Effect of inhaled heparin on lung function and coagulation in healthy volunteers.

The aim of the present study was to investigate the safety of increasing doses of a well-defined lower respiratory tract (LRT) dose of inhaled heparin with regard to pulmonary function and coagulation. Ten volunteers inhaled heparin from Sidestream jet nebulizers loaded with 100,000, 200,000, 300,000 or 400,000 International Units (IU) of heparin. Lung function, antifactor (anti)-Xa, activated partial thromboplastin time (APTT), tissue factor pathway inhibitor (TFPI), whole blood clotting time, platelets, von Willebrand factor, and C-reactive protein were determined before and 1, 3, 6, and 24 h after inhalation. The highest LRT dose was 32,000 IU heparin. Inhaled heparin did not affect pulmonary function. The area under the curve of the anti-Xa activity increased with increasing doses of heparin (p=0.005), but remained unchanged for all other variables. Peak anti-Xa activity was 0.113 IU x mL(-1) 6 h after inhalation of 400,000 IU heparin. When compared to baseline values: anti-Xa increased after 200,000 (p=0.03), 300,000 (p=0.004), and 400,000 IU (p=0.002) heparin; APTT increased to a maximum of 1.03 6 h after inhalation of 400,000 IU heparin (p=0.05); TFPI increased after 100,000 (p=0.01), 200,000 (p=0.01), 300,000 (p=0.006) and 400,000 IU (p<0.001). Inhaled heparin delivery of 32,000 International Units to the lower respiratory tract can safely be inhaled for clinical or research purposes.

Jet and ultrasonic nebulization of single chain urokinase plasminogen activator (scu-PA).

Recent studies have indicated that the deposition of intra-alveolar fibrin may play a central role in the pathogenesis of acute respiratory distress syndrome (ARDS). Our aim was to study whether the indigenous fibrinolytic agent (urokinase) normally present in the alveoli can be administered locally by nebulization in a recombinant zymogen form as single chain urokinase plasminogen activator (scu-PA). We aimed to characterize the particle size distribution, drug output, and enzymatic activity of scu-PA after nebulization with a Ventstream jet nebulizer (Medic-Aid, Bognor Regis, UK) and a Syst'AM DP-100 ultrasonic nebulizer (Pulmolink, Kent, UK). The particle size distribution was measured with a laser diffraction method and the drug output was determined by collection on filters. The amount of protein on the filters was determined with the Lowry method, and the enzymatic activity after nebulization was measured with a microtiter fibrin plate assay. The mass median diameter (MMD) of the scu-PA aerosol generated with the ultrasonic nebulizer was 3.69 (3.53-3.83) microm and with the jet nebulizer 2.96 (2.91-3.03) microm (p < 0.001). The drug output from the two nebulizers did not differ between nebulizers (p = 0.054). Fibrinolytically active scu-PA was generated with both nebulizers, but in contrast to jet nebulization, ultrasonic nebulization caused partial inactivation of scu-PA (p < 0.001). In conclusion, nebulization of scu-PA with the jet nebulizer is superior to ultrasonic nebulization in terms of particle size distribution and preservation of fibrinolytic activity.

Lung deposition and clearance of inhaled (99m)Tc-heparin in healthy volunteers.

The purpose of this study was to quantify the lower respiratory tract (LRT) dose delivered by a single nebulization of (99m)technetium-labeled sodium heparin as well as its airway distribution, and kinetics of aerosol clearance, since inhaled heparin may be useful in the treatment of asthma. Fifteen healthy subjects (5 male, 10 female) inhaled heparin from a jet nebulizer loaded with 90,000 IU of (99m)Tc-heparin, driving flow rate 10 L/min. Lung scintigrams and blood samples were taken immediately and at several time points up to 24 h after inhalation. 15 +/- 3% (mean +/- SD) (mean 13,300 IU) of the heparin nebulizer charge reached the mouth, and 8 +/- 2% (mean 7,000 IU) was found in the LRT. Jet nebulizer residual was 48 +/- 6% (mean 43,000 IU), 32 +/- 4% (mean 29,000) was found on exhalation filters, and 5 +/- 2% in the tubing. (99m)Tc-heparin was distributed uniformly in the lungs, and clearance was biphasic. 39 +/- 8% of the LRT dose of (99m)Tc-heparin remained in the lungs 24 h after inhalation. 10.00 +/- 3.40% (687 +/- 310 IU) of the LRT dose or 0.76 +/- 0.35% of the nebulizer charge was found in the blood. Peak concentration in the blood was found 61 +/- 25 min after conclusion of inhalation, which took 15 min. We conclude that a small but significant fraction of nebulized heparin reaches the LRT. The inhaled heparin distributes uniformly in the lungs from which it clears slowly, making it suitable for local administration without induction of measurable changes in coagulation assays. Administration of the present single dose of heparin thus appears to be safe.

