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Office Spirometry for Inhaled Insulin
| Article Date: 5/31/2007 |
Office Spirometry for Inhaled Insulin
by Paul Enright, MD and Denny Doherty, MD
National Lung Health Education Program (www.NLHEP.org)
The primary advantage of inhaling insulin instead of injecting it is patient preference. For patients who achieve better control of their diabetes because of better adherance to your prescribed insulin therapy, a reduced risk of subsequent vascular disease can be expected. Exubera (a Pfizer trademark) became the first widely available inhaled insulin in 2006. At least 4 other companies are developing inhaled insulin products. The methods used by the 5 wet aerosol or dry powder inhaler devices to deliver insulin to the lungs vary widely. Clinical trials of Exubera have shown that a small minority of patients experience worrisome declines in lung function, so the FDA requires that spirometry be performed before you prescribe it. The rates of pulmonary side-effects from other inhaled insulin products are not yet known.
On the average, adults with diabetes have a slightly smaller forced vital capacity (FVC) than healthy adults. FVC is the amount of air that a patient can exhale after a maximal inhalation. The FVC is easily measured using an office spirometer, averaging 5 liters in men and 4 liters in women. The term vital capacity was coined over 150 years ago by Doctor John Hutchinson because his patients with a large vital capacity lived longer. Many epidemiology studies done during the past 25 years have confirmed that spirometry results are a strong, indepentent predictor of cardiovascular and all-cause mortality. The lower FVC of diabetic adults is apparently the result of mild retardation of lung growth during adolescence, about the same time as insulin resistance is also beginning, but diabetes is not yet apparent.
Up to one-third of patients with Type 1 or Type 2 diabetes taking Exubera in clinical trials noticed some coughing soon after inhaling the insulin. Three to 4 percent of them reported shortness of breath, a rate somewhat higher than those randomized to continue traditional subcutaneuous or oral insulin therapy. Lung function was measured throughout these studies, using spirometry (FEV1 and FVC) and diffusing capacity (DLCO). Patients randomized to take Exubera experienced slightly greater declines in FEV1 and DLCO (on the average) when compared to those using traditional therapy. Lung function normally declines as we grow older, but about 5% of the patients taking Exubera experienced worrisome declines in FEV1 (more than 10%). FEV1 is the amount of air exhaled in the first second of an FVC maneuver.
Because of the potential pulmonary side-effects of Exubera, the FDA approved it with cautions for those prescribing it. Exubera is contraindicated in smokers because smoking greatly increases the uptake of inhaled insulin from the lungs into the bloodstream. Exubera is also contraindicated in patients with poorly controlled lung disease, such as asthma or COPD. Spirometry must be done before Exubera is prescribed. You can use a spirometer in your office to measure FEV1 and FVC or order spirometry to be done in a hospital-based pulmonary function laboratory. Exubera is not recommended when the FEV1 is below 70% of the predicted value.
Spirometry must be repeated six months after Exubera is started (the baseline) and every 12 months thereafter. During follow-up tests, if the FEV1 has fallen to less than 80% of the baseline value, then spirometry should be repeated. If the excessive FEV1 decline is confirmed, then Exubera should be discontinued and the patient returned to traditional therapies to control their diabetes.
The National Lung Health Education Program (NLHEP) is a group of pulmonary specialists who promote the use of spirometry for the detection of COPD in smoking adults and patients with respiratory symptoms. On the NLHEP website, desirable features of office spirometers are listed. After office spirometers have been tested by a third-party and found accurate (using an ATS waveform generator), they are tested by NLHEP (unbiased respiratory therapists) to determine if they have the features which minimize interpretation misclassification rates and make them easy-to-use by primary care practitioners.
