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Biomedical subjects

N Nandwani

Publications and source records attributed to N Nandwani.

12 recordsLinked to original sources
PubMed2000

Upper airway reflex sensitivity following general anaesthesia for day-case surgery.

We have studied changes in upper airway reflex sensitivity following general anaesthesia using dilute ammonia vapour as a chemical stimulant in 16 patients undergoing elective laparoscopic gynaecological surgery. We measured the threshold concentration of ammonia vapour required to elicit a transient reduction of inspiratory flow caused by glottic closure, defined as a glottic stop. Measurements of upper airway reflex sensitivity and auditory reaction time were obtained before surgery, and at 60 and 120 min after recovery. Auditory reaction time was depressed significantly at 60 min but was similar to baseline values 120 min after recovery. Upper airway reflex sensitivity remained significantly reduced at 60 and 120 min despite the return of auditory reaction time to normal. The lack of correlation between upper airway reflex sensitivity and auditory reaction time suggests that central nervous system depression alone does not explain the delayed recovery in airway reactivity.

Acoustic Stimulation↗
PubMed1999

Upper airway reactivity and upper respiratory tract infection: effect of nebulized lidocaine.

Patients presenting for elective anaesthesia and surgery may be suffering with, or recovering from, a recent upper respiratory tract infection. Airway reflexes are heightened and these individuals may be more likely to suffer airway complications on administration of general anaesthesia. We have examined the effect of nebulized lidocaine on upper airway reflexes in such subjects. Using dilute ammonia as a chemical stimulus to the upper airway, we measured upper airway reactivity in 15 volunteers (aged 22-43 yr) with symptoms of an upper respiratory tract infection for 4 days or less. The threshold concentration of ammonia producing a brief reduction in inspiratory flow was determined. Measurements were made before and after administration of a nebulized solution of 4% lidocaine 4 ml or saline. After a 2-h interval the procedure was repeated with the alternative solution. The order of administration was randomized. The observer was blind to the solution given. Ammonia threshold was found to increase in subjects after nebulized lidocaine, from a median value of 327 (range 76-878) ppm to 878 (251-1620) ppm (P = 0.0007, Wilcoxon); there was no significant change after nebulized saline. After a convalescence period of at least 4 weeks, with no return of symptoms in the preceding 2 weeks, ammonia threshold was reassessed. It was found to be increased in all 15 subjects. Comparison of the five different times of measurement showed a highly significant difference (P < 0.001, Friedman). Subsequent analysis showed significant differences (P < 0.05, Wilcoxon) between convalescent ammonia threshold and both baseline and post-saline nebulizer values. There was no significant difference between convalescent and post-lidocaine ammonia threshold. We conclude that in adult subjects, nebulized lidocaine attenuated the heightened airway reflex sensitivity associated with symptoms and signs of upper respiratory tract infection.

Adult↗
PubMed1998

Retrosternal goitre: a cause of dyspnoea in pregnancy.

During pregnancy, the thyroid undergoes several changes including altered function and gland enlargement. We describe the management of a 38-week pregnant woman presenting with cough and increasing breathlessness. She gave a 5-year history of asthma which initially obscured the final diagnosis of upper-airway obstruction secondary to tracheal compression by a large retrosternal goitre. Once this was recognized, management was straightforward. Delivery by caesarean section was carried out under epidural anaesthesia, following which her symptoms rapidly resolved. A subtotal thyroidectomy was performed 4 weeks later under general anaesthesia, again without incident. We outline the normal physiological changes that occur to the thyroid gland during pregnancy and also highlight the value of the flow volume loop in the evaluation of airway obstruction.

Journal Article↗
PubMed1998

Obstructive sleep apnoea and upper airway reactivity.

Upper airway reactivity was measured in 13 patients with obstructive sleep apnoea (OSA), using transient reflex laryngeal closure in response to dilute inhaled ammonia vapour. Upper airway reactivity was measured before and after 3 months of treatment with nasal continuous positive airway pressure (CPAP). Upper airway reactivity decreased significantly after treatment with nasal CPAP to values which were similar to those seen in normal subjects. We hypothesise that patients with OSA have increased upper airway reactivity, secondary to inflammation of the epithelial lining of the upper airway following the repeated injury of nocturnal airway obstruction, allowing the facilitated passage of inhaled irritants to the subepithelial receptors. Treatment of OSA with nasal CPAP may reverse these changes, although in the absence of a control group, these findings are provisional.