Characterization of heparin aerosols generated in jet and ultrasonic nebulizers.

Inhaled heparin has been used for asthma treatment, but results have been inconsistent, probably due to highly varying lung doses. We determined the output per unit time and the particle size distributions of sodium heparin, calcium heparin, and low molecular weight (LMW) heparin formulations in five concentrations from Sidestream jet nebulizers (Medic-Aid, Bognor Regis, England) and an Ultraneb 2000 ultrasonic nebulizer (DeVilbiss, Langen, Germany). We also determined the inhaled mass and the estimated respirable mass for some combinations. For the jet nebulizer, output per minute increased with increasing concentration and flow rate, and particle size decreased from 3.64 to 2.01 microns (mass median diameter [MMD]). The percentage of particles less than 3 microns ranged from 41% to 74%. For the ultrasonic nebulizer, maximum output per minute was achieved at a concentration of 7000 i.u./mL; this maximum depended upon the viscosity and temperature of the solution. MMD was independent of formulation, temperature, or concentration and ranged from 5.61 to 7.03 microns. Sodium heparin/calcium heparin in a concentration of 20,000 i.u./mL in the jet nebulizer driven at 10 L/min produced the highest dose of heparin capable of reaching the lower respiratory tract. Mass balance was determined for these combinations with the jet nebulizer run until visible aerosol generation ceased. Of a loading dose of 80,000 i.u. of heparin, 45,000 i.u. remained in the dead space of the nebulizer, 20,000 i.u. was deposited on the exhalation filter, and 15,000 i.u. was captured on the inhalation filter (inhaled mass). This corresponds to a respirable mass of 10,000 i.u. of heparin with a high probability of reaching the lower respiratory tract in normal healthy adults.

Effect of terbutaline on exercise capacity and pulmonary function in patients with chronic obstructive pulmonary disease.

The objective of this study was to investigate the effects of a single dose of a beta2-agonist, terbutaline (Bricanyl Turbuhaler), on resting lung function and exercise capacity in patients with chronic obstructive lung disease. Using a double-blind, placebo-controlled, randomized crossover study and outpatients from a department of pulmonary medicine at a major inner-city hospital, we examined 26 individuals with chronic obstructive lung disease who met the criteria of 40%

Bronchodilator and corticosteroid reversibility in ambulatory patients with airways obstruction.

With the aim of characterising subgroups, we analysed reversibility tests from 1,048 patients with airways obstruction (baseline FEV1 less than 60% of predicted normal (%pred), and FEV1 to FVC ratio less than 0.6). Spirometry before and after inhalation of salbutamol 0.3 mg and ipratropium bromide 0.06 mg was performed before and after one week of treatment with prednisone 30 mg daily. The changes in FEV1 after bronchodilators showed unimodal distribution (mean = 7.0 %pred, st.dev. = 6.6 %pred). The responses to corticosteroid were more spread out (mean = 6.3 %pred, st.dev. = 13.8 %pred). The correlation between bronchodilator responses before and after corticosteroid treatment was poor (r = 0.30), although highly significant (p less than 0.000,001). The responses to bronchodilators were virtually independent of the steroid reversibility. The corticosteroid response was inversely related to age (r = -0.20, p less than 0.000,001) and smoking habits (r = -0.17, p less than 0.000,001), and moderately associated with blood eosinophilia (r = 0.34, p less than 0.000,001). The frequency distribution of the bronchodilator responses and the steroid response and combinations of the responses were all unimodal, making any distinction between nosologic subgroups arbitrary. It is clear from the study that criteria other than just response to therapy must be employed for distinction of subgroups among patients with airways obstruction.

The short-latency respiratory response to sudden withdrawal of hypercapnia and hypoxia in man.

Five healthy young male subjects were maintained in a state of mild asphyxia (PA, CO2 approximately 45 torr, 6.0 kPa, PA, O2 approximately 50 torr, 6.6 kPa), i.e. with moderately strong drives from both arterial and intracranial chemoreceptors VT, TT and TI were recorded and V and TE derived breath by breath. The arterial chemoreceptor component was briefly and abruptly reduced, perhaps silenced, by two separate procedures, each repeated twenty-four times on each subject: B, removal of hypercapnia (two breaths hypoxia with PI, CO2 = 0 through a separate inspiratory line) and C, removal of asphyxia (two breaths O2). In control tests, A, the maintenance mixture was replaced by an identical mixture, using an identical manipulation. For each subject means of B and C were compared with means of A and with each other. Quick reflex changes (first three breaths) in V, VT and TE in tests B were not appreciably different from those in tests C in any subject; changes in TI were minimal in all. Thus removal of only the hypercapnic component of the arterial chemoreflex drive appears to be as efficient as the removal of both components simultaneously.

