Forced Mid-expiratory Flow Research Articles

Effects of a standard hyperbaric oxygen treatment protocol on pulmonary function.

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 a partial pressure of oxygen of 240 kPa for 90 min daily. None had any previous lung disease and all had normal chest radiography and lung function at the start of the study. Dynamic lung volumes, forced expiratory flows and the transfer factor of the lung for carbon monoxide (TL,CO) were measured before the HBO treatment, on days 7, 14 and 21 during treatment and then 3-4 weeks after treatment. Four patients (one male) reported nonproductive coughing during the last week of treatment. There was a progressive reduction in forced expiratory volume in one second (FEV1) (p<0.001), mean forced mid-expiratory flow rate (FEF25-75%) (p<0.001) and forced expiratory flows at 50 and 75% of forced vital capacity (FVC) expired during HBO treatment. The reduction in FEV1 on day 21 was 4.4+/-1.7% and in FEF25-75% 10.3+/-6.1%. Four weeks after treatment there was a partial normalization. There were no changes in FVC or peak expiratory flow (PEF). TL,CO was slightly reduced on day 21 of treatment only (p<0.01) and fully normalized 1 month later. A reduction in small airways conductance is consistent with other studies where total oxygen exposures have been below the limit causing toxic pulmonary effects traditionally measured as a reduction in vital capacity. This effect is not considered to be of any clinical significance for patients treated with hyperbaric oxygen unless repeated treatment series are to be given.

Effect of breathing circuit resistance on the measurement of ventilatory function

BACKGROUNDThe 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...

Effects of airway calibre on lung delivery of nebulised salbutamol.

BACKGROUND: A study was undertaken to test the hypothesis that airway calibre may alter lung deposition and therefore lung bioavailability of inhaled drugs as a result of narrowed airways reducing...

Experience with living-donor lobar transplantation for indications other than cystic fibrosis

Objective: Since development of a living donor bilateral lobar transplantation protocol for patients with cystic fibrosis, our indications have expanded to include recipients with other diagnoses. Methods: We report on our experience in eight patients with primary pulmonary hypertension, postchemotherapy pulmonary fibrosis, bronchopulmonary dysplasia, idiopathic pulmonary fibrosis, and obliterative bronchiolitis. The average age of the eight patients was 19.1 years (range 9 to 40). The mean preoperative carbon dioxide tension for the four patients who did not have primary pulmonary hypertension was 92 mm Hg (range 64 to 120 mm Hg), and the two patients with pulmonary fibrosis were intubated (one on high-frequency jet ventilation). Each recipient received a right lower lobe ( n = 7) or middle lobe ( n = 1) and a left lower lobe ( n = 8) from a total of 16 donors representing various combinations of the recipient's family ( n = 15) and an unrelated friend ( n = 1). Results: With an average follow-up of 1 year the overall survival is 75%. For the five patients followed up for at least 1 year, mean forced vital capacity was 80.6%, forced expiratory volume in 1 second was 75.6%, mid-forced expiratory flow was 64%, and diffusing lung capacity corrected for alveolar volume was 73% of predicted. For those patients with primary pulmonary hypertension, preoperative hemodynamics revealed mean pressures as follows: blood pressure 84.8 mm Hg, right atrial pressure 7.8 mm Hg, pulmonary artery pressure 71.3 mm Hg, pulmonary capillary wedge pressure 9.5 mm Hg, cardiac index 2.9 L/min per square meter, and pulmonary vascular resistance index 22.8 Wood units. Postoperative hemodynamics revealed a mean blood pressure of 84.3 mm Hg, right atrial pressure of 2.7 mm Hg, pulmonary artery pressure of 16 mm Hg, pulmonary capillary wedge pressure of 7.3 mm Hg, cardiac index of 4.2 L/min per square meter, and pulmonary vascular resistance index of 1.9 Wood units. Conclusions: Early results of living-donor bilateral lobar transplantation for diseases other than cystic fibrosis have resulted in satisfactory survival and pulmonary function. Additionally, patients with severe primary pulmonary hypertension have had dramatic normalization of their hemodynamics despite the limited amount of lung tissue transplanted. We believe that the data from this small cohort experience compares favorably with our larger series with cystic fibrosis and supports an expanded role for living-donor lobar transplantation in patients with alternate indications. (J Thorac Cardiovasc Surg 1997;114:917-22)

Adrenocortical activity with repeated twice daily dosing of fluticasone propionate and budesonide given via a large volume spacer to asthmatic school children.

