Drugs potentially affecting the extent of airways reversibility on pulmonary function testing are frequently consumed despite guidelines.

BACKGROUND: The increase in forced expiratory volume in one second (FEV1) effected by a bronchodilator is routinely assessed when patients undertake pulmonary function testing (PFT). Several drug classes can theoretically affect the magnitude of the increase in FEV1. Withholding periods are advised for many but not all such drugs. Anecdotally, many subjects presenting for PFT are found to have taken drugs that might affect the test. We did an audit of patients presenting for PFT to assess the frequency with which FEV1 reversibility might be affected by drugs. METHODS: One hundred subjects presenting to the laboratory for PFT were questioned about recent drug consumption by an independent pharmacy intern. Reversibility of FEV1 was assumed to have been affected if drugs of interest were consumed within defined withholding periods or two half-lives for drugs without such data. RESULTS: Sixty-three subjects were prescribed drugs likely to affect FEV1 reversibility. Thirty-six subjects consumed at least one such drug within the withholding period. Half (18) of these patients consumed ß-blockers with or without ß-agonists. Sixty-five subjects did not recall receiving any advice about withholding drugs prior to the test and only 10 recalled receiving advice from their clinician or pulmonary function technician. CONCLUSION: Subjects presenting for PFT are infrequently advised to withhold drugs that may affect FEV1 reversibility, and consequently, often take such drugs close to the time of the test. Therefore, it is likely that the increase in FEV1 is frequently affected by interference from drugs and this might impact on diagnosis and/or treatment options.

Accuracy of monitoring for sleep-related breathing disorders in the coronary care unit.

STUDY OBJECTIVES: To evaluate the frequency of sleep-disordered breathing (SDB) in patients presenting with acute cardiovascular events. DESIGN: Repeat observational study. SETTING: Coronary care unit of a university hospital. PATIENTS: A total of 26 patients presenting with unstable angina, myocardial infarction, or left ventricular failure. MEASUREMENTS: Level 3 portable sleep study performed at the time of acute presentation (study 1; 26 patients) and again > or = 6 weeks later (study 2; 18 patients). RESULTS: SDB (apnea-hypopnea index > or = 15) was identified in 13 of 26 patients (50%) during study 1. One patient had central sleep apnea. Of the 18 who completed the two studies, SDB was confirmed in 10 of 18 patients (56%) during study 1 but in only 5 of 18 patients (28%) during study 2. All five of those patients had obstructive sleep apnea (OSA). Six patients were deemed to have false-positive results for SDB at follow-up, and one patient was deemed to have a false-negative result. Detailed analysis suggested that supine posture during study 1 may have contributed to the high false-positive rate, even though only three of six patients fulfilled the criteria for positional OSA. CONCLUSIONS: SDB occurs commonly in patients presenting with an acute cardiovascular event. Consideration of the diagnosis of SDB is an important strategy for secondary prevention. However, our findings indicate that SDB abnormalities may be transient. Sleep studies to investigate SDB as a potential risk factor for cardiovascular morbidity should be carried out when the patient is clinically stable.

Elevated posture for the management of obstructive sleep apnea.

This study aimed to evaluate the effectiveness of elevated posture in the management of obstructive sleep apnea (OSA). Fourteen subjects presenting with mild-moderate OSA, (apnea-hypopnea index [AHI] 10 to 60/h), were included in a randomized crossover investigation. A shoulder-head elevation pillow (SHEP) was compared with nasal continuous positive airway pressure (nCPAP) therapy. Treatment success was defined as AHI10<16/h. Four subjects achieved treatment success with the SHEP and three achieved partial success. The remaining seven subjects were treatment failures. In contrast, success was achieved with nCPAP in 12 subjects. One subject achieved partial success and one was a treatment failure. With the SHEP, the mean AHI decreased from 27+/-12/h to 21+/-17/h. With nCPAP, the mean AHI was 5+/-3/h; (p=0.008 for the difference between treatments). Although somewhat variable, these data provide evidence that elevated posture during sleep is helpful in the management of OSA in some individuals. Results support the use of elevated posture as second-line therapy in the management of OSA. However, no relationships could be identified between baseline data, including the identification of positional OSA, and objective outcomes that might predict patients who are likely to benefit from treatment in an elevated position.