Right ventricle dimensions and function in response to acute hypoxia in healthy human subjects.

AIM: Acute hypoxia produces acute vasoconstriction in the pulmonary circulation with consequences on right ventricular (RV) structure and function. Previous investigations in healthy humans have been restricted to measurements after altitude acclimatization or were interrupted by normoxia. We hypothesized that immediate changes in RV dimensions in healthy subjects in response to normobaric hypoxia differ without the aforementioned constraints. METHODS: Transthoracic echocardiography was performed in 35 young, healthy subjects exposed to 11% oxygen, as well as six controls under sham hypoxia (20.6% oxygen, single blind) first at normoxia and after 30, 60, 100, 150 min of hypoxia or normoxia respectively. A subgroup of 15 subjects continued with 3-min cycling exercise in hypoxia with subsequent evaluation followed by an assessment 1 min at rest while breathing 4 L min-1 oxygen. RESULTS: During hypoxia, there was a significant linear increase of all RV dimensions (RVD1 + 29 mm, RVD2 + 42 mm, RVD3 + 41 mm, RVOT + 13 mm, RVEDA + 18 mm, P < 0.01) in the exposure group vs. the control group. In response to hypoxia, right ventricular systolic pressure (RVSP) showed a modest increase in hypoxia at rest (+7.3 mmHg, P < 0.01) and increased further with physical effort (+11.8 mmHg, P < 0.01). After 1 min of oxygen at rest, it fell by 50% of the maximum increase. CONCLUSION: Acute changes in RV morphology occur quickly after exposure to normobaric hypoxia. The changes were out of proportion to a relatively low-estimated increase in pulmonary pressure, indicating direct effects on RV structure. The results in healthy subjects are basis for future clinically oriented interventional studies in normobaric hypoxia.

Cromoglycate, reproterol, or both--what's best for exercise-induced asthma?

OBJECTIVE: International guidelines recommend short- (SABA) or long-acting b-agonists for the prevention of bronchoconstriction after exercise (EIB) in patients with exercise-induced asthma (EIA). However, other drugs are still in discussion for the prevention of EIB. We investigated the efficacy of a combination of inhaled sodium cromoglycate and the ß-mimetic drug reproterol versus inhaled reproterol alone and both versus inhaled placebo in subjects with exercise-induced asthma (EIA). METHODS: The study aimed to prove the preventive effect of a combination of 1-mg reproterol and 2-mg disodium cromoglycate (DSCG) and its single components vs. placebo, measuring the decrease of FEV1 after a standardized treadmill test in 11 patients with recorded EIA. The study medication was twice as high as those of drugs which are commercially available (e.g., Allergospasmin®, Aarane®). RESULTS: The results revealed that the combination of reproterol and DSCG was significantly effective against a decrease of FEV1 after a standardized exercise challenge test (ECT) compared to placebo. The short-acting b-agonist reproterol alone had almost the same effectiveness as the combination of reproterol and DNCG. The difference between the combination with DNCG and reproterol alone was less than 10% and insignificant (p 0.48). DNCG alone did not show a difference in the effectiveness compared to placebo. CONCLUSION: Prevention of EIA with the combination of reproterol and DSCG or with reproterol only is effective. An exclusive recommendation in favor of the combination cannot be given due to the low difference in the effectiveness versus reproterol alone. Due to the limited number of subjects and some probands showing protection under DSCG, it cannot be completely excluded that there is some preventive power of DSCG in individual cases.

Telemedicine in the sleep laboratory: feasibility and economic advantages of polysomnograms transferred online.

