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Biomedical subjects

P D Macnaughton

Publications and source records attributed to P D Macnaughton.

8 recordsLinked to original sources
PubMed1994

Measurement of lung volume and DLCO in acute respiratory failure.

We have undertaken rebreathing measurements of functional residual capacity (FRC), carbon monoxide diffusing capacity (DLCO), and diffusing coefficient (KCO) during positive pressure ventilation in 15 patients with adult respiratory distress syndrome (ARDS). Measurements of oxygenation (PaO2:FIO2 ratio) and lung injury score (LIS) were also recorded. Eight patients subsequently died (mortality of 53%). There was no significant difference in mean FRC, PaO2:FIO2, or LIS at presentation between survivors and nonsurvivors. However, both DLCO and KCO at presentation were significantly greater in survivors than nonsurvivors. In a separate study of nine patients with less severe lung injury, pulmonary capillary blood volume, derived from values of DLCO measured at two different values of FIO2, correlated with invasive pulmonary vascular resistance (PVR) measurements (r = 0.84, p < 0.01). DLCO measurements can be successfully undertaken in patients being ventilated with acute lung injury and may be a useful, noninvasive method of assessing the pulmonary circulation. The lowest values of DLCO were recorded in patients who subsequently did not survive.

Acute Disease↗
PubMed1994

The effect of exogenous surfactant therapy on lung function following cardiopulmonary bypass.

OBJECTIVE: Pilot study to investigate the effect of exogenous surfactant therapy on lung function following cardiopulmonary bypass (CPB). DESIGN: Prospective randomized controlled study. SETTING: Adult intensive care unit of a postgraduate cardiothoracic hospital. PATIENTS: Sixteen adult patients undergoing elective coronary artery revascularization surgery without a history of preoperative respiratory disease. INTERVENTIONS: Artificial lung-expanding compound (ALEC, Britannia Pharmaceuticals, Crawley, UK) 3.2 g, was given via a bronchoscope 60 min after bypass in eight patients. Eight control subjects received air. MAIN OUTCOME MEASUREMENTS: Lung function tests during IPPV (arterial blood gas tensions, Crs, FRC, TLco, KCO) were measured prior to CPB, before therapy, and at regular intervals up to 180 min afterwards. RESULTS: The CPB caused a significant impairment of lung function in both groups with an increase in A-a gradient (+47 +/- 11 mm Hg in the ALEC group and +44 +/- 17 mm Hg in controls) and reductions in FRC (-290 +/- 121 ml in the ALEC group and -470 +/- 132 ml in controls), TLco (-1.6 +/- 0.3 ml/min/mm Hg in the ALEC group and -2.2 +/- 0.3 ml/min/mm Hg in controls), and Crs (-10 +/- 1 ml/cm H2O in the ALEC group and -21 +/- 4 ml/cm H2O in controls). The ALEC therapy did not affect A-a gradient, FRC, and Crs compared with controls. However, TLco was significantly lower in the ALEC group following therapy (120 min after treatment -0.1 +/- 0.3 ml/min/mm Hg in ALEC group and +1.0 +/- 0.3 ml/min/mm Hg in controls). CONCLUSIONS: A single 3.2-g dose of ALEC administered as a bolus bronchoscopically does not improve lung function following CPB and may impair gas transfer.

Adult↗
PubMed1993

Measurement of carbon monoxide transfer and lung volume in ventilated subjects.

