PubMed Health⌕ Search

Biomedical subjects

A T Aquilina

Publications and source records attributed to A T Aquilina.

8 recordsLinked to original sources
PubMed1998

Clinical and radiographic manifestations of uncommon pulmonary nontuberculous mycobacterial disease in AIDS patients.

STUDY OBJECTIVE: To determine the clinical and radiographic findings of nontuberculous mycobacteria (NTM) other than Mycobacterium avium complex (MAC) and Mycobacterium kansasii in AIDS compared with non-AIDS patients. DESIGN: A retrospective chart review of all patients in whom NTM other than MAC complex and M kansasii were isolated between April 1, 1989, and October 31, 1995. SETTING: University-affiliated hospital. PATIENTS: Fifty-four patients met the criteria for uncommon pulmonary NTM disease: (1) repeated isolation of atypical mycobacterium in colony counts of > or = 3 from two or more sputum specimens; or isolation of the organism from transbronchial or open lung biopsy specimen with histologic changes suggestive of mycobacterial disease in the absence of other pathogens; and (2) either an abnormal chest radiograph, the cause of which had not been attributed to an active infection other than atypical mycobacterial disease; or the presence of one or more symptoms indicative of pulmonary disease coupled with exclusion of other illnesses with similar symptoms and signs. RESULTS: Thirty-five patients were HIV positive. Fever was the only clinical symptom more commonly seen in HIV-infected patients with NTM than non-HIV-infected patients. Sixty-six percent of all patients with AIDS were infected by Mycobacterium xenopi. Chest radiographs of AIDS patients showed a tendency for predominance of interstitial infiltrate and rarity of fibronodular disease. No specific radiographic pattern was observed for any particular organism. Adenopathy was not a feature of uncommon pulmonary NTM in AIDS, and it should suggest an alternate diagnosis. In two patients, NTM isolation from respiratory specimens preceded dissemination. Six of 8 AIDS patients treated for pulmonary NTM remained alive at the end of the study compared with only 4 of 15 patients who were not treated for pulmonary NTM (p<0.05). CONCLUSIONS: Uncommon NTM isolated from respiratory specimens ought to be considered as serious pathogens in the presence of clinical and radiographic manifestations unexplained by other pathologic processes. Colonization with NTM could precede dissemination. Treatment of uncommon pulmonary NTM disease could possibly confer a survival benefit in AIDS patients.

AIDS-Related Opportunistic Infections↗
PubMed1990

High-frequency oscillation during simulated altitude exposure.

Ventilatory requirements using high-frequency oscillation (HFO) during simulated altitude exposure were investigated in control dogs and animals with oleic acid-induced lung injury. FIO2 values of 0.21 and 1.0 were supplied by bias flow to the normal and injured dogs, respectively. After a control period, animals were exposed to a simulated altitude of 8,000 ft (barometric pressure 564 torr), followed by a second control period at ground level. Both experimental groups had similar values of PaCO2 at ground level and during exposure to reduced barometric pressure. The tidal volume necessary to maintain eucapnia was higher in oleic acid-injured animals compared with the control group; cardiac output and functional residual capacity were lower. The alveolar-arterial oxygen difference was substantially larger in the oleic acid group. Adequate gas exchange can be maintained with HFO during exposure to altitude provided that ventilation and inspired PO2 are not reduced below normobaric levels.

Altitude↗
PubMed1990

Role of molecular diffusion in conventional and high frequency ventilation.

The influence of molecular diffusion on gas-mixing during conventional mechanical ventilation (CMV) and high frequency ventilation (HFV) was studied by observing the wash-in of six poorly soluble, inert gases in arterial blood. Anesthetized dogs were ventilated either with CMV or HFV. Following a step change in inspired gas composition, the increase in arterial concentrations of hydrogen, helium, methane, ethane, isobutane, and sulfur hexafluoride was determined by gas chromatography. The relative gas diffusivities encompassed a range of almost one order of magnitude. Propane, present in inspired gas during both the control and wash-in phases, served as an internal reference for calculation of blood tracer concentrations. The wash-in of all six inert gases followed a single exponential time course during both CMV and HFV. The rate of wash-in of each gas decreased with increasing molecular weight (MW). The relationship of rate constants to a measure of relative diffusivity (MW-0.5) was significantly different than zero for both types of ventilation. The slope of this relationship was three times larger for CMV than HFV, indicating that molecular diffusion has a greater role in gas mixing during ventilation with large tidal volumes. Diffusion has a minor role in gas mixing during high frequency ventilation with small tidal volumes. Demonstration of the presence of gas separation secondary to molecular diffusion during HFV is enhanced by measuring wash-in, rather than wash-out, of inert gases because gas separation is likely to be obscured as exhaled gases pass through the well-mixed central airways during gas wash-out.

Animals↗
PubMed1987

Air transportation of patients with acute respiratory failure: theory.

