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PubMed1996

[The management of chronic asthma with inhaled beta 2 agonists--regular use? symptomatic use?].

Beta-agonist is a widely used bronchodilator. Although it has an ability to dilate bronchus rapidly, it shows no or minimal relief for severe asthma and no effect on the inflammation which is thought as a most important factor in disease of asthma. Some reports showed that the regular use of inhaled beta 2 agonist induced hypersensitivity of bronchoconstriction, and some showed that the overdose of inhaled beta 2 agonist induced an increase of asthma death. We should discuss how we use inhaled beta 2 agonist systematically now. Depends on the several guidelines, inhaled beta 2 agonist can be used on demand for mild and moderate asthma, and if inhaled beta 2 agonist need to be used regularly for more severe condition of asthma, inhaled corticosteroid and anti-inflammatory agents should be started. Inhaled beta 2 agonist can be used up to 4 times a day. To save the dose of inhaled beta 2 agonist for the control of asthma, the use of a handy peak flow meter will be beneficial.

Administration, Inhalation↗
PubMed1997

[Low dose inhalation of nitric oxide in chronic obstructive pulmonary diseases].

We studied the effect of inhalation of various concentrations of nitric oxide (NO)(2 ppm, 5 ppm, and 10 ppm) on the pulmonary circulation and on arterial oxygenation in 11 patients with stable chronic obstructive pulmonary disease. Inhalation of 2 ppm of NO resulted in values of mean pulmonary arterial pressure significantly lower than those measured while breathing room air only (24.1 +/- 1.7 vs 20.7 +/- 1.7 mmHg, p < 0.00001). The decrease in pulmonary artery pressure associated with inhalation of 2 ppm NO was only slightly less than the decrease associated with 10 ppm; the difference between the two was not considered to be clinically relevant. The pulmonary vascular resistance was significantly lower during inhalation of 2 ppm NO than during inhalation of room air only (495 +/- 40 vs 382 +/- 34 dyne.sec/cm5, p < 0.00001); the effects of inhaling 2 ppm and 10 ppm did not differ significantly. the partial pressure of oxygen in arterial blood was significantly lower after inhalation of 2 ppm NO than of baseline (61.1 +/- 2.3 vs 57.6 +/- 2.2 mmHg, p < 0.01). These results show that inhalation of NO worsens arterial oxygenation in patients with chronic obstructive pulmonary disease.

Administration, Inhalation↗
PubMed1997

[Inhaled budesonide for chronic obstructive pulmonary disease].

A significant, large minority of patients with chronic obstructive pulmonary disease (COPD) respond favorably to corticosteroid treatment; but the benefit may be outweighed by its side effects. Long-term administration of inhaled steroids is a safe means of treatment. We hypothesized that treatment with inhaled budesonide would improve clinical symptoms and pulmonary function in subjects with COPD, and that the response to an inhaled B2-agonist would individualize steroid responders. In 44 patients with stable COPD in a double- blind crossover trial, we compared a 6-week course of inhalations of 800 micrograms/d budesonide with a placebo, separated by a 4-week interval when no medication was taken. In 33 out of 42 responders to the B2-agonist who remained in the study, there was a significant improvement in FEV1 of greater than 20% following budesonide inhalation, as compared to placebo. There was also a significant difference between the 2 periods of treatment as to the mean number of B2-agonist inhalations. We conclude that about 1/4 of patients with stable COPD respond to bronchodilators, and treatment with inhaled steroids improves spirometry data and inhaled B2-agonist consumption in about 3/4.

Administration, Inhalation↗
PubMed1997

Inhaled nitric oxide as a selective pulmonary vasodilator in clinical anesthesia.

