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Biomedical subjects

N M al-Saady

Publications and source records attributed to N M al-Saady.

8 recordsLinked to original sources
PubMed1995

External high frequency oscillation in normal subjects and in patients with acute respiratory failure.

External high frequency oscillation was performed on 20 healthy volunteers using a cuirass-based system, the Hayek Oscillator. Five-min periods of oscillation were carried out on each subject at frequencies of 1, 2, 3, 4 and 5 Hz. Effective ventilation was measured in terms of the fall in alveolar partial pressure of carbon dioxide immediately after oscillation. The optimum frequency for oscillation was 1-3 Hz but most of the subjects were adequately ventilated over a wide range of frequencies. Thus, the Hayek Oscillator is capable of adequately ventilating normal subjects by means of chest wall oscillation. We also compared external high frequency oscillation with intermittent positive pressure ventilation in five patients with respiratory failure. Using the same inspired oxygen fraction, the external high frequency oscillation replaced intermittent positive pressure ventilation for a 30-min period. External high frequency oscillation improved oxygenation by 16% and reduced the arterial carbon dioxide by 6%. These preliminary findings suggest that normal subjects and intensive care unit patients can be adequately ventilated by means of external high frequency oscillation.

Acute Disease↗
PubMed1995

The Hayek oscillator. Nomograms for tidal volume and minute ventilation using external high frequency oscillation.

The Hayek Oscillator is a recent development in external high frequency ventilation and is a useful mode of ventilatory support during anaesthesia, in chronic respiratory failure and weaning in intensive care. The Hayek Oscillator is new and its application is growing, as are the number of patients who have benefited from its use. However, there are no clear guidelines on how best to adjust the oscillator to achieve optimum ventilation. A simple method of predicting changes in tidal volume and minute ventilation following adjustment would make the oscillator more useful. We present nomograms for tidal volume, minute ventilation and effective alveolar ventilation when the three variables, oscillator frequency, mean chamber pressure and peak-to-trough pressure span were adjusted. The frequency-tidal volume relationship was unaffected by a mean chamber pressure of 0, -5, -10 cmH2O, but altered with changes in peak-to-trough pressure span. We have also determined the effect of increasing negative extrathoracic pressure on functional residual capacity. The relationship between tidal volume and frequency was non-linear and related to the peak-to-trough pressure span. Mean functional residual capacity significantly increased from 2.25 l (SEM 0.10) without the cuirass at rest to 2.61 l (SEM 0.14) at -10 cmH2O (p < 0.05; n = 5) and 2.47 (SEM 0.12) at -20 cmH2O of mean chamber pressure. Vital capacity was unchanged by increasing extrathoracic pressure as was total lung capacity.

Adult↗
PubMed1993

Early results of intravascular oxygenation.

We have used the intravascular oxygenator (IVOX) in eight patients (14-76 years) with acute respiratory failure. At the time of referral for IVOX all patients were on inotropic support, five had pneumothoraces and two were on haemofiltration. Ventilatory data before IVOX were: ventilated for 2-14 days (median 6), PEEP 5-12 cm H2O (12), PIP 34-95 cm H2O (49), FiO2 0.7-1 (1), PaO2 5.4-26 KPa (8.5) and PaCO2 3.7-23 KPa (8). The intravascular oxygenator was used for 6 h-12 days (median 4), the oxygen transfer achieved was 68-140 ml/min (85) and the carbon dioxide removed was 40-106 ml/min (59). It was possible to decrease the ventilator settings with a significant increase in the PaO2 by 48 h (P < 0.05) but the fall in PaCO2 did not reach significance. As the IVOX was turned from "off" to "on" the mean PaO2 increase was 0.35 KPa +/- 0.14 SEM (P = 0.04) and the mean PaCO2 decrease 0.7 KPa +/- 0.2 SEM (P = 0.02) without any significant change in cardiac output. Two patients survived and six died from multisystem failure with three patients being hypoxic at the time of death. Postmortem examinations on five patients did not reveal any IVOX-related complications. We conclude that IVOX is safe but it is not as efficient in gas exchange as extracorporeal membrane oxygenation at present. Further improvement in the gas exchange efficiency of this prototype could render IVOX a very useful device.

Acute Disease↗
PubMed1989

High fat, low carbohydrate, enteral feeding lowers PaCO2 and reduces the period of ventilation in artificially ventilated patients.

The objective of this study was to compare the effect of a high fat, low carbohydrate enteral feed with a standard isocaloric, isonitrogenous enteral feed on PaCO2 and ventilation time in patients with acute respiratory failure requiring artificial ventilation. 20 clinically stable patients requiring enteral feeding were randomized to either feed in a double-blind fashion. Initial ventilator standard settings were adjusted according to clinical state. Measurements including minute volume and arterial blood gases were made twice daily. Weaning was carried out according to set criteria. During the feeding period, PaCO2 just prior to weaning fell by 16% in the high fat group but increased by 4% in the standard feed group (p = 0.003). The high fat group spent a mean of 62 h less time on the ventilator (p = 0.006). A high fat, low carbohydrate enteral feed appears to be beneficial in patients undergoing artificial ventilation.

Adult↗
PubMedDate not supplied

Intravascular oxygenation with the IVOX.

Improvements in hollow fibre gas transfer membranes have enabled the development of an intravascular oxygenator which for the first time provides gas exchange without the need for an extracorporeal circuit. We describe all aspects of the clinical utilization of the intravascular oxygenator device.

Animals↗