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Biomedical subjects

S B Bhatt

Publications and source records attributed to S B Bhatt.

15 recordsLinked to original sources
PubMed1998

Carbon dioxide dynamics during apneic oxygenation: the effects of preceding hypocapnia.

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, and III patients requiring general endotracheal anesthesia and invasive monitoring for elective surgery. INTERVENTIONS: Two ventilatory states preceding apneic oxygenation were studied in each patient. The first respiratory state was established using controlled mechanical ventilation in the stable, anesthetized patient, followed by a 5-minute period of apneic oxygenation. Arterial and mixed central venous blood gas samples were obtained simultaneously prior to and at 1-minute intervals during apnea. Ventilatory parameters were then changed to establish the second respiratory state. During the subsequent period of apnea, the study was repeated as above. MEASUREMENTS AND MAIN RESULTS: Arterial and mixed central venous partial pressure of carbon dioxide (pCO2) levels were measured. A greater increase in PaCO2 was found during the first minute of apneic oxygenation in the hypocapneic group compared with the eucapneic group. The venoarterial gradient of pCO2 was also greater in the hypocapneic group prior to apnea. CONCLUSIONS: Acute hypocapnia compared with eucapnia prior to apneic oxygenation is associated with a greater rise in PaCO2 in the anesthetized patient. This finding may be due in part to widening of the venoarterial gradient of pCO2.

Adult↗
PubMed1995

Superimposed inspiratory work of the Siemens Servo 300 ventilator during continuous positive airway pressure.

OBJECTIVE: To compare the superimposed inspired work of breathing (SIW) of the Siemens Servo 300 ventilator with the Siemens Servo 900 C ventilator. DESIGN: Comparisons made at continuous positive airway pressure (CPAP) levels of 0, 4, and 8 cmH2O, and at trigger sensitivities of -1 and -2 cmH2O, and flow triggering. SETTING: General intensive care unit in a University teaching hospital. PATIENTS: 7 patients receiving CPAP. At all levels of CPAP, the SIW was significantly less with the Siemens Servo 300 ventilator as compared to the Siemens Servo 900 C ventilator despite similar trigger sensitivities. No significant difference was found in the SIW of the Servo 300 ventilator when comparing trigger sensitivities of -1 cmH2O, -2 cmH2O, and flow triggering. Different levels of CPAP had no effect on SIW. CONCLUSIONS: The Siemens Servo 300 ventilator entails less superimposed inspiratory work of breathing than the Siemens Servo 900 C ventilator.

Adult↗
PubMed1995

Pressure support ventilation during isoflurane anaesthesia.

We have studied the respiratory effects of 5 and 10 cmH2O pressure support ventilation during anaesthesia with 1.5% end-tidal concentration of isoflurane in nine healthy, spontaneously breathing, adult patients. Some of the patients demonstrated an irregular respiratory pattern with periods of apnoea and we therefore went on to study a further seven patients with a continuous 500 s recording of airflow. Pressure support ventilation augmented mean (SD) tidal volume from 212 (56) ml to 360 (88) ml at 5 cmH2O and to 509 (108) ml at 10 cmH2O (n = 16, p < 0.05). Mean (SD) respiratory rate decreased from 26 (6) min-1 to 22 (6) min-1 at 5 cmH2O and 17 (5) min-1 at 10 cmH2O pressure support (n = 16, p < 0.05). Mean (SD) inspiratory work of breathing decreased from 1.77 (0.70) J. min-1 to 0.31 (0.36) J.min-1 at 5 cmH2O and 0.16 (0.26) J.min-1 at 10 cmH2O pressure support ventilation (n = 9, p < 0.05). Analysis of the respiratory rhythm in the second group of seven patients revealed an oscillating respiratory pattern in four patients at 5 cmH2O and six of the seven patients at 10 cmH2O pressure support ventilation. The metabolic advantage of the decreased work of breathing during pressure support ventilation during anaesthesia is unlikely to balance the disadvantage of an oscillating respiratory rhythm.

Adolescent↗
PubMed1993

Effects of PEEP on dynamic hyperinflation in patients with airflow limitation.

