SUMMARY1. Three normal subjects performed rest-exercise transitions on a cycle ergometer, from rest to unloaded pedalling (0 W), 50, 100 and 150 W. Each experiment was performed in triplicate, with randomized work load order, in two sessions. Ventilation was obtained breath-to-breath by integration of a pneumotachygraph signal, and cardiac output beat-to-beat by a new development of the Doppler technique. Results were bin-averaged in 4 s bins over the first 20 s, and compared to resting values.2. Both ventilation and cardiac output increased significantly in the first 2 s. This initial rise in ventilation was due entirely to an increase in rate, the subsequent rise mainly to increase in tidal volume. Cardiac output increased predominantly through change in rate with smaller increases in stroke volume.3. A striking feature was a tendency for ventilation and cardiac output responses to be biphasic with an initial rise followed by a slight fall at the 14 s mark, and a subsequent rise, at all work loads. Overall correlation between ventilation and cardiac output was therefore high (r = 0 92).4. Six normal subjects hyperventilated for 45 s voluntarily, (a) at rate 24/min and normal tidal volume; (b) at normal rate and tidal volume of 1-5 1; (c) at rate 24/min and tidal volume of 1-5 1. Cardiac output, averaged over 10-45 s, rose by 0 4, 0 5, and 1-0 1 min-respectively, with falls in end-tidal PCO, of 4, 6, and 8 mmHg.5. Six normal subjects hyperventilated for 60 s with rate 24/min and tidal volume of 1-4 1, and end-tidal Pco, maintained at 38 + 2 mmHg. Cardiac output, averaged from 10-60 s, rose by 1-0 I min'.6. With increased rate and tidal volume, whether isocapnic or hypocapnic, cardiac output responses showed an overshoot with a peak value at about 30 s.7. The hypothesis of 'cardiodynamic hyperpnoea' considers a possible effect of increasing cardiac output on ventilation. The effects of ventilation on cardiac output must also be considered. We propose an extended hypothesis involving stable positive feed-back.

The study was done to assess the influence of smoking on respiratory symptoms and respiratory function in sawmill workers in Benin City. 150 sawmill workers who were all males and aged between 18 and 50 years, and had been in continuous employment in sawmill factories for a minimum of one year were studied. They were selected by a two-stage random sampling process from sawmills in Benin City. These were compared to 150 age and sex matched controls in order to determine the effect of sawdust exposure on the respiratory system. Questionnaire was used to elicit morbidity patterns and anthropometric measurements were also made. Respiratory rates, Peak Expiratory Flow Rates and Blood Pressures were measured in both groups. Respiratory symptoms were more common among sawmill workers compared to the controls. Smoking by some of these workers further aggravated their respiratory symptoms. Although blood pressure was similar in both groups, Respiratory rates were higher and Peak Flow Rates were lower in the sawmill workers compared to the controls (20.83  2.02 cycles/minute and 516.72  38.48 L/minute for the sawmill workers; 15.45  1.23 cycles/minute and 575.37  27.34 L/minute for the controls, respectively). Less than 5% of the sawmill workers wore protective devices/clothing, and health and safety standards were neither practiced nor enforced. The findings suggest that respiratory symptoms especially sputum production and chest pain are common in sawmill workers. Respiratory function is compromised in these workers.

1. Twenty-seven young subjects used their right hand to perform sustained, isometric contractions at 40% of maximum for 2 min while lying supine. 2. During the last 30 s of exercise, mean arterial blood pressure increased by 38 +/- 4 mmHg (mean +/- S.E.M.) and heart rate by 27 +/- 2 beats/min. 3. Nineteen of the subjects respired eucapnically during exercise, increasing ventilation by 4.1 +/- 0.5 litres/min. Eight subjects hyperventilated (7.1-19.6 litres/min) and decreased end-tidal PCO2 by 8.2 to 15.1 mmHg during the last minute of exercise. 4. In the eucapnic subjects mean flow velocity in the right (i.e. contralateral to the activated cortex) middle cerebral artery increased by 11.4 +/- 1.0 cm/s, a change of 17%, during the contraction. This represents an increase in volume flow to the territory of this vessel, but an increase in global flow to the brain cannot be inferred. 5. In the eight subjects who hyperventilated during exercise, there was no rise of flow velocity in the middle cerebral artery, and in some subjects there was a fall during the first 2 min of recovery. These findings suggest that if subjects hyperventilate during handgrip exercise there could be a fall in volume flow to many regions of the brain during and after the exercise.

We have measured aortic flow in the ascending aorta in man with a Bach-Simpson BVM 202 blood velocity meter, and aortic root diameter by M-mode echocardiography, and thus derived beat-to-beat cardiac output (Q). We tested the technique in 21 patients (53 comparisons) with various cardiovascular problems against a thermodilution method, and in four normal subjects at rest and two levels of exercise (50 and 100 W) against a nitrous oxide rebreathing method. We obtained excellent overall correlation in a range of 0.5-10 litres/min (r = 0.98, n = 77, sy,x = 0.48 litre/min), the formula for the least squares regression being: (Q Doppler) = 0.95 (Q Thermodilution/N2O) + 0.11 litre/min. The Doppler signal is sufficiently noise-free to obtain maximum acceleration of flow from the first derivative of velocity.

Summary: Hypertension, and the effect of graded exercise on Blood pressure (BP), in 60 obese nonathletic young medical students (40 females and 20 males) with Body Mass Index (BMI) greater than 30 were studied. The subjects were in the age range of 18-22 years with mean age of 20.301.32 years. Twenty percent of the males and 7 percent of the females were found to be hypertensives (P<0.05) and the severity of the hypertension significantly (P< 0.05) increased linearly with increase in BMI (r =0.6). Our study reveals a positive direct correlation between obesity and socioeconomic status and BP. Marked increases in systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), time of return (RT) were observed in the obese individuals compared to control at all levels of graded exercise with the highest rises seen during severe exercise. Among the obese subjects, the increases in BP were more in the males than females, but time of return was higher in females than males. This study further confirms that obese young individuals are prone to early onset of hypertension and thus other cardiovascular diseases and less tolerant to physical exercises. Our results add to the evidence that hypertension is common among obese young adults.