One possible explanation for the higher peak flow values observed in our patient population is the altitude where testing was performed (approximately 1,606 m). Recently, Lenggenhager reported that resistance to airflow was reduced as barometric pressure decreased. Our results with normal subjects in an atmospheric chamber support this finding clinically. Subjects were able to generate sequentially higher percent predicted peak flows as the altitude was increased. On the other hand, the percent predicted FEV, that could be generated did not increase significantly at the simulated altitudes tested. It has been shown that at very high altitudes the FEV, does increase proportionately with increasing altitude.
These findings support the premise that FEVi is reproducible at most locations where routine clinical testing is performed. …Read the rest of this article
For example, of 18 patients with JPF values in the range of 80 to 89 percent predicted, 11 had FEV, values of less than 70 percent predicted. The same results were observed when peak flow obtained with the WPF was used for comparison. fully
We further sought to assess the effect of altitude on values of FEV! and PEFR. The results obtained in an atmospheric chamber are summarized in Figure 4. Compared with values obtained at sea level, the mean percent predicted peak flow value for the nine normal subjects increased by 6.3 percent (range, 2 to 16 percent) at 1,515 m and 12.0 percent (range, 1 to 20 percent) at 2,272 m. No significant change in FVC or FEV! was seen at any of the altitudes tested when compared with values obtained at sea level. The increase in PEFR at 1,515 and 2,272 m was statistically significant (p<0.001, ANOVA). The peak flow values at 757.5 m also tended to be higher than FEVi and FVC, but the differences did not achieve statistical significance. …Read the rest of this article
Ten subjects with airway obstruction demonstrated little or no reversible component and had diagnoses of COPD. The mean baseline FEVi for all patients with obstructive lung disease was 1.83 ±0.75 L (60.9 percent predicted) while the mean JPF was 314 ± 122 L/min (76.9 percent predicted). Airway symptoms had been present in this group from six months to 55 years, with a mean duration of 12.8 years. Seventy-two (71 percent) patients reported previous experience using either the JPF or the WPF. Thirty patients had no prior experience with either instrument. Here …Read the rest of this article
All testing was performed at an altitude of approximately 1,606 m. Each patient performed three maneuvers with each instrument in an alternating fashion. The FEV, and PEFR obtained with the JPF as well a PEFR obtained with the WPF were converted to percent predicted, using normal standards for ventilatory function. In addition, absolute values of FEV„ JPF, and WPF were compared. Studies with 60 normal subjects in our laboratory demonstrated that the predicted values of Knudson et al correlated best with the equipment used. Therefore, all data reported are based on those authors’ predicted values. …Read the rest of this article
Effect of Modest Altitude Spirometric testing is often used in the assessment of the patient with pulmonary disease. In patients with asthma and other obstructive lung diseases, FEVj and PEFR are widely used to estimate the degree of pulmonary impairment. Both measurements have proved to be excellent methods of following the course of individual patients, but few data are available comparing their relative merits for initial patient evaluation. …Read the rest of this article