Results obtained in individual subjects are shown in Table 2. Mean data and statistical comparisons between groups of paired data are provided in Table 3.
Symptoms and Signs
Marked eye irritation was a universal finding. Most individuals opted to wear the protective goggles after spending several minutes in the chamber. Three subjects experienced mild, transient, self-limiting cough. Except for eye and nasopharyngeal irritation, the subjects were comfortable and spent the time in the chamber reading or studying. No subject complained of headache, chest pain, or abdominal pain. No subject had wheezes detectable by auscultation either immediately before or after the period of involuntary smoking.
Blood Carboxyhemoglobin Analysis
The pre-exposure venous blood carboxyhemoglobin (COHb) level was 1.71 ±0.89 percent (mean±SD). Following passive smoking, the COHb level was 2.57 ±1.05 (p<0.001). This represents an increase in the mean COHb level of 0.86. This is in close agreement with the expected increase in COHb content following exposure to 40 to 50 ppm carbon monoxide for 60 minutes.
Effects of passive smoking on children and adults:
Results of baseline lung function on day 1 were normal in four subjects, showed small airways obstruction in another four subjects, and revealed mild airways obstruction (FEV1 between 65 percent and 80 percent of predicted) in one subject. There was no difference between day 1 baseline lung function and day 2 pre-smoke lung function. Comparison of day 2 presmoke lung function and postsmoke lung function showed no difference in FEV! or Vmax50. The FVC showed a small decrease (2 percent) following passive smoking (p = 0.01).
The baseline PD2OFEV1 on day 1 showed that each subject had a high degree of nonspecific bronchial responsiveness compared to a normal population tested in our laboratory (Fig 1). This is to be expected but confirms that our subjects, who were asymptomatic at the time of testing, are asthmatics (Such an article “Diagnosis of Bronchial Asthma by Clinical Evaluation” may be useful to you).
A comparison of baseline PD^FEVi on day 1 with postexposure day 2 is provided in Figure 2. Eight of the nine subjects showed an increase in PD2FEX1. The mean PDaoFEVj before smoke was .25 ± .22 mg/ml and after exposure was. 79 ± 1.13 mg/ml (p = 0.04) while the log PDaoFEVj increased from —1.92 to —1.21 (p = 0.02).
Table 2—Individual Results of Lung Function and PD^FEVj in Asthmatic Subjects
|Subject||Test||Day 1||Day 2|
Table 3—Mean Results of Lung Function, Carboxyhemoglobin Levels, and PDJFEV1
|Day 1||Day 2|
|FEV, (L)||3.43± .57||3.48± .65||3.45± .63|
|Vmax50 (L/sec)||3.46± 1.14||3.46± 1.14||3.42 ±1.02|
|FVC (L)||4.57 ±0.55||4.65±0.58*||4.56±0.60* *p = 0.01|
|COHb (%)||1.71 ±0.89||2.57±1.05 p = 0.001|
|PD20FEVl (mg/ml)||0.25±0.22||0.79 ± 1.13 p = 0.043|
|log PD^FEV,||—1.92 ± 1.23||—1.21 ± 1.54 p = 0.022|
Figure 1. The methacholine responsiveness of the study population is compared with individuals who gave no history of asthma. The asthmatic subjects have a very low PD^FEY^ indicating a high degree of airway reactivity.
Figure 2. This illustrates the methacholine responsiveness in nine stable asthmatics before and after passive smoking. Exposure to cigarette smoke resulted in an increased PD^FEY^ indicating a decrease in airway reactivity (p = 0.022). The mean values are also illustrated (antilog of the mean of the log PDuFEVj values).