Evaluation of a flexible bronchoscope prototype designed for bronchoscopy during mechanical ventilation: a proof-of-concept study.

Bronchoscopy during mechanical ventilation of patients' lungs significantly affects ventilation because of partial obstruction of the tracheal tube, and may thus be omitted in the most severely ill patients. It has not previously been possible to reduce the external diameter of the bronchoscope without reducing the diameter of the suction channel, thus reducing the suctioning capacity of the device. We believed that a better-designed bronchoscope could improve the safety of bronchoscopy in patients whose lungs were ventilated. We designed a flexible bronchoscope prototype with a drumstick-shaped head consisting of a long, thin proximal portion; a short and large distal portion for camera docking; and a large suction channel throughout the length of the device. The aims of our study were to test the impact of our prototype on mechanical ventilation when inserted into the tracheal tube, and to assess suctioning capacity. We first tested the efficiency of the suction channel, and demonstrated that the suction flow of the prototype was similar to that of conventional adult bronchoscopes. We next evaluated the consequences of bronchoscopy when using the prototype on minute ventilation and intrathoracic pressures during mechanical ventilation: firstly, in vitro using a breathing simulator; and secondly, in vivo using a porcine model of pulmonary ventilation. The insertion of adult bronchoscopes into the tracheal tube immediately impaired the protective ventilation strategy employed, whereas the prototype preserved it. For the first time, we have developed an innovative flexible bronchoscope designed for bronchoscopy during invasive mechanical ventilation, that both preserved the protective ventilation strategy, and enabled efficient suction flow.

Somatic tinnitus prevalence and treatment with tinnitus retraining therapy.

OBJECTIVES: Somatic tinnitus originates from increased activity of the dorsal cochlear nucleus, a cross-point between the somatic and auditory systems. Its activity can be modified by auditory stimulation or somatic system manipulation. Thus, sound enrichment and white noise stimulation might decrease tinnitus and associated somatic symptoms. The present uncontrolled study sought to determine somatic tinnitus prevalence among tinnitus sufferers, and to investigate whether sound therapy with counselling (tinnitus retraining therapy; TRT) may decrease tinnitus-associated somatic symptoms. METHODS: To determine somatic tinnitus prevalence, 70 patients following the TRT protocol completed the Jastreboff Structured Interview (JSI) with additional questions regarding the presence and type of somatic symptoms. Among 21 somatic tinnitus patients, we further investigated the effects of TRT on tinnitus-associated facial dysesthesia. Before and after three months of TRT, tinnitus severity was evaluated using the Tinnitus Handicap Inventory (THI), and facial dysesthesia was assessed with an extended JSI-based questionnaire. RESULTS: Among the evaluated tinnitus patients, 56% presented somatic tinnitus-including 51% with facial dysesthesia, 36% who could modulate tinnitus by head and neck movements, and 13% with both conditions. Self-evaluation indicated that TRT significantly improved tinnitus and facial dysesthesia in 76% of patients. Three months of TRT led to a 50% decrease in mean THI and JSI scores regarding facial dysesthesia. CONCLUSIONS: Somatic tinnitus is a frequent and underestimated condition. We suggest an extension of the JSI, including specific questions regarding somatic tinnitus. TRT significantly improved tinnitus and accompanying facial dysesthesia, and could be a useful somatic tinnitus treatment.

[Severe hypofibrinegenemia after rattlesnake envenomation in France]. / Hypofibrinogénémie sévère après morsure de crotale en France.

A 22-year-old man, who maintains illegally numerous exotic snakes at home (suburbs of Paris), was bitten by one of his Bresilian rattlesnakes, the lance-headed viper Bothrops moojeni, with grade III envenomation. The fibrinogen was less than 0,5 g/L, the prothombin time was 22%, the activated partial thromboplastin time was 94 seconds. The authors discuss the biological and clinical management of this defibrination, due to defibrinogenating proteases (thrombin-like enzymes), present in Bothrops moojeni venom. The patient received 7 vials of an antivenom directed to another crotal, Bothrops lanceolatus. Despite the importance of defibrinogenation, there was only a few clinical evidence of bleeding, according to the literature. The normalization of coagulation studies occured only after day 11. This case-report outlines the danger of the increase of exotic snakes maintained as pet in France and the difficulties to obtain specific antivenoms.

