PubMed Health⌕ Search

Biomedical subjects

H Watson

Publications and source records attributed to H Watson.

At least 73 records · Page 4Linked to original sources
PubMed1983

Validation of respiratory inductive plethysmography in patients with pulmonary disease.

The assumption that the respiratory system behaves with 2 df of motion in healthy persons allows calibration of respiratory inductive plethysmography (RIP) with spirometry (SP). To ascertain whether RIP could be calibrated by the same assumption in patients with lung disease, even though at least 3 df of motion are visualized (ie, upper and lower rib cage and upper and lower abdomen move out of phase), RIP was calibrated by a two-position calibration procedure and validated satisfactorily by simultaneous SP in the erect, semirecumbent, supine, and lateral decubitus positions. In lung disease, the contribution to tidal volume of regions moving independently of the combined rib cage and abdominal movements either is small or remains relatively constant with change of body posture. For clinical monitoring of the resting breathing pattern where patient movements cannot be restricted, respiratory inductive plethysmography can serve as a reliable semiquantitative, noninvasive ventilatory monitoring device.

Abdomen↗
PubMed1983

Towards an efficient retractor handle: an ergonomic study.

In a study whose aim was to design an ergonomically efficient retractor handle, surgeons' views on retractor design were canvassed by questionnaire. After observing retractors in use and measuring the forces involved peroperatively, prototype handles were made and tested in a laboratory. Experimental subjects showed a marked preference for a vertical 'T' configuration. Such a handle could easily be incorporated into most existing retractor designs.

Equipment Design↗
PubMed1982

Validation of respiratory inductive plethysmography using different calibration procedures.

We devised a new calibration procedure [least squares method (LSQ)] for respiratory inductive plethysmography (RIP) and compared it with our previously reported simultaneous equation method (SEQ) of analyzing data in 2 body positions and with the method of Stagg and associates using the analysis of individual breaths in a single body position. The values from RIP were compared with simultaneous spirometry (SP) in 20 normal subjects placed in the standing (STD), supine (SUP), sitting, prone, semi-recumbent, right lateral decubitus, and left lateral decubitus postures. The LSQ gave the most accurate results followed closely by SEQ. In addition, LSQ was compared with the isovolume angle maneuver (ISV) calibration procedure in supine (ISV-SUP) and standing (ISV-STD) postures. Each of the 10 normal subjects breathed at tidal volumes of 250, 750, and 1,250 ml in the SUP and STD postures. Of the values obtained by the LSQ method, 93% were within +/- 10% of SP in SUP and STD positions. Without a change in the posture in which the calibration was made, 83% of values with ISV-SUP and 90% of values with ISV-STD were within +/- 10% of SP. When body position was changed, 65% of the values obtained with ISV-SUP and 38% of the values obtained with ISV-STD were within +/- 10% of SP. With the LSQ, 45% of isovolume angles in SUP and STD position were within 45 +/- 3 degrees; 40% of isovolume angles with ISV-SUP and 60% with ISV-STD were within 45 +/- 3 degrees when body position was changed from position calibrated. In estimating fractional contribution of rib cage and abdominal compartments. LSQ was comparable to ISV in the standing posture but generally gave lesser values for the rib cage contribution in the supine posture than ISV. The optimal calibration procedure for respiratory inductive plethysmography in terms of accuracy and ease of subject performance is the least squares calibration procedure.

Calibration↗
PubMed1982

Response to bronchodilator drug administration by a new reservoir aerosol delivery system and a review of other auxiliary delivery systems.

