A mathematical model of aerosol delivery from holding chambers (spacers) was developed incorporating tidal volume (VT), chamber volume (Vch), apparatus dead space (VD), effect of valve insufficiency and other leaks, loss of aerosol by immediate impact on the chamber wall, and fallout of aerosol in the chamber with time. Four ...

Inspiratory flow profiles through a novel dry powder inhaler (DPI) (Clickhaler; Innovata Biomed Ltd, St. Albans, UK) were recorded in 17 pediatric patients (aged 7-16 years) with stable mild to moderate asthma. Most patients (n = 14) could generate high peak inspiratory flows (PIFs) (> 60 L/min) and high flows ...

According to data reported in literature tidal breathing parameters and especially tidal expiratory flow pattern parameters can be useful in distinguishing airflow obstruction. The purpose of the present study was to investigate the parameters of the tidal breathing in healthy people and patients with chronic obstructive pulmonary disease. The study ...

There is limited knowledge about which internal and external factors influence respiratory effects of occupational endotoxin exposure. Relationships between endotoxin exposure, work-related respiratory symptoms, and acute peak flow changes were studied in 97 shift workers in the potato processing industry. For each worker, across-shift peak flow changes were determined for ...

Simultaneous measurement of input (Zin) and transfer impedances (Ztr) allows separation of airway and tissue properties at a single frequency, without making assumptions concerning the structure of the two compartments. This approach offers the possibility of studying the variation in airway impedance (Zaw) during the respiratory cycle. Zin and Ztr ...

The prescription of hyperbaric oxygen (HBO) therapy for disorders not related to diving is increasing. Pulmonary oxygen toxicity is well known, but the effect of the cumulative oxygen exposure corresponding to a standard HBO treatment protocol has not been quantified before. Twenty patients (10 male) had 21 HBO treatments at ...

STUDY OBJECTIVE: To determine whether changes of partial expiratory flow-volume curve (PEFV) and inspiratory capacity (IC) detect functional responses to bronchodilator in patients who do not meet the FEV1 criteria for reversibility of airway obstruction. DESIGN/METHODS: The effects of salbutamol (200 microg by metered-dose inhaler) on lung function were examined ...

Expert judgment of peak flow-time graphs provides an important tool to detect occupational asthma. This technique has mainly been used in clinics to evaluate reversible airflow obstruction and to assess potential work-related patterns. The reproducibility of this technique in an open working population is unknown. Agreement between and within nine ...

An index obtained from tidal expiration, the ratio of time to peak tidal expiratory flow (tPTEF) to expiratory time (tE), discriminates between groups with and without airflow obstruction in infants and children and correlates with other measurements of airflow obstruction in adults. The aim of this study was to determine ...

BACKGROUND: The American Thoracic Society (ATS) has set the acceptable resistance for spirometers at less than 1.5 cm H2O/l/s over the flow range 0-14 l/s and for monitoring devices at less than 2.5 cm H2O/l/s (0-14 l/s). The aims of this study were to determine the resistance characteristics of commonly ...

Earlier studies have shown that time and flow indices derived from tidal expiratory flow patterns can be used to distinguish the severity of airway obstruction. This study was designed to address two aspects of tidal expiratory flow patterns: 1) how do expiratory flow patterns differ between subjects with normal and ...

Home peak expiratory flow (PEF) measurements have become the cornerstone of asthma self-management plans. However, the cut-off values for changing treatment have not been formally tested. This study focusses on the possible overtreatment brought about by the different cut-off values and denominators currently employed. Data from 133 clinically stable asthmatic ...

BACKGROUND: The usefulness and safety of the analysis of blood inflammatory markers in asthma are widely recognized. Recently, the analysis of induced sputum has been proposed as a safe, non-invasive tool in the study of airway inflammation in asthma. OBJECTIVE: Our aim was to test whether sputum analysis is more ...

STUDY OBJECTIVE: To define the effect of changes in body posture on flow-volume loops (FVLs) and four commonly used indices of upper airway obstruction (UAO) in young, nonobese normal subjects. DESIGN: Prospective comparative study. SETTING: Pulmonary function laboratory at an academic hospital. PARTICIPANTS: Thirty-one normal volunteers. INTERVENTION: At least three ...

To define the standard of airway flow limitation, pharyngeal pressure and flow rate were measured during wakefulness and sleep in seven habitual snorers with widely varying degrees of sleep-induced increases in upper airway resistance. Inspiratory pressure:flow relationships were used to group breaths into four categories of flow limitation, including linear ...

BACKGROUND: Expiratory flow rate, soft palate closure, and dead space air may influence exhaled levels of nitric oxide (NO). These factors have not been evaluated in the reservoir collection of NO. METHODS: Exhaled NO was collected into a reservoir during a single flow and pressure controlled exhalation. RESULTS: NO collected ...

