Dyspnoea,disability, and distance walked: comparison of estimates of exercise performance in respiratory disease.

Forty-four patients with airway obstruction and 18 with pulmonary infiltration were studied in an attempt to correlate exercise tolerance, as assessed by a simple walking test, with basic respiratory function values and differing subjective assessments of exercise performance. The distance walked in 12 minutes was significantly correlated with the response to a structured questionnaire and with the patients'' assessment of performance using an oxygen-cost diagram. The distance walked did not agree well with simple subjective estimates obtained in the clinical history. It was better correlated with forced vital capacity than with forced expiratory volume in one second in both groups of patients, and was well correlated with carbon monoxide transfer factor in those with pulmonary infiltration. The scatter of results, however, was such that exercise performance could not usefully be predicted from the respiratory function values or from subjective assessments. Simple exercise tests are an essential part of assessing disability and response to treatment in patients with respiratory impairment.     

Are "pink puffers" more breathless than "blue bloaters"?

Breathlessness, disability, and exercise tolerance were assessed in 26 patients with severe chronic airflow limitation (forced expiratory volume in one second (FEV1) less than or equal to 1 litre) divided into two groups--15 patients who were normocapnic (pressure of arterial carbon dioxide (Paco2) less than 5.5 kPa (less than 41.4 mm Hg)), and 11 patients who were hypercapnic (Paco2 greater than 6 kPa (greater than than 45.1 mm Hg)). The two groups were well matched for spirometric values (FEV1 0.59 1 and 0.62 1, respectively). All of the hypercapnic patients could improve blood gas tensions towards normal by hyperventilation. There were no significant differences in visual analogue scores of breathlessness during treadmill exercise, disability (oxygen-cost diagram, dyspnoea grade), or exercise tolerance (six-minute walk, maximal consumption of oxygen during bicycle ergometry, distance walked to exhaustion in progressive treadmill test). The findings show that the "fight" to maintain normal blood gas tensions in the face of severe airflow limitation does not have an appreciable cost in terms of disability.     

Portable oxygen and exercise tolerance in patients with chronic hypoxic cor pulmonale.

Breathing 30% oxygen during exercise alleviated arterial hypoxaemia and reduced minute ventilation in patients with severe chronic bronchitis. A similar level of oxygen (2 or 4 litres of oxygen/minute) from nasal prongs also increased their exercise tolerance, as assessed by the distance that they could walk on the level in 12 minutes. Nevertheless, a single-blind controlled study showed that the effort of carrying their portable supply of liquid oxygen, in the Union Carbide Oxygen Walker, abolished this gain in exercise tolerance. The improvement in walking distance was restored when oxygen on exercise was provided by wheeling the oxygen walker on a light-weight shopping trolley.     

Effects of inhaled nitric oxide at rest and during exercise in idiopathic pulmonary fibrosis

Patients with idiopathic pulmonary fibrosis (IPF) usually develop hypoxemia and pulmonary hypertension when exercising. To what extent endothelium-derived vasodilating agents modify these changes is unknown. The study was aimed to investigate in patients with IPF whether exercise induces changes in plasma levels of endothelium-derived signaling mediators, and to assess the acute effects of inhaled nitric oxide (NO) on pulmonary hemodynamics and gas exchange, at rest and during exercise. We evaluated seven patients with IPF (6 men/1 woman; 57 ± 11 yr; forced vital capacity, 60 ± 13% predicted; carbon monoxide diffusing capacity, 52 ± 10% predicted). Levels of endothelin, 6-keto-prostaglandin-F(1α), thromboxane B(2), and nitrates were measured at rest and during submaximal exercise. Pulmonary hemodynamics and gas exchange, including ventilation-perfusion relationships, were assessed breathing ambient air and 40 ppm NO, both at rest and during submaximal exercise. The concentration of thromboxane B(2) increased during exercise (P = 0.046), whereas levels of other mediators did not change. The change in 6-keto-prostaglandin-F(1α) correlated with that of mean pulmonary arterial pressure (r = 0.94; P < 0.005). Inhaled NO reduced mean pulmonary arterial pressure at rest (-4.6 ± 2.1 mmHg) and during exercise (-11.7 ± 7.1 mmHg) (P = 0.001 and P = 0.004, respectively), without altering arterial oxygenation or ventilation-perfusion distributions in any of the study conditions. Alveolar-to-capillary oxygen diffusion limitation, which accounted for the decrease of arterial Po(2) during exercise, was not modified by NO administration. We conclude that, in IPF, some endothelium-derived signaling molecules may modulate the development of pulmonary hypertension during exercise, and that the administration of inhaled NO reduces pulmonary vascular resistance without disturbing gas exchange.     

