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PubMed2004

Development and validation of a direct, non-destructive quantitative method for medroxyprogesterone acetate in a pharmaceutical suspension using FT-Raman spectroscopy.

A simple linear regression method was developed and statistically validated for the direct and non-destructive quantitative analysis--without sample preparation--of the active pharmaceutical ingredient (API) medroxyprogesterone acetate (MPA) in an aqueous pharmaceutical suspension (150 mg in 1.0 ml) using FT-Raman spectroscopy. The linear regression was modelled by plotting the highest peak intensity of the vector normalized spectral band between 1630 and 1590 cm-1 against different MPA standard suspension concentrations. At this band, no spectral interferences from additives in the suspension are observed. The validated model was used for the quantification of a commercial suspension (150 mg in 1.0 ml) of the commercialized preparations. The same standards and samples were used, respectively, for the development and validation of a simple linear regression model and for the quantitative determination by means of HPLC-with sample preparation-as described for the related substances of MPA in the Ph. Eur. IV. The quantification results obtained by the FT-Raman method corresponded with the claimed label concentration (150.01+/-0.96 mg/ml (n=6)). Applying the HPLC method, however, a systematic error was observed (157.77+/-0.94 mg/ml (n=6)). The direct FT-Raman method hence appears the most reliable for the quantification of the MPA component in suspension, compared to the HPLC method that requires sample preparation. The latter method provides a systematic error because the exact volume or density of a suspension sample is unknown. A precise isolation of fixed volumes from a suspension is rather unfeasible because of the continuous sagging of the suspended particles and their sticking to the used materials in the isolation process.

Chromatography, High Pressure Liquid↗
PubMed2006

On the viscosity of composite suspensions of aluminum and ammonium perchlorate particles dispersed in hydroxyl terminated polybutadiene--New empirical model.

The rheological properties of fuel suspensions with various solid loadings up to close their maximum packing fraction and suspending media having different viscosities are investigated using the rotational viscometer at relatively low shear rates in which suspensions behave as Newtonian fluids. Aluminum (Al) and ammonium perchlorate (AP) particles are major solid components of any solid fuel system which should be distributed uniformly inside a polymeric binder based on hydroxyl terminated polybutadiene (HTPB). The experimental data generated in this investigation indicates that the relative viscosity of the suspensions is independent of viscosity of polymer binder, but in addition to solid content, geometrical aspects of the solid particles affect strongly the relative viscosity of suspensions. Maximum packing fraction of filler is found to be suitable quantitative measure of filler characteristics such as size, size distribution, shape and structure. Consequently, it is revealed that the relative viscosity of fuel suspension is a unique function of reduced volume fraction (Phi). Based on analogy of viscosity enhancement of reactive resin with cure conversion and suspension with filler content, an empirical model with two adjustable parameters originated from resin gelation model is suggested. According to this model and experimental results obtained in this investigation, a generalized model is proposed to describe the relative viscosity as a function of solid content in which the adjustable parameters are found to be general constants. The generalized model which is expressed as mu(r) = (1-Phi)(0.3 Phi-2) is found to be quite accurate to predict the experimental data. Furthermore, the applicability and accuracy of the generalized model are evaluated using the viscosity data of some suspension systems reported in the literature.

Journal Article↗
PubMed2001

Risk of recurrent stress incontinence in women undergoing the combined modified pereyra procedure and transvaginal sacrospinous ligament vault suspension.

OBJECTIVES: To determine the risk of recurrent stress urinary incontinence in women undergoing the combined modified Pereyra procedure and sacrospinous ligament vault suspension. METHODS: A retrospective analysis of 62 patients who underwent the modified Pereyra procedure at Harbor-UCLA Medical Center between October 1, 1993 and July 10, 1999 for stress urinary incontinence was performed. RESULTS: The study group consisted of 62 patients treated for stress incontinence; 34 (55%) of the 62 patients underwent the modified Pereyra procedure for stress incontinence, and 28 (45%) underwent the combined modified Pereyra procedure and sacrospinous ligament vault suspension for stress incontinence and coexistent uterine and/or vaginal vault prolapse. Patients undergoing the modified Pereyra procedure without vaginal vault suspension had higher subjective (91% versus 64%, P = 0.01) and objective (88% versus 61%, P = 0.02) cure rates of stress urinary incontinence compared with the patients undergoing the combined modified Pereyra procedure and sacrospinous ligament vault suspension. The mean follow-up period for the patients undergoing the modified Pereyra procedure (23 +/- 14.4 months) was similar to that of the patients undergoing the combined modified Pereyra procedure and sacrospinous ligament vault suspension (26 +/- 9.4 months) (P = 0.3). Compared with the objectively cured patients, patients with objective failure demonstrated postoperative bladder neck hypermobility and a higher rate of recurrent grade 2 or greater anterior vaginal prolapse. Eleven patients had postoperative detrusor instability, and 2 patients who underwent sacrospinous ligament vault suspension developed recurrent grade 3 apical vault prolapse. CONCLUSIONS: Patients undergoing the combined modified Pereyra procedure and sacrospinous ligament vault suspension have high rates of recurrent stress urinary incontinence.