Inhaled nitric oxide (NO) is a selective pulmonary vasodilator in adult and pediatric patients. Inhaled NO diffuses into the pulmonary vascular smooth muscle where it results in vasodilation via stimulation of guanylyl cyclase. Systemic hemodynamics are not altered because inhaled NO is rapidly inactivated by hemoglobin. Oxygenation is also increased in certain patients as inhaled NO only vasodilates those segments of the pulmonary vasculature which are ventilated. There is growing evidence that inhaled NO may be a useful therapeutic agent in the treatment of pulmonary hypertension and hypoxemia from a variety of causes. Areas of greatest interest to anesthesia and critical care personnel may involve treatment of persistent pulmonary hypertension of the newborn (PPHN), adult respiratory distress syndrome (ARDS), and postoperative pulmonary hypertension secondary to cardiac disease. The potential toxicity of inhaled NO, particularly on immature and developing lungs, must be considered. While inhaled NO exerts acute beneficial effects, it is unclear if there are long-term benefits. Multicenter trials are currently underway to determine if inhaled NO decreases mortality from PPHN or decreases morbidity associated with ARDS.

Administration, Inhalation↗
PubMed1998

Inhaled nitric oxide in infants and children after open heart surgery.

OBJECTIVE: To assess the effects of inhaled nitric oxide (NO) on oxygenation and pulmonary circulation in infants and children with critical pulmonary perfusion and/or hypoxemia after open heart surgery. STUDY: A prospective case series report. SETTING: A multidisciplinary pediatric intensive care unit in a University hospital PATIENTS: From June 1993 to March 1996 37 pediatric patients after open heart surgery were treated with inhaled NO. Their mean age was 2.9+/-0.6 years, their mean body weight 12.6+/-1.8 kg. METHODS: Inhaled NO was applied using a microprocessor controlled delivery system which continuously measured NO and NO2 by the chemilumniscence method. Monitoring included ECG, continuous pulse oximetry (SaO2), arterial (AP), central venous (CVP) and left atrial (LAP) pressures and in 8 patients a pulmonary artery (PAP) pressure. Inhaled NO was started at an SaO2 <90% with a fraction of inspired oxygen concentration (FiO2) >0.7, at a mean pulmonary artery pressure (MPAP) >50% of the mean arterial pressure (MAP), and in patients after Fontan-procedure at a CVP-LAP pressure gradient >10 mmHg. RESULTS: The mean dose of inhaled NO was 3.7+/-0.3 ppm and the mean duration was 112+/-14.7 hours. For the whole group SaO2 increased from 79.6+/-2.3 to 90.1+/-1.5% (p<0.01) within 20 minutes of NO-inhalation. Inhaled NO significantly decreased the MPAP from 47.8+/-4 to 27.5+/-2.3 mmHg (p<0.01) in 8 patients with postoperative pulmonary hypertension and significantly decreased the transpulmonary pressure (CVP-LAP) from 14.3+/-0.8 to 7.3+/-0.9 mmHg (p<0.01) in 16 patients after Glenn- or Fontan-procedure. CONCLUSIONS: Inhaled NO is very effective to decrease pulmonary artery pressure, to improve oxygenation, and to improve Fontan-circulation in infants and children after open heart surgery.

Administration, Inhalation↗
PubMed1998

Paper spacers coupled to metered dose inhalers in family practice.