腹式呼吸训练法对COPD伴Ⅱ型呼吸衰竭患者肺通气状态、血气指标及运动耐力的影响

摘要 目的：探讨腹式呼吸训练法对慢性阻塞性肺疾病（COPD）伴Ⅱ型呼吸衰竭患者肺通气状态、血气指标及运动耐力的影响。方法：选择我院2020年07月2022年12月期间收治的100例COPD伴Ⅱ型呼吸衰竭患者,根据随机数字表法将患者分为对照组[常规治疗基础上接受双水平气道正压（BIPAP）辅助通气,n=50]和研究组（对照组的基础上接受腹式呼吸训练法干预,n=50）。对比两组临床相关指标、肺通气状态、血气指标及运动耐力指标。结果：研究组的喘憋消失时间、体温恢复正常时间、住院时间、肺部啰音消失时间短于对照组（P<0.05）。两组干预1周后第1秒呼气的最大容积（FEV₁）、最大自主分钟通气量（MVV）、用力肺活量（FVC）均升高,且研究组高于对照组（P<0.05）。两组干预1周后氧分压（PaO2₂）、血氧饱和度（SpO₂）均升高,且研究组高于对照组;二氧化碳分压（PaCO₂）下降,且研究组低于对照组（P<0.05）。两组干预1周后6 min步行距离（6MWT）升高,且研究组高于对照组（P<0.05）。结论：腹式呼吸训练法有助于改善COPD伴Ⅱ型呼吸衰竭患者的临床症状,调节肺通气状态、血气指标,提高运动耐力。     

Effect of changes in arterial oxygen content on circulation and physical performance.

To evaluate the effect of different levels of arterial oxygen content on hemodynamic parameters during exercise nine subjects performed submaximal bicycle or treadmill exercise and maximal treadmill exercise under three different experimental conditions: 1) breathing room air (control); 2) breathing 50% oxygen (hyperoxia); 3) after rebreathing a carbon monoxide gas mixture (hypoxia). Maximal oxygen consumption (Vo2 max) was significantly higher in hyperoxia (4.99 1/min) and significantly lower in hypoxia (3.80 1/min) than in the control experiment (4.43 1/min). Physical performance changes in parallel with Vo2 max. Maximal cardiac output (Qmax) was similar in hyperoxia as in control but was significantly lower in hypoxia mainly due to a decreased stroke volume. A correlation was found between Vo2 max and transported oxygen, i.e., Cao2 times Amax, thus suggesting that central circulation is an important limiting factor for human maximal aerobic power. During submaximal work HR was decreased in hyperoxia and increased in hypoxia. Corresponding Q values were unchanged except for a reduction during high submaximal exercise in hyperoxia.     

Plasma theophylline concentrations,six minute walking distances,and breathlessness in patients with chronic airflow obstruction.

Twenty patients with chronic bronchitis were given incremental dosages of a new slow release preparation of theophylline and observed for its effect on lung function and exercise tolerance. Measurements were made subjectively by using visual analogue scales and objectively using six minute walking distances and spirometry. The study was placebo controlled and had a double blind randomised design. In the dosages used (200, 400, 600, and 800 mg) theophylline produced no significant improvement in forced expiratory volume in one second or forced vital capacity, and there was no overall improvement in peak expiratory flow rate. Similarly, neither effort tolerance nor degree of breathlessness appeared to be influenced by the drug, even when unacceptably high dosages were used. By contrast, placebo yielded a 7% increase in the six minute walking distance. From these results it seems difficult to justify the routine, indiscriminate use of theophylline for chronic bronchitis.     

