PubMed Health⌕ Search

Biomedical subjects

Frank Clewlow

Publications and source records attributed to Frank Clewlow.

8 recordsLinked to original sources
PubMed2007

A prospective manikin-based observational study of telephone-directed cardiopulmonary resuscitation.

INTRODUCTION: Bystander cardiopulmonary resuscitation (CPR) significantly improves the outcome from sudden cardiac arrest (SCA) and is therefore encouraged by offering telephone instructions to the bystander. The effectiveness of this technique was examined in a manikin-based study. METHODS: Subjects performed CPR on an instrumented adult manikin by following Advanced Medical Priority Dispatch System v11.1 (AMPDS) instructions given by telephone from a different room. RESULTS: Fifty-one volunteers (26 males, median age 56, range 27-76 years) with no previous experience of CPR were recruited. No volunteers followed the entire instructions correctly. Forty percent were unable to open the airway, only 18% achieved a median inspiration time of 2 s or greater and only 30% delivered tidal volumes within the range 700-1000 ml. Chest compressions were performed at a median rate of 52 min-1 with only 4% of subjects achieving a rate of 100 min-1. Depth of compression was also inadequate in 88% of subjects and hand positioning was incorrect in a third of subjects. The median duty cycle was 46% and there were significant delays between the commencement of the AMPDS protocol and the delivery of the first breath (123 s) and first chest compression (163 s). DISCUSSION: Few bystanders perform CPR satisfactorily and further work is necessary to improve the effectiveness of telephone CPR instructions.

Adult↗
PubMed2004

Comparison of the effects of removal of chest hair with not doing so before external defibrillation on transthoracic impedance.

Chest hair contributes significantly to transthoracic impedance (TTI) during defibrillation. The magnitude of this effect has not been established using external paddles. We compared TTI in 40 men before elective cardiac surgery, and before and after shaving their chests. Chest hair causes a significant increase in TTI during external defibrillation, the magnitude of the effect being related to both the quantity of hair and force applied to the defibrillation paddles. When the chests of nonhirsute patients were shaved, a decrease in TTI occurred, which was probably related to the creation of low-impedance pathways through skin abrasions.

Adult↗
PubMed2004

Is optimal paddle force applied during paediatric external defibrillation?

INTRODUCTION: Optimal paddle force minimises transthoracic impedance; a factor associated with increased defibrillation success. Optimal force for the defibrillation of children < or =10 kg using paediatric paddles has previously been shown to be 2.9 kgf, and for children >10 kg using adult paddles is 5.1 kgf. We compared defibrillation paddle force applied during simulated paediatric defibrillation with these optimal values. METHODS: 72 medical and nursing staff who would be expected to perform paediatric defibrillation were recruited from a University teaching hospital. Participants, blinded to the nature of the study, were asked to simulate defibrillation of an infant manikin (9 months of age) and a child manikin (6 years of age) using paediatric or adult paddles, respectively, according to guidelines. Paddle force (kgf) was measured at the time of simulated shock and compared with known optimal values. RESULTS: Median paddle force applied to the infant manikin was 2.8 kgf (max 9.6, min 0.6), with only 47% operators attaining optimal force. Median paddle force applied to the child manikin was 3.8 kgf (max 10.2, min 1.0), with only 24% of operators attaining optimal force. CONCLUSION: Defibrillation paddle force applied during paediatric defibrillation often falls below optimal values.

Body Weight↗
PubMed2004

Differential contribution of skin impedance and thoracic volume to transthoracic impedance during external defibrillation.

BACKGROUND: Two mechanisms by which firm external paddle force decreases transthoracic impedance (TTI) have been proposed. Decreased impedance at the paddle-skin interface has been assumed to be the primary mechanism, but expulsion of air from the lungs, reducing lung volume is also likely to contribute. The relative contribution of each mechanism is unknown. METHODS AND RESULTS: Thirty five intubated patients undergoing general anaesthesia for cardiac surgery were studied. TTI across external defibrillation paddles was measured as paddle force was increased to 12kgf. Measurements were performed twice; once allowing the volume of the lungs to change and once with lung volume held at functional residual capacity. TTI with constant lung volume was significantly higher at (P< 0.001), confirming that a reduction in lung volume contributes to the decrease in TTI. At an optimal paddle force of 8kg, the reduction in lung volume contributed to 16.2% of the overall decrease in TTI. CONCLUSION: The decrease in TTI seen with increasing external paddle force is due primarily to improved electrical contact at the paddle-skin interface, with a decrease in thoracic volume accounting for no more than 16% of the overall decrease at forces used clinically.

