Diving: what to tell the patient with asthma and why?

Until a decade ago, divers with asthma were uniformly barred from diving with compressed air. This prohibition was based more on theoretical concerns for barotrauma than on actual data. Follow-up studies, although retrospective, do not support a ban on recreational or commercial diving for divers with stable asthma. These studies have noted that, despite the prohibition on diving, many divers with asthma have logged multiple dives without negative consequences. When those who have suffered diving-related barotrauma have undergone physiologic testing, measurements of small airways dysfunction (maximal mid-expiratory flow rates) have been lower than measurements for comparable divers who have never suffered diving accidents. Follow-up studies with long-term commercial divers have shown that a small percentage of individuals who have sufferred diving-related barotrauma also develop abnormal maximal mid-expiratory flow rates and even some airway hyperreactivity. These latter findings correlate with the changes that occur in chronic asthmatic patients, especially those who are not well treated. The decision as to whether an asthmatic patient should be allowed to dive rests on the individual's physiologic function, maturity, and insight into the consequences of poorly managed airway inflammation and bronchospasm.

Altitude-related pulmonary disorders.

The major physiologic stress encountered at high altitude is caused by the occurrence of hypobaric hypoxia. In this article, acute and chronic pulmonocardiac adaptation to altitude is reviewed, including possible genetic differences among highlanders from the Himalayan versus the Andean Mountains. The origin, symptoms, and treatment of acute mountain sickness and high altitude pulmonary edema are outlined. In addition, the prediction and prevention of pulmonary complications that may be encountered or exacerbated during commercial airflight are noticed.

CD4 lymphocyte counts and mortality in AIDS patients requiring mechanical ventilator support due to Pneumocystis carinii pneumonia.

OBJECTIVE: To evaluate CD4 counts as a predictor of mortality in AIDS patients with respiratory failure due to Pneumocystis carinii pneumonia (PCP). DESIGN: Retrospective chart review. SETTING: Urban university medical center. PATIENTS: Forty-eight patients admitted to the medical ICU from January 1993 to August 1996 with diagnosis of HIV/AIDS, PCP, CD4 count <200 cells per cubic millimeter, who required mechanical ventilation for respiratory failure. INTERVENTIONS: Medical records were reviewed and age, CD4 count, lactate dehydrogenase, room air (RA) PaO2, coinfections, and day of admission to day of intubation (DOA-DOI) data were recorded. RESULTS: All 48 patients (12 women and 36 men) were treated with corticosteroids and IV trimethoprim-sulfamethoxazole. Age ranged from 21 to 65 years; CD4, 1 to 180, RA PaO2, 27 to 93 mm Hg; and DOA-DOI, 0 to 20 days. Mortality varied significantly depending on CD4 counts: CD4 0 to 10 (100%); CD4 11 to 50 (88%); CD4 51 to 100 (50%); and CD4 >100 (25%). There were no significant difference in mortality between the groups with DOA-DOI <5 days (82%) vs >5 days (80%) or between the groups with PaO2 <60 mm Hg (85%) vs PaO2 >60 mm Hg (73%). CONCLUSION: Even though overall mortality was 81%, the mortality rate was significantly different among the four groups. Most striking was the progressive increase in mortality as CD4 cells decreased from >100 (25% mortality) to <10 (100% mortality). Survivors had significantly higher CD4 cell counts than those who died. The CD4 cell count within 2 weeks of admission has significant prognostic value and may be helpful when counseling patients, families, and healthcare surrogates in end-of-life decision making.

Serial measurements of the rapid-shallow-breathing index as a predictor of weaning outcome in elderly medical patients.