Combined Modality Therapy↗
PubMedDate not supplied

Inflammatory effects of topical antibiotic suspensions containing propylene glycol in chinchilla middle ears.

This study examines the occurrence of inflammatory changes and cholesteatoma in the middle ears of seven chinchillas after the application of topical antibiotic suspensions containing two different concentrations of propylene glycol. The preparations used were Cortisporin otic suspension, which contains neomycin, polymyxin B, hydrocortisone, and 10.5% propylene glycol, and Cortisporin ophthalmic suspension, containing the same ingredients, but only a 2% concentration of propylene glycol. Six weeks after the administration of the Cortisporin preparations, applied to the middle ear through a transbulla approach, no cholesteatomas were found in the seven ears treated with the ophthalmic suspension. Evidence of mild inflammation was present in only two of these ears. In the seven contralateral ears treated with the otic suspension, middle ear adhesions were found in six, cholesteatoma was present in four, serous effusions were found in three, and one had a large tympanic membrane perforation. The ears that showed cholesteatomas also had histologic evidence of squamous metaplasia, granulation tissue, and erosion of the underlying bone. We submit that the pathologic responses of the middle ear mucosa treated with the otic suspension, were due to an inflammatory response to the higher concentration of propylene glycol compared to that of the ophthalmic suspension.

Animals↗
PubMed2004

Hard structured particles: suspension synthesis, characterization, and compressibility.

Hard interactions are developed on three grades of fumed silica by eliminating interparticle forces and sterically stabilizing the particles by attaching an organic coating to the surface of the particles, suspending them in an index-matching solvent and screening the electrostatics. These hard-structured particles are studied to understand the effects of the particle's microstructure on suspension properties without the influence of interparticle forces other than volume exclusion, Brownian, and hydrodynamic interactions. Light and X-ray scattering studies of low-volume-fraction suspensions suggest that the fumed silicas consist of primary particle of radius of gyration R(g1) approximately equals 16 nm and aggregate size R(g2) approximately 50 nm and mass fractal dimension D(f) approximately equals 2.2. Osmotic compressibilities of these suspensions are measured as a function of particle concentration exploring the packing mechanism of fumed silica. While there is minimal detectable change in the primary particle size, R(g2) varies by approximately 15%, providing insight into how suspension properties are related to particle size. As expected of hard particles with the same microstructure, the concentration dependence on the osmotic pressure superimposes with volume fraction of solids. The comparison of fumed-silica-suspension measurements to the known behavior of hard-sphere suspensions demonstrates the effects of particle geometry on suspension properties with indications of interpenetration of the fumed silica due to their open geometry.

Journal Article↗
PubMed1999

Physical stability of ethyl diatrizoate nanocrystalline suspension in steam sterilization.

PURPOSE: To study the effects of formulation variables on the physical stability of a submicron crystal (nanocrystal) suspension under steam sterilization conditions. METHODS: Suspensions of ethyl diatrizoate nanocrystals were prepared by wet milling in the presence of the surfactant poloxamine 908. Particle size distribution and zeta potential were measured by photon correlation spectroscopy. RESULTS: On heating, the mean particle size of the nanocrystal suspension remained essentially unchanged up to 110 degrees C, the cloud point of the stabilizing surfactant, but increased significantly above that temperature. The increase in particle size was a result of particle aggregation rather than crystal growth. Adding a cloud point booster to the suspension significantly minimized the particle aggregation at high temperatures. The purity of poloxamine 908 and the tonicity agent and buffer salt used also affected the heat stability of the suspension, the latter agents apparently through altering the surfactant cloud point. CONCLUSIONS: The aggregation of the ethyl diatrizoate nanocrystalline suspension under steam sterilization conditions was a result of phase separation of the stabilizing surfactant at its cloud point. When formulated with a cloud point booster to prevent the phase-separation, the suspension maintained its physical stability under steam sterilization without any significant change in particle size distribution.

