PURPOSE: To develop a new system for safely supplying carbon dioxide (CO2) to open-angle glaucoma patients. METHODS: The orbital hemodynamics of 7 glaucoma patients were determined by color Doppler imaging under baseline conditions and during CO2 supplementation sufficient to increase the end-tidal CO2 partial pressure by 10%. Systemic conditions, including ...

We compared the central-chemoreflex sensitivities estimated from steady-state tests with those estimated from rebreathing tests in five subjects. In one laboratory, each subject underwent nine dynamic end-tidal forcing experiments. Three repetitions of 3, 6 and 9 mmHg step changes in the end-tidal partial pressure of carbon dioxide, from a pre-step ...

Although considerable experimental and clinical knowledge exists on the physiology of pneumoperitoneum, insufflation of the preperitoneal space has not been extensively studied. The purpose of this study is to evaluate the physiology associated with preperitoneal carbon dioxide (CO2) insufflation in a porcine model. Eleven pigs weighing 35 to 45 kg ...

We investigated transcutaneous partial CO2 and O2 pressures and respiratory rate in unpremedicated elderly patients of ASA physical status 1 to 3 who underwent cataract surgery under retrobulbar anaesthesia. In group A no air suction was used. In group B suction was applied under the sterile drapes to avoid rebreathing ...

Acetazolamide, a carbonic anhydrase inhibitor, is used in patients with chronic obstructive pulmonary diseases and central sleep apnoea syndrome and in the prevention and treatment of the symptoms of acute mountain sickness. In these patients, the drug increases minute ventilation (V'E), resulting in an improvement in arterial oxygen saturation. However, ...

BACKGROUND: Early diagnosis and treatment of intra-abdominal pathology in critically ill intensive care unit (ICU) patients remains a clinical challenge. The objective of this study is to assess the feasibility of portable, bedside diagnostic laparoscopy (DL) in the ICU for patients suspected of intra-abdominal pathology, and to contrast its accuracy ...

The abdominal wall lift (AWL) has been proposed for laparoscopic cholecystectomy to reduce hemodynamic effects caused by carbon dioxide (CO2) and high intraabdominal pressures (IAP). Data concerning effects of AWL on respiratory mechanics are scant. We therefore used a noninvasive method to evaluate whether the AWL could offset these effects. ...

To clarify the influence of the head-up position on cerebral oxygen metabolism during laparoscopy with CO2 insufflation in 12 patients who underwent laparoscopic cholecystectomy, changes in the concentrations of cerebral oxyhemoglobin (HbO2), deoxyhemoglobin (Hb), total hemoglobin (total Hb) and oxidized cytochrome aa3 (Cyt aa3) were measured by use of near-infrared ...

Neurotoxin microinjected into the retrotrapezoid nucleus of anesthetized rats decreases phrenic activity and eliminates the response to CO2. In unanesthetized rats, such treatment has no effect on awake, resting breathing and decreases CO2 sensitivity by 40% (M. Akilesh, M. Kamper, A. Li, and E. E. Nattie. J. Appl. Physiol. 82: ...

An intravascular gas exchange device for the treatment of respiratory failure consisted of a multitude of blind-ended hollow fibers glued in a pine-needle arrangement to a central gas supply catheter. It has previously been shown that gas desorption rates can be significantly enhanced by cycling gas pressure between a hypobaric ...

OBJECTIVE: Instrumental dead space wash-out can be used to improve carbon dioxide clearance. The aim of this study was to define, using a bench test, an optimal protocol for long-term use, and to assess the efficacy of this technique in neonates. DESIGN: A bench test with an artificial lung model, ...

BACKGROUND: The influence of raised intraperitoneal pressure during laparoscopy on tumour growth and port site metastasis is still unknown. METHODS: Tumour growth of colonic adenocarcinoma DHD/K12/TRb was measured after laparoscopy with carbon dioxide at different pressures (0, 5, 10 and 15 mmHg) in a rat model. Cell kinetics were determined ...