BACKGROUND: In a previous single dosing study in asthmatic school children fluticasone propionate produced significantly greater suppression of overnight urinary cortisol excretion than budesonide at high doses of 800 micrograms/day...

Role of pulmonary function in the detection of allograft dysfunction after heart-lung transplantation.

BACKGROUND: Lung function is altered by infection and rejection in patients who undergo heart-lung transplantation. The sensitivity, specificity, and positive/negative predictive values (PPV and NPV) of lung function for the...

Adrenal suppression with chronic dosing of fluticasone propionate compared with budesonide in adult asthmatic patients.

BACKGROUND: In a previous single dosing comparison between fluticasone propionate and budesonide differences in cortisol levels measured at 08.00 hours were observed at doses in excess of 1000 micrograms. The...

Contribution of hyperoxia to reduced pulmonary function after deep saturation dives

Pulmonary function was measured before and after a 28-day saturation dive to a pressure of 0.25 MPa in eight subjects. PO2 was 40 kPa, with periods of 75 kPa for 2 h every 2nd day during the first 14 days, 50 kPa for the next 12 days, and a gradual fall to 21 kPa over the last 2 days in decompression. A 28-day saturation dive with six subjects to a pressure of 0.15 MPa and a PO2 of 21 kPa was used as control. The measurements included static and dynamic lung volumes and flows, transfer factor for carbon monoxide (TLCO), and a cycle ergometer exercise test. There was a significant reduction in TLCO of 9.8 +/- 6.0% (P < 0.001) after the dive when values were corrected for hemoglobin concentration changes. Effective alveolar volume was unchanged. There was a reduction in forced midexpiratory flow rate of 9.8 +/- 7.0% (P < 0.01), but forced vital capacity and forced expired volume in 1 s were unchanged. Peak oxygen uptake was reduced by 10.1 +/- 5.3% (P < 0.001). There were no significant changes in any of the lung function variables after the control dive. Exposure to raised PO2 contributes significantly to the changes in pulmonary function that have been reported after deep saturation dives to pressures of 3.1-4.6 MPa with a similar profile of oxygen exposure. TLCO is apparently a more sensitive index than vital capacity for oxygen toxicity.

Detrimental effect of hypotonic cromolyn sodium

In a randomized, double-blind, placebo-controlled, crossover study, inhalation of the commercially available nebulized form of cromolyn sodium resulted in a significant decrease in forced midexpiratory flow rate between the 25th and 75th percentile points, equivalent to that observed for distilled water, in children with chronic asthma. We conclude that inhalation of the current hypotonic concentration of cromolyn sodium may be detrimental.

Pulmonary function and symptoms in workers exposed to wood dust.

Exposure to wood dust can cause a variety of lung problems, including chronic airflow obstruction. Forced vital capacity (FVC), forced expiratory volume in one second (FEV1), forced expiratory ratio (FEV1/FVC x 100), forced expiratory flow (FEF), forced mid expiratory flow (FMF), peak expiratory flow (PEF), and respiratory symptoms (cough, phlegm, breathlessness, wheezing, and nasal symptoms) were recorded in 145 non-smoking workers (77 male, 68 female) exposed to wood dust in a furniture factory in Umtata, Republic of Transkei, and 152 non-smoking control subjects (77 male, 75 female) from a bottling factory with a clean environment. After adjustment for age and standing height the forced expiratory indices were significantly lower in the exposed male workers than in the control subjects. FEF and PEF in the exposed men were 81.3% and 89.4% of predicted values and were lower than other indices. FVC in exposed men showed a significant inverse correlation with exposure (expressed in number of years of employment). The FVC was reduced by 26 ml per year of employment. The proportion of men with an FEV1/FVC below 70 was higher in exposed workers than in control subjects and higher in the exposed workers with more years of employment. The exposed workers had more respiratory symptoms than the control subjects, the prevalence, especially of cough and nasal symptoms, increasing with the increase in the number of years of employment. Workers exposed to pine and fibre dust have more respiratory symptoms and a greater risk of airflow obstruction.

