[Surgery in the Ancient Egypt].
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Egypt, Ancient↗
Biomedical subjects
J F Nunn
Publications and source records attributed to J F Nunn.
Estimation of tidal volume from the reservoir bag. A laboratory study.
The accuracy of 21 anaesthetists in estimating tidal volumes from reservoir bag movements was assessed using a model lung apparatus. The breathing system configuration (Mapleson A or D), the grade of anaesthetist, and the years of anaesthetic experience had no effect on accuracy. Greater precision of tidal volume estimation was observed with larger tidal volumes and lower fresh gas flows. The mean systematic error of 18 of the 21 anaesthetists was greater than zero, indicating a general tendency to overestimate tidal volume. This study therefore strengthens the view that clinical observations should be supplemented with information from continuous monitoring devices.
Anesthesia, Inhalation↗
Ribcage contribution to CO2 response during rebreathing and steady state methods.
Disagreements exist between previous studies of the contribution of the rib cage (RC) and abdomen-diaphragm (AD) components to CO2-stimulated ventilation. These studies used dissimilar techniques of CO2 stimulation and varying methods of data processing and presentation, thus precluding direct comparisons. We have therefore studied two methods of CO2 stimulation in 12 subjects, using a Read's rebreathing method and a modified steady-state technique. Respiratory inductive plethysmography was used to assess the RC and AD contributions to ventilation. Mean slopes for the ventilatory response to CO2 were the same for both methods (mean 2.56 L.min-1.mmHg-1), and the intercepts were significantly different (43.7 mmHg for rebreathing and 38.0 for modified steady state: P less than 0.001). There was a small, but significant, increase in the percentage RC contribution to ventilation during hypercapnia of 0.97%/mmHg PCO2 for rebreathing and 0.62 for steady state (P less than 0.01 and P less than 0.05, respectively), and these values were not significantly different from each other. Using our data in comparison with other studies, we have been able to show that differences in processing and presentation of data have given rise to wide variations in conclusions.
Adult↗
Effect of general anaesthesia on the pharynx.
Conventional lateral radiography was used in 18 elderly male patients to investigate the changes induced by general anaesthesia in the upper airway. The effect of tongue traction under anaesthesia was studied similarly in another 11 patients. Following induction of anaesthesia, there were highly significant approximations to the posterior pharyngeal wall of the soft palate (median change 1.3 mm, 95% confidence interval (Cl) 0.3-2.6 mm; P = 0.006), tongue base (mean change 6.5 mm, 95% Cl 5.3-7.7 mm; P less than 0.001) and epiglottis (mean change 3.8 mm, 95% Cl 3.1-4.5 mm; P less than 0.001). Apparent radiographic occlusion of the airway occurred most consistently at the level of the soft palate (17 of 18 patients), sometimes at the level of the epiglottis (four patients), but the tongue base did not touch the posterior pharyngeal wall in any patient. Traction on the tongue failed to clear the nasopharyngeal obstruction. Attempted inspiration under anaesthesia caused major secondary collapse of the pharynx, with multiple sites of obstruction, similar to that found in obstructive sleep apnoea.
Aged↗
An early marker of hyperoxic lung injury in the rat and its pharmacological modulation.
Of three possible early biochemical changes which were investigated in rats after hyperoxia, one was shown to be a useful marker of damage in this species. Mitochondrial oxygen uptake measured in lung homogenates has already been reported to be impaired after 24 h. With a purified mitochondrial fraction, we found significant impairment after only 3 h exposure to 100% oxygen. To our knowledge, this is the earliest significant change reported in this species. The antioxidants N-acetyl cysteine, dimethyl sulphoxide and allopurinol were found to ameliorate the injury. This suggests a possible link with the pulmonary damage and survival of rats in hyperoxia, which may be modulated also by antioxidant therapy.
Allopurinol↗
Airway obstruction associated with the use of the Guedel airway.
Soft tissue lateral neck radiography was used in 22 male patients older than 60 yr, to determine the cause of pharyngeal airway obstruction during anaesthesia, before and after insertion of a Guedel airway. In six of the patients, the airway was radiologically and clinically clear with the head in the neutral position. Nine patients showed obstruction of the airway by a "shelf" of tongue, but seven were cleared clinically by dorsiflexion at the atlanto-occipital joint, and the remaining two by the Esmarch-Heiberg manoeuvre. In four of the 22 patients, the Guedel airway was lodged in the vallecula in the neutral position. This was cleared clinically by dorsiflexion at the atlanto-occipital joint in all these patients. In three patients the Guedel airway was obstructed by the epiglottis, but this was cleared by dorsiflexion at the atlanto-occipital joint in two; in the third patient, the Guedel airway slipped into the vallecula after dorsiflexion at the atlanto-occipital joint and remained there despite the Esmarch-Heiberg manoeuvre. There was only one instance in 66 trials of a clinically obstructed airway without an apparent radiological cause. However, there were 10 instances in 66 trials of a clinically clear airway with an apparent radiological cause for obstruction.
