Peter Powles

• McMaster University

Recent years have brought growing recognition of the need for clinical criteria for myalgic encephalomyelitis (ME), which is also called chronic fatigue syndrome (CFS). An Expert Subcommittee of Health Canada established the Terms of Reference, and selected an Expert Medical Consensus Panel representing treating physicians, teaching faculty and res...

The label 'chronic fatigue syndrome' (CFS) has persisted for many years because of the lack of knowledge of the aetiological agents and the disease process. In view of more recent research and clinical experience that strongly point to widespread inflammation and multisystemic neuropathology, it is more appropriate and correct to use the term 'myal...

Evidence is growing that sleep problems in adolescents are significant impediments to learning and negatively affect behaviour, attainment of social competence and quality of life. The objectives of the study were to determine the level of sleepiness among students in high school, to identify factors to explain it, and to determine the association...

Recent years have brought growing recognition of the need for clinical criteria for myalgic encephalomyelitis (ME), which is also called chronic fatigue syndrome (CFS). An Expert Subcommittee of Health Canada established the Terms of Reference, and selected an Ex- pert Medical Consensus Panel representing treating physicians, teaching faculty and r...

To evaluate the efficacy of inhaled nitric oxide (iNO) on oxygenation, shunt, and pulmonary vascular resistance index (PVRI) in severely hypoxemic, ventilated patients. In a two-period double-blind crossover design, 14 critically ill, hypoxemic, ventilated patients were randomized to receive iNO 10 ppm in 100% oxygen or no iNO in 100% oxygen for 30...

Continuous lateral rotational therapy (CLRT) <40 degrees is a method of altering the position of the ventilated patient to help clear secretions from the lung. CLRT has not been shown to reduce the incidence of atelectasis or pneumonia but potentially offers a way to maximize positional drainage in these patients without producing adverse effects....

Objective: To evaluate the clinical and economic consequences of clinically important gastro-intestinal bleeding (CIB) in patients admitted to the intensive care unit (ICU). Design: Prospective, cohort study. Setting: Four university-affiliated hospitals in Canada. Patients and methods: Consecutive patients over 16 years of age admitted to the ICU...

Medical residency programs are likely to face increasing pressure to address their relations with the pharmaceutical industry. Our internal medicine residency program has developed guidelines that were adopted after extensive debate by residents and faculty members. The guidelines are based on the principles that residents and faculty should set th...

Objective: To determine physicians' assessment of the therapeutic effect and patient benefit of data obtained from right heart catheterization. Design: Before/after study. Setting: One medical and one surgical academic ICU in two medical centers. Patients: A total of 107 critically ill patients with uncertain hemodynamic status. Data Collection: Ph...

Using the medical literature to solve patient problems is challenging and rewarding. For intensive care physicians, this evidence-based medicine approach is more compelling when basic critical appraisal skills are developed. We highlight the important methodological points for interpreting the literature on treatment, using a cogent example from th...

Objective: To determine physicians' assessment of the therapeutic effect and patient benefit of data obtained from right heart catheterization. Design: Before/after study. Setting: One medical and one surgical academic ICU in two medical centers. Patients: A total of 107 critically ill patients with uncertain hemodynamic status. Data Collection: Ph...

To obtain data on oxygen use among hospital inpatients criteria for instituting, monitoring, and stopping oxygen therapy were formulated. The records of 90 consecutive patients who had been started on oxygen therapy outside the critical care areas of a university hospital were then examined. By the criteria, 79% of patients were deemed to have requ...

This study was performed to determine the roles of increased intrathoracic blood volume and increased vagal tone in the changes in lung volume and nitrogen washout produced by saline infusion. In the first study, measurements of TLC, VC, FRC, ERV, and slope of phase III nitrogen washout (delta N2) were made on 8 subjects before, during, and after i...

