The clinical assessment of the chemical regulation of ventilation

Respiratory performance of humans exposed to moderate levels of carbon dioxide

In a business as usual scenario, atmospheric carbon dioxide concentration (CO₂ ) could reach 950 parts per million (ppm) by 2100. Indoor CO₂ concentrations will rise consequently, given its dependence on atmospheric CO₂ levels. If buildings are ventilated following current standards in 2100, indoor CO₂ concentration could be over 1300 ppm, depending on specific ventilation codes. Such exposure to CO₂ could have physiological and psychological effects on building occupants. We conducted a randomized, within-subject study, examining the physiological effects on the respiratory functions of 15 persons. We examined three exposures, each 150 min long, with CO₂ of: 900 ppm (reference), 1450 ppm (decreased ventilation), and 1450 ppm (reference condition with added pure CO₂ ). We measured respiratory parameters with capnometry and forced vital capacity (FVC) tests. End-tidal CO₂ and respiration rates did not significantly differ across the three exposures. Parameters measured using FVC decreased significantly from the start to the end of exposure only at the reduced ventilation condition (p < 0.04, large effect size). Hence, poor ventilation likely affects respiratory parameters. This effect is probably not caused by increased CO₂ alone and rather by other pollutants-predominantly human bioeffluents in this work-whose concentrations increased as a result.

Morbidity and mortality after thoracoscopic pneumonoplasty

BACKGROUND

Both video-assisted thoracic surgery and open pneumonoplasty procedures have been used to achieve lung reduction in emphysema patients.

METHODS

The surgical and hospital course of 339 patients with a mean forced expiratory volume in 1 second of 750 mL and a mean ratio of forced expiratory volume in 1 second to forced vital capacity of 35% undergoing video-assisted thoracic surgical laser pneumonoplasty was analyzed.

RESULTS

The incidence of myocardial infarctions was 0.9% and the hospital mortality rate was 4.1%.

CONCLUSIONS

Factors leading to increased morbidity and mortality were advanced age (65 years and greater, especially greater than 75 years), sex (men greater than women), carbon dioxide retention in the resting state (especially an arterial carbon dioxide tension greater than 55 mm Hg), forced expiratory volume in 1 second less than 700 mL for men and 500 mL for women, maximum voluntary ventilation less than 25% predicted, and a ratio of residual volume/total lung capacity greater than 60%.

Effect of endotracheal continuous positive airway pressure on sensitivity to carbon dioxide and on respiratory timing in preterm infants

To determine the effects of continuous positive airway pressure (CPAP) on ventilatory response to CO2 and inspiratory and expiratory duration in preterm infants, 24 preterm infants with an average birth weight of 1220 g were studied at a mean age of 10.6 days. CPAP was applied via an uncuffed endotracheal tube. Testings were performed between ambient pressure and a positive airway pressure of 10 cm H2O. Approximately 2/3 of the applied pressure was transmitted to the esophagus. All infants demonstrated a ventilatory response to carbon dioxide of less than 50 ml/min per mm Hg Pco2 at ambient pressure, and no infant showed significant improvement at increasing levels of CPAP. Drive to breathe, as reflected in the inspiratory flow rate (Vt/Ti) also failed to change significantly. It may be concluded that in the apparent absence of significant changes in lung volume, CPAP fails to increase sensitivity to CO2 in preterm infants recovering from hyaline membrane disease.

Carbonic anhydrase inhibition in glaucoma: hazard or benefit for the chronic lunger?

Carbonic anhydrase inhibitors, of proven value in the longterm management of glaucoma, have a number of troublesome side effects, most of which are well-known. However, their potential hazards to patients with chronic obstructive lung disease have received little attention. The author reviews the physiological effects of carbonic anhydrase inhibition on carbon dioxide metabolism and the implications for the chronic lung patient. The untoward pulmonary complications associated with the use of carbonic anhydrase inhibitors are of particular importance to ophthalmologists, since chronic lung disease and glaucoma, both common disorders in the elderly, frequently coexist in the same patient.