Cardiac Surgical Procedures↗
PubMed2004

External defibrillation in the left lateral position--a comparison of manual paddles with self-adhesive pads.

INTRODUCTION: Firm paddle force during defibrillation lowers transthoracic impedance (TTI) and increases transmyocardial current, increasing the chances of successful cardioversion. Current protocols recommend that if defibrillation using the anterior-apical (AA) paddle position fails, the anterior-posterior (AP) position should be used. This generally requires the patient to be placed in the left lateral position with the operator leaning over the patient. Avoiding physical contact with the patient during defibrillation subjectively makes application of firm paddle force difficult in the AP position. We compared TTI between the AA and AP positions and between manual paddles and self-adhesive pads to establish if the AP position precludes firm paddle force and to compare TTI between paddles and self-adhesive pads. METHODS: Twenty-one consecutive patients undergoing elective cardioversion (age 39-82) were studied. TTI was measured between pairs of manually held paddles and self-adhesive pads using AA placement with the patient supine, and AP placement with the patient left lateral position. RESULTS: Mean TTI using the AP electrode position was lower using manual paddles (66.5 Omega; 95% CI 60.2-72.9 Omega) than that using self-adhesive pads (92.1 Omega; 95% CI 81.5-102.7 Omega; 95% CI between the mean =15.8-35.5 Omega; P <0.0001). TTI was significantly less using the manual paddles compared with self-adhesive pads in both AA and AP positions (P <0.0001). CONCLUSION: Despite the subjective difficulties of defibrillating patients in the AP position whilst leaning over them, use of manual paddles achieves a lower TTI than that achieved with self-adhesive pads.

Adult↗
PubMed2003

Is the orientation of the apical defibrillation paddle of importance during manual external defibrillation?

OBJECTIVE: Transthoracic impedance (TTI) is a factor determining the magnitude of the transmyocardial current during external defibrillation. Minimising TTI increases the chances of successful defibrillation. Most external defibrillation paddles are rectangular in shape and can, therefore, be placed in a transverse or longitudinal orientation. The apical paddle is often placed in a transverse orientation. This may theoretically result in a higher TTI than a longitudinal orientation because of poorer contact at the lateral paddle edges. We compared TTI with the apical paddle in both a transverse and longitudinal orientation. MATERIALS AND METHODS: Twenty sequential anaesthetised patients were studied. A pair of defibrillator paddles were instrumented to measure paddle force. TTI was recorded pre-operatively at end-expiration with the apical paddle in both longitudinal and transverse orientations. The sternal paddle was placed in a longitudinal orientation for all measurements. RESULTS: TTI decreased in both transverse and longitudinal orientations as paddle force increased. Transverse paddle orientation resulted in a significantly (P<0.01) higher TTI than longitudinal orientation at all paddle forces below 12 kg force. CONCLUSION: The longitudinal orientation of a rectangular defibrillation paddle provides a lower TTI than orientation horizontally.

Electric Countershock↗
PubMed2003

What is the optimal paddle force during paediatric external defibrillation?

INTRODUCTION: Transthoracic impedance (TTI) is a major determinant of transmyocardial current flow, and therefore, the success of defibrillation. European Resuscitation Council (ERC) paediatric guidelines recommend that 'firm' paddle force should be applied to the paddles during defibrillation. No study has yet established the optimal paddle force required to minimise TTI in children of different ages. METHODS: Eighty patients aged 10 weeks to 17 yrs undergoing general anaesthesia for routine surgery were studied. Using defibrillation paddles placed in an anterior-apical position, TTI (Omega) was measured for increasing values of force from 0.5 kgf (baseline) to 6.5 kgf. The optimal force, the force to achieve 95% of the overall reduction in TTI, was then determined. According to current guidelines, paediatric paddles (surface area 16 cm2) were used for infants (< or =10 kg) and adult paddles (82 cm2) for older children. Optimal force was then calculated for infants < or =10 kg, children >10 kg and < or =8 yrs and children 9-17 yrs age. RESULTS: Increasing paddle force from 0.5 kgf progressively decreased TTI. Optimal force using paediatric paddles was 2.9 kgf in infants. Optimal force using adult paddles was 5.1 kgf in children >10 kg but < or = 8 yrs and 5.3 kgf in children aged 9-17 yrs. CONCLUSIONS: Force is an important determinant of TTI and therefore, outcome of defibrillation. It is recommended that a minimum of 3 kgf be applied to paddles when defibrillating infants with paediatric paddles, and a minimum of 5 kgf be applied to all older children when adult paddles are used.

Adolescent↗