A simple method for measuring lung volume and carbon monoxide transfer factor (TLCO) by a rebreathing technique was assessed in nine healthy volunteers undergoing intermittent positive pressure ventilation (IPPV). Measurements of TLCO, alveolar volume (VA) and carbon monoxide transfer coefficient (KCO) made at three inspired oxygen concentrations (21, 35 and 70%) during IPPV were compared to those obtained during spontaneous breathing. The effects of 10 cmH2O positive end expiratory pressure (PEEP) were also studied. Pulmonary capillary blood volume (Vc) and the diffusing capacity of the alveolar capillary membrane (Dm) were derived. There was a close correlation between measurements of TLCO during IPPV (TLCOIPPV) and spontaneous breathing (TLCOSV) (r = 0.92). Ventilated TLCO was 64 +/- 8% of spontaneously breathing TLCO. There was a close agreement between ventilated and spontaneously breathing measurements of KCO (r = 0.95; mean difference 0.14, 95% limits of agreement +0.37 to -0.09 mmol.min-1 x kPa-1 x l-1). Vc was 92 +/- 23 ml during spontaneous breathing and 72 +/- 21 ml during IPPV (p < 0.05). PEEP of 10 cmH2O significantly increased functional residual capacity (2.3 +/- 0.5 to 3.5 +/- 0.6 l) and decreased TLCO (5.9 +/- 1.0 to 5.3 +/- 1.2 mmol.min-1 x kPa-1), KCO (1.7 +/- 0.2 to 1.1 +/- 0.3 mmol.min-1 x kPa-1 x l-1) and Vc (82 +/- 22 to 56 +/- 20 ml). Dm did not change with PEEP. This simple method may be a useful means of assessing gas exchange and lung volume in ventilated subjects. It showed that PEEP increased lung volume but reduced TLCO and that this reduction appeared to be due to a reduction in capillary blood volume.

Adult↗
PubMed1992

Changes in lung function and pulmonary capillary permeability after cardiopulmonary bypass.

OBJECTIVE: To assess the possibility that changes in lung function following cardiopulmonary bypass are associated with increased pulmonary capillary permeability. DESIGN: A prospective, descriptive study. SETTING: Adult cardiothoracic ICU in a post-graduate teaching hospital. PATIENTS: Ten sequential patients undergoing cardiac surgery requiring cardiopulmonary bypass. MEASUREMENTS: Arterial blood gas tensions, helium dilution end-expiratory lung volume, and carbon monoxide transfer were measured by a rebreathing technique preoperatively and 2 hrs postoperatively. Lung extravascular protein accumulation index was measured by a double-isotope technique 2 hrs postoperatively and in a group of normal controls. RESULTS: Mean +/- SEM alveolar-arterial PO2 gradient increased from 77 +/- 14 torr (10.3 +/- 1.8 kPa) to 138 +/- 24 torr (18.5 +/- 3.2 kPa) (p less than .01). Functional residual capacity decreased by 20.2 +/- 5.6% (p less than .01). Carbon monoxide transfer decreased by 26.7 +/- 5.3% (p less than .01) for the lung as a whole and by 17.9 +/- 3.2% (p less than .01) per liter of accessible gas volume. Protein accumulation index ranged from 0.03 to 3.2 x 10(-3) (median 0.6) postoperatively (median for normal subjects 0.4; p less than .05), although only one patient had a value indicative of clinically important endothelial injury. CONCLUSIONS: Cardiac surgery involving cardiopulmonary bypass results in a deterioration in lung function characterized by a loss of lung volume, a reduction in carbon monoxide transfer, and an increase in the alveolar-arterial PO2 gradient. These changes do not appear to be mediated by an increase in pulmonary endothelial permeability.

Aged↗
PubMed1990

Pulmonary function testing in the intensive care unit.

A number of tests of pulmonary function have been successfully developed for use in the intensive care unit. When performed in the ICU on critically ill patients, many of the traditional laboratory-based tests will have different clinical implications than when performed in ambulatory patients, for example vital capacity measurement. Also, the clinical questions posed in the ICU are often different, such that estimates of lung water may be clinically more useful than more traditional measures, such as the flow-volume loop. There is a need for further research to identify the clinical utility of these measurements. As the understanding of ARDS and MOF improves, new therapies may be developed which will require sensitive methods in order that they can be evaluated accurately. Similarly, the potential for new methods of respiratory support such as jet ventilation, extracorporeal techniques and lung transplantation reinforce the need for the pulmonary physician to be able to make an accurate assessment of respiratory function on the intensive care unit.

Extravascular Lung Water↗