Spirometry requires athletic-type breathing maneuvers. If submaximal test efforts are obtained, the FEV1 or FVC are falsely reduced. Such poor quality spirometry tests can make the patient appear to have low lung function (a false positive). Currently there are no certification programs for spirometry testing in the United States, but an excellent CD-ROM is available for learning how to perform office spirometry: Spirometry Fundamentals. Pfizer plans to offer this CD-ROM without charge to interested primary care practitioners. (www.http://depts.washington.edu/ventures/UW_Technology/Express_Licenses/spiroFun.php)
For more information about office spirometry, see the editorial in Physicians Office Resource Issue #3 (page 14 and 16) and the NLHEP website www.NLHEP.org
by Paul Enright, MD and Denny Doherty, MD
National Lung Health Education Program (www.NLHEP.org)
The primary advantage of inhaling insulin instead of injecting it is patient preference. For patients who achieve better control of their diabetes because of better adherance to your prescribed insulin therapy, a reduced risk of subsequent vascular disease can be expected. Exubera (a Pfizer trademark) became the first widely available inhaled insulin in 2006. At least 4 other companies are developing inhaled insulin products. The methods used by the 5 wet aerosol or dry powder inhaler devices to deliver insulin to the lungs vary widely. Clinical trials of Exubera have shown that a small minority of patients experience worrisome declines in lung function, so the FDA requires that spirometry be performed before you prescribe it. The rates of pulmonary side-effects from other inhaled insulin products are not yet known.
On the average, adults with diabetes have a slightly smaller forced vital capacity (FVC) than healthy adults. FVC is the amount of air that a patient can exhale after a maximal inhalation. The FVC is easily measured using an office spirometer, averaging 5 liters in men and 4 liters in women. The term vital capacity was coined over 150 years ago by Doctor John Hutchinson because his patients with a large vital capacity lived longer. Many epidemiology studies done during the past 25 years have confirmed that spirometry results are a strong, indepentent predictor of cardiovascular and all-cause mortality. The lower FVC of diabetic adults is apparently the result of mild retardation of lung growth during adolescence, about the same time as insulin resistance is also beginning, but diabetes is not yet apparent.
Up to one-third of patients with Type 1 or Type 2 diabetes taking Exubera in clinical trials noticed some coughing soon after inhaling the insulin. Three to 4 percent of them reported shortness of breath, a rate somewhat higher than those randomized to continue traditional subcutaneuous or oral insulin therapy. Lung function was measured throughout these studies, using spirometry (FEV1 and FVC) and diffusing capacity (DLCO). Patients randomized to take Exubera experienced slightly greater declines in FEV1 and DLCO (on the average) when compared to those using traditional therapy. Lung function normally declines as we grow older, but about 5% of the patients taking Exubera experienced worrisome declines in FEV1 (more than 10%). FEV1 is the amount of air exhaled in the first second of an FVC maneuver.
Because of the potential pulmonary side-effects of Exubera, the FDA approved it with cautions for those prescribing it. Exubera is contraindicated in smokers because smoking greatly increases the uptake of inhaled insulin from the lungs into the bloodstream. Exubera is also contraindicated in patients with poorly controlled lung disease, such as asthma or COPD. Spirometry must be done before Exubera is prescribed. You can use a spirometer in your office to measure FEV1 and FVC or order spirometry to be done in a hospital-based pulmonary function laboratory. Exubera is not recommended when the FEV1 is below 70% of the predicted value.
Spirometry must be repeated six months after Exubera is started (the baseline) and every 12 months thereafter. During follow-up tests, if the FEV1 has fallen to less than 80% of the baseline value, then spirometry should be repeated. If the excessive FEV1 decline is confirmed, then Exubera should be discontinued and the patient returned to traditional therapies to control their diabetes.
The National Lung Health Education Program (NLHEP) is a group of pulmonary specialists who promote the use of spirometry for the detection of COPD in smoking adults and patients with respiratory symptoms. On the NLHEP website, desirable features of office spirometers are listed. After office spirometers have been tested by a third-party and found accurate (using an ATS waveform generator), they are tested by NLHEP (unbiased respiratory therapists) to determine if they have the features which minimize interpretation misclassification rates and make them easy-to-use by primary care practitioners.
Spirometry requires athletic-type breathing maneuvers. If submaximal test efforts are obtained, the FEV1 or FVC are falsely reduced. Such poor quality spirometry tests can make the patient appear to have low lung function (a false positive). Currently there are no certification programs for spirometry testing in the United States, but an excellent CD-ROM is available for learning how to perform office spirometry: Spirometry Fundamentals. Pfizer plans to offer this CD-ROM without charge to interested primary care practitioners. (www.http://depts.washington.edu/ventures/UW_Technology/Express_Licenses/spiroFun.php)
For more information about office spirometry, see the editorial in Physicians Office Resource Issue #3 (page 14 and 16) and the NLHEP website www.NLHEP.org