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Biomedical subjects

R B Schoene

Publications and source records attributed to R B Schoene.

At least 73 records · Page 4Linked to original sources
PubMed1985

High altitude pulmonary edema and exercise at 4,400 meters on Mount McKinley. Effect of expiratory positive airway pressure.

Breathing against positive expiratory pressure has been used to improve gas exchange in many forms of pulmonary edema, and forced expiration against resistance during exercise has been advocated for climbing at high altitude as a method to optimize performance. To evaluate the effect of expiratory positive airway pressure (EPAP) on climbers with high altitude pulmonary edema (HAPE) and on exercise at high altitude, we studied four climbers with HAPE at rest and 13 healthy climbers during exercise on a bicycle ergometer at 4400 m. We measured minute ventilation (VI, L/min), arterial oxygen saturation (SaO2 percent), end-tidal carbon dioxide (PACO2, mm Hg), respiratory rate (RR), and heart rate (HR) during the last minute of a five minute interval at rest in the climbers with HAPE, and at rest, 300, and 600 kpm/minute workloads on a bicycle ergometer in the healthy subjects. The HAPE subjects demonstrated an increased SaO2 percent, no change in HR or VI, and a decrease in RR on EPAP as compared to control. In normal subjects, SaO2 percent, VI, and heart rate were significantly higher on EPAP 10 cm H2O than 0 cm H2O control (p less than 0.01, 0.01, and 0.05, respectively). The RR and PaCO2 were not significantly different. In summary, EPAP improves gas exchange in HAPE subjects at rest. The EPAP in normal subjects at high altitude resulted in a higher SaO2 percent at the expense of a higher VI and higher HR. These results suggest that the work of breathing is higher and the stroke volume lower on EPAP. The positive pressure mask may be an effective temporizing measure for victims of HAPE who cannot immediately go to a lower altitude.

Adult↗
PubMed1985

Marked suppression of ventilation while awake following massive ingestion of atenolol.

We describe a patient who ingested 5 g of atenolol with ethanol. After awakening, with repeat toxicology screen only showing atenolol, and in spite of normal voluntary breathing mechanics, he had marked suppression of his spontaneous respirations as measured by minute ventilation and by occlusion pressure with no incremental response to hypercapnic challenge. Subsequently, he recovered. Although we are unable to prove a causal relationship, future patients with atenolol overdose should be observed carefully for ventilatory failure, even if fully conscious.

Adult↗
PubMed1985

Pulmonary edema at high altitude. Review, pathophysiology, and update.

In summary, recent data suggest that HAPE is a permeability type of edema characterized by an influx of cells (primarily alveolar macrophages) and an increased protein concentration when compared with that of controls. A modest inflammatory response may be mitigated by the presence of an inhibitor to neutrophil chemotaxis. Further information would be helpful to document the course of the disease from its early and more subtle manifestations to its severe clinical form. In addition, insight into the role of biochemical mediators may lead to a better understanding and hence, to prevention and treatment of this potentially fatal disease. However, identity of the event or mediator which initiates the leak remains a mystery.

Adult↗
PubMed1985

Acetazolamide and exercise in sojourners to 6,300 meters--a preliminary study.

To examine the effect of acetazolamide on resting acid-base balance and on exercise performance at extreme altitude, we studied four members of the American Medical Research Expedition to Mount Everest at an altitude of 6,300 meters. After an initial progressive exercise test to exhaustion on a bicycle ergometer, subjects were re-studied after taking acetazolamide 250 mg every 8 h for three doses. We measured venous blood during rest for determination of hemoglobin, hematocrit, 2,3-diphosphoglycerate (DPG), bicarbonate, pH, P50, and arterial oxygen saturation by ear oximeter. The results showed that pH, bicarbonate, and DPG:hemoglobin ratio were lower on acetazolamide, whereas P50 at in vivo conditions was unchanged. Exercise ventilation and oxygen consumption for the same workload were slightly higher after acetazolamide, whereas VCO2/VO2 respiratory exchange ratio (R) was lower, and oxygen saturation was unchanged. Two of four subjects had decreased time at maximum workload on acetazolamide; none had an increased performance. The results of this study show that partial carbonic anhydrase inhibition in individuals sojourning to very high altitude produces a further base deficit and a metabolic acidosis, stimulates ventilation, and may impair maximum exercise performance. Although acetazolamide effectively prevents acute mountain sickness, it does not improve performance, and may even impair exercise performance at extreme altitude.

