High frequency chest compression (HFCC) offers a noninvasive therapeutic technique for a variety of thoracic region disorders. For more than 30 years, the HFCC focus has been on pulmonary disease. Significant pulmonary secretion enhancement and increased expectorated sputum output have been reported for cystic fibrosis (CF) patients with the application of HFCC therapy [1]. What follows describes certain capabilities of this well established pneumatically driven technique that is applicable to cardiovascular disease. HFCC can address a wide spectrum of health disorders, providing many cardiopulmonary benefits [2].HFCC uses a pneumatically driven pump (source) and an inflatable vest, with a unique pump valve design, that can produce various pressure waveform shapes (trapezoidal, triangular, or sinusoidal) at the pump and vest locations [1,2]. The energy associated with those waveforms is transferred to the thoracic region for therapeutic purposes, including CF.End of life for many CF patients can occur within a few months of having predicted forced expiratory volume in one second (FEV1) levels of 30–40%. However, some CF patients survive reasonably well on predicted FEV1 levels lower than 30%. And some of these patients survive for a number of years at predicted FEV1 levels close to 20%. A few of the low FEV1 survivors used a particular HFCC waveform (trapezoidal) for therapy. For them, it appears that the trapezoidal waveform provided a therapeutic impact that benefited other organs besides the lungs.Figure 1 shows that some CF patients with very low predicted FEV1 performance can live as long, or longer, than those with much higher FEV1 levels. Figure 1 indicates that long term survival for CF patients may not be just confined to sputum output and pulmonary function. The effect of HFCC on other organs may be providing substantial contributions to CF patient longevity.To evaluate the other organ effect, it was decided that the most appropriate other organ to test was the heart. The best HFCC waveform from the standpoint of its effects on other organs appeared to be the trapezoidal waveform. At higher HFCC frequencies (6–12 Hz), blood pressure reductions are typically less than 3.5% [3]. The objective was to determine if HFCC had more substantial effects on near term and long term blood pressure and heart rate at lower frequencies.For the other organ effect evaluation, an HFCC system was chosen that provided the most abrupt trapezoidal pressure waveform. Data from seven individuals were analyzed for the initial study. The HFCC output was adjusted for four of the study subjects to frequencies close to the heart rate. Near term–long term effects on blood pressure were recorded. Statistical techniques applied to blood pressure data are questionable unless initial continuous monitoring of blood pressure is done over long periods of time (months). One subject had a record of daily blood pressure levels for the previous 19 years, providing an excellent platform to analyze blood pressure levels and changes that occurred with HFCC. Treatments were administered twice a week for one half hour each. Blood pressure, heart rate, saturated oxygen, and electrocardiogram data were continuously monitored and recorded.The HFCC trapezoidal waveform provided the most significant impact on blood pressure and heart rate regulation. The asymmetric sine wave and triangle waveforms appeared to have some effect, with the sine wave HFCC system producing the least effect. The vest designs associated with the asymmetric sine wave and sine wave systems could be part of the reason for their less substantial effects.The heart requires approximately 13 W of the body's available power from various metabolic processes. Approximately, 1.3 W of the available power is converted into electrical and mechanical power to promote heart contractions and pump blood. Simulations and power calculations [2] indicate that approximately 3–5% (or 0.12–0.3 W) of the average source-vest chest HFCC power at frequencies close to 2 Hz may be interacting with the heart region. As indicated by the results reported in Ref. [2], this amount of power interacting with the heart is enough to produce average systolic blood pressure reductions of approximately 12 mm Hg and average peak-to-peak systolic blood pressure variation reductions of 17 mmHg for subjects with hypertension. The effects on diastolic blood pressure appear to be delayed by approximately 4 days with a subsequent decrease in average diastolic blood pressure of approximately 5 mmHg over a 10 day period [2]. A 47 day plot of blood pressure reduction with the application of HFCC at lower frequencies can be seen in Fig. 3 of Ref. [2]. The results are summarized in the Table 1.In addition, the effect of the lower frequency HFCC signal on heart rate can be significant if the heart rate is too high or too low. The chest compression waveform at the lower frequencies tends to abruptly push the heart rate to a healthier level (50–60 bpm) for heart rates that are too high (tachycardia) or too low (bradycardia). The cardiovascular system seems to be responding to various signals like a phase lock loop tracking receiver. Portions of the cardiovascular system have been modeled as a phase lock loop, with the heart serving as a variable frequency oscillator [2].Phase lock can occur when there are significant differences in level between the phase lock loop primary signal power and the locking signal. The applied HFCC waveform power in the region of the heart appears to be sufficient to promote a phase lock condition between the chest compression waveform and heart rate, resulting in an abrupt shift in heart rate (Fig. 2). As shown in Fig. 2, a heart rate that is too low will often abruptly increase to a higher level with the application of HFCC at the lower operating frequencies. For bradycardia and tachycardia, the heart rate appears to (1) abruptly shift to a frequency that is the sum of the HFCC frequency and the breathing rate, (2) shift to a frequency that is the difference between the HFCC frequency and breathing rate, or (3) shift to a difference frequency involving the fundamental and harmonics of the heart rate and HFCC frequency [2]. These frequency change combinations are most likely due to the effect of the interconnections between the heart and its associated nervous system signals.At chest compression frequencies close to 2 Hz, approximately 3–5% of the average source-vest chest compression power interacts with the heart region [2]. This relatively small amount of power (approximately 0.12–0.3 W) appears to be enough to produce significant improvements in average blood pressure, daily blood pressure variations, and heart rate [2]. It appears that a small amount of pneumatically driven chest compression power can provide significant therapeutic benefits for cardiovascular health with respect to hypertension and heart rate regulation. There is another strong message in the data. Figure 1 and Table 1 show the result of what improvements in therapeutic technique can do for patients with pulmonary disease, especially for those who have seriously damaged pulmonary systems. With the trapezoidal HFCC waveform being able to provide beneficial other organ effects, the cumulative impact of other organ benefits can help to mitigate long term lung deterioration. This kind of synergy can help to improve survivability percentages for many patients with CF and other chronic obstructive pulmonary disease health problems, even for those with limited pulmonary function capabilities.The authors wish to thank Dr. Warren J. Warwick for his encouragement and guidance in the course of this study.