Albert E. Heurich

Cardiopulmonary responses to continuous positive airway pressure in acute asthma

The effects of nasal continuous positive airway pressure (CPAP) on expiratory flow, arterial blood gas tensions, cardiovascular status, and dyspnea were studied in 21 patients with acute asthma. Therapy consisted of the following CPAP sequence: 30 minutes at 5 cm H2O, 20 minutes at 0 cm H2O, 30 minutes at 7.5 cm H2O, and 20 minutes at 0 cm H2O. Six control patients were fitted with a CPAP mask but given no positive-pressure therapy. Significant reductions in respiratory rate occurred from a baseline of 22.0 +/- 1.0 to 19.8 +/- 3.8 breaths/min at CPAP 5 cm H2O and to 19.4 +/- 4.3 breaths/min at CPAP 7.5 cm H2O (P < .05). No significant change occurred in forced expiratory volume in 1 second (FEV1), heart rate, mean arterial blood pressure, or arterial blood gas tension with either level of CPAP. Dyspnea, as assessed by a breathlessness score, improved during CPAP therapy (P < .05). These levels of CPAP were tolerated without deleterious side effects. In comparison, the control group showed no change in heart rate, respiratory rate, or breathlessness score during the study period. These data show that application of CPAP in acute asthma reduces respiratory rate and dyspnea with no untoward effects on gas exchange, expiratory airflow, or hemodynamics.

Damped Oscillatory Respiratory Response after Marathon Running at Altitude

Abstract Serial determinations of oxygen and carbondioxide concentrations and volumes of expired gas were made in 5 partially acclimatized, endurance trained, sea level residents following participation in the 1972 Pike’s Peak Marathon. The race combined a 26.3 mile distance run with an 8200 foot ascent and descent. Inspired oxygen tension ranged between 93 and 116 mm Hg. The time courses of V ˙ E , V ˙ O 2 and V ˙ C O 2 were compared with the pre-marathon values. Following the initial rapid decrease in V ˙ O 2 , a sustained elevation was noted for up to 90 minutes of resting recovery. Superimposed on this curve were responses having characteristics of damped oscillations. Similar periodic fluctuations were noted for V ˙ CO 2 and V ˙ E . These findings are discussed. The most probable cause is due to sustained involuntary muscular contractions with further muscle contraction and/or movement producing additional variations in metabolic rate during this “unnatural” form of recovery required for this study.