Total parenteral nutrition (TPN), specifically amino acid infusions, has been shown to increase the ventilatory response to inhaled CO2. The hypothesis tested was that morphine sulfate (known to depress ventilatory CO2 responsiveness) would diminish the augmented ventilatory CO2 response in patients receiving TPN. The influence of morphine on hyperoxic hypercapnic ...

To study pulmonary gas transport in panting, expirograms of several inert and respiratory gases were simultaneously measured in panting dogs. The experiments were performed on 5 conscious dogs (mean body weight 34.4 kg) provided with a chronic tracheostomy. Panting at a mean frequency of 312/min (5.2 Hz) was induced by ...

This paper reviewed in short neural and humoral factors which might be responsible for inducing exercise hyperpnea. As one of the neural factors afferent signals which arise in the exercising limbs and are transmitted via group III or IV high threshold sensory fibres were involved. The other neural factor is ...

This study was designed to examine the influence of carotid body (CB) hypocapnia on ventilation by selectively perfusing the CB through an extracorporeal circuit in 19 goats. When PcbCO2 was decreased from normocapnic levels in 14 awake goats (delta PcbCO2 = 10.9 Torr), PaCO2 increased 5.6 Torr (P less than ...

This paper reports the expired minute-ventilation (VE) responses of 5 subjects to three step levels in a) work rate on a bicycle ergometer (30, 50, and 70 W), b) inhaled constant fraction (CF) of CO2 (3, 5, and 7%), and c) inhaled constant flux (CFlux) of CO2 (0.3, 0.4, and ...

Static relationships between arterial, transcutaneous and end-tidal PCO2 (PaCO2, PtcCO2, PetCO2) as well as the dynamic relationship between PetCO2 and PtcCO2 were studied during moderate bicycle ergometer exercise with and without external CO2 loading. The exercise pattern consisted of 5-min intervals of constant power at 40 W and 100 W ...

We have studied the effect of acetazolamide 500 mg bd for three days on ventilatory response to CO2 (HCVR) and hypoxia under both isocapnic and poikilocapnic conditions (isocapnic and poikilocapnic HVR) in five normal subjects. Although acetazolamide reduced calculated arterial pH (7.41 [SEM] 0.01 to 7.37 [SEM] 0.01: p less ...

Nine subjects performed a sequence of sustained and randomised changes between 40 W and 100 W on a cycle ergometer while the end-tidal PO2 was kept close to 17.3 kPa (130 mm Hg) by means of a dynamic forcing technique (reference experiment). In a second series inspiratory CO2 was additionally ...

The present experiments have employed microelectrode techniques (pH and PCO2) and microcalorimetry (total CO2 concentration) to define parameters of acidification in specific structures of the rat testis and epididymis during control conditions and after administration of the carbonic anhydrase inhibitor acetazolamide (20 or 50 mg/kg). Values for in situ pH ...

The effect of oral caffeine on resting ventilation (VE), ventilatory responsiveness to progressive hyperoxic hypercapnia (HCVR), isocapnic hypoxia (HVR), and moderate exercise (EVR) below the anaerobic threshold (AT) was examined in seven healthy adults. Ventilatory responses were measured under three conditions: control (C) and after ingestion of either 650 mg ...

The carbon dioxide laser is used in the oral cavity for a variety of procedures. Although the procedures may not involve the teeth directly, precaution should be exercised to preserve their integrity. The results of this study indicate that the most limiting parameter for oral use of the CO2 laser ...

During twenty animal experiments the effectiveness of the gas exchange during extracorporeal membrane oxygenation (ECMO) was evaluated. Arteriovenous, venovenous and venoarterial perfusion systems were compared. While PO2 saturation values were sufficient in all three groups the PO2 values were significant higher during arteriovenous perfusion (84.22 +/- 3.5 mmHg) compared to ...

