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LITERATURE
MONITOR: A REVIEW
OF
RECENTLY PUBLISHED CLINICAL
ARTICLES
BREATHING PATTERNS PREDICT HEART FAILURE
Daytime oscillatory breathing patterns are common among patients with chronic heart failure and appear to be associated with a poor outcome and an increased prevalence of ventricular arrhythmias, according to a report by Ponikowski et al.
Power spectral analysis was applied to 30-minute recordings of respiration in 74 patients with stable chronic heart failure. Heart rate and blood pressure were monitored continuously, and peripheral chemosensitivity was measured by inducing transient hypoxia (via nitrogen inhalation).
Oscillatory breathing--rises
and falls in ventilation with apnea (Cheyne-Stokes respiration) or without
apnea (periodic breathing)--were found in 22 and 27 patients, respectively.
These respiratory patterns were significantly associated with more advanced
heart failure symptoms, impaired autonomic balance, and increased chemosensitivity.
Over half the patients
with either Cheyne-Stokes respiration (53%) or periodic breathing (52%)
had nonsustained ventricular tachycardia, compared with only 10% of those
with normal respiratory patterns. The two-year survival rate was lower
in patients with oscillatory respiratory patterns (67%) than in patients
with normal breathing patterns (96%), the researchers found.
Eight patients with
reproducible oscillatory breathing received 100% oxygen delivered via
face mask for 20 minutes. Oxygen exposure abolished the oscillations in
seven of the patients, but breathing abnormalities resumed within 20 minutes
when the patients again breathed room air. Similarly, dihydrocodeine administration
decreased peripheral chemosensitivity by 42%, and this fall correlated
with improvement in the respiratory pattern. Thus, "modulation of
peripheral chemosensitivity could be a therapeutic option in [chronic
heart failure] patients with cyclical breathing," the researchers
noted.
The patients with Cheyne-Stokes
respiration and the patients with periodic breathing were not significantly
different in terms of clinical parameters, autonomic indices, or peripheral
chemosensitivity. The researchers hypothesized that these oscillatory
breathing patterns "represent two aspects of the same phenomenon
(which could be referred to as cyclical respiration), with similar pathophysiologic
mechanisms involved." In fact, some of the patients alternately showed
Cheyne-Stokes respiration or periodic breathing on consecutive visits.
Ponikowski P, Anker
SD, Chua TP, et al. Oscillatory breathing patterns during wakefulness
in patients with chronic heart failure: clinical implications and role
of augmented peripheral chemosensitivity. Circulation. 1999;100:2418-2424.
FUNCTIONAL
AIRWAY OBSTRUCTION CAN MIMIC TONGUE ANGIODEMA
Tongue swelling leading
to upper airway obstruction in a 12-year-old girl was determined to be
a conversion reaction rather than angioedema, according to a recent case
reported by Nordness et al. "The findings in this case suggest that
even abnormal physical and radiographic findings can be present in functional
airway obstruction," the study investigators concluded.
The girl initially presented
with a sore throat and ear pain without fever. Later, her throat pain
worsened, she had difficulty swallowing, and her voice became weak. She
was hospitalized for two days and treated with ß2-agonist
bronchodilators, antihistamines, corticosteroids, and cefprozil. However,
the day following discharge, she presented to an emergency department
with breathing difficulties, swelling under the chin, and a weak voice.
In spite of her condition, the researchers noted that she was calm, cooperative,
and did not appear to be in distress.
Severe, posterior-third
tongue swelling was found on lateral neck radiograph, and soft tissue
fullness at the base of the tongue with no associated lymphadenopathy
was found on computed tomography. She underwent direct laryngoscopy and
biopsy of the tongue base; tongue biopsies were normal. Interestingly,
"with anesthetic induction, there was complete relaxation of the
upper airway with no evidence of tongue swelling, masses, or other abnormalities,"
the researchers explained.
Following surgery, she
had no further evidence of tongue mass or breathing difficulties. Her
primary care physician noted that the girl acted "unusual" during
office visits and that the "dynamics between her family were odd."
Functional airway obstruction
commonly occurs in young female adolescents under psychological stress
or with a history of respiratory problems, the researchers explained.