[Hepatosplenic and kidneys candidasis complicating an acute myeloblastic leukemia. A case treated with voriconazole and caspofungin]. / Candidose hépato-spléno-rénale compliquant une leucémie aiguë myéloblastique. A propos d'un cas traité par l'association voriconazole et caspofungine.

We report the observation of hepato-splenic and kidneys candidiasis complicating the chemotherapy of a myeloblastic leukemia (LAM5b). Following the lack of effectiveness of a first line treatement, using amphotericine B liposomale and 5-fluorocytosine, implementation of an association of new molecules, a triazole of second generation (voriconazole) and an echinocandine (caspofungine) has allowed a successful result.

Evidence that a transient enhancement of endogenous hematopoiesis contributes significantly to the favorable outcome following interleukin 1 pretreatment and allogeneic bone marrow transplantation.

The administration of IL-1, a potent radioprotective cytokine, before allogeneic BMT is associated with an early transient increase of circulating granulocytes, successful engraftment, and accelerated multilineage hematopoietic recovery. We have examined the effects of IL-1 alpha pretreatment on the engraftment of an allogeneic BMT unable to sustain survival by itself after a lethal irradiation: (1) transplantation of a limited amount of marrow cells and (2) transplantation several days after irradiation. IL-1 was unable to allow the engraftment of an early quantitatively inadequate BMT. However, delayed BMT with limited amounts of marrow cells was associated with engraftment in IL-1 pretreated recipients. Engraftment of a late (day 12) BMT in these IL-1-pretreated mice was comparable to the engraftment of a similar day 12 allogeneic BMT in non-IL-1-pretreated mice rescued from the lethal irradiation by an early (day 1) syngeneic graft. These findings demonstrate that IL-1 pretreatment can result in a dissociation between BMT-induced survival and engraftment and suggest that the favorable effects of IL-1 pretreatment in an allogeneic BMT setting are mainly mediated through a transient enhancement of endogenous hematopoiesis and not through a direct effect on the allogeneic stem cells present in the marrow graft.

Simian T cell leukemia virus type I from naturally infected feral monkeys from central and west Africa encodes a 91-amino acid p12 (ORF-I) protein as opposed to a 99-amino acid protein encoded by HTLV type I from humans.

A single protein of 12 kDa, p12 is encoded by the HTLV-I genome from both the singly spliced mRNA pX-ORF-I and doubly spliced mRNA pX-rex-ORF-I. While many full-length sequences of HTLV-1 are known, data on the p12 regions of African STLV-I are unavailable. We have undertaken to sequence the p12 gene in STLV-I from Central and West Africa naturally infected primates, and have compared them to known p12 sequences of HTLV-I. Our data on sequence and in vitro transcription-translation analyses indicate that p12 is a 91-amino acid (aa) protein among STLV-I strains from Central and West Africa, in contrast to the 99-aa protein found among HTLV-I strains around the globe. The p12 sequences of STLV-I exhibit a marked genetic variability at the level of both nucleotide and peptide sequences. Hydropathic and helical wheel analyses reveal that 60% of residues in HTLV-I p12 are hydrophobic, in contrast to 55% in STLV-I from Africa. Although HTLV-I and STLV-I show a similar putative antigenic site, a second potential site was located exclusively in STLV-I from Africa. There are differences in the predicted transmembrane domains in p12 between STLV-I and HTLV-I. Furthermore, the secondary structure data according to the Chou and Fasman algorithm predict an alpha-helical domain at the carboxy terminus in HTLV-I, and this domain may be truncated in STLV-I p12. The amino acid sequence of p12 shows two leucine zipper motifs (LZMs) at the amino terminus and in the middle region, respectively. This is the first report describing the size differences in p12 protein between HTLV-I and STLV-I, which may provide insights into pathogenic mechanisms used by HTLV-I and STLV-I.

PCR amplification of large genomic fragments from human and simian immunodeficiency virus infected cell lines.