Response to bronchodilator aerosols delivered by metered dose inhalers (MDI) depends in part upon the amount of drug depositing on the airways. Ideally, the MDI should be actuated during a slow deep inhalation followed by a breathholding pause, an impossible maneuver for many patients. We developed a new reservoir aerosol delivery system (RADS) consisting of a 700-ml collapsible bag in which aerosol could be injected. The mouthpiece-canister was filtered with a reed that vibrated at inspiratory flows greater than 0.3 L/s to produce a noise. Patients were instructed to keep inhalation silent while breathing from RADS. One puff of metaproterenol (650 microgram) administered via RADS (with one breath rebreathed) was compared with one puff of metaproterenol (650 micrograms) from usual MDI using serial measurements of body plethysmography and spirometry. Respiratory inductive plethysmography measured the point of MDI actuation, volume of inhalation, inspiratory flow, and breathholding pause. Ten patients with chronic airflow limitation caused by asthma or chronic bronchitis were given typed instructions on MDI usage and trained shortly before the study. Metaproterenol via RADS produced significantly greater maximal increase in SGaw (195 +/- 52% SE) compared with metaproterenol via conventional MDI (101 +/- 24%, p less than 0.003). Bronchodilator response in 4 patients unable to coordinate actuation of the MDI with inspiration was significantly less than in 6 patients with good MDI technique (p less than 0.005). The mean flow rates were 0.54 +/- 0.16 L/s during inhalation of metaproterenol compared with 0.19 +/- 0.02 L/s and 0.24 +/- 0.03 L/s during the first and second inhalations, respectively, using RADS. This reservoir aerosol delivery system, which was well accepted by the patients, promotes more effective bronchodilation than the conventional metered dose inhaler.

Adult↗
PubMed1981

Noninvasive ventilatory monitoring by respiratory inductive plethysmography in conscious sheep.

The respiratory inductive plethysmograph is a noninvasive device that has been used to measure tidal volume (VT) in humans from changes in self-inductance of wire coils excited by an oscillator circuit placed about the rib cage and abdomen. We investigated its accuracy in conscious sheep utilizing a new calibration procedure during quiet breathing and breathing associated with bronchospasm provoked by aerosolized carbachol. Seven sheep were intubated with a nasotracheal tube and an esophageal balloon placed for determination of transpulmonary pressure. Base-line mean pulmonary flow resistance (RL) in the sheep was 1.5 +/- 0.7 (SD) cmH2O X l-1 X s. After carbachol inhalation, mean RL increased to a maximum of 8.8 +/- 2.8 cmH2O X l-1 X s (P less than 0.002). AT base line, mean VT estimated by respiratory inductive plethysmography over a 20-s period fell within +/- 6% of spirometry. After carbachol VT in five of the sheep remained close to the initial validation, but in two, it deviated +/- 11% from spirometry. Analysis of the continuous recording of timing and volume components of the breaths revealed that bronchoprovocation did not significantly alter mean VT or frequency. However, there was a slight increase in both parameters resulting in an increase in minute ventilation from 7.6 +/- 2.4 to 9.6 +/- 2.8 l/min (P less than 0.02). Similarly, a slight decline in inspiratory time coupled with the slight rise in VT produced an increase in mean respiratory flow from a base-line value of 0.35 +/- 0.12 to 0.44 +/- 0.17 l/s (P less than 0.05). These results indicate that the respiratory inductive plethysmography accurately monitors breathing pattern in conscious sheep even during severe bronchospasm.

Animals↗
PubMed1980

Necropsy: a yardstick for clinical diagnoses.

An attempt to obtain necropsies on all deaths from a selected group of clinical units resulted in a necropsy rate of 65% (compared with a normal of 30% in these units). The effect of increasing the necropsy rate was to produce a higher rate of confirmation of clinical diagnoses; nevertheless, 15% of main diagnoses and 42% of causes of death were not confirmed. A large proportion of these were deemed by clinicians in consultations with pathologists to be clinically significant. Of main diagnoses considered certain, 10% were not confirmed. The proportion of diagnostic discrepancies was virtually identical in two groups--those in which the clinicial believed he would normally have requested necropsy, and those in which he would not. Thus clinical confidence in the diagnosis is not an adequate assurance of its accuracy. Although in this survey necropsy was requested on almost all cases, permission was refused in many which may be attributed either to resistance by relatives or to an inadequate approach by the medical staff. The proportion of permissions secured by individual units varied from 50% to 92%. This indicates that the nature of the approach to relatives is the more important factor. As present practices do not adequately allow for the detection of a wide range of misdiagnoses and missed diagnoses it is proposed that a "partial audit" would provide a valuable yardstick; clinicians would be asked to obtain permission for necropsy on an agreed proportion (say, 20%) of deaths over and above those cases in which they are particularly interested and would normally request a necropsy.

Age Factors↗
PubMed1979

Distribution of ventilation in normal children.

