Open-loop analysis of Pax(x=CO2) oscillation in the dog.

Abstract

Venous C02 loading and/or unloading using an artificial lung was performed on dogs to evaluate whether changes in the rate of carbon dioxide output (V002) can be involved in the control of respiration. As the signal providing J'2 information, small fluctuations in arterial Pco2 (4Paco2) which synchronized with the respiratory cycle were estimated from both the mean Pa002 and the fluctuations in arterial pH (4pH) measured with a catheter tip ISFET (ion sensitive field-effect transistor) pH sensor inserted in the common carotid artery. The open-loop method was used to analyze the effects of various respiratory parameters such as j02, tidal volume, and respiratory frequency on the changes in dpH and 4Paco2. Findings are: (1) 4Paco2 was linearly proportional to VC02 while the correlation between 4pH and VC02 was less linear, (2) magnitude of 4pH was dependent on the changes in tidal volume while 4Pa0O2 was not, (3) both the amplitude and the positive slope of Pa002 oscillation were functions of respiratory frequency. These results suggest the possibility that if Vco2 itself takes part in the control of ventilation, it will be C02 oscillation which links ventilation with Vco2.

An Anti-hyperventilation Instruction Decreases the Drop in End-tidal CO2 and Symptoms of Hyperventilation During Breathing at 0.1 Hz

“…Therefore, the increase of air hunger was likely caused by an increase of blood gas oscillations as a result of low respiratory rate. Arterial gas tension oscillates at the same frequency as breathing (Band et al 1980; Semple 1984) and the amplitude of these oscillations increases when breathing frequency decreases (Takahashi et al 1984). Increased amplitude of oscillations presumably leads to a transient increase in arterial CO 2 at the end of exhalation, which elicits a feeling of air hunger.…”

V ˙ E and V ˙CO 2 remain tightly coupled during incremental cycling performed after a bout of high-intensity exercise

“…E follows increased CO 2 during light-to moderateintensity dynamic exercise without any measurable change in P a CO 2 (Wasserman 1978). Yamamoto and Edwards (1960) proposed that respiratory cycle oscillations in P a CO 2 and/or pH are the signals which mediate changes in E X Takahashi et al (1984) concluded that CO 2 may play a role in the control of ventilation and that CO 2 oscillations during the respiratory cycle may link E with CO 2 . However, the exact role of intrabreath CO 2 and pH oscillations in the control of breathing during exercise has not yet been determined.…”