OBJECTIVES: 1. To assess the clinical efficacy of drug delivery using paper spacer devices coupled to metered dose inhalers (MDI). 2. To compare the effectiveness of paper spacers with the standard volumatic spacer. DESIGN: Randomised double-blind placebo controlled clinical trial. SETTING: Asthma clinic of a family practice at Kalutara. PATIENTS: 134 patients over 12 years of age, who attended the clinic with an acute episode of wheezing. METHOD: All patients over 12 years of age with an acute episode of wheezing who could speak a sentence of over 5 words were randomly allocated into 4 groups and administered salbutamol inhalations through a MDI coupled to a spacer. The first group used a 6-inch paper spacer, second group an 8-inch paper spacer, the third group a 10-inch paper spacer and the fourth group used a standard 750 ml volumatic spacer. MEASUREMENTS: In each subject, the peak expiratory flow rate (PFR) was recorded at the start, after placebo inhalation and after salbutamol inhalation. An increase of PFR of over 20% from the basal value was assessed as a good response. RESULTS: The number of patients who showed a good response after salbutamol inhalations in all four groups were very significant compared with the responses after placebo inhalations (p < 0.001). No significant differences were found in the effectiveness of salbutamol among the four other groups (p > 0.1). CONCLUSIONS: 1. All devices show equal efficacy. Metered dose inhalers and all 3 paper devices are as effective as the standard volumatic spacer. 2. The cost of a paper spacer device is negligible compared to that of the volumatic spacer. 3. The use of paper spacers in Sri Lankan family practices makes inhaled MDI therapy much cheaper without decreasing the effectiveness of drug delivery.

Administration, Inhalation↗
PubMed2007

Effective inhaled drug administration to mechanically ventilated patients.

Inhaled therapy is commonly employed in mechanically ventilated patients with chronic obstructive pulmonary disease or asthma. The efficacy of inhaled drugs is comparable to that achieved with systemic routes of administration, but the dose of drug required to achieve a therapeutic effect is generally much smaller. Moreover, limited systemic absorption of inhaled drugs minimises systemic side effects. Aerosol administration to ventilated patients differs from that in ambulatory patients in several respects. Optimal techniques for using pressurised metered-dose inhalers and nebulisers in ventilator circuits have been developed. With these techniques, the efficiency of inhaled drug delivery in mechanically ventilated patients is now comparable to that in ambulatory patients. Pressurised metered-dose inhalers are chiefly used to deliver bronchodilator and corticosteroid aerosols, and are more efficient and convenient to use than nebulisers for routine therapy in ventilated patients. However, nebulisers are more versatile and are employed to generate aerosols of bronchodilators, corticosteroids, antibiotics, prostaglandins, surfactant and mucolytic agents. Improvements in drug formulations and the design and efficiency of aerosol generating devices have led to increasing application of inhaled therapies in mechanically ventilated patients.

Administration, Inhalation↗
PubMed1993

Metered-dose inhalers. Do health care providers know what to teach?

OBJECTIVE: The specific aim of this investigation was to evaluate the proficiency of health care providers and patients in the proper use of metered-dose inhalers. DESIGN, SETTING, AND PARTICIPANTS: Health care providers, which include house staff, nurses, and respiratory care practitioners who provide care to patients with asthma in the primary general medicine clinic or the pulmonary medicine clinic of a university-county hospital in which patients were referred, were surveyed and assigned a performance score regarding the knowledge base of the appropriate use of metered-dose inhalers. Patients who attended the primary care general medicine and pulmonary subspecialty clinic were also assessed as to their proficiency in the use of metered-dose inhalers. RESULTS: A significant percentage of patients had a poor understanding of the technique used with the metered-dose inhaler. House staff and nursing staff were also less proficient in the proper use of the metered-dose inhaler. The respiratory care practitioners were the most knowledgeable of the health care providers. CONCLUSIONS: This study confirms that a large percentage of patients use metered-dose inhalers improperly. It also demonstrates a significant lack of understanding by health care providers of the proper use of metered-dose inhalers. Furthermore, this study supports the use of respiratory care practitioners in the outpatient setting, since they were the most proficient among all the health care providers in the proper use of metered-dose inhalers.

Asthma↗
PubMed2003

Inhaled long acting beta agonists for stable chronic asthma.

