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Patients undergoing procedures under general anaesthesia as day cases are routinely given a set of instructions regarding activities to avoid in the first 24 h after discharge. Day surgery units generally specify the need for a responsible carer from time of discharge for a period of 24 h. This study looks at the compliance of 240 patients with postoperative instructions. Of the patients studied, 4.1% drove, 1.7% made important decisions, 3.3% drank alcohol, 0.8% took sedatives and 10% cooked, ironed or looked after children. All patients were discharged into the care of a responsible adult. However, 13.3% failed to have a carer with them for 24 h and 1.3% spent the night alone at home. Of our cohort, 25% were unable to comply with the postoperative instructions in full. The majority of non-compliance occurred on the day following surgery, suggesting that patients may feel that the advice is excessively cautious.

We have investigated the effect of four doses of remifentanil on the incidence of respiratory depression and somatic response at incision. Remifentanil was administered as a loading dose of 0.125, 0.25, 0.375 or 0.5 microgram kg-1 and at a maintenance infusion rate of 0.025, 0.05, 0.075 or 0.1 microgram kg-1 min-1, respectively, with an infusion of propofol 6 mg kg-1 h-1. Responses occurred in 88% of patients with remifentanil 0.025 microgram kg-1 min-1 compared with 30-40% in the other groups. Respiratory depression after incision increased from 6% with remifentanil 0.025 microgram kg-1 min-1 to 73% with 0.1 microgram kg-1 min-1. Increases in propofol infusion rate to 7.2-8.4 mg kg-1 h-1 produced adequate maintenance of anaesthesia. Reductions in remifentanil doses to 0.025-0.05 microgram kg-1 min-1 resulted in adequate respiration at the end of surgery in 88% of patients. Maintenance infusions of the two drugs for spontaneous ventilation are likely to be in these ranges. However, the ideal loading doses and infusion rates for induction remain to be established.

Binaural masked thresholds were measured for periodic 100‐μsec rectangular pulses of period T. Signal parameters were pulse rate (10, 50, 100, 250, and 1000 pps), interaural phase difference (0 and π rad), and interaural time difference (0–5 msec). Spectral content of the signal was controlled by addition or subtraction of phase‐locked harmonic components and by high‐pass and low pass filtering (cutoff frequencies 300, 600, 1200, and 2400 cps). Broad‐band, interaurally in‐phase, masking noise at 60 dB sensation level was used throughout. The signals were transduced by headphones, and the masked thresholds were determined by a modified Bekesy technique. The difference between the threshold for a given test condition and threshold for the signal in‐phase condition is defined as the masking‐level difference (MLD), or the binaural release from masking. For all pulse rates, maximum release from masking obtains for an interaural time of 1.5 msec or T/2, whichever is smaller. The greatest binaural unmasking occurs for a pulse rate of 250 pps and is less at higher and lower rates. For all tonal cases (pulse rates of 250 pps and higher) the release from masking is found to relate primarily to the fundamental component. Elimination of the fundamental substantially reduces the MLD. At the lowest pulse rate, high pass filtering of the signal also reduces the MLD to a small value. The largest MLD's are found for signal conditions that give rise to basilar‐membrane motion near the 300‐cps place and that lead to interaural time differences of about 1.5 msec in the neural activity originating from these places. The same interaural disparity at higher‐frequency places produces substantially smaller MLD's. The MLD therefore appears specific to membrane place as well as to interaural time difference.

Results from a computational model for middle ear and basilar‐membrane operation suggest several binaural phenomena. The effects are sought experimentally in tests on the binaural lateralization of pulses. The interaural times for producing centered images are measured as functions of pulse polarity and noise masking. To a large extent. the interaural disparities appear explicable in terms of the mechanical response of the basilar membrane together with simple hypotheses about the mechanical‐to‐neural transduction in the inner ear. The time disparity can be manipulated by symmetrically masking with high‐pass or low pass noise. By this means, the coherent neural information is elicited from a restricted place on the membrane and reflects the mechanical properties of that place. Similarly, asymmetrical masking (for example, high pass in one ear and low pass in the other) yields interaural times that reflect the transit times to specific membrane places. Calculations from the mathematical model for the middle ear and basilar membrane are used to interpret the psychoacoustic behavior in terms of physiological response. The results are discussed in the context of related findings, and an effort is made to assess the relative influence of mechanical and neural factors.