A test method based on supercritical fluid extraction (SFE) and gas chromatography has been developed for some aromatic amines, such as 4-chloro-o-toluidine, beta-naphthylamine and 4-aminobiphenyl. A two-level factor design was used as the optimization procedure. Four main variables were considered: CO2 pressure, extraction temperature, static extraction time and volume of ...

The resting mouth occlusion pressure 0.1 s after onset of inspiration (P0.1) and minute ventilation (V'E) and their response to CO2 in patients with chronic obstructive pulmonary disease (COPD) remain controversial. The ventilatory drive and the factors that predict resting arterial CO2 tension (Pa,CO2) were studied in 19 eucapnic and ...

BACKGROUND: Diphenhydramine is used as an antipruritic and antiemetic in patients receiving opioids. Whether it might exacerbate opioid-induced ventilatory depression has not been determined. METHODS: The ventilatory response to carbon dioxide during hyperoxia and the ventilatory response to hypoxia during hypercapnia (end-tidal pressure of carbon dioxide [PETCO2] is approximately equal ...

The saccular lung in lizards is large and highly compliant compared with mammalian lungs, and these properties led us to question to what extent body movements could affect pulmonary gas exchange and the partial pressure of arterial blood gases. Specimens of two species of lizards, the frilled lizard (Chlamydosaurus kingii, ...

BACKGROUND: Intraabdominally insufflated carbon dioxide (CO2) during laparoscopy may have a specific effect on splanchnic circulation that may be unrelated to the effects of increased intraabdominal pressure alone. Therefore, the influences of insufflation with CO2 versus air on splanchnic circulation were compared. METHODS: Pigs were chronically instrumented for continuous recording ...

BACKGROUND: Although the low-flow CO2 insufflation rate used to initiate pneumoperitoneum may reduce the severity of potential venous embolism, its safety is not established. METHODS: Anesthetized pigs were ventilated with room air at a fixed minute ventilation. After 1 h of baseline, they were intravenously infused with CO2 at the ...

To clarify the control mechanism of ventilation during posture change, ventilatory parameters, PETCO2, and ventilatory response to CO2 were examined in 11 healthy male subjects at supine (0 degrees) and 75 degrees head-up tilt positions. Minute expiratory ventilation (V.E), tidal volume (VT), respiratory frequency (f), end-tidal and transcutaneous PCO2 and ...

Objective: The number and types of surgical procedures being preformed using laparoscopic technique is increasing due to technological advances. Recent studies suggest the carbon dioxide pneumoperitoneum and patient positioning causes hemodynamic alterations, respiratory acidosis, and a release of stress hormones. However, to date, no studies have investigated the physiological effect ...

For adequate and safe use of high-frequency jet ventilation (HFJV), reliable monitoring of the PCO2 status and course is necessary. Because of improved handling and performance, recently available transcutaneous PCO2 monitoring devices such as MicroGas 7650 (Kontron Instruments Medical Sensors, Basel, Switzerland) should enable more effective surveillance of CO2 elimination ...

We used a modified rebreathing technique to measure chemoreflex thresholds to CO2 in decerebrate, paralyzed and ventilated cats. Cats were hyperventilated to neural apnea (PaCO2 < 15 mmHg) with one ventilator and then switched to a rebreathing circuit consisting of a balloon inside a bottle connected to a second ventilator. ...

In order to elucidate if the inspiratory effort sensation (IES) associated with carbon dioxide (CO2) is independent of the concomitant increase in the ventilation, we studied 23 normal resting volunteers (mean age 34 +/- 11 yr) during CO2 rebreathing. Our main goal was to compare the IES at the same ...

We studied the effect of the interaction between diffusion limitation and alveolar ventilation to perfusion ratio (VA/Q) mismatch in the relation between blood gas partial pressures and cardiac output (Q). The analysis was based on a mathematical model of gas exchange involving two exchanging compartments and a right to left ...

We describe a model to calculate the buffering capacity of bicarbonate in the rumen. The addition of NaHCO3 results in the release of CO2 from solution and eventually from the rumen via eructation. This process directly neutralizes ruminal acidity. The degree to which the process continues depends on the partial ...

This tutorial review charts the development of electrochemical sensors for the analysis of blood-gases, gases and vapours in clinical medicine over the past four decades. The development of each sensor is set in its historical and clinical context, and the first part of the review concentrates on aqueous electrolyte electrochemistry ...