Acetazolamide↗
PubMed1984

Effects of topical betaxolol, timolol, and placebo on pulmonary function in asthmatic bronchitis.

To evaluate the effects of two beta-adrenergic blocking agents on cardiopulmonary function, we investigated two topical ophthalmologic preparations, betaxolol 1% and timolol 0.5%, in nine patients (eight men and one woman, ranging in age from 25 to 69 years) with reactive airway disease. The randomized, double-masked, crossover study used placebo eyedrops as the control, and each drug was tested on separate days. Spirometric measurements, respiratory rate, pulse rate, and blood pressure were observed at frequent intervals for four hours after the test solutions were instilled. At the end of the test, an inhaled beta-adrenergic stimulant (isoproterenol) was administered, and the measurements were repeated. Timolol produced a significant decrease in airflow, measured by forced expiratory volume in one second (FEV1) and the ratio of FEV1 to vital capacity at each observation time beyond 15 minutes. Betaxolol and placebo eyedrops produced no significant change from control values. These results suggested that timolol can adversely affect patients with reactive airway disease. Betaxolol eyedrops, conversely, caused no decrease in airflow in the same patients with proven airway disease.

Administration, Topical↗
PubMed1984

Plasma norepinephrine in normal young and aged men: relationship with sleep.

This study explored the relationship between age-related elevations of plasma norepinephrine (NE) levels (thought to reflect heightened sympathetic nervous system activity) and sleep. Plasma NE levels were consistently and significantly greater in 8 aged than 10 young men across a 24-hr study period. For both groups, plasma catecholamine levels remained stable near bedtimes and rise times and during spontaneous and experimentally induced nighttime awakenings; reversal of the sleep/wake pattern (nighttime wakefulness, daytime sleep) had little effect on the 24-hr plasma NE or sleep patterns, indicating that elevated NE cannot be attributed to altered sleep/wakefulness per se. The aged group had significantly more wakefulness and significantly higher plasma NE levels while in bed in all study conditions. These two variables were significantly correlated, suggesting that heightened sympathetic activity may fragment sleep with wakefulness in the aged.

Adult↗
PubMed1984

Pathophysiological patterns of resolution from acute oleic acid lung injury in the dog.

Lungs of mongrel dogs with permanent tracheostomies and implanted systemic pulmonary arterial catheters were injured by intravenous infusion of oleic acid (0.09 mg/kg). Injury resulted in extensive, multifocal, and nonrandomly distributed lung damage. Awake dogs were studied during a control period and 1, 4, and 7 days following injection of oleic acid. Standard gas exchange measurements, the inert gas elimination technique, and subsegmental bronchoalveolar lavage (BAL) were used. Five oleic acid dogs and two saline control dogs were killed after each study period for morphological evaluation. Control dogs did not develop significant gas exchange abnormalities but did have localized inflammatory reactions at the lavage site. The oleic acid dogs developed significant shunt at day 1 with resolution of shunt by day 7. The multifocal sites of oleic acid injury were virtually identical in appearance at a given time interval; they consisted of alveolar cell necrosis with varying amounts of hemorrhagic inflammatory exudation at day 1 followed by a proliferative reparative reaction resulting in substantial restoration of alveolar structure at day 7. BAL showed a suppurative inflammatory response with hemorrhage on day 1 and an increased number of macrophages by day 7. The oleic acid model of acute diffuse lung injury demonstrates several pathophysiological alterations that could be compared with pathomorphological changes during the acute injury phase and during the subsequent reparative phase.