缩唇腹式呼吸联合呼吸操训练对慢性阻塞性肺疾病患者血气分析指标、肺功能和生活质量的影响

目的:探讨缩唇腹式呼吸联合呼吸操训练对慢性阻塞性肺疾病(COPD)患者血气分析指标、肺功能和生活质量的影响。方法:选取2020年1月-2021年4月期间就诊于我院的82例COPD患者,根据随机数字表法分为对照组(缩唇腹式呼吸训练,41例)和研究组(缩唇腹式呼吸结合呼吸操训练,41例),对比两组疗效、血气分析指标[动脉血二氧化碳分压(PaCO₂)、血氧分压(PaO₂)、血氧饱和度(SaO₂)]、肺功能[用力肺活量(FVC)、第1秒用力呼气容积(FEV₁)、第1秒用力呼气容积所占FVC的比例(FEV₁/FVC)]、生活质量[圣乔治呼吸问卷(SGRQ)评分]、6分钟步行试验(6MWT)距离、BODE指数。结果:研究组的临床总有效率明显高于对照组(P<0.05)。研究组治疗3个月后PaO₂、SaO₂高于对照组,PaCO₂低于对照组(P<0.05)。研究组治疗3个月后FEV₁、FVC、FEV₁/FVC高于对照组(P<0.05)。研究组治疗3个月后6MWT距离长于对照组,SGRQ评分、BODE指数低于对照组(P<0.05)。结论:缩唇腹式呼吸联合呼吸操训练可改善COPD患者血气分析指标,提高肺功能和运动耐力,改善生活质量,疗效显著。     

Bronchoconstriction in asthmatics exposed to sulfur dioxide during repeated exercise

Young male volunteers with mild asthma and hypersensitivity to methacholine were exposed for 75 min with natural breathing to 0.0, 0.25, 0.5, and 1.0 ppm SO2. Each exposure included three 10-min periods of moderate treadmill exercise (minute ventilation 21 l . m-2 . min-1, O2 consumption 25 ml . kg-1, and heart rate 120/min). Specific airway resistance (sRaw) was not significantly increased after exercise in 0.25 ppm SO2, relative to the control exposure (clean air). In 0.5 and 1.0 ppm SO2, sRaw was increased twofold and threefold above preexposure levels, respectively, corresponding to increases of 3.2 and 9.2 cmH2O . s in excess over the increases seen in clean air (P less than 0.001). There was a broad range of responses to exercise and SO2. The increases in sRaw after the second and third exercises were significantly less than after the first exercise. Respiratory impedance measured by forced random noise suggests that the induced bronchoconstriction was primarily associated with peripheral airways. These results confirm that mild asthmatics selected for methacholine sensitivity have as a group significant bronchoconstriction in response to short-term moderate exercise with natural breathing in 1.0 and 0.5 ppm SO2. In addition, the induced bronchoconstriction is decreased after short-term repeated exercise in SO2.     

The effect of carbon monoxide on haem-facilitated oxygen diffusion

The aim of this paper is to quantify the effect of small quantities of carbon monoxide on the facilitated diffusion of oxygen by haemoglobin in the steady state. It is the first phase in the study of a mathematical model for carbon monoxide poisoning. Here we extend the Wyman model for facilitated diffusion to the case in which there are two ligands. The equations are solved using an asymptotic technique developed by Murray. We obtain accurate analytic approximations for the biologically important quantities of the problem for various percentages of carbon monoxide. These are the concentrations of free oxygen, haemoglobin, oxyhaemoglobin and carboxyhaemoglobin, and hence the saturation of the protein and the facilitated oxygen flux. The major effect of very small quantities of carbon monoxide on the oxygen flux is shown.     

Effect of helium breathing on intercostal and quadriceps muscle blood flow during exercise in COPD patients

Emerging evidence indicates that, besides dyspnea relief, an improvement in locomotor muscle oxygen delivery may also contribute to enhanced exercise tolerance following normoxic heliox (replacement of inspired nitrogen by helium) administration in patients with chronic obstructive pulmonary disease (COPD). Whether blood flow redistribution from intercostal to locomotor muscles contributes to this improvement currently remains unknown. Accordingly, the objective of this study was to investigate whether such redistribution plays a role in improving locomotor muscle oxygen delivery while breathing heliox at near-maximal [75% peak work rate (WR(peak))], maximal (100%WR(peak)), and supramaximal (115%WR(peak)) exercise in COPD. Intercostal and vastus lateralis muscle perfusion was measured in 10 COPD patients (FEV(1) = 50.5 ± 5.5% predicted) by near-infrared spectroscopy using indocyanine green dye. Patients undertook exercise tests at 75 and 100%WR(peak) breathing either air or heliox and at 115%WR(peak) breathing heliox only. Patients did not exhibit exercise-induced hyperinflation. Normoxic heliox reduced respiratory muscle work and relieved dyspnea across all exercise intensities. During near-maximal exercise, quadriceps and intercostal muscle blood flows were greater, while breathing normoxic heliox compared with air (35.8 ± 7.0 vs. 29.0 ± 6.5 and 6.0 ± 1.3 vs. 4.9 ± 1.2 ml·min(-1)·100 g(-1), respectively; P < 0.05; mean ± SE). In addition, compared with air, normoxic heliox administration increased arterial oxygen content, as well as oxygen delivery to quadriceps and intercostal muscles (from 47 ± 9 to 60 ± 12, and from 8 ± 1 to 13 ± 3 mlO(2)·min(-1)·100 g(-1), respectively; P < 0.05). In contrast, normoxic heliox had neither an effect on systemic nor an effect on quadriceps or intercostal muscle blood flow and oxygen delivery during maximal or supramaximal exercise. Since intercostal muscle blood flow did not decrease by normoxic heliox administration, blood flow redistribution from intercostal to locomotor muscles does not represent a likely mechanism of improvement in locomotor muscle oxygen delivery. Our findings might not be applicable to patients who hyperinflate during exercise.     