In five persons the transient ventilatory response was measured to three step levels of exercise, inhaled constant fraction of CO2, and inhaled constant flux of CO2. With constant CO2 fraction inhalation (3, 5, and 7%), the transient response of the minute-ventilation (VE) is associated with on- and off-time delays (Td). ...

The effects of sodium bicarbonate and a bicarbonate-carbonate mixture on expired CO2 and the volume of distribution of bicarbonate were studied in eight anesthetized, paralyzed, and ventilated dogs made acidotic with HCl (5 mmol/kg) infused over 90 min. Both sodium bicarbonate and Carbicarb resulted in systemic alkalinization and comparable increases ...

To investigate the contribution of vascular and metabolic stimuli to the sustained hyperpnea after exercise, the respiratory effects of obstructing and then releasing the femoral blood flow were recorded in 15 normal volunteers during recovery from steady-state cycle exercise (80 W). Obstruction was achieved using cuffs around the upper thighs, ...

The effects of almitrine bismesylate (initial intravenous dose 0.6 mg.kg-1 followed by continuous infusion of 0.4 mg.kg-1.h-1) on the ventilatory response to CO2 during hyperoxia and hypoxia were determined in 6 anaesthetized cats with the use of the dynamic end-tidal CO2 forcing technique. It was found that almitrine almost doubled ...

Infants with myelomeningocele have abnormalities in ventilatory control. To determine whether these persist into later life, we studied 14 patients with myelomeningocele and Arnold-Chiari malformation (age 18.0 +/- 0.8 (SE) years), and compared them with 14 control subjects (age 24.0 +/- 0.9 years). Pulmonary function and ventilatory muscle strength did ...

The effects of body temperature (Tb) on pulmonary stretch receptor (PSR) and CO2-sensitive intrapulmonary chemoreceptor (IPC) response characteristics may have important effects on ventilatory control in reptiles. In this study, three questions were addressed: (1) what are the effects of Tb on PSR and IPC responses to airway pressure (Paw) ...

The effects of exercise intensity and duration on blood gases in thoroughbred horses were studied to characterize the apparent exercise-induced failure in pulmonary gas exchange that occurs in these animals. In response to 2 min of exercise, arterial CO2 tension (PaCO2) decreased in mild and moderate exercise, returned to normocapnic ...

Tissue PCO2 (carbon dioxide tension) (PtCO2), interstitial H+ (H+e) and potassium activities (K+e) were monitored in the cerebral cortex of rats during and after 2-3 min of anoxia. Anoxia was associated with systemic hypotension and caused H+e (extracellular hydrogen ion activity) to increase from pH approximately equal to 7.2 to ...

A new technique has been developed to measure the transient response to inhaled CO2 using 30 sec pulses at constant inflow. Multiple experiments are ensemble-averaged in order to define the resulting small signals. We measured the peak changes in ventilation (delta V') and in PCO2 (delta PCO2), taking the ratio ...

The purpose of this study was to investigate the effects of furosemide, an inhibitor of NaCl cotransport, on cisternal cerebrospinal fluid (CSF) acid-base balance during acute respiratory acidosis (ARA). We measured blood and CSF acid-base variables in two groups (n = 7 in each) of anesthetized, paralyzed, and mechanically ventilated ...

The hypothesis that augmentation of the carotid chemoreceptor response to hypoxia by almitrine is due in part to an increased response to CO2 was tested by using single or few fiber preparation of carotid body chemosensory fibers in 12 cats anesthetized with alpha-chloralose. To differentiate between the plausible mechanisms of ...

Nasal CO2-sensitive receptors are reported to depress ventilatory frequency in several reptilian species in response to constant low levels of inspired CO2. The purpose of this study was to determine the influence of phasic patterns of CO2 in the upper airways on ventilation. Awake lizards (Tupinambis nigropunctatus) breathed through an ...

The effect of time of day on ratings of perceived exertion (RPE) at various intensities of cycling exercise, both below and above the ventilatory threshold, was studied in 32 subjects, 18 to 35 years of age. The ventilatory threshold occurred at the same (p greater than .05) mean (+/- SD) ...