The costs for polysomnography (PSG) and alternative diagnostic procedures for sleep-disordered breathing are challenging public health care systems. We wanted to determine if a telemedicine protocol with online transfer of PSGs from a remote site could be cost-effective and clinically useful while improving patient access to full PSG. Fifty-nine PSGs were performed in 54 pulmonary patients with suspected sleep-disordered breathing at a remote hospital. The data were transferred by File Transfer Protocol (FTP) via the Internet to Walter Reed Army Medical Center (WRAMC) for scoring and interpretation. The results were faxed back to the remote hospital. Clinical utility was assessed by evaluating the reasons for patient referral and the resulting diagnoses. The economic benefits were calculated by comparing direct expenses of the telemedicine protocol with costs for contracting PSGs at outside sleep laboratories. A total of 93% (55) of all PSGs were transferred successfully online. Of the 54 patients, 47 had PSGs performed for diagnosis (including three split-night studies), 8 underwent treatment titration, and 1 patient had both overnight studies. Diagnoses were obstructive sleep apnea in 43 patients, central sleep apnea in 2, and upper airway resistance syndrome in 2. The disease conditions were defined as severe in 27 patients, moderate in 12 patients, and mild in 8 patients. Each PSG cost $700 (including costs for lost transmissions) compared to $1,250 for referral to a private sleep laboratory. A savings of $550 per study was realized with the telemedicine protocol. The online transfer of PSGs from a remote site to a centralized sleep laboratory is technically feasible and clinically useful. Telemedicine offers an effective alternative for cost reduction in sleep medicine while improving patient access to specialized care in remote areas.

REM sleep and catecholamine excretion: a study in elite athletes.

We investigated the potential influence of catecholamines on sleep architecture in endurance-trained athletes. The hypothesis was that endogenous levels of aminergic neurotransmitters influence sleep architecture. Thirteen well-trained male street cyclists (all members of the German national amateur team, mean age 23.9 years, mean body mass index 21.9 kg/m2) completed the protocol. Each subject was studied during training after a race competition (C) and later in a recovery/rest period (R) with no training and no competition. Polysomnography (PSG) was performed for one night (C) and for a second night some weeks later (R). Urinary levels of catecholamines collected during the preceding day and over the night of PSG were used as an index of excretion rate of circulating adrenergic agonists. Nighttime and daytime excretion of epinephrine and norepinephrine was significantly elevated after exercise (C vs R; P<0.01). Rapid-eye-movement sleep (REM) onset latency was significantly increased (P=0.03) and REM was significantly decreased in the first half of the night in the training compared to the resting condition (C vs R, P=0.05). REM latency was correlated with increased epinephrine excretion on the day of exercise (C, r=0.63, P=0.02). The temporal appearance of REM during the night appears to be affected in part by the intense exercise associated with race competition, and urinary catecholamines are markers that are correlated with this alteration in REM appearance.

Application of telemedicine to sleep medicine.

Polysomnograms (PSGs) in specialized sleep centers with physicians and technicians trained in sleep medicine are still considered to be the most accurate form of diagnosis in patients with sleep disorders. But they are also very costly. Internet online transfer of PSGs from nonstaffed to very well-staffed sleep centers might be a solution in the future to reduce costs.

Using the Berlin Questionnaire to identify patients at risk for the sleep apnea syndrome.

BACKGROUND: Although sleep apnea is common, it often goes undiagnosed in primary care encounters. OBJECTIVE: To test the Berlin Questionnaire as a means of identifying patients with sleep apnea. DESIGN: Survey followed by portable, unattended sleep studies in a subset of patients. SETTING: Five primary care sites in Cleveland, Ohio. PATIENTS: 744 adults (of 1008 surveyed [74%]), of whom 100 underwent sleep studies. MEASUREMENTS: Survey items addressed the presence and frequency of snoring behavior, waketime sleepiness or fatigue, and history of obesity or hypertension. Patients with persistent and frequent symptoms in any two of these three domains were considered to be at high risk for sleep apnea. Portable sleep monitoring was conducted to measure the number of respiratory events per hour in bed (respiratory disturbance index [RDI]). RESULTS: Questions about symptoms demonstrated internal consistency (Cronbach correlations, 0.86 to 0.92). Of the 744 respondents, 279 (37.5%) were in a high-risk group that was defined a priori. For the 100 patients who underwent sleep studies, risk grouping was useful in prediction of the RDI. For example, being in the high-risk group predicted an RDI greater than 5 with a sensitivity of 0.86, a specificity of 0.77, a positive predictive value of 0.89, and a likelihood ratio of 3.79. CONCLUSION: The Berlin Questionnaire provides a means of identifying patients who are likely to have sleep apnea.