BACKGROUND: Asthma is a common respiratory disease among both adults and children and short acting inhaled beta-2 agonists are used widely for 'reliever' bronchodilator therapy. Long acting beta-2 agonists were introduced as prospective 'symptom controllers' in addition to inhaled corticosteroid 'preventer' therapy (ICS). OBJECTIVES: This review aimed to determine the benefit or detriment on the primary outcome of asthma control with the regular use of long acting inhaled beta-2 agonists compared with placebo. SEARCH STRATEGY: We carried out searches using the Cochrane Airways Group trial register, most recently in October 2002. We searched bibliographies of identified RCTs for additional relevant RCTs and contacted authors of identified RCTs for other published and unpublished studies. SELECTION CRITERIA: All randomised studies of at least two weeks duration, comparing a long acting inhaled beta-agonist given twice daily with a placebo, in chronic asthma. DATA COLLECTION AND ANALYSIS: Two reviewers performed data extraction and study quality assessment independently. We contacted authors of studies for missing data. MAIN RESULTS: Eighty five studies met the inclusion criteria, 56 parallel group and 29 cross over design. Salmeterol xinafoate was used as long acting agent in 60 studies and formoterol fumarate in 25. The treatment period was two to four weeks in 32 studies, and 12 to 52 weeks in 53 studies. 34 study groups used concurrent inhaled corticosteroid treatment, 21 studies did not permit their use and 35 permitted either inhaled corticosteroid or cromones. There were significant advantages to long acting beta-2 agonist treatment compared to placebo for a variety of measurements of airway calibre including morning peak expiratory flow (PEF) (weighted mean difference (WMD) 26.78 L/min 95%CI 20.36 to 33.20), evening PEF (WMD 19.17 L/min 95%CI 11.63 to 26.73). They were associated with significantly fewer symptoms, less use of rescue medication and higher quality of life scores. The risk of exacerbation was lower in adults using regular inhaled corticosteroids. REVIEWER'S CONCLUSIONS: Long acting beta-2 agonists are effective in the control of chronic asthma, and the evidence supports their use in addition to inhaled corticosteroids, as emphasised in current guidelines. Further research is needed on their use in children under 12 and in mild asthmatics not taking ICS.

Adrenergic beta-Agonists↗
PubMed2004

Effect of design on the performance of a dry powder inhaler using computational fluid dynamics. Part 1: Grid structure and mouthpiece length.

This study investigates (1) the effect of modifying the design of a dry powder inhaler on the device performance, and (2) which design features significantly contribute to overall inhaler performance. Computational Fluid Dynamics (CFD) analysis was performed to determine how the flowfield generated in an Aerolizer at 60 l min(-1) varied when the inhaler grid and mouthpiece were modified. The computational models were validated by Laser Doppler Velocimetry (LDV). Dispersion performance of the modified inhalers was measured with a mannitol powder using a multistage liquid impinger at 60 l min(-1). The inhaler grid was found to significantly affect the performance of the Aerolizer. As the grid voidage was increased, the amount of powder retained in the device doubled (due to increased tangential flow of particles in the inhaler mouthpiece) and the FPF(Loaded) was reduced from 57 to 44% (due to increased mouthpiece retention). The length of the mouthpiece played a lesser role on the inhaler performance, having no significant effect on the flowfield generated in the devices. In summary, the performance of a dry powder inhaler can be affected by simple design changes. CFD, coupled with experimental results, provides a rational basis for understanding the performance difference.

Drug Delivery Systems↗
PubMed1986

Prediction of drug residence times in regions of the human respiratory tract following aerosol inhalation.

A mathematical model was developed for predicting drug residence kinetics in various regions of the human respiratory tract (RT). The model allows for regional deposition of different dose fractions (following mouth inhalation of various particle sizes according to four popular breathing regimes). Predicted alveolar deposition was dependent on the mode of inhalation and breath-holding. Deposition in the ciliated airways, however, was largely unaffected by breath-holding and was at a maximum for aerodynamic diameters between 5-9 micron (slow inhalation) and 3-6 microns (fast inhalation). Selected mucociliary and absorption rate constants determined the durations (T) taken to deplete the initial deposition in a chosen lung region to a selected minimum dose fraction (MDF). Values of T for an MDF of 0.01 in the ciliated airways were dependent on aerosol size, mode of inhalation, and rate of dissolution. In the case of rapidly dissolving solutes, the maximum duration was short (1-2 h) and occurred at particle sizes and modes of inhalation which maximized deposition in the conducting airways. For less soluble particles, however, T in the same airways could approach 12 h due to a prolonged supply of particles from the alveolar regions. The optimal size distribution and the mode of inhalation for maximum duration differed substantially in each case. The model enables formulation of testable hypotheses relating to the extension of local drug residence in the RT following inhalation of therapeutic aerosols.