STUDY OBJECTIVES: To determine the usefulness of serial measurements of the rapid-shallow-breathing index (f/VT) as a predictor for successfully weaning elderly medical patients from mechanical ventilator support using a threshold value (< or =130) derived specifically for this population. DESIGN: Prospective observational study using parameters suggested from retrospective analysis. SETTING: Medical ICUs of a university-affiliated private teaching hospital. PATIENTS: Using data obtained from a retrospective analysis of 10 medical patients > or =70 years old who had failed weaning, 49 additional medical patients older than 70 years were studied prospectively. INTERVENTIONS: Standard weaning parameters were determined using a hand-held spirometer. Respiratory rate (f, breaths/min) and tidal volume (VT, liters) were measured at the beginning of a spontaneous breathing trial and hourly thereafter for up to 5 h using the same hand-held spirometer. MEASUREMENTS AND RESULTS: Retrospective analysis showed that the published threshold value for f/VT (< or =105) had poor predictability for weaning success when measured at the beginning of the weaning trial. In the 9 of 10 patients who failed to wean in the retrospective review, the f/VT increased to > 130 as the trial progressed over 2 to 3 h. Using an f/VT < or =130 as the threshold value for prospectively predicting successful weaning, the diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value increased from 84%, 92%, 57%, 87%, and 67%, respectively, when measured at the beginning of the weaning trial to 92%, 93%, 89%, 97%, and 80%, respectively, when measured 3 h later. The area under the receiver operating characteristic curve for f/VT also improved from 0.81 to 0.93. CONCLUSIONS: Serial measurements of the rapid-shallow-breathing index in medical elderly patients during a period of spontaneous breathing can accurately predict the ability to be successfully weaned from mechanical ventilator support.

Near-drowning: epidemiology, pathophysiology, and initial treatment.

Drowning is a major cause of accidental deaths, especially in children. The most serious pathophysiologic consequence of near-drowning is hypoxemia, which usually is due to aspiration-induced noncardiogenic edema. Therefore, initial resuscitative efforts need to be directed at establishing adequate oxygenation and ventilation, followed by rewarming and fluid administration. Although completely asymptomatic patients with normal vital signs, oxygenation and chest radiographs require only 4 to 6 hours of observation, many near-drowning victims will require at least 24 hours of observation. Despite these measures, approximately 25% of victims presenting to the Emergency Department will die and another 6% will develop neurological sequelae. Therefore, it is vital that better efforts be made by the community in promoting and instituting water safety programs.

[Incidence of insulin resistance in peripheral arterial occlusive disease patients. Pilot study in a general medicine practice]. / Häufigkeit der Insulinresistenz bei pAVK-Patienten. Pilotstudie in einer allgemeinmedizinischen Praxis.

UNLABELLED: Few data are available on the correlation between peripheral occlusive arterial disease and metabolic syndrome. The present pilot study therefore investigated patients with and without PAOD and compared their vascular risk pattern with that of healthy controls. METHOD: With the aid of Doppler US measurements of blood pressure differences (tibiobrachial Doppler Index [DI], 59 patients were divided up into three groups: "healthy" (DI > 0.8 to < 1.0), "suffering from PAOD" (DI < 0.8) and "endangered" (DI > 0.8 to < 1.0). In each patient an oral glucose test (100 g) was done and insulin levels measured; in addition, the lipid fractions and fibrinogen were determined in the fasting patient. RESULTS: The groups, matched for age and weight, showed typical differences between patients with PAOD and healthy controls: lowered HDL cholesterol, elevated systolic blood pressure, triglycerides, total and LDL cholesterol and insulin. In addition, disorders of the glucose tolerance test were also more common. This shows that the patients with vascular disease have the typical risk factor pattern for metabolic syndrome as compared with controls in which point they are similar to patients with CAD. CONCLUSION: In patients with PAD, intensive non-medical therapy, such as weight reduction and physical exercise are likely to reduce the vascular risk-as has been shown for CAD patients.

High accuracy pre-formed gradient discontinuous flow titrimetry.

A variant of Discontinuous Flow Analysis (DFA) titrimetry is described in which a pre-formed gradient is established between two titrant concentrations with the analyte aspirated at a constant rate into the gradient. The gradient encompasses a narrow range of analyte concentration (10% variation in this instance), and provides a high encoder pulse resolution. A simple acid-base titration model using photometric endpoint detection achieved comparable accuracy to conventional batch titrimetry (approximately 0.1% relative), with excellent calibration linearity (r(2) = 0.9997, standard error of estimation approximately 0.05% relative over six standards). Titrations were performed at the rate of one every 25 sec; with 0.8 ml of analyte and 0.85 ml of titrants consumed. The method is fully automatic.

Respiratory failure in the elderly.

Elderly patients are predisposed to respiratory failure because of physiological changes that occur with the aging process. These changes result in a loss of pulmonocardiac reserve and the relatively frequent need for mechanical ventilatory support. The management and weaning of elderly patients from mechanical ventilatory support is different from strategies used for younger patients. By focusing on the physiological changes that occur in the elderly, this article explains why the elderly experience more complications and higher mortality than younger patients with respiratory failure. It also suggests management strategies that incorporate newer insights into ventilatory and respiratory muscle failure.