Aged↗
Rib cage contribution to resting and carbon dioxide stimulated ventilation during 1 MAC isoflurane anaesthesia.
Using respiratory inductive plethysmography, we have measured rib cage and abdominal motion during isoflurane anaesthesia in 16 healthy day-surgery patients. Anaesthesia was induced with propofol and maintained with 1 MAC isoflurane in air-oxygen via a laryngeal mask. Measurements were taken during both resting ventilation and hyperpnoea induced by rebreathing carbon dioxide. For resting ventilation, the rib cage contributed a mean (SD) of 33 (15)% of the total ventilation whilst awake, and 39 (12)% during anaesthesia (ns). With increasing end-tidal carbon dioxide whilst awake, the subjects showed a mean increase in the percentage rib cage contribution of 7.1 (12.5)%/kPa of carbon dioxide. With isoflurane anaesthesia, there was significant depression of this rib cage recruitment with the mean contribution decreasing by 3.6 (7.4)% kPa-1 (P less than 0.05). These results indicate that 1 MAC of isoflurane does not selectively depress rib cage motion, except during carbon dioxide stimulated hyperpnoea.
Abdominal Muscles↗
Comparison of oxygen consumption measurements: indirect calorimetry versus the reversed Fick method.
OBJECTIVE: To compare measurement of oxygen consumption (VO2) by spirometry and the reversed Fick method. DESIGN: Within-patient comparison using simultaneous measurements by the two methods, one previously calibrated on a metabolic simulator. PATIENTS: Twenty sets of observations on eight patients (57 to 83 yrs) requiring mechanical ventilation in a critical care unit. INTERVENTIONS: None during or immediately before the measurements. MEASUREMENTS AND MAIN RESULTS: Duplicate pairs of measurements of VO2 were made with a previously validated spirometric technique and the reversed Fick method (Qt[CaO2 - CVO2]), where Qt is cardiac output, CaO2 is arterial oxygen content, and CVO2 is mixed venous oxygen content. The coefficient of variation of the difference between duplicate measurements by the former technique was only 2.53% compared with 10.4% for the latter. The mean VO2 measurement by the spirometric method was 285.7 +/- 40.7 (SD) mL/min standard temperature and pressure, dry (STPD) and for the reversed Fick method, the mean VO2 measurement was 249.3 +/- 38.5 mL/min STPD. The mean difference was 36.4 +/- 28.5 mL/min STPD (p less than .001). CONCLUSIONS: The repeatability of the spirometric method was four times better than the reversed Fick method. The latter gave a significantly lower value that probably, in part, reflects the VO2 of the lung, which is included in the spirometric method but not in the reversed Fick measurement.
Aged↗
Respiratory function and ribcage contribution to ventilation in body positions commonly used during anesthesia.
Lung function tests are normally performed in the upright position, whereas anesthesia is usually administered with the patient in the supine position, and occasionally in other postures. We therefore compared forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), functional residual capacity (FRC), and ribcage contribution to ventilation by respiratory inductive plethysmography in 13 conscious healthy male volunteers, sitting and in four horizontal positions used during anesthesia. Forced vital capacity and FEV1 were similar in all positions, except for a significant mean increase in FVC of 300 mL (SD 213) when sitting compared with when supine (P less than 0.001). The mean decrease in FRC was 806 mL (SD 293) between the sitting and supine positions (P less than 0.001). A significant increase in FRC occurred (252 mL, SD 329, P less than 0.01) when supine subjects raised their arms above their heads as required for computed tomography. Functional residual capacity in the prone and lateral positions was significantly larger than in the supine position (mean change 350 mL, P less than 0.001), but was still some 450 mL less than in the sitting position. Mean ribcage contribution was similar in all horizontal positions (32%-36%), whereas supine values were significantly different from those of the sitting position (mean 70%, SD 11, P less than 0.001). In conclusion, the various horizontal postures studied have no effect on FVC, FEV1, or ribcage contribution to ventilation. However, FRC in the prone, lateral, and arms-up positions is on average 250 mL larger than in the supine position, an observation that may affect gas exchange during anesthesia in these positions.