Preservation and usefulness of human gross temporal bones that have been dissected or drilled have always been a problem. This article describes application of the technique of plastination developed by von Hagens to the temporal bone. The use of this technique permits development of a collection of both anatomically dissected and surgically drilled temporal bones which can be studied by the otolaryngologist at any level. The procedure involves impregnation of the specimen with uncured polymers--a silicone rubber of medium viscosity followed by curing in a vapor bath. The advantages of this technique are that the plastinated temporal bone can be studied and handled without any unpleasant odor and there is no need for liquid preservation. The potential problem of the specimen drying out and becoming useless is thus avoided.

Subjects, listening with ear‐phones, adjusted the pitch of a uniform, periodic train of pulses to match the pitch of an experimental pulse pattern. One experimental pattern was periodic pulses with alternate amplitudes +a and +b. A second was similar but with alternate pulse amplitudes +a and −b. All pulse durations were 25 μsec. The parameters investigated, besides polarity pattern, were level difference ΔL=20 log |a/b| (0 to 20 db), and pulse rate (25 to 1074 pps). Results show that, roughly, for the (+a,+b) pattern a pulse‐rate match is made for a ΔL less than 6 db, regardless of pulse rate. For ΔL greater than 10 db, a match of one‐half pulse rate is made, also independent of pulse rate. For the (+a,−b) pattern, on the other hand, the pitch match is highly dependent both upon pulse rate and ΔL. As ΔL increases from 0 db, the match shifts away from the pulse rate at progressively lower frequencies. As in the first case, for ΔL>10 db, a pulse‐rate match is never made. The amplitude and phase spectra of ...

Brief pulses, delivered binaurally to listeners wearing earphones, produce a sound image centered in the head when the pulses are identical and simultaneous. Changing the polarity of one pulse (for example, from rarefaction to condensation) changes the relative times of occurrence that produce a centered image [J. Acoust. Soc. Am. 33, 840A (1961)]. This interaural disparity appears explicable in terms of the mechanical response of the basilar membrane and simple hypotheses about mechanical‐to‐neural transduction in the ear. Similarly, the disparity can be manipulated by symmetrical HP or LP masking noise. By this means, the coherent neural information is elicited from a specific place on the membrane, and reflects the mechanical properties of that place [J. Acoust. Soc. Am. 33, 1670A (1961)]. When the masking is made asymmetrical (for example, HP in one ear, LP in the other), the interaural times can be made also to reflect the transit times to specific points on the membrane. This paper presents data for...

Binaural‐masked thresholds were measured for periodic 100‐μsec rectangular pulses of period T. Signal parameters were pulse rate (10, 50, 100, 250, 1000 pps), interaural time difference (0–5 msec), and spectral content (as determined by high‐pass and low‐pass filtering at 0, 300, 600, 1200, and 2400 cps). Broad‐band, interaurally in‐phase masking noise at 60 dB SL was used throughout. The signals were transduced by headphones, and the thresholds were determined by a modified Bekesy technique. For all pulse rates, maximum release from masking obtains for an interaural time of about 1.5 msec or T/2, whichever is smaller. The greatest unmasking occurs for a pulse rate of 250 pps and is less at higher and lower rates. At the lowest pulse rate, severe high‐pass filtering of the signal abolishes the masking‐level difference, and severe low‐pass filtering enhances it. The results suggest that the greatest release from masking attaches to interaurally out‐of‐phase motion in the vicinity of the 300‐cps place on the basilar membrane.

At the last meeting of the Society [J. Acoust. Soc. Am. 33, 840(A) (1961)], we described an experiment to measure the interaural time difference for binaurally lateralizing cophasic (rarefaction‐rarefaction) pulses, and antiphasic (rarefaction‐condensation) pulses. High‐passed masking moise, with cutoff frequency fc, was used to cause the coherent neural information to originate in the apical half of the basilar membrane. The disparity in interaural times for lateralizing cophasic and antiphasic conditions was explicable in terms of (in fact, predicted by) the calculated displacements of the basilar membrane. Principal cophasic fusions of the sound image were made for zero interaural time. Principal antiphasic fusions, on the other hand, were made for a lead of the condensation pulse by a time approximately equal to 12fc sec. Using the procedure previously outlined, we have extended the experiment to the complementary situation where the significant neural information is constrained to originate from the ...