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Biomedical subjects

J Sadé

Publications and source records attributed to J Sadé.

At least 19 recordsLinked to original sources
PubMed2003

Mathematical analysis of atelectasis formation in middle ears with sealed ventilation tubes.

AIM: A mathematical model was developed to identify time periods of atelectasis induction in middle ear (ME) ventilated via ventilating tubes (VT). Atelectatic ears are characterized by a total gas pressure lower than 760 mmHg. METHODS: Ventilating tubes were deliberately sealed and ME gas content changed in the presence of a preset blood gas pressure. Once sealed, CO2 rapidly diffuses out of the blood via lining tissues into the ME cleft. This results in initially a total ME pressure rise followed by a decrease in subatmospheric pressures. Time periods for atelectasis reformation was determined once ME pressure crossed the 760 mmHg value and continued to decline as the atelectasis reached higher grades. RESULTS: Time periods calculated by the model varied from 18 to 125 min in ME cavities ranging in volume from 0.5 to 3.5 mL, respectively. These results were calculated for conditions of venous blood in the lining mucosa blood and are consistent with prior clinical tests that measured an induced return to previous atelectasis state following the closure of the VT in 33 tested ears within 25-120 min (43 min on average). CONCLUSIONS: The model demonstrates that under the above conditions, diffusive gas transfer in relation to blood gas content is the leading mechanism to alterations in ME pressure and volume. It may be used as a tool to determine ME physiological cavity volume of ears with VT.

Carbon Dioxide↗
PubMed2001

How can the hooded seal dive to a depth of 1000 m without rupturing its tympanic membrane? A morphological and functional study.

Recent studies using a satellite-linked dive recorder have shown that the hooded seal (Cystophora cristata), a common Arctic pinniped, can dive to a depth of > 1000 m and stay submerged for close to 1 h. At these depths the water pressure reaches 100 atm, entailing obvious risk of serious damage to the hearing apparatus, mainly the tympanic membrane (TM) and middle ear (ME). We dissected and photodocumented the temporal bones of five newborn and three adult hooded seals in order to study the temporal bone structure and reveal its protective mechanisms for extreme pressure changes. Specimens were sectioned and stained for light microscopy. The thicknesses of the pars tensa and pars flaccida were found to average 60 and 180 microm, respectively. The ME cavity hosts a cavernous tissue of thin-walled vessels beneath the modified respiratory epithelium. The ME and external ear canal (EAC) volumes can be altered appreciably by filling/emptying the cavernous tissue with blood. The ossicles were fixed by contracting the tensor tympani and stapedius muscles simultaneously with complete occlusion of the EAC. According to Boyle's law, the volume of the gas-filled ME cavity at a depth of 1000 m is only 1% of its volume at the surface of the sea. Ascent from such a depth allows the gas in the ME cavity to expand, causing the TM to bulge laterally. This movement is counteracted by a reduction in the blood volume inside the cavernous sinuses, action in the tensor tympani and stapedius muscles and discharge of gas through the Eustachian tube. The presence of a firm, broad-based exostosis in the floor of the EAC lateral to the TM helps to obstruct the EAC.

Animals↗
PubMed2001

Hyperectasis: the hyperinflated tympanic membrane: the middle ear as an actively controlled system.

OBJECTIVE: To describe and analyze a middle ear condition in which the steady state of the middle ear pressure is elevated above the atmospheric pressure. SETTING AND STUDY DESIGN: This is a long-term survey of 59 patients from a private clinic who were observed on routine examination to have a ballooned out (hyperinflated) tympanic membrane. INTERVENTION: All patients underwent hearing tests, tympanometry, and Shullers (lateral) mastoid radiography. MAIN OUTCOME MEASURES: A hyperinflated tympanic membrane indicates a middle ear pressure that is higher than atmospheric pressure. The ballooned tympanic membrane returns to its physiological level after being punctured. This pressure situation is the reverse or opposite of atelectasis and is therefore termed hyperectasis. Hyperectasis, like atelectasis, is associated with a poorly pneumatized mastoid. RESULTS: Fifty-nine hyperectatic ears persisted in their hyperinflated state for weeks, months, or even years. The hyperectasis was preceded by atelectasis, and both conditions occasionally changed one into the other. The ballooned part of the tympanic membrane is usually thin and "scarred." Hyperectasis is not a rare situation and, once recognized, can be readily encountered in an otologic clinic. CONCLUSIONS: Like most biologic systems (e.g., blood pressure, temperature), the middle ear's central feature, i.e., pressure, also has a dynamic character vacillating up and down. It is conceivable that middle ear pressure is also actively regulated and controlled with the aid of a feedback mechanism. Passage of gas through the eustachian tube or absorption by diffusion-perfusion is also at least partly an active process. The up and down middle ear pressure vacillations are usually clinically benign and do not lead to any pathologic features as long as they are buffered by an accompanying normal mastoid pneumatization. It is the ear with a nonpneumatized mastoid that has limited ability to buffer pressure changes and that will present as an atelectasis, a retraction pocket, or (eventually a cholesteatoma) or their reverse, a hyperectatic tympanic membrane.