Lung function and immunopathological changes after inhaled corticosteroid therapy in asthma

Six patients with asthma (American Thoracic Society (ATS) criteria), maintained on inhaled beta 2-agonists alone, were treated with inhaled corticosteroid (budesonide 400 micrograms b.d.) for a period of three months. Prior to steroid therapy, baseline spirometry, bronchodilator response and bronchial hyperresponsiveness were documented and endobronchial biopsies were obtained for immunopathological analysis. Frozen sections of the biopsies were investigated using immunoperoxidase methods, with a panel of monoclonal antibodies selected to reveal the presence and distribution of lymphocyte and macrophage subsets and HLA-DR expression. After three months the studies were repeated. Studies before steroid therapy revealed a T-cell-dominated inflammation in the bronchial wall of all subjects. Baseline airway obstruction, median (range) forced expiratory volume in one second (FEV1) 78.5 (61-109)% of predicted, with a significant bronchodilator response 20.8 (14-33)% and bronchial hyperresponsiveness to histamine geometric mean (SD) PC20FEV1 0.69 (2.5) mg was documented. Steroid therapy caused a significant reduction in bronchial hyperresponsiveness to histamine, with an increase in geometric mean PC20FEV1 to 2.22 (3.2) mg post steroid (p less than 0.03). Concurrent with a reduction in bronchodilator response and an increase in spirometric variables (improved forced midexpiratory flow (FEF25-75) p less than 0.03), there were marked reductions observed in the overall numbers of T-lymphocytes (CD 2, 5, 8), the numbers of CD45RO+ T-cells, and the numbers of macrophages (RFD1+) with the phenotype of antigen presenting cells. In all six subjects, reductions in the quantitative expression of HLA-DR molecules were also seen.(ABSTRACT TRUNCATED AT 250 WORDS)

Forced expiratory indices in normal black southern African children aged 6-19 years.

Forced vital capacity (FVC), forced expiratory volume in one second (FEV1), forced expiratory ratio (FEV1/FVC x 100), forced mid expiratory flow (FMF), and peak expiratory flow (PEF) were measured in 2000 non-smoking black African schoolchildren aged 6-19 years from Umtata in the Republic of Transkei in Southern Africa. FVC, FEV1, FMF, and PEF were highly correlated with each other and all were highly correlated with age and standing height in both sexes. There was a significant negative correlation between FEV1/FVC and both age and standing height. An increase in the slope of the increase in FVC for both age and height occurred at 11 years and 143 cm in girls and at 13 years and 150 cm in boys. This continued for about two years and 10 cm in both groups before it declined. The mean values of FEV1, FEV1/FVC, and PEF in the present study were 14% lower than those obtained in black American schoolchildren. The present study is the largest study of urban black African schoolchildren and provides useful reference values.

Pulmonary Function in Wood Workers Exposed to Formaldehyde: A Prospective Study

Employees exposed to formaldehyde in the woodworking industry (N = 47) and nonexposed control subjects (N = 20) were examined in 1980 by spirometry and the nitrogen washout technique. A transient impairment of lung function was noted over a work shift. Five years later, 21 subjects were still experiencing exposure to formaldehyde. A transient decrease in lung function was again found over a work shift, as evidenced by a reduction in forced mid-expiratory flow (FEF25-75) of 0.15 l/s and an increase in closing volume (CV%) of 3.0% in nonsmokers. Significant decreases in forced expired volume in 1 s as a percent of forced vital capacity (FEV1.0/FVC) and FEF25-75 were also noted over the 5 y in nonsmokers (0.4% and 0.2 l.s/y, respectively, after correction for normal aging). After 4 wk of no exposure (holidays), FEF25-75 and forced expired vital capacity (FVC, FEV1.0) returned to normal in the smoking group. Lung function in smokers improved less during the holiday. A dose-response relationship was found between exposure to formaldehyde and decrease in lung function. Thus, industrial exposure to formaldehyde causes transient lung function impairment over a work shift, with a cumulative effect over the years. The impairment, however, can be reversed with 4 wk of no exposure.

Acute pulmonary response to formaldehyde exposure in healthy nonsmokers.

The acute pulmonary response to three hours' exposure to 3 ppm formaldehyde (HCHO) during intermittent exercise was evaluated in nine healthy nonsmokers. The protocol consisted of clean air on the first day and HCHO on the second day with a 24-hour follow-up on the third day. Pulmonary function, nonspecific airway reactivity, and symptoms were assessed daily. Thirty minutes of HCHO exposure resulted in a 2% decrease in forced expiratory volume at one second (P less than .05) and a 7% decrease in forced midexpiratory flow rate 25%-75% (P less than .01); however, these effects were no longer present between 60 and 180 minutes. There was also a significant increase in odor (P less than .02), nose or throat irritation (P less than .01), and eye irritation (P less than .01) with exposure. No changes in pulmonary function or airway reactivity were observed 24 hours after exposure. Acute exposure to 3 ppm HCHO produced small, transient decreases in pulmonary function and mild to moderate eye and upper respiratory tract irritation.

Accuracy of an electronic spirometer--a field trial.