Flow in a symmetric bifurcation model of analytically known geometry was investigated experimentally under oscillatory flow conditions. The duration of the inspiratory and expiratory phases were set to be equal during the oscillatory period. A two velocity component laser Doppler anemometer was used to interrogate the flow field. Three different ...

OBJECTIVE: To evaluate the effects of pharyngeal gas insufflation (PGI) in clinically stable patients with chronic obstructive pulmonary disease (COPD). DESIGN: Prospective study in humans. SETTING: Department of Intensive Care Medicine at a University Hospital. PATIENTS: Seven clinically stable COPD patients. INTERVENTION: Pharyngeal dry fresh air insufflation (PGI) with a ...

This paper reports the results of spirometric studies done in the state of Gujarat in view of deriving the ventilatory norms. The study included a total of 2000 healthy nonsmoker individuals with 1369 males and 631 females. The study was done over the period from September, '92 to July, '93. ...

The purpose of this study was to evaluate the influence of velocity of shortening on the relationship between diaphragm activation and pressure generation in humans. This was achieved by relating the root mean square (RMS) of the diaphragm electromyogram to the transdiaphragmatic pressure (Pdi) generated during dynamic contractions at different ...

The aim of this study was to assess the accuracy and applicability of a portable electronic peak flow meter combined with an asthma monitor (AM1, Jaeger, Germany) which measures peak expiratory flow (PEF), forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). The technical accuracy in PEF, ...

Researchers disagree about whether exposure to asbestos causes significant respiratory impairments and airway obstruction in the absence of radiographic asbestosis and smoking. To obtain confirmatory information, the authors examined pulmonary function of 208 nonsmoking female asbestos workers who did not have asbestosis and 136 controls. The authors observed an overall ...

As an inflammatory airway disease, asthma is expected to be associated with an increase in airway blood flow. We therefore compared airway mucosal blood flow (Qaw) among normal subjects (n = 11) and patients with stable asthma receiving (n = 13) or not receiving (n = 10) long-term inhaled glucocorticosteroid ...

Upper airway obstruction is an important but often unrecognised cause of dyspnoea and ventilatory failure. Flow volume loop remains the most sensitive method to detect upper airway obstruction. We report a patient with Hashimoto's thyroiditis who showed evidence of upper airway obstruction on the flow volume loop only in the ...

Nitric oxide (NO) of endogenous origin is present in exhaled breath. An increase in exhaled NO concentration (ENO) has been described in bronchial asthma and ENO falls after inhaled steroid therapy. The sources of ENO may include pulmonary blood, the gas exchange region, conducting airways and the nasal cavity. In ...

Goiter is a common condition and can cause upper airway obstruction (UAO), which may be difficult to detect. We have studied maximal expiratory and inspiratory flow volume loops using a neural network to see if this offers a better way to identify patients with UAO. The flow-volume loops from 155 ...

OBJECTIVE: Tracheal gas insufflation (TGI) is considered an adjunctive method to enhance carbon dioxide elimination during permissive hypercapnia in patients with acute respiratory distress syndrome. Due to increasing tidal volume and/or expiratory resistance, TGI may cause intrinsic PEEP (PEEPi), and may lessen the advantages of permissive hypercapnia. There is no ...

Tumour necrosis factor alpha (TNF alpha) is increased in patients with cardiac cachexia, a condition associated with reduced peripheral blood flow both at rest and after interventions causing vasodilation. By contrast, in patients with chronic heart failure (CHF), higher TNF levels are associated with a greater capacity for vasodilation in ...

OBJECTIVES: In neurogenic dysphagia a good cough is important for airway protection. If triggering of cough, or its effectiveness, is impaired this might result in an increased aspiration risk. Capsaicin, an agent which induces cough through sensory nerve stimulation, was used to test cough sensitivity in groups of patients with ...

The acute and subacute effects of ambient concentrations of ozone on lung function have been studied extensively in a variety of settings. Such studies generally have focused on measures of function that reflect either lung volumes or flows that are influenced by the physiology of large and small airways (e.g., ...

Ambulatory peak flow monitoring plays an important role in the diagnosis and management of patients with bronchial asthma. Today several kinds of portable peak flow meters (PFMs) are available for this purpose and sometimes comparisons between the readings of different kinds of PFMs are necessary in clinical setting. We compared ...

Recently, we reported a reproducible model of asthma in guinea-pigs in vivo, which developed a late asthmatic response (LAR) as well as an early response. In this study, time-related changes in the occurrence of the LAR and leucocyte kinesis were assessed. Furthermore, the state of the activation of eosinophils that ...

OBJECTIVES: The study was conducted to ascertain whether physical education teachers, using a peak flow meter, could reliably screen for exercise-induced asthma (EIA) in children during free running. DESIGN, SETTING AND SUBJECTS: The study was conducted using a convenience sample of male pupils between the ages of 12 and 18 ...

Lung volume reduction surgery (LVRS) is a promising new treatment for emphysema and leads to increased flow rates. We investigated the mechanisms by which flow rates could increase and the correlates of lessened dyspnea in patients undergoing LVRS before and 3 months after LVRS in patients with severe emphysema. The ...

