Advanced practice roles for nurses in tomorrow's healthcare systems.

Advanced practice nurses (APNs) have traditionally been a diverse group in terms of titles, education, credentials, and roles. The classification of APN usually encompasses the nurse practitioner (NP), certified nurse midwife (CNM), certified registered nurse anesthetist (CRNA), and clinical nurse specialist (CNS). NP, CRNA, and CNM roles have been more clearly delineated than the CNS roles. In light of healthcare reform, the CNS roles have been critically reviewed and analyzed. Attempts have been made to clarify responsibilities and outcomes, and to quantify the financial impact of this role. In this article, seven APN roles clearly defined in terms of minimal qualifications and competencies critical to accomplishment of the duties, responsibilities, and expected outcomes are presented. Comparison of competency requirements are also presented. The roles presented are designed to facilitate healthcare institutions in meeting the demands for serving patients with increasingly complex needs, as well as cost-containment goals.

Nonhypersomnolent patients with obstructive sleep apnea.

Until recently, snoring had been considered both a medical enigma and a psychosocial problem. Snoring is now considered to be an acoustic phenomenon produced by vibration of the soft palate and the tonsillar pillars. We describe 20 patients with a clinical complaint of excessive snoring who were referred to rule out obstructive sleep apnea. All patients were without symptoms of daytime sleepiness and failure of the right heart. Twenty subjects were studied, 18 of whom were males. All subjects were monitored for one full night in the Sleep Laboratory. The apnea rate ranged from 9.0 to 94.0 incidents an hour with a mean of 30.0. Eight of the 20 subjects had obstructive episodes longer than 1 minute and three others had episodes longer than 55 seconds. Hypersomnolence, long thought to be a cardinal symptom, is not present in all patients with an ostensibly significant degree of obstructive sleep apnea.

Fatigue of inspiratory muscles and their synergic behavior.

The time (tlim) required to produce inspiratory muscle fatigue was measured in five normal subjects breathing at functional residual capacity (FRC) against a variety of high inspiratory resistive loads. In every breathing test the subjects generated with each inspiration a mouth pressure (Pm) that was a predetermined fraction of maximum Pm (Pmmax). They continued breathing until they were unable to generate this Pm. The Pm/Pmmax that could be generated indefinitely (Pmcrit) was around 60%. The inspiratory power output at that level of breathing was 6.6 kg.m/min (Wcrit). In three of those subjects the same experiment was conducted at an end-expiratory volume of FRC + one-half inspiratory capacity (1/2IC). The higher lung volume was actively maintained by the subjects watching end-expiratory transpulmonary pressure on an oscilloscope. For any fraction of the maximum mouth pressure at FRC + 1/2IC (Pm'max), tlim was shorter than FRC. Pmcrit decreased to 30% Pm'max and Wcrit to 2.6 kg.m/min. Monitoring the abdominal pressure revealed that the contribution of the diaphragm and intercostal accessory muscles alternated in time, possibly postponing the onset of fatigue.

Flow dependence of gas distribution and the pattern of inspiratory muscle contraction.

We measured regional distribution of xenon-133 boli at 0.25, 0.75, and 1.5 l/s in four normal seated subjects during inspirations performed predominantly with intercostal and accessory muscles (IC) or with the diaphragm, accompanied by outward abdominal motion (Ab). In six additional subjects we inferred the topographical distribution of helium boli during similar breaths and flow rates from the slope of the alveolar plateau recorded during a slow expiration (less than 0.5 l/s). Distribution of the helium boli was studied during natural as well as IC and Ab inspirations. At each of the flow rates IC breaths distributed relatively more of the inspired bolus to upper lung regions than did Ab inspirations. Natural breaths at 0.25 l/s resulted in distributions similar to those of Ab inspirations, whereas at 1.5 l/s the distribution approached that of IC inspirations. A three-compartment model, representing upper, middle, and lower lung regions, was used to simulate bolus distribution. The experimental data showed substantial departure from predictions based on regional time constants alone. However, additional small differences in applied pressure (less than 0.50 cmH2O) between the regions satisfactorily accounted for the gas distribution.

Theophylline bioavailability following chronic dosing of an elixir and two solid dosage forms.

Theophylline bioavailability following chronic dosing of an elixir and two commercial tablet formulations (I and II) relative to an acute dose of elixir was evaluated in healthy volunteers. Both tablet formulations contained ephedrine. In addition, Tablet I contained hydroxyzine hydrochloride, and Tablet II contained phenobarbital. The mean area under the serum concentration-time curve (AUC) calculated either from time 0 leads to infinity for a single dose or over one dosing interval after repetitive doses was the highest after chronic administration of the elixir. The AUC after chronic elixir, in fact, was statistically different from the values after acute elixir (p less than 0.05) and Tablet II (p less than 0.05). There was, however, a large variation in the elimination half-life among the four theophylline treatments. The mean t 1/2 was the longest after chronic elixir followed by Tablet I, Tablet II, and acute elixir. The AUC values for the four treatments, when corrected for differences in t 1/2, were no longer significantly different, indicating that the extent of theophylline absorption was essentially the same from all three tested products. The time to peak and the peak serum concentration also did not differ among treatments. The prolongation in t 1/2 following chronic treatment with the elixir and its subsequent shortening during tablet administration suggest an initial inhibition followed by induction of theophylline metabolism. The changes may be due to the prolonged treatment with theophylline itself or the other drug ingredients in the dosage form.

Prosthetic valve endocarditis: reviewing the problem.

Bacterial endocarditis is a serious complication of valve replacement, with an overall mortality of 59%. Fever, although a constant feature of the condition, is a nonspecific finding; other manifestations may or may not be present and the diagnosis may be overlooked. Any patient with a prosthetic heart valve and bacteremia should be considered to have endocarditis and should be treated accordingly.

Theophylline bioavailability: a comparison of the oral absorption of a theophylline elixir and two combination theophylline tablets to intravenous aminophylline.

The bioavailability of theophylline from single doses of an elixir (Elixophyllin) and two different tablet formulations, as compared to intravenous aminophylline, was studied with a crossover design in 12 normal volunteers. Both tablet formulations (Marax and Tedral) contain ephedrine. Marax contains hydroxyzine hydrochloride, and Tedral contains phenobarbital. The absorption of theophylline was most rapid from the elixir, whereas that from Marax was faster than that from Tedral. The peak concentrations of theophylline after administration of the 3 oral dosage forms were in the order, elixir greater than Marax greater than Tedral, however, the time to achieve peak concentration was highly variable and did not differ significantly among the 3 products. On the basis of area under the serum concentration-time curves, the absorption of theophylline from the elixir and from Marax was essentially complete. The area under the serum concentration curve after administration of Tedral was significantly less than that after intravenous aminophylline, elixir, and Marax; however, when the individual areas under the concentration curves were adjusted for intrasubject variation in elimination rate constant, the mean area under the concentration curve after Tedral no longer differed significantly from those of the intravenous and other two oral products. A large degree of intersubject variation in the oral absorption of theophylline was observe din this study. Therefore, in addition to the well-documented, large individual variation in the serum clearance of theophylline, intersubject differences in the absorption of the drug is another factor that complicates proper adjustment of the dose in oral theophylline therapy.