Polymerase chain reaction (PCR) has been used to amplify the large fragments from viral genomic DNA of SIV from wild caught, asymptomatic Erythrocebus monkeys from Western Africa (Senegal) and also from HIV-2 infected cell lines. By using consensus primer sequences from highly conserved stretches of gag, pol and env genes, two halves of the viral genome of HIV-2 and SIV (isolated from west African Erythrocebus monkeys) have amplified by PCR. One half spans 5200 bp from within the U3 region of the 5' long terminal repeat (LTR) into pol gene and an overlapping fragment spans 3700 bp from the pol gene into U5 region of 3' LTR. Also fragments ranging from 1-2.3 kb from gag pol and env genes have been successfully amplified. Our data demonstrate that primers used to amplify large segments from viral DNA yield better results if they are derived from a consensus sequence of a highly conserved stretch of the viral genome.

[Quantitative and qualitative anomalies of sperm in African individuals infected with HIV]. / Anomalies quantitatives et qualitatives du sperme chez des individus africains infectés par le VIH1.

Semen from 16 HIV1-infected african individuals (12 at stage II/CDC; 4 with pre-AIDS) has been analyzed both quantitatively (volume; number of spermatozoa) and qualitatively (motility). 12 healthy HIV1-seronegative individuals were recruited as controls. The HIV1-infected patients showed generally abnormalities of the semen: oligospermia (7 cases), azoospermia (3 cases), or asthenospermia (10 cases). These abnormalities were more marked in patients at advanced stages of the HIV infection. In comparison with the control group, the HIV1-infected individuals had more frequently a past history of sexually transmitted diseases. These abnormalities in the composition of the semen in HIV1-infected african individuals could affect the fertility of these men; that could indirectly restrict the risk of congenitally HIV contaminated child.

[Resurgence of yaws in Central African Republic. Role of the Pygmy population as a reservoir of the virus]. / Résurgence du pian en République centrafricaine. Rôle de la population pygmée comme réservoir de virus.

The authors present the results of a clinical (framboesia) and serological (TPHA and VDRL) investigation aimed at defining the reservoir of virus of yaws in the Lobaye area (southwest of CAR) out of which the disease spreads in spite of previous mass treatment campaigns. The Lobaye focus is still active because we found among the pediatric population under the age of 15 years, 5.6% contagious skin lesion and 19.6% VDRL+. In this area with contact between nomadic Pygmies and sedentary ethnic groups, the observed level of clinical and serological attacks suggested that the pygmie population, as previously described, makes up the principal focus of yaws. For every 1 case found through clinical examination, 3.5 cases VDRL+ and 4.8 cases TPHA+ are found through serological examination. This proportion indicates that clinical screening alone is not sufficient to evaluate the endemic yaws level in a population.

[Immune response to equine Chorionic Gonadotropin used for the induction of ovulation in goats and ewes]. / Réponse immunitaire à la eCG utilisée dans le traitement de l'induction d'ovulation chez la chèvre et la brebis.

In dairy goats and ewes the use of equine Chorionic Gonadotropin (eCG) as a convenient hormone for the induction of ovulation is necessary for out-of-season breeding and artificial insemination (AI). Treatment for induction and synchronization of ovulation consists of a progestagen delivered by vaginal sponge, followed by an eCG injection. In some females, the first injection of eCG induces a humoral response with high concentrations of anti-eCG antibodies in contrast to other females displaying a very low concentration of anti-eCG antibodies. Females eliciting a low response were also poor responders after the following treatments. Conversely, high responders at the first treatment systematically yielded high immune responses upon the following treatment. By a molecular genetic approach using microsatellites we showed that the anti-eCG immune response phenotypes were associated with MHC class II polymorphism. Females with high residual antibody concentrations at the time of eCG injection exhibited a much lower kidding rate than other females did. Lower fertility of these females, inseminated at a fixed time after eCG treatment (43H for goats and 55H for ewes), might be due to the delay in estrus occurrence and the pre ovulatory LH surge. Consequently, under field conditions old females selected for AI are only those with low residual anti-eCG antibody concentrations and old females with high residual antibody concentration are culled from AI breeding because of their low fertility during the previous year. So we have undertaken comparative studies to establish if the anti-eCG immune response is correlated with the global immunity in animals.

[Thoracic nocardiasis associated with macrophage activation syndrome]. / Nocardiose thoracique associée à un syndrome d'activation macrophagique.

Nocardiasis is an uncommon bacterial disease often observed in immunodepressed patients. Its interactions with the immune system remain poorly known. We report a case of Nocardia asteroides thoracic nocaridiasis in an African subject who also had macrophage activation syndrome. We recall the classic data on nocardiasis in Africa and emphasize the importance of emergence in HIV-infected subjects. The association between nocardiasis and macrophage activation syndrome suggest a possible pathogenic mechanism involving the immune system (lymphocytes and macrophages) and Nocardia asteroides.