Biological calibration of the Hewlett-Packard electronic spirometer against a Stead-Wells 13.5-litre spirometer shows a good concordance for forced vital capacity (FVC; systematic error 0% in women, 1% in men, probable error 4% in both sexes). However, the electronic device underestimates both 1-second forced expiratory volume (FEV1.0) and maximum mid-expiratory flow rate (MMEF) by 8-10%. This bias is unlikely to reflect technical problems of calibration, voltage drift, condensation of moisture or an inappropriate BTPS calibration; possible causes are a non-linearity in the pneumotachograph response characteristics, a lower resistance to expiration in the electronic device, and greater feedback to the subject and observer with the traditional spirometer. Given reports that similar discrepancies arise with other electronic spirometers, care should be taken in overinterpreting data obtained by such devices.

Association of Respiratory Viral Infections with Pulmonary Deterioration in Patients with Cystic Fibrosis

In a two-year prospective study, we examined the effect of respiratory viral infections on pulmonary function in 49 patients with cystic fibrosis (mean age, 13.7 years). Nineteen normal siblings (mean age, 14) served as controls. Subjects were assessed quarterly and at the time of any respiratory illness. Each assessment included nasal washes for viral isolation and blood drawing for respiratory viral serologic studies. Pulmonary-function tests were performed at least twice yearly. Respiratory illnesses were reported significantly more often in the patients (3.7 per year) than in the normal siblings (1.7 per year), although the frequency of proved viral infections (1.67 per year) was identical. In the patients with cystic fibrosis significant correlations (P less than 0.0001) were found between the annual incidence of viral infections and every measure of disease progression in the two-year period, including the rate of decline of the Shwachman score (r = 0.71), the percentage of ideal weight for height (r = 0.80), the forced vital capacity (r = 0.85), the forced expiratory volume in the first second (r = 0.84), the forced midexpiratory flow rate (r = 0.68), and the frequency (r = 0.53) and duration (r = 0.84) of hospitalizations for respiratory exacerbations. We conclude that frequency of viral respiratory infections is closely associated with pulmonary deterioration in patients with cystic fibrosis.

Small-airways dysfunction in nonsmokers chronically exposed to tobacco smoke.

We evaluated the effect of long-term passive smoking (involuntary inhalation of tobacco smoke by nonsmokers) and long-term voluntary smoking on specific indexes of pulmonary function in 2100 middle-aged subjects. Regardless of sex, nonsmokers chronically exposed to tobacco smoke had a lower forced mid-expiratory flow rate (FEF 25 to 75 per cent) and forced end-expiratory flow rate (FEF 75 to 85 per cent) than nonsmokers not exposed (P less than 0.005). In addition, values in passive smokers were not significantly different from those in light smokers and smokers who did not inhale (P less than 0.005). When we looked at the extent to which smoke exposure is related to graded abnormality, we found that nonsmokers in smoke-free working environments have the highest scores on the spirometric tests; passive smokers, smokers who do not inhale, and light smokers score similarly and significantly lower; and heavy smokers score the lowest (P less than 0.005). We conclude that chronic exposure to tobacco smoke in the work environment is deleterious to the nonsmoker and significantly reduces small-airways function.

Lung function changes in smokers with normal conventional spirometry.

The comparative ability to detect early abnormalities in smokers by commonly used lung function tests was studied. Sixty-five healthy male nonsmokers served as a reference group and provided standards for 1-sec forced expiratory volume, vital capacity, end-tidal spirometry, spirometric forced mid-and end-expiratory flows, single-breath diffusing capacity, static lung volumes (helium method), and single-breath N2 closing volume measurements, In the present series of 80 male smokers, the measurements of forced mid-expiratory flow and forced end-expiratory flow did not improve the ability of the more conventional indices, 1-sec forced expiratory volume and the ratio of 1-sec forced expiratory volume to vital capacity, to detect obstructive lung disease. In 71 smokers with normal 1-sec forced expiratory volume and ratio of 1-sec forced expiratory volume to vital capacity, the end-tidal spirometry, diffusing capacity, and residual volume indices revealed 14,20, and 21 per cent of abnormalities. respectively. The single-breath N2 closing volume test (Phase IV/vital capacity and slope of Phase III) detected the greatest number of subtle changes in lung function; this was abnormal in 32 per cent of smokers with normal conventional spirometry. In young or light smokers, Phase IV/vital capacity was more frequently increased than the slope of Phase III; an incerse trend was observed in older or heavier smokers. The single-breath N2 closing volume test also provided the greatest number of abnormal results when other indices were impaired in the same subjects.