"The term la belle indifference has been used to describe the lack
of concern the patient demonstrates to the respiratory distress,"
they added. These patients do not respond to medications and usually benefit
from relaxation techniques, neck extension, and verbal support. The diagnosis
"is one of exclusion and should be considered if other causes of
airway obstruction are excluded," the researchers concluded.
Nordness ME, Zacharisen
MC. Functional airway obstruction mimicking tongue angioedema. Ann
Allergy Asthma Immunol. 1999;83:540-542.
RAMPANT
MISUSE OF ASTHMA MEDICATIONS
Results from a large
survey reveal that 16% of patients who use inhaled ß-agonists overuse
these drugs and that 64% of patients who use inhaled corticosteroids underuse
their medication.
Diette et al examined
data from the Managed Health Care Association Outcomes Management System
Consortium Asthma Study, which included 6,612 health plan enrollees (age
18 years and older) with asthma.
Among the 5,718 patients
with moderate or severe asthma, 94% reported using inhaled ß-agonists
for short-term asthma relief, and 67% took inhaled corticosteroids for
long-term management. However, 16% of the patients receiving ß-agonists
reported overuse (more than eight puffs per day on days of use), and 64%
of the inhaled corticosteroid recipients reported underuse (four or fewer
puffs per day or use on four or fewer days per week).
Table
1
PATIENT CHARACTERISTICS ASSOCIATED
WITH ASTHMA MEDICATION MISUSE
|
| Variable |
Overuse
of ß-agonists |
Underuse
of Corticosteroids |
| Use
of other asthma medications |
Greater |
Lower |
| Peak
flow meter in home |
Present |
Absent |
| Asthma
severity |
Increased |
Decreased |
| Knowledge
of asthma |
Increased |
Decreased |
| Number
of office visits for asthma |
Increased |
Decreased |
| Gender |
Male |
Female |
| Satisfaction
with health care |
Greater |
Lower |
| Other |
Having
problems obtaining asthma medication |
Nonwhite race
Younger age
(18 to 34 years)
|
| Data
extracted from Diettle GB et al. Arch Intern Med. 1999. |
Both patient and provider
characteristics were found to influence medication misuse. Patient characteristics
associated with overuse or underuse are listed in Table 1. Overuse of
ß-agonists was significantly less likely to occur among patients of
allergists than among patients of generalists, but was more likely to
occur among patients of pulmonologists. In addition, the study found that
underuse of inhaled corticosteroids was significantly more likely to occur
among patients treated by generalists than among patients treated by the
other two physician types.
Diette GB, Wu AW, Skinner
EA, et al. Treatment patterns among adult patients with asthma: factors
associated with overuse of inhaled beta-agonists and underuse of inhaled
corticosteroids. Arch Intern Med. 1999;159:2697-2704.
IS
S AUREUS RESISTANT TO VANCOMYCIN?
Staphylococcus aureus
may be developing resistance to vancomycin, warned the Centers for Disease
Control and Prevention (CDC) in a report of the fourth known case of vancomycin-resistant
S aureus. This is somewhat alarming because nosocomial methicillin-resistant
S aureus (MRSA) is already common, and vancomycin is the last line
of defense against it.
The case involved a
63-year-old woman with end-stage renal disease who had a history of frequent
hospitalizations and intermittent treatment with vancomycin. Her most
recent hospitalization (in April 1999) was for MRSA bacteremia, which
had developed despite nearly two weeks of vancomycin therapy.
The patient continued
to receive vancomycin in the hospital. Nevertheless, a blood culture 13
days after admission grew S aureus with a minimum inhibitory concentration
(MIC) of 4 µg/mL. The patient's median serum vancomycin concentration
was 12.7 µg/mL at that time. Three subsequent blood cultures over the
next three days grew S aureus with MICs of 8 µg/mL.
The patient died from
endocarditis 10 days after the first culture. Subsequent testing found
that her S aureus isolate was susceptible to vancomycin at a MIC
of 4 to 8 µg/mL, depending on the test method.