We have studied the effects of extrinsically applied PEEP (PEEPe) and intrinsic PEEP (PEEPi) on lung volume and peak airway pressure (Paw,peak) in 10 patients with airflow limitation during mechanical ventilation. PEEPe was applied in 2-4 cm H2O increments until values greater than PEEPi were reached. Total lung hyperinflation was quantified by measuring the expired volume resulting from deflation (starting at end inspiration) until cessation of expiratory flow. The previous expired tidal volume was subtracted from this volume to obtain the change in functional residual capacity (delta FRC), the hyperinflation resulting from PEEPi and PEEPe. PEEPi (0.49-1.66 kPa) was demonstrated in all patients before the application of PEEPe and correlated with delta FRC (r = 0.71), with delta FRC increasing by 582 ml/kPa PEEPi (P < 0.05). PEEPe at pressures less than PEEPi increased delta FRC by (mean) 186 (SEM) 34 ml/kPa PEEPe (P < 0.05) and increased Paw,peak by 0.6 (0.12) kPa/kPa PEEPe (P < 0.05). In contrast, PEEPe at pressures greater than PEEPi, increased delta FRC by 695 (128) ml/kPa PEEPe (P < 0.05) and Paw,peak by 1.8 (0.26) kPa/kPa PEEPe. We conclude that PEEPe may be applied cautiously at values less than PEEPi when clinically indicated, but the application of PEEPe at values greater than PEEPi may substantially aggravate lung hyperinflation.

Aged↗
PubMed1993

The minilink breathing system: resistance and suitability for spontaneous ventilation.

The Portex infant breathing/ventilation systems with 8.5 mm and 15 mm internal diameter connectors were compared with a standard T-piece which had a 15 mm connector and 22 mm internal diameter tubing. The differential pressures across each system were measured at constant fresh gas flows up to 30 l.min-1 dry air. Resistance was calculated at flows compatible with quiet respiration and peak inspiratory flow. Flow resistance of the 3.0 mm internal diameter tracheal tube in conjunction with the minilink breathing systems were similar to those previously reported for tracheal tubes alone. However, the minilink breathing system assumed a greater influence on resistance when tracheal tubes of larger internal diameter were used. It added considerably more resistance than the standard tubing. This may have a deleterious effect during spontaneous ventilation in older children.

Airway Resistance↗
PubMed1992

Effect of dobutamine on oxygen supply and uptake in healthy volunteers.

We have measured the changes in VO2 and the VO2:DO2 relationship during infusion of dobutamine in healthy volunteers. Nine healthy, adult, non-obese, male physicians were infused with an incremental infusion of dobutamine starting at 2.5 micrograms kg-1 min-1 increasing to 5.0 and then 7.5 micrograms kg-1 min-1 for 15 min each. VO2 and cardiac index were measured every five minutes. VO2I (VO2m-2) increased from a baseline of 128 (SEM 6.1) ml min-1 m-2 to 159 (8.0) ml min1 m-2 (P < 0.05) at the end of infusion with 7.5 micrograms kg-1 min-1. The corresponding changes for DO2I (DO2 m-2) were from 643 (35) ml min-1 m-2 to 1240 (142) ml min-1 m-2 (P < 0.05). The coefficient of correlation for pairs of VO2 and DO2 values, at baseline and each dobutamine infusion in individual subjects, ranged from 0.89 to 0.99 (mean 0.95, SD 0.03). Dobutamine has potent calorigenic effects; demonstration of a positive correlation between VO2 and DO2 after infusion of dobutamine does not necessarily imply an underlying tissue oxygen debt.

Adult↗
PubMed1992

Resistance and additional inspiratory work imposed by the laryngeal mask airway. A comparison with tracheal tubes.

Laryngeal mask airways and tracheal tubes were studied to determine both their resistance to constant gas flows and additional inspiratory work during simulated inspiration. Laryngeal mask airways imposed less resistance and required lower additional inspiratory work compared with the corresponding sized tracheal tubes. If inspiratory loading during anaesthesia is an important consideration, then the laryngeal mask airway may be preferable to a tracheal tube.

Airway Resistance↗
PubMed1990

Potassium homeostasis during & after cardiopulmonary bypass.

Potassium homeostasis was studied in 30 patients undergoing cardiac surgery by employing cardiopulmonary bypass (CPB) and moderate hypothermia, and using morphine, N2O, relaxant anaesthesia. There was a trend for hypokalemia, and for maintaining a K+ level of 4-4.5 mmol/l, K+ infusion was required during CPB (9.017 mmol/m2 BSA/h). K+ infusion required in the post-operative period was considerably less (1.532 mmol/m2 BSA/h). There was no significant difference in the K+ levels of patients receiving preoperative diuretic therapy, as compared to those not receiving such therapy. Potassium requirement was significantly higher in patients under-going CABG and valvular heart disease, as compared to congenital heart disease. The mean urinary loss of K+ during bypass was found to be 2.95 mmol/m2 BSA/h, which was only 32 per cent of that required to be infused (9.017 mmol/m2 BSA/h). The mean excretion of K+ in the post operative period was significantly higher (4.53 mmol/m2 BSA/h) than K+ required to be infused during this period (1.532 mmol/m2 BSA/h).

Cardiopulmonary Bypass↗