Adult↗
Radiological study of the Laryngeal Mask.
Lateral soft-tissue radiography was used to determine the location of the Laryngeal Mask (LM) in relation to the larynx and surrounding structures in 24 elderly male patients undergoing general anaesthesia. In a majority of cases (16 of 24) the epiglottis was within the cuff of the mask but without causing discernable airway obstruction in any case. One case of backfolding of the cuff occurred, and there was one case of gross misplacement (also clinically undetected). Supplementary information was obtained in 13 patients by the use of fibre-optic endoscopy, via the lumen of the LM, confirming the inclusion of the epiglottis within the mask and demonstrating a characteristic distortion by the LM of the normal laryngeal anatomy. It is concluded that inclusion of the epiglottis within the LM is commonplace, and misplacements may occur without clinical evidence of a compromised airway.
Anesthesiology↗
Effects of anaesthesia on respiration.
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Anesthesia, General↗
Carbon dioxide cylinders on anaesthetic apparatus.
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Anesthesiology↗
Evaluation of metabolic measuring instruments for use in critically ill patients.
We evaluated three commercial indirect calorimetry devices which are used during artificial ventilation. Commercial butane, which had an RQ of 0.615, consumes 6.40 ml oxygen, and produces 3.94 ml CO2/1 ml, was burned in a gas-tight combustion chamber in conjunction with the ventilation of a lung model. During combustion, the flow rate of butane was measured with a soapfilm flowmeter for the calculation of reference values of oxygen consumption (VO2) and CO2 production (VCO2). To investigate the effect of oxygen concentration on the accuracy of these instruments, measurements were carried out at FIO2 values of 0.3, 0.4, 0.5, and 0.6 with a fixed ventilation mode (tidal volume 500 ml; respiratory rate 16 breath/min, intermittent positive-pressure ventilation). For the Datex Deltratrac Metabolic Monitor, the mean relative errors of measured VO2, VCO2, and RQ were all within 4.0%, 2.9%, and 4.0%, respectively. For the Engstrom Metabolic Computer, the corresponding values were 1.4%, 5.7%, and 6.0%, and for the SensorMedics MMC Horizon, 5.7%, 2.9%, and 5.9%.
Calorimetry↗
Time course of changes in lung permeability and edema in the rat exposed to 100% oxygen.
Rats were exposed to 100% oxygen for up to 60 h to determine early changes in lung permeability leading to the development of pulmonary edema. The time course of development of increased solute flux was assessed by the clearance of 99mTc-labeled diethylenetriamine pentaacetate (99mTc-DTPA) from the lung and the accumulation of 125I-labeled albumin (125I-albumin) in the lung. These end points were related to the development of pulmonary edema by the measurement of the wet-to-dry weight ratio of the lung and the weight of fluid in the pleural cavity. No significant changes occurred until 48 h of hyperoxia, when sharp increases in both indexes of lung permeability and wet-to-dry weight ratio occurred. By 60 h of exposure, pleural effusions had developed. The volume of this effusion was significantly correlated to both 99mTc-DTPA clearance and 125I-albumin flux.
Albumins↗
Henrik Enghoff and the volumen inefficax.
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Carbon Dioxide↗
Survival of patients ventilated in an intensive therapy unit.
The survival of patients who were artificially ventilated in an intensive therapy unit (ITU) of a district general hospital was studied. The first 100 such patients admitted were followed up for at least four years. Of these, 67 survived treatment in the ITU, 47 were discharged from hospital, and 30 survived four years. (Survival in the ITU of patients who did not require ventilation was 89%.) The effects of age, duration of ventilation, and disease were studied, and a higher survival was found in children, in patients ventilated for under 24 hours, and in patients admitted with drug overdosage. Survival was poor in patients aged over 75 and in those who required ventilation after cardiac arrest or myocardial infarction or for chronic obstructive lung disease. The cost of a bed in an ITUs to be used to the greatest effect it is important to define those patients who are most likely to benefit from the facilities they offer.
Adolescent↗
Halothane does not inhibit human neutrophil function in vitro.
Various indices of function of neutrophils from normal healthy volunteers have been examined after in vitro exposure to halothane. Random free movement on glass was unaffected, but random migration through millipore filters was slightly increased. There was no significant change in migration in response to casein chemotaxis. Phagocytosis, degranulation and the enhanced non-mitochondrial respiration associated with phagocytosis were unaffected. Electron-microscopic appearance at 30 s after exposure to latex particles was normal in all respects.
Cell Movement↗