The relationship between maximal ventilation, breathing pattern and mechanical limitation of ventilation.

1. The extent to which the pattern of breathing at maximal ventilation in man is affected by the mechanical properties of the respiratory pump has been studied. 2. The maximal effort flow volume (MEFV) loop has been used to calculate the shortest possible inspiratory (TI) and expiratory (TE) durations associated with the highest ventilation for all tidal volumes (VT). These minimal TIS and TES hve been plotted on a VT-TI-TE diagram. 3. Such predicted minimal TIS and TES were compared with observed minimal values from five healthy subjects who tried to reach their maximal ventilations during three experimental conditions: maximal voluntary hyperventilation, rebreathing, and graded exercise. 4. We have found that exercise increases the maximal flows at all lung volumes and confirmed that rebreathing has no such effect. 5. During hyperventilation the mechanical limits were followed closely for all VTS. During exercise and rebreathing the VT-TI and the VT-TE relationships showed a definite maximum of VT at submaximal ventilation in half the cases. The calculated minimal TIS and TES were approached but not reached. This indicates that maximal ventilation is not entirely limited by the mechanical properties of the respiratory pump, but that mechanical factors influence the regulation of breathing pattern when ventilation approaches the maximal capacity of the respiratory pump.

Short-latency ventilatory responses to sudden withdrawal of hypoxia at normal and raised body temperature in man.

Approximately isopnoeic conditions (VE=40 l/min) were achieved by the inhalation of asphyxial gas mixtures (PA,O2 60 torr, PA,CO2 40-45 torr) in normothermia after a rise in rectal temperature of 1.6 degrees C had been induced by a heated flying suit. Arterial chemoreceptor drive was transiently reduced by either isocapnic removal of hypoxia (type (1) tests: two breaths of CO2 in O2) or simultaneous withdrawal of both hypercapnia and hypoxia (type (2) tests: two breaths of O2). 8-13 tests of each type were performed at both temperature conditions in 6 expts. on 4 healthy human subjects. Expired volume, total breath duration and inspiratory time were recorded, and minute ventilation and expiratory time subsequently computed breath by breath. In hyperthermia the steady-state ventilation of 40 l/min (at a relatively higher respiratory frequency and a correspondingly lower tidal volume) was achieved at a PA,CO2 which was 5 torr lower than in normothermia. Ventilation decreased significantly in all tests. Tested with a 3-way analysis of variance significant differences between the ventilatory responses at the two temperature conditions, and between the two test types were found. The rate of change of ventilation was greater in hyperthermia than in normothermia, and also greater in type (2) tests than in type (1) tests. Since isopnoeic conditions existed prior to the tests, this implies that the arterial chemoreceptor contribution to the total ventilatory drive is increased in hyperthermia. In type (2) tests a significant lengthening of expiratory time was observed in the first test breath. This finding confirms the effect in man of changes in airway PCO2 on lung stretch receptor discharge.

Very small, very short-latency changes in human breathing induced by step changes of alveolar gas composition.

1. Three healthy young males were maintained for sessions of about 1 hr in a state of mild asphyxia (PA,O2 approximately 55, PA,CO2 approximately 45 torr), i.e. with moderately strong drives from both arterial and intracranial chemoreceptors. Tidal volume (VT), breath duration (TT) and duration of inspiration (TI) were recorded, and ventilation (VE) and duration of expiration (TE) were derived breath by breath. 2. The arterial chemoreceptor component of the drive was briefly and abruptly reduced, perhaps silenced, by three separate procedures: the inspiratory pathway was connected for two breaths to a second gas supply line containing, B, hypoxia with Pi,CO2 zero (removal of hypercapnia with maintained hypoxia); C, pure oxygen (removal of asphyxia); and D, oxygen with 40 torr added PCO2 (removal of hypoxia with maintained hypercapnia). In controls, A, the second inspiratory line contained the maintenance mixture so that the switch involved no change of inspiratory gas composition. Each type of test was repeated twenty-four times on each subject. 3. Responses attributable to silencing of arterial chemoreceptors (i.e. with 1 1/2--3 breath latencies about equal to the lung-to-ear circulation time) are reported elsewhere. 4. Very small responses, occurring only half a respiratory cycle after first inhalation of the test mixture, were detected by pooling all responses of each kind from all subjects. When hypoxia was withdrawn, with (C) or without (D) simultaneous withdrawal of hypercapnia, VT and VE were reduced by 3 and 2% respectively, probably because gas mixtures containing high oxygen concentrations are appreciably more viscous than hypoxic mixtures and so require more effort to breathe in and out. When hypercapnia was withdrawn with (C) or without (B) simultaneous withdrawal of hypoxia, TE was significantly lengthened (mean, + 65 +/- 18 msec), 5. The change of TE was discussed in relation to known effects of CO2 on airway receptors in the dog.