[Sensitivity to antibiotics of bacteria from nosocomial infections. Evolution in resuscitation services of military hospitals]. / Sensibilité aux antibiotiques des bactéries d'infections nosocomiales. Evolution dans les services de réanimation des hôpitaux des armées.

OBJECTIVE: The aim of this study, conducted in the French Military hospitals, was to monitor the course of the antimicrobial sensibility of bacteria isolated from nosocomial infection in intensive care units. PATIENTS AND METHODS: A prospective study has been conducted from January to December 1998 in all the intensive care units of the French Army. All the non-repetitive strains isolated from nosocomial infection were collected and sent to a reference centre. Antimicrobial susceptibility was determined by the agar dilution method. Beta-lactamase were identified by iso-electro-focalisation. Antibiotics choice and interpretative criteria were those of the "Comité Français de l'Antibiogramme de la Société Française de Microbiologie". RESULTS: A total of 849 strains are included in this study. Pseudomonas aeruginosa was the most frequently isolated bacterium (20%) followed by Escherichia coli (19%) Staphylococcus aureus (15%), coagulase-negative Staphylococci (CoNS) (11%) and Enterococci (7%). Imipenem was the most effective antibiotic against enterobacteriaceae (336 isolates; 100% susceptibility). Gentamicin (92%), amikacin (92%) third generation cephalosporins (83%), aztreonam (83%) and ciprofloxacin (78%) were also very effective. Resistance to III generation cephalosporins was correlated with an extended spectrum beta-lactamase (BLSE) in 36% of cases. This BLSE could be associated with an over production of the constitutive cephalosporinase. The most frequent species producing BLSE were Enterobacter aerogenes (75% of BLSE) and Klebsiella pneumoniae (17%). Among the 172 P. aeruginosa isolated, antimicrobial susceptibility were respectively: 71% for imipenem, 62%: tobramycin, 60%: amikacin 59%: ciprofloxacin 59% piperacillin + tazobactam, 55% piperacillin, 53%: ceftazidime and 44% for ticarcillin. Seventy per cent of the 96 CoNS and 50.2% of the 126 S. aureus isolated were resistant to methicillin. A strain of S. aureus and 2 CoNS strains had intermediate resistance to teicoplanin. Twenty per cent of the 59 Enterococci strains isolated were resistant to aminopenicillins (10/11 strains of E. faecium), and 9% presented a high level of resistance to gentamicine. One strain of E. faecium was resistant to vancomycin. CONCLUSION: The evolution of the susceptibility to antibiotics in intensive care units reflects the antibiotic pressure and level of cross-transmission. High rates of meticillin-resistance among staphylococci, of resistance to beta-lactams antibiotics among P. aeruginosa and of ciprofloxacin among Enterobacteriaceae are shown in this study. The implementation of appropriate strategies for surveillance and prevention is necessary.

[Antibiotic sensitivity of Salmonella isolated in army hospitals between 1998-1999]. / Sensibilité aux antibiotiques des salmonelles isolées dans les hôpitaux des armées en 1998-1999.

OBJECTIVES: Monitor the evolution in France of antibiotic sensitivity of non-typhoid salmonella isolated in fecal cultures conducted in army hospital laboratories. METHODS: A prospective study was performed from January 1998 to December 1999 in all the biology departments of the 11 army hospitals in France. All the non-repetitive strains were sent to an official center for serotyping and determination of the minimum inhibiting concentrations, by dilution in Mueller Hinton's gelose. The antibiotics currently used in treatment were tested and interpretation endpoints followed the recent recommendations of the Antibiogram committee of the French society of microbiology. Identification of beta-lactamase was conducted by iso-electric focalization and polymerization by chain reaction (PCR). For Salmonella Typhimurium, research for the specific resistance locus of the DT104 clone was made using PCR. RESULTS: Two hundred and twenty-two non-repetitive salmonella strains were isolated. The principle serotypes found were: Salmonella Enterididis (23.9%), S. Typhimurium (21.2%) and S. Hadar (10.8%). All the strains were sensitive to ciprofloxacin and cefotaxim, whereas one third exhibited reduced sensitivity to aminopenicillin. Depending on the serotype, Typhimurium and Hadar serotypes exhibited significantly lesser sensitivity to aminopenicillin, nalidixic acid and tetracycline. For S. Typhimurium, resistance is related to the diffusion of the multiresistant DT104 clone, which involves half of the strains of this serotype. For S. Hadar, 18 out of 24 strains (75%) were resistance to nalidixic acid, and 5 of them exhibited reduced resistance to ciprofloxacin. There was no difference in sensitivity to antibiotics between the strains responsible for diarrhea and those isolated in systematic examinations for capacity to work in the food trade (respectively 54 and 46% of strains). CONCLUSION: Non-typhoid salmonella are frequently isolated in diarrhea of infectious origin. The increasing resistance to antibiotics is primarily related to the diffusion of the DT104 clone, regarding S. Typhimurium and to the increase in resistance to quinolone, regarding S. Hadar.