The CDC confirmed these
findings and concluded that the isolate had an intermediate level of vancomycin
resistance. No such S aureus isolates were recovered from other
sites on the patient's body, nor was there evidence of transmission to
her family members, health care workers, or other patients.
The Centers for Disease
Control and Prevention. Staphylococcus aureus with reduced susceptibility
to vancomycin--Illinois, 1999. MMWR Morb Mortal Wkly Rep. 2000;48:1165-1166.
PREVENTING
AIDS-RELATED OPPORTUNISTIC ILLNESSES
Potent antiretroviral
therapy reduces the incidence of opportunistic illnesses in patients infected
with the human immunodeficiency virus (HIV), according to data from the
Swiss HIV Cohort Study. A low baseline CD4 cell count was the strongest
predictor of disease progression after initiation of antiviral therapy
and may be used to detect patients who require close clinical surveillance.
Ledergerber et al examined
the effects of potent antiretroviral therapy (ie, at least three antiretroviral
drugs, including a protease inhibitor) among 2,410 HIV-infected patients.
Each subject was followed for at least 15 months after the start of treatment.
The incidence of opportunistic
illnesses per 100 person-years decreased from 15.1 in the six months before
therapy initiation to 7.7 in the first three months after the treatment's
start, 2.6 in the next six months, and 2.2 between nine and 15 months.
This decrease ranged from a 38% reduction per month for Kaposi's sarcoma
to a 5% reduction per month for non-Hodgkin's lymphoma.
Compared with the rest
of the cohort, patients with a low baseline CD4 cell count, a high baseline
viral load, advanced clinical stage, or older age had a significantly
increased risk of opportunistic illness after starting antiretroviral
therapy. Of these variables, baseline CD4 cell count was the best predictor
of disease progression, with an almost threefold increased risk for cell
counts of 51 to 200 X 106/L and an almost sixfold
increased risk for cell counts of 50 X 106/L
or below (the comparison was with cell counts above 200 X 106/L).
Furthermore, two factors--a
CD4 cell count that rose by 50 X 106/L or more
and undetectable levels of HIV-1 RNA in plasma (fewer than 400 copies/mL)--were
associated with a markedly lower risk of an opportunistic illness after
the initial six months of antiretroviral therapy (hazard ratios, 0.32
and 0.39, respectively).
Ledergerber B, Egger
M, Erard V, et al. AIDS-related opportunistic illnesses occurring after
initiation of potent antiretroviral therapy: the Swiss HIV Cohort Study.
JAMA. 1999;282:2220-2226.
CAN
PATIENT EDUCATION IMPROVE COMPLIANCE?
An educational intervention
aimed at self-management improved inhaled corticosteroid compliance among
patients with asthma, according to a recent report by Gallefoss et al.
In patients with chronic obstructive pulmonary disease (COPD), the intervention
reduced the need for short-acting inhaled ß2-agonists
but did not alter inhaled corticosteroid compliance.
A total of 140 patients
(age range, 18 to 70 years) with mild to moderate bronchial asthma or
COPD were randomized to an education intervention or traditional treatment;
patients were then followed for one year. The intervention consisted of
two 2-hour group sessions and one or two individual sessions with a trained
nurse and physiotherapist. Individual self-management plans were devised
based on personal information and findings from two weeks of peak flow
monitoring. Outcome analysis was based on dispensed medication reports
from local pharmacies. Patients were defined as compliant if their dispensed
regular medication was greater than 75% of their prescribed regular medication.
The intervention produced
an almost twofold increase in the proportion of asthmatic patients who
complied with inhaled corticosteroid use (57% vs 32%). In contrast, no
such improvement was found among the COPD patients. Furthermore, the intervention
did not affect oral corticosteroid use in either group. However, rescue
ß2-agonist administration declined markedly
in both groups, although only among the COPD patients did this decrease
reach statistical significance.
While previous self-management
studies have shown improved inhaler compliance with education, "the
present study is the first to show such a finding when compliance is not
self-reported," the researchers noted.
Gallefoss F, Bakke
PS. How does patient education and self-management among asthmatics and
patients with chronic obstructive pulmonary disease affect medication?
Am J Respir Crit Care Med. 1999;160:2000-2005.
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