Acoustic Impedance Tests↗
PubMed2000

Surgical planning of the treatment of cholesteatoma and postoperative follow-up.

There is no single surgical treatment of choice for aural cholesteatoma. The extent of the cholesteatoma, the amount of preoperative destruction, and the size of the mastoid pneumatization should guide the surgeon in choosing the type of operation for a particular ear--which may range from a simple extraction of the cholesteatoma (delivery) all the way to a radical mastoidectomy. It is the clinical acumen that will determine the type of surgery for a given cholesteatomatous ear, algorithms being of little use in the complex situation of a pathological condition with infinite variables. However, even when the most suitable surgical modality is chosen by the best of surgeons, the operated ear will still be left with the innate cause of the cholesteatoma, namely, its physiopathologic background and its tendency to develop a negative gas balance in the middle ear. Because of this tendency to redevelop negative middle ear pressure, insertion and reinsertion of ventilation tubes are often necessary to prevent recurrent retractions and maintain aeration of the middle ear in posterior tympanotomies and modified radical mastoidectomies. Further, when the mastoid bowl is marsupialized, as in radical and modified radical mastoidectomies, the mastoid bowl is often not self-cleansing, thus periodically requiring the help of the otologist to keep it clean and dry. My study consisted of a long-term follow-up of 368 cholesteatomatous ears, which were operated on according to 6 different surgical modalities, ie, 112 radical mastoidectomies, 88 modified radicals, 72 posterior tympanotomies, 52 atticotomies, 36 deliveries, and 8 obliterations. Of the 368 ears, 11% did not require any postoperative toilet, whereas 89% required revisiting the surgeon periodically on an average of every 5 months, for cleansing of the mastoid cavity or securing the aeration of the middle ear by reinserting a ventilation tube.

Cholesteatoma, Middle Ear↗
PubMed2000

The buffering effect of middle ear negative pressure by retraction of the pars tensa.

OBJECTIVE: To measure the middle ear (ME) volume displaced when the pars tensa (PT) retracts during conditions of atelectasis (AT). STUDY DESIGN: Measurements were carried out on AT tympanic membrane (TM). SETTING: Measurements were carried out on ambulatory patients in a private clinic. PATIENTS: Thirty-nine patients treated for otologic disorders who came for a routine follow-up. INTERVENTIONS: Quantitative assessment of ME volume displaced by retraction of the PT was achieved by measuring the amount of fluid needed to fill up the retracted part of a TM. The fluid-3% aqueous boric acid solution was colored with gentian violet. MAIN OUTCOME MEASURES: Retraction of the PT may prevent formation of high ME negative pressure by reducing the ME volume. Retraction of the PT acts as a pressure buffer according to Boyls law, in which volume x pressure = constant. RESULTS: Direct correlation was found between the degree of AT and the ME volume displaced by the AT. Measurements of 12 AT ears grade I showed them to have a volume of 5 microL to 31 microL (average, 19.5 microL) and ten AT ears grade II had a volume of 15 microL to 87 microL (average, 39.5 microL). Eight AT ears grade III had a volume of 26 microL to 67 microL (average, 54.3 microL), and nine AT ears grade IV had 80 microL to 200 microL (average, 130.6 microL). CONCLUSIONS: Retraction of the PT may counteract an important potential negative ME pressure (up to several hundred millimeters of water) depending on the degree of retraction and the extent of mastoid pneumatization.