Measurements of closing volume and the distribution fo ventilation by both single-breath (SBN2) and multiple-breath nitrogen washout methods were obtained in 376 healthy boys and girls, ages 6 to 18 years. A closing volume could be demonstrated in 39 percent of the subjects, and closing volume expressed as percentage of vital capacity did not change with height. Closing capacity expressed as percentage of total lung capacity showed a slight decrease with height. The slope of phase III of the SBN2 curve decreased with height. Single compartment N2 washout curves were observed in 72 percent of the subjects, and the incidence of single compartment curves increased with age. In those subjects with two compartment N2 washout curves, the relative compartmental ventilation became more even with increasing height. Our observations suggest that parallel units among peripheral airways grow at different rates.

Adolescent↗
PubMed1977

A new roentgenographic method for estimating mucous velocity in airways.

A new roentgenographic method is described for the estimation of mucous velocity in airways. Radiopaque discs of teflon mixed with bismuth trioxide were deposited in the trachea, and their motion was observed by a fluoroscopic image intensifier. Simultaneous measurements of disc movement were obtained by a previously reported cinebronchofiberscopic method and by the roentgenographic method in 6 anesthetized dogs. Mean +/- SD tracheal mucous velocity was 8.5 +/- 7.3 mm per min by the roentgenographic method, and 7.6 +/- 7.1 mm per min by the cinebronchofiberscopic method. Discrepancies between the 2 methods for individual disc velocities could be accounted for by the cumulative errors of both methods. The roentgenographic method was also used in 7 normal volunteers who did not have topical anesthesia of the tracheobronchial tree. The discs were blown through the inner channel of a bronchofiberscope, the tip of which was located just above the vocal cords. Placement of the discs on the tracheal mucosa generally did not produce coughing. Tracheal mucous velocity ranged from 7.4 to 19.4 mm per min as estimated from videotape recordings of the image intensifier images. There was no consistent difference in velocity between the erect or supine position, or after topical anesthesia with lidocaine.

Adult↗
PubMed1975

Activation of the hypertrophic right ventricle in the dog.

Right ventricular hypertrophy (RVH) of mild, moderate, or severe degree was produced in six dogs following systolic overload of the right ventricle by surgical banding of the pulmonary trunk. Activation of the myocardium and specialized conducting tissue of the right ventricle was studied using intramural multi-electrodes or an exploring electrode, first with the heart in situ and then with the heart in a modified Langendorff perfusion circuit. Normal epicardial and intramural activation patterns were found in RVH, and the prolonged excitation time was found to be due to the increased muscle mass. No delay in activation was found in any part of the specialized conducting tissue of the right ventricle. Late activated Purkinje fibres were found in the outflow tract of the right ventricle in the dogs with hypertrophy and in a control series of normal dogs. The present electrocardiographic criteria for complete and incomplete right bundle branch block (RBBB) are based on widening of the QRS complex and the rSR pattern. This type of change can occur also in RVH. Because it has been shown here that no delay occurs in the specialized conducting system of the right ventricle in RVH secondary to systolic loading; the application of criteria to electrocardiograms that also fulfil the criteria for RVH may be misleading. It is suggested that in such cases the diagnosis of a conduction disturbance must also depend upon other methods, and that the terms "incomplete' and "complete' RBBB should be handled with care in this context.

Animals↗
PubMed1975

Classification of ventricular pre-excitation. Vectorcardiographic study.

In a study of 45 cases of ventricular pre-excitation, 19 were classified as type A and 20 as type B according to Rosenbaum's criteria, which depend on the polarity of the major deflections in the right praecordial leads and not, as is commonly thought, on the direction of the delta vector. Six cases that could not be classified as type A or type B were termed intermediate. Vectorcardiograms were recorded from 29, and these showed a wide but continuous range of values for both the delta and the main QRS vectors in all three planes. Any classification based on these features must, therefore, depend on arbitrary quantitative data. Three patients in this series had associated right bundle-branch block. A review of the published reports on the association of pre-excitation and bundle-branch block failed to provide a rational basis for the classification of pre-excitation. It is emphasized that Rosenbaum's classification is empirical and its validity is questioned.

Adolescent↗