Adult↗
PubMed1997

Effect of an upper respiratory tract infection on upper airway reactivity.

Patients presenting for elective anaesthesia and surgery may be suffering with, or recovering from, a recent upper respiratory tract infection (URTI). It is a frequent clinical problem as to whether to postpone surgery in such patients as they may be more likely to suffer adverse respiratory events related to administration of general anaesthesia. Using dilute ammonia vapour as a chemical stimulus, we measured upper airway reactivity in 11 healthy volunteers (six males), mean age 39.8 (range 30-58) yr, who had symptoms of an URTI. Volunteers were recruited 24-72 h after symptoms first began, and followed-up at regular intervals for the next 8 weeks. Measurements of upper airway reactivity were made on the following days (+/- 24h) after commencement of URTI symptoms: 3, 6, 9, 15, 20 and 27. Additional measurements were obtained 56 days after symptoms first began, and these were regarded as baseline measurements. Upper airway reactivity was increased on days 3, 6 and 9 compared with baseline measurements (P < 0.01, Wilcoxon). There was no significant change in airway reactivity from day 15 onwards, by which time 10 of the 11 subjects were completely devoid of symptoms. All subjects were asymptomatic by day 20 and remained so until the study ended on day 56. We conclude that upper airway reactivity was increased during the acute phase of an URTI, and that this appeared to be related to the presence of symptoms.

Acute Disease↗
PubMed1997

The effect of laryngeal mask airway insertion on the position of the internal jugular vein.

A high-quality ultrasound system (Dyasonics Prisma) was used to study the effect of laryngeal mask airway insertion and cuff inflation on the position and relations of the internal jugular vein in eight healthy young patients undergoing elective surgery. On insertion of the laryngeal mask, with the cuff pre-inflated with 10 ml of air, some minor movement was discernible in the larynx. Neither the larynx nor surrounding structures changed significantly in position. However, on full inflation of the laryngeal mask cuff there was a more noticeable movement of the larynx, which visibly distended in an anterior direction. The mean anterior displacement was 0.8 cm (range 0.6-1.1 cm). There was no significant lateral displacement of the carotid artery or internal jugular vein and there was no significant compression of these structures. We conclude that in the presence of a laryngeal mask airway fixed landmarks such as the sternal notch and angle of the jaw should be used to identify the likely position of the internal jugular vein. Difficulty in cannulation may be experienced if the mobile laryngeal structures are used as landmarks.

Adolescent↗
PubMed1997

Effect of nebulised lignocaine on the quality of induction of anaesthesia in cigarette smokers.

We have assessed the effect of nebulised lignocaine, given pre-operatively, upon the quality of induction of anaesthesia in cigarette smokers. Seventy-five patients were studied in a double-blind randomised fashion, receiving a nebuliser of either 4 ml 0.9% NaCl or 4 ml 4% lignocaine. All patients received a standardised anaesthetic consisting of thiopentone followed by progressive increments of enflurane. Thirty-three out of 38 patients (87%) who received nebulised lignocaine had induction without adverse events, compared with 25 out of 37 patients (68%) in the nebulised saline group (Chi-squared test p < 0.05). We conclude that the use of nebulised lignocaine, administered pre-operatively, improves the quality of induction of anaesthesia in cigarette smokers.

Administration, Inhalation↗
PubMed1996

Configuration of the SCOTI device with different tracheal tubes.

We have evaluated the Sonomatic Confirmation of Tracheal Intubation device (SCOTI) by testing its ability to be correctly configured with a variety of tracheal tubes of differing internal diameter and length. The device only configured correctly for RAE tubes with internal diameter of 7.0 mm or greater and for armoured tubes of internal diameter 8.5 mm. For conventional tubes of varying internal diameter cut to different lengths, configuration was only successful with certain dimensions. The inability to configure the device correctly with all types and lengths of tracheal tubes limits its usefulness as a indicator of tracheal intubation.

Calibration↗