheral resistance from prone to standing was higher after spaceflight. CONCLUSIONS: The GCG prevented tachycardia and increased total peripheral resistance with standing after spaceflight. The GCG shows promise as a countermeasure against post-spaceflight orthostatic intolerance, can be easily donned, and is relatively comfortable to wear, but has not been validated after long-duration spaceflight.

Cardiovascular regulation during body unweighting by lower body positive pressure.

BACKGROUND: We hypothesized that human cardiovascular responses to standing in reduced gravity environments, as on the Moon or Mars, could be modeled using a lower body positive pressure (LBPP) chamber. METHODS: Heart rate, blood pressure, body segment fluid shifts, ECG, indexes of sympathetic, parasympathetic balance, and baroreflex control of the heart and periphery plus echocardiographic measures of cardiac function were recorded from seven men and seven women supine and standing at 100% (Earth), 40% (-Mars), and 20% (-Moon) bodyweights (BW). RESULTS: The fluid shifted from the chest was greater when standing at 100% BW than at 20% and 40% BW, while fluid pooled in the abdomen was similar at all BWs. Compared to moving from supine to standing at 100% BW, moving to 20% and 40% BW resulted in smaller decreases in stroke volume and pulse pressure, smaller increases in heart rate and smaller decreases in parasympathetic control of heart rate, baroreflex slope, numbers of blood pressure ramps, and much reduced indexes of sympathetic drive to the heart and periphery. However, peripheral vascular resistance, systolic pressure, and baroreflex effectiveness were elevated during 20% and 40% BW, compared to supine and standing at 100% BW. DISCUSSION: Standing at reduced bodyweight suppressed indexes of sympathetic control of heart rate and peripheral vasomotion. Regulatory responses indicated a combination of arterial and cardiopulmonary baroreflex control: mean heart rate, vasomotion, and baroreflex sensitivity appeared to be more under cardiopulmonary control while baroreflex effectiveness appeared to be driven more by the arterial baroreflex.

Artificial gravity training reduces bed rest-induced cardiovascular deconditioning.

We studied 15 men (8 treatment, 7 control) before and after 21 days of 6º head-down tilt to determine whether daily, 1-h exposures to 1.0 G(z) (at the heart) artificial gravity (AG) would prevent bed rest-induced cardiovascular deconditioning. Testing included echocardiographic analysis of cardiac function, plasma volume (PV), aerobic power (VO(2)pk) and cardiovascular and neuroendocrine responses to 80º head-up tilt (HUT). Data collected during HUT were ECG, stroke volume (SV), blood pressure (BP) and blood for catecholamines and vasoactive hormones. Heart rate (HR), cardiac output (CO), total peripheral resistance, and spectral power of BP and HR were calculated. Bed rest decreased PV, supine and HUT SV, and indices of cardiac function in both groups. Although PV was decreased in control and AG after bed rest, AG attenuated the decrease in orthostatic tolerance [pre- to post-bed rest change; control: -11.8 ± 2.0, AG: -6.0 ± 2.8 min (p = 0.012)] and VO(2)pk [pre- to post-bed rest change; control: -0.39 ± 0.11, AG: -0.17 ± 0.06 L/min (p = 0.041)]. AG prevented increases in pre-tilt levels of plasma renin activity [pre- to post-bed rest change; control: 1.53 ± 0.23, AG: -0.07 ± 0.34 ng/mL/h (p = 0.001)] and angiotensin II [pre- to post-bed rest change; control: 3.00 ± 1.04, AG: -0.63 ± 0.81 pg/mL (p = 0.009)] and increased HUT aldosterone [post-bed rest; control: 107 ± 30 pg/mL, AG: 229 ± 68 pg/mL (p = 0.045)] and norepinephrine [post-bed rest; control: 453 ± 107, AG: 732 ± 131 pg/mL (p = 0.003)]. We conclude that AG can mitigate some aspects of bed rest-induced cardiovascular deconditioning, including orthostatic intolerance and aerobic power. Mechanisms of improvement were not cardiac-mediated, but likely through improved sympathetic responsiveness to orthostatic stress.

Virtual guidance as a tool to obtain diagnostic ultrasound for spaceflight and remote environments.

INTRODUCTION: With missions planned to travel greater distances from Earth at ranges that make real-time two-way communication impractical, astronauts will be required to perform autonomous medical diagnostic procedures during future exploration missions. Virtual guidance is a form of just-in-time training developed to allow novice ultrasound operators to acquire diagnostically-adequate images of clinically relevant anatomical structures using a prerecorded audio/visual tutorial viewed in real-time. METHODS: Individuals without previous experience in ultrasound were recruited to perform carotid artery (N = 10) and ophthalmic (N = 9) ultrasound examinations using virtual guidance as their only training tool. In the carotid group, each untrained operator acquired two-dimensional, pulsed and color Doppler of the carotid artery. In the ophthalmic group, operators acquired representative images of the anterior chamber of the eye, retina, optic nerve, and nerve sheath. Ultrasound image quality was evaluated by independent imaging experts. RESULTS: Of the studies, 8 of the 10 carotid and 17 of 18 of the ophthalmic images (2 images collected per study) were judged to be diagnostically adequate. The quality of all but one of the ophthalmic images ranged from adequate to excellent. DISCUSSION: Diagnostically-adequate carotid and ophthalmic ultrasound examinations can be obtained by previously untrained operators with assistance from only an audio/video tutorial viewed in real time while scanning. This form of just-in-time training, which can be applied to other examinations, represents an opportunity to acquire important information for NASA flight surgeons and researchers when trained medical personnel are not available or when remote guidance is impractical.