Buffers↗
PubMed2006

Raman spectroscopy as a process analytical technology tool for the understanding and the quantitative in-line monitoring of the homogenization process of a pharmaceutical suspension.

The aim of this study was to propose a Process Analytical Technology (PAT) strategy for the quantitative in-line monitoring of an aqueous pharmaceutical suspension using Raman spectroscopy. A screening design was used to study the significance of process variables (mixing speed and height of the stirrer in the reactor) and of formulation variables (concentration of the active pharmaceutical ingredient (API) ibuprofen and the viscosity enhancer (xanthan gum)) on the time required to homogenize an aqueous pharmaceutical model suspension as response variable. Ibuprofen concentration (10% and 15% (w/v)) and the height of stirrer (position 1 and 2) were discrete variables, whereas the viscosity enhancer (concentration range: 1-2 g L-1) and the mixing speed (700-1000 rpm) were continuous variables. Next, a multilevel full factorial design was applied to study the effect of the remaining significant variables upon the homogenization process and to establish the optimum conditions for the process. Interactions between these variables were investigated as well. During each design experiment, the conformity index (CI) method was used to monitor homogeneity of the suspension mixing system in real-time using Raman spectroscopy in combination with a fibre optical immersion probe. Finally, a principal component regression (PCR) model was developed and evaluated to perform quantitative real-time and in-line measurements of the API during the mixing process. The experimental design results showed that the suspension homogenization process is an irregular process, for which it is impossible to model the studied variables upon the measured response variable. However, applying the PCR model it is possible to predict in-line and real-time the concentration of the API in a suspension during a mixing process. In this study, it is shown that Raman spectroscopy is a suitable PAT tool for the control of the homogenization process of an aqueous suspension. Raman spectroscopy not only allowed real-time monitoring of the homogeneity of the suspension, but also helped (in combination with experimental design) to understand the process. Further, the technique allowed real-time and in-line quantification of the API during the mixing process.

Chemistry, Pharmaceutical↗
PubMed2000

Molecular cloning and characterization of calreticulin, a calcium-binding protein involved in the regeneration of rice cultured suspension cells.

A full-length cDNA clone encoding a phosphoprotein (pp56) involved in the regeneration of rice (Oryza sativa L.)-cultured suspension cells was isolated by screening a rice cultured suspension cell cDNA library. The 1558-bp cDNA sequence contains an ORF encoding an acidic (pI 4.38) protein of 424 amino acids (47.9 kDa), sharing 70-93% and 50-53% homology with other plant and mammalian calreticulins, respectively. Sequence analysis of the cDNA clone revealed several significant conserved motifs, including a calreticulin family repeat motif in the central domain and two calreticulin family motifs in the N-domain, indicating that this gene is a rice calreticulin (CRO1). The CRO1 gene in long-term rice cultured suspension cells shows constitutive expression in both suspension culture and regeneration media. In contrast, expression of the CRO1 gene in short-term rice cultured suspension cells, which possess regeneration potential, is increased dramatically when these cells are transferred to the regeneration medium. After approximately 2 weeks in the regeneration medium, the expression of the CRO1 gene reverts to constitutive levels. These results demonstrate the presence of calreticulin in rice cultured suspension cells and its developmental regulation during the regeneration of rice cultured suspension cells.

Amino Acid Sequence↗
PubMed1999

Suspension sutures aid facial reconstruction.

BACKGROUND: Suspension, pexing or tacking sutures, which have a long history of use in facial cosmetic surgery, have only recently begun use in reconstruction. OBJECTIVE: In this study, the suspension suture was used to fix the closure line at the junction of cosmetic units, to prevent distortion of free margins secondary to wound contraction, eg, ectropion or eclabium, to prevent tenting across concavities, and to prevent scar spreading of wounds closed under tension. The acute complications and long-term effectiveness of this suturing technique in achieving the 4 desired results were evaluated. METHODS: During a 10-year period, 136 cases of surgical defects of the face created by the removal of nonmelanoma skin cancer by Mohs micrographic surgery were repaired using absorbable suspension sutures. The wounds were evaluated initially for acute complications of hemorrhage, infection, dehiscence, and necrosis; and later over 3 years for chronic sequela of hypertrophic scar, spread scar, contraction deformities such as distortion of free margins, and pigmentary changes. RESULTS: Suspension sutures were used in 60 cases of primary layered closure and 76 flaps of the face. Suspension sutures allowed primary closure of defects that would have required flaps in 72% of the cases and prevented distortion of free margins. There were more acute and long-term complications related to excess tension with primary closure than with flaps. Suspension sutures fixed the closure line at the junction of cosmetic units, prevented tenting across concavities, and both features were maintained over the duration of the study. CONCLUSION: Suspension sutures aided in obtaining linear closures, prevented distortion of free margins, prevented tenting across concavities, and fixed the closure line at the junction of cosmetic units; however, they did not prevent spread scars.