Absorption↗
PubMed1994

Assessment of the ability of young children to use a powder inhaler device (Turbuhaler).

The purpose of the study was to determine the age at which young asthmatic children could master the use of a new powder inhaler device (Turbuhaler). We studied 59 children with asthma between the ages of 3 and 6 years who consecutively attended the asthma clinic of the pediatric department. Efficiency of inhalation and the pharmacological effect of the terbutaline in the inhaler were measured by scores for inhalation technique and clinical response. None of the 3-year-old children used the device efficiently, but 43% of the 4-year-old, 67% of the 5-year-old, and 80% of the 6-year-old children used the inhaler correctly. Although inhaler technique was not perfect in the younger age group, 50% of the 3-year-old children demonstrated clinical improvement of asthma symptoms after inhalation. In the older age groups, 79%, 92%, and 100% of the 4, 5, and 6-year-old children demonstrated clinical improvement of asthma symptoms after inhalation. It is concluded that the new mode of dry powder delivery system (Bricanyl Turbuhaler) can be used in young asthmatic children who are 4 years of age and above.

Age Factors↗
PubMed1979

A blood cyanide distribution study in the rabbits intoxicated by oral route and by inhalation.

Blood cyanide concentration was determined in rabbits intoxicated orally or by inhalation. Experiments were carried out under urethane anaesthesia. In the inhalation experiments, rabbits inhaled a combustion product containing HCN via the tracheal cannula and in the oral studies animals were administered NaCN solution into the stomach. In addition to the carotid artery and jugular vein blood samples, postmortem samples were obtained from both sides of the heart and the descending vena cava. The arterial cyanide concentration in the inhalation group showed a close relationship with ventilation. After an initial rise, blood levels decreased a little, in some cases with transient apnea. At the last stage it again increased with gasping, reaching its maximal value. After ultimate apnea, the blood cyanide concentration declined. The blood cyanide values were higher in the oral group than in the inhalation group. The difference between the two groups became larger in the inferior order, the left heart blood--the right heart blood--blood in the descending vena cava. The left heart/right heart ratio of the inhalation group was significantly higher than that of the oral group (1.28+/- 0.28 vs. 0.95+/- 0.09). The coefficient of variation (c.v.) of the inhalation group was larger than that of the other group. Within the inhalation group, the left heart blood showed the largest c.v. values and this was probably due to redistribution of the cyanide by bloodstream after attainment of the maximal concentration.

Administration, Oral↗
PubMedDate not supplied

The effect of a combination of inhaled nitric oxide and an endothelinA-receptor antagonist on hemodynamic dysfunction in experimental acute pulmonary thromboembolism.

Although either inhaled nitric oxide (NO) or endothelinA receptor antagonist has been tried in the treatment of various forms of pulmonary hypertension, the effects of combination therapy have not been reported. We evaluated the effects of inhaled NO alone or a combination of inhaled NO and ZD2574 (an endothelinA receptor antagonist) in an experimental canine acute pulmonary thromboembolism model. Forty parts per million of inhaled NO alone, or a combination of inhaled NO and 10 mg/kg of ZD2574 was administered 1 hour after embolization with an autologous blood clot. We compared the hemodynamic and gas exchange parameters between the two treatment groups. Two treatment regimens decreased mean pulmonary arterial pressure and pulmonary vascular resistance and attenuated decrease in cardiac output. Moreover, systemic arterial hypotension or worsening of hypoxemia did not occur in either of the treatment groups. In the combined group, more favorable hemodynamic outcomes were maintained than in the inhaled NO alone group. And hemodynamic deterioration shown after NO withdrawal was attenuated in the combined group. These findings suggest that when inhaled NO is concomitantly administered with an ETA receptor antagonist, more favorable hemodynamic outcomes can be expected during and after NO inhalation in acute pulmonary thromboembolism.

