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A prompt and sustained ventilatory output, greater than could be accounted for by the elevation of mean arterial carbon dioxide tension, occurred in response to a square-wave fluctuation of CO2 at the carotid bodies of dogs. Step perfusions with mean increments of 6.9 and 14.7 mm Hg Pco over control were associated with ventilation ratios of only 1.13 and 1.27, respectively. In contrast, during repeated square-wave perfusions, mean VR was 1.24 for a mean increment in Pco2 of only 4.9 mm Hg. The mean Pco2, of the square-wave perfusions was significantly lower than those of both step perfusions, and the mean VR of the square-wave perfusions was significantly higher than that of the lowest group of step perfusions. There was no evidence of adaptation of ventilation during the repeated square-wave perfusions. These findings support the concept that the pattern of application of a Co2 stimulus may provide an additional component to the chemical stimulus to respiration.

STUDIES of pulmonary function in patients with ankylosing spondylitis have established that the vital capacity is frequently reduced and that the maximum ventilatory capacity is decreased proportionately less than the vital capacity.1 2 3 In the most comprehensive survey of ventilatory function in this disease reported to date, Rogan, Needham and McDonald3 demonstrated that the reductions in vital capacity and total lung capacity were the most striking and consistently abnormal findings, and showed the best correlation with the severity of the disease as judged by radiologic criteria. Their studies also showed that the ratio of residual volume to total lung capacity was . . .

Since the description by Rosen, Castleman, and Liebow 1 of pulmonary alveolar proteinosis, various empiric methods of treatment have been proposed. Clinical improvement was noted in 3 of 21 cases during therapy with corticosteroids 1-10 and radiographic improvement on two 11,12 of seven patients 9,11,12,14 treated with potassium iodide. One of the two patients 12 who improved while receiving oral iodides also received streptokinase-streptodornase by aerosol. Aerosol therapy has been associated with clinical and rediographic improvement in three other cases—one received streptokinase-streptodornase 15 and two trypsin. 8,9 One patient 8 tolerated trypsin aerosol therapy for only six days, but the oral intake of 400 units of trypsin-chymotrypsin daily was associated with progressive clearing of the chest x-ray film. The efficacy of these regimens is still in question, however, since spontaneous remissions have been reported 1 and clinical observations in this rare disease have been, by necessity, limited and uncontrolled. This communication

A rebreathing method was used to study the increase in ventilation with an increase in PaCOCO2 in newborn infants and adults. The response curve of infants was shifted to the left of that of adults, which is consistent with their lower initial PaCOCO2 and buffer base, and greater metabolism per kilogram of body weight. The rebreathing response curves of infants were also to the left of steady-state responses reported by others. It is postulated that nonchemical stimuli caused higher ventilation throughout the entire range of the CO2 response curves in the infants studied by rebreathing without altering the sensitivity to increases in Pco2. The change in ventilation per kilogram versus the change in PaCOCO2, the slopes of the CO2 response curves, were nearly the same in infants and adults studied by either method. This finding, when the comparison is made on the basis of body weight, suggests the sensitivity of the regulatory apparatus does not change with age, and the output of the effector apparatus, lungs and chest wall, is related to the mass of the individual. CO2 response curves; nonchemical stimuli; chemical stimuli; respiration Submitted on February 19, 1963

The ventilatory responses of dogs during bilateral carotid artery perfusions with hypercapnic blood were determined to evaluate the effect upon ventilation of reaching an increment above control of 30.4 mm Hg Pco2 at different rates. A ramp change resulted in a prompt increase in ventilation to the level sustained during the subsequent apparently steady state. A step change resulted in an overshoot of ventilation beyond that anticipated for the ventilatory response if it followed the elevation of mean Pco2. Complete accommodation of ventilation to the ramp stimulus occurred by 5 seconds, when the mean carotid body PCO2 was 49 mm Hg. Following an abrupt decrease of 30.4 mm Hg PCO2, at the end of the perfusions, mean ventilation gradually decreased toward control without an undershoot. The combination of an “excess” ventilation during the ramp function and an “excess” ventilation during recovery suggests that a ramp stimulus at the carotid bodies acts as an effective additional component of the chemical stimulus to ventilation when initiated near eucapnic conditions. Arterial chemoreceptors Ventilatory responses to CO2 Control of breathing Ventilatory transients

Transient infusions of normal, acidic, hypercapnic, or buffered hypercapnic blood were made into the vertebral arteries of anesthetized dogs. The infusions of normal or acidic (hyperhydric-isocapnic) blood produced no statistical changes in ventilation during a 100 second infusion period. The infusions of hypercapnic blood produced an increase in ventilation after a delay of 20–30 sec, while the infusions of equally hypercapnic blood buffered with HCO-3, which prevented the normal drop in pH, produced a greater and more prompt increase in ventilation. These results suggest that under physiological conditions: 1) increased acidity of arterial blood does not stimulate the central chemoreceptors in the absence of an increase in PCO2; 2) the blood-borne agent leading to stimulation of the central chemoreceptors is molecular CO2; 3) increased blood [Hco-3] initially facilitates the stimulation of the centra] chemoreceptors during hypercapnia; 4) a sudden transitory change in arterial Pco produces its initial effect upon ventilation by stimulating chemoreceptors at the periphery.

A clinic is described that was designed to carry out functional evaluation of patients with chronic medical and psychiatric disabilities and to plan for their vocational rehabilitation. Th...