Noninvasive measurement of central venous pressure by neck inductive plethysmography.

Bedside estimation of the height at which the internal jugular veins collapse, referenced to a standard hemodynamic location, theoretically reflects central venous pressure. This method has never been demonstrated as accurate when compared to invasive CVP measurements because of the great clinical skills and time required to visually identify the internal jugular venous waveform. Since the principles of the bedside method are sound, we utilized them in conjunction with the neck inductive plethysmograph, a device which has the capability of recording internal jugular venous and carotid arterial waveforms. The respiratory distortion of these vascular waveforms was eliminated by employing a digital bandpass filter, making it easy to identify the venous and arterial waveforms on the videoscreen of a personal computer. The upper torso was positioned while observing the videoscreen until the vascular waveform was seen as a mixed arteriovenous waveform, signifying intermittent internal jugular venous collapse. The height of the internal jugular vein above the phlebostatic axis was obtained by external measurement and recorded as CVPni in cm H2O. In 43 patients, 86 percent of CVPni (NIP) values fell within 20 percent CVPi (invasive catheter measurements) over a range of CVP from 0 to 19 cm H2O. In an additional seven patients, CVPi was greater than the height that the upper torso could be elevated and an arterial waveform could not be obtained. Here, CVPni was recorded as the value at least exceeding the value measured. In two other patients, obstruction of an internal jugular vein gave spuriously low values of CVPni. Our study indicates that this new neck inductive plethysmographic method is accurate compared to invasive catheter measurements of CVP and should serve as a safe, noninvasive alternative in situations where such measurements are required.

Thoracocardiography. Part 2: Noninvasive measurement of changes in stroke volume; comparisons to impedance cardiograph.

The thoracocardiograph (TCG) displays cardiac oscillations transmitted to the external surface of the thorax through inductive plethysmographic transducers placed transversely around the thorax near or about the xiphoid process. Such signals, with the appearance of ventricular volume curves, were used to compute changes of stroke volume (SV) and cardiac output (CO) in normal subjects. Their values were compared with changes of SV and CO measured with the impedance cardiograph (IC). Increases of SV and CO were produced with subcutaneous terbutaline and there was excellent agreement between TCG and IC values, best from TCG transducers placed at the xiphoid process and 3 cm caudal to it, although TCG locations 6 cm caudad and 3 cm cephalad to the xiphoid were also satisfactory. Since the site 3 cm caudad to the xiphoid process is known to anatomically transect solely a segment of the left ventricle, it was designated the TCG-Reference location. Both TCG and IC derived SV were not altered during postural shifts about a horizontal axis. Neither TCG nor IC showed the expected large decreases of SV from supine posture to head-up tilt. With baseline TCG and IC measurements in 60 degrees head-up tilt. MAST suit application increased CO measured with TCG but not with IC. Neither TCG nor IC revealed alteration of CO with nasal CPAP up to 10 cm H2O despite a rise in functional residual capacity (FRC) level of 870 ml. This investigation indicates that TCG has promise as a near continuous, noninvasive monitor of SV and CO in normal subjects if postural axis is fixed and does not require highly trained personnel or labor-intensiveness for its operation.

Thoracocardiography. Part 1: Noninvasive measurement of changes in stroke volume comparisons to thermodilution.

The thoracocardiograph (TCG) is a new noninvasive monitoring device that measures cardiac oscillations transmitted to the external surface of the thorax. It consists of 2.5 cm in height, elastic inductive plethysmographic transducers placed transversely in the proximity of the xiphoid process to provide changes in cross-sectional area on a transverse plane across the minor ventricular axis. Cardiac oscillations synchronous with each heart beat are extracted from the respiratory signal during breathing with an ensemble-averaging technique using the electrocardiograph as a trigger pulse. The average cardiac waveform at locations near the xiphoid process in normal humans has the appearance of a ventricular volume curve. The latter is also found in the majority of patients with heart disease although in some, outward (dyskinetic) rather than inward motion during systole occurs at one or more locations of the TCG transducers. As in echocardiography, such findings are consistent with ischemic or scarred myocardium invalidating computation of changes in stroke volume from such sites. In anesthetized dogs and critically ill patients with normal ventricular wall motion, changes in TCG derived ventricular volume waveform amplitudes agreed well with changes of thermodilution estimates of stroke volume during atrial pacing and fluid loading in the dogs on the one hand and with application of extrinsic positive end-expiratory pressure (PEEP) in patients on the other hand. Thoracocardiography has the potential for noninvasive, continuous monitoring of stroke volume and cardiac output as well as for detection of ischemic or scarred myocardium.

