Stephen Birch

Breathing Patterns: 1. Normal Subjects

Ventilatory monitoring devices that require mouthpiece breathing produce a rise in tidal volume (VT), a fall in frequency (f) and alterations in periodicity and variability of breathing components. Together with the introduction of the respiratory inductive plethysmograph, a reliable noninvasive monitoring device of ventilation, major advances have taken place in understanding the significance of the components of the breathing pattern. We measured the breathing pattern of normal subjects utilizing respiratory inductive plethysmography and continuously processed these data with a microprocessor system. The mean values of the breathing pattern components in normal subjects were not affected by age, but the rhythmicity was more irregular in the elderly. The values of breathing pattern components obtained noninvasively by respiratory inductive plethysmography in normal subjects are fairly predictable in limits similar to other tests of pulmonary function.

Effect of positive end-expiratory pressure on breathing patterns of normal subjects and intubated patients with respiratory failure

The aims of this study included assessment of accuracy of respiratory inductive plethysmography when pulmonary hyperinflation was induced by application of PEEP, and examination of breathing patterns of normal subjects, intubated patients requiring mechanical ventilation and intubated patients immediately before extubation during application of PEEP by demand valve and high gas flow reservoir bag systems. Validation of tidal volume (VT) and end-expiratory level measured with respiratory inductive plethysmography to simultaneous spirometry (SP) was achieved with PEEP levels up to 12.5 cm H2O in 7 normals. In 17 intubated patients, almost all VT values measured with respiratory inductive plethysmography fell within +/- 10% of SP even with 2 to 3 changes of body posture. In normal subjects, increasing levels of PEEP from the demand valve system produced nonprogressive rises of VT and mean inspiratory flow, falls of frequency and fractional inspiratory time (TI/TTOT), and no changes of minute ventilation (Vmin) nor mean expiratory flow. PEEP from the high gas flow reservoir bag system produced nonprogressive rises of VT and rib cage (RC) contribution to VT, and rises of Vmin and mean inspiratory and expiratory flows between 10.0 and 12.5 cm H2O of PEEP. Intubated patients requiring intermittent mandatory ventilation (IMV) had a rapid, shallow breathing pattern unaltered by PEEP levels delivered by either system up to 12.5 cm H2O despite increases of end-expiratory level. Intubated patients who were about to be extubated breathed with patterns closer to ambulatory normal subjects with the exception of their elevated RC contribution to VT.(ABSTRACT TRUNCATED AT 250 WORDS)

Deposition of ragweed pollen and extract on nasal mucosa of patients with allergic rhinitis: Effect on nasal airflow resistance and nasal mucus velocity

This study was undertaken to ascertain whether nasal mucus velocity (NMV) could be altered by short-term exposure to antigen. Asymptomatic patients with a history of allergic rhinitis who had a positive cutaneous reaction to ragweed extract were investigated. The plan was to achieve approximately a fourfold elevation of nasal airflow resistance (NAR) with antigen challenge and then obtain serial measurements of NAR and NMV. NMV was not significantly altered when the antigen was introduced by nasal inhalation of (1) ragweed pollen grains, (2) nebulized ragweed extract for 10 breaths, and (3) nebulized ragweed extract for 30 min on each of 3 successive days. When ragweed extract was introduced by direct instillation of the solution into the nose, NMV fell below baseline values at either 0.5 or 1.5 hr, or at both times after administration. Persistence of impairment of mucociliary transport at a time when nasal airway constrictor response had dissipated suggested that a chemical mediator might have been responsible for the alteration of clearance. The failure to demonstrate depression of mucus transport with the inhalation studies might have been due to insensitivity of the radiopaque Teflon disk method or to a qualitatively different allergic reaction to direct instillation of antigen solution.

Acute effects of aerosolized metaproterenol on breathing pattern of patients with symptomatic bronchial asthma

We studied the effect of two sequential puffs of metaproterenol (650 micrograms each puff) delivered with an auxiliary aerosol delivery system on the breathing pattern of patients with symptomatic bronchial asthma who were monitored noninvasively with respiratory inductive plethysmography. Particular attention was directed to respiratory center drive as reflected by mean inspiratory flow and minute ventilation. Both these components were elevated in the eight patients whose mean FEV1.0 was 1.43 L (45% predicted normal). Two puffs of metaproterenol produced a maximal increase over baseline in FEV1.0 of 50 +/- 25% (SD), whereas no change took place in FEV1.0 with placebo administration. This dose of metaproterenol did not alter heart rate nor blood pressure throughout the study period of 2 hours. Neither mean inspiratory flow, minute ventilation, nor any component of the breathing pattern changed with this partial reversal of bronchoconstriction. These results suggest that the neural mechanism accounting for heightened respiratory center drive in patients with symptomatic bronchial asthma does not wholly depend on bronchoconstriction.