Animals↗
PubMed1984

Relationship of hypoxic ventilatory response to exercise performance on Mount Everest.

At very high altitude, exercise performance in the human sojourner may depend on a sufficient hypoxic ventilatory response (HVR). To study the relationship of HVR to exercise performance at high altitude, we studied HVR at sea level and 5,400 m and exercise ventilation at sea level, 5,400 m, and 6,300 m in nine members of the American Medical Research Expedition to Everest. The relationship of HVR between individuals was maintained when HVR was repeated after acclimatization to 5,400 m (P less than 0.05). There was a significant correlation in all subjects between HVR and ventilatory equivalent during exercise at sea level (r = 0.704, P less than 0.05). Subjects were then grouped into high (H) and low (L) HVR responders (ventilation increase to end-tidal PO2 of 40 Torr = 21.2 +/- 5.4 and 5.6 +/- 0.9 1 X min-1, respectively. At low and moderate levels of exercise, ventilation at sea level and after acclimatization to 6,300 m was higher in the high HVR group. At 6,300 m blood O2 saturation (Sao2%) decreased from rest to maximum exercise: H = 8.3 +/- 1.8%, L = 20.0 +/- 2.5% (P less than 0.01). HVR correlated inversely in all subjects with the decrease in Sao2 from rest to maximum exercise (P less than 0.05). Climbers with the highest HVR values reached and slept at higher altitudes. We conclude that the relative value of HVR in our group of climbers was not significantly altered after acclimatization; HVR predicts exercise ventilation at sea level and high altitude; the drop in Sao2% that occurs with exercise is inversely related to HVR; and sojourners with high HVR may perform better at extreme altitude.

Altitude↗
PubMed1984

Effect of respiratory muscle weakness on P0.1 induced by partial curarization.

Mouth occlusion pressure 0.1 s after onset of inspiration (P0.1) reflects central respiratory drive (CRD), but its dependence on respiratory muscle strength is unknown. To clarify this relationship, we produced progressive levels of respiratory muscle weakness by infusion of d-tubocurarine in eight supine spontaneously breathing normal subjects. Hypercapnic ventilatory response (HCVR) was measured before curarization and at mild (mean inspiratory effort 62 +/- 3% of control), moderate (42 +/- 3%), and severe (23 +/- 1%) weakness. At the severe level of weakness 1) supine functional residual capacity was not significantly changed from base line, 2) the percent of base-line slope of delta P0.1/delta PCO2 (122 +/- 27%) was significantly greater (P less than 0.01) than that for change in expired minute ventilation (delta VE)/delta PCO2 (39 +/- 10%), 3) the percent of base-line delta P0.1/delta VE (381 +/- 46%) during HCVR was significantly increased (P less than 0.01), 4) the P0.1 response was significantly increased from base line at two out of three specific levels of PCO2 while the VE was unchanged or significantly decreased, and 5) peak inspiratory resistance did not significantly change. Thus P0.1, unlike VE, did not decrease with even severe respiratory muscle weakness. Indeed, P0.1 increased at two out of three levels of PCO2 under circumstances when higher CRD is expected. One potential explanation for the results is that P0.1 may at least qualitatively reflect CRD up to the level of severe respiratory muscle weakness attained in this study.

Adult↗
PubMed1984

Cardiac asystole during an hypoxic drive study in a normal subject.