Adult respiratory distress syndrome (ARDS) that results from severe trauma often occurs in remote places, making it necessary to transport the patients to tertiary medical facilities by air. Since these severely hypoxic patients are exposed to additional risk of reduced inspired oxygen tension due to decreased barometric pressure, the feasibility of transportation of these patients was investigated by computer analysis. Mathematical models of pulmonary gas exchange in patients with ARDS were developed to calculate arterial and mixed venous blood tensions while breathing room air and oxygen at sea level, 8,000 ft, and 40,000 ft. Under each condition the following parameters were varied: alveolar ventilation (VA), cardiac output (Q), metabolic rate (VO2), hematocrit (Hcrit), and membrane diffusing capacity for oxygen (DmO2). Most of the gas exchange problems at altitude could be overcome by breathing oxygen as long as cardiac output and hematocrit were adequate. Hypoxemia in ARDS patients will not be greatly affected by the reduced inspired oxygen tensions at altitude in much the same way that hypoxemia in ARDS is poorly responsive to increased inspired oxygen tensions at sea level.

Aerospace Medicine↗
PubMed1987

Ventilatory criteria for aeromedical evacuation.

Ventilatory requirements during simulated aeromedical transportation were investigated in normal dogs and animals with oleic acid-induced lung injury. Inspired oxygen fractions of 0.21 and 1.0 were used to ventilate the normal and injured dogs, respectively. Both groups were ventilated with a constant-volume piston ventilator. After a control period, animals were exposed to a simulated altitude of 8,000 ft (barometric pressure 564 mm Hg), followed by a second control period at ground level. Both groups of animals had no change in carbon dioxide production, arterial PCO2 or ventilation during exposure to reduced barometric pressure. Systemic blood pressure, heart rate, cardiac output, and lung volume were all lower in oleic acid-injured animals than controls; the alveolar-arterial oxygen difference was larger in the oleic acid group. With altitude exposure, arterial and mixed venous oxygen tensions were decreased in both groups. Adequate gas exchange can be maintained during exposure to altitude even in animals with abnormal function provided that ventilation is constant and the inspired oxygen fraction is increased to compensate for the reduced barometric pressure.

Aerospace Medicine↗
PubMed1983

Comparison of airway reactivity induced by histamine, methacholine, and isocapnic hyperventilation in normal and asthmatic subjects.

In an investigation of a rapid screening test for airway reactivity using isocapnic hyperventilation with room air and cold air the results of this test were compared with the airway response to histamine and methacholine challenge. Twelve non-atopic, non-smoking normal subjects and 11 subjects with stable asthma who had an FEV1 above 74% of the predicted value were studied. In the normal subjects isocapnic hyperventilation with room air (75 l/min; 22 degrees C (SEM 0.2 degrees); 10 mg H2O/l air) and isocapnic hyperventilation with cold air (77 l/min; -10 degrees C (0.9 degrees); 2.4 mg H2O/l air) produced no significant change in FEV1. In the asthmatic subjects, hyperventilation with room air (71 l/min; 22 degrees C (0.8 degrees); 10 mg H2O/l air) caused a mean fall in FEV1 of 11.7%; cold air hyperventilation (70 l/min; -10 degrees C (0.9 degrees); 2.4 mg H2O/l air) caused a mean fall in FEV1 of 20.4%. Cold air hyperventilation produced greater separation between normal and asthmatic subjects than room air. The provocative concentration of histamine required to reduce the FEV1 by 20% (PC20) correlated closely with the PC20 for methacholine (r = 0.95; p less than 0.001). Both tests separated normal from asthmatic subjects. PC20 for both histamine and methacholine correlated with the fall in FEV1 after cold air hyperventilation (r = 0.93, p less than 0.001; r = 0.87, p less than 0.001 respectively). We conclude that the results of a rapid screening test based on hyperventilation with cold air correlate well with a standard pharmacological challenge.

Adult↗
PubMed1980

Airway reactivity in subjects with viral upper respiratory tract infections: the effects of exercise and cold air.

To define airway hyperreactivity further in symptomatic upper respiratory tract infection (URI), we compared in the setting of viral URI the respiratory effects of inhaling histamine to that of exercising with room air (993 +/- 300 kpm/min; 22 degrees +/- 2 degrees C), cold air breathing (-8 +/- 2 degrees C), and exercising with cold air (993 +/- 300 kpm/min; -8 degrees +/- 2 degrees C). Thirteen previously healthy, nonsmoking, nonatopic adults with URI were evaluated at the time of presentation and 1, 3, and 6 wk thereafter. At the initial presentation there was a 28 +/- 14% decrease in mean airway conductance (SGaw) after inhalation of histamine (p > 0.001). By 6 wk, airway reactivity to histamine decreased in 9 of 13 subjects. After exercise with cold air, there was a 12.5 +/- 7.5% decrease in mean SGaw (p < 0.001). By 6 wk, exercise with cold air no longer produced a decrease in SGaw (p > 0.05). In 5 additional subjects this airway reactivity to exercise with cold air was blocked by previous administration of atropine and by oropharyngeal anesthesia. We conclude that during viral URI there occurs transient airway hyperreactivity ot the combination of exercise with cold, dry air and that the upper airway and parasympathetic nervous system have important roles in these responses.

Adult↗