Ventilatory responses to acute and sustained hypoxia during sevoflurane anesthesia in women.

UNLABELLED: We investigated the isocapnic hypoxic (i.e., pulse oximetry monitored arterial saturations 70%-75%) ventilatory response (HVR) for 20 min in the awake state and during sevoflurane anesthesia at an end-tidal concentration of 1.6% in eight healthy (ASA physical status I) women. Our aims were to determine if a prolonged isocapnic hypoxic period during sevoflurane anesthesia showed a biphasic response pattern (i.e., an initial acute HVR followed by a decline to a lowered sustained HVR) and, if so, to quantify to what extent the acute and sustained HVRs were depressed by anesthesia. The study was conducted before laparoscopic gynecological surgery. Pneumotachography and in-line infrared capnography were used. The pattern of awake biphasic HVR was maintained during anesthesia but was depressed during both the acute and the sustained phases by 60% and 70%, respectively. Further, HVR during anesthesia was accomplished by an increase in respiratory rate, in contrast to an increase in tidal volume in the awake state. In conclusion, sevoflurane anesthesia at 1.6% depresses HVR in women, but the biphasic response is maintained. IMPLICATIONS: Acute and sustained hypoxic ventilatory responses were investigated in eight women before and during sevoflurane anesthesia. A biphasic ventilatory response was persistent but blunted during anesthesia.

Ventilatory responses to acute and sustained hypoxia during isoflurane anesthesia.

UNLABELLED: In the awake state, isocapnic hypoxic ventilatory responses (HVRs) are biphasic, with an acute response within 5 min of hypoxic stimulation followed by a less pronounced sustained response. In this study, we investigated the influence of isoflurane anesthesia (end-tidal concentration 1.1 kPa) on acute and sustained isocapnic HVRs in eight healthy women at pulse oximetry arterial saturations of 75%-80%. The aims were to determine whether HVR (20 min of hypoxia) during anesthesia was biphasic and to quantify ventilatory responses. Pneumotachography and in-line infrared capnometry were used. A biphasic HVR was found both in awake and anesthetized patients. Of the subjects, six had decreased and two had increased acute and sustained isocapnic HVRs in the anesthetized, compared with the awake state, which resulted in an approximately 50% reduction in both acute and sustained HVRs. In addition, the ventilatory response pattern was altered by anesthesia. Awake HVR was accomplished by increased tidal volumes while respiratory rates were unchanged. The opposite occurred during anesthesia. The underlying mechanisms for this biological action of inhaled anesthetics remains to be elucidated. In conclusion, this study clearly demonstrates the persistence of hypoxic ventilatory sensitivity during clinical anesthesia. IMPLICATIONS: We studied the ventilatory effects of 20 min of breathing air with low oxygen content (hypoxic) in eight women, before and during anesthesia with inhaled isoflurane. We demonstrated a persistent but blunted hypoxic ventilatory response during clinical anesthesia.

Isoflurane anaesthesia (0.6 MAC) and hypoxic ventilatory responses in humans.

In order to evaluate the difference between poikilo-capnic (no CO2 added to inspired gas) and iso-capnic (CO2 added to keep end-tidal CO2 constant) hypoxic ventilatory responses (HVR) awake and during 0.6 MAC isoflurane anaesthesia, seven cardio-pulmonary healthy patients were investigated. Pneumotachography and capnography were used before and during hypoxia (end-tidal O2 tension approx. 7 kPa). In the awake state, poikilo-capnic hypoxic challenges resulted in an increased HVR as indicated by a VE that on average increased by 1.4 +/- 1.0 (mean +/- s.d.) l.min-1, whereas the iso-capnic hypoxic challenges resulted in a VE increase that was 4.7 +/- 2.3 l.min-1 on average. In the anaesthetized state, the corresponding value during poikilocapnia was 1.3 +/- 0.8 l.min-1 (88% of the awake responses, n.s.) and during iso-capnia 2.3 +/- 1.4 l.min-1 (49% of the awake, P < 0.02). Awake HVR was achieved by greater tidal volumes during poikilocapnia as well as during isocapnic challenges, while respiratory rates were unchanged. In the anaesthetized state, during poikilocapnia, however, HVR was mediated by an increased respiratory rate, (from 17.5 +/- 1.7 breath.min-1 to 20.2 +/- 2.2) and during isocapnia by a combination of increased rate (from 17.1 +/- 1.9 breath.min-1 to 19.1 +/- 1.8) and tidal volume (from 496 +/- 80 to 560 +/- 83 ml). It is concluded that poikilocapnic HVR is maintained at 0.6 MAC isoflurane whereas iso-capnic HVR is depressed by 50%.(ABSTRACT TRUNCATED AT 250 WORDS)

Poikilocapnic hypoxic ventilatory response in humans during 0.85 MAC isoflurane anesthesia.

Ventilatory responses to hypoxia (HVR) were investigated using poikilocapnic conditions (i.e. end-tidal CO2's allowed to seek it's own level) in 15 cardio-pulmonary healthy patients who were first studied awake and then at 0.85 MAC isoflurane. The influence of hypercapnia (HyperCapnic Ventilatory Response, HCVR) was also elucidated. Pneumotachography, capnography and airway occlusion pressures at 0.1 s (P degree 0.1) were used before and during both mild hypoxia (end-tidal O2 tension 8.7 kPa) and hypercapnia achieved by an inspired CO2 concentration of 5%. HCVR was attenuated by 60% during anesthesia (P < 0.01). In the awake state, five of the 15 patients decreased HVR during hypoxia as compared with during normoxia. This resulted in a VE that on average increased by 0.6 l.min-1 (P < 0.05) whereas P degree 0.1 was unchanged. In the anesthetized state, no case of decreased HVR was seen and hypoxia induced a mean VE increase (+/- s.d.) by 1.0 +/- 0.2 l.min-1 (P < 0.001) and a P degree 0.1 that on average was improved by 0.63 +/- 0.27 cm H2O (P < 0.01). It is suggested that when the aim is to evaluate the influence of volatile anesthetic agents on HVR and to quantitate its clinical relevance during and immediately after anesthesia, a poikilocapnic technique should be used. It is concluded that the poikilocapnic HVR to PEO2's of 8.7 kPa was maintained during 0.85 MAC isoflurane.

A comparison of nutrient-based and exchange-group methods of diet instruction for patients with noninsulin-dependent diabetes.

This study compared effectiveness of nutrient-based (Diet Guide) vs food-group (Exchange Lists) methods of diabetic diet evaluation in improving dietary compliance, glycemic control, and biochemical indicators of heart disease risk. Eighty-three persons with noninsulin-dependent diabetes were taught one of two diet-planning methods in a 3-session workshop. Both methods led to reductions in energy intake and percent of calories from fat and saturated fatty acids in 6 mo postworkshop. Reductions in fat intake were greater and more long lasting for persons using Diet Guide than using Exchange Lists method of diet planning. Despite dietary changes, neither diet-planning method led to significant decreases in weight or skinfold thickness. Few differences were seen in clinical measurements pre- and 6 mo postworkshop. Total and LDL cholesterol values were lower than preworkshop values for men in both groups. Suggestions are given for improving effectiveness of both diet-planning methods.

Alternate lunch patterns in high schools. II. Student and foodstaff reactions.

Reactions to alternate menu patterns used in high school lunches were measured. Students rated food in Basic 4 and free-choice patterns more positively than Type A. The environment in the lunchroom was not rated differently with different menu patterns. Based on overall student reactions, the free-choice pattern was preferred. School lunch managers found the free-choice pattern more difficult to serve because of reimbursement and pricing problems but felt there was less plate waste and better student response with this system.