| 1. Coordination between actuation and inhalation is crucial to effective use |
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| The timing of actuation in relation to inhalation is critical to delivery of the drug to the lungs. Studies have demonstrated that actuation during the initial part of the inhalation provides optimal drug delivery.
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| 2. Newman SP. Lund, Sweden; 1983
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| The effects of terbutaline on lung parameters were examined following actuation of the pMDI at various stages of inhalation (20, 50, and 80% of lung capacity) as well as 3 seconds before a deep inhalation and after completion of inhalation. When actuated during inhalation, increases in PEF were marked and similar. Lesser effects were observed following actuation prior to inhalation and no noticeable effects were observed following actuation at residual volume.
The effects of drug administered via pMDI are most marked when actuated during inhalation
Terbutaline was the drug used in this study. RV = residual volume, TLC = total lung capacity, VC = vital capacity. Adapted from Newman et al., 1983.
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| 3. Inhalation should be at low flow rates for maximal deposition
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| Studies comparing low and high inspiratory flow rates have demonstrated that improvement in lung function is greater at low flow rates.
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| 4. Newman SP. Lund, Sweden; 1983 |
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Patients with reversible airway obstruction were given two puffs of terbutaline 250 µg. Doses were actuated at low (25–30 L/min) or high (80–90 L/min) flow rates. Breath was held for 10 seconds at low flow rates and 10 or 4 seconds at high flow rates. Doses were actuated at either 20, 50, or 80% of vital capacity.
Low flow rates resulted in a greater increase in FEV1than did high flow rates. These effects were independent of time of actuation.
Effects of drugs administered via pMDI are greater when inhaled at slow flow rates
The drug used in this study was terbutaline. Slow flow rate is defined as 25–30 L/min, fast flow rate is defined as 80–90 L/min). Adapted from Newman et al., 1983.
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| 5. After inhalation, breath should be held to obtain maximum effects |
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Holding breath for 10 seconds after actuation of a pMDI provides close to maximal bronchodilatory effects. Holding breath for longer periods did not provide any additional advantages.
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| 6. Newman SP. Lund, Sweden; 1983 |
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Patients with reversible airway disease received two controlled inhalations of terbutaline 250 µg. Following inhalation patients held their breath for 4, 10, or 20 seconds. Actuation was at 20, 50, or 80% of vital capacity. Holding breath for 10 or 20 seconds resulted in equivalent effects on FEV1which were significantly greater than those following holding breath for 4 seconds.
Holding breath for 10 or more seconds after actuation of a pMDI improves clinical effects
The drug used in this study was terbutaline. Adapted from Newman et al., 1983.
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