Chemoreflex drive of ventilation in the awake miniature pig.

Awake, resting miniature pigs trained to breathe through a respiratory mask were studied at neutral ambient temperature first intact, then after bilateral chronic carotid body denervation. Resting pulmonary ventilation (V), tidal volume (VT) and ventilatory period (T), and O2 and CO2 partial pressures in the end-tidal gas (PETO2, PETCO2) were measured cycle-by-cycle in steady state at levels of PETO2 ranging from 35 to 300 Torr, and in the course of NaCN injections and transient pure-O2 inhalation)30-sec O2-test). Steady state toxic CO2 ventilatory responses curves were determined.

Respiratory mechanics of Pekin ducks under four conditions: pressure breathing, anesthesia, paralysis or breathing CO2-enriched gas.

Impedance magnitude (Z) of the lower respiratory system was studied in Pekin ducks, using forced oscillations of a small volume at the airways opening in the range 1.6-16 Hz. The experiments were performed on 5 awake ducks enclosed in a body plethysmograph and spontaneously breathing ambient air at a transrespiratory pressure (Prs, the pressure difference between the lung and the body surface) which was varied in steps from -10 cm H2O (compression) to +10 cm H2O (distension).

Impedance of the lower respiratory system in ducks measured by forced oscillations during normal breathing.

The lower respiratory system of 10 conscious Pekin ducks breathing normally was subjected to superimposed oscillations of 1.3 to 16 Hz by a small volume piston pump. Induced sinusoidal flow (VO) and pressure (PO) signals were measured in late expiration, when the gas flow ventilated by the animal was minimum.

Ventilatory and circulatory O2 convection and blood acid-base changes in normoxic and hypoxic awake miniature swine.

1. Awake miniature swine were studied at rest and at neutral temperature while breathing either normoxic or hypoxic gas mixtures, PIO2 = 145 and 82 Torr, at low altitude. 2.

Carotid chemoreceptor function in ventilatory and circulatory O2 convection of exercising dogs at low and high altitude.

Awake dogs were studied before (control) and after chronic bilateral carotid denervation (denervated) at rest and running for 3 min on a treadmill at 8 km . h-1 and at various grades, in an altitude chamber operated either at 140 m or at 4000 m for 3 h. Steady-state pulmonary ventilation (Vg) and breathing pattern (VT, fR), oxygen consumption (MO2), O2 concentrations (C) and pressures (P) in the arterial (a) and mixed venous blood (v), hematocrit (Ht) and acid-base status in arterial blood, and heart frequency (fH) were measured.

The ventilatory responses of conscious dogs to isocapnic oxygen tests. a method of exploring the central component of respiratory drive and its dependence on O2 and CO2.

Conscious unrestrained dogs trained to breathe through a respiratory mask or, after chronic tracheostomy, through a cuffed endotracheal tube were studied in an altitude chamber operated in such a way that end-tidal PO2 was maintained at 100, 75 or 60 Torr. Each hypoxic experiment was completed within 1 h of the onset of hypoxia. At all levels of oxygenation, resting pulmonary ventilation (V), obtained from the tidal volume (VT) and ventilatory period (T), and alveolar gas tensions (PAO2, PACO2) were measured cycle-by-cycle before and during isocapnic O2-tests (IOT) at various steady levels of alveolar PCO2 ranging from 30 to 48 Torr.

Measurement of the distensibility of the parabronchi in duck lungs.

Air flow resistance in the parabronchial lung of the duck was measured at various pressure differences between the lung and the body surface (Prs) using a body plethysmograph. One lung of the anesthetized animal was ventilated at a steady flow rate, from trachea, through the parabronchial lung, and out via a cannula in the caudal thoracic air sac (Tr leads to CS flow), or vice versa (CS leads to Tr flow), all flow being directed over the parabronchi (Pb) by blocking the main bronchus between the medioventral (MV) and mediodorsal secondary bronchi (MD). Pressure differences were measured between MV and MD (Ptot), and between the clavicular air sac and MD giving the pressure drop along the parabronchial tubes (PPb).

O2-chemoreflex drive of ventilation in awake birds at rest.

Three varieties of birds (a non-flyer, the chicken; a diver, the duck; a flyer, the pigeon) were studied in resting conditions at neutral ambient temperature, while awake, either intact or sham operated, or after bilateral chronic carotid body denervation. Tidal volume (VT), ventilatory period (T) and minute volume (V = VT/T) measured plethysmographically, were recorded breath-by-breath in steady state at two levels of oxygenation, and in the course of transient pure O2 inhalation (60-sec O2-test). O2 partial pressures in the inspired and expired gases (PIO2 and PETO2), and in the arterial blood (PaO2) were also measured.

Ventilatory and circulatory O2 convection at 4000 m in pigeon at neutral or cold temperature.

Awake domestic pigeons, either maintained at 22 degrees C (series I) or acutely exposed at 2 degrees C (series II), were studied in a hypobaric chamber at 140 m and at various stages during a 4-week exposure to 4000 m. Steady-state pulmonary ventilation (Vg) and breathing pattern (VT, fr), oxygen consumption (MO2), O2 concentrations and pressures in the arterial (a) and mixed venous blood (v), hematocrit (Ht) and acid-base status in arterial blood, systolic blood pressure and heart frequency (fH) were measured. From these data cardiac output (Vb) and stroke volume (Vs), ventilatory and circulatory requirements (Vg/MO2, Vb/MO2), extraction of O2 from inspired air (EgO2) and blood EbO2), and capacitance coefficient of blood for oxygen (betabo2) were calculated.

Ventilatory acclimatization and csf acid-base balance in carotid chemodenervated dogs at 3550 m.

In three awake dogs in a hypobaric chamber at 140 m and at 3550 m, resting ventilation, pulmonary gas exchanges, respiratory gases and pH of the arterial blood, acid-base status in the cerebrospinal fluid (csf), and ventilatory responses to transient O2-inhalation were studied before (intact) and after chronic bilateral carotid body denervation (cbd). 1. The hypoxic chemoreflex drive of ventilation was reduced by about half in cbd dogs.

Blood and CSF acid-base changes, and rate of ventilatory acclimatization of awake dogs to 3,550 m.

Awake, intact dogs trained to wear a respiratory mask were studied in a hypobaric chamber at 140 m and at various stages of a 4-week exposure to 3,550 m. Resting ventilation, pulmonary gas exchanges, arterial blood gases and pH, acid-base status of the cisternal fluid (CSF) and ventilatory responses to transient O2 inhalation were measured. Attention is focussed on the time course of ventilatory acclimatization to altitude, characterized by hyperventilation with hypocapnia and a consequent increase of arterial Po2.