Adult↗
PubMed1999

Eustachian tube teratoma and its terminological correctness.

Teratomas are germ cell tumours usually found in the young and are characteristically composed of tissue foreign to the place where they arise. Two teratomas of the middle ear were first described in 1866 and since then, and to the best of our knowledge, 19 additional cases have been reported in the literature under different terms such as hairy congenital polyps, epidermoid cysts, dermoid cysts, hamartoma, cutaneous teratoma and teratomas. The difficulty in classifying germ cell tumours may explain the different terminologies encountered in the literature. The authors describe a case of teratoma of the eustachian tube presenting as a mass in the middle and external ear of a 10-week-old girl. Using this case, a review of the literature is performed in light of the new classification of germ cell tumours proposed by the World Health Organization (WHO). It is of note that most of the teratomas that present in the middle ear arise from, or involve, the eustachian tube.

Ear Neoplasms↗
PubMed1999

Mastoid buffering properties: I. Gas partial pressures.

Differences in the gas partial pressures between the middle ear (ME) cavity and the blood are an important factor in ME gas economy. Differences in gas partial pressures between various regions of the ME-mastoid air cell system (ME-MACS) could play a role as well. To determine whether gas partial pressure differences do occur between various compartments in the ME, we measured the rate of gas diffusion from one compartment to another in both an artificial model and in the ME-MACS of human temporal bones. The rate of gas diffusion between various areas of the ME and the mastoid tip was found to be rapid, with a half-life on the order of 2 minutes (range 0.8 to 5.3 minutes). We suggest that this high diffusion rate prevents the buildup of significant differences in gas composition in the ME-MACS system, which can therefore be regarded as a homogeneous gas pocket.

Diffusion↗
PubMed1998

Rate of gas exchange in the middle ear of guinea pigs.

Gas exchange between blood in the middle ear (ME) mucosa and ambient ME gas may be limited by diffusion through tissue or blood perfusion. In order to study the limiting factors in ME gas exchange, a hole was drilled in the bulla of 14 anesthetized guinea pigs through which a mass spectrometer probe was inserted and sealed in place. The rate at which oxygen (O2), carbon dioxide (CO2), nitrogen, and argon concentrations changed toward their steady state values was recorded. From the exponential fitted curves, gas rate constants (Kg) were calculated. The ratio KCO2/KO2 was 4:1, which is lower than expected from a diffusion-limited process in an aqueous compartment. The different rate ratios of CO2 and O2 indicate a diffusion-limited process. However, the deviation of the KCO2/KO2 ratio from that expected in aqueous solutions may indicate the involvement of a lipid compartment in gas exchange or other physiological mechanisms such as local acidity.

Animals↗
PubMed1998

Middle ear pressure variations during 50% N2O anesthesia as a function of mastoid pneumatization.

HYPOTHESIS: Mastoid size is a factor in middle ear (ME) pressure regulation. BACKGROUND: In a study investigating ME pressure variations during nitrous oxide (N2O) anesthesia, particularly high values of ME pressure increase rate (PIR) were observed in four patients with sclerotic mastoids. The current study is aimed at systematically assessing this observation. METHODS: Middle ear pressure was measured periodically in 30 patients during 50% N2O anesthesia using tympanometry. For each patient, a curve representing ME pressure during anesthesia was plotted. From the curve steepness, the PIR was calculated. Extent of mastoid pneumatization was assessed planimetrically using mastoid x-rays. Ears then were divided by the median into two groups: ears with small mastoids and ears with large mastoids. The difference between the mean PIR of both ear groups was statistically analyzed. RESULTS: A significant difference between the PIR was found among the two groups. In ears with mastoids smaller than 9.475 cm2 (the median), the PIR was significantly higher than in ears with mastoids > 9.475 cm2. CONCLUSIONS: These findings support the concept that the mastoid has a ME pressure buffering capability: the larger its volume, the better its buffering capability. It is therefore suggested, that the mastoid plays a role in ME pressure regulation.

Acoustic Impedance Tests↗
PubMed1997

Shrapnell membrane and mastoid pneumatization.