Animals↗
PubMed1994

What do pediatricians in training know about the correct use of inhalers and spacer devices?

Most patients with asthma in the United States are cared for by nonspecialist physicians. Because inhaled medications are the mainstay of asthma therapy and their successful use requires both practical skills and theoretic knowledge, we wondered how much nonspecialist physicians know about the use of metered-dose inhalers and spacer devices. Fifty pediatricians in training were interviewed individually. Practical knowledge was assessed by asking each to demonstrate correct use of a placebo inhaler and a spacer device (Inspirease [Key Pharmaceuticals, Inc., Miami, Fla.] and Aerochamber with mask [Monaghan Medical Corp., Plattsburgh, N.Y.]). Of the seven recommended steps for use of metered-dose inhalers, the residents demonstrated an average of 3.8 steps correctly. The most common errors included not shaking the metered-dose inhaler before use (18% of residents correct) and insufficient breath holding (28% correct). In testing spacer use, the most common errors included not shaking the canister (16% correct) and incorrect number of activations and inhalations (12% correct). Many residents were not familiar with correct assembly of the spacer (48% correct). Theoretic knowledge of metered-dose inhaler and spacer use was evaluated by a written questionnaire. The most common deficiencies in theoretic knowledge related to the purpose of slow inspiration and breath holding. Most of the participants had been treating children with asthma and had prescribed metered-dose inhalers (45 of 50, 90%) and spacer devices (76%) in the past.(ABSTRACT TRUNCATED AT 250 WORDS)

Equipment Design↗
PubMed1992

Effect of inhaled terbutaline sulphate in relation to its deposition in the lungs.

We studied the effects of inhaled terbutaline on FEV1 and gas exchange, and the pattern of deposition within the lungs. To document this and to estimate the dose of terbutaline administered to the lungs, [99mTc]DTPA was added to nebulised terbutaline solution. The aerosol was deposited preferentially in large or small airways by using aerosols with different particle mass median diameters (1.5 and 4.8 microns) and different inhalation flow rates (0.25 and 1.0 l/s). The patients inhaled placebo and then three increasing doses of terbutaline (0.006, 0.02 and 0.08 mg to the lungs). Finally, 2 mg terbutaline was inhaled from a metered dose inhaler via a spacer. After each inhalation FEV1, PaO2 and PaCO2 was measured. The inhalation of small particles at a low flow resulted in a fairly uniform lung deposition, while larger particles at a higher flow resulted in heavy central deposition. Penetration index for small and large particles were 1.3 +/- 0.2 and 0.8 +/- 0.3 (P less than 0.001), respectively. In both groups FEV1 increased similarly with each dose, and at 0.02 and 0.08 mg the increase was significant (P less than 0.01). After eight metered doses of terbutaline sulphate (0.25 mg per dose) inhaled via a spacer, there was a further increase in FEV1 (P less than 0.001). Gas exchange did not differ between the two groups but if they were combined the DA-aO2 was significantly lower after metered doses than control (P less than 0.05). Thus, it appears that the site of deposition is not important for the bronchodilator effect of terbutaline, and gas exchange tended to improve with both modes of administration.

Adult↗
PubMed2004

Adjustable maintenance dosing with budesonide/formoterol in a single inhaler provides effective asthma symptom control at a lower dose than fixed maintenance dosing.