During incremental exercise PCO2 does not fall for several work rates ('isocapnic buffering') above the anaerobic threshold (theta an). We explored this apparent lack of compensatory hyperventilation in 24 normal subjects who underwent incremental cycling (15 W/min) to exhaustion. Ventilation, pulmonary gas exchange, and end-tidal gas tensions were computed breath-by-breath. ...

Five healthy young men underwent two separate steady-state incremental exercise runs within the aerobic range on a treadmill with alternating periods of breathing with no load (NL) and with a discontinuous inspiratory elastic load (IEL) of approximately 10 cmH2O/l. End-tidal PCO2 was maintained constant throughout each run at the eucapnic ...

The ability of brain cells to regulate intracellular pH (pHi) and several phosphate metabolites was evaluated during 1 h of hypercapnia (inspiratory CO2 fraction of 0.10 and 0.05) in anesthetized rats by 31P high-field (145.6 MHz) nuclear magnetic resonance spectroscopy. Body temperature was maintained at 37 +/- 0.5 degrees C. ...

The CO2 production of 5 anaesthetized cats, ventilated to a constant PaCO2 and PaO2 by appropriate alteration of tidal volume and FIO2, was altered by means of an extracorporeal gas exchanger. Afferent chemoreceptor discharge was recorded from a single fibre preparation of the right carotid sinus nerve and the respiratory ...

Non-invasive transcutaneous blood gas monitoring techniques have been used as indicators of the effect of standing exercise on circulation in paraplegic subjects. Oxygen (tPO2) and carbon dioxide (tPCO2) electrodes were positioned on the chests and legs of a group of normal control subjects and a group of paraplegic subjects in ...

In humans, arterial PCO2 (PaCO2) has been demonstrated to be regulated at or near resting levels in the steady state of moderate exercise (i.e., for work rates not associated with a sustained lactic acidosis). To determine how PaCO2 might be expected to behave under the nonsteady-state conditions of incremental exercise ...

1. The transient ventilatory response to CO2, measured using short pulses at constant inflow, was compared with the steady-state response at rest and during exercise at 50 W, and with the rebreathing response at rest, in nine healthy subjects. At rest CO2 was given at flow rates of 0.2 and ...

We have investigated, in six healthy male volunteers, the effect of high thoracic extradural anaesthesia on the ventilatory pattern and hypercapnic ventilatory response. Ventilatory variables were determined using a respiratory inductive plethysmograph. Duration of inspiration, rib cage excursion and its contribution to tidal volume decreased significantly following extradural anaesthesia, while ...

The relationship between CO2 and ventilatory response to sustained hypoxia was examined in nine normal young adults. At three different levels of end-tidal partial pressure of CO2 (PETCO2, approximately 35, 41.8, and 44.3 Torr), isocapnic hypoxia was induced for 25 min and after 7 min of breathing 21% O2, isocapnic ...

Compensation for inspiratory flow-resistive loading was compared during progressive hypercapnia and incremental exercise to determine the effect of changing the background ventilatory stimulus and to assess the influence of the interindividual variability of the unloaded CO2 response on evaluation of load compensation in normal subjects. During progressive hypercapnia, ventilatory response ...

A study was designed to investigate the possibility that changes in ventral medullary extracellular fluid carbon dioxide tension (PCO2) and hydrogen ion (H+) concentration mediate the ventilatory stimulation induced by systemic administration of aminophylline. Six cats with peripheral chemodenervation (bilateral carotid sinus nerve and vagal neurotomy) were studied while anaesthetised ...

Intracellular pH (pHi) is a significant modifier of cell-to-cell communication in some tissues but its role is uncertain in heart tissue. The present studies examined the effect of cytosolic protons on electrotonic spread and conduction velocity in cardiac Purkinje fibers. Cable analysis provided values for internal longitudinal resistance (ri) and ...