Acute alterations in stroke volume during exercise at 3,100 m altitude.

Following 3 weeks exposure to an altitude of 3,100 m, the cardiac output response to upright submaximal exercise was examined in 3 healthy subjects breathing ambient air and breathing 60% oxygen. The procedure allowed acute alteration of the 2 conditions within a single testing period of 30 min, 60% oxygen breathing either preceding or following breathing ambient air. Cardiac output was also measured in two of the subjects during maximal exercise under these two conditions. Administration of the high oxygen inspirate during exercise had little effect on the level of cardiac output but resulted in an immediate bradycardia and a dramatic increase of approximately 16% in stroke volume. Stroke volumes during maximal exercise were also increased by approximately 10% by the administration of high oxygen. It is suggested that the condition of decreases exercise stroke volume which develops with chronic exposure to altitude may be largely the result of diminished myocardial contractility stemming from a condition of myocardial hypoxia.     

Effect of beta-adrenergic blockade on hyperventilation and exercise tolerance in emphysema

Ventilation, heart rate, and arterial blood gas tensions were measured at rest and during incremental exercise in 10 patients with emphysema after intravenous placebo or 7 mg metoprolol. Metoprolol reduced heart rate by 14% (P less than 0.001) and ventilation by 11% (P less than 0.01), but there was no significant difference in arterial O2 or CO2 tension (Pao2 and PaCO2, respectively). Metoprolol increased the time to exhaustion on a cycle ergometer (P less than 0.05) but did not improve the 12-min walking distance. A double-blind randomized crossover comparison of 4 wk treatment with atenolol (100 mg/day), metoprolol (100 mg/day), or matched placebo was performed in 12 patients with emphysema. Both beta-adrenoceptor antagonists reduced resting heart rate by 33% (P less than 0.001) and resting minute ventilation by 11% (P less than 0.025). There was no change in resting or exercise Pao2 or Paco2. During steady-state exercise on a cycle ergometer, atenolol and metoprolol reduced ventilation by 14 and 4%, respectively. This was accompanied by 11 and 5% reductions in O2 consumption (P less than 0.05) and 13 and 6% falls in CO2 production (P less than 0.05). There were no significant changes in tests of exercise tolerance, but forced expiratory volume in 1 s and forced vital capacity were reduced during beta 1-adrenergic blockade. beta 1-Blocking drugs reduce hyperventilation in emphysema by reducing pulmonary gas exchange without a change in arterial blood gas tensions. Increased airflow obstruction prevents this reduction being of therapeutic value.     

Intermittent claudication. The effect of physical training on walking tolerance and venous lactate concentration

Twenty-one patients with intermittent claudication underwent a physical exercise program lasting 8 weeks. The patients were classified on the basis of maximal walking tolerance (MWT) and diagnosis at the initial examination. Seven of the patients had a MWT less than 1,000 m and no symptoms of chronic obstructive airways disease (COAD) or angina (group A), seven had a MWT less than 1,000 m plus angina and/or COAD (group B) and seven had an unlimited (greater than 1,250 m) MWT (group C). At the completion of the training program all three groups showed a significant improvement in walking distance to pain and stress test capacity. During the post-training walking tolerance test, the venous lactate concentrations in group A were lower after 2 min and 4 min of exercise, and at exhaustion (P less than 0.05). Group A patients showed a significant correlation between an increase in MWT after training and a decrease in maximum lactate concentration measured during walking. Although the patients in group B had a significant increase in MWT, blood lactate concentrations in this group were not always decreased by physical training. Group C lactate concentrations were lower after 8 min, 15 min, and 30 min of walking (P less than 0.05). It is concluded that a physical training program increases walking tolerance in different categories of claudicants, and possible mechanisms for the improvement are discussed.     