OBJECTIVE: To assess whether a correlation exists between the degree of pars flaccida (PF) retraction and the degree of mastoid pneumatization. DESIGN: The degree of PF retraction was defined by means of an operating microscope and a pneumatic otoscope. Degree of mastoid pneumatization was assessed planimetrically, using mastoid x-rays. SETTING: Private otologic clinic. PARTICIPANTS: A total of 595 ears, with intact pars tensa, of 332 adult patients. RESULTS: The degree of PF retraction was found to be inversely correlated to the level of mastoid pneumatization. Poorly pneumatized mastoids were associated with PF retractions. The poorer the pneumatization, the deeper the retraction. Well-pneumatized mastoids were associated with normal position of the PF. CONCLUSIONS: This study lends further support to the possibility that the mastoid pneumatic system functions as a middle ear pressure buffer. This possibility gives further explanation as to why ears with poorly pneumatized mastoids tend to develop tympanic membrane retractions and perforations, incus necrosis, or retraction pocket cholesteatoma, while ears with a large pneumatic system are rarely at such risk.

Adult↗
PubMed1997

Correlation between retractions of the pars flaccida and the pars tensa.

Retractions of the pars flaccida (PF) and the pars tensa (PT) were assessed in 250 atelectatic ears in an attempt to find out the way in which the differences in mechanical properties of the two parts of the tympanic membrane are reflected clinically. Retraction of PF was found in 217 ears (86.8 per cent) and retraction of PF in 150 (60 per cent). The concomitant presence of both types of retraction was observed in 117 ears (46.8 per cent) while 133 (53.2 per cent) had only one type, 100 of them (75.1 per cent) PF retraction and 33 (24.9 per cent) PT retraction. When only one type of retraction was present, the empirical probability of having a PF retraction was 75.1 per cent, while the probability of having a PT retraction was only 24.9 per cent. Clinically, the more frequent occurrence of PF retraction in the absence of PT retraction than vice versa reflects the greater collapsibility of the PF. When both types of retractions were present, we found a positive correlation between their severity.

Ear Diseases↗
PubMed1997

Revision myringoplasty.

This retrospective study was undertaken to review the short- and long-term results of 70 revision and 16 re-revision myringoplasty operations. Of the former, 43 cases (61.4 per cent) had initial success, six weeks following surgery. The leading causes of immediate failure (27 cases) were associated with a complete no-take of the graft, infection with graft necrosis and poor anterior adaptation of the graft in decreasing order. Six out of the 43 patients developed late re-perforations during the follow-up period, thus reducing the success rate of revision myringoplasty to 52.8 per cent. Late re-perforations were attributed to insidious atrophy of the tympanic membrane or episodes of acute otitis media. Sixteen patients underwent re-revision myringoplasty and their success rate was 62.5 per cent. The overall success rate of revision and re-revision myringoplasty was 54.7 per cent. It has been concluded that results of revision myringoplasty were independent of patients' age, location and size of perforation and the seniority of the surgeon.

Adolescent↗
PubMed1997

Secretory otitis media in adults: II. The role of mastoid pneumatization as a prognostic factor.

The sequelae of secretory otitis media (SOM) were monitored in 72 adult patients with SOM who were followed up for an average of 33 months. It was found that SOM became chronic and retraction of the tympanic membrane appeared as a function of the pneumatization of the mastoid. Ears with poor pneumatization (less than 6 cm2) developed chronic SOM in 52.2% of cases, as compared with 20% in cases with well-pneumatized ears (6 cm2 and above). Atelectasis developed in 37.3% of poorly pneumatized ears, and in only 5.7% of well-pneumatized ears. These sequelae may therefore be linked pathogenetically to the extent of pneumatization, as both the SOM and the sequelae appeared many years after formation and maturation of the pneumatic system. This study supports other studies that view the mastoid pneumatic system as an organ, as a middle ear pressure buffer. Well-pneumatized ears rarely develop a negative pressure and are seldom associated with chronic sequelae. Ears with poorly pneumatized mastoids lack the physiological function of such a pressure buffer. Ears with a tendency to develop a negative gas balance, whether as a result of deficient ventilation or excessive diffusion, will therefore develop a negative pressure more readily when their pneumatic system is underdeveloped, and consequently will be more prone to develop chronic sequelae.

Adolescent↗
PubMed1997

Dependence of middle ear gas composition on pulmonary ventilation.