A healthy 31-year-old man who had previously sojourned to an altitude of 5,000 meters with no detrimental effect developed sudden cardiac asystole during a progressive hypoxic ventilatory response ( HVR ) test. At the moment of asystole, his alveolar PO2 (PAO2) was 41 mm Hg and his arterial oxygen saturation (SaO2) was 81 percent. Cardiopulmonary resuscitation was initiated, and after 20 seconds of asystole and apnea, he recovered normal sinus rhythm and spontaneous respiration. A subsequent ECG and cardiac enzyme levels were normal. During testing, he demonstrated depressed ventilation in response to hypoxia and a slowing of the heart rate. Careful observation of heart rate and breath-by-breath ventilation during HVR tests may predict this potentially fatal complication.

Adult↗
PubMed1984

Nutrition for ultra-endurance: several hours to several months.

In conclusion, the nutritional needs of three types of ultra-endurance athletes have been reviewed. These include events of several hours, day-after-day competition, and prolonged true endurance expeditioneering. There are many requirements common to all three--an adequate supply of fuel already available, judicious repletion of fuel and fluid losses during the events, and postcompetition repletion, which pertains not only to training but also to events of several days' duration. Most importantly, the "competitive edge" can be maintained only with careful attention to all of these factors.

Diet↗
PubMed1983

Effect of acetazolamide on normoxic and hypoxic exercise in humans at sea level.

Acetazolamide (A) is a potent inhibitor of carbonic anhydrase. It has been shown to be efficacious in preventing acute mountain sickness as well as decreasing the O2 desaturation that occurs during sleep in individuals with chronic mountain sickness who live at altitude. Very little data, however, are available about its effect on exercise. We studied six healthy males in a double-blind cross-over design using acetazolamide and placebo (P) during normoxic and hypoxic (fractional inspired O2 = 0.118) progressive work exercise to exhaustion on a bicycle ergometer. A metabolic acidosis was documented in all subjects on A (P less than 0.045). Before exercise, subjects on A had 2.0 and 3.5 l/min increase in minute ventilation (VE) during normoxia (P = not significant) and hypoxia (P less than 0.005), respectively, and a 2.2% increase in arterialized O2 hemoglobin saturation (SaO2) during hypoxia. During normoxic and hypoxic exercise, VE/kpm and SaO2/kpm were significantly higher while the respiratory exchange ratio (R) was significantly lower on A. These effects were greater on hypoxia. During normoxia, maximal O2 consumption (1/min) was lower on A [3.1 +/- 0.4 (A) vs. 3.8 +/- 0.2 (P), P less than 0.025] and higher during hypoxia on A[2.6 +/- 0.7 (A) vs. 2.4 +/- 0.1 (P), P less than 0.05]. The increase in exercise VE on A may result in an increased alveolar and subsequent arterial O2 tension which may be important for exercise at altitude. Carbonic anhydrase inhibition may also affect CO2 transport in the lung, which may explain the lower R.

Acetazolamide↗
PubMed1983

Iron repletion decreases maximal exercise lactate concentrations in female athletes with minimal iron-deficiency anemia.

We studied the effect of 2 weeks of iron therapy on exercise performance and exercise-induced lactate production in trained women athletes: six control subjects with normal parameters of iron status and nine with mild iron-deficiency anemia defined by low Fe/TIBC, ferritin, and minimally decreased Hgb values. Iron therapy improved the abnormal measures of iron status and low Hgb in the second group to normal. Exercise performance in a progressive work-exercise protocol on a bicycle ergometer to exhaustion was unchanged after iron therapy in both groups; however, blood lactate levels at maximum exercise in the iron-deficient group decreased significantly from 10.3 +/- 0.6 mmol/L before therapy to 8.42 +/- 0.7 after therapy (p less than 0.03). The control subjects did not significantly alter lactate levels after maximal exercise on iron compared to placebo: 8.3 +/- 0.8 mmol/L vs. 8.5 +/- 0.7. Although there was not a significant difference in maximum exercise performance after iron therapy, these data support animal experiments implying that iron may play a role in oxidative metabolism and that minimal decreases in Hgb may impair arterial oxygen content enough to affect aerobic metabolism. In addition, these findings may have important implications for competitive women athletes in whom mild iron deficiency may go unnoticed.