缩唇腹式呼吸训练联合弹力带抗阻运动对慢性心力衰竭患者运动耐力、心肺功能及生活质量的影响

摘要 目的：观察缩唇腹式呼吸训练对联合弹力带抗阻运动对慢性心力衰竭（CHF）患者运动耐力、心肺功能及生活质量的影响。方法：选取2020年4月~2021年7月期间我院收治的CHF患者83例。按照双色球法将患者分为对照组（n=41）和观察组（n=42）,对照组接受弹力带抗阻运动,观察组接受缩唇腹式呼吸训练联合弹力带抗阻运动。观察两组运动耐力、心肺功能、生活质量及1年内再住院率和1年内死亡率情况。结果：两组干预4周后躯体领域评分、情绪领域评分、其他领域评分和总分均下降,且观察组低于对照组（P<0.05）。两组干预4周后用力肺活量（FVC）、第1秒用力呼气容积（FEV₁）、最大自主分钟通气量（MVV）、左室射血分数（LVEF）升高,且观察组高于对照组（P<0.05）,而左室舒张末期内径（LVEDD）、左室收缩末期内径（LVESD）下降,且观察组低于对照组（P<0.05）。两组干预4周后6 min步行距离试验（6MWT）、峰值摄氧量（VO_2peak ）及无氧阈值（AT）升高,且观察组高于对照组（P<0.05）。观察组的1年内再住院率、1年内死亡率均低于对照组（P<0.05）。结论：弹力带抗阻运动联合缩唇腹式呼吸训练可促进CHF患者心肺功能改善,提高运动耐力,促进生活质量提升,同时还可降低1年内再住院率、1年内死亡率,疗效较好。     

Effect of attitudes and beliefs on exercise tolerance in chronic bronchitis.

In 50 patients with chronic bronchitis the relation was assessed between exercise tolerance and pulmonary function and psychological factors, including subjective perception of exertion, mood, general psychiatric disturbance, and the attitudes and beliefs held by patients concerning themselves, their illness, and its treatment. Ventilatory capacity was significantly correlated with but a poor predictor of exercise tolerance. Subjective perception of exertion was most closely correlated with exercise tolerance. The distance walked in a 12-minute exercise test was significantly correlated with measurements of mood and with several attitudes and beliefs. Attitudes and beliefs greatly outweighed measurements of mood and ventilatory capacity as components in a multiple regression predicting distance walked in 12 minutes. This method of psychological assessment emphasises the importance of attitudes and beliefs in respiratory disability and may have useful applications in rehabilitation in other chronic diseases.     

布地格福与布地奈德福莫特罗粉对COPD缓解期患者肺功能、运动耐力的影响对比

摘要 目的：探讨布地格福与布地奈德福莫特罗粉对慢性阻塞性肺疾病（COPD）缓解期患者肺功能、运动耐力的影响。方法：选取2020年1月至2022年12月本院收治的300例COPD缓解期患者,将其随机分为A组（n=150）和B组（n=150）,A组予以布地格福吸入治疗,B组予以布地奈德莫特罗粉吸入治疗。连续治疗3个月后,比较两组疗效及用药安全性;比较两组肺功能、血气水平、运动耐力和生活质量、炎症指标变化。结果：连续治疗3个月后,A组治疗总有效率为96.00 %,高于对照组的90.00 %（P＜0.05）;治疗后两组第1 s用力呼气容积（FEV₁）、FEV₁/用力肺活量、FEV₁占预计值百分数、血氧分压、6 min步行距离较治疗前均有提升,且A组高于B组（P＜0.05）;治疗后两组残气容积/肺总量、二氧化碳分压、白细胞介素-17、基质金属蛋白酶-9、圣乔治呼吸问卷评分较治疗前均有降低,且A组低于B组（P＜0.05）;治疗期间两组均未发生严重的不良反应（P＞0.05）。结论：相较于布地奈德福莫特罗,布地格福对COPD缓解期的治疗效果更佳,能有效减低气道炎症损伤,改善其肺功能及血气水平,提升患者运动耐力及生活质量。     

Peak exercise capacity estimated from incremental shuttle walking test in patients with COPD: a methodological study

Background

In patients with COPD, both laboratory exercise tests and field walking tests are used to assess physical performance. In laboratory tests, peak exercise capacity in watts (W peak) and/or peak oxygen uptake (VO₂ peak) are assessed, whereas the performance on walking tests usually is expressed as distance walked. The aim of the study was to investigate the relationship between an incremental shuttle walking test (ISWT) and two laboratory cycle tests in order to assess whether W peak could be estimated from an ISWT.