PURPOSE: To assess the effect of pneumoperitoneum on P(a-ET)CO2 gradient in children. METHODS: Sixty one ASA I and II children (10.7 +/- 3.0 yr, 38.4 +/- 14.2 kg, mean +/- SD), scheduled for visceral or urological laparoscopic procedures, were studied. They were anaesthetized, intubated, paralysed and their lungs ventilated with ...

We studied interactions between CO2 chemoreflexes and arterial baroreflexes in 10 supine healthy young men and women. We measured vagal carotid baroreceptor-cardiac reflexes and steady-state fast Fourier transform R-R interval and photoplethysmographic arterial pressure power spectra at three arterial pressure levels (nitroprusside, saline, and phenylephrine infusions) and three end-tidal CO2 ...

STUDY OBJECTIVE: To compare the rate of increase of arterial carbon dioxide tension (PaCO2) during apneic oxygenation preceded by acute respiratory hypocapnia with that during apnea preceded by respiratory eucapnia. DESIGN: Randomized, prospective, single crossover study. SETTING: Operating room at a teaching hospital. PATIENTS: 19 ASA physical status I, II, ...

BACKGROUND: We investigated the ability of pressurized CO2 gas to aerosolize B16 melanoma (B16) tumor cells in an in vitro model. METHODS: The experimental apparatus consisted of an 18.9-L plastic cylindrical vessel and a compliant latex pouch was attached to the top. Two 5-mm ports penetrated the vessel; insufflation and ...

BACKGROUND: Carbon dioxide (CO2) pneumoperitoneum for laparoscopic surgery increases arterial pressures, systemic vascular resistance and heart rate and decreases urine output. METHODS: In this double-blind randomized study esmolol, an ultrashort-acting beta1-adrenoceptor antagonist was compared with physiological saline (control) in 28 patients undergoing laparoscopic surgery in standardized 1 MAC isoflurane anaesthesia. ...

An analogue computer model has been constructed to simulate the dynamic behaviour of the human cardiorespiratory system for studying the effect of changes in different system-variables--as alveolar ventilation, functional residual capacity (FRC) of the human lung and the cardiac output--on the partial pressure of carbon dioxide in the arterial and ...

The purpose of the study was to determine whether chamber exposure to low levels of CO2 results in functional alterations in gas mixing and closing volume in humans. Four healthy volunteer subjects were exposed to 0.7% CO2 and to 1.2% CO2. Spirometry, lung volumes, single breath nitrogen washout, diffusing capacity ...

This study evaluated the incidence and factors involved in the occurrence of gas embolism after laparoscopic injuries. A 5-MHz transesophageal echocardiographic (TEE) probe was placed in 11 anesthetized pigs and used to examine the right cardiac chambers and pulmonary artery. A calibrated carbon dioxide analyzer continuously measured end-tidal carbon dioxide ...

OBJECTIVE: To evaluate the accuracy of physiologic deadspace (VD/VT) measurement, using a metabolic monitor. DESIGN: Prospective collection of data. SETTING: University-affiliated children's hospital with a 51-bed critical care area. PATIENTS: Infants and children who were sedated and paralyzed and were receiving mechanical ventilation through a cuffed endotracheal tube. INTERVENTIONS: None. ...

During laparoscopy, the increase of the carbon dioxide tension may increase the synthesis of hydrochloric acid in the parietal cells of the stomach; the source of the secreted hydrogen ions is carbonic acid derived from the hydration of carbon dioxide. The present report tests this hypothesis by correlating the changes ...

We studied the effect of pressure up to 300 bar on the catalytic efficiency of subtilisin Carlsberg suspended in compressed propane, near-critical ethane, near-critical carbon dioxide and tert-amyl alcohol, at constant temperature and fixed enzyme hydration. Increasing pressure lowered the catalytic efficiency of the enzyme in all the solvents, resulting ...

We investigated the effects of increasing CO2 ventilatory drive on the coordination of respiration and reflex swallowing elicited by continuous infusion of distilled water into the pharynx (2.5 ml/min) in 11 normal subjects. Ventilation was monitored using a pneumotachograph and swallowing was recorded by submental electromyogram. The CO2 ventilatory drive ...

