Breathing

Abstract: Summary. The pulmonary arterial blood pressure was recorded in anaesthetized cats by means of a special cannula, according to MELLIN's technique. In most experiments the thorax was closed and the animal was breathing spontaneously. The pulmonary arterial pressure in 9 experiments averaged 23 cm water, or approximately 17 mm Hg, at an average systemic pressure of 132 mm Hg. The average ratio thus was about 1: 8, with the limits 1: 5 and 1: 14. Pressure variations of 1–2 cm blood synchronous with the breathing were regularly recorded. In one case, slow large waves of 1–2 minutes duration and about 5 cm amplitude were observed. Even great variations in the systemic blood pressure, elicited from the pressoregulating reflex mechanisms, were hardly accompanied by variations in the pulmonary arterial pressure. During muscular work a moderate rise in pulmonary blood pressure generally occurred, greater when air was breathed than when oxygen alone was administered. Clamping the pulmonary artery to one lung did not cause any change in systemic pressure (confirming LICHTHEIM and TIGERSTEDT) but caused a moderate rise in pulmonary arterial pressure. Breathing of pure oxygen lowered the pulmonary arterial pressure and oxygen-lack raised it. Carbon dioxide 6.5–20.5 per cent in oxygen raised the pressure sligthly, but constantly. These effects were not influenced by vagotomy. The effect of injections of adrenaline, nor-adrenaline, acetylcholine and histamine and of stimulation of pulmonary nerves were studied in some cases. The experiments seem to warrant the conclusion, that the regulation of the pulmonary blood flow is mainly mediated by a local action of the blood and alveolar gases leading to an adequate distribution of the blood through the various parts of the lungs according to the effeciency of aeration.

Abstract: Rationale: Sleep-disordered breathing recurrent intermittent hypoxia and sympathetic nervous system activity surges provide the milieu for cardiac arrhythmia development.Objective: We postulate that the prevalence of nocturnal cardiac arrhythmias is higher among subjects with than without sleep-disordered breathing.Methods: The prevalence of arrhythmias was compared in two samples of participants from the Sleep Heart Health Study frequency-matched on age, sex, race/ethnicity, and body mass index: (1) 228 subjects with sleep-disordered breathing (respiratory disturbance index ⩾ 30) and (2) 338 subjects without sleep-disordered breathing (respiratory disturbance index < 5).Results: Atrial fibrillation, nonsustained ventricular tachycardia, and complex ventricular ectopy (nonsustained ventricular tachycardia or bigeminy or trigeminy or quadrigeminy) were more common in subjects with sleep-disordered breathing compared with those without sleep-disordered breathing: 4.8 versus 0.9% (p = 0.003) for atrial fibri...

Abstract: The relationship of respiratory sinus arrhythmia amplitude (RSA) to tidal volume and breathing frequency was quantified during voluntarily controlled tidal volume and breathing frequency and spontaneous quiet breathing. Seventeen seated subjects breathed via mouthpiece and nose-clip, maintaining constant tidal volumes at each of several breathing frequencies. Inspiratory breath hold was zero frequency. Log RSA was plotted vs. log frequency for each tidal volume. The large stable RSA for frequencies less than 6 cycles/min was called low-frequency intercept (LFI, 20 +/- 5 beats/min). Low-frequency intercept was inversely proportional to a subject's age only to 35 yr. At higher breathing frequencies above a characteristic corner frequency (fC, 7.2 +/- 1.5 cycles/min) RSA decreased with constant slope (roll-off; 21 +/- 3.4 dB/decade). The RSA-volume relationship was linear permitting normalization of RSA-frequency curves for tidal volume to yield one curve. Spontaneous breathing data points fell on this curve. Voluntarily coupling of heart rate to breathing frequency in integer ratios reduced breath-by-breath variability of RSA without changing mean RSA. In conclusion, low-frequency intercept, corner frequency, and roll-off characterize an individual's RSA-frequency relationship during both voluntarily controlled and spontaneous breathing.

Abstract: KONNO, KIMIO, AND JERE MEAD. Measurement of the separate volume changes of rib cage and abdomen during breathing. J. Appl. Physiol. 22(3) : 407-422. I 967 .-Changes in the anteroposterior diameters of the rib cage and abdomen were recorded on the axes of a direct-writing X-Y recorder both during relaxation against a closed airway at different lung volumes, and while, at fixed lung volumes, displacements of volume were made voluntarily back and forth between the rib cage and abdomen in both the standing and supine postures. The family of isovolume lines was used to construct the volume-motion relationships for the rib cage and abdomen, and this in turn was used to estimate the separate volume changes of these parts during breathing. A high degree of volume dependence between the rib cage and abdomen was demonstrated under isovolume conditions, while a high degree of volume independence between these parts was demonstrated when total volume change was unconstrained. During breathing the chest wall deviated substantially from its passive configuration. In six subjects the abdomen accounted for about half or more of the tidal volume, but much less than half of the vital capacity, in both postures.