Disseminated strongyloidiasis in AIDS and non-AIDS immunocompromised hosts: diagnosis by sputum and bronchoalveolar lavage.

In conclusion, disseminated strongyloidiasis is a fatal disease that commonly affects the lungs. The disease should be suspected in an immunocompromised host who came from an area endemic for S stercoralis even years before the onset of symptoms or in patients with unexplained gram-negative bacteremia or meningitis. Treatment should be started promptly and should be maintained for a long time.

One year's experience with a noninvasively monitored intermediate care unit for pulmonary patients.

Many studies have shown that selected cardiac patients can be safely and economically cared for in intermediate care units rather than intensive care units. However, there are only limited data concerning intermediate care units for pulmonary patients. We prospectively followed up all Medicare patients from May 5, 1987, through May 4, 1988, who were admitted to a pulmonary noninvasive monitoring unit. Ninety-four patients were admitted 104 times; 33 required mechanical ventilatory support for an average of 26 days. The overall cost savings were greater than $173,000, while high-quality medical care was maintained. We conclude that a noninvasive monitoring unit can be effectively used as an alternative to the intensive care unit for selected pulmonary patients.

Diaphragmatic flutter resulting in failure to wean from mechanical ventilator support after coronary artery bypass surgery.

Diaphragmatic dysfunction, most commonly elevation of the left hemidiaphragm and/or phrenic nerve paralysis, are well-known complications of coronary artery bypass grafting (CABG). Diaphragmatic flutter (DF) is an easily overlooked breathing pattern characterized by rapid (greater than 40 times/min) involuntary contractions of the diaphragm, at times superimposed on a more normal breathing pattern (dirhythmic breathing). Using respiratory inductive plethysmography, we were able to record this unusual ventilatory pattern in four patients after CABG. All procedures were performed via median sternotomy with topical hypothermia. Sternal complications were present in three cases (instability, dehiscence, infection). DF could not be suppressed by mechanical hyperventilation or patient volition. Weaning was unsuccessful until after DF abated. Diaphragmatic flutter may occur after CABG and should be considered as a cause of failure to wean from mechanical ventilator support in this setting.

Pleural pressure changes in dogs measured from suprasternal fossa movements.

Movements of the suprasternal fossa during spontaneous breathing monitored with the surface inductive plethysmograph (SIP) have been shown to reflect changes of intrapleural pressure in conscious humans. Calibration of this device in anesthetized intubated dogs was accomplished by adjusting the electrical gain of its analog waveform to be equivalent to changes of airway pressure during inspiratory efforts against an occluded airway. This procedure, denoted the occlusion test, was also used to identify the site of esophageal balloon catheter placement for its recording of intrapleural pressure deflections. The validity of SIP-derived estimates of inspiratory and expiratory pulmonary resistances and lung compliance was established by finding close agreement with measurements obtained with intraesophageal pressure changes during 1) unimpeded spontaneous breathing, 2) inspiratory resistive loading, 3) bronchoprovocation with aerosolized carbachol, 4) mechanical ventilatory modalities, and 5) induced pulmonary edema. Therefore, movements of the suprasternal fossa with respiration can be reliably transformed into quantitative or semiquantitative changes of intrapleural pressure in anesthetized intubated dogs during major alterations of pulmonary mechanics.

Cheyne-Stokes respiration in patients recovering from acute cardiogenic pulmonary edema.

Cheyne-Stokes respiration is characterized by crescendo-decrescendo fluctuations in tidal volume and respiratory rate interrupted by central apneas. It has long been associated with cardiac disease and has often been cited as a poor prognostic indicator, yet the incidence and immediate significance of CSR in the setting of acute cardiogenic PE is not well defined. Therefore, we studied 95 patients who required MVS because of PE. Breathing patterns were monitored by continuous respiratory inductive plethysmography for a minimum of 12 hours of spontaneous respiration after recovery from PE; CSR was noted in 42 patients (44 percent). There were no significant differences between patients with PE and CSR and those with only PE in regard to LVEF (mean +/- SD, 36 +/- 18 percent vs 33 +/- 16 percent; p = 0.55), reinstitution of MVS within 48 hours (4.8 percent vs 17.0 percent; p = 0.065), or in-hospital mortality (16.7 percent vs 26.4 percent; p = 0.255). We conclude that CSR is a relatively common breathing pattern in patients who required MVS because of cardiogenic PE and does not portend a poor immediate prognosis in this population.