The study compares two popular forms of written tests; the multiple choice test (MCQ) and the Modified Essay Question (MEQ). Two factors were varied in the experiment: the format of the questions (multiple choice, directed free response, or open-ended free response) and the context of the questions (in a patient problem or in random sequence). Six...

the arterial hypdxemia that occurs in all subjects acutely exposed to high altitude lessens over succeeding days and weeks through ventilatory acclimatization (2). If acclimatization proceeds normally, the partial pressure of oxygen (Po 2) in arterial blood increases over time. If acute mountain sickness (AMS) intervenes and becomes severe, however...

A pocket calculator program is described which facilitates rapid evaluation of pulmonary function at rest and during exercise. It embodies the Fick Principle applied to carbon dioxide; mixed venous carbon dioxide tension is measured by rebreathing, obviating the need for central venous or pulmonary artery catheterisation. The program is in two part...

Disturbance of sleep is common at high altitude and is frequently due to cold and other physical discomforts. However, it may also be a manifestation of acute mountain sickness (12,20,23). The tragic story of Dr. Jacottet, who died in the Vallot hut on Mont Blanc, illustrates this point. In a letter to his brother in Vienna, Sept. 1, 1891, he said,...

The effect of digoxin on the right and left ventricular ejection fractions in 15 patients with pulmonary heart disease caused by severe chronic airflow obstruction was studied in a double-blind, randomized, placebo-controlled trial. All patients were ambulatory and had clinical features of right but not left ventricular dysfunction. Equilibrium rad...

Anti-hypertensives, diuretics, digitalis, beta-blockers, nitrates, anti-arrhythmics, and psychiatric drugs are reviewed for their effects on the cardiovascular response to exercise, in particular work capacity, heart rate, blood pressure, anginal threshold, and exertional arrhythmias. The limitations of these measurements to assess changes in the v...

A pocket calculator program has been written for the rapid bedside evaluation of cardiorespiratory function. The unique features of this program are that it makes use of recently available non-invasive techniques for measurement of arterial oxygen saturation and mixed venous PCO2. This enables calculation of pulmonary venous admixture and mixed ven...

Forty-two interns and residents on the staff of a community teaching hospital were questioned to assess their understanding of blood gas abnormalities. Misunderstandings were such that 24% of the residents and interns might have given inadequate care had their interpretations dictated practice. Few therapeutic misadventures in fact occurred, largel...

Unless cardiac output is reduced, alveolar ventilation can be monitored without arterial blood gas analysis by estimating arterial carbon dioxide tension (PaO2) from rebreathing measurement of mixed venous carbon dioxide tension (PvCO2) (PaCO2 = 0.8 PvCO2). If cardiac output is reduced, the PvCO2 - PaCO2 difference increases, reflecting the increas...

The mixed venous carbon dioxide tension (PVCO2) can be measured at the bedside by a rebreathing equilibrium technique that is quick, simple and noninvasive. Only one brief period of rebreathing is required. The technique is accurate even when the lungs are not normal, and gives a graphic record that allows verification of the accuracy of the estima...

The intrinsic sinoatrial (SA) rate at rest and during exercise was measured in 5 normal male subjects after prolonged oral and acute intravenous administration of propranolol and atropine. At rest, the intrinsic SA rate was similar after both oral and intravenous propranolol. At the higher levels of power output on a cycle ergometer, cardiac rate w...

The accuracy of three ear oximeters (Waters XP-350, Waters 0-1100, Hewlett-Packard 47201A) was evaluated on 52 subjects during acute progressive and steady-state hypoxia. Ear oximeter readings were compared with measured arterial saturation (SAO2) in arterial or "arterialized" capillary blood samples. Hewlett-Packard (HP) 47201A ear oximeter readin...

1. To investigate the interaction of hypoxaemia and blood Pco2 in the production of cerebral hypoxia, we studied six healthy men in whom acute progressive hypoxia was induced by using a re-breathing technique, while the Pco2 was kept constant. 2. At least two blood Pco2 tensions were studied in each subject. Arterial oxygen saturation was monitored...