Jack L. Clausen

Altered Distribution of Pulmonary Ventilation and Blood Flow Following Induction of Inhalational Anesthesia

The development of impairment of pulmonary gas exchange during inhalational anesthesia was studied in ten patients (ages 52–75 years) by use of the multiple-inert-gas elimination method. Preoperative pulmonary function tests indicated a wide range of abnormal pulmonary function. Control gas-exchange studies with the subjects awake (supine position) demonstrated modest increases in pulmonary ventilation-blood flow (VA/Q) distribution in all subjects (mean log SD = 0.96), but the shunt was minimal (mean 1.3 per cent). Inhalational anesthesia was either 1) halo-thane, 0.4 per cent (end-tidal) in N2O, 50–60 per cent, balance oxygen, for eight subjects, or 2) halothane, 0.6 per cent, in nitrogen, 50–60 per cent, balance oxygen, for two subjects. Striking increases in retention of the least soluble tracer gases (SF6, and ethane) were seen in all patients after a minimum of 35 min of anesthesia, during mechanical ventilation with both anesthetic regimens. This was due to one of three different patterns of responses. Three subjects showed primarily increased intrapulmonary shunt (mean shunt = 23 per cent of cardiac output). Three subjects showed primarily increases in low-VA/Q units (mean = 32 per cent of cardiac output), with little or no shunt, while the remaining four had both intrapulmonary shunt and units of low VA/Q. Arterial blood PO2 measurements suggested substantially greater impairment of oxygenation when the pattern of response was primarily an increase in shunt. This difference was accentuated by the concentrating effect of N2O uptake on alveolar PO2 in low-VA/Q units. As a consequence, arterial blood PO2 values grossly underestimated the VA/Q inequality in patients in whom low-VA/Q regions developed. An alternative index, the development of CO2 retention at constant alveolar ventilation, more reliably identified patients in whom severe VA/Q inequality developed during inhalational anesthesia.

Sleep apnoea and sympathetic nervous system activity: a review

A review was made of the literature relating sleep apnoea to sympathetic nervous system (SNS) activity, as inferred from catecholamine levels or muscle sympathetic nerve activity (MSNA). Twenty‐four studies were located. Most studies reported an elevation of norepinephrine and MSNA, both during sleep and wakefulness among individuals with sleep apnoea. However, studies rarely controlled for known confounders of sympathetic activity, making the validity of the findings questionable.

Weight force during prone restraint and respiratory function

Prone maximal restraint position (PMRP, also known as hogtie or hobble) is often used by law enforcement and prehospital personnel on violent combative individuals in the field setting. Weight force is often applied to the restrained individuals back and torso during the restraint process. We sought to determine the effect of 25 and 50 lbs weight force on respiratory function in human subject volunteers placed in the PMRP. We performed a randomized, cross-over, controlled trial on 10 subjects placed in 4 positions for 5 minutes each: sitting, PRMP, PRMP with 25 lbs weight force (PMRP+25), and PRMP with 50 lbs weight force placed on the back (PMRP+50). We measure pulse oximetry, end-tidal CO2 levels, and forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1). FVC and FEV1 were significantly lower in all restraint positions compared with sitting but not significantly different between restraint positions with and without weight force. Moreover, mean oxygen saturation levels were above 95% and mean end-tidal CO2 levels were below 45 mm Hg for all positions. We conclude that PMRP with and without 25 and 50 lbs of weight force resulted in a restrictive pulmonary function pattern but no evidence of hypoxia or hypoventilation.

Pulmonary Function Tests in the Detection of Left Heart Failure: Correlation with Pulmonary Artery Wedge Pressure

Standard pulmonary function tests, including lung volumes measured by three fundamentally different techniques, were performed in 40 patients undergoing cardiac catheterization. These were compared with clinical and radiologic evaluations in detecting left heart failure (LHF). Patients with elevation in mean pulmonary artery wedge pressure (PAWM) greater than or equal to 20 mm Hg had significant restrictive changes with reduction in vital capacity (VC), forced expiratory volume in 1 s (FEV1.0), and total lung capacity (TLC) measured by helium dilution and body plethysmography. Radiographic TLC was not reduced in these patients or correlated with PAWM. Obstructive changes were not present. Radiologic gradings by 5 different observers were reasonably accurate in detecting LHF but varied between observers. VC and TLC measured by helium dilution and body plethysmography were slightly less sensitive but more specific in detecting PAWM elevation. Clinical classification was sensitive but nonspecific; in addition, clinical signs were not reliable indicators of elevated PAWM. We conclude that pulmonary function testing may provide objective, accurate, and useful information in the evaluation of cardiac patients for LHF. However, radiographic measurement of thoracic cage volume does not reflect the changes in lung gas volume measured by gas dilution or plethysmographic techniques in patients with chronic congestive heart failure.

