Central origin vs. reflex feedback in the respiratory heart rate relationship.

In the midcollicular decerebrate cat we have observed unique respiratory variation in heart rate (respiratory-heart rate relationship, RHRR) in respiratory intervals of 2-7 s or Biot's breathing of paired breaths at 16-s intervals. Cardiac slowing that marked the respiratory segmentation of the heartbeat showed consistent relationship with the breath it preceded by 1 to 5 s. Thus, association of respiration and heartbeat must include synergistically central interrelated origins for respiration cardiac rates constituting the RHRR.

Respiratory heart rate relationship in the decerebrate cat.

The respiratory heart rate relationship was examined in 10 decerebrate cats. The relationship appears to be a multi-part phenomenon consisting of (1) the inspiratory acceleration of the heart rate, which is well known, plus (2) the tendency toward small numbered relationships of integers between heart and respiration, as for example 2:1 to 5:1 heart rate to respiratory rate rather than complete randomness in the multiples of cardiac intervals in the respiratory cycle, and (3) registry of the heart and respiratory cycles upon each other in conformity to definitions of linear autonomous systems. So the phenomenon can be attributable to the influence of respiration upon the heart, the influence of the heart upon respiration, resulting in the mutual influence of both in supplying the physiological needs of perfusion of the periphery revealing higher integrations which an autonomous system would require.

Decrease of ether induction time after exposure to dysbaric conditions in rat.

In 22 adult male albino rats (means = 565 g) it was consistently observed that the time required to anesthetize them with 5 ml of diethyl ether after a hyperbaric exposure of 6 ATA using compressed air decreased depending on the severity of the animals' post-decompression reaction to the compression-decompression exposure. Monitoring the time required to lightly anesthetize adult male rats with diethyl ether to a point of losing the righting reflex after a particular compression-decompression exposure provided an indication of the rats' post-exposure state of health. This technique aided in correctly establishing if a rat developed a degree of decompression sickness that may have otherwise gone unnoticed. The loss of resistance to ether induction as a result of decompression sickness may be related to alterations in the blood-brain barrier, blood perfusion inequities, or changes in cardiopulmonary mechanics due to the presence of gaseous emboli. Rats that survived the compression-decompression exposures showed a marked resistance to ether induction after 24 h of recovery.

The site of the integration of muscular activity and respiration.

Acutely decerebrate (midcollicular) cats do not, or rarely if ever, walk spontaneously; nor do they show phasic movements of progression. After low thoracic cordotomy in a Schiff-Sherrington preparation with enhanced forelimb rigidity, approximately 50% of the preparations begin to show spontaneous locomotory movements in the forelimbs. In some cases these movements are in periodic bursts, and at these times are associated with waxing hyperpnea beginning before the onset of the forelimb movements. This indicates the presence of an intrinsic exercise hyperpnea mechanism mediated within the central nervous system in centers caudal to the hypothalamus.

Physiological responses to spirometer load.

A transient time-dependent increase in tidal volume (TV) and respiratory rate has been observed as a spirometric loading effect in experiments on 22 decerebrate cats. Respiration was recorded via the impedance pneumograph throughout the entire experiment while tidal volume was measured at intervals of 10-60 min on a spirometer. A total of 233 spirograms was recorded. The mean control tidal volume was 14 ml/kg, followed by an average increase of 30%, 43%, 51%, and 64% at 30, 60, 90, and 120 sec on the spirometer respectively. Spirometric respiratory rate also increased and as a result instantaneous minute volumes (MV) showed increases up to nearly 400% of control. Maximal effects occurred within 80 sec reflecting a sequential combination of reflex (via vagal afferents) and chemical (increased CO2) factors reaching a new equilibrium. We also noted a spirometric regularization of previously irregular or periodic (Biot's) breathing. It is apparent that the spirometer introduces small and graded perturbations into respiratory control systems.