[Tinea capitis: sample surveys among school doctors and dermatologists in the Paris suburbs]. / Prise en charge des teignes: enquête auprès de médecins scolaires et de dermatologues franciliens.

BACKGROUND: Subsequent to detection of several cases of anthropophilic tinea capitis, we wanted to know whether the legal decree requiring eviction from school and an epidemiology survey in the children community or the family is implemented properly. METHODS: Two sample surveys were carried out among 50 school doctors from the Hauts-de-Seine department and 110 dermatologists working the Paris suburbs. RESULTS: Eviction from school was rare and not based on the type of dermatophytes (anthropophilic or zoophilic agent). Likewise, epidemiology survey was neglected, often being solely clinical for other family members. Systematic sampling in the children community or in the family was very exceptional. DISCUSSION: Despite the rise in the number of cases of anthropophilic tinea capitis in Paris suburbs, the decree is not often implemented. Dermatologists would appear to be responsible for this situation, especially in case of M. langeronii, which is very contagious in nursery school.

[Epidemiology of resistance to antituberculosis drugs in Mycobacterium tuberculosis complex strains isolated from adenopathies in Djibouti. Prospective study carried out in 1999]. / Epidemiologie de la resistance aux antituberculeux des souches du complexe Mycobacterium tuberculosis isolees d'adenopathies a Djibouti. Etude prospective realisee en 1999.

Tuberculosis is a major cause of death in the Republic of Djibouti. Tuberculous lymphadenitis represents about 25% of the clinical forms of tuberculosis in this country. Between January 1999 and April 1999, 196 lymph node specimens were consecutively collected from 153 patients living in Djibouti. Testing of susceptibility to the major anti-tuberculosis drugs was performed by the proportion method. Growth of Mycobacterium tuberculosis complex strains was obtained from specimens of 85 patients including 9 with prior treatment. Strains were identified as Mycobacterium tuberculosis in 78 cases, Mycobacterium canetti in 3, Mycobacterium africanum in 3, and Mycobacterium bovis in 1. Prevalence of HIV infection was 15%. Assessment of primary resistance demonstrated that the overall resistance rate, i.e., resistance to 1 or more drugs, was 18 (21.2%). Results showed resistance to isoniazid (H) in 6 cases (7.1%), rifampicin (R) in 3 (3.5%), ethambutol (E) in 1 (1.2%), streptomycin (S) in 13 (15.3%) and pyrazinamide (Z) in 1 (1.2%). Multidrug resistance (MDR) was found in 2 cases (2.4%). Assessment of acquired resistance demonstrated resistance to H in 4 cases (44%), R in 2 (22%), S in 2 (22%), E in 0, Z in 0 and MDR in 1 (11%). These findings were not significantly different from data obtained from sputum samples analysed between 1997 and 2000 or from those described in a study conducted in 1985.

[Rapid screening for beta lactamase of Neisseria gonorrhoeae in pus from blennorrhagia]. / Dépistage rapide dans le pus de blennorragie de la Bétalactamase de Neisseria gonorrhoeae.

The authors have evaluated in an isolated post, a method for rapid detection of penicillinase-producing Neisseria gonorrhoeae in urethral exudates. This method, easy to use and not very expensive, offers a good sensitivity, and could help in making for the therapeutic decision and in the epidemiological surveillance of Neisseria gonorrhoeae's resistance to penicillin.