The middle ear (ME) steady state gas composition resembles that of mixed venous blood. We changed arterial and venous blood gases by artificially ventilating anesthetized guinea pigs and measured simultaneous ME gas changes during spontaneous breathing, hyperventilation, and hypoventilation. During hyperventilation, PaCO2 and PvCO2 (a = arterial, v = venous) decreased from 46.0 and 53.0 mm Hg to 17.9 and 37.5 mm Hg, respectively, while PaO2 and PvO2 (85.6 and 38.2 mm Hg) did not change. This was accompanied by an ME PCO2 decrease from 70.4 to 58.8 mm Hg and a PO2 decrease from 36.8 to 25.4 mm Hg. During hypoventilation, PaCO2 and PvCO2 increased to 56.8 and 66.4 mm Hg, while PvO2 decreased to 21.8 mm Hg. The ME PCO2 increased simultaneously to 88.8 mm Hg and the ME PO2 decreased to 25.4 mm Hg. The ME PO2 decrease during hyperventilation may be explained by a 33% decrease in ME mucosa perfusion, calculated from the ME ventilation-perfusion ratio. This study shows that ME gas composition follows fluctuations of blood gas levels and thus may affect total ME pressure.

Animals↗
PubMed1997

On the function of the pars flaccida: retraction of the pars flaccida and buffering of negative middle ear pressure.

Retraction of the elastic pars flaccida (PF) is the first reaction to a middle ear (ME) negative pressure in adults. Such retraction reduces middle ear volume, thereby elevating the ambiant pressure. PF retraction acts therefore as a buffering mechanism which counteracts ME negative pressure. Measurements of the volume of the retracted PF were performed by filling the retracted PF space with a liquid. Measurements of 15 PF retraction pockets stages I showed them to have a volume of 1-3 m3 (average 2 mm3) and 23 retraction pockets stage II presented a volume of 4-8 m3 (average 5-8 mm3). It was calculated that retraction of the PF stage I and II may counteract 1-80 mm H2O of negative ME pressure-depending on the degree of retraction and the extent of mastoid pneumatization. The range of PF retraction suggests that normal pressure in the ME fluctuates, up to 8 mm H2O in average pneumatic ears (10 cm2) extending eventually to 80 mm2 in ears with sclerotic mastoids. Other mechanisms which may also serve the ME as pressure buffers by reducing its volume-once a negative pressure sets in-are retraction of the pars tensa, swelling of the mucosa or flooding the ME cavity with an exudate.

Adult↗
PubMed1996

Histopathologic changes of the tympanic membrane in acute and secretory otitis media.

The histopathologic changes observed in 40 normal and inflamed temporal bones of infants and children are reported. The tympanic membranes of patients with acute and secretory otitis media underwent considerable swelling compared to those of normal controls. Tympanic membranes with acute otitis media were thicker than those with secretory otitis media, but the difference was not statistically significant. The epithelial layer showed an increase in the number of cell layers. The lamina propria demonstrated the most significant changes of all layers with a marked swelling due to edema, engorged blood vessels, and inflammatory cell infiltration. Increased numbers of distended capillaries were present, predominantly in the subepithelial connective tissue layer, while infiltration of inflammatory cells was mainly in the submucosal connective tissue layer. By contrast, the involvement of the mucosal layer was modest and was composed of cuboidal cells, except for small islands of metaplastic mucosa with mucus production occasionally encountered in specimens with secretory otitis media.

Acute Disease↗
PubMed1996

Secretory otitis media in adults: I. The role of mastoid pneumatizationas a risk factor.

We analyzed clinically 102 ears with secretory otitis media (SOM) belonging to 72 adult patients who during their adult life had not suffered previously from ear disease. As in children, most of the cases (63%) could be traced directly to an upper respiratory tract infection. The most striking finding was the preponderance of poorly pneumatized mastoids-which were measured planimetrically-among our SOM cohort. This was found in adult SOM ears compared to contralateral healthy ears (4.59 versus 7.88 cm2), as well as when all 102 SOM ears were compared with values of the normal population (5.41 versus 12.9 cm2). This study showed that poorly pneumatized mastoids are a significant risk factor as far as adult SOM is concerned.

Adolescent↗