Face↗
PubMed1996

Sacrospinous vault suspension and abdominal colposacropexy: success rates and complications.

OBJECTIVE: Our purpose was to compare success rates and complications of sacrospinous vault suspension and abdominal colposacropexy. STUDY DESIGN: A case series is presented of 130 attempted sacrospinous vault suspensions with the Miya hook and 80 cases of abdominal colposacropexy, done in conjunction with other procedures. Patients were assessed 6 weeks and 6 and 12 months after surgery and yearly thereafter. RESULTS: Sacrospinous vault suspension was completed in 125 women (5 abandoned because of technical difficulty). Abdominal colposacropexy was completed in all 80 women. There was only one intraoperative complication-hemorrhage from the presacral veins during abdominal colposacroplexy. The incidence of postoperative febrile morbidity was 10% after sacrospinous vault suspension and 6% after abdominal colposacropexy. Follow-up ranged from 6 months to 5 years. The incidence of recurrent vault prolapse was 2.4% with sacrospinous vault suspension and 1.3% with abdominal colposacropexy. Demonstrable stress urinary incontinence occurred in one woman after abdominal colposacropexy and in none after sacrospinous vault suspension. CONCLUSION: Sacrospinous vault suspension and abdominal colposacropexy are associated with a low incidence of intraoperative and postoperative complications and recurrent vault prolapse. Latent stress urinary incontinence may be unmasked, particularly with abdominal colposacropexy, and preoperative urodynamic evaluation is therefore recommended.

Female↗
PubMed1982

A comparison of the pharmacological activity in cows of two suspensions of betamethasone alcohol.

The activity of two betamethasone (BM) suspensions, which differed only in their solids:vehicle ratio, was examined in cattle. Two groups of 10 cows received by subcutaneous injection either 20 ml of a 2 mg/ml aqueous suspension of BM alcohol or 2 ml of a 20 mg/ml aqueous suspension. A further 10 cows served as a saline-treated control group. The mean peak plasma BM concentration was significantly higher in cows treated with 2 mg/ml suspension. However, plasma BM levels tended to be maintained for longer by the 20 mg/ml suspension. A depression of early morning cortisol levels, similar to that seen with other synthetic glucocorticoids, was recorded with both BM preparations; the depression outlasted the presence of BM. Plasma glucose levels and circulating neutrophil numbers were elevated by BM treatment, and the magnitude and duration of these changes was related to the solids:vehicle ratio of the injected suspensions. The more concentrated suspension was absorbed more slowly and thus produced effects of greater duration.

Journal Article↗
PubMed2003

Budesonide inhalation suspension reduces the need for emergency intervention in pediatric asthma: a named-patient case series.

This report describes 15 children aged 10-35 months frequently hospitalized with uncontrolled asthma who were monitored for a mean of 26.9 months to assess the efficacy of budesonide inhalation suspension (AstraZeneca LP, Wilmington, DE) in reducing emergency interventions. Budesonide inhalation suspension was previously shown to relieve asthma symptoms, improve pulmonary function, and reduce rescue medication use in children as young as 6 months with mild to severe persistent asthma. We now show that > or = 1 year of treatment with budesonide inhalation suspension at doses between 0.25 and 1.5 mg/d decreased the burden of asthma. The mean number of hospitalizations caused by asthma or respiratory illness decreased from 1.8 +/- 1.37 in the period before initiation of treatment with budesonide inhalation suspension to 0.33 +/- 0.62 during treatment. Likewise, the mean number of oral prednisone courses decreased from 8.1 +/- 13.7 to 1.8 +/- 2.1, and the mean number of acute respiratory illnesses requiring additional therapy decreased from 2.7 +/- 2.3 before treatment with budesonide inhalation suspension to 0.87 +/- 0.74 during treatment. Numbers of emergency department visits decreased or remained the same after initiation of budesonide inhalation suspension treatment in all but two children. There was no effect on growth rate in this group of children with moderate to severe asthma. In this case series, budesonide inhalation suspension represents a safe, effective treatment option to prevent recurrent emergency intervention for patients < 3 years of age with poorly controlled asthma.