[A 7-year survey of strains identified in blood cultures in a clinical hematology unit]. / Etude sur sept ans des isolats d'hémocultures dans un service d'hématologie clinique.

GOAL: This study had for aim to analyze the epidemiology of strains identified in blood cultures (hôpital d'instruction des armées Percy, Clamart, France, hematology unit) to compare the rate of identified micro-organisms with literature data, and to search for a possible correlation between antibiotherapy management and evolution of resistance profiles. MATERIAL AND METHODS: All the micro-organisms (N = 690) collected over seven years (January 1996 to December 2002), from blood cultures of hospitalized patients in conventional and sterile sector were studied. RESULTS: Gram positive cocci rate (GPC) was 62.6% and Gram negative bacilli (GNB) 31.3%. Evolution in time showed a decrease of GPC and an increase of GNB, notably the non fermenting Gram negative bacilli, leading to an equal rate by 2001-2002. The most frequently identified species were Staphylococcus epidermidis (36.4%), Escherichia coli (8.7%), Pseudomonas aeruginosa (6.8%), and Staphylococcus aureus (4.9%). The rate of methicillin-resistant staphylococci was 63.6%. Fifty-five percent of E. coli strains had a penicillinase phenotype. Pseudomonas aeruginosa resistance was 8.5, 8.5, 6.4 and 8.5%, respectively for ceftazidime, piperacillin-tazobactam, imipenem, and amikacin. CONCLUSION: This study showed a tendency to inversion of former bacteremia epidemiology with increasing negative Gram bacilli. It justifies the antibiotherapy protocols adopted in the hematology unit.

[Bone and joint sites of African histoplasmosis (Histoplasma duboisii). Apropos of a case and review of the literature]. / Localisations ostéo-articulaires de l'histoplasmose africaine (Histoplasma duboisii). A propos d'un cas et revue de la littérature.

The authors report a case of disseminated African histoplasmosis with bone and joint involvement in a black 28-year-old citizen of the Central African Republic who presented with a 17-month history of multiple osteoarticular lesions (sternoclavicular joints, humerus, ribs), cutaneous lesions (face, scalp, thorax), and lymphadenopathy. Clinical manifestations resolved rapidly under treatment with ketoconazole (600 mg/d for 10 days then 400 mg/day for nine months). Persistent yeast cells were then found upon examination of a lymph node biopsy specimen. The characteristics and diagnosis of osteoarticular lesions due to African histoplasmosis are discussed on the basis of a review of the literature. Bone and joint lesions due to African histoplasmosis have not yet been reported in patients with the acquired immunodeficiency syndrome. However, the expanding epidemic of human immunodeficiency virus infection in Africa can be expected to result in an increase in the incidence of African histoplasmosis. Imidazole derivatives are easier to use on a long-term basis than amphotericin B and have significantly improved our ability to treat African histoplasmosis.

Fate of inhaled monoclonal antibodies after the deposition of aerosolized particles in the respiratory system.

Monoclonal antibodies (mAbs) are usually delivered systemically, but only a small proportion of the drug reaches the lung after intravenous injection. The inhalation route is an attractive alternative for the local delivery of mAbs to treat lung diseases, potentially improving tissue concentration and exposure to the drug while limiting passage into the bloodstream and adverse effects. Several studies have shown that the delivery of mAbs or mAb-derived biopharmaceuticals via the airways is feasible and efficient, but little is known about the fate of inhaled mAbs after the deposition of aerosolized particles in the respiratory system. We used cetuximab, an anti-EGFR antibody, as our study model and showed that, after its delivery via the airways, this mAb accumulated rapidly in normal and cancerous tissues in the lung, at concentrations twice those achieved after intravenous delivery, for early time points. The spatial distribution of cetuximab within the tumor was heterogeneous, as reported after i.v. injection. Pharmacokinetic (PK) analyses were carried out in both mice and macaques and showed aerosolized cetuximab bioavailability to be lower and elimination times shorter in macaques than in mice. Using transgenic mice, we showed that FcRn, a key receptor involved in mAb distribution and PK, was likely to make a greater contribution to cetuximab recycling than to the transcytosis of this mAb in the airways. Our results indicate that the inhalation route is potentially useful for the treatment of both acute and chronic lung diseases, to boost and ensure the sustained accumulation of mAbs within the lungs, while limiting their passage into the bloodstream.