Methods

Ninety-three patients with moderate or severe COPD performed an ISWT, an incremental cycle test (ICT) to measure W peak and a semi-steady-state cycle test with breath-by-breath gas exchange analysis (CPET) to measure VO₂ peak. Routine equations for conversion between cycle tests were used to estimate W peak from measured VO₂ peak (CPET). Conversion equation for estimation of W peak from ISWT was found by univariate regression.

Results

There was a significant correlation between W peak and distance walked on ISWT × body weight (r = 0.88, p < 0.0001). The agreement between W peak measured by ICT and estimated from ISWT was similar to the agreement between measured W peak (ICT) and W peak estimated from measured VO₂ peak by CPET.

Conclusion

Peak exercise capacity measured by an incremental cycle test could be estimated from an ISWT with similar accuracy as when estimated from peak oxygen uptake in patients with COPD.

     

Walking at moderate speed with heel-less shoes increases calf blood flow

This study was designed to examine the physiological and biochemical effects of wearing heel-less shoes over a wide range of walking speeds. Six male students wearing alternately regular shoes and heel-less shoes walked at the constant speeds of 60, 80, 100 and 120 m/min for 10 min on a treadmill at 0% grade. The average heart rate was higher during heel-less shoe trials than when subjects walked in regular shoes at each speed, but differences were not significant. The calf blood flow showed its highest mean value at 80 m/min when subjects walked in heel-less shoes, and at 100 m/min when they walked in regular shoes. However, at walking speeds higher than these, calf blood flow decreased for wearers of both types of shoes. The calf blood flow after 80 m/min was higher when walking in heel-less rather than regular shoes. Blood lactate concentration after walking in heel-less shoes at 120 m/min was significantly higher than basal level, but after walking in regular shoes it was unchanged from the level before walking. Noradrenaline concentration at 120 m/min while walking in heel-less shoes was significantly higher than while walking in regular shoes. In conclusion, walking exercise in heel-less shoes induced an increase of the calf blood flow at a moderate speed, and increased glycogen metabolism and noradrenaline secretion at a faster speed.     

Duration of Hydrogen Formation by Anabaena cylindrica B629 in Atmospheres of Argon, Air, and Nitrogen

The time course of hydrogen formation by Anabaena cylindrica was followed beneath an argon atmosphere alone and also beneath atmospheres of argon, nitrogen, and air in the presence of carbon monoxide (0.2%) and acetylene (5%). Hydrogen production beneath argon alone was comparable in rate and duration (7 to 12 days) to that which occurred beneath air in the presence of carbon monoxide (0.2%) and acetylene (5%). However, much greater longevity (16 to 26 days) and improved rates of hydrogen formation were obtained when algae were incubated beneath argon and particularly nitrogen, each supplemented with carbon monoxide and acetylene. The total hydrogen produced by these cultures was up to three times as much as that released by cultures incubated beneath argon alone. Hydrogen-oxygen ratios for argon cultures either with or without carbon monoxide and acetylene were initially 1:5 but approximated 1:2 when measured over the entire incubation period. In each case oxygen production and nitrogenase activity (acetylene reduction) continued at reduced rates after hydrogen evolution had ceased. The effects of methionine sulfoximine (2 μM), ammonium ions (0.5 mM), or both on oxygen production were generally negligible, while effects on hydrogen production were variable depending on the atmosphere used; in most cases, eventual destabilization of the system occurred. A brief comparison was made of the time courses of anaerobic and aerobic hydrogen formation by the marine cyanobacterium Calothrix membranacea. It was found that shaking of cultures was beneficial for hydrogen production but not strictly necessary. It is concluded that hydrogen production by A. cylindrica in air and particularly nitrogen in the presence of carbon monoxide and acetylene offers the best potential of the atmospheres considered on the basis of four criteria: rates and longevity of hydrogen formation, practicality of the atmosphere used, and tolerance of hydrogen evolution to slight changes in composition of the atmosphere.