This study hypothesizes that: peak supramaximal airflow during cough reflects expiratory muscle effort, and that expiratory muscle function during cough might be assessed from the airflow signal alone. We monitored airflow and oesophageal pressure (Poes) in normal subjects during cough generated under two conditions: 1) voluntarily from functional residual capacity ...

Peak expiration flow records from patients allergic to house-dust mites (Dermatophagoides spp.) may show a characteristic variation from week to week due to the general life cycle of these mites in dwellings. This was demonstrated from the combined records of 10 patients recorded in their own homes, covering a period ...

The influence of the endotracheal tube (ETT) during a T-piece trial remains controversial. Our aim was to compare the work of breathing of 14 successfully extubated patients at the end of a 2-h trial (T) and after extubation (E) of the trachea, and to assess, using the acoustic reflection method, ...

We compared "miniWright" peak flow (mWPF) readings with spirometric peak expiratory flow rates (PEFR) in 91 children, aged 8-15, exposed to ambient air at a summer camp in northwestern New Jersey. mWPF measurements immediately preceded spirometry, and mWPF-PEFR differences were regressed on spirometric PEFR by child. The ratio (mWPF-PEFR)/PEFR (mean ...

Two methods of defining perception of asthma-related changes in airflow were compared, and relationships to clinical opinions of severity and assessments of psychological functioning were investigated. Perceived breathlessness (VAB) and peak expiratory flow (PEF) were recorded by 100 subjects for 28 days. Perception was defined by correlation of the two ...

Although experiment and computer analysis of zone-circulating flow injection analysis (ZCFIA) data have been investigated, there are still some essential problems inherent to ZCFIA. Computer program of high dimensional modified simplex method was used for resolving peaks of ZCFIA damped response curves. Peaks are resolved on the basis of the ...

Recording of respiratory airflow is an integral part of polysomnography (NPSG). It is conventionally monitored with a thermistor that measures temperature as a surrogate of flow. The subjectivity of interpreting hypopnea from this signal has prompted us to measure nasal airflow directly with a simple pneumotachograph consisting of a standard ...

Chemical exposure may result in respiratory conditions such as chronic bronchitis, bronchial hyperresponsiveness, and chronic airway obstruction. Clinical studies have shown that during the course of disease, cytokine networks are changed. In order to study the relationship between blood cytokines and respiratory symptoms in an occupational setting, we investigated 106 ...

The degree of rebreathing in Mapleson A, C and D breathing systems for sinusoidal and exponential flow waveforms is analysed mathematically. The effects of altering the I:E ratio and of introducing an expiratory pause are investigated. The results for sinusoidal waveforms closely resemble those for a square wave. Exponential flow ...

It has been demonstrated by a lot of clinical practice and experimental research that blood stasis is present in cases of asthma. In regard to the manifestations of asthma with blood stasis, medical doctors in our country carried out many investigations. The symptoms and signs of the disease are recognized ...

Cyclosporine A (CsA) in liposomes of dilauroylphosphatidylcholine (DLPC), containing 118 micrograms of CsA/L of aerosol with a particle size of 1.6 to 1.7 micron diameter, was inhaled by 10 nonsmoking, normal volunteers each for 45 min. Aerosol was administered through an Aerotech II nebulizer (CIS-US, Inc., Bedford, MA) mouthpiece. Eight ...

The clinical usefulness of inspiratory flow pattern manipulation during mechanical ventilation remains unclear. The aim of this study was to investigate the effects of different inspiratory flow waveforms, i.e. constant, sinusoidal and decelerating, on arterial blood gases and respiratory mechanics, in mechanically ventilated patients. Eight patients recovering after open heart ...

It has recently been shown (O. F. Pedersen T. R. Rasmussen, O. Omland, T. Sigsgaard, P. H. Quanjer. and M. R. Miller. Eur. Respir. J. 9: 828-833, 1996) that the added resistance of a mini-Wright peak flowmeter decreases peak expiratory flow (PEF) by approximately 8% compared with PEF measured by ...

The purpose of this study was to examine whether peak expiratory flow is determined by the wave-speed flow-limiting mechanism. We examined 17 healthy subjects and 11 subjects with stable asthma, the latter treated with inhaled bronchodilators and corticosteroids. We used an esophageal balloon and a Pitot-static probe positioned at five ...

Several in vitro and in vivo studies have emphasized the importance of generating a high inspiratory flow when using a dry powder inhaler. Little attention has been paid to the influence of the inspiratory flow profile on the particle size distribution contained in aerosols generated by these devices. The internal ...

This paper presents measurements of the geometric shape, perimeter, and cross-sectional area of the human oral passage (from oral entrance to midtrachea) and relates them through dimensionless parameters to the depositional mass transfer of ultrafine particles. Studies were performed in two identical replicate oral passage models, one of which was ...