Asthma guidelines suggest a stepwise approach to maintenance pharmacological treatment of persistent asthma until control is attained, and a 3 month review of the fixed maintenance dosing for step-up or step-down adjustment. This 12-week study compared the efficacy and safety of budesonide/formoterol in a single inhaler (Symbicort Turbuhaler 160/4.5 or 80/4.5 microg) given as adjustable maintenance or fixed maintenance dosing. Patients (n = 2358) were randomised to budesonide/formoterol fixed maintenance dosing (two inhalations bid) or adjustable maintenance dosing (two inhalation bid; stepping up to four inhalations bid if asthma worsened for a maximum of 14 days; stepping down to two inhalations once nocte or one inhalation bid if symptoms were controlled) for 12 weeks, following a 4-week run-in period on budesonide/formoterol two inhalations bid. Primary efficacy variables were frequency of asthma exacerbations and changes in patients' asthma symptom severity. Secondary variables were asthma control, safety and health economics. Both adjustable maintenance dosing and fixed maintenance dosing were associated with similar low frequency of exacerbations (5% both groups; ns) and similarly improved lung function, with similarly fewer nocturnal awakenings and less asthma symptoms compared with the mean value of the run-in period. However, patients on adjustable maintenance dosing used 24% fewer study drug compared with fixed maintenance dosing (2.95 versus 3.86 inhalations daily; p < 0.0001) and incurred in a significant (p <0.0001) reduction in total costs (direct+indirect) compared with fixed maintenance dosing. In conclusion, adjustable maintenance dosing with budesonide/formoterol effectively controls asthma at a reduced drug load with lower costs than fixed maintenance dosing.

Adult↗
PubMed1998

The biopersistence and pathogenicity of man-made vitreous fibres after short- and long-term inhalation.

A summary is given of the biopersistence and pathology after inhalation by rats of two different Man-made Vitreous Fibres, MMVF21 (traditional stone wool) and MMVF34 (HT stone wool), and the results are discussed in relation to biopersistence measured after intra-tracheal instillation. The results are given from a short-term inhalation biopersistence study, a completed chronic inhalation study, and interim results from an on-going chronic inhalation study. In both the short-term and chronic studies, laboratory rats were exposed by nose-only inhalation to well-characterised fibre test atmospheres that had been selected to be largely rat respirable. The short-term inhalation study included groups exposed to aerosols targeted at 150 fibres longer than 20 microns per cm3. The exposure duration was 6 hours/day for 5 days, with subsequent post-exposure periods lasting up to 12 months. For lung burden analyses, interim sacrifices were performed at regular intervals. The ongoing chronic study comprises a group of rats exposed to the MMVF34 fibre at one exposure level of 30 mg/m3. The negative control group is filtered air. The exposure duration is 6 hours/day, 5 days/week for 2 years, with a subsequent post-exposure period lasting until approximately 20% survival in the test fibre group. Interim sacrifices are performed at months 3, 6, 12, 18 and 24 and biopersistence monitored for rats exposed for 3 and 12 months, with subsequent post-exposure periods lasting 6 months. Effectively the main protocol for the previously conducted chronic study was the same, except that there were 3 fibre exposure groups (3, 16 and 30 mg/m3) and no specific biopersistence satellite groups were included. For MMVF34, the inhalation tests of different duration show a similar biopersistence pattern, while the intra-tracheal test gives longer elimination half-times especially for long fibres. The MMVF34 fibre is considerably less biopersistent than the traditional MMVF21 fibre when comparing the calculated elimination half-times after short-term inhalation. When comparing the pathology after 3, 6, 12 and 18 months exposure, MMVF34 showed minor histopathological changes compared to MMVF21. The carcinogenicity and toxicity results of the chronic study with MMVF21 suggest that this fibre does not pose a significant health risk to humans and the current results with MMVF34 indicate that this fibre consequently should pose an even smaller risk, if any.

Aerosols↗