The effect of modified ultrafiltration (MUF) after cardiopulmonary bypass for paediatric cardiac surgery was evaluated in 138 children with moderate to severe congenital heart disease. The median age was 0.4 years (0 days to 6.5 years), and the weight 5.3 kg (2.2-20 kg). The operation was discontinued in six cases, ...

The use of laparoscopy for the diagnosis or therapeutic management of abdominal disease in the horse has distinct advantages when it allows the horse to remain standing. However, distending the abdomen by insufflation of a biologically active gas in an anaesthetised horse may add to the physiological challenge of general ...

The intraperitoneal insufflation of carbon dioxide during laparoscopic procedures is associated with an increase in mean arterial pressure and systemic vascular resistance. To evaluate the time course of the circulatory changes related to intraabdominal pressure variation, we used transesophageal echocardiography in 10 patients anesthetized for laparoscopic cholecystectomy. Left ventricular dimensions, ...

BACKGROUND: This study investigated three factors postulated to be sources of physiological stress in laparoscopic surgery: hypercarbia, elevated intraabdominal pressure, and the steep Trendelenburg position. Our research was designed to define the effects of each of these potential stressors on hemodynamic responses observed during laparoscopic colectomy in pigs. METHODS: Twenty-four ...

OBJECTIVE: To evaluate and compare the effect of tracheal gas insufflation using two gases with different physical properties, helium and oxygen, as an adjunct to conventional mechanical ventilation in patients with respiratory failure. DESIGN: Prospective, intervention study. SETTING: General intensive care unit in a tertiary university medical center. PATIENTS: Seven ...

Cardiovascular changes due to pneumoperitoneum during laparoscopic surgery are established in adult patients, but not known in infants. We investigated the hemodynamic effects of laparoscopy during general anesthesia in 12 ASA physical status I infants by using noninvasive continuous esophageal aortic blood flow (ABF) echo-Doppler monitoring. During the laparoscopic procedure, ...

Hounds undergoing prolonged or complicated surgical procedures are often underventilated, as indicated by blood gas and end-tidal CO2 (CO2) values when using published ventilatory guidelines. We investigated the relationship between body weight, tidal volume, and inspiratory pressure delivered by the ventilator (lung inflation pressure) in 59 anesthetized hounds (19 to ...

BACKGROUND: Respiratory function and pulmonary gas exchange are affected in laparoscopic procedures where a pneumoperitoneum is introduced using CO2. Previous studies have shown differing results concerning pulmonary gas exchange during laparoscopic procedures: Whereas in patients undergoing isoflurane anaesthesia decreases in PaO2 are demonstrated, this factor remains unchanged in patients undergoing ...

BACKGROUND: The cardiopulmonary changes experienced by patients who undergo laparoscopic cholecystectomy (LC) and the prognostic value of patient characteristics are not well understood. METHODS: Cardiorespiratory changes were investigated in 120 patients undergoing LC or open cholecystectomy (OC). The results and their relation to patient variables were statistically evaluated. RESULTS: The ...

We have measured the performance of 10 trainee anaesthetists during a single simulated anaesthetic during which there was a complex critical incident. Errors in the recording on the anaesthetic charts of the "patient's" oxygen saturation, heart rate, systolic and diastolic arterial pressures and end-tidal carbon dioxide concentrations were used as ...

This study compares the hemodynamic response to panic disorder subjects with that of normal controls during respiratory challenges. Panic patients meeting DSM-IIIR criteria for panic disorder and normal controls were challenged with room air hyperventilation, 5% CO2 breathing, and 7% CO2 breathing. Measurements of pulse and blood pressure were taken ...

Tracheal and arterial CO2 partial pressures were measured simultaneously in 27 laryngectomized patients both while they were awake and during high-frequency jet ventilation. Tracheal gas was sampled during brief interruptions of high-frequency jet ventilation. Agreement between tracheal and arterial CO2 partial pressures was assessed using the Bland-Altman method. The tracheal-arterial ...