The Effect of Oleoresin Capsicum “Pepper” Spray Inhalation on Respiratory function

We performed a randomized, cross-over controlled trial to assess the effect of Oleoresin capsicum (OC) spray inhalation on respiratory function by itself and combined with restraint. Thirty-five subjects were exposed to OC or placebo spray, followed by 10 min of sitting or prone maximal restraint position (PMRP). Spirometry, oximetry, and end-tidal CO2 levels were collected at baseline and throughout the 10 min. Data were compared between groups (ANOVA) and with predefined normal values. In the sitting position, OC did not result in any significant changes in mean percent predicted forced vital capacity (%predFVC), percent predicted forced expiratory volume in 1 s (%predFEV1), oxygen, or CO2 levels. In PMRP, mean %predFVC and %predFEV1 fell 14.4 and 16.5% for placebo and 16.2 and 19.1% for OC, but were not significantly different by exposure. There was no evidence of hypoxemia or hypercapnia in either groups. OC exposure did not result in abnormal spirometry, hypoxemia, or hypoventilation when compared to placebo in either sitting or PMRP.

Extending Resectability for Carcinoma of the Lung in Patients with Impaired Pulmonary Function

Abstract A total of 49 consecutive patients who had resection for carcinoma of the lung is reported. Twenty-two of the patients had marginal pulmonary function, forced expiratory flow rate less than 1.0 liter per second, and forced vital capacity in the first second less than 70%. Of the total group, 23 were more than 60 years old, and 13 of these had marginal pulmonary function. Thirteen patients had pneumonectomy, with no hospital mortality; 30 had lobectomy, with 3 hospital mortalities; and 6 had wedge resection, with 1 hospital mortality. No patients had pulmonary insufficiency in the postoperative period or died of pulmonary insufficiency. The selection of patients was based on a combination of data on flow rates, vital capacity, and regional ventilation perfusion scans. The good results may be due to the fact that despite major obstructive disease of the airway, vital capacity was preserved (92 ± 16% of predicted). Intraoperative use of the Robertshaw tube, preservation of as much lung as possible, and use of local analgesia during the postoperative period were apparent contributors to the low mortality and the absence of pulmonary insufficiency.

Evaluation of sleep disordered breathing with unattended recording: the Nightwatch System

There is a need for studies to determine how new ambulatory systems compare to traditional polysomnography (PSG). Thirty-four subjects were recorded with the Nightwatch (NW) System (Heathdyne Inc.) at home and then recorded with PSG in the laboratory. NW records were scored automatically using the NW algorithm with manual editing. There were no significant differences in mean RDI, AI, number of apneas or hypopneas or oximetry varibles between the systems. Correlations of RDI on the Nightwatch system and laboratory nights were significant (r = 0.63). Every case of RDI > or = 10 on the PSG was also identified by Nightwatch. Specificity was lower on Nightwatch (66%); however, all three cases of false positives could be explained physiologically, i.e. by body position. Overall the NW system correlated well with traditional PSG for respiratory disturbance.

The immediate effects of cortisol on pulmonary function in normals and asthmatics

We investigated short-term effects of corticosteroids on airway caliber, measured by spirometry and body plethysmography, over a period of 6 hr after an intravenous bolus of cortisol (8 mg/kg) or saline placebo was administered in a double-blind crossover format comparing 10 normal and nine asymptomatic unmedicated asthmatics. After 6 hrs isoproterenol (240 micrograms) was administered to compare the effects of cortisol with a beta-agonist bronchodilator. Serum cortisol levels remained greater than 100 micrograms/dl after cortisol and normal after placebo. Cortisol had no effect on pulmonary function except for a trend of improved flows and decreasing ratios of residual volume to total lung capacity in asthmatics that was not significant at 6 hr. Isoproterenol resulted in immediate improvement in specific conductance and flows in both groups; no interaction with cortisol was seen. We conclude that cortisol had no short-term effect on airway caliber in normals, at best a slowly evolving effect in asymptomatic unmedicated asthmatics, and no interaction with the bronchodilator effects of a maximal dose of isoproterenol in these groups.