Anti-Inflammatory Agents↗
PubMed1985

The mixed epidermal cell-lymphocyte reaction. II. Epidermal Langerhans cells are responsible for the enhanced allogeneic lymphocyte-stimulating capacity of normal human epidermal cell suspensions.

Earlier studies carried out in our laboratory which demonstrated that disaggregated human epidermal cells isolated from normal flexor forearm skin produced a greater degree of primary allogeneic lymphocyte blastogenic response than did autologous peripheral blood mononuclear cells have since been confirmed by others. We have now completed a series of additional studies designed to determine the basis for this difference. Blocking studies with anti-HLA-DR antibodies revealed that the allogeneic response triggered by epidermal cells was completely dependent on the presence of unbound HLA-DR molecules eliminating the possibility that nonspecific mitogenic effects produced by the epidermal cell suspension might be responsible for the difference. In addition we were unable to demonstrate that epidermal keratinocytes were supplying a nonspecific helper or growth-promoting effect to the interaction between stimulating HLA-DR bearing Langerhans cells and responding T lymphocytes. Since it has recently been suggested that the entire alloantigen-presenting capacity of unfractionated peripheral blood mononuclear cells can be attributed to a small population of HLA-DR antigen-bearing dendritic cells, we have considered the possibility that the greater degree of allogeneic lymphocyte response produced by epidermal cells could be due to the presence of a greater percentage of HLA-DR positive dendritic cells present in epidermal cell suspensions (i.e., Langerhans cells). Peripheral blood dendritic cell-enriched fractions and epidermal cell suspensions that contained similar percentages of dendritic cells produced equivalent amounts of allogeneic lymphocyte stimulation, whereas peripheral blood dendritic cell-enriched fractions that contained greater percentages of dendritic cells than were present in epidermal cell suspensions produced greater amounts of allogeneic stimulation. We therefore conclude that the enhanced mixed lymphocyte reaction stimulating capacity of human epidermal cell suspensions could be explained by the fact that epidermal cell suspensions contain a greater percentage of HLA-DR bearing alloantigen-presenting dendritic cells than do unfractionated peripheral blood mononuclear cell suspensions.

Adult↗
PubMedDate not supplied

Testicular suspension: effect on testicular function.

The present communication studies the testicular function during suspension of the testicle to the scrotal neck. The material consisted of 28 dogs: 20 test dogs and 8 controls. In the 20 test dogs, the 2 testicles were suspended to the skin at the scrotal neck by 2-3 silk stitches. After one year, the testiculo-scrotal suspension was released. During testicular suspension, there was significant drop in the scrotal-rectal temperature difference. Semen quality showed gradual deterioration so that by the 12th month, 80% of the test dogs were azoospermic. There was a significant drop of serum testosterone and elevation of serum prolactin. 8 of the 20 test dogs which produced pregnancy when mated before testicular suspension, failed after suspension. After release of testicular suspension by 3 months, scrotal-rectal temperature difference, sperm count and morphology and hormonal assay showed normal levels. Mating of the same 8 dogs produced pregnancy. In conclusion, testicular suspension leads to spermatogenic depression and infertility which are reversible.

Animals↗
PubMed1997

Effect of formulation on the rheology of theophylline compound suspensions in Gelucires.

The theophylline derivatives, etofylline, diprophylline and proxyphylline, which exhibit increasing aqueous solubility, were used to prepare suspensions in seven saturated polyglycolyzed glycerides (Gelucires) characterized by their rising hydrophilic-lipophilic balance (HLB). Drug concentration was set at 25% w/w and the production temperature was set at the Gelucire melting point plus 30 degrees C in order to obtain suitable suspensions. Various formulation factors were studied. Ostwald flow indices revealed that the suspensions had a thixotropic shear-thinning behaviour and a relative viscosity which increased as drug aqueous solubility rose and Gelucire HLB decreased. These rheological properties could be explained by the chemical composition of Gelucires and drugs used. A microstructure was proposed for the liquid suspension such that colloidal particles and aggregates formed in these suspensions directly influenced the observed rheological properties. Observation of solidified suspensions by scanning electron microscopy confirmed this hypothesis. Moreover, a correlation between the relative viscosity of drug suspensions on the one hand and drug concentration, drug solubility and Gelucire HLB on the other allowed for the calculation of the required concentration of each theophylline derivative in each Gelucire to obtain a given viscosity.