Acidosis↗
PubMed1982

Acute mountain sickness and acetazolamide. Clinical efficacy and effect on ventilation.

Sixty-four climbers participated in a randomized clinical trial of acetazolamide prophylaxis for acute mountain sickness (AMS) during rapid, active ascent of MT Rainier. Twenty-nine (93.6%) of 31 climbers receiving acetazolamide and 25 (75.8%) of 33 receiving placebo attained the summit. Time spent ascending from sea level to the summit (4,394 m) averaged 33.5 hours (range, 23 to 48 hours). On the summit AMS was less common in climbers receiving acetazolamide, and they experienced less headache, nausea, drowsiness, shortness of breath, and dizziness and a greater sense of satisfaction and psychological well-being. Minute ventilation on the summit was significantly greater in subjects taking acetazolamide (24.9 +/- 2.0 L/min compared with 16.9 +/- 3.8 L/min). Expired vital capacity was also greater on the summit in the acetazolamide group (6.9 +/- 0.4 L compared with 5.8 +/- 0.4 L). We conclude that acetazolamide is effective in the prophylaxis of AMS for climbers attempting rapid, active ascent. Increased ventilation at altitude, producing an increased alveolar oxygen tension, may be related to the observed amelioration of symptoms.

Acetazolamide↗
PubMed1982

Augmentation of exercise ventilation by medroxyprogesterone acetate.

The influence of medroxyprogesterone acetate (MPA) on exercise performance was studied in a double-blind cross-over trial using six normal males to compare the exercise performance changes to those observed in a previous study of exercise responses of female subjects during the follicular and luteal phase of the menstrual cycle. A maximal progressive work exercise test on a cycle ergometer was performed after 2 weeks of placebo or MPA administration. Although five of six subjects spontaneously complained of increased exertional dyspnoea on MPA, no significant decreases were documented in maximal exercise time or in maximal oxygen consumption. A mean increase in exercise ventilation of 19% at low levels of exertion and 26% at high levels of exertion was documented, but no subject demonstrated evidence of ventilatory limitation. The increases in exercise ventilation observed in these male subjects after MPA administration were larger than those observed in the previous study comparing exercise ventilatory responses during follicular and luteal phases of the menstrual cycle. It seems possible that some other exercise-related modulator of the ventilatory response to exercise under the influence of progesterone is present in either male subjects receiving MPA or women with normal hormonal cycles.

Adult↗
PubMed1982

Control of ventilation in climbers to extreme altitude.

Blunted chemosensitivity has been found in successful endurance athletes and some high-altitude natives. This characteristic, however, may not be beneficial to climbers at extreme altitude, where a vigorous ventilatory response to hypoxia may be of value in enhancing alveolar and arterial oxygenation. We studied 14 climbers who had climbed to 7,470 m or higher, 10 age-matched controls, and 10 outstanding middle- and long-distance runners. The ventilatory response to progressive hypoxia was determined at a constant, normal end-tidal Pco2 over 8-12 min and to CO2 by rebreathing a 7% CO2 hyperoxic mixture (Read technique). The hypoxic response parameter of Weil, A was used to determine the hypoxic responses and S (delta VE/ delta PACO2) the hypercapnic response. Climbers had A values significantly higher than the runners (means +/- SE: 158.9 +/- 29.9 vs. 49.3 +/- 7.1, P less than 0.001) but not significantly higher than the controls (109.9 +/- 21.0). delta VE/ delta PACO2 of climbers was higher (3.0 +/- 0.4) than both controls (2.2 +/- 0.2, P less than 0.025) and runners (1.4 +/- 0.2, P less than 0.0005). These data suggest that successful climbers to extreme altitude may be selected by virtue of their vigorous respiratory responses to hypoxia to maintain adequate oxygenation in the presence of extreme environmental hypoxia.

Adaptation, Physiological↗