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Pressurized metered‐dose inhalers attached to spacers are now the most common form of delivery of anti‐asthma medication in children. However, no reliable data are available of how much drug reaches the lungs in children of different ages. This information is crucial, as it determines the efficacy of therapy. In this study, we present information on the amount of drug reaching the lungs in children from a pressurized metered‐dose inhaler attached to a detergent‐coated spacer. We studied 18 asthmatic children inhaling radiolabeled salbutamol through detergent treated spacers to minimize electrostatic charge on the spacer wall. Lung deposition was much higher than expected when using detergent‐coated spacers. Mean (SD) lung deposition, expressed as a percentage of the total actuated dose (five actuations), was 16.4% (5.5) in younger children inhaling through a small volume spacer, and 28.2% (6.7) and 41.8% (3.8) in older children inhaling with different breathing patterns through a large volume spacer. These findings have major implications for dosage regimens for inhaled anti‐asthma medication in children. Lower doses may be sufficient for adequate drugs delivered through spacers treated for static to achieve a desired clinical response. Pediatr Pulmonol. 2000; 29:389–393. © 2000 Wiley‐Liss, Inc.

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Objectives: The aim of this study was to compare subjective measures (overall health assessment both by the study physician and the child’s mother) with objective measurements of forced expiratory volumes (FEV_t) and maximal flow at functional residual capacity v̇_maxFRC) in recurrently wheezy infants. Methods: Sixteen wheezy infants (12 boys) aged 8–26 months were studied. A clinical assessment at visit 1 was followed by the run-in period during which day- and nighttime asthma symptom scores were obtained. The actual study period consisted of 2 visits when patient’s lung function was assessed. The first of which was during an acute exacerbation (visit 2), while the second was when the infant was asymptomatic (visit 3). FEV_t were obtained by the raised volume rapid thoracic compression technique (RVRTC) and v̇_maxFRC by the tidal volume rapid thoracic compression technique (TVRTC). Results: Mean FEV_t but not mean v̇_maxFRC were significantly lower at visit 2 compared to visit 3 (FEV_0.5: p = 0.005, and FEV_0.75: p = 0.002; v̇_maxFRC: p = 0.15) and correlated well with overall health assessment by the study physician (FEV_0.5: r = 0.82, and FEV_0.75: r = 0.84), but not with the overall health assessment by the mother. Conclusions: We have shown in the present study that objective measurements of FEV_t from a raised lung volume correlate well with the overall health assessment by the study physician; this was in contrast to measurements of v̇_maxFRC in the tidal volume range. We therefore conclude that the RVRTC technique is a feasible method to assess and monitor obstructive lung disease in infancy.

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The influence of pulmonary vascular congestion on the response of the airways and lung tissue to low doses of inhaled methacholine (MCh) was studied by inflating a balloon catheter in the left atrium of the heart in six piglets, with an additional five piglets serving as control animals. Congestion alone resulted in small increased in baseline airway (Raw) (14.6 +/- 3.7%) and tissue (Rti) resistance (8. 1 +/- 6.5%). Low-dose inhaled MCh (0.3 mg/ml) increased Raw and Rti in the control group by 10.8 +/- 10.3% and 42.2 +/- 29.5%, respectively. The increase in Raw with MCh in the presence of vascular engorgement was significantly greater (67.8 +/- 18.9%) but the increase in Rti (38.1 +/- 13.2%) was similar to that seen in the control group. Morphometric measurements were performed on transverse sections of large and small airways from nine additional piglets (three congested only, three MCh only, and three congestion plus MCh). The thickness of the inner airway wall was similar in all groups. Compared with MCh only piglets, the thickness of the outer airway wall (between the outer border of the smooth muscle and the surrounding lung parenchyma) was increased (p < 0.05) in engorged only and engorged plus MCh piglets. Compared with MCh only and engorgement only, the amount of airway smooth muscle shortening was greater (p < 0.05) in all airway size groups in piglets that underwent engorgement plus MCh challenge. The results of this study demonstrate that pulmonary vascular engorgement, induced by increased left atrial pressure, selectively enhances the airway, but not the parenchymal, response to inhaled MCh. These changes are associated with increased thickness of the outer airway wall in response to vascular congestion, suggesting that uncoupling of the mechanical interdependence between the airway smooth muscle and the lung parenchyma may have occurred. Mechanical uncoupling may reduce the load opposing smooth muscle shortening resulting in increased airway narrowing in response to low doses of inhaled methacholine.