Chemistry, Pharmaceutical↗
PubMed2001

Optimized suspension culture: the rotating-wall vessel.

Suspension culture remains a popular modality, which manipulates mechanical culture conditions to maintain the specialized features of cultured cells. The rotating-wall vessel is a suspension culture vessel optimized to produce laminar flow and minimize the mechanical stresses on cell aggregates in culture. This review summarizes the engineering principles, which allow optimal suspension culture conditions to be established, and the boundary conditions, which limit this process. We suggest that to minimize mechanical damage and optimize differentiation of cultured cells, suspension culture should be performed in a solid-body rotation Couette-flow, zero-headspace culture vessel such as the rotating-wall vessel. This provides fluid dynamic operating principles characterized by 1) solid body rotation about a horizontal axis, characterized by colocalization of cells and aggregates of different sedimentation rates, optimally reduced fluid shear and turbulence, and three-dimensional spatial freedom; and 2) oxygenation by diffusion. Optimization of suspension culture is achieved by applying three tradeoffs. First, terminal velocity should be minimized by choosing microcarrier beads and culture media as close in density as possible. Next, rotation in the rotating-wall vessel induces both Coriolis and centrifugal forces, directly dependent on terminal velocity and minimized as terminal velocity is minimized. Last, mass transport of nutrients to a cell in suspension culture depends on both terminal velocity and diffusion of nutrients. In the transduction of mechanical culture conditions into cellular effects, several lines of evidence support a role for multiple molecular mechanisms. These include effects of shear stress, changes in cell cycle and cell death pathways, and upstream regulation of secondary messengers such as protein kinase C. The discipline of suspension culture needs a systematic analysis of the relationship between mechanical culture conditions and biological effects, emphasizing cellular processes important for the industrial production of biological pharmaceuticals and devices.

Animals↗
PubMed1989

Colposuspension and transvaginal bladder neck suspension in the treatment of stress incontinence.

The present work was performed to evaluate the clinical usefulness of colposuspension in stress urinary incontinence without uterovaginal descent and bladder neck suspension in cases with uterovaginal descent. Modified Burch colposuspension was performed in 29 patients and modified Raz bladder neck suspension in 19 patients. The patients were examined clinically and urodynamically before and 8-12 months after operation. All patients in the colposuspension group regarded themselves as being totally continent postoperatively. In the bladder neck suspension group the respective figure was 58%, plus 21% showing improvement and 21% failures. Urodynamically, the cure rates (positive urethral closure pressure at stress) were 100% for colposuspension and 79% for bladder neck suspension. After colposuspension the urethral closure pressure at stress and the pressure transmission ratio were significantly increased whereas successful bladder neck suspension increased only urethral closure pressure at stress. The failed bladder neck suspensions did not induce any urodynamic changes. The present data confirms that Burch colposuspension is effective in stress urinary incontinence in women without simultaneous uterovaginal descent, whereas bladder neck suspension by the modified Raz technique did not appear to be optimal for the treatment of stress incontinence in patients with uterovaginal descent.

Adult↗
PubMed2004

Suspension laryngoscopy revisited.

Every critical advancement in direct laryngoscopic surgical technique has enhanced its precision. Among the most notable was Killian's seminal description of suspension laryngoscopy 90 years ago, which allowed for bimanual direct laryngoscopic surgery. Because of the technical difficulties encountered while performing suspension laryngoscopy, Brünings and Seiffert designed fulcrum laryngoscope holder-stabilizers for spatula laryngoscopes from Killian's original instrument design. Their devices, which were easier to use and better tolerated by patients, were supported from the laryngeal cartilage framework or chest wall. Laryngoscope holder-stabilizers were retrofitted to tubular laryngoscope specula in the 1940s and 1950s, whereupon they became very popular. Suspension laryngoscopy should have become more common subsequent to the introduction of general endotracheal anesthesia with paralysis in the 1960s. However, laryngoscope holder-stabilizers were entrenched as the device preferred by most, and they remain so today. This entrenchment occurred despite the fact that suspension laryngoscopy allows for positioning a larger examining speculum, which in turn allows for enhanced exposure and endolaryngeal procedural precision. The applied vector forces on the mandible, maxilla, oral cavity, pharynx, and larynx associated with suspension laryngoscopy are preferable to those associated with holder-stabilizers. A prospective assessment of 120 cases revealed effective use of suspension laryngoscopy in all. We believe that only a minority of surgeons has actually seen true suspension laryngoscopy and that its merits are worthy of reexamination.

History, 19th Century↗