In order to know the role of cardiodynamic factors for exercise hyperpnea, ventilation and several cardiorespiratory variables were measured simultaneously in human subjects during exercise. Cardiac output (Q) and mixed venous CO2 content (CVCO2) were determined by a rebreathing method. The correlation coefficients (r) for the relationships between minute expiratory ...

Five men performed an incremental exercise test following a normal, low and high carbohydrate dietary regimen over a 7-day period, to examine the influence of an altered carbohydrate energy intake on the relationship between the ventilation (VET) and lactate (LaT) thresholds. VET and LaT were determined from the ventilatory equivalents ...

In order to examine the role of respiratory oscillation of PaCO2 (CO2 oscillation) in the control of respiration, we performed veno-venous bypass using a membrane lung in 10 anesthetized paralyzed dogs, where the dog was put on fixed mechanical ventilation so that we could keep average PaCO2 and PaO2 constant ...

1. The threshold of the ventilatory response to carbon dioxide mediated by the peripheral chemoreceptors was determined under mild hypoxic conditions during both rest and exercise in eight volunteers. 2. The method used was an adaptation of the Read rebreathing technique, modified for hypoxia and with prior hyperventilation. The method ...

The effect of prolonged hypercapnia on carotid chemoreceptor discharge frequency has not been elucidated. In addition, the effect of acute hypercapnia on chemoreceptor discharge has not been determined in the goat, a species commonly used for ventilatory control studies. Therefore, we determined the effects of acute and prolonged normoxic-hypercapnia on ...

We examined the role of CO2 responsiveness and breathing efficiency in limiting exercise capacity in 15 patients with chronic airway obstruction (FEV1 = 0.88 +/- 0.25 L, mean +/- SD). Responses of minute ventilation and P0.1 (mouth pressure 0.1 s after the onset of occluded inspiration) to hypercapnia (delta VE/delta ...

The pulmonary responses and changes in plasma acid-base status occurring across the inactive forearm muscle were examined after 30 s of intense exercise in six male subjects exercising on an isokinetic cycle ergometer. Arterial and deep forearm venous blood were sampled at rest and during 10 min after exercise; ventilation ...

The ratio G = delta VE/delta VCO2 where delta VA is change in ventilation and delta VCO2 is change in CO2 production, is often used to quantitate the ventilatory response to exercise and is the overall system gain (G). However, the actual variable of interest often is the gain for ...

We studied the interaction of O2 and CO2 at the peripheral chemoreceptors in 6 two-week-old awake lambs. The method used, which selectively tested the peripheral chemoreceptors, measured the immediate ventilatory (VE) response to pure O2 and then to O2 + CO2. From room air, the animal was switched abruptly to ...

The problem faced in determining the ventilatory response to CO2 near eupnea has been the difficulty of unloading metabolically produced CO2 from the subject in the steady state. Previous methods using extracorporeal circuits to unload CO2 are technically difficult and provide a limited number of experimental states per experiment. Using ...

In the treatment of critically ill patients, it may be important to know the values of total diurnal O2 consumption and CO2 production. Often, diurnal values are obtained by extrapolation from the easily obtained short interval values. However, both stochastic and systematic errors can be introduced. This study analyzes the ...

The CO2 response of the phrenic neurogram before and during CO-induced isocapnic brain hypoxia was studied in peripherally chemodenervated, vagotomized, paralyzed, ventilated cats with blood pressure held constant. During inhalation of 0.5% CO in 40% O2, arterial O2 content (CaO2) was reduced to 40% and minute phrenic activity to 38.4 ...

We investigated the effects of selective large changes in the acid-base environment of medullary chemoreceptors on the control of exercise hyperpnea in unanesthetized goats. Four intact and two carotid body-denervated goats underwent cisternal perfusion with mock cerebrospinal fluid (CSF) of markedly varying [HCO-3] (CSF [H+] = 21-95 neq/l; pH 7.68-7.02) ...