Right upper lobectomy twenty years after left pneumonectomy. Preoperative evaluation and follow-up.

Quantitative perfusion lung scanning coupled with spirometry and balloon occlusion of the pulmonary artery supplying the lung to be resected have been used to predict the potential operability of patients being considered for pneumonectomy. These techniques were adapted for the lobar level prior to performing a right upper lobectomy in a 59-year-old man who had undergone a left pneumonectomy 20 years previously. This case demonstrates how physiologic reserve can be predicted in patients who require sequential pulmonary resection.

End-tidal carbon dioxide in critically ill patients during changes in mechanical ventilation.

Values of end-tidal CO2 (PETCO2) approximate PaCO2 in spontaneous breathing normal subjects and in stable patients receiving mechanical ventilatory support (MVS). Because marked inequality of ventilation/perfusion ratios in critically ill patients might affect this correlation, we assessed changes of PETCO2 in predicting changes in PaCO2 (delta PaCO2) and changes in minute ventilation (delta Ve) in this patient population. Twenty consecutive intubated patients 38 to 89 yr of age (mean, 70 yr) with respiratory failure while receiving MVS with indwelling arterial lines were studied. Settings on the mechanical ventilator were varied for frequency and tidal volume, and after a minimum of 5 to 10 min equilibration, PaCO2 and PETCO2 were measured. Vt and Ve were recorded from the digital indicator of the pneumotachygraph within the mechanical ventilator and corrected for compression volume in the respirator circuit. A total of 116 simultaneous measurements were performed. PETCO2 correlated well with PaCO2 (r = 0.78, p less than 0.001). The 95% confidence interval for the mean difference in PaCO2-PETCO2 was 4.0 +/- 0.97 mm Hg. However, delta PETCO2 (measured from baseline) did not correlate as well with delta PaCO2 (r = 0.58, p = less than 0.001). In four patients, the trend in their PETCO2 during changes in mechanical ventilation were in the opposite direction from the trend in their PaCO2. Thus, many critically ill patients, who cannto be preidentified, have an inconstant PaCO2-PETCO2 gradient with changes of ventilation. Utilization of PETCO2 as a noninvasive monitoring substitute for trends in PaCO2 in critically ill patients may be misleading despite establishing an initial PaCO2-PETCO2 relationship.

Oxygen desaturation and changes in breathing pattern in patients undergoing colonoscopy and gastroscopy.

The respiratory effect of diagnostic colonoscopy and upper endoscopy were studied in 32 elderly patients. Twenty-two underwent colonoscopy and 10 upper endoscopy. In the group undergoing upper endoscopy, 4 of 10 patients experienced a decrease in oxygen desaturation greater than or equal to 4% during the medication period; an additional 2 patients desaturated during the procedure. In the group undergoing colonoscopy, 12 of 22 patients experienced oxygen desaturation during the medication period; 3 other patients desaturated during the procedure. Mean SaO2 for each group was lowest (p less than 0.05) during the medication period. Central apneas occurred in 13 of the patients undergoing colonoscopy during the medication period; however, only 8 of these patients with apneas experienced desaturation greater than or equal to 4% and the periods of desaturation did not correlate with the periods of apneas. Oxygen desaturation greater than or equal to 4% occurs frequently during both upper endoscopy and colonoscopy in this elderly population. This is related to the effects of sedation; the procedure itself worsened the desaturation in only 16% of the patients. Furthermore, the desaturation did not correlate with changes in the breathing patterns of the patients. Low-flow oxygen and/or close monitoring of patients during and subsequent to administration of medication is advised.

New modes of palliative therapy for patients with lung cancer--a review.

Although our ability to cure nonsmall cell carcinoma of the lung has not changed appreciably over the past decade, newer modalities have provided improved palliative therapy. This article briefly reviews various forms of laser therapy and endobronchial irradiation (brachytherapy). The combination of these techniques appears to offer the promise of safely palliating patients who otherwise would rapidly succumb to local effects of their tumor.